Nitride

Nanocrystalline vanadium nitride (VN) was prepared by a direct thermal liquid-solid reaction between vanadium chloride (VCl 4 ) and sodium azide (NaN 3 ) at 600°C. Characterized by XRD, TEM, XPS and PL, the composition and morphology of the product were confirmed. The possible reaction mechanism was also discussed.

Electron-rich late-transition-metal complexes with terminal metal-nitrogen multiple bonds (M=N, MN) were considered unstable until only a few years ago. Owing to their postulated existence as transient intermediates in catalytic C À N and H À N bond-formation processes, their synthesis and study remains a highly desirable and challenging target. In this realm, the Haber-Bosch process, for which terminal ruthenium and iron nitrido units are considered active catalytic species, is of special interest. These MN structures are formed by cleavage of dinitrogen at elevated temperatures and undergo hydrogenation to ammonia at a later stage. The direct observation by Cummins and Laplaza of dinitrogen cleavage at ambient temperature in d 3 Group 6 compounds to yield the corresponding d 0 metal complexes with metal nitrido triple bonds MN (M= Mo, W) was therefore a major achievement. In contrast to these very stable nitrido compounds, terminal oxido and nitrido complexes of late transition metals are still very rare. In fact, only recently the groups of Hill and Milstein reported on d 6 palladium, platinum, and gold complexes with terminal M=O units, extending an earlier study of an iridium(V) oxido system. The presence of vacant metal p-acceptor orbitals has been identified as key to the reactivity and stability of metal-ligand multiple bonding with p-donor oxido or nitrido ligands. For most coordination geometries only d n electron configurations with n < 6 are compatible with this requirement. Complexes with a d 4 electron configuration are borderline and include the recently isolated rare examples of Group 8 metals (Fe and Ru) with terminal nitrido ligands. Examples for d 6 complexes with metal-nitrogen triple bonds have been reported for imido complexes. Herein, we report the synthesis, characterization, and reactivity of a square planar iridium complex (1, Scheme 1), which contains a terminal metal nitrido triple bond (M N). Complex 1 undergoes hydrogenation by molecular hydrogen to the corresponding amido complex 3, which could have bearing on ongoing studies toward alternative Haber-Bosch catalysts.

The electronic structure of valence and conduction bands of silicon nitride SiN layer deposited on a silicon substrate was studied using x X-ray photoelectron spectroscopy (XPS) and X-ray bremsstrahlung isochromat spectroscopy (BIS), respectively, and compared with the density of states (DOS) taken from the literature. In the isochromat spectrum measured at photon energy 5415 eV, a strong maximum at 9.7 eV and a weak extended structure in the energy range up to 200 eV above the BIS edge were observed. A theoretical calculation of extended X-ray bremsstrahlung isochromat fine structure (EXBIFS) for silicon nitride has been performed using a multiple scattering method and partial probabilities of X-ray bremsstrahlung transitions calculated for continuum states in a dipole approximation. The results have shown that the X-ray bremsstrahlung isochromat fine structure for silicon nitride appears mainly due to electron transitions to the s states localized near Si ions.

ZnTe and Cr doped ZnTe crystals have been synthesized using a solvothermal process. The characterizations by x-ray diffraction and transmission electron microscopy show that the synthesized ZnTe:Cr crystals have a cubic structure and Cr is incorporated into ZnTe. The magnetic properties of ZnTe:Cr are investigated. A hysteresis is observed in the magnetization versus magnetic field measurements below 10 K. The detailed analyses suggest that the hysteresis possibly originated from the magnetic short-range ordering of Zn 1−x Cr x Te compounds in the sample.

