Epitaxial growth of AlN films on single-crystalline Ta substrates

We have demonstrated the first epitaxial growth of AlN films on single-crystalline Ta substrates by the use of a low-temperature growth technique based on pulsed laser deposition (PLD). Although previous AlN films grown on Ta(100) and (111) substrates have exhibited quite poor crystallinity, an epitaxial AlN(0001) film with an in-plane epitaxial relationship of AlN[112¯0]//Ta[001] has been obtained on a Ta(110) substrate at a growth temperature of 450 °C. We found that the full-width at half-maximum values for the crystal orientation distribution in the tilt and twist directions of the AlN film were 0.37° and 0.41°, respectively. Grazing-incidence X-ray reflection (GIXR) and X-ray photoelectron spectroscopy (XPS) measurements have revealed that the AlN/Ta heterointerface is quite abrupt, and that its abruptness remains unchanged even after annealing at 1000 °C.     

Growth and characterization of ultrathin carbon films on electrodeposited Cu and Ni

Ultrathin carbon films were grown on different types of metallic substrates. Free‐standing foils of Cu and Ni were prepared by electroforming, and a pure Ni film was obtained by galvanic displacement on a Si wafer. Commercial foil of Ni 99.95% was used as a reference substrate. Carbon films were grown on these substrates by chemical vapour deposition in a CH₄‐H₂ atmosphere. Obtained films were characterized by Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ultraviolet photoemission spectroscopy. The XPS at grazing collection angle was used to determine the thickness of carbon films. Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area were investigated from Raman data, optical images, and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes, was determined from C KVV spectra acquired by using X‐rays and electron beam. A formation of an intermediate layer of metal hydroxide was revealed in the samples with graphene overlayer.     

Surface analysis of films and film systems produced by pulsed laser deposition

Ceramic films and film systems (ZrO₂ films, ZrO₂/Ti multilayers, and BN films) are deposited by pulsed laser deposition (PLD) and analyzed using X-ray photoelectron (XPS), Auger electron (AES), and micro-Raman spectroscopies. The electron spectroscopies are used to determine the film stoichiometry, the nature of the bonding, and to specify contaminant species. The micro-Raman spectroscopy gives information on crystal structure, grain size, and mechanical stress within the films. In ZrO₂ films a stoichiometry is achieved with typically 5%, with only weak dependencies on processing variables. The only contaminants are a small amount of water from the ambient gas and a carbonaceous surface layer. Multilayers consisting of alternating ZrO₂ and Ti layers exhibit a TiC contamination within the Ti layers. Depending on the processing variables, BN films may be nearly stoichiometric or may have significant, even dominant contaminations throughout the film from elemental B, B₂O₃, and/or a boron-oxynitride species. The first component is due to the non-stoichiometric material removal from the target (N-depletion) at low laser fluences, as confirmed by XPS measurements on irradiated targets. The second and third arise from H₂O in the ambient, and exhibit a complex dependence on processing variables. Micro-Raman spectra show only amorphous or hexagonalphase BN. Depending on the position on the substrate relative to the laser-induced vapour/plasma plume, there may be a particle deposition or mechanical stress within the films, as evidenced from large shifts (up to 15 cm^–1) of the Raman spectral peaks.     

ZnO thin films prepared on titanium substrate by PLD technique at different substrate temperatures

ZnO thin films were grown by pulsed laser deposition on titanium substrates at different substrate temperatures ranging from 300 to 700 °C. X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS),photoluminescence, and Raman spectroscopy are employed to investigate the change of properties. XRD, XPS, and Raman data showed that the films consisted of TiO₂ at high substrate temperature, which will deteriorate the crystallization quality of ZnO films. The optimum temperature for the growth of ZnO films on the Ti substrate is about 500 °C in this paper. The ZnO films grown on titanium substrate can be used in direct current, microwave, and medical applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization of sputter-deposited YBaCuO films by X-ray photoelectron spectroscopy

