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The work is devoted to the study of recrystallization occurring during short-term annealing of 100 nm thick polycrystalline films of copper and silver. It is found that in copper films deposited by the method of thermal evaporation onto a substrate at room temperature, a bimodal crystallite size distribution with maxima at 15 and 35 nm is observed. The bimodal distribution in copper films is preserved during annealing, which leads to a shift of both peaks of the crystallite size distribution histograms to the larger sizes region. In contrast to Cu, even in as-deposited Ag films, besides the nanosized fraction, micron-sized crystallites are present. Apparently, these grains are formed due to the phenomenon of self-annealing and weakly evolve during heating owing to grain growth stagnation. The nanosized fraction in as-deposited Ag films is represented by crystallites with the most probable size of 25 nm, which increases to 50 nm as a result of short-term annealing at the temperature of 250 °C. The grain-boundary diffusion coefficient was determined, which is more than 10−18 m2/s for both films of metals. The obtained value indicates a multiple intensification of self-diffusion processes in films, the thickness of which allows us to refer them to macroscopic sample. • Recrystallization of Cu and Ag nanocrystalline films has been studied. • Acceleration of diffusion rate in nanocrystalline films of metals is shown. • It is found that as-deposited Cu films have a bimodal crystallite size distribution. • A bimodal distribution in copper films is preserved during their annealing. • Low thermal stability of silver films is explained by their layered structure. [ABSTRACT FROM AUTHOR]

• Crystallization of GaN:Si,C was carried out to examine the role of C in n-type GaN crystals. • Intentional incorporation of high concentrations of Si and C is possible. • Raman spectroscopy shows low-frequency modes in co-doped crystals, suggesting SiC precipitates. • YL peak's position and intensity vary with dopant specifics, hinting at Si-C complexes or V Ga. In this work co-doping with silicon and carbon in gallium nitride grown by halide vapor phase epitaxy was performed. Native seeds of high structural quality with bowing radii of (0 0 0 1) crystallographic planes higher than 15 m and threading dislocation density on the order of 5 × 104 cm−3 were used. The crystallized material was examined in terms of structural, optical, and electrical properties. For this purpose different characterization methods: X-ray diffraction, Raman spectroscopy, low-temperature photoluminescence, and Hall measurements, were applied. The physical properties of samples doped only with silicon and co-doped with carbon were analyzed and compared. However, during the crystallization process, due to high amount of Si and C, clusters of silicon carbide were unintentionally formed. The formation of these SiC clusters had an impact on the properties of the GaN crystals that were being studied. The research provides an initial insight into the complex studies of co-doping gallium nitride crystals. The results of this paper give us groundwork for more in-depth exploration of this topic. [ABSTRACT FROM AUTHOR]

Advanced Substrates consist of a thin GaN layer bonded to a carrier wafer. The layer is separated from starting material by Smart Cut™ technology. GaN on sapphire Advanced Substrates were successfully used as seeds for HVPE-GaN growth. Unintentionally doped and silicon-doped thick GaN layers were crystallized. The results were compared to HVPE-GaN grown on standard MOCVD-GaN/sapphire templates. Free-standing HVPE-GaN with high free carrier concentration was obtained. A laser diode was built on the n-type doped HVPE-GaN grown on an Advanced Substrate. [ABSTRACT FROM AUTHOR]

One of the main advantages of the hydride vapor phase epitaxy (HVPE) method for crystallizing bulk gallium nitride is the crystallization of GaN with a relatively high growth rate (>100 μm/h). In this paper various growth rates in the c -direction during crystallization of GaN by HVPE on ammonothermally grown GaN crystals are determined and examined. The influence of the highest (380 μm/h) and the lowest (40 μm/h) growth rate on the structural quality and purity of the HVPE-GaN crystals is analyzed. The optimal macroscopically stable growth rate (without cracks and pits) and the way of achieving it are presented and discussed. [ABSTRACT FROM AUTHOR]

