Volume compression of CuCl to 7 GPa

The unit cell volume of CuCl as a function of pressure has been measured up to 7 GPa (giga Pascals). The compression behaviour is quite normal. The analysis of the compression data gives 40·3±1·5 GPa for the bulk modulus of the zinc blende phase. The zinc blende phase transforms to a tetragonal phase at 5·5 GPa, the volume change associated with the transformation being 12%. A comparison of the bulk modulus of CuCl with those of CuBr and CuI indicates that an anomaly exists in this group.     

Measurements of the work function of single-walled carbon nanotubes encapsulated by AgI,AgCl, and CuBr using kelvin probe technique with different kinds of probes

We report the results on the measurements of the work function of single-walled carbon nanotubes encapsulated by Agl (AgI@SWCNT), AgCl (AgCl@SWCNT), and CuBr (CuBr@SWCNT) by the local Kelvin probe technique. We found the values of the work function of tubes encapsulated with AgI and AgCl (Φ(AgI@SWCNT) = 5.08 ± 0.02, Φ(AgCl@SWCNT) = 5.10 ± 0.02 eV) to exceed substantially that of pristine carbon nanotubes, and the value of the work function of carbon nanotubes encapsulated with CuBr is Φ(CuBr@SWCNT) = 4.89 ± 0.03 (eV). The measurements are carried out using different kinds of microscope probes including multi-walled carbon nanotube tips.     

Optical microscopic,X-ray diffraction,and electrical resistance studies of CuCl at high pressure

Electrical resistance and X-ray diffraction measurements and also optical observations under a polarizing microscope were made on CuCl to pressures in excess of 12.5 GPa at room temperature using a diamond anvil cell. Resistance measurements were also performed in a piston-cylinder apparatus to pressures of approximately 5.5 GPa at room temperature. Three samples of CuCl prepared by different methods were examined. No anomalous pressure dependence in electrical resistance was found in the pressure range studied, and no dramatic changes in optical transmission were observed up to pressures of approximately 10.0 GPa. Optical observations and X-ray diffraction measurements indicate the existence of four phases in the pressure range studied, including a nonconducting black opaque phase which grows with time when CuCl is left for several days at the highest pressures.     

Influence of ion bombardment on growth and properties of PLD created DLC films

A hybrid PLD system with ion bombardment of films was developed. Growing DLC films were modified during the laser deposition (10 J?cm^?2) by argon ions with energy in the range from 40 eV to 210 eV and cathode current of 0.15 A and 0.5 A. The content of sp² “graphitic” and sp³ “diamond” bonds was measured using XPS. Sp³ bonds changed from 60 % to 81 %. We found the highest sp³ content for energy of 40 eV. Hardness (and reduced Young’s modulus) were determined by nanoindentation and reached 49 GPa (277 GPa). Film adhesion was studied using the scratch test and was up to 14 N for titanium substrates. Relations among deposition conditions and measured properties are presented.     

Low energy electron attenuation length studies in thin amorphous carbon films

The results of experiments on low energy electrons passing through thin amorphous carbon films are reported. For electron energies between 50 and 3000 eV, electron attenuation lengths were determined by electron transmission measurements through carbon films of thicknesses between 81 and 210 Å. The density of these amorphous carbon films was also obtained by a sink—float method and found to be 1.90 ± 0.05 g cm^?3. The electron attenuation length for inelastic scattering was found to increase monotonically from approximately 10 to 55 Å over the 50 to 3000 eV range. Over the 500–3000 eV energy region, the results are in good agreement with mean free paths calculated using optically measured dielectric functions.     

In situ electrical resistance and activation energy of solid C_(60) under high pressure

The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300-423 K by using a designed diamond anvil cell. In the experiment, four parts of boron-doped diamond films fabricated on one anvil were used as electrical measurement probes and a W-Ta thin film thermocouple which was integrated on the other diamond anvil was used to measure the temperature. The current results indicate that the measured high-pressure resistances are bigger than those reported before at the same pressure and there is no pressure-independent resistance increase before 8 GPa. From the temperature dependence of the resistivity, the C60 behaviors as a semiconductor and the activation energies of the cubic C60 fullerene are 0.49, 0.43, and 0.36 eV at 13, 15, and 19 GPa, respectively.     

Proprietes optiques de couches de Be evaporees et etudiees sous ultra-vide dans L'u.v. De 2,5–25 eV

Optical constants of thin films of Be are obtained from reflectance measurements between 2 and 25 eV. These films are obtained by evaporation in ultra-high vacuum and studied in situ. The optical conductivity σ and real part ?₁ of the dielectric constant are compared with previous theoretical and experimental results. The agreement is good, particularly for the important structure of σ at 4.8 eV. The volume plasmon is situated at 19.2 ± 0.4 eV and the surface plasmon at 13.6 eV.     