Summary Thin films of YBaCuO have been deposited onto SrTiO₃ (100) single crystals by different sputter techniques. At substrate temperatures around 700°C critical current densities as high as 5.9×10⁶ A/cm² at 77 K could be achieved. X-ray photoelectron spectroscopy (XPS) has been used to characterize the surface composition and the surface homogeneity of the films. The existence of the superconducting perovskite structure beside other surface species can be detected for example by observing the Ba 4d_5/2 emission at its characteristic binding energy of 87.3 eV. Using XPS as a quantitative analytical technique it has been shown that it is possible to detect metallic contamination (Pt, Cr) in the films at a detection limit of 0.1 atomic percent of the cations. The occurrence of the metallic contamination has been traced back to formation of volatile metal-oxides of the substrate heater wires during the deposition process.     

Sol-Gel Preparation and Characterization of Ag-TiO2 Nanocomposite Thin Films

Ag-TiO₂ thin films were prepared with a sol-gel route, using titanium isopropoxide and silver nitrate as precursors, at 0.03 and 0.06 Ag/Ti nominal atomic ratios. After drying at 80°C, the films were fired at 300°C and 500°C for 30 min. The films were analysed by X-ray diffraction (XRD) with glancing angle, and X-ray photoelectron spectroscopy (XPS), with depth profiling of the concentration. XPS analysis showed the presence of C and N as impurities in the nanocomposite films. Their concentration decreased with increasing the firing temperature. Chemical state analysis showed that Ag was present in metallic state, except for the very outer layer where it was present as Ag⁺. For the films prepared with a Ag/Ti concentration of 0.06, depth profiling measurements of the film fired at 300°C showed a strong Ag enrichment at the outer surface, while composition remained almost constant within the rest of the film, at 0.019. For the films heated to 500°C, two layers were found, where the Ag/Ti ratios were 0.015 near the surface and 0.026 near the substrate.     

Preparation and Characterizations of TiO2/Organically Modified Silane Composite Materials Produced by the Sol-Gel Method

TiO₂/organically modified silane (ORMOSIL) composite materials produced by the sol-gel method were studied for optical waveguide applications. High optical quality waveguiding films on different substrates, including silicon, gallium arsenide, silica/silicon substrates, and microscope glass slides, were prepared from high titanium content (0.2 molar) ÿ-glycidoxypropyltrimethoxysilane at low temperature. Scanning electron microscopy (SEM), atomic force microscopy (AFM), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been used to investigate the optical and structural properties of the composite films. The TGA/DTA results showed that the organic compounds in the film would tend to decompose in the temperature range from 200°C to 500°C. SEM and AFM results showed that a dense and porous-free composite material film could be obtained at the heat treatment temperature of 100°C. It was also shown that ORMOSIL is integrated in the glass, providing low shrinkage and high cracking resistance. The propagation loss properties of the composite films were also investigated. About 1.1 dB/cm propagation loss of the planar waveguide film was obtained at the wavelength of 633 nm.     

Characterization of molybdenum carbide nanoparticles formed on Au(111) using reactive-layer assisted deposition

Temperature programmed desorption (TPD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM) have been used to characterize molybdenum carbide nanoparticles prepared on a Au(111) substrate. The MoC(x) nanoparticles were formed by Mo metal deposition onto a reactive multilayer of ethylene, which was physisorbed on a Au(111) substrate at low temperatures (<100 K). The resulting clusters have an average diameter of approximately 1.5 nm and aggregate in the fcc troughs located on either side of the elbows of the reconstructed Au(111) surface. Core level XPS shows that the electronic environment of the Mo and C atoms in the nanoparticles is similar to that found in Mo(2)C(0001) single crystals and carburized Mo metal surfaces. Peak intensities in XPS and AES spectra were used to estimate an average Mo/C atomic ratio of 1.2 +/- 0.3 for nanoparticles annealed above 600 K.     

