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Eingeladener Vortrag
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In many areas of material sciences, hydrogen analysis is of particular importance. For example, hydrogen is most abundant as impurity in thin film materials depending on the deposition process and has great influence on the chemical, physical and electrical properties of many materials. Existing bulk reference materials (RMs) are not suited for surface sensitive analytical methods like elastic recoil detection analysis (ERDA) or nuclear reaction analysis (NRA). To overcome this serious lack of (certified) thin-layer reference materials for the determination of hydrogen in the near-surface region (12 µm depth), we produced stable, homogeneous amorphous silicon layers on Si-wafers (aSi:HSi) by means of chemical vapour deposition (CVD), while about 10% of hydrogen was incorporated in the Si-layer. Homogeneity and stability were proved by NRA whereas traceability of reference values has been assured by an international interlaboratory comparison.
The Spray Ion Layer Gas Reaction (Spray-ILGAR) technique is a new variation on the ILGAR technique used to prepare chalcogenide thin films. High quality indium sulfide thin films were produced by Spray-ILGAR with an indirect bandgap of 2.2 eV and a high suitability for use as buffer layers in chalcopyrite solar cells. The process involves the cyclical spray deposition of an indium containing precursor layer followed by its conversion to sulfide using hydrogen sulfide gas. Analysis of the deposition reveals that the indium chloride based precursor is transported via the vapour phase from the spray droplets to the substrate surface.
The deposition of boron carbonitride layers
on silicon substrates by a microwave plasma enhanced
chemical vapour deposition (MW-PECVD) process using
N-trimethylborazine (TMB) and benzene as precursors
is presented. As plasma gases argon and nitrogen
were used. In this investigation we focus on the influence
of the gas composition, substrate temperature and
-bias on the layer composition, layer structure as well as
the thermal stability. The films were analyzed with respect
to their composition and bonding structure using
elastic recoil detection analysis (ERDA) and X-ray
photoelectron spectroscopy (XPS). Furthermore, nanoindentation
measurements before and after annealing
tests at 500 and 700°C were performed. The measurements
show a strong dependence of the structure and
mechanical properties on the substrate temperature.
The hydrogen content strongly decreases to 8 at.% with
higher substrate temperatures. Simultaneously, the layer
hardness and Youngs modulus increase up to 21 and
173 GPa, respectively. The hardness does not decrease
after annealing for 1 hour at 700°C.
The TOF-ERDA setup at the ISL Berlin was used to perform precise energy loss measurements of scattered ions. Different samples were irradiated with a 350 MeV Au beam and the TOF of the recoiled elements was measured without and with an additional metal stopping foil (Fe, Ag or Au) behind the target. The energy loss of the different elements in these foils was derived from the shift of the high energy edges of the spectra. The values are mainly consistent with the semi-empirical Ziegler/Biersack data. Deviations, trends and possible errors are discussed.
Ultra-thin In(OH)x Sy/Pb(OH)x Sy heterostructures were formed by the wet chemical SILAR (successive ion layer adsorption and reaction) technique. ERDA (elastic recoil detection analysis) was used for stoichiometry analysis. The heterocontacts were conditioned by joint annealing of the two layers at different low temperatures in air. The charge selectivity was demonstrated with various small area solar cell structures. The results are discussed on the base of formation of bonds between sulphide clusters and passivation of defects with hydrogen containing species in hydroxy-sulphides.
MgB2 thin films were deposited on SiC buffered Si substrates by sequential electron beam evaporation of a BMg bilayer followed by in situ annealing. The application of a SiC buffer layer enables the maximum annealing temperature of 830 °C to be reached. Transmission electron microscopy analysis confirms the growth of a nanogranular MgB2 film and the presence of a Mg2Si compound at the surface of the film. The 150200 nm thick films show a maximum zero resistance critical temperature TC0 above 37 K and a critical current density JC~106 A cm-2 at 11 K.
The content of chromium in different oxidation states in chromium-treated wood was studied with XANES (X-ray absorption near-edge structure) measurements at the Cr K absorption edge. It could be shown that wood samples treated with Cr(VI) (pine and beech) did still contain a measurable content of Cr(VI) after four weeks conditioning. If such wood samples were heat exposed for 2 h with 135 °C prior conditioning, Cr(VI) was no longer detected by XANES, indicating a complete reduction to chromium (III).
A set of compound refractive lenses (CRLs), mounted on a silicon wafer, was obtained from the Institut für Mikrostrukturtechnik Karlsruhe. The CRLs were characterized at the BAMline at the synchrotron BESSYII in Berlin. It could be demonstrated that beam diameters below 1 µm can be obtained. The beam size accepted by the lenses is (140 × 140) µm2, thus the intensity gain in the micrometer spot, including absorption, is about 15,000. It is possible to switch between different beam energies within a few minutes. First results of scans and the application of the lenses for MicroXANES (X-ray absorption near-edge structure) measurements are presented in this paper. Also, the possibility of MicroEXAFS (extended X-ray absorption fine structure) measurements is discussed.