Measurements of electronic properties of interfaces with functional nanostructures by bias-voltage non-contact atomic force microscopy/spectroscopy

本研究的目的是利用偏压非接触原子力显微镜/光谱学在原子尺度上分析光电功能纳米结构及其与基底的电子和结合状态。结果表明，当我们将两块凝聚态物质相互靠近，改变它们之间的偏置电压时，我们可以通过静电势能的变化对两个表面的电子态进行能量调谐，从而产生共振态，即共价键。此外，同时测量它们之间的相互作用力和电流，意味着有可能评估隧道势垒的坍塌和分析电子传导与力的关系。因此，我们提出了尖端制备技术，以提高电流和力的检测灵敏度。我们清洗了AFM悬臂上的Si尖端，并在其上沉积Ge，或者用尖端触摸加热的Ge或Si衬底，并加热和/或施加偏置电压：这导致尖端上纳米柱的生长。用扫描电镜（SEM）、扫描电镜（SAM）和透射电镜（TEM）对其进行评价。此外，我们还制作了石英力传感器，并在电化学蚀刻的Pt- it线上制备了Pt纳米柱。我们在原子尺度上观察了沉积在Si(111)-7x7上的4,4”-二氨基-对terphenyl (DAT) π共轭分子，并用XPS分析了它们的电子结合态。DAT在线性分子的两端有两个氨基，具有在Si衬底上形成长度可控的π共轭分子的潜力，通过与DAT交替沉积1,4-双（4-甲酰基苯乙烯）苯等进行气相聚合。我们观察到DAT优先吸附在7x7重构的有缺陷的半细胞上，并获得了一个氨基与Si底物结合而另一个氨基在DAT末端游离的证据。此外，我们得出结论，与Si结合的氨基对底物表现出电传导。

The aim of this study is to analyze opto-electronic functional nanostructures on atomic scale, and their electronic and binding states to substrates using bias-voltage non-contact atomic force microscopy/spectroscopy. The results showed that, when we brought two pieces of condensed matter close to each other, and changed bias voltage across them, we can energetically tune the electronic states at the two surfaces through the change in electrostatic potential energy, resulting in resonating states, i.e. covalent bond. In addition, simultaneous measurements of interaction force with current between them implied that the possibility of evaluating collapse of tunneling barrier and analyzing the correlation between electronic conduction and force. Thus, we promoted the tip preparation techniques to improve the detection sensitivity of current and force. We cleaned Si tips on AFM cantilevers, and deposited Ge on them or touch heated Ge or Si substrates with the tip, and heated and/or applied bias voltage: this leads to growth of a nanopillar on the tip. We evaluated them with SEM, SAM and TEM. Moreover, we fabricated quartz force sensors and prepared Pt nanopillars on electrochemically etched Pt-It wire for the sensors. We observed π-conjugated molecules of 4,4"-diamino-p-terphenyl (DAT) deposited on Si(111)-7x7 on atomic scale and analyzed their electronic binding states by XPS. DAT has two amino groups at both ends of the linear molecule with potential to form π-conjugated molecules with a controlled length standing on Si substrates, which are vapor polymerized by depositing, e.g., 1,4-bis (4-formylstyryl) benzene alternatively with DAT. We observed that DAT was adsorbed preferentially on faulted half cells of the 7x7 reconstruction, and obtained evidence that one amino group is bound with Si substrate and the other is free at the end of DAT. Moreover, we concluded that the amino group binding with Si exhibited electric conduction to the substrate.