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Applied Surface Science (v.252, #1)

13th Applied Surface Analysis Workshop (AOFA 13) by Klaus Wetzig (Guest Editor) (pp. 1-2).

Depth profile and interface analysis in the nm-range by S. Oswald; R. Reiche; M. Zier; S. Baunack; K. Wetzig (pp. 3-10).

In modern technology, thin films are shrinking more and more to a thickness of few nanometers. Analytical investigations of such thin films using the traditional sputter depth profiling, sputtering in combination with surface-analytical techniques, have limitations due to physical effects especially for very thin films. These limitations are pointed out and some alternatives are discussed. Non-destructive analysis with angle-resolved X-ray photoelectron spectroscopy is demonstrated to be a useful method for such investigations. Both qualitative and quantitative results can be obtained even for complex layer structures. Nevertheless, there are also limitations of this method and some alternatives or complementary methods are considered.

Keywords: PACS; 82.80−Pv; 68.55−a; 68.35−pElectron spectroscopy; Depth profiling; Angle-dependent analysis; Thin films; Surface morphology; Barrier layers

Phase analysis of TaN/Ta barrier layers in sub-micrometer trench structures for Cu interconnects by M. Traving; I. Zienert; E. Zschech; G. Schindler; W. Steinh�gl; M. Engelhardt (pp. 11-17).

The resistance behavior of TaN/Ta diffusion barrier bilayers has been investigated. The dependence of the Ta-phase on the TaN layer thickness was examined by means of X-ray micro-diffraction and resistivity measurements. Furthermore, the influence of the geometry of a damascene trench structure on the Ta-phase of the deposited TaN/Ta barrier bilayers has been studied and compared to the results obtained with blanket wafers. The influence of the Ta-phase on the via resistance of Cu interconnects is discussed.

Keywords: PACS; 61.10.Nz; 81.05.Bx; 81.15.CdDiffusion barrier; Damascene trench; TaN; Ta; Ta-phase; X-ray diffraction; Resistivity

New physical techniques for IC functional analysis of on-chip devices and interconnects by Christian Boit (pp. 18-23).

Localization of functional fails in ICs makes use of physical interactions that the devices produce under electrical operation. The focus is on electroluminescence (keyword: photon emission) and signal responses to stimulation by scanned beams of laser light or particles. In modern chip technologies access of this information is only available through chip backside. This paradigm shift requires a full revision of chip analysis techniques and processes. This has also been a kick-off of a rush in development of new methodologies. Here, an overview is given which parameters are crucial for successful analysis techniques of the future and how photon emission, laser based techniques and new preparation techniques based on focused ion beam (FIB) open the path into this direction.

Keywords: PACS; 85.40.Qx; 79.60; 52.50.JmFailure analysis through chip backside; Photon emission; PICA; Thermal laser stimulation (TLS); Soft defect localization (SDL); OBIRCH; TIVA; LADA; Circuit edit; Focused ion beam (FIB)

Visible-light attachment of SiC linked functionalized organic monolayers on silicon surfaces by Louis C.P.M. de Smet; Aliaksei V. Pukin; Qiao-Yu Sun; Brian J. Eves; Gregory P. Lopinski; Gerben M. Visser; Han Zuilhof; Ernst J.R. Sudh�lter (pp. 24-30).

Organic monolayers on hydrogen-terminated silicon surfaces were prepared under extremely mild conditions using visible light and analyzed by a variety of surface-sensitive techniques: (angle-resolved) X-ray photoelectron spectroscopy (ARXPS), scanning tunneling microscopy (STM), high-resolution electron energy loss spectroscopy (HREELS), and attenuated total reflection infrared spectroscopy (ATR-IR). Detailed XPS and STM analysis of non-functionalized monolayers displays detailed mechanistic and structural information. Additionally, we present the first attachment of a disaccharide to the silicon surface, and a characterization thereof by ATR-IR and HREELS.

Keywords: PACS; 68.65.+g; 87.15.By; 61.16Visible light; Hydrosilylation; Organic monolayers; Receptors; Biosensors

Elementary processes at semiconductor/electrolyte interfaces: perspectives and limits of electron spectroscopy by Th. Mayer; M. Lebedev; R. Hunger; W. Jaegermann (pp. 31-42).

Semiconductor device properties based on electrolyte contacts or modified by electrochemical reactions are dominated by the electronic structure of the interface. Electron spectroscopy as e.g. photoemission is the most appropriate surface science techniques to investigate elementary processes at semiconductor/electrolyte interfaces. For such investigations a specific experimental set-up (SoLiAS) has been built-up which allows performing model experiments as well as surface analysis after emersion under different experimental conditions. The experimental approach is presented by a number of experiments performed during the last years with GaAs as substrate material. Model experiments by adsorption and coadsorption of electrolyte species give information on fundamental aspects of semiconductor/electrolyte interactions. Emersion experiments give information on a final composition and the related electronic structure of electrodes after electrochemical reactions. The use of frozen electrolytes will help to bridge the gap between these two approaches. With the combination of the experimental procedures one may expect a detailed analysis of electrolyte (modified) interfaces covering chemical composition, electronic structure of surfaces/interfaces as well as surface/interface potentials.

Keywords: PACS; 68.45.Da; 73.20.Dx; 82.80.PvSolid–liquid interface; Emersion; Adsorption; Photoelectron spectroscopy; GaAs

Morphological and elemental characterisation with the high-energy ion-nanoprobe LIPSION by T. Butz; Ch. Meinecke; M. Morawski; T. Reinert; M. Schwertner; D. Spemann; J. Vogt (pp. 43-48).

This contribution deals with the morphological and elemental characterisation with high-energy (MeV) focused ion beams (in particular protons) with special emphasis on high spatial resolution in the sub-micrometer regime and very low minimum detection limits (sub-ppm) in trace element analysis. The most important methods like particle induced X-ray emission (PIXE), Rutherford backscattering spectrometry (RBS), as well as scanning transmission ion microscopy (STIM) and STIM-tomography will be illustrated by examples from material and life sciences.

Keywords: PACS; 07.81.+a; 78.70.En; 82.80.Yc; 68.55.−aIon probe; Particle induced X-ray emission (PIXE); Rutherford backscattering spectrometry (RBS); Thin films

Comparison of reference-free X-ray fluorescence analysis and X-ray reflectometry for thickness determination in the nanometer range by Michael Kolbe; Burkhard Beckhoff; Michael Krumrey; Gerhard Ulm (pp. 49-52).

X-ray reflectometry is the method of choice to determine the thickness of nanolayered systems with small uncertainties. In view of known limitations of this method for extremely thin or laterally inhomogeneous layers we compared X-ray reflectometry with fundamental parameter based X-ray fluorescence analysis using synchrotron radiation in the radiometry laboratory of the PTB. The results of both methods for a set of sample systems with transition metal layers of various thicknesses deposited on silicon wafers were compared and showed a good agreement within their respective uncertainties. For the investigation of layered systems both methods are very appropriate and, in addition, can give complementary information about the layers. Thus, the density is determined by X-ray reflectometry, and X-ray fluorescence analysis gives information about trace elements within the layers and the layer homogeneity.

