Selective etching and epitaxial refilling of silicon wells in the system SiH4/HCl/H2

Wells were etched in (100) silicon by different kinds of selective etching and were selectively refilled by using different gas systems. Masking materials were SiO₂ and Si₃N₄; for the refilling the systems SiCl₄/H₂ and SiH₄/HCl/H₂ were studied. By using a combination of weak anisotropic gas etching with HCl (Si₃N₄ films as mask) and of SiH₄/HCl/H₂ as refilling system, plane surfaces without ridges at the boundary of the mask and without nuclei on the mask were reached. The results were obtained by SEM, light microscopic and profile investigations and are compared with the other kinds of etching and refilling.     

Undoped amorphous SiNx: H alloy semiconductors: Dependence of electronic properties on composition

The electrical and optical properties of a-SiN_x:H thin films prepared by rf growth-discharge in SiH₄N₂H₂ without B or P doping have been measured for 0 < x ? 0.6. It is observed that the activation energy for extended-state electron conduction as well as the optical gap are unaffected by N content for x ? 0.4. The electron mobility in extended states is improved by as much as a factor of 10 by the N incorporation. There is a rapid conversion from the tetrahedral network to a Si₃N₄ network as x increases above ≈ 0.4.     

A Novel Three Dimensional Organic–Inorganic Hybrid Based Porous Phase: Synthesis and Characterization of Reduced Oxovanadium pyromellitate, [VIV2O2(H2O)2(C6H2(COO)4)]

The hydrothermal reaction of a mixture of VOSO₄ · xH₂O, 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) and 0.1 M H₂SO₄ for 72 h at 160 °C gives blue needle like crystals of [V^IV ₂O₂(H₂O)₂(C₆H₂(COO)₄)] in 30% yield. The compound has a porous 3-D extended network structure having a rigid architecture which is held together by the multidentate functionalities of 1,2,4,5-benzenetetracarboxylate ligand. Crystal data for the compound: monoclinic space group C 2/c (No:15), a = 11.756(5) ?, b = 9.645(3) ?, c = 11.822(7) ?, β = 107.10(4)°, Z = 8. The compound constitutes the first example of a fully reduced oxovanadium based solid incorporating the organic ligand. This article consists of synthesis, crystal structure and characterization of [V^IV ₂O₂(H₂O)₂(C₆H₂(COO)₄)].     

Crystal structure of britvinite [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)]: A new layered silicate with an original type of silicon-oxygen networks

The crystal structure of a new mineral britvinite Pb_7.1Mg_4.5(Si_4.8Al_0.2O₁₄)(BO₃)(CO₃)[(BO₃)_0.7(SiO₄)_0.3](OH, F)_6.7 from the Lángban iron-manganese skarn deposit (V?rmland, Sweden) is determined at T = 173 K using X-ray diffraction (Stoe IPDS diffractometer, λMoKα, graphite monochromator, 2θ_max = 58.43°, R = 0.052 for 6262 reflections). The main crystal data are as follows: a = 9.3409(8) ?, b = 9.3579(7) ?, c = 18.8333(14) ?, α = 80.365(6)°, β = 75.816(6)°, γ = 59.870(5)°, V = 1378.7(2) ?³, space group P1, Z = 2, and ρ_calcd = 5.42 g/cm³. The idealized structural formula of the mineral is represented as [Pb₇(OH)₃F(BO₃)₂(CO₃)][Mg_4.5(OH)₃(Si₅O₁₄)]. It is demonstrated that the mineral britvinite is a new representative of the group of mica-like layered silicates with structures in which three-layer (2: 1) “sandwiches” composed of tetrahedra and octahedra alternate with blocks of other compositions, such as oxide, oxide-carbonate, oxide-carbonate-sulfate, and other blocks. The tetrahedral networks (Si₅O₁₄)_∞∞ consisting of twelve-membered rings are fragments of the britvinite structure. Similar networks also form crystal structures of the mineral zeophyllite and the synthetic phase Rb₆Si₁₀O₂₃. In the crystal structures under consideration, the tetrahedral networks differ in the rotation of tetrahedra with respect to the layer plane. Original Russian Text ? O.V. Yakubovich, W. Massa, N.V. Chukanov, 2008, published in Kristallografiya, 2008, Vol. 53, No. 2, pp. 233–242.     

