Anisotropic valence band dispersion of single crystal pentacene as measured by angle-resolved ultraviolet photoelectron spectroscopy
Anisotropic valence band dispersion of single crystal pentacene as measured by angle-resolved ultraviolet photoelectron spectroscopy
复制标题
DOI：
10.1557/jmr.2018.315
复制
发表时间：
2018-10-29
影响因子：
2.7
通讯作者：
Kera, Satoshi
中科院分区：
文献类型：
--
作者：
Nakayama, Yasuo;Hikasa, Masataka;Kera, Satoshi
单晶并五苯的电子结构对于阐明有机半导体材料中的载流子输运具有重要意义。最近在并五苯单晶样品上实现了价带弥散的实验观察，但由于过去的实验是在大气中形成表面氧化物的样品上进行的，所以它的本征性质仍然没有得到解决。本文采用X射线光电子能谱(XPS)和角度分辨紫外光电子能谱(ARUPS)对未经环境曝光的单晶并五苯样品进行了研究。XPS结果证实了样品中氧化物杂质丰度的降低。ARUPS测量清楚地分辨了单晶并五苯在表面布里渊区四个对称方向上的价带结构，表明分子间转移积分和价带最大处的空穴有效质量的各向异性至少是2.4倍。
Electronic structures of single crystal pentacene are of great interest for the elucidation of charge carrier transport in organic semiconductor materials. Experimental observation of valence band dispersion was recently achieved on single crystal samples of pentacene; however, its intrinsic properties are still unresolved because past experiments were performed on specimens with surface oxides formed by exposure to the ambient atmosphere. In this work, X-ray photoelectron spectroscopy (XPS) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) were conducted on single-crystal pentacene samples prepared without ambient exposure. The XPS results confirmed the reduction of the abundance of oxide impurities on the present samples. The ARUPS measurements clearly resolved the valence band structures of the single-crystal pentacene in four symmetry directions of the surface Brillouin zone, indicating anisotropy of at least a factor of 2.4 for the intermolecular transfer integral and hole effective mass at the valence band maximum.