The ability of the oxonitride [{Ti(h 5-C 5 Me 5)(m-O)} 3 (m 3-N)] (1) to act as an organometallic ligand has been studied from both theoretical and experimental points of view. DFT calculations have allowed understanding the electronic structure of 1, and rationalizing its chemical behavior by comparison with the electronic structures of isoelectronic species [{Ti(h 5-C 5 Me 5)(m-O)} 3 (m 3-CH)] and [{Ti(h 5-C 5 Me 5)(m-NH)} 3 (m 3-N)]. Reactions of 1 with different inorganic molecules such as [Mo(CO) 3 (1,3,5-Me 3 C 6 H 3)] or AlEt 3 have confirmed the possibility of 1 to act as a tridentate or monodentate ligand to give the [{(CO) 3 Mo}(m 3-O) 3 {Ti 3 (h 5-C 5 Me 5) 3 (m 3-N)}] (2) and [{Et 3 Al}(m 3-O){(m-O) 2 Ti 3 (h 5-C 5 Me 5) 3 (m 3-N)}] (3) complexes, respectively. Surprisingly, reactions of 1 with [M(CO) 6 ] (M ¼ Cr, Mo, W) complexes led to activate the m 3-N unit in 1 to afford the new compounds [Ti 3 (h 5-C 5 Me 5) 3 (m-O) 4 {(NC)M(CO) 5 }] 2 [M ¼ Cr (4), Mo (5), W (6)]. Molecular structures of complexes 2e6 have been established by single crystal X-ray analysis.

Carbides and nitrides of d-group transition metals are classified as refractory hard material and their industrial importance has been recognized for long. In recent years, unique functionalities including catalytic function and superconductivity are discovered for this group of materials to raise serious attention of materials researchers and engineers to refractory carbides and nitrides as novel functional materials. In the present report, results of nitriding in flowing NH 3 gas at a fixed flow rate 10 l/h (≈ 167 ml/min) under heating with concentrated solar beam for VIa-group metals, Cr, Mo and W, are summarized to demonstrate favourable effect of solar beam heating towards further enhancement of nitriding power of flowing NH 3 gas compared with the situation in conventional electric furnace in which visible light components except infra-red (IR) heat wave component are absent in the reaction system.

In the present study, the type and densities of defects in AlN crystals grown on 6H-SiC seeds by the sublimation-recombination method were assessed. The positions of the defects in AlN were first identified by defect selective etching (DSE) in molten NaOH-KOH at 400 °C for 2 minutes. Etching produced pits of three different sizes: 1.77 ìm, 2.35 ìm , and 2.86 ìm. The etch pits were either aligned together forming a sub-grain boundary or randomly distributed. The smaller etch pits were either isolated or associated with larger etch pits. After preparing cross-sections of the pits by the focused ion beam (FIB) technique, transmission electron microscopy (TEM) was performed to determine which dislocation type (edge, mixed or screw) produced a specific etch pit sizes. Preliminary TEM bright field and dark field study using different zone axes and diffraction vectors indicates an edge dislocation with a Burgers vector 1/3 is associated with the smallest etch pit size.

Thermal (gas) nitridation of stainless steel alloys can yield low interfacial contact resistance (ICR), electrically conductive and corrosion-resistant nitride containing surface layers (Cr 2 N, CrN, TiN, V 2 N, VN, etc.) of interest for fuel cells, batteries, and sensors. This paper presents results of proton exchange membrane (PEM) single-cell fuel cell studies of stamped and pre-oxidized/nitrided developmental Fe-20Cr-4V weight percent (wt.%) and commercial type 2205 stainless steel alloy foils. The single-cell fuel cell behavior of the stamped and pre-oxidized/nitrided material was compared to as-stamped (no surface treatment) 904L, 2205, and Fe-20Cr-4V stainless steel alloy foils and machined graphite of similar flow field design. The best fuel cell behavior among the alloys was exhibited by the pre-oxidized/nitrided Fe-20Cr-4V, which exhibited ∼5-20% better peak power output than untreated Fe-20Cr-4V, 2205, and 904L metal stampings. Durability was assessed for pre-oxidized/nitrided Fe-20Cr-4V, 904L metal, and graphite plates by 1000+ h of cyclic single-cell fuel cell testing. All three materials showed good durability with no significant degradation in cell power output. Post-test analysis indicated no metal ion contamination of the membrane electrode assemblies (MEAs) occurred with the pre-oxidized and nitrided Fe-20Cr-4V or graphite plates, and only a minor amount of contamination with the 904L plates.

