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

本研究的目的是研究金属/单分子膜界面，即了解单分子膜在金属(氧化物)上的吸附情况。研究结果如下：1.构建了非弹性电子隧道谱(IETS)测量系统，可以观测到金属-绝缘体-金属隧道连接中的金属(氧化物)声子和分子振动峰。我们制备了锡、铅薄膜作为衬底，通过两种氧化工艺(如变湿条件)制备了锡/SnO_2/铅、铅/铅/铅单分子膜。并观察到了锡、铅氧化物的声子谱。我们做这个实验的原因是为了掌握要转移的LB单分子膜的金属的表面状况。通过这些测量，我们得到了以下结果：(1)PbO声子的轮廓不随湿度变化。即使有机分子掺杂到金属/金属氧化物界面，也没有观察到分子振动峰。(2)SnO_2声子受湿度的影响很大。并在较高偏压区域观察到分子振动峰。因此，我们使用锡作为隧道结的基极，观察到了LB单分子膜的分子振动峰。根据上述实验结果，我们制备了Sn/SnO_2/Ar_2Co/Pb隧道结，并观察了隧道谱。通过对超导能隙的测量，我们认识到隧道结中的电子转移是以隧道效应为主。此外，我们还测量了高偏压区的隧道光谱。结果，在同一隧道结中观察到了“运行依赖”的隧道光谱。这可能归因于通过成分的排列增强了LB单分子膜的永久偶极的荷电。

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.