Effect of N2/CH4 flow ratio on microstructure and composition of hydrogenated carbon nitride films prepared by a dual DC-RF plasma system

Hydrogenated carbon nitride (a-CN:H) films were deposited on n-type (1 0 0) silicon substrates making use of direct current radio frequency plasma enhanced chemical vapor deposition (DC-RF-PECVD), using a gas mixture of CH₄ and N₂ as the source gas in range of N₂/CH₄ flow ratio from 1/3 to 3/1 (sccm). The deposition rate, composition and bonding structure of the a-CN:H films were characterized by means of X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectrometry (FTIR). The mechanical properties of the deposited films were evaluated using nano-indentation test. It was found that the parameter for the DC-RF-PECVD process had significant effects on the growth rate, structure and properties of the deposited films. The deposition rate of the films decreased clearly, while the N/C ratio in the films increased with increasing N₂/CH₄ flow ratio. CN radicals were remarkably formed in the deposited films at different N₂/CH₄ flow ratio, and their contents are related to the nitrogen concentrations in the deposited films. Moreover, the hardness and Young’s modulus of the a-CN:H films sharply increased at first with increasing N₂/CH₄ flow ratio, then dramatically decreased with further increase of the N₂/CH₄ flow ratio, and the a-CN:H film deposited at 1/1 had the maximum hardness and Young’s modulus. In addition, the structural transformation from sp³-like to sp²-like carbon-nitrogen network in the deposited films also was revealed.     

Molecular structure of AlH3[N(CH2CH2)3CH]2

Reaction of AlH₃[N(CH₂CH₂)₃CH] with hexamethyltrisiloxane, (OSiMe₂)₃, gives rise to the bis-quinuclidine complex AlH₃[N(CH₂CH₂)₃CH]₂, which has been characterized by ¹H and ¹³C NMR spectroscopy and X-ray crystallography. The molecular structure of AlH₃[N(CH₂CH₂)₃CH]₂ consists of a trigonal bipyramidal aluminum with axial coordination of the quinuclidine ligands. Crystal data: orthorhombic, space group Pbcn, a = 10.6895(9), b = 12.266(1), c = 12.3794(9) Å, V = 1623.2(2) ų, and Z = 4.     

Crystal structure and phase transition in the compound [C6H5CH2NH(CH3)2]TlCl4

The N‐N dimethyl benzylammonium tetrachlorothallate (III) [C₆H₅CH₂NH(CH₃)₂]TlCl₄ crystallizes in the monoclinic system P2₁/n at room temperature with the following unit cell dimensions: a = 7.725(3) Å, b = 14.080(5) Å, c = 13.697(4) Å, β = 91.2(2)° with Z = 4. The structure shows a layer arrangement perpendicular to the b axis: planes of [TlCl₄]^‐ tetrahedra alternate with planes of [C₆H₅CH₂NH(CH₃)₂]⁺ cations. The cohesion of the atomic arrangement is ensured by hydrogen bonds N‐H…Cl. Differential scanning calorimetric and optical birefringence measurements reveals a phase transition at T = 339K. Raman spectroscopic study and dielectric measurements were performed to discuss the mechanism of the phase transition. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of laser fluence on c‐axis orientation of LiNbO3 piezoelectric films on nanocrystalline diamond by pulsed laser deposition

Completely c‐axis oriented LiNbO₃ piezoelectric films have been deposited on nanocrystalline diamond (NCD)/Si substrates with SiO₂ buffer layer by pulsed laser deposition. The amorphous SiO₂ buffer layer was formed on NCD/Si substrates by sol‐gel method. The c‐axis orientation and crystallinity of LiNbO₃ films are strongly dependent on the laser fluence, and the laser fluence 3.6 J/cm² is found to be the optimal value for the growth of oriented LiNbO₃ film, which has a smooth surface with composed of a large mount of uniform grains. The average surface roughness of LiNbO₃ films is about 6.7 nm.     

