Structure of adamantan-1-ammonium 1-adamantanecarboxylate

Adamantan-1-ammonium 1-adamantanecarboxylate, C₂₁H₃₃NO₂ (I) is a novel dispiro-type compound. Aminoadamantane derivatives, in which the spiro carbon atoms are part of heterocyclic rings, are of potential interest as biological active substances and antiviral agents. Complex (I) crystallizes in the centrosymmetric space group C2/c (No. 15) with eight molecules in the unit cell with a = 25.227(4), b = 6.527(1), c = 22.489(4) Å, and = 90.75(1)°. The two spiro units are a 1-adamantylammonium cation and a 1-adamantane carbonyloxy anion. The complex units are stabilized by a network of intermolecular carbonyloxy-to-amine hydrogen bonding and van der Waals cohesive forces. Germane bond lengths are: C—N = 1.479(9) and C—O (mean) = 1.25(2) Å.     

The crystal structure of 5-methyl-1-(octahydro-1-iodo-1H-1-inden-4-yl)-1H-tetrazole

The title compound is C₁₁H₁₇N₄I, F.W.=330.20, monoclinic, space groupP2₁/a,a=11.586(2),b=10.617(1),c=10.417(1) Å, =94.567(2)°,Z=4,F(000)=652, (MoK)=0.7107 Å, (MoK)=2.31 mm^–1,V=1277.31 Å₃,D _C=1.71 gcm^–3,D _m=1.70 gcm^–3. The structurewassolved by Patterson and Fourier methods and refined to anR value 0.031 for 1620 observed reflections. The connectivity and conformation of the addition product ofcis-1,5-cyclononadiene and iodine azide was determined by X-ray analysis. The reaction product contains a chair-conformation cyclohexane ring that iscis fused to a cyclopentane ring. The cyclopentane ring has an envelope conformation and an equatorially oriented iodine substituent. A planar tetrazole ring is axially substituted on the cyclohexane ring. The plane of the tetrazole ring makes a dihedral angle of 69.6° with the average plane of the carbon atoms of the cyclohexane ring.     

Structural Studies of 1:1 Quinone-Hydroquinone Complexes

The structures of the 1:1 quinone-hydroquinone complexes of 2-phenyl and of 2-(4′-chloro) phenylbenzoquinone have been studied by X-ray methods. A superficial study would indicate that the quinhydrones are centrosymmetric and belong to the space group P2₁/c. However, other evidence indicates that the true crystal structure may belong to either the space group P2₁ or to Pc, or that the crystal may contain regions that would coresspond to each of these two non-centrosymmetric space groups. Some possible consequences of such a structural arrangement are briefly discussed.     

Selective area growth of GaN microstructures on patterned (1 1 1) and (0 0 1) Si substrates

Selective MOVPE growth of GaN microstructure on silicon substrates has been investigated using SiO₂ mask having circular or stripe window. In case of (0 0 1)substrate, grooves with (1 1 1) facets at the sides were made by using the etching anisotropy of a KOH solution. On the (1 1 1) facets of patterned silicon substrate (or on the as opened window region of (1 1 1) substrate), growth of wurtzite GaN was performed, of which the c-axis is oriented along the 1 1 1 axis of silicon. The photoluminescence and X-ray diffraction analysis were performed to characterize the single crystal to reveal the effect of the growth conditions of the intermediated layer and the microstructure.     

Geometric modeling of homoepitaxial CVD diamond growth: I. The {1 0 0}{1 1 1}{1 1 0}{1 1 3} system

Plasma-assisted CVD homoepitaxial diamond growth is a process that must satisfy many stringent requirements to meet industrial applications, particularly in high-power electronics. Purity control and crystalline quality of the obtained samples are of paramount importance and their optimization is a subject of active research. In the process of such studies, we have obtained high purity CVD diamond monocrystals with unusual morphologies, namely with apparent {1 1 3} stable faces. This phenomenon has led us to examine the process of CVD diamond growth and build up a 3D geometrical model, presented here, describing the film growth as a function of time. The model has been able to successfully describe the morphology of our obtained crystals and can be used as a predictive tool to predetermine the shape and size of a diamond crystal grown in a given process configuration. This renders accessible control of desirable properties such as largest usable diamond surface area and/or film thickness, before the cutting and polishing manufacture steps take place. The two latter steps are more sensitive to the geometry of the growth sectors, which will be addressed in a companion paper.Our model, applicable to the growth of any cubic lattice material, establishes a complete mapping of the final morphology state of growing diamond, as a function of the growth rates of the crystalline planes considered, namely {1 0 0}, {1 1 1}, {1 1 0}, and {1 1 3} planes, all of which have been observed experimentally in diamond films. The model makes no claim as to the stability of the obtained faces, such as the occurrence of non-epitaxial crystallites or twinning. It is also possible to deduce transient behavior of the crystal morphology as growth time is increased. The model conclusions are presented in the form of a series of diagrams, which trace the existence (and dominance) boundaries of each face type, in presence of the others, and where each boundary crossing represent a topology change in terms of number of faces, edges and vertices. We validate the model by matching it against crystals published in the literature and illustrate its predictive value by suggesting ways to increase usable surface area of the diamond film.     