This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMC's) by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC surfaces, of interest because of the presence of different types of surface resonances (SR's) on them and because of their technological importance in growth processes. Also, TM compounds have shown potential in catalysis applications. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, δ-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH2, and NH3. Trends in adsorption strength are explained in terms of surface electronic factors, by correlating the calculated adsorption energy values with the calculated surface electronic structures. The results are rationalized with use of a concerted-coupling model (CCM), which has previously been applied succesfully to the description of adsorption on TiC(111) and TiN(111) surfaces [Solid State Commun. 141, 48 (2007)]. First, the clean TMC(111) surfaces are characterized by calculating surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOS's). Detailed comparisons between surface and bulk DOS's reveal the existence of transition-metal localized SR's (TMSR's) in the pseudogap and of several C-localized SR's (CSR's) in the upper valence band on all considered TMC surfaces. The spatial extent and the dangling bond nature of these SR's are supported by real-space analyses of the calculated Kohn-Sham wave functions. Then, atomic and molecular adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOS's reveals a presence of both adsorbate-TMSR and adsorbate-CSR's interactions, of varying strengths depending on the surface and the adsorbate. These variations are correlated to the variations in adsorption energies. The results are used to generalize the content and applications of the previously proposed CCM to this larger class of substrates and adsorbates. Implications for other classes of materials, for catalysis, and for other surface processes are discussed.

It is difficult in 2013 to deny that the production, consumption, and storage of energy are among the top technological challenges facing our world. As the demand for fossil fuels increases, the call for alternative, more efficient and clean sources of energy becomes loud and clear. While many new technologies are under development to address this need, deficiencies in materials properties and other problems have hindered the successful replacement of fossil fuel burning energy sources. Currently deployed technologies often rely on heat-driven engines. These engines are inherently limited in efficiency by the 2 nd law of thermodynamics via the Carnot limit, which states that the maximum efficiency achievable by a heat-driven engine is a function of the operating temperature of the engine, as well as the temperature of the environment in which it operates, Figure 1.1.

Nitrides of refractory metals are investigated as diffusion barriers for Cu metallization. The composition, thermal stability and inter diffusion in layered systems are characterized by depth profile analysis. For the quantification of depth profiles determination of sensitivity factors is essential. For nitrogen and other light elements matrix specific standards are often not available and compound standards are used for calibration. We have investigated the systems Ta-N and Ta-Si-N and for comparison Cr-N by means of Auger electron spectrometry (AES) and glow discharge optical emission spectrometry (GDOES). A non-linear calibration curve for the N=Cr intensity ratio was observed with GDOES in the Cr-N-system, probably caused by selfabsorption of the Cr line.

The magnetic and structural properties of FINEMET [Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 wt%] amorphous powder were investigated after nitrification and mechanical milling. Fe-based amorphous powder were nitrified and crystallized simultaneously at 550°C using by ammonia (NH 3 ) gas. Nitrified powder exhibited iron nitride phase such as c 0 -Fe 4 N, Fe 3 N, and a 00 -Fe 16 N 2 . Nitrified particles were more brittle than raw particles. As a result, nanometer-sized nitride powder was fabricated by high-energy ball milling method. The saturation magnetization (M s ) and coercivity (H c ) of nitrified powder were increased due to nitride phase.

This paper reports on design, fabrication and experimental testing of a new class of two-port stacked piezoelectric aluminum nitride contour-mode micromechanical resonators that can be used for RF filtering and timing applications. This novel design consists of two layers of thin film AlN stacked on top of each other and excited in contour mode shapes using the d 31 piezoelectric coefficient. Main feature of this design is the ability to reduce capacitive parasitic feedthrough between input and output signals while maintaining strong electromechanical coupling. For example, these piezoelectric contour-mode resonators show a quality factor of 1,700 in air and a motional resistances as low as 175 Ω at a frequency of 82.8 MHz. The input to output capacitance has been limited to values below 80 f F, therefore simplifying signal detection even at high frequencies.

