Research of Monolayer/Metal Interface by Inelastic Electron Tunneling Spectroscopy (IETS)

本研究的目的是研究金属/LB单层界面，即了解LB单层如何吸附在金属（氧化物）上。我们的研究结果如下：1。我们构建了非弹性电子隧道光谱（IETS）测量系统，通过该系统我们可以观察到金属-绝缘体-金属隧道结中的金属（氧化物）声子和分子振动峰。我们制备了Sn， Pb薄膜，并将其作为LB单层转移的衬底，通过两种氧化方法（如不同湿度条件）制备了Sn/SnO_2/Pb， Pb/PbO /Pb。并观察了锡、铅氧化物声子谱。我们做这个实验的原因是为了掌握LB单层转移所需金属的表面状况。从这些测量中，我们得到了以下结果。(1) PbO声子廓线不随湿度变化而变化。即使有机分子掺杂到金属/金属氧化物界面中，也没有观察到分子振动峰。(2)湿度对SnO_2声子的影响较大。在高偏置区观察到分子振动峰。因此，我们使用锡作为隧道结的基底电极来观察LB单层的分子振动峰。根据上述实验结果，我们制备了Sn/SnO_2/Ar_2Co/Pb隧道结，并观察了隧道光谱。通过对超导Pb能隙的测量，我们认识到隧穿是隧道结中主要的电子转移方式。我们进一步测量了高偏置区域的隧道光谱。结果，在相同的隧道结中观察到“运行依赖”的隧道光谱。这可能是由于LB单分子层中各组分的排列使其永久偶极子电荷增强所致。

The aim of this research is to study a metal/LB monolayer interface, that is, to know how a LB monolayer would be adsorbed on a metal (oxide).The results we researched are as follows ;1. We constructed Inelastic Electron Tunneling Spectroscopy (IETS) measuring system, by which we can observe metal (oxide) phonon and molecular vibration peaks in a metal-insulator- metal tunnel jonction.2. We prepared Sn, Pb thin films, that would be used as substrates on which a LB monolayer could be transfered, Sn/SnO_2/Pb, Pb/PbO /Pb produced by two kinds of oxidation procedures (e. g. by varying humidity condition). And we observed Sn, Pb oxide phonon spectra. The reason why we did this experiments is to grasp the surface condition of the metals for a LB monolayer to be transfered. From these measurements, we obtained results below.(1) The contours of PbO phonons do not change with humidity condition. The molecular vibration peaks are not observed, even if organic molecules are doped into the metal/metal oxide interface.(2) SnO_2 phonons are strongly affected by humidity condition. And in the higher bias region the molecular vibration peaks are observed.Therefore we used Sn as the base electrode of a tunnel junction to observe molecular vibration peaks of LB monolayer. From the experimental results above mentioned, we prepared Sn/SnO_2/Ar_2Co/Pb tunnel junctions, and observed the tunnel spectra. We recognized that tunneling is the dominant electron transfer in this tunnel junction from the measurement of supercnducting Pb energy gap. Further we measured the tunnel spectra in the higher bias region. As the result, 'run-dependent' tunnel spectra were observed in the same tunnel junction. This would probably be attributed to the charging with enhancement of permanent dipole of a LB monolayer by alignment of the constituents.