Keywords: PACS; 78.70.E; 61.10.K; 06.20.JX-ray fluorescence; X-ray reflectometry; Fundamental constants

Determination of layer thickness with μXRF by Carla Vogt; Rainer Dargel (pp. 53-56).

The significance of thin films in modern high tech applications requires fast and nondestructive analysis. A method to determine the thickness of single layers with μXRF via a calibration procedure is described. The influences of surface roughness and the angle of the incident beam on the intensity of the fluorescence radiation are discussed.

Keywords: PACS; 68.55.−a; 61.10.YhThin films; MicroXRF; Layer thickness; TiN

Laboratory LPP EUV reflectometer working with non-polarized radiation by Ludwig van Loyen; Thomas B�ttger; Stefan Sch�dlich; Stefan Braun; Thomas Foltyn; Andreas Leson; Frank Scholze; Stephan M�llender (pp. 57-60).

A laboratory extreme ultraviolet reflectometer (EUVR) for the wavelength range from 10 to 16nm was built at IWS Dresden using a gold target laser pulse plasma (Au-LPP) source. The peak reflectance and the center wavelength are reproduced in relative standard deviation of 0.2 and 0.02%, respectively. In contrast to measurements using linearly polarized s-adjusted synchrotron radiation at PTB, measurements with non-polarized radiation at the EUVR yield systematically lower values for the reflectance due to the smaller reflectance of the p-component at higher angles of incidence.

Keywords: Extreme ultraviolet; Metrology; Lithography; At-wavelength characterization; ReflectometryPACS; 6.20; 42.82.C; 7.60.H

Quantitative XPS imaging—new possibilities with the delay-line detector by U. Vohrer; C. Blomfield; S. Page; A. Roberts (pp. 61-65).

X-ray photoelectron spectroscopy (XPS, ESCA) is an ideal tool for identifying differences in surface chemistry. In the past, it has lacked the spatial resolution as well as the performance of elemental or even chemical state imaging, to be of significant use in detecting most microscopic surface phenomena. The recent development of improved micro- or small spot-XPS systems with near-micron spatial resolution as well as outstanding chemical state image performance has opened up a significant opportunity to undertake more detailed studies of micro-structured or micro-patterned surfaces or technical samples with locally distributed impurities. The introduction of a new detector type, the delay-line detector (DLD), to XPS-equipments allows for the first time the acquisition of quantifiable XPS images. This study is intended primarily to explore the capabilities of quantitative ESCA-imaging with respect to the possibilities and limits.

Keywords: PACS; 82.80.Pv; 61.16.MsXPS; ESCA; Imaging; Quantification; DLD

A combined SNMS and EFTEM/EELS study on focused ion beam prepared vanadium nitride thin films by Gerald Kothleitner; M. Rogers; A. Berendes; W. Bock; B.O. Kolbesen (pp. 66-76).

We investigated the diffusion profiles and core-loss fine-structures (ELNES) of thin vanadium nitride films by electron energy-loss spectroscopy (EELS) and energy filtering transmission electron microscopy (EFTEM). The nitride layers have been produced by rapid thermal processing in a NH₃ or N₂ atmosphere and have then been cross-sectioned with a focused ion beam instrument (FIB) under mild milling conditions to maintain crystallography. For the high-resolution electron energy-loss spectroscopy studies (HREELS), a recently developed TEM gun monochromator, implemented into a 200kV field emission gun column was used in combination with a new post-column spectrometer. It was found that, dependent on substrate and atmosphere, layers with different vanadium and nitrogen content were formed, showing distinct differences in their ELNES. With an energy resolution at the 0.2eV level and a TEM beam spot size of approximately 2nm these layers could be unambiguously identified when compared to theoretical ELNES simulations from the literature.

Keywords: PACS; 61.16.Bg; 82.80.Pv; 68.55.NqVanadium nitride films; Rapid thermal processing (RTP); Focused ion beam preparation (FIB); TEM gun monochromator; STEM/EELS; Secondary neutral mass spectrometry (SNMS)

Chemisorption at interfaces between organic semiconductors and metals: role of the electron affinity by M. Knupfer; T. Schwieger (pp. 77-80).

Chemisorption is a well-known phenomenon for many interfaces between organic semiconductors and metals. It is shown that many published data indicate that the occurrence of chemisorption can be rationalized upon the consideration of the metal work function versus the electron affinity of the organic semiconductor.

Keywords: PACS; 73.61.Ph; 73.40.Ns; 73.20.−rMetal/organic interfaces; Chemisorption; Photoemission spectroscopy

IR and SFM study of PTCDA thin films on different substrates by Steffen Berger; Kathrin Heimer; H.G. Mack; Christiane Ziegler (pp. 81-84).

FT-IR spectroscopy and SFM were used to investigate the growth of thin films of the organic semiconductor 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) deposited by vacuum sublimation onto various substrates, i.e. Ag(111) layers on mica, KBr(100), mica, oxidized Si, and TiO₂ nanoparticles on Si. Layer thicknesses of PTCDA varied from 10 to 1500nm.The anhydride vibrations of PTCDA differ for the used substrates, which can be connected to the orientation of the molecules relative to the substrate surface and the film morphology as detected in the SFM pictures.

Keywords: PACS; 60.63.50.+xOrganic semiconductor; Structure; DFT calculation; Orientation

Photoelectron spectroscopy of nanocrystalline anatase TiO₂ films by Adam Orendorz; Jens W�sten; Christiane Ziegler; Hubert Gnaser (pp. 85-88).

Nanocrystalline TiO₂ (anatase) films were prepared using either colloidal suspensions or a sol–gel route. The electronic structure of these films was analyzed using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Apart from pristine films, films containing defects introduced by annealing under ultra-high vacuum conditions or by ion bombardment were investigated. Generally, annealing in the temperature range up to 720K results in no significant changes in the XPS and UPS spectra as compared to the pristine state, indicating that the amount of defect formation is too low to be observable by these techniques. On the other hand, ion irradiation causes the appearance of distinct defect states; these could be identified in agreement with previous data from photoemission studies on rutile and anatase single crystals. From UPS, a valence-band width of ∼4.6eV was determined for the nanocrystalline anatase films.

Keywords: PACS; 61.46.+w; 68.37.−d; 73.63.Bd; 81.07.BcTitanium dioxide; Nanocrystalline films; Photoelectron spectroscopy

Characterization of thin Ta–Si–N_x layers of different nitrogen content using XPS, UPS and STM by W. Zahn; D. Hildebrand; S. Menzel; S. Oswald; H. Heuer (pp. 89-93).

