X-ray diffraction, Raman, and photoacoustic studies of ZnTe nanocrystals

Abstract

Nanocrystalline ZnTe was prepared by mechanical alloying. X-ray diffraction (XRD), energy dispersive spectroscopy, Raman spectroscopy, and photoacoustic absorption spectroscopy techniques were used to study the structural, chemical, optical, and thermal properties of the as-milled powder. An annealing of the mechanical alloyed sample at 590 °C for 6 h was done to investigate the optical properties in a defect-free sample (close to bulk form). The main crystalline phase formed was the zinc-blende ZnTe, but residual trigonal tellurium and hexagonal ZnO phases were also observed for both as-milled and annealed samples. The structural parameters, phase fractions, average crystallite sizes, and microstrains of all crystalline phases were obtained from Rietveld analyses of the X-ray patterns. Raman results corroborate the XRD results, showing the longitudinal optical phonons of ZnTe (even at third order) and those modes of trigonal Te. Nonradiative surface recombination and thermal bending heat transfer mechanisms were proposed from photoacoustic analysis. An increase in effective thermal diffusivity coefficient was observed after annealing and the carrier diffusion coefficient, the surface recombination velocity, and the recombination time parameters remained the same.

ZnTe nanocrystal formation and growth control on UV-transparent substrate

“…The Raman transitions near 108, 216, 283, 323, 428, and 644 cm À1 correspond, respectively, to the normal phonon modes: (i) second order transverse acoustic (2TA) [19][20][21], (ii) first order longitudinal optical (1LO) [2,11,12,[19][20][21], (iii) second order longitudinal acoustic (2LA) [19][20][21], (iv) third order transverse/longitudinal optical coupled to the first order longitudinal acoustic (TO/LO + LA) [19,20] (v) second order longitudinal optic (2LO) [2,11,12,19,21,22], and (vi) third order longitudinal optic (3LO) [2,11]. It should be noted that this new PZABP matrix not only allows ZnTe NC growth but is also UV-transparent.…”

“…ZnTe has also attracted much attention because of its very high electro-optic coefficient and dielectric constant in the terahertz range -properties which can be advantageous as electro-optic field detectors [4,6,9,10]. Until now, ZnTe nanostructures have been synthesized by different techniques such as thermal evaporation, hot wall evaporation, radio frequency cathodic evaporation, solvothermal processes, molecular beam epitaxy [2,6,[11][12][13] and colloidal solutions [5,14]. Most of these ZnTe structures have been obtained in the form of monocrystalline nanowires [6,9] and, more recently, nanocrystals [5].…”

“…Due to its wide energy gap (2.26 eV) at room temperature [2][3][4][5], ZnTe is attractive for the manufacture of optoelectronic devices such as light emitting diodes, green-range laser diodes [6,7], electrochemical solar photocells [8,9] and efficient, phosphorus based displays. ZnTe has also attracted much attention because of its very high electro-optic coefficient and dielectric constant in the terahertz range -properties which can be advantageous as electro-optic field detectors [4,6,9,10].…”

Structural Characterization of ZnTe Grown by Atomic-Layer-Deposition Regime on GaAs and GaSb (100) Oriented Substrates

“…This breakdown is attributed to the generation of structural defects as misfit dislocation in the layer-substrate interface, inhomogeneity and other crystallinity problems originated from compositional fluctuations and by elastic scattering from ionized impurities. The peak observed at 208 to 211 cm -1 is associated to the ZnTe longitudinal optical (LO) phonon peak [19][20][21][22][23][24][25][26] , details of this peak are presented in . The peaks at 274 to 290 cm -1 are composed by the TO-GaAs and LO-GaAs vibrational modes, originated from the GaAs substrate, because of the penetration depth of laser light is larger than the ZnTe layer thickness and reaches the substrate, so the Raman spectra exhibit peaks related to the substrate characteristics.…”

Dilute magnetism in Zn1−xMnxTe nanocrystals grown in a glass template

“…These structures are also good candidates for quantum computation, spin filters and quantum information, and other spintronic devices [2][3][4]. In this context, ZnTe and Zn 1Àx Mn x Te semiconductors, with or without quantum confinement properties, have been synthesized by various methods, such as mechanical alloying [5], colloidal [6], hot wall epitaxy [7], and molecular beam epitaxy [1,8,9]. This Letter provides evidence of Zn 1Àx Mn x Te NC growth, synthesized by fusion in a glass template allowing control of optical, morphological and magnetic properties as a function of magnetic ion concentration, x.…”