Ge/Au,Ge/Ag双层膜和Ge-Au,Ge-Ag合金膜中非晶Ge的晶化

本文对Ge/An,Ge/Ag,双层膜和Ge-An,Ge-Ag合金膜的退火过程进行了透射电子显微镜观测,对Ge/多晶Au(或Ag)还进行了加热过程的原位观测。观测表明,多晶Au和单晶Au膜的存在使非晶Ge的晶化温度T_c的下降显著不同,可由晶界三叉点等处为非晶Ge的有利形核位置来解释,双层膜的缩聚区中由于局域优先晶化的影响,不仅T_c(=100℃)比非缩聚区中(T_c=150℃)低,而且形成直径为1—2μm的Ge大晶粒,而Ge/多晶Ag和Ge/单晶Ag膜的T_c均约为280℃,合金膜中金属含量较低时(C_Au<17at％,C_Ag<18at％),T_c高于相应的Ge/多晶Au(Ag)膜;金属含量较高时,T_c低于Ge/多晶Au(Ag)膜。这说明过饱和金属原子的存在使得非晶Ge的晶化势垒大大降低。关键词：

CRYSTALLIZATION OF AMORPHOUS Ge IN Ge/Au, Ge/Ag BILAYER FILMS AND Ge-Au, Ge-Ag ALLOY FILMS

In this article, as-evaporated and annealed samples of Ge/Au, Ge/Ag bilayer films and Ge-Au, Ge-Ag alloy films were investigated by TEM. In situ observations of Ge/ polyerystalline Au (p-Au) and Ge/p-Ag films during heating were also made by TEM. It is found that crystallization temperature T_c of amorphous Ge (a-Ge) in a-Ge/p-Au is much lower than T_c of a-Ge/monocrystalline Au (m-Au). It is shown that the boundary triple points and other interface defects of p-Au films are the favourable nucleating positions for a-Ge crystallization in bilayer films. T_c of a-Ge in the condensation regions of Ge/p-Au films (≈100℃) is lower than T_c (≈150℃) in the noncondensa-tion regions. There are some large Ge grains in the condensation regions because of the effect of favourable crystallization in local regions. T_c of a-Ge in a-Ge/p-Ag and a-Ge/ m-Ag films is about 280℃. T_c of alloy films is higher than that of correlative bilayer films when metallic content in alloy film is low (C_Au < 17at%, C_Ag< 18at%). T_c of alloy films is lower than that of bilayer films when metallic content is relatively high. It is because of smpersaturation metallic atoms which reduce the crystallization potential barrier of a-Ge significantly.