A long-term hydrological and water chemistry research was conducted in three experimental microbasins differing in land cover: (1) a purely agricultural fertilized microbasin, (2) a forested microbasin dominated by Carpinus betulus (European hornbeam), and (3) a forested microbasin dominated by Picea abies (L.) (Norway spruce). The dissolved inorganic nitrogen (DIN: NH 4

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In the present study, hard TiSiN coating compounds with different Si content have been deposited by the magnetron sputtering technique. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) have been employed to investigate the effects of Si addition on the composition, structure and phase development of the cubic NaCl-type structure. To get some insight on these changes, X-ray absorption spectra have been measured at the Ti and Si K-edges in fluorescence yield mode. The collected data showed that the interaction between Ti and Si was weak and the formation of a-Si 3 N 4 can be assumed. Hardness measurements were also consistent with the formation of hard nanocomposite films. A maximum hardness of about 36 GPa was obtained for the sample with 11 at. % Si.

Lithium nitride hydride, Li 4 NH, was synthesised from lithium nitride and lithium hydride over minute timescales, using microwave synthesis methods in the solid state for the first time. The structure of the microwave-synthesised powders was confirmed by powder X-ray diffraction [tetragonal space group I4 1 /a; a = 4.8864(1) Å, c = 9.9183(2) Å] and the nitride hydride reacts with moist air under ambient conditions to produce lithium hydroxide and subsequently lithium carbonate. Li 4 NH undergoes no dehydrogenation or decomposition [under Ar (g) ] below 773 K. A tetragonal-cubic phase transition, however, occurs for the compound at ca. 770 K. The new high temperature (HT) phase adopts an anti-fluorite structure (space group Fm 3 m; a = 4.9462(3) Å) with N 3− and H − ions disordered on the 4a sites. Thermal treatment of Li 4 NH under nitrogen yields a stoichiometric mixture of lithium nitride and lithium imide (Li 3 N and Li 2 NH respectively).

We analyze the ellipticity of the standard k · p wurtzite model for the symmetrized and the Burt–Foreman operator ordering. We find that for certain situations the symmetrized Hamiltonian is unstable, leads to unplausible results and can cause spurious solutions. We show that the operator ordering in wurtzite must be completely asymmetric to be stable. The asymmetric operator ordering is elliptic and consequently no spurious solutions are obtained. Therefore we recommend the use of a complete asymmetric operator ordering for nitride device simulation.

ZnTe and Cr doped ZnTe crystals have been synthesized using a solvothermal process. The characterizations by x-ray diffraction and transmission electron microscopy show that the synthesized ZnTe:Cr crystals have a cubic structure and Cr is incorporated into ZnTe. The magnetic properties of ZnTe:Cr are investigated. A hysteresis is observed in the magnetization versus magnetic field measurements below 10 K. The detailed analyses suggest that the hysteresis possibly originated from the magnetic short-range ordering of Zn 1−x Cr x Te compounds in the sample.

Growth orientation and type of internal structures are both observed to change abruptly as a function of growth temperature in catalyst free growth of gallium nitride nanowires. In the present work, corresponding temperature-dependent changes in the growth matrix substrate that can affect the availability of nucleation sites and influence the reactivity of constituent adatom materials in catalyst-free nanowire growth are investigated. The influence of Ga vapor pressure and an abrupt change in the availability of single versus molecular adatom constituents is identified as a possible controlling parameter.

In this article we investigate the effect of relative humidity on dielectric charging/discharging processes in electrostatically actuated MEMS devices. The assessment procedure is based on surface potential measurements using Kelvin Probe Force Microscopy (KPFM) and it targets in this specific work PECVD silicon nitride films in view of application in electrostatic capacitive RF MEMS switches. Charges have been injected through the AFM tip and the induced surface potential has been measured under different relative humidity levels. The impact of the charge injection duration and the bias level as well as bias polarity applied during the charge injection step, have been explored. Finally, the effect of the dielectric film thickness under different relative humidity levels has been assessed through depositing SiN films with different thicknesses.