Reactively sputtered Ta–Si–N_x barrier systems of different nitrogen content on copper were investigated by photoelectron spectroscopy (XPS, UPS) and scanning tunnelling microscopy (STM). The measured photoelectron spectra (excitation He–I) showed a clear dependence of the electron state density near the Fermi edge on the content of nitrogen. These results correlate with the I(U) characteristics of the STM measurements and the electrical conductivity of these layers.

Keywords: PACS; 82.80.Pv; 61.16.Ch; 66.30.NyPhotoelectron spectroscopy; Scanning tunnelling microscopy; Barrier systems; Tantalum-based layers

Nm-scale resolution studies of the bond interface between ultrasonically welded Al-alloys by an analytical TEM: a path to comprehend bonding phenomena? by A. Brodyanski; C. Born; M. Kopnarski (pp. 94-97).

The analysis of the ultrasonically welded zone between aluminum alloys is taken as an example of the possibilities of analytical TEM to gain an insight into the phenomena occurred at the inner boundary surfaces of contacting metals during the ultrasonic welding. It is shown that combined TEM studies (imaging, diffraction, chemical analysis) of the welded seam allow to thoroughly characterize such a “buried�? layer as the ultrasonic welded zone and to reconstruct, thereby, the physical and chemical processes responsible for its formation.

Keywords: PACS; 61.16.Bg; 81.20.VjTEM; Ultrasonic welding; Bonding zone; Al-alloys

On the cleaning of monocrystalline metallic samples from impurities by W. Arabczyk; U. Narkiewicz (pp. 98-103).

The problem of sample cleaning is essential for all the scientists using ultra-high vacuum (UHV) techniques. The paper explores the issue of how the real structure of the monocrystalline sample affects its cleaning procedure. The mosaic structure of a monocrystalline sample should be taken into account in the interpretation of segregation and adsorption phenomena studies carried out under UHV conditions. Some examples of the cleaning of an Fe(111) sample from sulphur and carbon impurities are presented in the paper. Cleaning may result in obtaining two different states: clean surface and clean defects or clean surface but filled defects. According to these studies, the number of adsorption sites in the defects equals approximately 50% of the number of adsorption sites on the surface.

Keywords: PACS; 81.65.Cf; 64.75.+gSurface cleaning; Surface contamination; Segregation; Defects

Post deposition purification of PTCDA thin films by J. W�sten; Th. Ertl; S. Lach; Ch. Ziegler (pp. 104-107).

The decomposition of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecules during evaporation of unpurified raw material in ultra high vacuum was studied. The fragments were identified by mass spectrometry and the influence of these fragments and further contaminations of the raw material on the electronic structure of PTCDA thin films was measured by photoemission spectroscopy. Annealing of contaminated PTCDA films was tested as cheap and easy to perform method for (partial) post deposition purification of the contaminated films.

Keywords: PACS; 73.20.−r; 71.20.RvPTCDA; Purification; Photoemission; Mass spectrometry

Corrosion of aluminium components studied with MIES, UPS and XPS by Martin Frerichs; Florian Voigts; Sven Hollunder; Rainer Masendorf; Alfons Esderts; Wolfgang Maus-Friedrichs (pp. 108-112).

We use X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and metastable impact electron spectroscopy (MIES) to investigate the corrosion of aluminium components. Clean aluminium films were prepared under ultrahigh vacuum (UHV) conditions and exposed to water and NaCl. We attempt to provide a model for the mechanism of this interaction and its effects on the durability of the components.

Keywords: PACS; 81.65.MqAluminium; Corrosion; Ultraviolet photoelectron spectroscopy (UPS); Metastable impact electron spectrocopy (MIES)

Analytical methods for the characterisation of leaf surfaces: a contribution to understand the processes of biomineralization by Simone Hinke; G�nter Marx; R�diger Fehlhaber; Otto Wienhaus (pp. 113-116).

Biomineralization describes the pathway of nature to organize inorganic compounds and molecules for the creation of functional systems. This work is part of the DFG special program 1117 ‘Principles of Biomineralization’, which is a multidisciplinary work between scientists from several German universities and also from other European countries. One part is the study of the silicon accumulation in wheat ( Triticum aestivum L.) and orchard grass ( Dactylis glomerata L.). The plant samples grow under defined conditions in a pot trial. The plant habit and the quantity of biomineralized silica depend on the supplied additives, their availability for the plant and the growth conditions. Investigations were performed with SEM, conventional light microscopy, XRD as well as AAS for quantitative and qualitative elemental analysis.

Keywords: PACS; 87.64Biomineralization; Analytical methods; Silica cells; Trichome

Initial bioadhesion on surfaces in the oral cavity investigated by scanning force microscopy by N. Schwender; K. Huber; F. Al Marrawi; M. Hannig; Ch. Ziegler (pp. 117-122).

Scanning force microscopy (SFM) was used to measure the adhesion forces between BSA, a saliva protein, and two dental surfaces, natural enamel and a filling material (Dyract AP™). Measurements were taken in phosphate buffered aqueous solutions (PBS). Forces were resolved down to the piconewton regime. The dependency of the adhesion force on the interaction time, pH-value and substrate surface was monitored. In a further step, surface samples were fixed on an enamel brace and carried for a defined time in the oral cavity. The formed biofilm, called pellicle, shows a different morphology on the different substrates. This can be explained by the above-mentioned substrate dependence of the adhesion force.

Keywords: PACS; 87.64.DzScanning force microscopy; Salivary protein adsorption; Adhesion force

Low energy RBS and SIMS analysis of the SiGe quantum well by D. Krecar; M. Rosner; M. Draxler; P. Bauer; H. Hutter (pp. 123-126).

The Ge concentration in a MBE grown SiGe and the depth of the quantum well has been quantitatively analysed by means of low energy Rutherford backscattering (RBS) and secondary ion mass spectrometry (SIMS). The concentrations of Si and Ge were supposed to be constant, except for the quantum well, where the nominal germanium concentration was at 5%. Quantitative information was deduced out of raw data by comparison to SIMNRA simulated spectra. With the knowledge of the response function of the SIMS instrument (germanium delta (δ) layer) and using the model of forward convolution (point to point convolution) it is possible to determine the germanium concentration and the thickness of the analysed quantum well out of raw SIMS data.

Keywords: PACS; 68.49.Sf; 82.80.Ms; 82.80.Yc; 73.21.Fg; 68.18.−g; 68.47.PeSecondary ion mass spectrometry; SIMS; Low energy Rutherford backscattering; RBS; Quantum well; Ge-δ-layer

Quantitative element mapping of Mg alloys by laser ablation ICP-MS and EPMA by Christopher Latkoczy; Yves M�ller; Patrik Schmutz; Detlef G�nther (pp. 127-132).