Charge Carrier Transport 1n 1:1 Complexes of Tetracyanobenzene with Naphthalene Anthracene and Durene

Abstract

It is well established that crystals of charge transfer (CT) complexes formed between aromatic donors and acceptors are built up of linear stacks of closely packed molecules. There are two main types of CT crystal structure, (i) a parallel arrangement of linear stacks made up of the individual component molecules, AAAA…DDDD… and (ii) a parallel arrangement of linear stacks made up of alternating molecules, ADADA… In each case it is to be expected that the intermolecular forces between the face to face packed molecules in each stack are far greater than those forces between stacks. A considerable anisotropy in physical properties which are a strong function of intermolecular interactions is a natural result of these crystal structures. Such anisotropy has been reported in the few crystals of the ADAD structure which have been examined, for example, in triplet exciton motion in biphenxl² and anthracene tetracyanobenzene (TCNB) complexes³,⁴ and in charge carrier mobilities μ in anthracene⁵ and phenthrene-pyromellitic-acid-dianhydride⁶ as well as anthracene-trinitrobenzene⁷. Carrier mobilities which were reported were all low, < 0.1 cm²/V sec., and though the major interesting questions were posed, such as what is the effect of different donors on μ?; or are there separate conduction and valence bands for acceptors and donors?; the dearth of mobility data on a range of materials leaves these questions unanswered. We have recently measured the mobilities of holes in several TCNB complexes as a first step towards understanding carrier transport in such materials. These are a particularly interesting series of materials in that triplet motion is said to be primarily two dimensional in anthracene TCNB³, and unidimensional in biphenyl TCNB². Since the transport of charge, like triplet exciton motion, is dominated by exchange interactions, and since CT triplet     

Investigation of preparation and properties of epitaxial growth GaN film on Si(1 1 1) substrate

In this paper, a single crystalline GaN grown on Si(1 1 1) is reported using a GaN buffer layer by a simple vacuum reactive evaporation method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence measurement (PL), and Hall measurement results indicate that the single crystalline wurtzite GaN was successfully grown on the Si(1 1 1) substrate. The surface of the GaN films is flat and crack-free. A pronounced GaN(0 0 0 2) peak appears in the XRD pattern. The full-width at half-maximum (FWHM) of the double-crystal X-ray rocking curve (DCXRC) for (0 0 0 2) diffraction from the GaN epilayer is 30 arcmin. The PL spectrum shows that the GaN epilayer emits light at the wavelength of 365 nm with an FWHM of 8 nm (74.6 meV). Unintentionally doped films were n-type with a carrier concentration of 1.76×10¹⁸/cm³ and an electron mobility of 142 cm³/V s. The growth technique described was simple but very powerful for growing single crystalline GaN films on Si substrate.     

Crystal and molecular structure of 1-amino-1-methylethylphosphonic acid monohydrate

The crystal and molecular structure of 1-amino-1-methylethylphosphonic acid monohydrate (C₃H₁₀NO₃P·H₂O) has been determined by single-crystal X-ray diffraction methods. The crystals are orthorhombic:Pna2₁,a=11.665(2),b=9.415(1),c=6.386(1) Å,Z=4. The structure was solved by the heavy-atom method and refined to a finalR=0.028. The molecule exists as a zwitterion, H ₃ ⁺ N-C-(CH₃)₂-PO₃₄H^–. There are six independent hydrogen bonds in the structure, three of the type N-HO with lengths 2.904(5), 2.745(6), and 2.765(5) Å and three of the type O-HO with lengths 2.754(4), 2.833 (7), and 2.548(5) Å.     

The 1:1 crystal complex of salicylic acid and urea

The 1∶1 crystal complex of salicylic acid (C₇H₆O₃) and urea (CH₄N₂O), mp 121° C, is monoclinic, with space groupC2/c (C ₂ ⁶ h, No. 15) and unit cell dimensionsa=22.206(3),b=5.108(1),c=17.177(2) Å,β=106.18(1)°.d _calc=1.407 g cm^?3,d _meas=1.41 g cm^?3 forZ=8. The structure was determined by direct methods and refined by a full-matrix least-squares procedure to giveR=0.057 andR _w =0.050 for 1652 integrated intensities above 2σ(I). The structure contains a strong OH?O hydrogen bond with O?O distance 2.54 Å in which the carboxyl OH group is donor and urea oxygen atom is acceptor. There are two NH?O intermolecular hydrogen bonds with N?O distances of 2.90 and 2.96 Å. Additionally, the salicyclic acid contains an intramolecular OH?O hydrogen bond of 2.56 Å.     

