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In this study we investigate the performance of Cu(In1-x,Ga-x)Se-2/Zn(O1-z,S-z) solar cells by changing the gallium content of the absorber layer in steps from CuInSe2 to CuGaSe2 and at each step vary the sulfur content of the Zn(O,S) buffer layer. By incorporating more or less sulfur into the Zn(O,S) buffer layer it is possible to change its morphology and band gap energy. Surprisingly, the best solar cells with Zn(O,S) buffer layers in this study are found for close to or the same Zn(O,S) buffer layer composition for all absorber Ga compositions. In comparison to their CdS references the best solar cells with Zn(O,S) buffer layers have slightly lower open circuit voltage, V-oc, lower fill factor, FF, and higher short circuit current density, J(sc), which result in comparable or slightly lower conversion efficiencies. The exception to this trend is the CuGaSe2 solar cells, where the best devices with Zn(O,S) have substantially lowered efficiency compared with the CdS reference, because of lower V-oc, FF and J(sc). X-ray photon spectroscopy and X-ray diffraction measurements show that the best Zn(O,S) buffer layers have similar properties independent of the Ga content. In addition, energy dispersive spectroscopy scans in a transmission electron microscope show evidence of lateral variations in the Zn(O,S) buffer layer composition at the absorber/buffer layer interface. Finally, a hypothesis based on the results of the buffer layer analysis is suggested in order to explain the solar cell parameters.

The effect of atomic layer deposition temperature of Zn1-xMgxO buffer layers for Cu(In,Ga)Se-2 (CIGS) based solar cell devices is evaluated. The Zn1-xMgxO films are grown using diethyl zinc, bis-cyclopentadienyl magnesium and water as precursors in a temperature range of 105 to 180 C High efficiency devices are produced in the region front 105 up to 135 degrees C. At a Zn1-xMgxO deposition temperature of 120 C, a maximum cell efficiency of 15.5% is reached by using a Zn1-xMgxO layer with an x-value of 0.2 and a thickness of 140 inn. A significant drop in cell efficiency due to large losses in open circuit voltage and fill factor is observed for devices grown at temperatures above 150 C. No differences in chemical composition, structure and morphology of the samples are observed, except for the samples prepared at 105 and 120 C that show elemental selenium present at the buffer/absorber interface. The selenium at the interface does not lead to major degradation of the,solar cell device efficiency. Instead, a decrease in Zn1-xMgxO resistivity by more than one order of magnitude at growth temperatures above 150 C may explain the degradation in solar cell performance. From energy filtered transmission electron microscopy, the width of the CIGS/Zn1-xMgxO chemical interface is found to be thinner than 10 not without any areas of depletion for Cu, Se, Zn and O.

One of the most challenging issues in the characterization of magnetic materials is to obtain a quantitative analysis on the nanometer scale. Here we describe how electron magnetic circular dichroism (EMCD) measurements using the transmission electron microscope can be used for that purpose, utilizing reciprocal space maps. Applying the EMCD sum rules, an orbital to spin moment ratio of mL/mS=0.08±0.01 is obtained for Fe, which is consistent with the commonly accepted value. Hence, we establish EMCD as a quantitative element-specific technique for magnetic studies, using a widely available instrument with superior spatial resolution.

Films of iridium-tantalum oxide and iridium oxide have been prepared by sputtering and studied regarding their structure and electrochemical properties. X-ray diffraction and transmission electron microscopy showed an average grain size of 3-4 nm for both films. Point energy dispersive X-ray spectrometry showed an inhomogeneous distribution of iridium and tantalum indicating that the iridium-tantalum oxide may be a mixture of small IrO2 and Ta2O5 grains, which is consistent with the determined composition IrTa1.4O5.6. X-ray photoelectron spectroscopy gave valuable information on the stabilization process of the as-deposited films involving an uptake of oxygen, and on a coloration mechanism only including protons.

Nanoelectrodes were fabricated combining photolithography, electron beam lithography and focused ion beam milling allowing for large scale integration and nanoengineering of the electrode properties. The structure determination by transmission and scanning electron microscopy showed a highly reproducible gap width. The atomic scale electrode structure was characterized using scanning and transmission electron microscopy. The nanogap resistances were found to be the highest hitherto reported for nanogaps, namely in the 300–1300 TΩ range. Gold nanoparticles were trapped by ac dielectrophoresis, and the electrodes were shown to be stable enough to endure empty gap voltages as high as 5 V as well as currents high enough to induce fusing of trapped nanoparticles.