X-ray reflectometry of the specific features of structural distortions of He+-implanted Si(001) surface layers

The structural changes in the surface layers of silicon substrates, implanted by helium ions with energies from 2 to 5 keV and doses to 6 × 10¹⁵–5 × 10¹⁷ cm^?2, has been studied by high-resolution X-ray reflectometry. The damaged layer is found to have a total thickness comparable with the total ion path length (estimated from the SRIM model) and a multilayer structure: a strongly amorphized layer with reduced density, a porous (incapsulated) layer, and a deformed layer. The thickness of sublayers, their density ρ(z), and the mean strain (～5 × 10^?3) have been determined. The characteristic pore size is estimated to be 5–20 nm. It is shown that the presence of a nanoporous layer facilitates the formation of diffuse scattering, which can be used to diagnose layers by high-resolution X-ray reflectometry.     

Vapour epitaxial growth and characterization of InAs1-xPx

The vapour growth of InAs_1-xP_x layers has been carried out by the hydride process. The phosphorus rich part of the system (0.7 ? x ? 1) was especially investigated. Heteroepitaxial deposits of InAs_1-xP_x and InP have been performed on substrates such as InAs, GaAs and GaP. A systematic study of the influence of the substrate orientation on the quality of the layer has been carried out by growth on hemispherical substrates. Preferential planes have been pointed out: (100) and (111) A for InAs, (111) for GaAs and GaP. The band gap variation as a function of the composition has been determined by photoluminescence at 4.2 °K and X-ray diffraction measurements. It fits the equation: E_G(x) eV = 0.425 + 0.722 x + 0.273 x² at 4.2 °K.     

Strain relaxation in multilayer III–N structures on Si(111) substrates

X-ray diffractometry and X-ray scattering reciprocal space maps have been used to study strain relaxation in a complex buffer composed of seven intermediate layers of Al _x Ga_{1 ? x} N composition with different values of x, decreasing with an increase in the distance from the substrate. The layers have been grown by hydride metalorganic vapor phase epitaxy on silicon and sapphire substrates. Differences in the structural quality of the first four layers of a multilayer buffer grown on different substrates have been revealed. A gradual smoothing out of these differences in the next three layers with an increase in the layer serial number has been shown. The last grown intermediate Al _x Ga_{1 ? x} N layer and the GaN layer grown on it have identical thicknesses and degrees of mosaicity, regardless of the substrate type. Device structures grown on a complex buffer demonstrate emission in approximately the same wavelength range.     

Effect of growth parameters on the properties of GaN : Zn epilayers

The vapor-phase HCl/Ga/NH₃ method for deposition of GaN : Zn epilayers on sapphire substrates has been investigated to determine the dependence of epilayer resistivity, cathodoluminescence, and surface quality on the growth parameters. Both nucleation and control of the epilayer properties have been significantly improved by introducing HCl directly into the deposition zone in addition to the HCl that passes over the Ga source to produce GaCl. The effect of annealing on the stability of undoped layers and on the cathololuminescence of Zn-doped layers has also been investigated. Electroluminescent devices with reproducible properties have been obtained by growing structures consisting of an undoped n⁺ layer, a Zn-doped n-type layer, and a very thin, Zn-doped, high-resistivity layer whose growth parameters determine the emission wavelength and electroluminescence efficiency.     

The microstructure and magnetic property of TiO2‐terminated SrTiO3 substrate selected growth cubic phase CaRuO3 film

CaRuO₃ thin films with various thicknesses were synthesized by pulsed laser deposition respectively on SrTiO₃ substrates with SrO‐ and TiO₂‐termination. The microstructure of these films was studied by transmission electron microscopy. The results demonstrate that the CaRuO₃ thin films grown on TiO₂‐terminated substrates show quite uniform morphology, whilst they do the facet morphology when the substrates are SrO‐terminated. In addition, there is a 5∼7 unit‐cell‐thickness cubic CaRuO₃ layer in the films grown on TiO₂‐terminated substrates. The measured ferromagnetic hysteresis loop is attributed to the cubic CaRuO₃ layer, which is supported by a first‐principles calculations. On the contrary, there is free of cubic CaRuO₃ layer in samples grown on SrO‐terminated substrates. The crystallographic domains, the orientation relationship between domains and substrates and crystal defects in these films were studied as well. The different growth mechanism of CaRuO₃ on SrO‐ and TiO₂‐terminated SrTiO₃ substrates may be correlated with the selective nucleation and growth.     

