通过近边X射线吸收精细结构光谱（NEXAFS）研究吸附在Si(001)-(2×1)表面的C60分子未占据分子轨道中的热效应。

Thermal effect in unoccupied molecular orbitals of C60 molecules adsorbed on a Si(001)-(2 x 1) surface studied by NEXAFS.

作者信息

Kondo D, Sakamoto K, Takeda H, Matsui F, Ohta T, Amemiya K, Uchida W, Kasuya A

机构信息

Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan.

出版信息

J Synchrotron Radiat. 2001 Mar 1;8(Pt 2):505-7. doi: 10.1107/s0909049500019695.

DOI:10.1107/s0909049500019695

PMID:11512831

Abstract

We report here the temperature-dependent unoccupied molecular orbitals (MO's) of C60 molecules adsorbed on a Si(001)-(2 x 1) surface measured using near edge x-ray absorption fine structure (NEXAFS). At 300 K, the NEXAFS spectrum reveals that the interaction between a 1.0 monolayer (ML) C60 film and a Si(001) surface is mainly the van der Waals force. After annealing the samples at 500 K, we observe an increment in the full-width at half-maximum of unoccupied MO's, which indicates the change of the interaction. Moreover, the lowest unoccupied molecular orbital (LUMO) shifts to the higher photon energy side and the intensity of the LUMO+1 relative to that of the LUMO+3 decreases in the NEXAFS spectrum. These results suggest that the strong interaction induced at 500 K has a covalent character, to which the LUMO+1 contributes.

摘要

我们在此报告使用近边X射线吸收精细结构（NEXAFS）测量的吸附在Si(001)-(2×1)表面的C60分子的温度依赖型未占据分子轨道（MO）。在300K时，NEXAFS光谱显示1.0单层（ML）C60薄膜与Si(001)表面之间的相互作用主要是范德华力。在500K对样品进行退火后，我们观察到未占据MO的半高宽增加，这表明相互作用发生了变化。此外，在NEXAFS光谱中，最低未占据分子轨道（LUMO）向更高光子能量侧移动，并且LUMO+1相对于LUMO+3的强度降低。这些结果表明，在500K时诱导的强相互作用具有共价性质，LUMO+1对此有贡献。