Synthesis, Crystal Structure and Properties of the Binuclear Complex [Sm2(C10H9N2O4)2(C10H8N2O4)2(H2O)4]

Abstract  A novel binuclear Smarium (III) complex with N-(2-propionic acid)-salicyloyl hydrazone (C₁₀H₁₀N₂O₄, H₃L) was prepared and characterized. The crystal structure of [Sm₂(H₂L)₂(HL)₂(H₂O)₄] (1) was determined by X-ray single crystal diffractometry. 1 crystallizes in the monoclinic systerm, space group P2(1)/c, with a = 0.10229(2), c = 31.549(7), b = 0.70599(15) nm, and Z = 4. In the structure, Sm(III) is nine-coordinated by carboxyl O and acyl O atoms and imido N atoms of two ligands (H₂L and HL forms) and O atoms from two water molecules. H₂L and HL act as tridentate ligands which form two stable five-numbered chelating rings sharing one edge in the keto form for each ligand, and the carboxyl groups of two ligands were coordinated via bidentated bridging form. The coordination polyhedron around Sm (III) was described as a monocapped square antiprism. The inter- and intramolecular hydrogen bonds resulted in a three-dimensional network and provided extra stability for the structure. The complex was researched the interaction with calf thymus DNA by electronic absorption titration and emission titration. The results show that the complex is bound to calf thymus DNA mainly by intercalation .The complex also shows good fluorescence property. Index Abstract  The title compound, [Sm₂(H₂L)₂(HL)₂(H₂O)₄] was synthesized by the treatment of N-(2-propionic acid)-salicyloyl hydrazone (C₁₀H₁₀N₂O₄, H₃L) and Sm(NO₃) · 4H₂O and its crystal structure determined. Single crystal X-ray diffraction analysis reveals that Sm (III) is nine-coordinated by carboxyl O and acyl O atoms and imido N atoms of two ligands (H₂L and HL forms) and O atoms from two water molecules. The carboxyl groups of two ligands were coordinated via bidentated bridging form. The coordination polyhedron around Sm (III) was described as a monocapped square antiprism. The inter- and intramolecular hydrogen bonds resulted in a three-dimensional network and provided extra stability for the structure.      

Properties of a-Si : H : F deposited in SiF4/SiH4/Ar Gas mixtures by a glow-discharge technique

Films of silicon-hydrogen-fluorine alloys (a-Si : H : F) were prepared by capacitive coupling rf glow discharge in an SiF₄/SiH₄/Ar gas mixture. Up to 4% fluorine can be incorporated in films prepared with a gas mixture of SiF₄/(SiF₄ + SiH₄) = 0.72. The hydrogen concentration decreases as fluorine concentration increases but there is still more hydrogen than fluorine in films with the highest density of fluorine, which is in sharp contrast to the best films produced by the Madan and co-workers. Both dark conductivity and photoconductivity decrease as fluorine increases, though improvement of doping efficiency was observed in films with moderate concentrations of fluorine. The influence of hydrogen is more important than the influence of fluorine in the present silicon-hydrogen-fluorine alloys.     

Synthesis and structural analysis of Bis(2-hydroxyphenyl) phenylamine, PhN(o-C6H4OH)2: Comparison with Tris(2-hydroxyphenyl)amine N(o-C6H4OH)3

