Chen Liwei, Ludeke R, Cui Xiaodong, Schrott Alejandro G, Kagan Cherie R, Brus Louis E
Department of Chemistry, Columbia University, New York, New York 10027, USA.
J Phys Chem B. 2005 Feb 10;109(5):1834-8. doi: 10.1021/jp046371+.
Monolayer islands of pentacene deposited on silicon substrates with thermally grown oxides were studied by electric force microscopy (EFM) and scanning Kelvin probe microscopy (SKPM) in ultrahigh vacuum (UHV) after prior 10 min exposure to atmospheric ambient. On 25-nm-thick oxides, the pentacene islands are 0.5 V higher in electrostatic potential than the silicon dioxide background because of intrinsic contact potential differences. On 2-nm-thin oxides, tunneling across the oxides allows Fermi level equilibration with pentacene associated states. The surface potential difference depends on the doping of the underlying Si substrates. The Fermi level movement at the pentacene SiO(2) interface was restricted and estimated to lie between 0.3 and 0.6 eV above the pentacene valence band maximum. It is proposed that hole traps in the pentacene or at the pentacene-oxide interface are responsible for the observations.
在超高真空（UHV）环境中，将并五苯单层岛沉积在具有热生长氧化物的硅衬底上，并在预先暴露于大气环境10分钟后，通过电场显微镜（EFM）和扫描开尔文探针显微镜（SKPM）对其进行了研究。在25纳米厚的氧化物上，由于固有接触电势差，并五苯岛的静电势比二氧化硅背景高0.5伏。在2纳米厚的氧化物上，通过氧化物的隧穿使得费米能级与并五苯相关态达到平衡。表面电势差取决于底层硅衬底的掺杂情况。并五苯与二氧化硅界面处的费米能级移动受到限制，估计位于并五苯价带最大值上方0.3至0.6电子伏特之间。研究表明，并五苯中或并五苯与氧化物界面处的空穴陷阱是造成这些观测结果的原因。