The electronic structure of nanolaminate Ti 2 AlN and TiN thin films has been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured Ti L, N K, Al L 1 and Al L 2,3 emission spectra are compared with calculated spectra using ab initio density-functional theory including dipole transition matrix elements. Three different types of bond regions are identified; a relatively weak Ti 3d -Al 3p bonding between -1 and -2 eV below the Fermi level, and Ti 3d -N 2p and Ti 3d -N 2s bonding which are deeper in energy observed at -4.8 eV and -15 eV below the Fermi level, respectively. A strongly modified spectral shape of 3s states of Al L 2,3 emission from Ti 2 AlN in comparison to pure Al metal is found, which reflects the Ti 3d -Al 3p hybridization observed in the Al L 1 emission. The differences between the electronic and crystal structures of Ti 2 AlN and TiN are discussed in relation to the intercalated Al layers of the former compound and the change of the materials properties in comparison to the isostructural carbides.

Niobium nitride is used in different applications due to its mechanical, tribological, electrical, and optical properties. This paper is a study concerning the influence of the deposition temperature on the mechanical characteristics of niobium nitride thin films at nanoscale . The films were deposited on silicon substrates by direct current magnetron sputtering at different temperatures. The deposition was done at room temperature, at 200 and 400 °C respectively. Atomic force microscopy investigations were performed to determine the mechanical properties of the niobium nitride films. The results pointed out that both the nanohardness and modulus of elasticity are decreasing with the increase in temperature up to 200 °C after which they are increasing when the temperature is increased up to 400 °C. Key words: niobium nitride, magnetron sputtering, nanoindentation, nanohardness, modulus of elasticity.

Group III–V dilute nitrides, III-N x −V1−x (with x up to 0.10) have exhibited many unusual properties as compared to conventional semiconductor alloys. Here we review studies on the synthesis of group III–V dilute nitrides by a highly nonequilibrium method: the combination of ion implantation, pulsed-laser melting (PLM), and rapid thermal annealing (RTA). Using this method, the formation of a wide variety of III−N x −V1−x alloys including GaN x As1−x , InN x P1−x , Al y Ga1−y N x As1−x , and GaN x As1−x−y P y has been synthesized and their optical properties investigated. In particular, ion implantation followed by PLM has been successful in forming thermally stable thin films of GaN x As1−x with x as high as 0.016 and structural and optical properties comparable to films grown by epitaxial deposition techniques with similar substitutional N content. Using the implantation, PLM technique group II–VI dilute oxide (II−O−VI) semiconductors, a direct analogue of the III–V diluted nitrides, have also been formed. In Zn1-x Mn x Te, where the O level lies below the conduction band edge, it was demonstrated that incorporation of a small amount of oxygen leads to the formation of a narrow, oxygen-derived band of extended states located well below the conduction band edge of the ZnMnTe matrix. The three absorption edges of this material (̃0.73, 1.83, and 2.56 eV) cover the entire solar spectrum providing a material envisioned for the multiband, single junction, high-efficiency photovoltaic devices.

Lithium nitride hydride, Li 4 NH, was synthesised from lithium nitride and lithium hydride over minute timescales, using microwave synthesis methods in the solid state for the first time. The structure of the microwave-synthesised powders was confirmed by powder X-ray diffraction [tetragonal space group I4 1 /a; a = 4.8864(1) Å, c = 9.9183(2) Å] and the nitride hydride reacts with moist air under ambient conditions to produce lithium hydroxide and subsequently lithium carbonate. Li 4 NH undergoes no dehydrogenation or decomposition [under Ar (g) ] below 773 K. A tetragonal-cubic phase transition, however, occurs for the compound at ca. 770 K. The new high temperature (HT) phase adopts an anti-fluorite structure (space group Fm 3 m; a = 4.9462(3) Å) with N 3− and H − ions disordered on the 4a sites. Thermal treatment of Li 4 NH under nitrogen yields a stoichiometric mixture of lithium nitride and lithium imide (Li 3 N and Li 2 NH respectively).