The molecular structures of N(o-C₆H₄OH)₃, PhN(o-C₆H₄OH)₂, andp-TolN(o-C₆H₄OMe)₂ have been determined by X-ray diffraction, thereby indicating several structural differences. For example, whereas the nitrogen in N(o-C₆H₄OH)₃ is pyramidal with Σ_C–N–C = 348.3^∘, the nitrogen atoms in PhN(o-C₆H₄OH)₂ andp-TolN(o-C₆H₄OMe)₂ are trigonal planar with Σ_C–N–C = 359.9^∘ and Σ_C–N–C = 360.0^∘, respectively. The phenyl andp-tolyl groups of PhN(o-C₆H₄OH)₂ andp-TolN(o-C₆H₄OMe)₂ lie close to the trigonal plane, while theo-C₆H₄OH ando-C₆H₄OMe groups are almost orthogonal to this plane. The coplanar and orthogonal orientations of the aryl groups of PhN(o-C₆H₄OH)₂ andp-TolN(o-C₆H₄OMe)₂ are in marked contrast to those of the phenyl groups within Ph₃N, which exhibit dihedral angles in the range 38–52^∘ and approximateD₃ symmetry. The observed structures of PhN(o-C₆H₄OH)₂ andp-TolN(o-C₆H₄OMe)₂ may be rationalized in terms of maximizing delocalization of the nitrogen lone pair into the phenyl andp-tolyl groups, while minimizing unfavorable overlap with theo-C₆H₄OH ando-C₆H₄OMe groups due to the presence of π-donatingortho-substituents; the orthogonal orientation of theo-C₆H₄OH ando-C₆H₄OMe groups is also one that minimizes unfavorable steric interactions between theortho-substituents.     

Synthesis and structure of (NH4)4[(DMF)2Mo8O26]· 2CH3CH2OH·2H2O (DMF= N , N -dimethylformamide)

A new organic-inorganic hybrid γ-octamolybdate complex, (NH₄)₄[(C₃H₇NO)₂Mo₈O₂₆]·2CH₃CH₂OH·2H₂O was synthesized from the mixture of ethanol, DMF, 4-aminobenzoic acid, (NH₄)₆Mo₇O₂₄·4H₂O, HCl and H₂O. The structure was determined by X-ray crystallography. It crystallizes in monoclinic P2₁/n space group with the crystal cell parameters of a = 8.8825(4), b = 21.1608(10), c = 11.1343(6) ?, β = 104.7720(10)°, V = 2023.64(17) ?³ and Z = 2. The crystal X-ray analysis shows that two DMF molecules are bound to γ-octamolybdate anion. The molecular structure is stabilized by the complex hydrogen bonding.     

A new dabco templated metal sulfate, (C6H14N2)[Mn (H2O)6](SO4)2. Chemical preparation, hydrogen-bonded structure and thermal decomposition

The crystal structure of manganese sulfate templated by 1,4-diaza-bicyclo[2.2.2]octane (abbreviated dabco), (C₆H₁₄N₂)[Mn(H₂O)₆](SO₄)₂, was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P2₁/c) with the following unit-cell parameters: a = 12.1392(2) ?, b = 12.3117(2) ?, c = 12.2765(2) ?, β = 104.607(1)°, V = 1775.47(5) ?³ and Z = 4. The structure has been solved using direct methods and refined by least-squares analysis [R ₁ = 0.0381, wR ₂ = 0.1082]. The crystal structure of the title compound is built from isolated [Mn(H₂O)₆]²⁺ octahedral cations, 1,4-diaza-bicyclo[2.2.2]octandiium cations (C₆H₁₄N₂)²⁺ and sulfate anions (SO₄)²⁻ connected by a three-dimensional hydrogen-bond network. The thermal decomposition of the precursor, studied by thermogravimetry and temperature-dependent X-ray powder diffraction, proceeds through four stages giving rise to the mixture of Mn₂O₃and Mn₃O₄. Supplementary Material CCDC 620298 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.     

Crystal and Molecular Structures of C6H5CH2SOCH2CONHCH2C6H5 and C6H5SOCH2CON(iC3H7)2