Epitaxial Deposition of GaAs in the Ga(CH3)3?AsH3?H2 System (III) Heteroepitaxy on Isolating Substrates

Epitaxial growth of GaAs has been achieved on CaF₂, α-Al₂O₃ and spinel substrates. X-ray investigations showed well defined relations between layer perfection and the quality of substrate material. The formation of epitaxial layers in pyrolytic deposition processes is discussed in terms of supersaturation and its influence on nucleation and layer growth.     

Synthesis and crystallographic characterization of a chiral complex of (R)‐2‐(pyridin‐2‐ylmethylene)amino‐2′‐hydroxy‐1,1′‐binaphthyl(L) with hydrated nickel(II) acetate

A chiral complex of (R)‐2‐((pyridin‐2‐ylmethylene)amino)‐2′‐hydroxy‐1,1′‐binaphthyl ( L ) with hydrated nickel (II) acetate has been synthesized and spectroscopically characterized. The crystal structure of [NiL₂(CH₃OH)(CH₃COO)]CH₃COO·CH₃OH has been determined by single‐crystal X‐ray diffraction. The complex crystallizes in the orthorhombic space group P 2(1) 2(1) 2(1) with cell constants a = 15.1035 (19), b = 17.836 (2), c = 18.730 (2)Å, α = β = γ = 90.00°, Z = 4. The structure was solved by direct methods and refined to R = 0.0346 (wR₂ = 0.0863). The analytical result of the crystal structure indicates that a pair of L ligands chelate to a Ni (II) atom in an asymmetric fashion with one Ni‐N bond being longer than the other, the Ni (II) atom is further coordinated by one methanol molecule and one acetate anion to form a distorted octahedral geometry. In the crystal of the complex, the coordination cation [NiL₂(CH₃OH)(CH₃COO)]⁺, the uncoordinated methanol molecule and uncoordinated acetate anion are further assembled into one‐dimensional chain structure via intermolecular hydrogen bonds along the a‐axis. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Convenient Route to Alkylene Dithiophosphato Ligands: Synthesis and Crystallographic Analysis of [OCH<Subscript>2</Subscript>CMe<Subscript>2</Subscript>CH<Subscript>2</Subscript>OPS<Subscript>2</Subscript>HNEt<Subscript>3</Subscript>]

Abstract  

Triethylammonium salts of O,O′-alkylene dithiophosphato like OGOPS₂HNEt₃, [where, G = –CH₂CMe₂CH₂–(1), –CH₂CEt₂CH₂–(2), –CMe₂CH₂CHMe–(3) and –CMe₂CMe₂–(4)] have been synthesized in quantitative yield by the direct reaction of P₂S₅ with 1,2- and 1,3-substituted glycols in presence of triethylamine, Et₃N, in 1:2:2 molar stoichiometry in toluene. These have been mainly characterized by molecular weight, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic studies. Single crystal X-ray structure analysis of [OCH₂CMe₂CH₂OPS₂HNEt₃] reveals that phosphorus atom is tetrahedrally bonded to two sulfur atoms and two oxygen atoms in the ring and the molecule exists as discrete cation and anion. The structure is stabilized by cation–anion N–H···S hydrogen bonded interactions. Antiparallel pattern of triethylammonium ion is sandwiched within the two-dimensional layers of the ring system.     

Fine embossing of chalcogenide glasses – a new fabrication route for photonic integrated circuits