Crystal of Tetrakis(1-ethyl-1H-imidazole)diisothiocyanatocopper(II) bis(1-ethyl-1H-imidazole)diisothiocyanatocopper(II)

Abstract  A new complex [Cu(NCS)₄ (N-Eim)₄] [Cu(NCS)₂ (N-Eim)₂] (where N-Eim = N-ethylimidazole) has been synthesized and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the Triclinic space group P−1 with the parameters: a = 8.7707(18) ?, b = 10.712(2) ?, c = 13.511(3) ?, α = 104.73(3)°, β = 104.84(3)°, γ = 102.52(3)°, V = 1131.54(3) ?³, with Z = 1 formula units. In the structure, the copper atoms all assume an elongated octahedral geometry with two distinct coordination environments; one is coordinated by four N-ethyl-imidazole ligands and two axial SCN groups, and another by two SCN groups and two N-ethyl-imidazole ligands. The two units form one infinite 1D zigzag chain along the [1 0 1] plane by two thiocyanate ligands from the [Cu(NCS)₄ (N-Eim)₄] units. Index Abstract  The title compound, tetrakis(1-ethyl-1H-imidazole)diisothio cyanatocopper(II) bis(1-ethyl-1H-imidazole)diisothiocyanatocopper(II) has been synthesized and structurally characterized by single-crystal X-ray diffraction. In the structure, the copper atoms all assume an elongated octahedral geometry with two distinct coordination environments. The two units form one infinite 1D zigzag chain along the [1 0 1] plane by two thiocyanate ligands from the [Cu(NCS)₄ (N-Eim) 4] units.      

Epitaxial growth of MgO films on Si(1 1 1) by metal organic chemical vapor deposition

Epitaxial MgO films were grown on Si(1 1 1) substrates at 800°C using methylmagnesium tert-butoxide (MeMgO^tBu) as a single precursor under high-vacuum conditions (5×10⁻⁶ Torr). The crystalline structure, morphology, and chemical composition of the deposited films were investigated by X-ray diffraction, X-ray pole figure analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results show that epitaxial MgO films with correct stoichiometry can be deposited on Si(1 1 1) at 800°C. The single precursor methylmagnesium tert-butoxide has been found suitable for the epitaxial growth of MgO on Si(1 1 1) substrates.     

Isolation and crystal structures of triethylenediamine-hydroquinone (1/1) and triethylenediamine-phenol (1/2)

Two crystalline adducts of triethylenediamine with hydroquinone [N(CH₂CH₂)₃N·C₆H₄(OH)₂,I] and phenol [N(CH₂CH₂)₃N·2C₆H₅OH,II] have been isolated and characterized by X-ray analysis. ComplexI crystallizes in the monoclinic space groupC2/c, witha=11.944(2),b=9.491(2),c=11.986(2) Å,=121.70(1)°, andZ=4. Both molecular components occupy sites of symmetry 2, and are linked alternately by N H-O hydrogen bonds to form infinite zigzag chains. Crystals ofII are also monoclinic, with space groupP2₁/c,a=12.987(2),b=6.376(1),c=21.350(3) Å,=106.94(1)°, andZ=4. The structure is composed of discrete hydrogen-bonded molecular aggregates corresponding to the stoichiometric formula. The triethylenediamine moieties in both adducts closely approximate to the idealizedD ₃ h conformation. The structures have been refined toR values of 0.097 (I) and 0.092 (II) using, respectively, 479 and 1580 observed MoK data.     

Direct observation of sublimation process on a CdTe(1 1 1) surface using an ultrafine particle

A particle with a CdTe core and carbon mantle was produced by the advanced carbon-coating method which enables direct coverage with a carbon layer using an electron microscope. The coagulated particles containing approximately 30–200 CdTe particles produced by the gas evaporation method were covered with a carbon layer of about 7 nm thickness at 300°C. By heating these particles above 500°C, the sublimation process of a part of the CdTe particle can be directly captured by high-resolution transmission electron microscopy and recorded in real time on videotape. Sublimation on the CdTe(1 1 1) surfaces occurred in the step flow mode of two (1 1 1) layers. It was observed that two (1 1 1) zinc-blende layers changed to the (0 0 0 2) würtzite configuration unit just before sublimation. The condensation of CdTe on the sublimated particle surface and growth of CdTe in the carbon layers were also captured in the video image. These sublimation processes were discussed in terms of the existence of the polarity of II–VI compounds.     