Abstract  The crystal structures for two of the ligands C₆H₅CH₂SOCH₂CONHCH₂C₆H₅ (1) and C₆H₅SOCH₂CON(ⁱC₃H₇)₂ (2) have been determined by X-ray diffraction. These compounds crystallize in orthorhombic system with space groups and cell parameters, Pca21(no. 29), a = 8.4600(5) ?, b = 5.3534(5) ?, c = 32.136(2) ?, V = 1455.42(15) ?³ and Pna21(no. 33) a = 17.5563(11) ?, b = 5.7902(4) ?, c = 14.2866(9) ?, V = 1452.30(16) ?³, respectively. These molecules are stabilized in solid state by various intra and intermolecular hydrogen bonding interactions to give polymeric structures. The reported IR spectra of these compounds in solid state could be explained on the basis of the observed intermolecular hydrogen bonding interactions. Index Abstract  The title compounds C₆H₅CH₂SOCH₂CONHCH₂C₆H₅ (1) and C₆H₅SOCH₂CON(ⁱC₃H₇)₂ (2) were prepared by the oxidation of corresponding sulfides with H₂O₂/SeO₂ in methanol and their structures were determined. The structures show that the SO and CO groups are having “anti” configuration in 1 and “syn” configuration in 2. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis and crystal structures of two copper(I) π-complexes with 1-allyloxybenzotriazole of CuBr?C6H4N3(OC3H5) and 2CuCl?C6H4N3(OC3H5) compositions

Both compounds of CuBr⋅C₆H₄N₃(OC₃H₅) (sp. gr. P1, a = 7.633(1) Å, b = 9.987(1) Å, c = 14.898(2) Å, α = 104.75(1)^∘, β = 94.76(1)^∘, γ = 106.90(1)^∘) (I) and 2CuCl⋅C₆H₄N₃(OC₃H₅) (sp. gr. Cc, a = 11.2483(4) Å, b = 16.7076(6) Å, c = 7.2948(3) Å, β = 118.612(2)^∘) (II) composition were prepared by alternating-current electrochemical synthesis. In I due to a bridging function of organic moieties 16-membered cycles appear which are combined into ribbons {Cu₂Br₂[(C₆H₄N₃(OC₃H₅)]₂}_n. Each of two crystallographically independent copper atom possesses a trigonal-pyramidal arrangement with different degree of tetrahedral distortion. Distinctive numbers of hydrogen bonds around Br1 and Br2 atoms cause rather appreciable distinctions in copper–olefinic bond interaction effectiveness for each metal atom. In II Cu₂Cl₂ rhombs are joined to infinite chains oriented along [010] direction. Each ligand molecule is also coordinated through the C=C—bond of the allylic group to copper atom of one inorganic chain and through the nitrogen atom to a metal atom belonging to another copper-halide chain. Cu1 atoms is tetrahedrally surrounded by three chlorine atoms and nitrogen one, whereas a trigonal-planar arrangement of Cu2 atom is formed by two halogen atoms and slightly disordered olefinic group.     

Growth and shape control of orthorhombic Fe5(PO4)4(OH)3·2H2O single crystalline dendrites

Orthorhombic Fe₅(PO₄)₄(OH)₃·2H₂O single crystalline dendritic nanostructures have been synthesized by a facile and reproducible hydrothermal method without the aid of any surfactants. The influences of synthetic parameters, such as reaction time, temperature, the amount of H₂O₂ solution, pH values, and types of iron precursors, on the crystal structures and morphologies of the resulting products have been investigated. The formation process of Fe₅(PO₄)₄(OH)₃·2H₂O dendritic nanostructures is time dependent: amorphous FePO₄·nH₂O nanoparticles are formed firstly, and then Fe₅(PO₄)₄(OH)₃·2H₂O dendrites are assembled via a crystallization-orientation attachment process, accompanying a color change from yellow to green. The shapes and sizes of Fe₅(PO₄)₄(OH)₃·2H₂O products can be controlled by adjusting the amount of H₂O₂ solution, pH values, and types of iron precursors in the reaction system.     

Crystal structure of a new basic nitrate of neodymium(III), [Nd6O(OH)8(H2O)14(NO3)6](NO3)2 · 2H2O

A new basic Nd³⁺ nitrate, [Nd₆O(OH)₈(H₂O)₁₄(NO₃)₆](NO₃)₂ · 2H₂O (I), is isolated in the crystal form and studied. Compound I differs from the basic Ln nitrates containing [Ln ₆O(OH)₈] clusters in that it involves a larger number of water molecules. The incorporation of additional water molecules is accompanied by changes in the coordination environment of one of the three crystallographically independent Nd³⁺ cations. Two cations have coordination polyhedra in the form of a monocapped tetragonal antiprism with a coordination number of 9, and the third cation has a polyhedron in the form of a bicapped tetragonal antiprism with a coordination number of 10. Original Russian Text ? I.A. Charushnikova, C. Den Auwer, 2007, published in Kristallografiya, 2007, Vol. 52, No. 2, pp. 248–251.     