For the first time embossing of ribs, from 1 to 10 μm wide and ∼10 mm long, has been carried out in chalcogenide glass layers sputtered onto semiconductor wafer substrates, with potential to act as monomode waveguides; these features have been similarly embossed in the surface of bulk chalcogenide glasses. The embossing shows very good replication of the GaAs mould patterning to 1 μm definition, with evidence also for sub-micron replication. For the embossing, thin coatings of the chalcogenide glasses were sputtered onto wafer substrates as follows: (i) a 6 μm layer of Ge₁₇As₁₈Se₆₅ (at.%) onto porous Si-on-Si wafer substrates and (ii) a 4 μm layer of Ge₁₅As₁₅Se₁₇Te₅₃ onto uncoated GaAs substrates. The Ge₁₇As₁₈Se₆₅ sputtered glass layer on porous Si-on-Si was demonstrated to slab waveguide at 1.55 μm wavelength; it was designed to achieve monomode waveguiding at 1.55 μm after embossing, for the 5 μm wide rib. The series of ribs, 1–10 μm wide, were successfully embossed in the Ge₁₇As₁₈Se₆₅ glass sputtered layer on porous Si-on-Si, but cracking of the glass layer occurred during the embossing process. Successful embossing of ribs without the glass layer cracking was achieved for the Ge₁₅As₁₅Se₁₇Te₅₃ sputtered glass layer on uncoated GaAs. Due to its relative simplicity, it is likely that hot embossing of this type of glass-based matrix offers an extremely promising route for producing high-resolution, guided-wave optical components and circuitry at low-cost, high-volume, and for a wide wavelength range.     

Epitaktische Abscheidung von GaAs im System Ga(CH3)3?AsH3?H2 (I) Autoepitaktische Abscheidung

Some aspects of Ga(CH₃)₃/AsH₃/H₂ pyrolysis are described. The quality of the epitaxial GaAs layers on GaAs substrates is examined by chemical etching, X-ray technique and observation of the surface morphology. The investigations show a relation between the quality of the layers and growth conditions (As/Ga-proportion, substrate temperature).     

Vibrational spectra and structure of organophosphorus compounds

The infrared spectra of both CH₃OPSClF and CD₃OPSClF in the vapor phase have been recorded from 4000 to 33 cm^–1. The Raman spectra of the liquids have been recorded and a temperature study of the CD₃OPSClF spectrum has been completed. Two isomeric configurations are indicated from the low-temperature Raman spectra. The doublet due to the P=S stretching vibration has a separation of only 15 cm^–1. From the variation in the relative intensity of the doublet, an energy difference of –450 cal/mol was obtained for the two isomers. The fundamental vibrations are assigned on the basis of the band positions and isotopic shift factors. The assignments are compared to those previously given for the CH₃OPSCl₂ and CH₃OPSF₂ molecules.For part VIII,see Inorg. Chem.8, 2796 (1969).Taken in part from the thesis submitted by J. W. Clark to the Department of Chemistry for the Ph.D. degree, August 1968.We wish to thank Miss Ann Perez for recording the infrared spectra. Acknowledgement is also made to the United States Army Research Office, Durham, for the support of this research by Grant Number DA-ARO-D-31-124-G824.     

Heteroepitaxial growth of GaP on silicon

Epitaxial gallium phosphide layers have been grown on silicon substrates by the metal-organic process. This process involves the reaction between trimethylgallium (CH₃)₃Ga and PH₃ and gives a high density of nucleation sites on the silicon. The influence of the substrate orientation and of the deposition temperature on the crystallinity of the layers has been studied. Best results were obtained on (001) oriented substrate at a deposition temperature of 800°C. X-ray reflection topographs of the layers have revealed the formation of cracks extending along the [110] direction, which are explained by the lattice mismatch and the difference in thermal expansion coefficients. The cracking is asymmetric with the main direction parallel to [110]. The density of cracks can be reduced by a two stage epitaxy. The electrical properties of undoped and n-type doped layers have been assessed by Hall and C(V) measurements. It shows auto-doping with silicon coming from the substrate.     

Crystal Structure of Cuprate (II) Complex of Tetradentate ONNO Ligand: 4-[(2-{[(1<Emphasis Type="Italic">E</Emphasis>)-1-Methyl-3-oxobutylidene]amino}ethyl)imino]pentan-2-one

Abstract  

The title copper complex, Cu[CH₃CO–CH=C(CH₃)N(CH₂–CH₂)N(CH₃)C=CHCO CH₃], has been synthesized by the reaction of ligand, 4-[2-(1-methyl-3-oxo-but-1-enylamino)-ethylamino]-pent-3-en-2-one (ONNO) and copper chloride. The structure of the synthesized complex was determined by IR, NMR, mass spectroscopic data and X-ray crystallography. The structure was solved in monoclinic, space group P2₁/n with a = 10.971 (4), b = 8.988 (3), c = 12.830 (5) ?, β = 93.512 (5), V = 1,262.7 (6) ?³, Z = 4 and with R _int = 0.047. The geometry around the copper atom displays a distorted square-planner structure by coordinating with two oxygen atoms from carbonyl moiety and two nitrogen heteroatom from the central moiety of the ligands and thus established two 6-membered rings and one 5-membered ring. The two nitrogen atoms form two anionic–cationic bonds to complete the coordination sphere around the copper metal atom.     

