| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 98 === Crystals of Ga2(Se1-xTex)3 compounds with x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1 were grown by vertical Bridgman method. The crystalline phase and stoichiometry of these crystals were investigated by Field-Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD), Electron probe X-ray micro-analysis (EPMA) and Raman spectroscopy had been used to study the electronic structure of these compounds. The energy band gaps of Ga2(Se1-xTex)3 were examined by thermoreflecatcne (TR) measurements, absorption and photoluminescence (PL) measurements.
X-ray diffraction patterns, Field-Emission Scanning Electron Microscopy analysis and Electron probe X-ray micro-analysis confirmcd that as-grown crystals are single phase. It was found that the values of lattice constants increase as the composition x of tellurium in the ternary compounds is increased. The lattice constants, (a) could be fitted by the following equations: a(x) =5.4682 + 0.44x Å. Information on the bonding in the Ga2(Se1-xTex)3 crystals were obtained by measurements of Raman spectroscopy. Composition dependencies of the energy gap for the single phase crystals were evaluated. It was found that the energy gap varied linearly with tellurium content and the values of energy gap decrease as the composition x of tellurium in the ternary compounds is increased. The energy gap, Eg could be fitted by the following equations: Eg = 1.896 – 0.754x eV.
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