MOCVD growth and optical properties of non-polar (1 1–2 0) a-plane GaN on (1 0–1 2) r-plane sapphire substrate

Non-polar a-plane GaN film with crystalline quality and anisotropy improvement is grown by use of high temperature AlN/AlGaN buffer, which is directly deposited on r-plane sapphire by pulse flows. Compared to the a-plane GaN grown on AlN buffer, X-ray rocking curve analysis reveals a remarkable reduction in the full width at half maximum, both on-axis and off-axis. Atomic force microscopy image exhibits a fully coalesced pit-free surface morphology with low root-mean-square roughness (∼1.5 nm). Photoluminescence is carried out on the a-plane GaN grown on r-plane sapphire. It is found that, at low temperature, the dominant emission at ∼3.42 eV is composed of two separate peaks with different characteristics, which provide explanations for the controversial attributions of this peak in previous studies.     

Synthesis and structure–property relations in xCuO–(1 − x)Bi2O3 (0.5 ⩽ x ⩽ 0.9) (C1–C5: x = 0.5, 0.6, 0.7, 0.8, 0.9) glasses

Synthesis of the xCuO–(1 ? x)Bi₂O₃ (0.5 ? x ? 0.9) (C1–C5: x = 0.5, 0.6, 0.7, 0.8, 0.9) glasses was done via nitrate–citrate gel route. Glassy phase is ascertained by XRD studies. Magnetic susceptibility results in the range 4.2–400 K show weak paramagnetic nature with exchange integrals ～0.024–0.13 eV in the glasses. The electron paramagnetic resonance (EPR) in the range 4.2–363 K shows g ≈ 2.0 and the trend of the g-matrix elements g_|| > g_⊥ > g_e for the glasses C1–C5 at 4.2 K are due to the Cu²⁺ (3d⁹) paramagnetic site in the glasses which is in a tetragonally elongated octahedron [O_1/2–CuO_4/2–O_1/2] having D_4h symmetry. IR spectroscopic results show the presence of octahedron [BiO_6/2]^3? and [CuO_6/2]^4? units and pyramidal [BiO_2/2O]^? unit in the glasses.     

Epitaxial lateral overgrowth of non-polar GaN(1 1̄ 0 0) on Si(1 1 2) patterned substrates by MOCVD

m-Plane GaN was grown selectively by metal–organic chemical vapor deposition (MOCVD) on patterned Si(1 1 2) substrates, where grooves aligned parallel to the Si〈1 1 0〉 direction were formed by anisotropic wet etching to expose the vertical Si{1 1 1} facets for growth initiation. The effect of growth conditions (substrate temperature, chamber pressure, and ammonia and trimethylgallium flow rates) on the growth habits of GaN was studied with the aim of achieving coalesced m-plane GaN films. The epitaxial relationship was found to be GaN(1 1? 0 0) || Si(1 1 2), GaN[0 0 0 1] || Si[1 1 –1], GaN[1? 1? 2 0] || Si[1 1? 0]. Among all growth parameters, the ammonia flow rate was revealed to be the critical factor determining the growth habits of GaN. The distribution of extended defects, such as stacking faults and dislocations, in the selectively grown GaN were studied by transmission electron microscopy in combination with spatially resolved cathodoluminescence and scanning electron microscopy. Basal-plane stacking faults were found in the nitrogen-wing regions of the laterally overgrown GaN, while gallium-wings were almost free of extended defects, except for the regions near the GaN/Si{1 1 1} vertical sidewall interface, where high dislocation density was observed.     

Growth of Sm1 – ySryF3 – y (0 < y ≤ 0.31) Crystals and Investigation of Their Properties

Crystallography Reports - Sm1&nbsp;–&nbsp;ySryF3&nbsp;–&nbsp;y (0 &lt; y ≤ 0.31) crystals have been grown from melt by directional solidification in a...     

Incorporation of group III,IV and V elements in 3C–SiC(1 1 1) layers grown by the vapour–liquid–solid mechanism

We report on a comparative investigation of the incorporation of group III, IV and V impurities in 3C–SiC heteroepitaxial layers grown by the vapour–liquid–solid (VLS) mechanism on on-axis α-SiC substrates. To this end, various Si-based melts have been used with addition of Al, Ga, Ge and Sn species. Homoepitaxial α-SiC layers grown using Al-based melts were used for comparison purposed for Al incorporation. Nitrogen incorporation depth profile systematically displays an overshoot at the substrate/epilayer interface for all the layers. Ga and Al incorporations follow the same distribution shape as N whereas this is not the case for the isoelectronic impurities Ge and Sn. This suggests some interaction between Ga/Al and N coming from the high bonding energy between the group III and V elements, which does not exist with Ge and Sn. This is why both incorporate as a cluster. A model of incorporation is proposed taking into account metal-N and metal-C bonding energies together with the solid solubility of the corresponding nitrides.     

