质子交换LiTaO3光波导特性及晶格常数变化

采用气相质子交换方法,在Z－切LiTaO3晶体表面制备平面光滑波导层。样品制备采用245℃苯甲酸气体,在LiTaO3晶体在－C和＋C表面交换8－20小时。质子交换层在LiTaO3表面形成,并用棱镜耦合测量波导样品。然后在HF：HNO3酸中用化学方法腐蚀波导层,并用电子显微镜观测光波导层与补底界面的形貌。用X射线衍射法,测量LiTaO3质子交换光波层的晶格常数变化。用双晶X射线测量质子交换（PE）和退火质子交换（APE）波导层晶格常数的变化。样品的X射线衍射曲线表明,PE和APE波导晶格常数的变化不同。实验中,还测量了有无极畴反转LiTaO3晶格常数的改变。     

Nickel-disilicide-assisted excimer laser crystallization of amorphous silicon

Polycrystalline silicon (poly-Si) thin film has been prepared by means of nickel-disilicide (NiSi多晶硅 受激准分子激光器结晶 结晶化 界面晶粒生长polycrystalline silicon, excimer laser crystallization,Ni-disilicide, Ni-metal-induced lateral crystallization, two-interface grain growthProject supported by the National High Technology Development Program of China (Grant No 2002AA303250) and by the National Natural Science Foundation of China (Grant No 60576056).9/7/2005 12:00:00 AM3/6/2006 12:00:00 AMPolycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon （a-Si） coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy （SEM）, another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization （Ni-MILC） model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.