We present an investigation of the magnetic, thermodynamic, and electric transport properties and the electronic structure of the strongly correlated compounds Ce3Rh4Sn13 and Ce3Co4Sn13. The main goal of this report is to compare the physical properties of both compounds and to explain the abnormal electrical resistivity behavior in Ce3Co4Sn13 above ∼160 K, which has not been observed in Ce3Rh4Sn13. We suggest that a possible local distortion of the trigonal Sn2 prisms around Co occurs in Ce3Co4Sn13 below ∼160 K, which could change the electronic structure near the Fermi level and, as a consequence, explain the metallic behavior visible in the resistivity above this temperature. We determined experimentally the hybridization energy Δ between the f-electron and conduction-electron states for both compounds and its influence on the different ρ (T) behaviors under pressure. The complimentary experimental data allowed us to explain the semimetallic properties of both compounds and the transition between semimetallic and metallic behavior in Ce3Co4Sn13, which is not observed for Ce3Rh4Sn13. [ABSTRACT FROM AUTHOR]

The magnetic and transport properties of Fe2VGa doped with metal M (M = Rh and Ti) have been obtained from the analysis of ac magnetic susceptibility χac, magnetization M vs magnetic field, specific heat C, and electrical resistivity ρ. The results provide evidence for the formation of a spin-glass state at Tf~6 K, resulting from an atomic disorder. Short-range magnetic correlations manifested at T>Tf as anomalies of the low magnetic field ac magnetic susceptibility and specific-heat data are believed to be related to a Griffiths-like phase in Fe2V1-xMxGa at x

Manganese diffusion in ion implanted gallium nitride crystals was investigated. The ions were implanted into a sample composed of a GaN layer grown using halide vapor phase epitaxy on an ammonothermal gallium nitride substrate. The sample was polished into an atomically flat state prior to the implantation. Manganese ions were implanted into the surface of a (0001) plane (also known as the c-plane) using the beam energy of 230 keV and ion fluence of 5E15 cm−2. The beam was tilted relative to the sample's normal to prevent channeling. After the implantation, ultra-high pressure annealing method was used to both, remove the post-implantation damage and induce the diffusion of implanted Mn ions. Manganese profiles were analyzed along the c-direction using secondary ion mass spectrometry after 5 and 30 h of annealing in temperatures ranging from 1473 K to 1753 K. Two diffusion mechanisms were observed. The diffusion parameters, activation energy and temperature-independent diffusion coefficients, are presented for each mechanism. Additionally, the structural quality of the samples is assessed after 5 and 30-hour annealing in the aforementioned temperature range through the means of X-ray diffractometry. • Mn-implanted HVPE-GaN was annealed in ultra-high-pressure conditions. • Two Mn diffusion mechanisms were identified & described. • Models for the aforementioned diffusion mechanisms are proposed. • X-ray diffractometry presents a high degree of recovery of the crystal lattice. [ABSTRACT FROM AUTHOR]

Results of gallium nitride crystallization on native seeds by Hydride Vapor Phase Epitaxy method are described. The seeds are high quality ammonothermal GaN crystals. Properties of unintentionally doped HVPE-GaN are briefly presented. A review on doping with donors and acceptors is prepared. Intentional incorporation of silicon or germanium is proposed in order to grow highly conductive HVPE-GaN. Carbon, iron, or manganese was introduced to increase the resistivity of crystallized material. GaN samples with different dopants are described in terms of their structural, optical, and electrical properties. [ABSTRACT FROM AUTHOR]

Crystallization by hydride vapor phase epitaxy method of gallium nitride single crystals doped with germanium and properties of the obtained material are described in this paper. Growth was performed in hydrogen and nitrogen carrier gas. The results were studied and compared. Influence of different flows of germanium tetrachloride, precursor of germanium, on the grown crystals was investigated. Ammonothermal GaN substrates were used as seeds for crystallization. Structural, electrical, and optical properties of HVPE-GaN doped with germanium are presented and discussed in detail. They were compared to properties of HVPE-GaN doped with silicon and also grown on native seeds of high quality. [ABSTRACT FROM AUTHOR]

Gallium nitride crystals were grown by hydride vapor phase epitaxy using solid iron as a source of dopants. Three crystal growth processes were performed at constant HCl flow over the solid iron and with different gallium chloride flows. High structural quality ammonothermal GaN was used as seed material. No yellow luminescence and only weak near band edge luminescence were visible in all grown crystals. A sharp peak was observed at 1.298 eV. This was shown before as an intrinsic transition of Fe impurity in GaN. The grown crystals were highly resistive at room temperature. High-temperature Hall effect measurements revealed n-type conductivity with activation energy equal to 1.8 eV. Secondary ion mass spectrometry indicated the presence of manganese in all three samples. The concentration of manganese was always higher than concentration of iron in the doped GaN. [ABSTRACT FROM AUTHOR]