Synthesis and oxidation of CeN film: an in situ investigation by electron spectroscopies

Nearly stoichiometric CeN film is synthesized on a Re(0001) substrate in an ultrahigh vacuum system involving highly active N atoms in the growth process, generated by thermal decomposition of NH3 by use of a hot tungsten filament. The electronic structure of the CeN film as prepared is equivalent to that of a single crystal observed by in situ Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). AES and XPS investigations show that CeN film is directly oxidized to CeO2 after exposure to O2 at room temperature. However, CeN changes into Ce2O3 after annealing in approximately 10(-6) mbar of O2 atmosphere at elevated temperature.     

Synthesis and evaluation of bis-β-diketonate dioxotungsten(VI) complexes as precursors for the photodeposition of WO3 films

In this paper non-stoichiometric tungsten oxide thin films have been successfully prepared by direct UV irradiation of bis-β-diketonate dioxotungsten(VI) precursor complexes spin-coated Si(1 0 0) substrates. Photodeposited films were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the surface morphology examined by Atomic Force Microscopy (AFM). The results of XRD analysis showed that the as-photodeposited WO_3−x films are amorphous and have a rougher surface than thermally treated films. Post-annealing of the films in air at 500 °C transforms the sub-oxides to a monoclinic WO₃ phase.     

Quantitative surface analysis of Fe?Ni alloy films by XPS,AES and SIMS

A comparison of quantitative surface analyses of Fe? Ni alloy thin films by various methods has been proposed as a pilot study by the Surface Analysis Working Group of the Consultative Committee for Amount of Substance (CCQM). To test the suitability of Fe? Ni for this purpose, alloy films with different compositions were grown on Si(100) wafers by ion‐beam sputter deposition and the compositions were certified by an isotope dilution method using inductively coupled plasma‐mass spectrometry. The alloy compositions measured with X‐ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) using sensitivity factors determined from pure Fe and Ni metal films agreed with the certified mean values to better than 2%. The alloy compositions quantified by secondary ion mass spectrometry (SIMS) with a C₆₀ ion source agreed to better than 4% with the certified compositions if one of the alloys was used to establish the relative sensitivity factors (RSFs). These results indicate that the quantification of the Fe? Ni alloy is a good method for a CCQM pilot study because matrix effects and ion‐sputtering effects are small for these analytical methods. Copyright © 2007 John Wiley & Sons, Ltd.     

Passivation of InP(100) substrates: first stages of nitridation by thin InN surface overlayers studied by electron spectroscopies

This article investigates the nitridation effect of InP(100) semiconductor surfaces performed using a glow discharge cell. Auger electron spectroscopy and XPS were used to understand the different steps of this process. An important point is the initial quantity of metallic indium on the InP(100) surfaces. Indeed the indium droplets, created in well‐known quantity, play the role of precursor. At a relatively low temperature of 523 K the system undergoes surface restructuring, which includes removal of the In droplets and the formation of two InN monolayers. Phosphorus–nitrogen bonds have been detected by the analysis of P LMM Auger peaks, and In? N bonds by analysis of the In 4d XPS peak. However, the presence or not of metallic indium inside this InN overlayer is crucial for passivation of the substrate. Ex situ photoluminescence measurements correlated to the electron spectroscopies results have shown the good passivation effect of the InP(100) surfaces by InN overlayers for 40 min of nitridation. Copyright © 2005 John Wiley & Sons, Ltd.     

Facetting of Fe-15% Cr-N, Fe-3% V-C and Fe-3% V-C,N (111) surfaces

Summary Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and scanning electron microscopy (SEM) have been used to study the surface chemistry of crystallographically open bcc (111) surfaces of Fe-15% Cr-N, Fe-3% V-C and Fe-3% V-C,N alloys. The binary and ternary surface phases CrN, VC and V(C,N) were formed at temperatures ranging from 450 to 750°C depending on the alloy. On Fe-15% Cr-30ppmN (111) two-dimensional surface compounds CrN were formed at temperatures above 600°C according to the bulk phase diagram of the Fe-Cr-N system, whereas on Fe-15% Cr-N samples with nitrogen contents of more than about 100 ppm the precipitation of three-dimensional CrN took place at temperatures below 600°C. Optical and SEM micrographs as well as oxidation experiments at room temperature indicated that the substrate surfaces are inhomogeneously covered by the surface phases. Facetting of the bcc (111) surfaces induced both by cosegregation of the solutes and by surface precipitation was observed in real space (SEM) as well as in reciprocal space (LEED). It is shown that the surface phases are epitaxially arranged on (100) facets of the substrate.     