High-quality silicon/insulator heteroepitaxial structures formed by molecular beam epitaxy using Al2O3 and Si

Heteroepitaxial growth of γ-Al₂O₃ films on a Si substrate and the growth of Si films on the γ-Al₂O₃/Si structures by molecular beam epitaxy have been investigated. It has been found from AFM and RHEED observations that, γ-Al₂O₃ films with an atomically smooth surface with an RMS values of ∼3 Å and high crystalline quality can be grown on Si (1 1 1) substrates at substrate temperatures of 650–750°C. Al₂O₃ films grown at higher temperatures above 800°C, did not show good surface morphology due to etching of a Si surface by N₂O gas in the initial growth stage. It has also been found that it is possible to grow high-quality Si layers by the predeposition of Al layer followed by thermal treatment prior to the Si molecular beam epitaxy. Cross-sectional TEM observations have shown that the epitaxial Si had significantly improved crystalline quality and surface morphology when the Al predeposition layer thickness was 10 Å and the thermal treatment temperature was 900°C. The resulting improved crystalline quality of Si films grown on Al₂O₃ is believed to be due to the Al₂O₃ surface modification.     

Synthesis, crystal structure, and thermal properties of {[Cd2(L1)3(sac)4]⋅2CH2Cl2}∞: A coordination polymer with non-interpenetrating ladders containing cadmium in a rare, trigonal bipyramidal coordination environment (L1 = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, sac = saccharinate)

The new coordination polymer, {[Cd₂(L1)₃(sac)₄]?2CH₂Cl₂}_∞:, has been prepared from the reaction of 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (L1) with [Cd(sac)₂(H₂O)₄].2H₂O(sac = saccharinate) in a methylene chloride/ethanol solvent mixture. The compound features a non-interpenetrating ladder motif constructed from Cd(L1)3 T-shaped units. The Cd atoms are coordinated to three nitrogen donor atoms from three L1 ligands and two nitrogen donor atoms from two saccharinate ligands in a rare, trigonal bipyramidal coordination environment. The compoundwas further characterized by IR spectroscopy and DTA/TGA. {[Cd₂(L1)₃(sac)₄]?2CH₂Cl₂}_∞: crystallizes in the triclinic space group P-1 with a = 10.8747(19)Å, b = 12.626(2)Å, c = 15.749(3)Å, α = 111.839(3)^°, β = 97.442(3)., and γ = 106.239(3)^°     

Investigation of calcium carbonate precipitated in the presence of alkanols

The influence of myristyl alcohol (CH₃(CH₂)₁₃OH), cetyl alcohol (CH₃(CH₂)₁₅OH) and behenyl alcohol (CH₃(CH₂)₂₁OH) on the structure, morphology, size and surface properties of calcium carbonate (CaCO₃) has been investigated. Changes in the nature of the washing solvent, in the C_nOH/Ca²⁺ and CO₃²⁻/Ca²⁺ molar ratios and in temperature have been also evaluated. The sole polymorph produced was rhombohedral calcite. At room temperature, while microspheres composed of submicrocubes were produced at a high molar ratio CO₃²⁻/Ca²⁺ and low CH₃(CH₂)₁₅OH concentration, a stoichiometric molar ratio CO₃²⁻/Ca²⁺ and high CH₃(CH₂)₁₅OH concentration induced the formation of microcubes and microboxes. In the presence of this alkanol (12 % molar) a significant enhancement of the water contact angle (ca. 40 °) resulted in a sample obtained with a stoichiometric CO₃²⁻/Ca²⁺ ratio. These results emphasize the key role played by the three non‐ionic surfactants in the formation of materials with variable crystal shape and wettability and thus technological interest for a range of applications.