CVD-ZnS异常大晶粒的再结晶机制

Recrystallization Mechanism of Abnormal Large Grains in CVD-ZnS

本文采用化学气相沉积法(CVD)制备出CVD-ZnS晶体,并通过一系列的测试和分析解释了CVD-ZnS异常大晶粒的再结晶机制。使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、电子衍射对石墨基板底部的CVD-ZnS异常大晶粒与正常区域晶粒的微观形貌进行观察,结果发现在靠近石墨基板底部与沉积方向相同的CVD-ZnS晶粒尺寸要比该方向上正常区域的晶粒大,异常大晶粒区的晶粒尺寸为50~100μm,晶界较宽,然而并没有表现出晶粒形态扩张伸长;其次在CVD-ZnS材料正常区域可以观测到明暗带,底部异常大晶粒区域则无此现象;另外在沉积温度为900~1000 K条件下,立方相是稳定的相,由于反应物浓度分布不均匀会导致堆垛层错、孪晶界和位错堆积组成的层位畸变发生。能谱(EDS)测试分析表明,在垂直于沉积方向上距离基板底部~9 mm的正常晶粒与距离石墨基板底部~0.3 mm的异常大晶粒相比,元素组成一致,在化学计量配比上S/Zn略大于1。X射线衍射(XRD)表征分析得出异常大晶粒再结晶过程中主要是以立方相形式存在,有少量六方相,并且确定异常大晶粒再结晶的优先取向是s(111)。

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 50~100μm,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).