Surface morphology and electrical properties of copper thin films prepared by MOCVD

Thin copper films have been grown in a vertical MOCVD (Metal-Organic Chemical Vapor Deposition) reactor using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) copper(II), Cu(thd)₂, as precursor. Deposition has been carried out in a pure hydrogen atmosphere (pressure: 3, 20 mbar) at different substrate temperatures (350–750 ° C). The films have been investigated by profilometry, four-point resistivity measurements, ESCA, AES, XRD, AFM, and Normarsky microscopy. An unusual dependence of the film thickness with deposition time has been observed. Rapid growth occurred in the first minutes resulting in badly conducting films (thickness below 1000 Å). Good electrical resistivities have been obtained above 2000 Å. AFM has been used to gain information about the surface morphology of the films with different thicknesses. The grain size and surface roughness increased with increasing film thickness. Small grains grew in the beginning and the electrical properties have been governed by the highly Ohmic bridges between the individual grains.     

Preparation and Characterization of Titania Thin Films from Aqueous Solutions

Dip- or spin-coating and characterization of titania (TiO₂) thin films from various aqueous solutions have been studied. The aqueous titanium solutions mainly used in this study were halogen- and chelate-free solutions with the concentrations up to 1.4 M derived from titanium isopropoxide (TIP) with tetramethylammonium hydroxide (TMAOH) or some alkylamines, while aqueous and alcoholic solutions containing titanium atoms stabilized chelating ligands were examined for comparison. The TiO₂ films prepared from the TIP-TMAOH solution were already crystallized at 350°C to anatase form and those formed at 600°C had high transparency and refractive indices of 2.40. No carbon residue in the film prepared at 400°C was detected by XPS. The pure anatase form was sustained up to 850°C. Interestingly, it was found that the (004) preferentially oriented anatase films were obtained from TIP-lactic acid (LA) system until 700°C. The solutions containing citric acid (CA) or alkanolamines yielded anatase and rutile form fired at the temperatures equal to or higher than 600°C. Carbon residue was detected in the film fired at 400°C. The film thickness monotonically decreased from the upper to the bottom ends of the substrate. However, it was found that the thickness uniformity was drastically improved by an addition of sucrose to the aqueous solutions. The effects of the solution composition and polyhydroxy compounds on the crystal modifications of formed films and the film uniformity are discussed.     

Vanadium Doped Sol-Gel TiO2 Coatings

A study of the experimental conditions required to obtain vanadium doped sol-gel TiO2 coatings is presented. Tetraethyl orthotitanate was employed as the TiO2 source and VCl3, VOSO4 · H2O and VOSO4 dissolved H2SO4 where employed as vanadium sources.Dip coating has been used to produce coatings on silicon wafers, spectral carbon electrodes and titanium electrodes. Both supported and unsupported films have been studied by UV-Vis spectra, IR spectroscopy and X-ray diffraction (XRD). The measurements have been made on samples as prepared and treated thermally at temperatures between 100°C and 300°C. The thermal treatment temperatures have been established from DTA/TGA measurements.The vanadium doped sol-gel TiO2 coatings have been tested as sensors for redox potential measurements in electrochemical processes. The influence of both the thickness of films and the nature of substrate has been investigated.     

Photoelectrochemical Properties of Sol-Gel Processed Ag-TiO2 Nanocomposite Thin Films