Results of growth of high structural quality gallium nitride single crystals doped with silicon are described in this paper. Dichlorosilane was used as precursor of silicon in the hydride vapor phase epitaxy method. Crystallization runs with different flows of dichlorosilane were performed and compared. One-inch free-standing HVPE-GaN crystals of high structural quality and high purity, previously grown on ammonothermal GaN substrates, were used as seeds. Structural, electrical, and optical properties of HVPE-GaN doped with silicon are presented and discussed in detail. A laser diode built on the homoepitaxially grown GaN is demonstrated. [ABSTRACT FROM AUTHOR]

Investigation of source of stress in HVPE-GaN grown in c-direction on native seeds is reported. The study was based on experimental results. Ammonothermally grown GaN seed was used for growth of a thick HVPE-GaN layer in the c-direction. Deterioration of quality of the HVPE-GaN layer appeared. Numerical simulations were used for determining and examining radial, tangential, and axial stress distributions in the grown GaN crystal and the seed. The maximum equivalent stress (von Mises stress) was calculated and analyzed. It was shown that growth in non-polar and semi-polar directions, which appears on the edges of the crystal during crystallization process, can generate a very large tensile stress in GaN growing in the c-direction. This stress is much larger than the one generated due to a lattice mismatch between the ammonothermal seed and the deposited HVPE layer. [ABSTRACT FROM AUTHOR]

Study on the sources of stress in HVPE-GaN layer crystallized on 1-in. ammonothermally grown GaN seed is presented in this paper. Characterization by means of X-ray diffraction and transmission electron microscopy is performed. HVPE-GaN samples of high quality and those with visible quality deterioration are investigated on c-plane and m-plane cross-sections. Special attention is paid to HVPE material growing in semi-polar and non-polar directions on the edges of the seed and the growing layer. It is shown that this material generates significant stress leading to a structural deterioration of HVPE-GaN growing in the c -direction. [ABSTRACT FROM AUTHOR]

We studied the incorporation of Mg-related impurity centers in GaN crystals depending on the direction of the crystallization front. Two series of GaN crystals – (i) undoped and (ii) Mg-doped – were grown by High Nitrogen Pressure Solution (HNPS) method under otherwise identical conditions. Each series contained four samples with ( 10 1 ¯ 0 ) , ( 11 2 ¯ 0 ) , ( 20 2 ¯ 1 ¯ ) and ( 20 2 ¯ 1 ) orientations. The low-temperature photoluminescence (PL) spectroscopy was used for characterization of the obtained crystals. The observed differences in the PL spectra of GaN:Mg crystals suggested that Mg incorporation in GaN grown by HNPS method depends considerably on the orientation of crystallization front. The concentration of Mg impurity incorporated into the GaN crystals subsequently increases for the following sequence of planes: ( 10 1 ¯ 0 ) , ( 11 2 ¯ 0 ) , ( 20 2 ¯ 1 ¯ ) and ( 20 2 ¯ 1 ) . For ( 10 1 ¯ 0 ) , ( 11 2 ¯ 0 ) and ( 20 2 ¯ 1 ¯ ) planes the blue band is related only to O N – Mg Ga donor-acceptor pair (DAP) transitions, while for ( 20 2 ¯ 1 ) plane the incorporation of Mg-H complexes occurs additionally to the formation O N – Mg Ga DAP. [ABSTRACT FROM AUTHOR]

