{"title":"Fabrication of NbN/Al-AlNx/NbN tunnel junctions on several kinds of substrates","authors":"H. Akaike, T. Funai, Shunya Sakamoto, A. Fujimaki","doi":"10.1109/ISEC.2013.6604313","DOIUrl":null,"url":null,"abstract":"We have evaluated the electrical characteristics of NbN/Al-AlN<sub>x</sub>/NbN tunnel junctions fabricated on sapphire-C or fused-silica substrates. NbN/Al-AlN<sub>x</sub>/NbN multilayers were prepared by reactive dc-magnetron sputtering deposition of lower and upper NbN layers, and rf-magnetron sputtering deposition of the Al layer, followed by radical-nitridation. The junctions showed low sub-gap leakage currents in the current-voltage characteristics at 4.2 K. The quality parameter, R<sub>sg</sub>/R<sub>n</sub>, where respective R<sub>sg</sub> and R<sub>n</sub> are the sub-gap resistance at 2 mV and junction resistance at 5 mV, was above 15. The gap voltage (V<sub>g</sub>) was around 3.3 mV, which was reduced in comparison with V<sub>g</sub> values of ~4.3 mV for junctions on MgO substrates. The reduced V<sub>g</sub> was caused by superconducting properties of lower NbN layers deposited on the sapphire or fused-silica substrates. Uniformity in critical current (I<sub>c</sub>) was relatively good, and the maximum-to-minimum spread in I<sub>c</sub> was ±1.7% for 200 junctions on a sapphire substrate and ±2.0% for the junctions on a fused-silica substrate.","PeriodicalId":233581,"journal":{"name":"2013 IEEE 14th International Superconductive Electronics Conference (ISEC)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2013-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"4","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"2013 IEEE 14th International Superconductive Electronics Conference (ISEC)","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1109/ISEC.2013.6604313","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 4
Abstract
We have evaluated the electrical characteristics of NbN/Al-AlNx/NbN tunnel junctions fabricated on sapphire-C or fused-silica substrates. NbN/Al-AlNx/NbN multilayers were prepared by reactive dc-magnetron sputtering deposition of lower and upper NbN layers, and rf-magnetron sputtering deposition of the Al layer, followed by radical-nitridation. The junctions showed low sub-gap leakage currents in the current-voltage characteristics at 4.2 K. The quality parameter, Rsg/Rn, where respective Rsg and Rn are the sub-gap resistance at 2 mV and junction resistance at 5 mV, was above 15. The gap voltage (Vg) was around 3.3 mV, which was reduced in comparison with Vg values of ~4.3 mV for junctions on MgO substrates. The reduced Vg was caused by superconducting properties of lower NbN layers deposited on the sapphire or fused-silica substrates. Uniformity in critical current (Ic) was relatively good, and the maximum-to-minimum spread in Ic was ±1.7% for 200 junctions on a sapphire substrate and ±2.0% for the junctions on a fused-silica substrate.