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been successfully applied to quantitatively map the lateral elemental distribution of trace elements in multi-phase magnesium-based alloys. A lateral resolution of 32μm was achieved with limits of detection in the lower mgkg⁻¹ range for Ti, Cr, Mn, Fe, Co, Ni, and Cu in such materials. Quantification of elements by LA-ICP-MS was carried out using a sum normalization calibration procedure. Multi-element mappings of an area of 350μm×350μm were performed by LA-ICP-MS and results for the main elements Mg, Al, and Zn were compared to electron probe microanalysis (EPMA) measurements of the same sample area. The agreement for Mg was 2.2% between the two techniques. The influences of the laser parameters, like repetition rate and laser spot size were studied and the conditions were optimized for single spot analysis to achieve high lateral resolution capabilities.

Keywords: PACS; 82.80.-dICP-MS; EPMA; Mg alloys

Investigations of corrosion phenomena on gold coins with SIMS by K.E. Mayerhofer; K. Piplits; R. Traum; M. Griesser; H. Hutter (pp. 133-138).

In order to establish a new handling procedure for contaminated coins, the Coin Cabinet and the Conservation Science Department of the Kunsthistorisches Museum, Vienna, initiated a research project on corrosion effects of gold coins. By now, investigations on historic and contemporary coins included optical microscopy, scanning electron microscopy (SEM), Auger electron microscopy (AES), X-ray photoelectron microscopy (XPS), and electrochemical methods showing the distribution of pollutants.This work focuses on secondary ion mass spectrometry (SIMS) investigations merely showing the distribution of electronegative elements, such as sulfur, oxygen, and chlorine on the surface. Sulfur is highly suspected of causing the observed corrosion phenomena, and is indeed enriched near polluting splints. Since SIMS is a destructive method, the investigated samples are test coins with intentionally added impurities. These coins were manufactured in cooperation with the Austrian Mint. They were treated with potassium polysulfide (K₂S_x) for 8h gaining a rapid corrosion of the surface.SIMS mass spectra, depth profiles, and images were done (a) at non-polluted areas, (b) near polluted areas with slight coloring, and (c) directly at polluting stains showing enrichments of sulfur and chlorine. Due to the success of these investigations further studies on historic coins are intended.

Keywords: PACS; 82.80.MsNumismatic; Gold coin; Metallic inclusions; Corrosion; Brown spots; SIMS

Alkyl chain effects in thin films of substituted phthalocyanines studied using infrared spectroscopy by A. Haug; S. Harbeck; D. Dini; M. Hanack; M.J. Cook; H. Peisert; T. Chass� (pp. 139-142).

Thin films (2–50nm) of unsubstituted and 1,4-octa-alkyl substituted zinc phthalocyanines were investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, whereas the alkyl chains are C₄H₇, C₇H₁₃, C₁₀H₁₉. The absorption bands in the whole spectral range are discussed. We observe distinct differences in the spectra between the alkyl substituted Phthalocyanine (Pc) compounds. In contrast to PcZn and (but)₈PcZn, the spectra of (hep)₈PcZn and (dec)₈PcZn show two additional features in the spectral range between 3700 and 3000cm⁻¹, which are discussed in detail.

Keywords: PACS; 78.30.JwPhthalocyanine; Thin films; FTIR–ATR spectroscopy

Electronic properties of the organic semiconductor hetero-interface CuPc/C₆₀ by O.V. Molodtsova; T. Schwieger; M. Knupfer (pp. 143-147).

We present a study of the electronic properties of the interface between the well-established molecular organic semiconductor copper phthalocyanine (CuPc) and the fullerite C₆₀ using photoelectron spectroscopy and the Kelvin-probe (KP) method. Upon deposition of CuPc on C₆₀, we found interfacial shifts of the vacuum level indicating the formation of a dipole layer, while band bending is found to be negligible. The interface dipole of 0.5eV measured with KP is close to the difference between the work functions of bulk CuPc and C₆₀. No evidence for a chemical interaction at the interface is concluded from the absence of additional features in the core-level spectra at the earliest stages of deposition. The energy-level alignment diagram at the CuPc/C₆₀ interface is derived.

Keywords: PACS; 73.61.Ph; 73.40.Ns; 79.60.-iOrganic–organic interface; Kelvin-probe method; Photoelectron spectroscopy; Work function; Energy level alignment; Fullerite; Copper phthalocyanine

XPS investigation of the PTFE induced hydrophobic properties of electrodes for low temperature fuel cells by M. Schulze; C. Christenn (pp. 148-153).

In electrodes of low temperature fuel cells like polymer electrolyte membrane fuel cells (PEFC) or alkaline fuel cells (AFC) the reactants and the water must be transported. For this purpose the pore system in the electrodes needs a hydrophilic character for the transport of the water and a hydrophobic character for the transport of the gases. The degree of the hydrophobicity determines whether the pore system will be flooded by the reaction water. In the case of PEFC, this is also determined by the degree of the required humidification of the reaction gases. In AFC hydrophobicity determines the extension of the three-phase reaction zone. Caused by the strong influence of hydrophobicity on the transport processes, the electrochemical performance and the optimized operation conditions are also affected by hydrophobicity.Typically polytetrafluoro-ethylene (PTFE) is used to make the electrodes hydrophobic, because PTFE has a high chemical stability. Hydrophobicity depends on the concentration of PTFE on the electrode surface. The PTFE concentration, which is related to the hydrophobic character, can be determined by XPS. The changes in the PTFE content and structure of the electrode of a PEFC was investigated by cyclic voltammetry and XPS and correlated with the performance of the cell in long-term operation. With both methods an initial significant increase in free and electrochemically active surface platinum area is observed. This activation is associated with a degradation of the PTFE in the electrode which is responsible for the hydrophobic properties of the electrode. With further operation the performance of the cell decreases because the water management becomes more critical. Generally, it is shown that XPS can be used for the investigation of the hydrophobicity of electrodes prepared by various manufacturing techniques as well as of changes in their hydrophobicity induced by the electrochemical operation.

Keywords: PACS; 84.60.Dn; 82.80.PvFuel cells; Hydrophobic properties; XPS

Protein adsorption on solid–liquid interfaces monitored by laser-ellipsometry by R. Seitz; R. Brings; R. Geiger (pp. 154-157).

The adsorption of soluble proteins at solid–liquid interfaces plays a fundamental role in both, nature and industrial areas.The formation of organic molecular films below monolayer coverage can be resolved in real-time with ellipsometry, an optical technique based on the principle of change in state of polarization of light on reflection from an optically flat surface.In this communication studies of adsorption kinetics of the protein bovine serum albumin (BSA) on the substrates TiO₂, Au and SiO₂ are presented.The results show that the kinetics and degree of adsorption of BSA depend on the substrate material.

Keywords: PACS; 68.45.DProtein adsorption; Ellipsometry

Investigation of organic impurities adsorbed on and incorporated into electroplated copper layers by M. Stangl; V. Dittel; J. Acker; V. Hoffmann; W. Gruner; S. Strehle; K. Wetzig (pp. 158-161).