A series of SiO x containing a-C:H films was deposited on polished silicon substrates by RF PACVD ( Radio Frequency Plasma Assisted Chemical Vapour Deposition ) method using methane and hexamethyldisiloxane (HMDSO). Three CH 4 /HMDSO flow ratios and four self-bias voltages were applied for the synthesis of 12 different a-C:H:SiO x coatings having different properties and silicon/oxygen concentrations. The chemical structure of the deposited films was determined by Fourier transform infrared spectroscopy. Detailed characterization of the mechanical properties of SiO x incorporated carbon coatings was made using the nanoindentation (hardness and modulus) and profilometry (residual stress) methods. Hardness and elastic modulus were used for the evaluation of the endurance capability (H/E) and resistance to plastic deformation (H 3 /E 2 ). The elastic recovery was calculated based on loading and unloading curves. The residual stress of diamond-like carbon coatings can be effectively reduced by the incorporation of SiO x . The mechanism of reducing the residual stress depending on the applied self-bias voltage is proposed. In the case of all of the examined coatings the addition of SiO x reduces the hardness, while for high self-bias voltages an increase of endurance capability and resistance to plastic deformation is observed. [ABSTRACT FROM AUTHOR]

We investigate the electronic structure of the skutterudite-related Ce3M4Sn13 compounds, where metal M is Co, Ru, or Rh, using x-ray photoemission spectroscopy (XPS) and band structure calculations, both within local density approximation scheme and within scheme including additional Coulomb correlations (LDA+U). The 4-electron states located near the Fermi level slightly change the intensity with applying the correlation energy U. We note the large impact of 4-electron correlation, which is clearly observed in the change of Ce 5p states located about 18 eV in the valence band. Namely, for Ce3Rh4Sn13 and Ce3Ru4Sn13 the 4-electron correlations significantly shift the 5p states towards higher binding energies, while for Ce3Ru4Sn13 the energy of the Ce 5 p states almost does not depend on U. The influence of the 4-electron correlations is also manifested by the positive magnetoresistivity (MR) of Ce3Ru4Sn13 and the Ce3-xLaxRh4Sn13 alloys that reaches 40% at the highest magnetic field (B = 9 T) for the sample x - 0.6, whereas only a small positive MR ~ 0.5% is observed in Ce3Ru4Sn13. The magnetoresistivity of Ce3Ru4Sn13 exhibits quite different behavior and is negative. [ABSTRACT FROM AUTHOR]

The results of the Hydride Vapor Phase Epitaxy (HVPE) on ammonothermal GaN seeds (Am-GaN) with various misorientations: 0.3, 0.5 and 1 degree to the [1 0 −1 0] and [1 1 −2 0] directions are presented. Growth rate and structural quality of the HVPE-GaN layers are analyzed. Morphology of the crystal growing surface at the beginning of the crystallization process (after one and two hours of growth) and at the end of it (after eight hours) is presented as a function of the Am-GaN seed misorientation. Based on these results a rough growth model is proposed and discussed in detail. [ABSTRACT FROM AUTHOR]

In this work homoepitaxial HVPE-GaN growth on non-polar and semi-polar GaN seeds was described. Two crystallization processes, in the same experimental conditions but using different carrier gases: N 2 and H 2 , were performed. An influence of growth directions and growth conditions on the growth rate and properties (morphology, structural quality and oxygen and silicon contaminations) of obtained crystals were investigated and discussed. It was shown that the growth rate strongly depends on the growth direction and the carrier gas. It was demonstrated that for the semi-polar [20–21] direction it was possible to obtain high quality and highly conductive (without intentional doping) gallium nitride layers. [ABSTRACT FROM AUTHOR]

Recently, it was reported that the skutterudite-related Ce3Rh4Sn13 heavy fermion compound has a large electronic specific heat coefficient C(T)/T and short-range magnetic correlations, both suggest a possible quantum critical point (QCP). We present the low-temperature specific heat, resistivity, and susceptibility of Ce1-xLaxRh4Sn13, which do not confirm the presence of QCP. X-ray photoelectron spectroscopy revealed a stable configuration of Ce atoms consistent with magnetic susceptibility data. Magnetic susceptibility shows that the sixfold-degenerate multiplet of Ce3+ ion splits into three doublets due to the lower local symmetry of CeSn12 cage in the cubic Ce1-xLaxRh4Sn13 compounds. The resistivity, specific heat, and susceptibility data are consistent with our band-structure calculations. The chemical bondings in the unit cell of Ce1-xLaxRh4Sn13, analyzed based on the difference charge density maps from band-structure calculations within the virtual crystal approximation explain the deformation of the cages and the crystal electric field properties of the system. [ABSTRACT FROM AUTHOR]