Reaction mechanism of silicon Cat-CVD

Reaction kinetics for the silicon catalytic chemical vapor deposition (Cat-CVD) has been investigated. SiH₃ and Si₂H₂ are expected to be important precursors in the Si film growth. However, the reactivity of Si₂H₂ to the film surface was not well understood. Quantum chemical calculations have been performed for the adsorption of Si₂H₂ and H₂SiSiH₂ on the Si(1 0 0)-2 × 1 surface with and without the hydrogen termination. It was found that there was no activation barrier for the Si₂H₂ adsorption on the bare Si(1 0 0) surface. The chemical kinetic model for the Si Cat-CVD process was modified according to these quantum chemical calculations. Results of kinetic simulations were compared to the experimental results. It is suggested that there is a correlation between the film quality and the concentration of Si₂H₂.     

Influence of P2O5 content on the structure of SiO2-Na2O-CaO-P2O5 bioglasses by Si and P MAS-NMR

²⁹Si and ³¹P MAS-NMR has been used in order to study the influence of P₂O₅ content on the structure of SiO₂-Na₂O-CaO-P₂O₅ bioglasses. The ²⁹Si NMR spectra show many Q_Siⁿ entities co-existing in the same glass. For all the glasses, the Q_Siⁿ species are associated with Ca²⁺ and Na⁺. The glass network becomes more and more polymerized when the P₂O₅ content increases. The ³¹P NMR spectra show that the phosphorus is present as monophosphate with or without diphosphate complexes associated with both Ca²⁺ and Na⁺. The increase in phosphorus content modifies the relative abundance of phosphate complexes and leads to changes in the chemical environment around phosphate indicating that the distribution of cations is not homogeneous. Indeed most phosphate complexes attract calcium. The percentage of diphosphate complexes increases with the P₂O₅ content as the silicate network repolymerizes.     

Structural change of liquid Si15Te85 and Si20Te80 with temperature: Ab initio molecular dynamics simulations

Using ab initio molecular dynamics simulations, the structural and electronic properties of liquid Si₁₅Te₈₅ and Si₂₀Te₈₀ at two temperatures were studied respectively. Compared with available experimental data, the calculated structure factors are acceptable. From symmetry arguments, the calculated partial bond-angle distribution functions suggest that with increasing temperature the extensive tetrahedral network structures persist longer in liquid Si₂₀Te₈₀ than those do in liquid Si₁₅Te₈₅. Our results indicate that the local tetrahedral structure around Si atoms and the Peierls-like distorted local atomic structure around Te atoms both play important roles in the structural change of liquid Si₂₀Te₈₀ and Si₁₅Te₈₅, which also suggest that the mechanisms of the structural change upon cooling in liquid Si₂₀Te₈₀ and Si₁₅Te₈₅ are of no essential difference. The results of DOS and LDOS indicate that the variation of the dip in DOS at E_F mainly results from the change of Te p orbitals.     

Synthesis, Spectroscopic Characterization and Crystal Structure of a New Acetyl phosphorylamidate P(O)[NHC(O)C6H4(4-NO2)][N(CH(CH3)2)(CH2C6H5)]2

Abstract  

A new acetyl phosphorylamidate P(O)[NHC(O)C₆H₄(4-NO₂)][N(CH(CH₃)₂)(CH₂C₆H₅)]₂ has been synthesized and characterized by elemental analysis, ¹H, ¹³C and ³¹P NMR, IR and single crystal X-ray diffraction. Single crystal X-ray analysis shows that it belongs to triclinic system, space group P[`1] P\bar{1} , with a = 10.5868(16) Å, b = 11.8058(18) Å, c = 12.4364(19) Å, α = 65.410(3)°, β = 67.492(4)°, γ = 85.879(3)°, V = 1,298.6(3) Å³, and Z = 2. The intermolecular PO···HN hydrogen bond makes H-bonded dimer of molecule with Ci symmetry. In the crystal network, the dimers are aggregated in the chain arrays through π-stacking between p-NO₂–C₆H₄–C(O)–NH– moieties. Moreover, weak C–H···O and C–H···π interactions exist in the crystal network.     