Purpose: Comprehensive structure and properties investigation results of the multilayer, multi-component, gradient PVD and CVD coatings developed on the Si3N4 nitride tool ceramics substrate are presented in the paper. Design/methodology/approach: The detailed results are presented of examinations carried out on the transmission and scanning electron microscopes, as well as of the mechanical properties and tribological tests of the investigated coatings. Findings: The research carried out proved that depositing the hard, anti wear, multilayer coatings based on the Al2O3 and TiN layers onto the Si3N4 nitride tool ceramics with the PVD method results in obtaining better functional properties like extension of the cutting tool life, than in case of the uncoated nitride ceramics or coated with the PVD coatings and some CVD ones. Research limitations/implications: Pro-ecological dry cutting processes without the use of the cutting fluids and in the „Near-Net-Shape” technology. Originalit...

In this study, α-Si3N4 powder was produced by carbothermal reduction and nitridation (CRN) of quartz from Can-Canakkale. Carbon with a specific surface area of 110 m2g−1 and quartz powders were mixed then the powder mix was placed in an alumina tube furnace and reacted in between 1300-1500°C for 4 hours under nitrogen flow. The quartz powder was carbothermally reduced and nitrided to form silicon nitride powders. XRD results showed that the reaction product was mainly α-Si3N4 and contained some β-Si3N4 and residual quartz. In order to reduce amount of unreacted quartz, the raw materials mixture was grinded either with carbon black or with no carbon. After CRN reactions of separate grinded quartz powders with carbon, residual quartz was disappeared, reaction temperature was decreased and α-Si3N4 rate was increased. Hence, a better mixing of carbon and fine silica enhanced the α phase formation. SEM images and XRD pattern showed that sub micron particles (0.6–0.87m), high α-phase content Si3N4 powders can be produced at 1450°C for 4 h in flowing nitrogen gas during the CRN process.

In this article we investigate the effect of relative humidity on dielectric charging/discharging processes in electrostatically actuated MEMS devices. The assessment procedure is based on surface potential measurements using Kelvin Probe Force Microscopy (KPFM) and it targets in this specific work PECVD silicon nitride films in view of application in electrostatic capacitive RF MEMS switches. Charges have been injected through the AFM tip and the induced surface potential has been measured under different relative humidity levels. The impact of the charge injection duration and the bias level as well as bias polarity applied during the charge injection step, have been explored. Finally, the effect of the dielectric film thickness under different relative humidity levels has been assessed through depositing SiN films with different thicknesses.

In this work, we demonstrate the use of X-ray diffraction for analyzing structural imperfections in a-plane GaN grown on r-plane sapphire. Although there are only two (hh0) planes accessible under symmetric diffraction, there are an adequate number of diffraction planes accessible under the quasi-symmetric configuration to enable analysis of rocking curves that are not influenced by basal-plane stacking faults. By measuring diffraction profiles for a series of symmetric and asymmetric crystal planes, the broadening terms were separated using extrapolation methods based on their geometric dependence. Individual broadening factors can then be correlated to the relative contribution of different structural defects, including threading dislocations, lateral coherence length, and basal plane stacking faults.

The photoluminescence of m-plane GaN grown on mplane sapphire substrate by MOCVD is reported. The defect related emissions with temperature and excitation power dependence are detailed. In addition to the near band-edge emission (at ~3.472 eV), two major defectrelated bands (D1~3.43 eV and D2~3.34 eV) are dominant in the low temperature spectra. The D1 emission exhibits thermal quenching with two activation energies (8 and 30 meV), similar to that of a-plane GaN grown on r-plane sapphire. The D2 band was found to consist of a complex overlap of multiple emissions. By fitting the asymmetric band using multiple Gaussian functions, the extracted emission at ~3.34 eV was shown to have thermal activation energy ~17-20 meV. This emission exhibits different behavior from that of D2 in a-plane GaN in temperature and excitation power dependency, indicating the possible involvement of different defects due to the changes in growth characteristics.