At room temperature electroplated copper layers exhibit changes in resistivity, residual stress, and microstructure. This process, known as self-annealing, is intimately linked to the release of organic impurities, which stem from the incorporation of organic additives into the Cu layer in the course of the electroplating process. The behavior of these impurities during self-annealing, represented by the carbon content, could be detected by analytical radio frequency glow discharge optical emission spectrometry (GD-OES) and carrier gas hot extraction (CGHE). The precondition of a quantitative determination is a surface cleaning procedure to remove adsorbed organics from the copper surface. It was observed that at first almost all impurities have to leave the Cu metallization before an accelerated abnormal grain growth can start. The small amount of remaining organic species after self-annealing could be quantified by both examination techniques, GD-OES and CGHE.

Keywords: PACS; 61.72.Ss; 66.30.Jt; 68.35.Dv; 81.15.Pq; 82.45.Vp; 85.40.LsElectroplating; Copper; Self-annealing; Additives; Surface contamination; GD-OES

Characterization of oxide layers on amorphous Zr-based alloys by Auger electron spectroscopy with sputter depth profiling by S. Baunack; U. Kamachi Mudali; A. Gebert (pp. 162-166).

Amorphous Zr–Cu–Ni–Al–[Ti, Nb] ribbons prepared by melt spinning under argon atmosphere were subjected to electrochemical investigations. Passive films developed at potentiostatic anodic polarization in sulphuric acid solution were investigated by Auger electron spectroscopy (AES) and sputter depth profiling.Changes in the shape of the Auger peaks have been analyzed by factor analysis of the spectra obtained during depth profiling. Pronounced changes in shape and position occur for the Zr, Al, and Ti Auger transitions, but not for Cu and Ni. At least three different peak shapes for O(KVV) were found and attributed to different oxygen binding states. The alloy composition has no significant effect on the thickness and composition of the oxide layer.In multi-element alloys preferential sputtering is a common phenomenon. In the steady state of sputtering, a significant depletion in Cu is found. At the oxide/metal interface, a distinct enrichment of copper is found for all alloys and treatments. The degree of this Cu enrichment depends on the pretreatment. It is higher for the electrochemically-passivated samples than for samples with oxide layers grown during melt spinning.

Keywords: PACS; 82.80.P; 82.80.F; 79.20.RAuger spectroscopy; Electrochemical analysis; Sputtering

Analysis of Mg–B compounds by means of Auger electron microprobe by S. Baunack; O. Perner; C. Fischer (pp. 167-171).

For the development of a low-cost MgB₂ superconductor the “powder-in-tube�? (PIT) technique is investigated. Mechanically alloyed MgB₂ powder provides a favorable microstructure and phase composition for the low temperature preparation of MgB₂ tapes with superconducting properties. The composition of sintered bulk samples and Fe-clad MgB₂ tapes made of mechanically alloyed MgB₂ has been investigated by Auger micro-analysis. Due to the process the samples contain about 15% oxygen. Pure MgB₂ crystallites were investigated as standard for stoichiometry and peak shape analysis.

Keywords: PACS; 61.16.M; 82.80.P; 84.70; 74.62.BAuger-microscopy; Auger spectroscopy; Cables—superconducting; Chemical composition—superconductors

Surface characterisation and interface studies of high-k materials by XPS and TOF-SIMS by A. Besmehn; A. Scholl; E. Rije; U. Breuer (pp. 172-176).

High-k dielectric LaAlO₃ (LAO) films on Si(100) were studied by TOF-SIMS and XPS to look for diffusion processes during deposition and additional thermal treatment and for the formation and composition of possible interfacial layers. The measurements reveal the existence of SiO₂ at the LAO/Si interface. Thermal treatment strengthens this effect indicating a segregation of Si. However, thin LAO layers show no interfacial SiO₂ but the formation of a La–Al–Si–O compound. In addition, Pt diffusion from the top coating into the LAO layers occurs. Within the LAO layer C is the most abundant contamination (10²¹at/cm³). Its relatively high concentration could influence electric characteristics. XPS shows that CO₃²⁻ is intrinsic to the LAO layer and is due to the adsorption of CO₂ of the residual gas in the deposition chamber.

Keywords: PACS; 77.84.L; 82.80.Pv; 82.80.MsHigh-k material; Metal oxide semiconductor; LaAlO; ₃; XPS; TOF-SIMS

Comparing the chemical properties of evaporated and sputtered niobium films on oxidized Si(100) wafers – preparation of oxynitride films by O. Brunkahl; W. Bock; K. Thoma; B.O. Kolbesen (pp. 177-184).

Five hundred nanometers of niobium films have been deposited on silicon(100) wafers with 100 or 300nm thermally grown oxide by electron beam evaporation and DC magnetron sputtering. SEM and AFM investigations revealed smaller crystallites and rougher surfaces for the evaporated films. The differences in film morphology resulted in lower reflection intensities in XRD for the as-deposited evaporated films. In order to investigate the influence of the structural properties on their chemical reactivities, in a first set of experiments the films were nitrided with molecular nitrogen by rapid thermal processing (RTP) at varying temperatures. In another set of experiments after nitridation in nitrogen at 1000�C an oxidation step in molecular oxygen at varying temperatures followed. The films showed different reactivities, leading to different rates of nitridation and oxidation. Sputtered films were less reactive than the evaporated films, deduced from the sequence of reaction products dependent on reaction temperature. XRD data indicated that oxynitrides have formed. Elemental depth profiles were measured by secondary ion mass spectrometry (SIMS).

Keywords: PACS; 82.80.Ms; 81.15.−zNitride; Oxynitride; Niobium; RTP; SIMS

Investigation of ultrathin tantalum based diffusion barrier films using AES and TEM by Kornelia Dittmar; Hans-J�rgen Engelmann; M. Peikert; E. Wieser; J.V. Borany (pp. 185-188).

Reliably acting diffusion barrier films are basically for the functionality of the copper inter-connect technology. Tantalum (Ta) and Tantalum nitride (TaN) are established materials for diffusion barriers against copper diffusion. In this study, the characterization of TaN like films produced using N⁺ plasma immersion ion implantation (PIII) was performed using Auger electron spectroscopy (AES). Chemical information was extracted from the Auger data using linear least square fit (LLS). The capability of the method in order to detect very little changes in the film composition dependent on small process changes was demonstrated. The nitrogen incorporation by PIII into high aspect ratio contact holes was proven using analytical TEM.

Keywords: PACS; 61.16.−d; 66.30.NyAES; TEM; Tantalum nitride; Diffusion barrier; Plasma immersion ion implantation

First nucleation steps of vanadium oxide thin films studied by XPS inelastic peak shape analysis by F. Gracia; F. Yubero; J.P. Espin�s; A.R. Gonz�lez-Elipe (pp. 189-195).