Growth of Pb on Si(3 3 5)–Au surface

The growth, crystallographic structure and electronic properties of ultrathin Pb films grown on a vicinal silicon surface are investigated with reflection high energy electron diffraction (RHEED) and specific resistivity measurement techniques. A Si(3 3 5) surface with a perfect distribution of monoatomic steps separated with (1 1 1) terraces induced by a submonolayer amount of Au is used as a substrate. In the early stage, Pb growth is anisotropic. Apparently, the presence of steps forces the growth of short crystalline Pb chains along the steps. The layer is amorphous in the perpendicular direction. With the increasing thickness, a phase transition takes place between 3 and 4 monolayers (ML) that makes crystalline order also across the terraces. A further increase in thickness causes the layer surface to repeat the substrate morphology. It consists of regularly distributed monoatomic steps and narrow (1 1 1) terraces.     

Ravil Vagizovich Galiulin (January 1, 1940–February 1, 2010)

Obituaries

Ravil Vagizovich Galiulin (January 1, 1940–February 1, 2010)     

Growth and structure properties of La1−xSrxMnO3−σ (x=0.2, 0.3, 0.45) thin film grown on SrTiO3 (0 0 1) single-crystal substrate by laser molecular beam epitaxy

La_1−xSr_xMnO_3−σ (LSMO) thin films have been grown on SrTiO₃ (0 0 1) single-crystal substrates using the laser molecular beam epitaxy (MBE) technique. The two-dimensional layer-by-layer growth was in-situ monitored by reflection high-energy electron diffraction (RHEED). Kinetic growth with surface relaxation was also observed, and crystallinity of the thin films was investigated by high-resolution X-ray diffraction. Results of 2θ−ω scans revealed a strong correlation between out-of-plane lattice constant and oxygen content as well as strontium doping concentration. However, further analysis of rocking curve measurements around (0 0 2) plane of thin films grown under different oxygen pressure (P_O2) shown the effects of oxygen content on the crystal structure. An exceptionally low full-width at half-maximum (FWHM) of 0.02° was measured from the sample grown at P_O2 of 5.0 Pa, indicating the almost perfect epitaxial growth of LSMO thin films.     

Synthesis and Crystal Structure of (PzCH<Subscript>2</Subscript>CHOHCH<Subscript>2</Subscript>PzH)·(Ph<Subscript>2</Subscript>SnCl<Subscript>3</Subscript>) (Pz = 3,5-dimethylpyrazol-1-yl)

Abstract  

Reaction of Ph₂SnCl₂ with 1,3-bis(3,5-dimethylpyrazol-1-yl)-2-propanol (L) in a 1:1 ratio yields L(SnPh₂Cl₂)₂ adduct, which partly hydrolyzes to the title complex (C₂₅H₃₁Cl₃N₄OSn, Mr = 628.58) during crystal growing in the air. The title complex is of monoclinic, space group P2₁/n with a = 9.0338(9), b = 17.890(1), c = 17.340(1) ?, β = 95.533(1)^o, V = 2798.9(5) ?³, Z = 4, Dc = 1.492 Mg/m³, λ(MoKα) = 0.71073 ?, μ = 1.224 mm⁻¹, F(000) = 1272, R = 0.023, wR = 0.054 for 4212 observed reflections with I ≥ 2σ(I). The crystal structure indicates that there is no direct interaction between the pyrazolyl ligand and the tin atom, but this complex forms a supramolecular structure through weak intermolecular C–H⋯Cl and O–H⋯Cl hydrogen bonds.     

Lewis Acid–Base Adduct Me3Sb–Ga(t-Bu)3

Abstract  

The simple Lewis acid–base adduct Me₃Sb–Ga(t-Bu)₃ 1 was prepared by reaction of t-Bu₃Ga and SbMe₃ in 1:1 M ratio. 1 was fully characterized by multinuclear NMR spectroscopy (¹H, ¹³C). In addition, its solid state structure was determined by single crystal X-ray diffraction studies. 1 is monoclinic, space group P2₁ /n with a = 8.4895(2) ?, b = 12.9303(4) ?, c = 17.9976(5) ?, β = 97.472(2)° and Z = 4.     

Nanostructured Crystals of Fluorite Phases Sr1 – xRxF2 + x (R Are Rare-Earth Elements) and Their Ordering. 15. Concentration Dependence of the Defect Structure of As Grown Nonstoichiometric Phases Sr1 – xRxF2 + x (R = Sm,Gd)

Crystallography Reports - The defect structure of as grown single crystals Sr1&nbsp;–&nbsp;xSmxF2&nbsp;+&nbsp;x (x = 0.14, 0.26) and...     

Base-Stabilized Monomeric Stibinoalane dmap–Al(Et<Subscript>2</Subscript>)Sb(<Superscript>t</Superscript>Bu)<Subscript>2</Subscript>

Abstract  

The six-membered heterocycle [Me₂AlSb(t-Bu)₂]₃ was reacted with the strong Lewis-base 4-dimethylaminopyridine (dmap), yielding the first completely alkyl-substituted monomeric complex dmap–Al(Me₂)Sb(t-Bu)₂ 1. 1 was characterized by NMR spectroscopy and single crystal X-ray diffraction. 1 is monoclinic, space group P2 ₁ /n with a = 9.9004(2) ?, b = 16.8166(3) ?, c = 13.8400(3) ?, β = 100.746(1)° and Z = 4.     

