Behavior of hot-electron at MIM tunnel junction/porous Si interface

当在Al/AlO_x/Ag结上施加不超过金属功函数的足够强的电压时，可以产生能量高于费米能级的所谓“热电子”。本研究旨在建立Al/AlO_x/Ag隧道结的制备方法，并通过测量其I-V曲线，获得有关隧道结与多孔硅衬底界面处热电子行为的基本知识。此外，银电极表面上的化学物种的变化，在偏置电压施加在整个结的红外反射吸收光谱进行了研究。所得结果总结如下。(1)A在制备Al/AlO_x/Ag隧道结的过程中，最重要的是确定Al薄膜电极的氧化条件。铝电极在280℃氧气氛中氧化2小时或在450℃空气中氧化几分钟是获得结的合适条件。（2）在441. 6 nmHe-Cd激光（80 mW）辐照下，多孔硅衬底上形成的结的隧道电流显著增加，而玻璃衬底上形成的结的隧道电流在相同的辐照条件下没有变化。本研究中使用的多孔硅的带隙约为1.6 eV，因此在多孔硅处产生的光电压可能会通过改变Al电极和多孔硅衬底之间的电荷分布来影响结的隧穿性质。（3）当向Al电极施加偏压（+）时，促进了在结上形成的2甲基-1，4萘醌薄膜的分解。

When a sufficiently strong voltage but not beyond the metal work function is applied across an Al/AlO_x/Ag junction, the so-called "hot-electron" whose energy is higher than the Fermi level can be generated. In this study, we aimed to establish the method of fabrication of Al/AlO_x/Ag junctions and to obtain basic knowledge concerning the behavior of hot electrons at the interface between the tunnel junction and the porous-Si substrate through measurements of the I-V curve. Further, the change in chemical species on Ag electrode surface during a bias voltage was applied across the junction was investigated with IR reflection absorption spectroscopy. The results obtained are summarized as follows.(1)A matter of the utmost importance in preparation of the Al/AlO_x/Ag tunnel junction is to establish the oxidation conditions of Al thin film electrode. The oxidation of the Al electrode at 280℃, 2 hours in oxygen (1 atm) atmosphere, or at 450℃, several minutes in air was suitable to obtain the junction.(2)Under irradiation of 441.6nm He-Cd laser (80mW), a remarkable increase in the tunnel current was observed for the junction formed on porous-Si substrate, whereas the junction formed on glass substrate showed no change in the tunnel current even though the same irradiation conditions were employed. The band-gap of the porous-Si used in the present study was about 1.6 eV and hence the photo-voltage generated at the porous-Is might influence the tunneling properties of the junction through the change in charge distribution between the Al electrode and the porous-Si substrate.(3)The decomposition of a 2Methyl-1, 4Naphtoquinone thin film formed on the junction was promoted when applying the bias voltage (+) to the Al electrode.