We report the structural and tribological characterization of nanostructured CNx thin films produced by the deposition of a supersonic carbon cluster beam assisted by nitrogen ion bombardment. The influence of the deposition parameters on the chemical composition and structure of the films has been systematically studied by X-ray photoelectron spectroscopy, elastic recoil detection analysis, transmission electron microscopy and atomic force microscopy. Depending on the deposition parameters, the films show a structure ranging from amorphous to disordered graphitic with interlinked planes. Nitrogen content depends on the nitrogen ion kinetic energy. The films have a very low density with a high surface roughness. Friction measurements at the nanoscale show a correlation between nitrogen content and mechanical properties of the system.

Carbide derived carbons (CDCs) have been synthesized from VC, WC, TaC, NbC, HfC and ZrC at T = 1000 °C, and from TiC at T = 700-1200 °C via a chlorination reaction. The CDCs have been studied by means of high resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS). These studies show that the structures of CDCs are strongly dependent upon the nature of the starting carbide and the synthesis temperature. The structures range from very disordered nanoporous carbon, consisting of randomly curved graphene layers, to compact spherical entities of compactly packed graphitic layers. EELS studies of carbon core-loss spectra show that the relative sp2 content in these carbons varies between 83% and 98%. The low-loss part of the EEL spectra shows that the positions of the π-plasmons and the bulk plasmons are more dependent on the carbide precursor, than the synthesis temperature. The densities of the CDC particles have been estimated using the bulk plasmon positions as well as the sp3 content determined from the C-K edge spectra. The densities calculated from sp3 are close to the pycnometric ones, while the densities calculated from bulk plasmon positions are lower and reflects the nanostructure of CDCs.

The drill crown of a rock drill is made of steel and equipped with WC/Co cemented carbide buttons (or inserts) of different geometries. These rock drill button are exposed to a large number of high load impacts into the rock. The complex and strongly shifting properties of rock minerals lead to a complex mixture of wear mechanisms. These wear mechanisms have recently been mapped by the present authors, and are divided into five classes of deterioration and five classes of material removal mechanisms. In this paper, two important deterioration mechanisms are studied in detail, namely the binder phase degradation and the rock intermixing. Transmission electron microscopy (TEM) has been employed for these high resolution studies. However, rock intermixture and huge internal stresses in the buttons lead to severe difficulties in preparing samples. Therefore, a focused ion beam-instrument (FIB) has been used to cut cross-section samples in the outermost surface on rock drill buttons. These have been investigated in the TEM by EDS, EFTEM, and STEM. Buttons from two rock drills of different history were selected for this investigation. One was used to drill 18 m in a hard rock type (quartzitic granite) and the other to drill 20 m in a much softer rock type (magnetite). Only selected regions of the outermost WC grain layers, which are in a steady state wear mode, were investigated. The crystallographic structure of the Co binder phase was investigated in both buttons, and it was represented mainly by the hcp-Co, but also small extent of fcc-Co. This is suggested to be a result of the mechanical fatigue, following one of two suggested Co-phase transformation series. The rock covers and intermixed zones formed were analysed in detail. The large part of the rock cover was found to be amorphous, containing rock and WC fragments. Adjacent to the WC grains, the rock cover was often found to have a porous structure, where the pores were surrounded by crystalline Co-particles adjac

Materials from the Stellite family of Co-based alloys are commonly used as low friction, galling resistant materials in high load dry sliding contact applications. In the present investigation, the surface region of a Co-based material (Stellite 21) exposed to self-mated high load dry sliding at room temperature has been analysed in detail. During sliding, an approximately 30 nm thick Co-enriched tribofilm is created. It exhibits low friction properties and a high galling resistance. The transformation from an face-centred-cubic structure to easily sheared hexagonal-closed-packed basal planes in the tribofilm combined with the high load carrying capacity of the underlying deformation hardened zone is suggested to explain the excellent low friction properties and galling resistance of this material.

Carbon microfibers were deposited using laser-assisted chemical vapor deposition at atmospheric and sub-atmospheric pressures. Precursor pressures and incident laser powers were varied. Fibers were cast in acrylic resin and polished to allow nanoindentation of the cross sections. Cross-sectional roughness was examined by optical profilometry. A radial change in mechanical properties was observed. The local elastic modulus (Youngs modulus) and hardness for the edge and core regions are reported. These mechanical properties were investigated with respect to deposition parameters and corresponding fiber microstructure.