Crystalline oxide tunnel barriers formed by thermal oxidation of aluminum overlayers on superconductor surfaces
Crystalline oxide tunnel barriers formed by thermal oxidation of aluminum overlayers on superconductor surfaces
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超导体表面铝覆盖层热氧化形成的晶体氧化物隧道势垒
DOI：
10.1063/1.337209
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
J. Gavaler
中科院分区：
文献类型：
--
作者：
A. Braginski;J. Talvacchio;M. Janocko;J. Gavaler
通过在四种难熔超导体：Nb、Mo - Re、Nb3Sn和NbN的单晶和多晶薄膜上热氧化薄铝层形成了晶体氧化物隧道垒。隧道结主要由Pb‐Bi和Nb、Mo‐Re和NbN反电极组成。基电极结晶度、表面粗糙度、氧亲和性和天然氧化物性质的差异影响了平均势垒高度、亚隙和正常（高于间隙）电导以及微短路的发生。还注意到层沉积方法（蒸发与溅射）的影响。通过对不同基极上得到的势垒和离子铣削非晶化势垒性能的比较，发现非晶化势垒比晶化和外延化势垒更均匀，更能代表Al2O3。后者的特性部分是由分流的天然氧化物通道定义的，这种通道是由硼的不均匀覆盖造成的。
Crystalline oxide tunnel barriers were formed by thermal oxidation of thin Al overlayers on single‐crystal and polycrystalline films of four refractory superconductors: Nb, Mo‐Re, Nb3Sn, and NbN. Tunnel junctions were fabricated mostly with Pb‐Bi and also with Nb, Mo‐Re, and NbN counterelectrodes. Differences in the base electrode crystallinity, surface roughness, oxygen affinity, and native oxide properties influenced the average barrier height, the subgap and normal (above‐gap) conductance and the occurrence of microshorts. An effect of the overlayer deposition method (evaporation versus sputtering) was also noticed. The comparison of properties of barriers obtained on different base electrodes and of those amorphized by ion milling lead to the observation that amorphous barriers are more uniform and representative of Al2O3 than the crystalline and epitaxial barriers. The properties of the latter are defined, in part, by the shunting native oxide channels which result from a nonuniform coverage of the b...