Study on Nanofabrication and One-Dimensional Quantum Effects

本项目的目的是建立纳米制造技术的基础，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的意义。结果表明，离子束辅助刻蚀可以有效地刻画SiO_2和Si_3N_4，刻蚀速度比物理溅射刻蚀快100倍以上。用低能聚焦离子束也证明了降低了工艺引起的损伤。这些结果对于利用聚焦离子束进行无掩膜刻蚀或沉积具有重要意义。2)首先，我们观察到了由于介观结构中电子波的干涉而引起的普遍的电导波动。此外，我们还发现了磁阻的非定域性和不对称性。这是通过我们建立的纳米加工技术实现的。3)首先，我们在GaAs/GaAlAs异质结亚微米环器件中观察到了明显的Aharanov-Bohm效应。这表明可以通过外场来控制干涉效应，这对于器件的应用是很重要的。4)我们观察到了各种不同的GaAlAs异质结量子线的弹道输运效应。首先，我们证明了由于电子在弹道区域的直线传播，在电流路径的弯曲处或互连处出现了大的负阻。5)我们在窄线的GaAlAs/GaAlAs中观察到了一维量子尺寸效应。

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.