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Hafnium germanium telluride
Gyung-Joo Jang,Hoseop Yun
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808011380
Abstract: The title hafnium germanium telluride, HfGeTe4, has been synthesized by the use of a halide flux and structurally characterized by X-ray diffraction. HfGeTe4 is isostructural with stoichiometric ZrGeTe4 and the Hf site in this compound is also fully occupied. The crystal structure of HfGeTe4 adopts a two-dimensional layered structure, each layer being composed of two unique one-dimensional chains of face-sharing Hf-centered bicapped trigonal prisms and corner-sharing Ge-centered tetrahedra. These layers stack on top of each other to complete the three-dimensional structure with undulating van der Waals gaps.
Magnetoelastic Effects in Iron Telluride  [PDF]
I. Paul,A. Cano,K. Sengupta
Physics , 2010, DOI: 10.1103/PhysRevB.83.115109
Abstract: Iron telluride doped lightly with selenium is known to undergo a first order magneto-structural transition before turning superconducting at higher doping. We study the effects of magneto-elastic couplings on this transition using symmetry considerations. We find that the magnetic order parameters are coupled to the uniform monoclinic strain of the unit cell with one iron per cell, as well as to the phonons at high symmetry points of the Brillouin zone. In the magnetic phase the former gives rise to monoclinic distortion while the latter induces dimerization of the ferromagnetic iron chains due to alternate lengthening and shortening of the nearest-neighbour iron-iron bonds. We compare this system with the iron arsenides and propose a microscopic magneto-elastic Hamiltonian which is relevant for all the iron based superconductors. We argue that this describes electron-lattice coupling in a system where electron-electron interaction is crucial.
哀牢山变质带  [PDF]
地质学报 , 1960,
Abstract: 一、哀牢山南段地质简述(见图1)哀牢山延展于云南省红河的西南岸,西北向大理伸展?东南延长至越南境南。太古代时,哀牢山一带即形成了一个北西―南东向的狭长沉陷带;后来经过剧烈下沉,造成了巨厚的地槽沉积,并先后侵入了酸性、中性及基性等火成岩。至太古代后期发
Ellipsometric Studies on Silver Telluride Thin Films  [PDF]
M. Pandiaraman,N. Soundararajan,C. Kumar,R. Ganesan
Journal of Nano- and Electronic Physics , 2011,
Abstract: Silver telluride thin films of thickness between 45 nm and 145 nm were thermally evaporated on well cleaned glass substrates at high vacuum better than 10 – 5 mbar. Silver telluride thin films are polycrystalline with monoclinic structure was confirmed by X-ray diffractogram studies. AFM and SEM images of these films are also recorded. The phase ratio and amplitude ratio of these films were recorded in the wavelength range between 300 nm and 700 nm using spectroscopic ellipsometry and analysed to determine its optical band gap, refractive index, extinction coefficient, and dielectric functions. High absorption coefficient determined from the analysis of recorded spectra indicates the presence of direct band transition. The optical band gap of silver telluride thin films is thickness dependent and proportional to square of reciprocal of thickness. The dependence of optical band gap of silver telluride thin films on film thickness has been explained through quantum size effect.
4-(Dimethylamino)phenyl ethynyl telluride  [cached]
Joan Farran,Angel Alvarez-Larena,Joan F. Piniella,Mario V. Capparelli
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809009404
Abstract: The title compound, C10H11NTe, is the first organyl ethynyl telluride, R—Te—C[triple-bond]C—H, to be structurally characterized. In the L-shaped molecule, the aryl moiety, viz. Me2NC6H4Te, is almost perpendicular to the Te—C[triple-bond]C—H fragment. The Te—Csp2 bond [2.115 (3) ] is significantly longer than the Te—Csp bond [2.041 (4) ]. The Te—C[triple-bond]C group is approximately linear [Te—C—C = 178.5 (4)° and C[triple-bond]C = 1.161 (5) ], while the coordination at the Te atom is angular [C—Te—C = 95.92 (14)°]. In the crystal structure, there are Csp—H...N hydrogen bonds which are perpendicular to the CNMe2 group; the N atom displays some degree of pyramidalization. Centrosymmetrically related pairs of molecules are linked by Te...π(aryl) interactions, with Te...Cg = 3.683 (4) and Csp—Te...Cg = 159.1 (2)° (Cg is the centroid of the benzene ring). These interactions lead to the formation of zigzag ribbons which run along c and are approximately parallel to (110).
