高剂量离子注入直接形成Ge纳米晶的物理机理

Physical Mechanism of Ge Nanocrystals Formed by High-Dose-Ion-Implantation

研究了单束双能高剂量Ge离子注入、不经过退火在非晶态SiO2薄膜中直接形成镶嵌结构Ge纳米晶的物理机制．实验中利用不加磁分析器的离子注入机，采用Ge弧光放电离化自动形成的Ge^＋和Ge^2＋双电荷离子并存的单束双能离子注入方法，制备了10^16～10^18cm^-2多种剂量Ge离子注入的Si基SiO2薄膜样品．用GIXRD表征了Ge纳米晶的存在，并仔细分析得到了纳米晶形成的阈值剂量．通过TEM分析了Ge纳米晶的深度分布和晶粒尺寸．用SRIM程序分别计算了双能离子在SiO2非晶层的射程和深度分布，与实验结合，得到纳米晶形成的物理机制，即纳米晶的形成与单束双能离子注入时Ge^＋和Ge^2＋相互碰撞产生的能量沉积在SiO2中形成的局域高温有关．

The formation mechanism of Ge nanocrystals （nc-Ge） embedded in a SiO2 amorphous film is studied. The samples are prepared by Ge ion implantation of mono-beam with two kinds of energy （or charge）,different doses from 1 × 10^16 to 1 × 10^18 cm^-2 and without subsequent annealing. The solid Ge is ionized to Ge^＋ and Ge^2＋ ions under arc discharge. Both Ge^＋ and Ge^2＋ ions are accelerated at the voltage of 40kV, without any magnetism analyzer, and implanted into an amorphous SiO2 film at the same time. The nc-Ge existence is characterized and the threshold dose of the nc-Ge formation is studied by GIXRD. The size and distribution of the nc Ge are observed by TEM. The Ge ion range and depth distribution in the amorphous SiO2 film are calculated by an SRIM program. Combining experiment results with theoretical calculation,the physical mechanism of a nc-Ge formation is also obtained,i, e. ,it is related to the local high temperature induced by the energy deposition resulting from the collision of Ge^＋ and Ge^2＋ during ion implantation.