Study of Ultra-Thin-Film/Ultra-Fine-Structure Devices

用金属有机化学气相沉积法在东京工业大学成功地制备了氧化物超导体YBaCuO超薄膜，其温度低至5 0 0ﾟC。从3.6 nm(3个晶胞厚度)的薄膜中观察到超导电性的开始。从4.8 nm厚的样品观察到了30K的零电阻率，从10 nm厚的MgO衬底上观察到了80K的零电阻率。这些结果表明，我们已经沉积了最高质量的薄膜。我们还发现，在用原子层层法生长YBaCuO超薄膜的过程中，促进了化学物种的迁移。原子力显微镜观察到YBaCuO薄膜表面非常光滑，表面粗糙度在10微米范围内小于1个晶胞厚度。从微桥结构中获得了高达10^7Acm^-2的临界电流密度。用350keV电子…辐照YBaCuO薄膜，在剑桥大学制备了约瑟夫森结更多的光束。利用二氯硅烷和氢基原子层外延技术制备了硅超薄膜，并首次采用有机硅和氢自由基原子层外延技术制备了Ge超薄膜。东京工业大学提出了用于硅量子线器件的沟槽-氧化物金属氧化物-半导体结构。利用超级计算机模拟了沟槽MOS结构对电子的限制。从低温下的电容-电压特性可以观察到量子效应。采用电子束光刻和电子回旋共振反应离子刻蚀方法制作了沟槽MOS实际器件。利用东京工业大学的数字化学气相沉积方法，在0.5K下观察到了一种由量子效应引起的硅量子点结构。研究发现，氢自由基在纳米硅的形核和晶体生长过程中起着非常重要的作用。结果表明，氢自由基也有助于选择性地刻蚀纳米晶硅周围的非晶硅，以制备有效的势垒层。东京工业大学和剑桥大学对非晶硅和多晶硅的薄膜晶体管进行了研究。讨论了降解机理、超大规模集成技术和神经网络技术的应用。较少

Ultrathin films of oxide superconductors YBaCuO have been prepared successfully at a temperature of as low as 500^ﾟC by metalorganic chemical vapor deposition method at Tokyo Institute of Technology. Superconductivity onset was observed from a film of as thin as 3.6nm(3 unit-cell-thickness). Zero-resistivity at 30K was observed from 4.8nm-thick sample and 80K was observed from 10nm-thick YBaCuO on MgO substrate. These results suggest that we have deposited the highest quality films. We have also revealed that migration of chemical species were enhanced during the crystal growth of ultrathin films of YBaCuO by atomic layer-by-layer method. Very smooth surface of YBaCuO films with roughness of less than one unit-cell-thickness along 10 mum range was observed by atomic force microscopy. A critical current density of as high as 10^7Acm^<-2> was obtained from a microbridge structure. Josephson junctions were fabricated at Cambridge University by irradiating YBaCuO films with 350KeV electron … More beam. Magnetic field dependence of the critical current revealed that very uniform junction was obtained.Ultra-thin films of silicon were prepared by atomic layer epitaxy by using dichlorosilane and hydrogen radicals at Tokyo Institute of Ultra-thin films of Ge were also prepared by atomic layer epitaxy for the first time by using organicgerman and hydrogen radicals.Trench-oxide metal-oxide-semiconductor structure was proposed for silicon quantum wire devices from Tokyo Institute of Technology. Electron confinement by the trench MOS structure was simulated by using a supercomputer. It was then evaluated that quantum effects would be observable from the capacitance-voltage characteristics at low temperatures. Actual device of trench-MOS was fabricated by using electron beam lithography and electron cyclotron resonance reactive ion etching method. A structure due to quantum effects was observed from a sample with 28nm-wide trench at 0.5K.Digital chemical vapor deposition method was proposed for the fabrication of Si quantum dot structure from Tokyo Institute of Technology. It was found that hydrogen radicals played very important role both in the nucleation and crystal growth of nanocrystalline silicon. It turned out that hydrogen radicals were also useful for theselective etching of amorphous silicon surrounding nanocrystalline silicon for the fabrication of effective potential barrier layer.Thin film transistors of amorphous and polycrystalline silicon were investigated both at Tokyo Institute of Technology and Cambridge University. The mechanism of degradation, application of ultra-large scale integration and neural network were discussed. Less