Bis[(4-methylphenyl)ethynyl] telluride
Ignez Caracelli,Julio Zukerman-Schpector,Jesus M. Pena,Hélio A. Stefani
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810006264
Abstract: The tellurium atom in the title bis-ethynyl telluride, Te(C9H7)2 or C18H14Te, is located on a crystallographic twofold axis, the C—Te—C angle being 92.23 (15)°. The dihedral angle between the rings is 87.27 (7)°. In the crystal structure, molecules are connected in chains parallel to the b axis and mediated by C—H...π interactions.
Cadmium Telluride (CdTe) Thin Film for Photovoltaic Applications  [PDF]
Sekhar Chandra Ray,Kaushik Mallick
International Journal of Chemical Engineering and Applications , 2013, DOI: 10.7763/ijcea.2013.v4.290
Abstract: Cadmium telluride (CdTe) thin films are prepared by the dip-coating deposition technique under atmospheric pressure at different temperature. The optical band gap obtained within the range 1.63-1.60 eV. Crystallite sizes are obtained from XRD that are dependent on composition (Cd/Te) and baking temperatures. Raman spectra confirms the presence of transverse (TO) and longitudinal (LO) optical phonons in the CdTe structure. Films are good photoconductive in nature and could be used in photovoltaic applications.
"Graphene-Like" Exfoliation of Atomically-Thin Bismuth Telluride Films  [PDF]
Desalegne Teweldebrhan,Vivek Goyal,Muhammad Rahman,Alexander A. Balandin
Physics , 2009,
Abstract: We report on graphene-like exfoliation of the large-area crystalline films and ribbons of bismuth telluride with the thicknesses of a few atoms. It is demonstrated that bismuth telluride, the most important material for thermoelectric industry, can be mechanically separated into its building blocks -[Te-Bi-Te-Bi-Te]- atomic five-folds with the thickness of ~1 nm and even further - to subunits with smaller thicknesses. The atomically-thin crystals can be structured into suspended crystalline ribbons providing quantum confinement in two dimensions. The quasi two-dimensional (2-D) crystals of bismuth telluride revealed high electrical conductivity. The proposed atomic-layer engineering of bismuth telluride opens up a principally new route for drastic enhancement of the thermoelectric figure of merit.
Thermoelectric properties of electrically gated bismuth telluride nanowires  [PDF]
Igor Bejenari,Valeriu Kantser,Alexander A. Balandin
Physics , 2009, DOI: 10.1103/PhysRevB.81.075316
Abstract: We theoretically studied the effect of the perpendicular electric field on the thermoelectric properties of the intrinsic, n-type and p-type bismuth telluride nanowires with the growth direction [110]. The electronic structure and the wave functions were calculated by solving self-consistently the system of the Schrodinger and Poisson equations using the spectral method. The Poisson equation was solved in terms of the Newton - Raphson method within the predictor-corrector approach. The electron - electron exchange - correlation interactions were taken into account in our analysis. In the temperature range from 77 to 500 K, the dependences of the Seebeck coefficient, thermal conductivity, electron (hole) concentration, and thermoelectric figure of merit on the nanowire thickness, gate voltage, and excess hole (electron) concentration were investigated in the constant relaxation-time approximation. The results of our calculations indicate that the external perpendicular electric field can increase the Seebeck coefficient of the bismuth telluride nanowires with thicknesses of 7 - 15 nm by nearly a factor of 2 and enhance ZT by an order of magnitude. At room temperature, ZT can reach a value as high as 3.4 under the action of the external perpendicular electric field for realistic widths of the nanowires. The obtain results may open up a completely new way for a drastic enhancement of the thermoelectric figure of merit in a wide temperature range.
Jan Przy?uski,Zbigniew Szcz?sny,Tomasz Wartanowicz
Bulletin of the Institute of Heat Engineering , 1977,
Abstract: The paper deals with experimental investigations on obtaining amorphous films of germanium telluride GeTe by means of vacuum vaporization, in oder to obtain stoichiometry of their composition. The existence of picrocrystals in the obtained GeTe films of an average thickness 5000 A was controlled with X rays by means of Bragg-Brentano dyphractometer method. The homogeneity of GeTe distribution in the films was examined by X radiation exciting directly the beam of primary electrons. The thermically initiated phase transformation of GeTe films from the shape accepted as amorphous according to the given structural investigations, to the crystalline shape proved possible the obtaining of amorphous films of GeTe under the described conditions of the investigation.
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