Carbon nitride films with b-C N crystals of 200 nm grain size were grown on Si (1 0 0) substrates using magnetron sputtering. 3 4 These films were characterized by transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Carbon nitride films had low surface roughness. Maximum NyC ratio of 0.5 was achieved in the films. Chemical bonds of sp, sp and sp coexisted in the films. The fraction of each bond was related to the deposition conditions. The resistivities 2 3 of the films were measured, which ranged from 1=10 to 1=10 V cm. The measured resistivity results indicated that the carbon 3 7 nitride films had semiconductive properties. The resistivity largely depended on the sp ysp ratio. Effects of N fraction, target 3 2 2 current and substrate bias were investigated. All these deposition parameters had influence on the chemical bonds of the films, and on the resistivities too. High sp ysp ratio resulted in high resistivity.

Microwave-Assisted Surface Synthesis of a Boron-Carbon-Nitrogen Foam and its Desorption Enthalpy The modifi cation of microporous carbon foam with boron and nitrogen through a facile microwave chemical treatment are reported. The resulting surfaces of the foam exhibit distinct B-N and carbon domains based on chemical and microscopic analysis, in keeping with theoretical predictions. The resultant materials are shown to exhibit exceptionally high methanol desorption enthalpy and thermal stability in comparison to untreated carbon foam and consequently are suggested as candidate materials for sorption cooling and thermal storage applications using methanol as the adsorbate.

Cleaning of GaN by argon sputtering and subsequent annealing introduces metallic gallium on the GaN surface. Once formed, this metallic gallium can be difficult to remove. It has a strong influence on the Fermi level position in the band gap and poses a problem for subsequent epitaxial growth on the surface. We present a method of removing metallic gallium from

ABSTRACTTransmission electron microscopy was used to study defects in lateral epitaxial layers of GaN which were overgrown on a template of a-plane (1120) GaN grown on (1102) r-plane Al2O3. A high density of basal stacking faults is formed in these layers because the c-planes of wurtzite structure are arranged along the growth direction. Density of these faults is decreasing at least by two orders of magnitude lower in the wings compared to the seed areas. Prismatic stacking faults and threading dislocations are also observed, but their densities drastically decrease in the wings. The wings grow with opposite polarities and the Ga-wing width is at least 6 times larger than N-wing and coalescence is rather difficult. Some tilt and twist was detected using Large Angle Convergent Beam Electron Diffraction.

Silicon oxide is a promising material for silicon thin-film solar cells. As a doped layer it shows low parasitic absorption while as an intrinsic layer it can be used as a high band gap absorber in multijunction solar cells. Whereas doped silicon oxide layers prepared with CO 2 are widely investigated, intrinsic layers and the use of N 2 O as a source gas for oxygen incorporation in silicon thin-film solar cells have not received much attention yet. Therefore we present the optical and electrical properties of doped and intrinsic silicon oxinitride layers at varying N 2 O flow as well as their performance in single cells. We found that p-doped amorphous silicon oxinitride layers enhance the short circuit current and the open circuit voltage of amorphous silicon single cells while the fill factor is reduced due to higher series resistance. When N 2 O is added to the intrinsic layer of amorphous silicon single cells the cell performance deteriorates drastically which is attributed to increased defect density.

The electronic structure of nanolaminate Ti 2 AlN and TiN thin films has been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured Ti L 2,3 , N K, Al L 1 , and Al L 2,3 emission spectra are compared with calculated spectra using ab initio density-functional theory including dipole transition-matrix elements. Three different types of bond regions are identified; a relatively weak Ti 3d-Al 3p bonding between −1 and −2 eV below the Fermi level, and Ti 3d-N 2p and Ti 3d-N 2s bondings which are deeper in energy observed at −4.8 eV and −15 eV below the Fermi level, respectively. A strongly modified spectral shape of 3s states of Al L 2,3 emission from Ti 2 AlN in comparison with pure Al metal is found, which reflects the Ti 3d-Al 3p hybridization observed in the Al L 1 emission. The differences between the electronic and crystal structures of Ti 2 AlN and TiN are discussed in relation to the intercalated Al layers of the former compound and the change of the materials properties in comparison with the isostructural carbides.