2015 Fiscal Year Annual Research Report
全窒化物誘電体材料と基板を用いたエピタキシャル超伝導量子ビットの作製
| Project/Area Number |
25420352
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| Research Institution | National Institute of Information and Communications Technology |
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Principal Investigator |
丘 偉 国立研究開発法人情報通信研究機構, 未来ICT研究所ナノICT研究室, 研究員 (90535189)
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| Project Period (FY) |
2013-04-01 – 2016-03-31
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| Keywords | Superconducting / TiN / NbN / CPW / Quality factor / Dielectric loss / Epitaxial |
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| Outline of Annual Research Achievements |
We studied the dielectric loss in epitaxially grown superconducting NbN resonator on single crystal Si (100) substrates with a thin TiN film served as the buffer layer.
The superconducting thin film resonator based on epitaxial TiN has shown a significant improvement in dielectric loss of 2.25x10e-6 compares to the loss of 1x10e-4 from epitaxial NbN resonator developed on single crystal MgO substrate. However, Josephson tunnel junction devices directly developed from multi-layer TiN/AlN/TiN on Si substrate show poor characteristics partially due to the relatively bad surface roughness (> 0.5 nm) of barrier material -AlN during the process. In order to improve the junction quality, we developed epitaxial NbN/TiN thin film structure on Si-substrate as the TiN (~ 50 nm) served as a buffer layer to deposit epitaxial (200) NbN (> 200nm) on top.
From the standpoint of superconducting qubit development, both high quality junction devices and low dielectric loss from the overall circuit play crucial roles. To examine the loss in this newly developed NbN/TiN thin film structure. We developed epitaxial NbN/TiN coplanar waveguide (CPW) microwave resonator circuit on Si-substrate. The circuit includes a series of quarter-wavelength meandered CPW transmission line resonator. The epitaxial NbN/TiN resonator shows a further improvement in dielectric loss of 1.82x10e-6 compares to epitaxial TiN resonator.
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Research Products
(5 results)