Synthesis and Crystal Structure of Mixed-valence Hexanuclear Manganase Oxide Complex,Hexakis(μ<Subscript>2</Subscript>-pivalato)-tetrakis(μ<Subscript>3</Subscript>-pivalato)-mono(pyridine)-tris(pivalic acid)-bis(μ<Subscript>4</Subscript>-oxo)dimanganese(III) tetramanganase(II)

Abstract  The complex, [Mn₆O₂(OOCCMe₃)₁₀(HOOCCMe₃)₃(py)], has a hexanuclear structure with a Mn₆O₂ core. This complex crystallizes in the monoclinic space group P2₁/n with a = 17.757(5) ?, b = 27.413(5) ?, c = 22.348(5) ?, β = 90.233(5)°, V = 9,040(4) ?³ and Z = 4. It contains a [Mn₆O₂]¹⁰⁺ core that can be described as two edge-sharing Mn₄ tetrahedra at the centre of each of which tetrahedron lies a μ₄-O²⁻ ion. All Mn atoms are six-coordinate and possess distorted octahedral geometry. Mn₄ exhibits butterfly arrangement with both μ₄-O atoms on the same side of the molecule. The complex is mixed-valence , and the Mn^III centers are assigned as the two central metal ions bridged by two O²⁻ ions. Index abstract  The complex, [Mn₆O₂(OOCCMe₃)₁₀(HOOCCMe₃)₃(py)], has a hexanuclear structure with a Mn₆O₂ core. This complex crystallizes in the monoclinic space group P2₁/n with a = 17.757(5) ?, b = 27.413(5) ?, c = 22.348(5) ?, β = 90.233(5)°, V = 9040(4) ?³ and Z = 4. It contains a [Mn₆O₂]¹⁰⁺ core that can be described as two edge-sharing Mn₄ tetrahedra at the centre of each of which tetrahedron lies a μ₄-O²⁻ ion. All Mn atoms are six-coordinate and possess distorted octahedral geometry. Mn₄ exhibits butterfly arrangement with both μ₄-O atoms on the same side of the molecule. The complex is mixed-valence , and the Mn^III centers are assigned as the two central metal ions bridged by two O²⁻ ions.      

The Crystal-Chemical Features of Phases and the Nature of the Coordination Bond in the System [CuxNi(1 – x){N(CH2PO3)3}]Na4 · nH2O (x = 0–1)

Crystallography Reports - The structural features of the phases formed during crystallization of mixed copper and nickel complexes with nitrilotris(methylenephosphonic acid)...     

(Na1/2Bi1/2)TiO3-(Na1/2Bi1/2)(Zn1/3Nb2/3)O3无铅压电陶瓷的介电特性研究

采用固相合成法制备了(1-x)(Na1/2Bi1/2)TiO3-x(Na1/2Bi1/2)(Zn/23Nb2/3)O3(简写为(1-x)NBT-xNBZN)无铅压电陶瓷.研究了该体系陶瓷晶体结构、弥散相变特征与介电弛豫行为.X射线衍射分析表明,所研究的组成均能够形成纯钙钛矿(ABO3)型固溶体.当x≥0.5%摩尔分数时,该体系陶瓷具有三方、四方共存的晶体结构.材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm.修正的居里-外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随x的增加而增加.x≤0.5%摩尔分数的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随x的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性.根据有序-无序转变和宏畴.微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理.     

Synthesis and Structure of a One-Dimensional Copper(II)–Potassium(I) Complex of (<Emphasis Type="Italic">S</Emphasis>)-2-Hydroxy-3-Phenylpropanoic acid

Abstract  

Evaporation of the mixture solution of Cu(ClO₄)₂·6H₂O, KOH and (S)-2-hydroxy-3-phenylpropanoic acid affords a Cu(II)–K(I) coordination compound 1. Single-crystal X-ray diffraction analysis reveals that 1 is a one-dimensional comb-like coordination polymer in the P2₁2₁2₁ space group with crystal cell parameters a = 10.989(2) ?, b = 15.939(3) ?, c = 22.511(5) ?, V = 3943(1) ?³ and Z = 4.     

Synthesis and Crystal Structure of a Cyanido-Bridged Bimetallic Copper(II)–Silver(I) Complex of Imidazole and [Ag(CN)<Subscript>2</Subscript>]<Superscript>−</Superscript>: [Cu(Imidazole)<Subscript>4</Subscript>{Ag(CN)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

Abstract  

A cyanido-bridged Cu(II)–Ag(I) bimetallic complex, [Cu(Imidazole)₄{Ag(CN)₂}₂] has been prepared and structurally characterized. The compound crystallizes in the orthorhombic space group Pmna. The crystal structure of the complex consists of trinuclear molecules made up of one [Cu(Imidazole)₄]⁺² and two [Ag(CN)₂]⁻ units. The trinuclear molecules are interlinked to each other through N–H–N and C–H–N hydrogen bonds. The Cu(II) ions are located on mirrors and assume distorted octahedral geometry with the basal plane consisting of four imidazole N-atoms.