Ag-TiO₂ thin films were prepared with a sol-gel route, using titanium isopropoxide and silver nitrate as precursors, at 0, 0.03 and 0.06 Ag/Ti nominal atomic ratios. After drying at 80°C, the films were fired at 300°C, 500°C, and 600°C for 30 min and 5 h. Glancing angle X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS), with depth profiling of the concentration, were used to study the films. XPS analysis showed the presence of C and N as impurities in the nanocomposite films. Their concentration decreased with increasing the firing temperature. Chemical state analysis showed that Ag was present in metallic state, except for the outer layer where it was present as Ag⁺. For the films prepared with a Agt/Ti concentration of 0.06, depth profiling measurements of the film fired at 300°C showed a strong Ag enrichment at the outer surface, while composition remained almost constant within the rest of the film, at Ag/Ti atomic ratio of 0.02. Two layers were found for the films heated to 500°C, where the Ag/Ti ratios were 0.015 near the surface and 0.03 near the substrate. The photoelectrochemical properties of Ag-TiO₂ were studied for thin films deposited on ITO substrates. Photocurrents of Ag-TiO₂ nanocomposite electrodes fired at 300°C were observed even at visible light, for wavelengths longer than 400 nm.     

XANES and XPS characterization of hard amorphous CSixNy thin films grown by RF nitrogen plasma assisted pulsed laser deposition

Amorphous carbon silicon nitride thin films were grown on (100) oriented silicon substrates by pulsed laser deposition (PLD) assisted by an RF nitrogen plasma source. Up to about 30 at. % nitrogen and up to 20 at. % silicon were found in the hard amorphous thin films by XPS in dependence on the composition of the mixed graphite / Si₃N₄ PLD target. The universal nanohardness was measured to be at maximum load force of 0.1 mN up to 23 GPa for thin CSi_xN_y films with reference value of 14 GPa for single crystalline silicon. X-ray photoelectron spectroscopy (XPS) of CSi_xN_y film surfaces showed a clear correlation of binding energy and intensity of fitted features of N 1s, C 1s, and Si 2p peaks to the composition of the graphite / Si₃N₄ target and to nitrogen flow through the plasma source, indicating soft changes of binding structure of the thin films due to variation of PLD parameters. Auger electron spectroscopy (AES) of Si KL₂₃L₂₃;¹D Auger transition gave a detailed view of bonding structure of Si in the CSi_xN_y films. The intensity of π* and σ* resonances at the carbon K-edge X-ray absorption near-edge structure (XANES) of the CSi_xN_y films measured at BESSY I corresponded to the nanohardness of the CSi_xN_y films, thus giving insight into chemical binding structure of superhard amorphous materials.     

Quantitative AES,XPS and RBS determination of intergranular bismuth coverage in copper bicrystals at 500 °C

We report on a comparative measurement of intergranular bismuth coverage on a copper substrate using Auger electron spectroscopy (AES), x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Bicrystalline copper samples were put in presence of bismuth vapour at 500 °C (consequently embrittled by the grain‐boundary penetration of Bi atoms), water‐quenched and subsequently fractured at room temperature. Each fracture surface was analysed by AES, XPS and RBS with the help of quantitative procedures developed for each of the three techniques. All possible sources of discrepancy were carefully examined. The combined quantitative approaches have led to excellent agreement. Such a good agreement constitutes a necessary condition to begin a critical discussion on the mechanisms potentially involved in the liquid metal embrittlement (LME) phenomenon. Copyright © 2005 John Wiley & Sons, Ltd.     

Study of the cobalt diffusion in CVD-layers by scanning Auger microscopy (SAM)

Summary Multilayers of TiC/Al₂O₃/TiC were deposited by CVD (Chemical Vapor Deposition) on pure cobalt, cemented carbides (WC-Co) and Al₂O₃ substrates. By a low angle cut produced with a ball cratering technique, depth profile measurements were determined by SAM.In the case of the cobalt substrate, the cobalt concentration in the first TiC layer was greater than 10 at %. For the cemented carbide substrate, an enrichment at both interfaces of the first TiC layers was clearly detected. This occurred by diffusion of Co during the cleaning of the hot (1050 ° C) CVD reactor with hydrogen while no CVD deposition occurred. A thin Al₂O₃ layer (0.5 m) proved to be a very efficient diffusion barrier for cobalt.The cobalt diffusing from the substrate acted as accelerator and grain refining agent for the TiC CVD deposition.

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Untersuchung der Kobaltdiffusion in CVD-Schichten mit Scanning Auger Mikroskopie (SAM)