Observation of single aromatic molecule by scanning tunneling microscope.

利用光调制和偏压调制扫描隧道显微镜（STM）研究了吸附在Si（100）2x1表面上的芳香族分子。本研究的目的是揭示分子结构和电子性质对STM分子成像的影响。通过比较光调制和偏压调制的STM图像，可以将光激发载流子的贡献与表面光伏分开。利用扫描隧道显微镜（STM）测量了酞菁锌（ZnPc）和晕苯分子吸附在Si（100）2* 上的光电流图像。结果表明，光调制和偏压调制的STM图像具有很好的成像效果。1的表面已经获得了扫描隧道显微镜。分子的光电流图像主要是通过局域态密度（LDOS）效应对表面光电压进行补偿的结果。ZnPc分子总是观察到明亮的图像，表明在偏置电压下的大LDOS。另一方面，晕苯分子的图像在它们的对比度上显示出广泛的变化。这种差异归因于最高占据和最低未占据分子轨道之间的带隙能的差异。结果表明，光调制STM对吸附在半导体表面上的芳香分子的结构和电子性质是敏感的。

We have performed the photo-modulated and bias modulated scanning tunneling microscopy (STM) study on aromatic molecules adsorbed on Si (100) 2x1 surfaces. The purpose of this research project is to reveal the effect of the investigation of the effect of molecular structure and electronic property on molecular imaging by STM.Comparision between photo- and bias-modulated STM images enable to separate the contribution of photoexcited carrier from surface pbotovoltage.Photocurrent images of zinc-phthalocyanine (ZnPc) and coronene molecules adsorbed on Si (100) 2*1 surfaces have been obtained by scanning tunneling microscopy. The photocurrent images of molecules are mainly the result of cotribution of surface photovoltage through the local density of state (LDOS) effect. The ZnPc molecules are always observed as bright images indicating large LDOS at the bias voltage. On the other hand, the images of coronene molecules show wide variety in their contrast. This difference is attributed to the difference of gap energy between highest occupied and lowest unoccupied molecular orbitals. The results demonstrate that photo-modulated STM is sensitve to the structrue and electronic property of aromatic molecules adsorbed on semiconductor surfaces.