Phase diagram of GaAs

Abstract

Optical measurements in the diamond anvil cell (DAC) as well as thermodynamics, show cubic GaAs I to be unstable at 300 K, at 13 GPa. The thermodynamic phase line from GaAs I to the high pressure (H.P.) form(s) is at 11 ± 2 GPa. Large hyteresis makes the actual I→II transition observable only at 17.5 ± 1 GPa.     

X-ray photoelectron and Raman studies of microwave Plasma Assisted Chemical Vapour Deposition (PACVD) diamond films

X-ray photoelectron and Raman spectroscopies were used to investigate the chemical and the structural properties of thin diamond films synthesised by Plasma Assisted Chemical Vapour Deposition (PACVD). Continuous polycrystalline diamond films were grown under different plasma conditions and based on the combination of detailed XPS and Raman spectroscopic analysis two main topics are highlighted (i) the stress measurements were discussed by distinguishing clearly the chemical effects from the mechanical effects; (ii) an electronic gap at 2.7 eV probed by Raman resonance that corresponds to an energy loss peak on the XPS carbon signal, was related to the surface hydrogenation.     

Spin-orbit splitting of the copper halides and its volume dependence

We have investigated theoretically and experimentally the dependence of the spin-orbit splitting of the edge excitons in CuCl, CuBr, and CuI on volume. The results indicate a large contribution of the change in p(halogen)-d(Cu) hybridization with volume, especially for CuCl.     

High strain rate sensitivity of hardness in quinary Ti-Zr-Hf-Cu-Ni high entropy metallic glass thin films

Quinary Ti-Zr-Hf-Cu-Ni high-entropy metallic glass thin films were produced by magnetron sputter deposition. Nanoindentation tests indicate that the deposited film exhibits a relatively large hardness of 10.4±0.6 GPa and a high elastic modulus of 131±11 GPa under the strain rate of 0.5 s⁻¹. Specifically, the strain rate sensitivity of hardness measured for the thin film is 0.05, the highest value reported for metallic glasses so far. Such high strain rate sensitivity of hardness is likely due to the high-entropy effect which stabilizes the amorphous structure with enhanced homogeneity.     

The excitonic absorption of CdS under pressure

Abstract

We have investigated the pressure dependence of the absorption edge of tlie E_A-E_B- and the E_C-excitons of 1pi thick CtlS(hex) crystal slabs. We obtaiurd dE_Θ/dP =dE_c/dP = 47±3 meV/GPa for T=300K and dE_A/dP= dE_B/dP = 43±3 meV/GPa for T=78K. With tliese values we were able to determine the crystal-field splitting (68f4 nieV) aid the spin-orbit splitting (26±2 meV). The resulting pressure shifts of tlie rxcitonic energies were in agreement witli a κ · p-calculation of tlie transition energies using tlie perturbation niatrix of G.E. Pikus for Δ_so ? Δ_c. The refractive Index n‖c was iiieasured for T=300K up to 2.2 GPa and described by Marples Model.     

Ultra‐thin nanocrystalline diamond films (<100 nm) with high electrical resistivity

Thick diamond films are known to exhibit remarkably high electrical resistivity and thermal conductivity. However, on thin films, difficulties are often observed to achieve such performances. In this study, the synthesis of ultra‐thin diamond films was optimized towards the possibility to maintain high dielectric performances on layers compatible with today requirements for Silicon‐On‐Diamond technology, and namely aiming at films with thicknesses equal or below 150 nm. The nucleation of diamond nanocrystals is crucial to obtain films with thickness lower than 100 nm. A Bias Enhanced Nucleation step (BEN) was improved to achieve nucleation densities above 10¹¹ cm^–2 although the process was also tuned to limit the size of the nanocrystals during this step. The control of the carbonization of the silicon substrate is also essential to reach such a density with a high reproducibility. The BEN is followed by a growth step with optimized conditions. The films were characterized by SEM and Spectroscopic Ellipsometry. Electrical conductivity measurements were conducted on thin diamond films and values obtained on layers below 100 nm were as high as 5 × 10¹³ Ω cm; a value significantly higher than the state of the art for such thin films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of germanium thin films on the W(100) surface

The growth of Ge thin films on the surface of a textured predominantly (100)-oriented tungsten ribbon is studied by thermal desorption spectrometry at different substrate temperatures over a wide range of coverages. The mechanism of growth of the Ge films at T = 300 K is similar to a layer-by-layer mechanism. For T > 300 K, the films grow through the Stranski-Krastanov mechanism, according to which the completion of the monolayer coverage is followed by the formation of three-dimensional crystallites; as a result, the desorption kinetics changes. For small coverages (i.e., in the absence of lateral interactions), the activation energy of Ge desorption from W(100) is E = 4.9 ± 0.2 eV. In a monolayer, this activation energy decreases to E = 3.9 ± 0.2 eV due to the repulsive lateral interactions. The energy of pairwise lateral interactions is determined to be ω = 0.3 eV.     