AlGaN photodetectors grown on Si(1 1 1) by molecular beam epitaxy

The fabrication and characterisation of Al_xGa_1−xN (0x0.35) photodetectors grown on Si(1 1 1) by molecular beam epitaxy are described. For low Al contents (<10%), photoconductors show high responsivities (10A/W), a non-linear dependence on optical power and persistent photoconductivity (PPC). For higher Al contents the PPC decreases and the photocurrent becomes linear with optical power. Schottky photodiodes present zero-bias responsivities from 12 to 5 mA/W (x=0−0.35), a UV/visible contrast higher than 10³, and a time response of 20 ns, in the same order of magnitude as for devices on sapphire substrate. GaN-based p–n ultraviolet photodiodes on Si(1 1 1) are reported for the first time.     

Enhanced thermal stability of NiSi films on Si(1 1 1) substrates by a thin Pt interlayer

A thin interlayer of Pt can greatly enhance the thermal stability of NiSi films formed by rapid thermal annealing (RTA) on Si(1 1 1) substrates, as was revealed by X-ray diffraction (XRD) data and sheet resistance measurement. High-resolution transmission electron microscopy (HRTEM) reveals a well-defined interface between the Ni(Pt)Si film and the Si(1 1 1) substrate for the Ni/Pt/Si sample annealed at 640°C. The orientation relationship in this sample determined by selected area electron diffraction (SAED) was NiSi(1 0 0)||Si(1 1 1) and NiSi[0   0]||Si[0 1  ]. With the increase of temperature, the texture of NiSi films transform from NiSi(1 0 0)||Si(1 1 1) to NiSi(0 0 1)||Si(1 1 1). The reduction in the interfacial energy due to the formation of the (1 0 0) textured NiSi film is proposed as a possible reason for the improved thermal stability of NiSi and the transition in NiSi texture during high-temperature annealing. Detailed study on the XRD data combined with Auger electron spectra (AES) indicates PtSi and NiSi form a solid solution following Vegard's law, which adjusts the lattice constant ratio c/b to and may account for the texture of NiSi(1 0 0)||Si(1 1 1).     

Etch pits of precipitates in CdZnTe crystals on (1 1 1) B surface

The etch pits of Te-rich and Cd-rich precipitates of the Cd_0.94Zn_0.04Te crystals situated on (1 1 1) B surface were distinguished from the dislocation etch pits and evaluated by using Everson Etching for the first time. By using an IR transmission microscope and a scanning electron microscope (SEM) with an energy-dispersive x-ray spectroscopy (EDX) analytical system, the characteristics of the precipitate etch pits were studied. The etch pit of the Te-rich precipitate which would influence the etch rate of its ambient materials shows the shape of triangle or hexagon with a rough surface different from the cone-shaped triangle etch pit as the dislocation etch pit. The etch pit of the Cd-rich precipitate is always enwrapped by large quantities of dislocation etch pits, which indicates the existence of the damaged layers around the Cd-rich precipitate. Base on the characteristics of the precipitate etch pits, the areal densities of the precipitates with the size larger than 5 μm on the substrate surfaces can be measured by the optical microscope with a magnification of 50 and under Nomarski mode. Compared with the conventional measurement method based on the IR transmission microscope (IRTM), the method of the etch pit observation (EPO) is more practical for measuring the areal densities of the precipitates of CdZnTe substrates.     

The Growth and Properties of K1-yLiyTa1-xNbxO3 Crystal

Potassium lithium tantalate niobate (K_1-yLi_yTa_1-xNb_xO₃, KLTN) crystals with tetragonal phase at room temperature were grown by the flux pulling method. Two-wave coupling energy transfer has been realized in this crystal. The two-wave coupling gain coefficient measured is 0.46 cm⁻¹, and the sign of the dominant carrier is positive. As compared with potassium tantalate niobate (KTN), the dielectric properties of KLTN changed significantly.     

Heteroepitaxial growth of InN layers on (1 1 1) silicon substrates

Indium nitride (InN) layers were grown on (1 1 1) silicon substrates by reactive magnetron sputtering using an indium target. Atomic force microscope, X-ray diffraction, and Raman spectroscopy analysis revealed that highly c-axis preferred wurtzite InN layers with very smooth surface can be obtained on (1 1 1) silicon substrates at a substrate temperature as low as 100 °C. The results indicate that the reactive sputtering is a promising growth technique for obtaining InN layers on silicon substrates at low substrate temperature with low cost and good compatibility with microelectronic silicon-based devices.