The initial states of deposition of vanadium oxide thin films have been studied by analysis of the peak shape (both inelastic background and elastic contributions) of X-ray photoemission spectra (XPS) after successive deposition experiments. This study has permitted to assess the type of nucleation and growth mechanisms of the films. The experiments have been carried out in situ in the preparation chamber of a XPS spectrometer. Thin films of vanadium oxide have been prepared on Al₂O₃ and TiO₂ by means of thermal evaporation, ion beam assisted deposition and plasma enhanced chemical vapour deposition. The thin films prepared by the first two procedures consisted of V₂O₄, while those prepared by the latter had a V₂O₅ stoichiometry. The analysis of the inelastic background of the photoemission spectra has shown that the films prepared by thermal evaporation on Al₂O₃ are formed by big particles that only cover completely the surface of the substrate when their height reaches 16nm. By contrast, the thin films prepared with assistance of ions on Al₂O₃ or with plasma on TiO₂ consist of smaller particles that succeed in covering the substrate surface already for a height of approximately 4nm. Thin films prepared by plasma-assisted deposition on Al₂O₃ depict an intermediate situation where the substrate is completely covered when the particles have a height of approximately 6nm. The type of substrates, differences in the deposition procedure or the activation of the adatoms by ion bombardment are some of the factors that are accounted for by to explain the different observed behaviours.

Keywords: PACS; 82.80.P; 81.15XPS; Thin film; Growth mechanism; Vanadium oxide; Nucleation; XPS background analysis

Electronic structure and topography of annealed SrTiO₃(111) surfaces studied with MIES and STM by Anissa G�mann; Karsten G�mann; Martin Frerichs; Volker Kempter; G�nter Borchardt; Wolfgang Maus-Friedrichs (pp. 196-199).

Perovskites of ABO₃ type like strontium titanate (SrTiO₃) are of great practical concern as materials for oxygen sensors operating at high temperatures. It is well known that the surface layer shows different properties compared to the bulk. Numerous studies exist for the SrTiO₃(100) and (110) surfaces which have investigated the changes in the electronic structure and topography as a function of the preparation conditions. They have indicated a rather complex behaviour of the surface and the near surface region of SrTiO₃ at elevated temperatures. Up to now, the behaviour of the SrTiO₃(111) surfaces under thermal treatment is not sufficiently known. This contribution is intended to work out the relation between alteration of the surface topography with respect to the preparation conditions and the simultaneous changes of the electronic structure. We applied scanning tunneling microscopy (STM) to investigate the surface topography and, additionally, metastable impact electron spectroscopy (MIES) to study the surface electronic structure of reconstructed SrTiO₃(111) surfaces. The crystals were heated up to 1000�C under reducing and oxidizing conditions. Both preparation conditions cause strong changes of the surface topography and electronic structure. A microfaceting of the topmost layers is found.

Keywords: PACS; 68.35.BStrontium titanate; Scanning tunneling microscopy (STM); Metastable impact electron spectroscopy (MIES); Surface reconstruction

Mechanical stress in ALD-Al₂O₃ films by Gunter Krautheim; Thomas Hecht; Stefan Jakschik; Uwe Schr�der; Wieland Zahn (pp. 200-204).

Mechanical stress in atomic-layer deposition (ALD)-Al₂O₃ films was investigated at room temperature and during thermal cycling up to 870°C. The films were generally under tensile stress. Thicker films (25–60nm) showed a sharp stress increase at about 780–790°C. X-ray diffraction (XRD)-, X-ray reflectance (XRR)- and X-ray photoelectron spectroscopy (XPS)-measurements indicate an irreversible phase transition from amorphous AlO(OH) to a mixture of different crystalline Al₂O₃-phases. Annealing at higher temperatures leads to a stress reduction as a result of diffusion and recovery processes. The stress behaviour of thinner films (<20nm) during thermal cycling is quite different. Tensile stress increases with increasing temperature and decreases to nearly the same value during cooling down. The process is continuous and reversible.

Keywords: PACS; 77.55; 68.55; 68.60; 07.10.LDielectric thin films; Atomic-layer deposition; Temperature dependence of mechanical stress; Phase transition; Stress relaxation

Formation of niobium oxynitrides by rapid thermal processing (RTP) by V.A. Matylitskaya; W. Bock; K. Thoma; B.O. Kolbesen (pp. 205-210).

The potential of rapid thermal processing (RTP) for the preparation of thin films of niobium oxynitrides was investigated. The 200 and 500nm niobium films were deposited via sputtering on oxidized silicon(100)- and on sapphire(1−102)-substrates. At first, oxidation of niobium films in molecular oxygen and then nitridation in ammonia using an RTP-system was performed. The films were characterized before and after the oxidation and nitridation processes by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and secondary ion mass spectrometry (SIMS). The influence of the two different substrates, amorphous SiO₂ and single crystalline sapphire on the reactivity of the niobium films was studied in dependence of temperature, time of reaction and film thickness. The existence of niobium oxynitride formation was verified for some of the films. In some of the experiments, crack formation in the films or even delamination of the Nb-films from the substrates was observed.

Keywords: Niobium oxynitride; Rapid thermal processing (RTP); Thin films; X-ray diffraction (XRD); SIMS depth profile

Effect of Ag-alloying addition on the stress–temperature behavior of electroplated copper thin films by S. Menzel; S. Strehle; H. Wendrock; K. Wetzig (pp. 211-214).

The effect of Ag-alloying on the microstructural and thermo-mechanical properties of electrochemically deposited Cu thin films was investigated using the focused ion beam technique, scanning electron microscopy and the electron back scatter diffraction (EBSD) technique as well as the substrate curvature method to study their stress–temperature and stress relaxation behavior. The results show that the linear elastic behavior of 1μm thick Cu films is significantly improved by alloying. Additionally, after annealing such films have an excellent low electrical resistivity of 1.9–2.0μΩcm, which meets the requirements of the roadmap ITRS [International Technology Roadmap for Semiconductors, Edition 2003, part: interconnect, available athttp://public.itrs.net/].

Keywords: PACS; 85.40.Ls; 66.30.QaElectroplated Cu(Ag) alloy metallization; Microstructure; Stress–temperature behavior; Electromigration

Material transport in Al-metallizations of power-loaded SAW structures by S. Menzel; M. Pekar�?ikova; M. Hofmann; T. Gemming; K. Wetzig (pp. 215-217).

Material transport in Al/Ti-finger electrodes on LiNbO₃ substrates of power-loaded surface acoustic wave (SAW) structures were investigated under microscopic observation with respect to stress-induced material transport. Additionally, investigations were carried out before and after SAW loading during lifetime experiments. For the experiments, a special power SAW test structure was applied realizing travelling SAWs. The results show that the microstructure of the electrodes was damaged by void and hillock formation even at moderate input power. This changes the electrical and acoustical properties of the SAW structures irreversibly. The logarithmic time-to-failure (TTF) of damaged SAW structures depends linearly on loading time and rf power.

