Characterisation of amorphous molybdenum silicide (MoSi) superconducting thin films and nanowires
Characterisation of amorphous molybdenum silicide (MoSi) superconducting thin films and nanowires
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DOI：
10.1088/1361-6668/aa76d8
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发表时间：
2017-08-01
影响因子：
3.6
通讯作者：
Hadfield, Robert H.
中科院分区：
文献类型：
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作者：
Banerjee, Archan;Baker, Luke J.;Hadfield, Robert H.
我们报道了用于超导纳米线单光子探测器(SNSPD)的非晶态硅化钼薄膜的优化生长。在Ar气氛中用Mo和Si靶共溅射沉积了硅化钼薄膜。测量了超导转变温度(T-c)和方块电阻(R-S)随厚度的变化，并与几种无序超导膜的理论模型进行了比较。非晶态材料的超导和光学性质对原子结构中的短程(长达1 nm)和中程(类似于1-3 nm)非常敏感。起伏电子显微镜研究表明，薄膜呈现出类似A15的中程有序。电子能量损失谱表明薄膜的化学计量比接近Mo83Si17，这与其他许多名义公式为A(3)B的A15结构显示出显著的A：B>；3：1的非化学计量比的报道是一致的。通过椭圆偏振光谱测量了5 nm厚的MoSi薄膜从紫外光(270 Nm)到红外(2200 Nm)的光学性质，显示出高的长波吸收。我们还测量了由10 nm厚的MoSi薄膜图案化的纳米线的电流密度随温度的变化。在3.6K下，最宽的丝(2003 Nm)的电流密度为3.6×10(5)A cm(-2)，最窄的丝(173 Nm)的电流密度为2×10(5)A cm(-2)。这项研究证实了MoSi对SNSPD应用的极佳适应性，并使人们对底层材料的性能有了新的了解。
We report on the optimisation of amorphous molybdenum silicide thin film growth for superconducting nanowire single-photon detector (SNSPD) applications. Molybdenum silicide was deposited via co-sputtering from Mo and Si targets in an Ar atmosphere. The superconducting transition temperature (T-c) and sheet resistance (R-s) were measured as a function of thickness and compared to several theoretical models for disordered superconducting films. Superconducting and optical properties of amorphous materials are very sensitive to short- (up to 1 nm) and medium-range order (similar to 1-3 nm) in the atomic structure. Fluctuation electron microscopy studies showed that the films assumed an A15-like medium-range order. Electron energy loss spectroscopy indicates that the film stoichiometry was close to Mo83Si17, which is consistent with reports that many other A15 structures with the nominal formula A(3)B show a significant non-stoichiometry with A:B > 3:1. Optical properties from ultraviolet (270 nm) to infrared (2200 nm) wavelengths were measured via spectroscopic ellipsometry for 5 nm thick MoSi films indicating high long wavelength absorption. We also measured the current density as a function of temperature for nanowires patterned from a 10 nm thick MoSi film. The current density at 3.6 K is 3.6 x 10(5) A cm(-2) for the widest wire studied (2003 nm), falling to 2 x 10(5) A cm(-2) for the narrowest (173 nm). This investigation confirms the excellent suitability of MoSi for SNSPD applications and gives fresh insight into the properties of the underlying materials.