THE GROWTH AND POST HEAT TREATMENT OF GE-DOPED AgGaS2 CTYSTALS

• Main Authors: Chung, Wei-Jung, 鍾偉榮
• Other Authors: Peng-Heng Chang
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/40613645495256881849

碩士 === 國立交通大學 === 材料科學與工程研究所 === 84 === Ge doped AgGaS2 single crystals of diameters up to 10mm and length up to 68mm for applications in nonlinear optics and blue light emiting diodes have been successfully grown by vertical Bridgman method.Direct high temperature synthesisof element Ag, Ga,S with nonstoichoiemetry Ag0.99Ga1.001S2.001 is employed to prepare polycrystalline source materials for the subsequent single crystal grrowth.Growth quartz ampoules were coated with pyrolytic graphite buffer layersto prevent thermal expansion of the crystal during cooling from high temperature.The recommended growth conditions are:temperature gradient at the melt/solid:35 C/cm;pulling rate:30cm/day;cooling procedure:24 hr. to room temperature after growth.Precipitates,twins and microcracks are present in the as-grown crystals.Most of these defects can eliminated by the post annealing besides twins.As-grown AgGaS2 crystals were heat treated in a sealed quartz ampoulefor 12 to 14 days at 950C,using approximately 3wt% excess pure Ag.EPMA resultsindicate that the composition of crystals are uniform even more after annealing procedure,and the precipitates are Ga- rich as revealed by EPMA mapping.ICP results indicate that the concentration of Ge-doping increases at tail with the growth of crystal,and the partition coefficient is about 0.079.FTIR results indicate that IR transmittance can be enhanced by heat treated which removes the precipitats.PL results indicate that the emission energyfor the band-edge emission at room temperature is about 2.662eV.