Keywords: PACS; 66.30.−h; 77.65.DqAcoustomigration; Al-metallization; SAW structure

XPS and AES investigations of hard magnetic Nd–Fe–B films by S. Oswald; S. F�hler; S. Baunack (pp. 218-222).

Nd–Fe–B is a promising material system for the preparation of thin films with good hard magnetic properties. One problem of this material class is the sensitivity against oxidation, resulting in a degradation of the magnetic properties. Using XPS depth profiling in combination with peak-shape analysis it is shown that already after several hours oxygen can diffuse deep into the thin laser-deposited films and that Nd is mainly responsible for the oxidation. Local element analysis with AES revealed boron inhomogeneities from droplet formation during laser deposition. These problems can be solved by using a capping Cr layer and an FeB target for thin film preparation, respectively.

Keywords: PACS; 82.80.Pv; 68.55.Nq; 75.70−iHard magnetic films; Oxidation; Electron spectroscopy; Depth profiling; Phase formation; Factor analysis

Characterization of PECVD boron carbonitride layers by T. Thamm; K.-U. K�rner; W. Bohne; E. Strub; J. R�hrich; S. St�ckel; G. Marx (pp. 223-226).

BCN films on silicon substrates were deposited with two different PECVD techniques. A microwave plasma with RF-bias enhancement (MW-PECVD) and a direct current glow discharge plasma system (GD-PECVD) was used with N-trimethylborazine (TMB) and triethylamine borane (TEAB) as precursors and with benzene as an additional carbon source. Argon and nitrogen were used as plasma gases. Substrate temperature, substrate bias and gas composition were varied. ERDA (elastic recoil detection analysis) measurements yield information on the layer composition regarding the concentrations of the elements boron, carbon, nitrogen and hydrogen. Depth profiles are also available. The hydrogen content in the produced BCN layers strongly depends on the substrate temperature and increases up to 35at.%. Depth profiles show a homogeneous distribution of the elements B, C, N and H over the entire layer thickness. Further, the layers were examined regarding their structure (FTIR spectroscopy) and their mechanical properties (nanoindentation measurements).

Keywords: PACS; 81.15.−z; 52.75.Rx; 82.80.ChBCN; PECVD; Hardness; Hydrogen content; ERDA; FTIR spectroscopy

Analysis of chemical dissolution of the barrier layer of porous oxide on aluminum thin films using a re-anodizing technique by I. Vrublevsky; V. Parkoun; V. Sokol; J. Schreckenbach (pp. 227-233).

Chemical dissolution of the barrier layer of porous oxide formed on thin aluminum films (99.9% purity) in the 4% oxalic acid after immersion in 2moldm⁻³ sulphuric acid at 50°C has been studied. The barrier layer thickness before and after dissolution was calculated using a re-anodizing technique. It has been shown that above 57V the change in the growth mechanism of porous alumina films takes place. As a result, the change in the amount of regions in the barrier oxide with different dissolution rates is observed. The barrier oxide contains two layers at 50V: the outer layer with the highest dissolution rate and the inner layer with a low dissolution rate. Above 60V the barrier oxide contains three layers: the outer layer with a high dissolution rate, the middle layer with the highest dissolution rate and the inner layer with a low dissolution rate. We suggest that the formation of the outer layer of barrier oxide with a high dissolution rate is linked with the injection of protons or H₃O⁺ ions from the electrolyte into the oxide film at the anodizing voltages above 57V.

Keywords: PACS; 82.45.+z; 81.05.RmAluminum; Porous alumina; Barrier oxide layer; Dissolution rate; Re-anodizing

XPS and ARXPS investigations of ultra thin TaN films deposited on SiO₂ and Si by M. Zier; S. Oswald; R. Reiche; K. Wetzig (pp. 234-239).

TaN films were deposited by reactive DC magnetron sputtering onto Si and SiO₂ with thicknesses of less than one monolayer up to 10nm. After this, the samples were transferred into the analysis chamber without breaking the vacuum and analysed by means of X-ray photoelectron spectroscopy (XPS) and angular resolved XPS (ARXPS).XPS measurements as a sensitive method to characterise chemical states showed a silicon nitride formation at the interface at deposition on Si. On the SiO₂ no reaction was found at the interface.Based on these observations layer models for quantification of ARXPS measurements by means of model calculations were derived, so it was possible to obtain information on the in-depth element distribution in a non-destructive manner. For comparison to the ARXPS investigations analyses of the inelastic background of the Ta4d peak are shown and discussed.

Keywords: PACS; 33.60.Fy; 79.60.Jv; 81.15.CdXPS; ARXPS; Tantalum nitride; Diffusion barrier; Silicon; Silicon oxide

Advances in X-ray excitation of Kossel patterns by a focusing polycapillary lens by E. Langer; S. D�britz; W. Hauffe; M. Haschke (pp. 240-244).

In this paper, the polychromatic X-ray excitation of Kossel patterns by an X-ray tube and a focusing polycapillary lens will be presented. Additionally, it will be shown that the lateral resolution of the Kossel technique under X-ray tube excitation can be improved and the exposure times can be strongly reduced by using a polycapillary lens. The advantageous combination of X-ray fluorescence and crystal structure analysis by means of Kossel microdiffraction will be demonstrated.

Keywords: PACS; 61.10.Yh; 78.66.BzKossel technique; Lattice source interferences; Polycapillary lens

Shells on nanowires detected by analytical TEM by J�rgen Thomas; Thomas Gemming (pp. 245-251).

Nanostructures in the form of nanowires or filled nanotubes and nanoparticles covered by shells are of great interest in materials science. They allow the creation of new materials with tailored new properties. For the characterisation of these structures and their shells by means of analytical transmission electron microscopy (TEM), especially by energy dispersive X-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS), the accurate analysis of linescan intensity profiles is necessary. A mathematical model is described, which is suitable for this analysis. It considers the finite electron beam size, the beam convergence, and the beam broadening within the specimen. It is shown that the beam size influences the measured result of core radius and shell thickness. On the other hand, the influence of the beam broadening within the specimen is negligible. At EELS, the specimen thickness must be smaller than the mean free path for inelastic scattering. Otherwise, artifacts of the signal profile of a nanowire can pretend a nanotube.

Keywords: PACS; 61.46; 61.16BAnalytical TEM; Nanowires; Nanotubes; Model for linescan profiles

Multivariate data analysis for depth resolved chemical classification and quantification of sulfur in SNMS by M. Sommer; J. Goschnick (pp. 252-256).

The quantification of elements in quadrupole based SNMS is hampered by superpositions of atomic and cluster signals. Moreover, the conventional SNMS data evaluation employs only atomic signals to determine elemental concentrations, which not allows any chemical specifications of the determined elements. Improvements in the elemental quantification and additional chemical information can be obtained from kinetic energy analysis and the inclusion of molecular signals into mass spectra evaluation. With the help of multivariate data analysis techniques, the combined information is used for the first time for a quantitative and chemically distinctive determination of sulfur. The kinetic energy analysis, used to solve the interference of sulfur with O₂ at masses 32–34 D, turned out to be highly important for the new type of evaluation.

