Investigation of Gate-controled Electron-Emittor

当MOS和MIM结构电容器的栅电极被正电压偏置时，在栅电极边缘出现电子发射现象。通过观察在靠近样品电容器的阳极上形成的荧光屏的光点来收集发射的电子，证实了电子发射的证据。MOS类型的实验装置建立在p-Si衬底上，在其上形成了SiO_2层和金属电极。大多数MIM型实验装置是由一层薄薄的CeO2薄膜作为绝缘层，中间夹着一个下电极和一个上栅电极组成的。这些金属电极的材料是从铝、金、铬和钛中选择的几种组合。电子从栅电极边缘的几个非常小的点发射。特别是当栅极蒸发时，在栅电极上产生的小孔可以有效地获得发射电流，发射电流通常伴随着很大的波动和不稳定，但在某些情况下，尽管电子是从10微米量级的很小的光斑发射的，但发射电流却是很大的镜安量级的电流。只有当以下三个过程都运行良好时，才被认为是电子发射。(1)从硅衬底或下电极到氧化物或绝缘层的电子注入。(2)氧化物或绝缘层中的电子输运。(3)氧化物或绝缘层表面的电子发射。总之，在很高的电场强度下，超热电子的注入是最重要的过程，它被认为是服从FowlarNordheim隧道效应的。电子注入来源于氧化物与半导体或绝缘体与金属电极界面的晶格缺陷或杂质原子的某些位置，势垒变薄和降低。

An electron-emission phenomenons from edges of gate-electrodes of MOS or MIM structure capacitors is found when the gate-electrodes are biased by positive voltages.The evidence of the-electron-emission is confirmed by observing light spots of a fluorescent screen formed on an anode which is placed adjacent to the sample capacitor to collect the emitted electron.The MOS-type experimental device is constructed on a p-Si substrate upon which a SiO2 layer and a metal electrode are formed. Most of MIM-type experimental devices are made up of a thin CeO2 film as an insulator layer sandwiched by a lower-electrode and an upper gate-electrode. Materials of these metal electrodes are chosen in several combinations from Al, Au, Cr and Ti.The electrons are emitted from a few very small spots along the edges of the gate-electrode. Especially, the emission current can be obtained efficiently from small holes which happen to generate on the gate-electrode when the gateelectrode is evaporated.The emitted current-is generally accompanied with large fluctuation and instability but in some cases shows very large current of the order of mirriampere in spite of the electrons are emitted from a very small spot of the order of 10 micrometers.The electron-emission is considered to occur only when following 3 processes are all well-operated. (1) Electron injection from the Si-substrate or the lower-electrode to the oxide or insulator layer. (2) Electron transportation in the oxide or insulator layer. (3) Electron emission from the surface of the oxide or insulator layer.Above all, the injection of hot electrons which is considered to obey FowlarNordheim tunneling effect is most important process under the very high electric field strength. The electron injection originates from some sites of lattice imperfections or impurity atoms at the interface between the oxide and the semiconductor or the insulator and the metal electrode where the potential barriers are thinned and lowered.