Study on epitaxial metal/insulator multilayr structure formation

离子团束（ICB）法是一种用于制备金属、绝缘体等薄膜的方法，与其他方法相比，具有独特的性能。Al/Al_2O_3多层结构由于其界面处的能带偏移大、金属的载流子密度高和绝缘层中的击穿场强高，是制备高速量子效应器件的理想材料。我们用ICB法在Si（111）衬底上外延生长了Al/Al_2O_3多层结构。用STM、TEM和RHEED研究了样品的表面状态和结晶度，发现Al在Al_2O_3上和Al_2O_3在Al上都实现了外延生长，Al和Al_2O_3层之间的界面平整。此外，我们还成功地在Si（111）衬底上用外延Al/Al_2O_3多层结构制作了三势垒共振隧穿二极管，并观察到了负微分电阻。谐振电压为1.22 V，峰谷比为1.003。谐振电压的计算值与传递矩阵法的计算值基本一致。外延Al/Al_2O_3多层结构有望应用于量子效应器件。

Ionized cluster beam (ICB) method has been used to form thin films of metals, insulators and so on which have unique characteritics when compared to films formed using other techniques. The ICB method has also been applied to low temperature growth of epitaxial films on substrates having a large lattice mismatch.Al/Al_2O_3 multilayr structures are suitable candidates for high speed quantum effect devices, because of the large band offset at the interface, high carrier density of the metal and high breakdown field in the insulator. We have grown epitaxial Al/Al_2O_3 multilayr structure on Si(111) substrates by ICB method. The surface state and crystallinity were studied by STM,TEM and RHEED.It was found that the epitaxial growth of Al on Al_2O_3 and of Al_2O_3 on Al was achieved, and that the interface between Al and Al_2O_3 layrs was flat. In addition, we have succeeded to fabricate triple barrier resonant tunneling diodes using epitaxial Al/Al_2O_3 multilayr structures on Si(111) substrates and observed negative differential resistance. The resonant voltage was 1.22 V and the peak-valley ratio was 1.003. The value of resonant voltage agreed with the calculated value using Trasfer Matrix Method. The epitaxial Al/Al_2O_3 multilayr structure can be expected to be applied to quantum effect devices.