Keywords: PACS; 82.80.MsSNMS; Organic and inorganic compounds; Sulfur; Classification; Quantification

SNMS investigations of platinum-doped nanogranular tin dioxide layers by T. Schneider; M. Sommer; J. Goschnick (pp. 257-260).

Thin platinum-doped nanogranular SnO₂ layers are examined because of its high gas sensitivity and fast gas response to be applied in gas sensor microarrays. The nanogranular metal oxide layers were prepared from a colloidal dispersion using spin coating on silicon substrates. Field emission scanning electron microscopy (FE-SEM) investigations showed quite homogeneous layers of 20nm particles, containing a few holes of some micron width, probably due to bubbles introduced into the layer during wet deposition. Depth resolved analysis with secondary neutral mass spectrometry (SNMS) was employed to characterize the elemental content and depth distribution of the 20nm particle layers. A platinum content of approx. 1at.%, homogeneously spread throughout the particles was found, as well as carbon and chlorine residues of a few atomic percent enriched at the surface of the particles.

Keywords: PACS; 82.80.MsSNMS; Gas sensor micro array; Nanoparticle layer; Catalytic additive; Quantification

Analysis of new electrical signals in respect to quantification of radio frequency glow discharge emission spectrometry by L. Wilken; V. Hoffmann; K. Wetzig (pp. 261-265).

Radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) is routinely used for the chemical analysis of solid samples. For quantification two independent electrical signals of the discharge are required. These are provided in real time by the glow discharge source with integrated voltage and current sensors. The available time-dependent voltage and current must be reduced. For this purpose a plasma equivalent circuit is used. It is shown that the cathode voltage and active cathode current describe the sputtering and excitation well. Measuring standard reference materials at constant cathode voltage and cathode current results in linear calibration curves.

Keywords: PACS; 82.80; 52.80.H; 52.70Radio frequency; Glow discharge; Optical emission spectroscopy; Plasma equivalent circuit

Characterisation of molybdenum intermediate layers in Cu–C system with SIMS method by K.E. Mayerhofer; C. Schrank; C. Eisenmenger-Sittner; H. Hutter (pp. 266-270).

In the design of new high-speed chip generations a huge problem is bleeding off process heat during their operation. The installation of heat sinks onto such chips is necessary. Possible materials are copper-coated carbon composites. They combine high thermal conductivity with low density and a tailorable coefficient of thermal expansion (CTE). The low wettability of copper onto carbon necessitates a surface pretreatment.Flat slices of nitrogen-plasma etched vitreous carbon (Sigradur G) made up as a model system for carbon fiber material. The later serial fabrication of these fibers includes a hot pressing step after the deposition joining them to solid composites. It is simulated by a heat treatment step of the compound. The first sample series consisted of samples with 100nm molybdenum and 500nm copper layers (sputter deposited), as deposited and heat treated. The second run concludes samples without molybdenum layer but an additional 50nm cap layer deposited after heat treatment.All samples were investigated with secondary ion mass spectrometry (SIMS), showing a diffusion of carbon into the molybdenum layer. Measuring MCs⁺ secondary ions, both matrix elements and trace elements were detectable sufficiently.

Keywords: PACS; 82.80.MsSIMS; Sputter deposition; Heat drain; Molybdenum; Molybdenum carbide

Range evaluation in SIMS depth profiles of Er-implantations in silicon by K. Mayerhofer; H. Foisner; K. Piplits; G. Hobler; L. Palmetshofer; H. Hutter (pp. 271-277).

In the last decade ion implantation of common dopants in silicon has been almost full characterised. However, data of inner transition elements are based on few measurements or even extrapolations. Our investigations focus on erbium, an upcoming dopant in photonic applications. Some of us have previously found errors of 20% in the projected range of Er in Si and SiO₂ when comparing the range profiles measured with SIMS and simulations using SRIM, T2D, and our own binary collision simulator IMSIL. Because of the far-reaching consequences, we have performed additional, more precise experiments to confirm our previous results.Equal doses of Er has been implanted into SIMOX wafers with energies of 100, 200, 300, 400, 500, and 600keV. Profiles have been measured with secondary ion mass spectrometry (SIMS). Relative sensitivity factors (RSF) were gathered from low-energy implantations, remaining within the Si top layer. We used the Si/SiO₂ interface at exactly 217.7nm to calibrate the depth scale of all profiles. In addition dynamical Monte-Carlo simulations of the sputter process were taken to correct the depth scale and the interface position.

Keywords: PACS; 81.70.Jb; 82.80.Ms; 79.20.Rf; 68.55.LnSIMS; Secondary ion mass spectrometry; Implantation; Sputter rate; Profile depth

SIMS investigation of gettering centres produced by phosphorus MeV ion implantation by D. Krecar; M. Fuchs; R. K�gler; H. Hutter (pp. 278-281).

The ion implantation is a well-known standard procedure in electronic device technology for precise and controlled introduction of dopants into silicon. Damages caused by implantation act as effective gettering zones, collecting unwanted metal impurities. In this work, the consequences of high-energy ion implantation into silicon and of subsequently annealing were analysed by means of secondary ion mass spectrometry (SIMS). The differences in impurities gettering behaviour were studied in dependence of the implantation dose and annealing time at T=900�C.

Keywords: PACS; 61.72.Tt; 61.72.Yx; 68.49.Sf; 82.80.MsIon implantation; Gettering effect and defects; R; _P; -,; R; _P; /2- and trans-; R; _P; -effect; Secondary ion mass spectrometry (SIMS)

2D and 3D SIMS investigations on sintered steels by Dragan Krecar; J�rgen Zwanziger; Vassilka Vassileva; Herbert Danninger; Herbert Hutter (pp. 282-285).

Powder metallurgy (PM) is a well-established method for manufacturing ferrous precision parts. Sintering is one of the important production steps and can be strongly enhanced (activated) by formation of a liquid phase during the sintering process. The liquid phase can be reached by the addition of alloying elements (e.g., copper) or sintering activators (e.g., phosphorus) and is formed by melting of eutectic phase mixtures or by incipient melting. The main investigations presented in this work are done by secondary ion mass spectrometry (SIMS): 2D and 3D elemental distribution. Additionally, impact energy and hardness measurements were performed in order to study the influence of phosphorus on mechanical properties. The concentration of P in different samples was varied between 0 and 1 weight percent (wt.%), the carbon content was consistently 0.5wt.%. Nominal specimens were sintered at 1120 and 1250�C in protective atmosphere of flowing nitrogen to determine the influence of sintering temperature.

Keywords: PACS; 68.49.Sf; 82.80.Ms; 81.20.Ev2D–3D SIMS; Sintering; Activator; Phosphorus; PM

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Applied Surface Science (v.252, #1)