Diamond and cubic boron nitride under high pressure: Raman scattering,equation of state and high pressure scale

Abstract

The development of the diamond-anvil cell has stimulated Raman-scattering investigation of vibrational modes in covalent crystals. The linear pressure coefficient reported for diamond by Hanfland et at' (2.90 ± 0.05 cm-¹/GPa) agrees to within mutual experimental error with the result of Boppard et aL² (2.87±0.01 cm-¹/GPa). As to cubic boron nitride, the only work by Sanjurjo ef aL3 reports 3.45 ± 0.07 cm-¹/GPa for LO- and 3.39 ± 0.08 cm-¹/GPa for TO- modes. Since no compressibility data are availablel^1?3, the mode Griineisen parameter γ = ‐ δ In γ/δ is defined as y = K/Y·dv/aP and depends on the bulk modulus K and the calibration of the ruby scale. The above papers report y= 0.96 and y=0.95±O.O3fordiamondand γ_Lo=1.21,γTo=1.51 forBN.     

Characterization of hydrogenated amorphous carbon thin films by end-Hall ion beam deposition

Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24 eV to 48 eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5-0.8 nm for α-C:H and 0.35 nm for α-C:H:N films. When the ion energy was increased from 24 eV to 48 eV, the fraction of sp³ bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8 GPa to 12.5 GPa, and the Young's modulus increased from 100 GPa to 130 GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145 GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.     

Static compression of rare earth metal holmium to 282 GPa

ABSTRACT

The phase transitions and equation of state measurements were carried out on rare earth metal Holmium (Ho) to 282?GPa using toroidal diamond anvils thereby doubling the pressure range to which it has been studied previously. The first set of experiment employed standard beveled diamond anvils utilizing copper as an x-ray pressure standard to 217?GPa. The second set of experiment employed toroidal diamond anvils utilizing platinum as an x-ray pressure standard to 282?GPa. The recently proposed 16-atom orthorhombic structure (oF16) appeared to be stable between 103 and 282?GPa. The scaled axial ratio (c/a) shows a narrow range of variation of 1.58?±?0.05 for the five known crystalline phases of Ho to 282?GPa. The experimental equation of state of Ho is presented up to a threefold volume compression V/V_o?=?0.322.     

Ca2CuO3的高压结构性质研究

 采用金刚石压砧高压装置（DAC）,对具有Cu—O链结构的Ca₂CuO₃的多晶粉末样品进行了高压同步辐射能散X射线衍射实验。实验结果表明,在0～34 GPa压力范围内,Ca₂CuO₃晶体没有发生结构相变,用Birch-Murnaghan状态方程拟合,得到在压力导数B′₀=4时,零压体弹模量B₀=165.4±1.8 GPa。     

超高压下CsBr的结构与相变

 采用金刚石对顶压砧高压装置（DAC）、同步辐射X光源和能散法，对CsBr粉末样品进行了原位高压X光衍射实验，最高压力达115 GPa。观测到在53 GPa左右压力下，CsBr的最强衍射峰(110)劈裂成两个峰，标志了简单立方结构向四方结构的转变；在0至最高压力范围内（相应于V/V₀为1至0.463）测量了晶轴比c/a；在115 GPa内未观测到样品的金属化现象。     

Effect of annealing on photo accelerated chemically deposited Indium sulfide thin films with various cationic precursors

The present work reports the deposition of Indium sulfide thin films by a recently established novel method called photo-assisted chemical deposition technique. It is a very low cost method for the deposition of thin films, and can be easily scaled up for industrial production. Indium sulfide thin films are deposited on glass substrates through various cationic precursors and the effect of annealing on structural, optical and morphological properties was investigated. Films have been characterized with respect to their structural, optical and morphological properties by means of X-ray diffraction, UV–VIS-NIR Spectrophotometer, SEM and AFM techniques. As-deposited films on glass substrates were amorphous and became crystalline after annealing. The grain size of all the annealed films are larger than the as-prepared films and attained a maximum value for the film prepared with sulfate precursor. The calculated strain was compressive in nature. Surface roughness was estimated from the AFM measurements and found to be decreased in annealed samples. The film deposited with chloride precursor showed a higher visible transmittance of around 80 % and became 90 % on annealing. The variation of packing density follows the variation of the refractive index. The optical band gap of the samples was estimated and found to be within the range of 2.45–2.71 eV, which is in quite agreement with the literature.