Study on Nanofabrication and One-Dimensional Quantum Effects

本项目旨在建立纳米加工技术的基础，研究纳米结构中的介观效应及其外场控制，这对未来的量子器件具有重要意义。结果总结如下：1)证明了离子束辅助刻蚀可以有效地刻蚀SiO_2和Si_3N_4，刻蚀速率比物理溅射刻蚀快100倍以上。使用低能量聚焦离子束也证明了砷化镓中工艺诱导损伤的减少。这些结果对于使用聚焦离子束的无掩膜蚀刻或沉积是重要的。2)我们首先观察到介观结构中电子波的干扰导致的砷化镓的普遍电导波动。此外，我们还发现了磁电阻的非局域性和不对称性。这是通过我们已经建立的纳米加工技术实现的。3)我们首先在GaAs/GaAlAs异质结构亚微米环器件中观察到明显的Aharanov-Bohm效应。这表明通过外部场控制干扰效应的可能性，这对器件应用很重要。4)在GaAs/GaAlAs异质结构量子线中观察到不同的弹道输运效应。首先，我们证明了由于电子在弹道区域内直接移动，在电流路径的弯曲处或连接处会出现较大的负电阻。5)在窄GaAs/GaAlAs线中观察到一维量子尺寸效应。

The present project is to establish the basis of nanofabrication technology and to investigate mesoscopic effects and their control by external fields in nanostructures, which are important for future quantum devices. The results are summarized as follows.1) It was demonstrated that SiO_2 and Si_3N_4 are effectively patterned by ion beam assisted etching with high etching rate, more than 100 times faster than the physi-cal sputter etching. Reduction of process induced damage in GaAs was also demonstrated by using low energy focused ion beams. These results are important for maskless etching or deposition using focused ion beams.2) We, first, observed universal conductance fluctuations in GaAs which comes from interference of electron waves in mesoscopic structures. In addition, we also found nonlocality and asymmetry of magnetoresistance. This was realized by using nanofabrication technology which we have established.3) We, first, observed a clear Aharanov-Bohm effect in GaAs/GaAlAs heterostructure submicron ring devices. This indicates the possibility of controlling the inter-ference effects by an external fields, which is important for device applications.4) We observed various ballistic transport effects in GaAs/GaAlAs heterostructure quantum wires. We, first, demonstrated that a large negative resistance appears at bents or interconnects of current path becouse electrans travel straightforward in ballistic region.5) We observed one dimensional quantum size effect in narrow GaAs/GaAlAs wires.