Crystallization kinetics of the Zr61Al7.5Cu17.5Ni10Si4 alloy using isothermal DSC and TEM observation

The crystallization behavior and microstructure development of the Zr₆₁Al_7.5Cu_17.5Ni₁₀Si₄ alloy during annealing were investigated by isothermal differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. During isothermal annealing of the Zr₆₁Al_7.5Cu_17.5Ni₁₀Si₄ alloy at 703 K, Zr₂Cu crystals with an average size of about 5 nm were first observed during the early stages (30% crystallization) of crystallization by TEM. The Zr₂Cu crystal size increased with annealing time and attained an average size of 20 nm corresponding to the stage of 80% crystallization. In addition, the change in particle size with increasing annealing time exhibited a linear relationship between grain growth time and the cube of the particle size for the Zr₂Cu type crystalline phase. This indicates that the crystal growth of the Zr₆₁Al_7.5Cu_17.5Ni₁₀Si₄ alloy belongs to a thermal activated process of the Arrhenius type. The activation energy for the grain growth of Zr₂Cu is 155 ± 20 kJ/mol in the Zr₆₁Al_7.5Cu_17.5Ni₁₀Si₄ amorphous alloy. The lower activation energy for grain growth in compared to that for crystallization in Zr₆₅Cu₃₅ 440 kJ/mol crystal corresponds to the rearrangement of smaller atoms in the metallic glass, Al or Si (compare to Zr).     

A novel representative {[Rb1.94(H2O,OH)3.84](H2O)0.1}{Al4(OH)4[PO4]3} in the pharmacosiderite structure type

The crystal structure of a new synthetic aluminophosphate {[Rb_1.94(H₂O,OH)_3.84](H₂O)_0.1}{Al₄(OH)₄[PO₄]₃} synthesized under mild hydrothermal conditions (T = 280°C, P = 100 atm) in the Rb₂O-Al₂O₃-P₂O₅-H₂O system is determined using X-ray diffraction (Stoe IPDS diffractometer, λMoK _α, graphite monochromator, 2θ_max = 64.33°, R = 0.032 for 312 reflections). The main crystal data are as follows: a = 7.4931(6) ?, space group P 3m, Z = 1, and ρ_calcd = 2.76 g/cm³. It is shown that the synthesized compound belongs to the pharmacosiderite structure type with a characteristic mixed open microporous framework composed of octahedra and tetrahedra. A comparative crystal chemical analysis of related phases is performed, and the chemical compositions of promising absorbents, i.e., hypothetical compounds potentially possible in the structure type under consideration, are proposed. It is established that pharmacosiderite and rhodizite are homeotypic to each other. Original Russian Text ? O.V. Yakubovich, W. Massa, O.V. Dimitrova, 2008, published in Kristallografiya, 2008, Vol. 53, No. 3, pp. 442–449.     

Synthesis and X-ray diffraction study of complex neptunium(VI) potassium chromate K2[(NpO2)2(CrO4)3(H2O)] · 3H2O

The crystal structure of the K₂[(NpO₂)₂(CrO₄)₃(H₂O)] · 3H₂O compound was established. The structure consists of anionic layers [(NpO₂)₂(CrO₄)₃(H₂O)] _n ²ⁿ , between which K+ ions and crystallization water molecules are located. The coordination polyhedra of Np atoms are distorted pentagonal bipyramids. All chromate ions are bound in a tridentate-bridging fashion. __________ Translated from Kristallografiya, Vol. 49, No. 4, 2004, pp. 676–680. Original Russian Text Copyright ? 2004 by Grigor’ev, Fedoseev, Budantseva, Bessonov, Krupa.