Recrystallization Mechanism of Abnormal Large Grains in CVD-ZnS
Yang Hai Guo Li Liu Xiaohua Tian Zhirui Li Dongxu Jiang Lipeng
GRINM Guojing Advanced Material Co.,Ltd.,General Research Institute for Nonferrous Metals
Abstract：
CVD-ZnS crystals were prepared by chemical vapor deposition(CVD)and the recrystallization mechanism of abnormal large grains in CVD-ZnS was explained by a series of tests and analyses. The microscopic morphology of CVD-ZnS abnormally large particles at the bottom of graphite substrates and grains in normal areas were observed by scanning electron microscope(SEM),transmission electron microscope(TEM)and electron diffraction. The results showed that the grains size of abnormal large CVD-ZnS in the same direction as the deposition near the bottom of graphite substrate was larger than that of normal area,the grains size in the abnormal large grains area was 50～100 ?m,and the grain boundary was wide,but it did not show the elongation of grain morphology expansion. Secondly,the bright and dark zone could be observed in the normal area of CVD-ZnS material,but there was no such phenomenon in the abnormal large grain area at the bottom. Besides,under the condition that the sedimentary temperature was 900～1000 K,the cubic phase was a stable phase,and the unevenness of the concentration distribution of the reactants would lead to the dislocation of the stacking layer,the formation of the layer distortion of the twin boundary and dislocation accumulation. Energy dispersive spectrometer(EDS)test showed that the normal grains with a distance of ～9 mm from the bottom of the substrate perpendicular to the deposition direction were compared with the abnormal large grains with a distance of ～0.3 mm from the bottom of the graphite substrate,and elemental composition was the same. However,S/Zn was slightly larger than 1 in stoichiometric ratio. X-ray diffraction(XRD)characterization analysis concluded that the abnormal large grains recrystallization process was mainly in the form of cubic phase,there were a small number of hexagonal phase,and the priority orientation of abnormal large grains recrystallization was s(111).
Keyword：
chemical vapor deposition(CVD)-ZnS;microstructure;abnormal large grain;recrystallization mechanism;
Fig.2 Sample cross section cut parallel to and perpendicular to the deposited direction of CVD-ZnS
(a)Parallel to the deposited direction of CVD-ZnS;(b)Per-pendicular to deposited direction,A/B samples taken fromFig.1,top A/B sample distance from substrate surface 25～29mm,middle A/B sample distance from substrate surface 12～16 mm,bottom A/B sample distance from substrate surface 1～5 mm
Fig.3 SEM images of S direction normal area,S direction transition area and S direction abnormal large grains area-SEM images and EDS analysis of P direction normal area and P direction abnormal large grains area
(a)S direction normal area(distance from substrate surface 9～30mm);(b)S direction transition area(distance from substrate sur-face 8.5～9.0 mm);(c)S direction abnormal large grains area(dis-tancefromsubstratesurface 0～0.2mm);(d)P direction normal ar-ea(distance from substrate surface～9 mm);(e)P direction abnor-mallargegrainsarea(distancefrom substratesurface～0.3mm)
Fig.4 TEM images and electron diffraction diagram of grains of normal area and abnormal large grains inside the bottom area
(a)TEM images in grains of normal area;(b)Electron diffraction diagrams in normal areas;(c)TEM image of abnormal large grainsinside the bottom area;(d,e)Electron diffraction diagram of abnormal large grains area at bottom
