Al_2O_3(0001)邻晶面上基底温度对PTCDI-C_5岛分布的影响（英文）

Effect of Al_2O_3(0001) Vicinal Surface Substrate Temperature on the Alignment of PTCDI-C_5 Islands

在α-Al_2O_3(0001)表面研究了N,N'-二戊基-3,4,9,10-苝二甲酰亚胺(PTCDI-C_5)薄膜形貌与基底温度之间的关系.在背景真空度低于6×10-7Pa的超高真空腔中,利用分子束外延方法在基底上生长标称厚度为0.6 nm的PTCDI-C_5薄膜,薄膜生长过程中的基底温度分别被控制在25℃、37℃和61℃.生长结束后,利用原子力显微镜(AFM)轻敲模式在大气环境下对薄膜形貌进行离线表征.AFM图像显示在Al_2O_3基底表面,PTCDI-C_5分子形成岛,而且PTCDI-C_5岛的排列与基底温度之间呈现一定关系.本文实验条件下,在25℃和37℃之间存在一个基底温度阈值.在薄膜生长过程中,当基底温度低于此温度阈值时,PTCDI-C_5岛在基底表面随机排列;相反,当基底温度高于此温度阈值时,PTCDI-C_5岛沿着Al_2O_3(0001)表面的台阶边缘分布.

The morphologies of N,N＇-dipenthyl-3 ,4,9,10-perylene tetracarboxylic diimide （PTCDI-C5） thin films on the α-Al2O3 （0001） substrate were investigated as a function of substrate temperature. The PTCDI-C5 thin films with a nominal thickness of 0. 6 nm were deposited on the substrate by molecular beam epitaxy in an ultrahigh vacuum chamber with a base pressure lower than 6 × 10^- 7 Pa. During dep-osition, the substrate temperature was controlled at 25 ℃ , 37 ℃, and 61 ℃ , respectively. The morphol-ogies of PTCDI-C5 thin films were characterized ex-situ by atomic force microscope （ AFM） in the tapping mode at room temperature. AFM images showed that the PTCDI-C5 molecules formed islands on A1203 substrate, and the arrangement of PTCDI-C5 islands showed dependence on the substrate temperature dur-ing deposition. Under our experimental conditions, a substrate temperature threshold between 25 ℃and 37 ℃ was observed. When the substrate temperature during deposition was lower than the temperature threshold, the PTCDI-C5 islands randomly distributed on the surface. On the contrary, when the substrate temperature during deposition was higher than the temperature threshold, the PTCDI-C5 islands aligned themselves along the step edges on the Al2O3 （0001） surface.