Electrical properties of NbN/NbNx/NbN Josephson Junctions
Electrical properties of NbN/NbNx/NbN Josephson Junctions
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NbN/NbNx/NbN 约瑟夫森结的电气特性
DOI：
10.1088/1361-6668/ac2eaf
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发表时间：
2021
影响因子：
3.6
通讯作者：
Zhen Wang
中科院分区：
文献类型：
--
作者：
Lu Zhang;Kaixin Yan;Yuanhe Tao;Yulong Zhong;Jiasheng Shi;Junwen Zeng;Weifeng Shi;Ling Wu;Huiwu Wang;Wei Peng;Lei Chen;Zhen Wang
在这项工作中，我们报告的NbN内分流约瑟夫森结与NbNx障碍的电气性能。横截面扫描透射电子显微镜分析表明，所有层具有相同的立方结构，NbN/NbNx/NbN三层外延生长在MgO衬底上。通过控制反应溅射过程中的N2分压和沉积时间，NbNx薄膜的电阻率可以在1 ~ 104 mΩ cm范围内变化。测量了不同势垒厚度下不同势垒电阻率的结的临界电流密度（JC）和特征电压（IcRn）随温度的变化关系。对于具有73.44、385.72和711 mΩ cm的折射率的10 nm厚的NbNx层，势垒的相干长度分别被确定为5.55±0.07、4.88±0.06和1.40±0.13 nm，对应于2.741±0.004、1.211±0.002、1.211± 0.003和1.211± 0.004的载流子扩散速率。和0.008±0.001 cm 2 s-1。因此，势垒电阻率的降低导致更大的相干长度和更快的扩散速率，这将进一步增加结的Jc和IcRn。通过调节势垒电阻率和厚度，可以很容易地将结的Jc调节到4个数量级以上，在10 K时获得了0.97 ± 0.0 7 mV的IcRn值结果表明，全NbN自分流结在高速高温应用中是一种很有前途的候选结。
In this work, we report the electrical properties of NbN internally shunted Josephson junctions with NbN x barriers. Cross-sectional scanning transmission electron microscopy analysis shows that all layers have the same cubic structure; NbN/NbN x/NbN trilayers were epitaxially grown on MgO substrates. The resistivity of the NbN x films could be varied in the range of 1–10 4 mΩ cm by controlling both the N 2 partial pressure and the deposition time during reactive sputtering. The temperature dependence of the critical current density (J c) and characteristic voltage (I c R n) of the junctions with different barrier resistivities were measured for various barrier thicknesses. For the 10 nm-thick NbN x layer with resistivities of 73.44, 385.72, and 711 mΩ cm, the coherence length of the barrier was determined to be 5.55±0.07, 4.88±0.06, and 1.40±0.13 nm, respectively, corresponding to carrier diffusion rates of 2.741±0.004, 1.211±0.002, and 0.008±0.001 cm 2 s− 1, respectively. Thus, the reduction in barrier resistivity leads to a larger coherence length and a faster diffusion rate, which will further increase the J c and I c R n of the junction. By adjusting the barrier resistivity and thickness, the J c of the junction can be easily tuned over more than four orders of magnitude, and an I c R n value of 0.97±0.07 mV was obtained at 10 K. The results indicate that the all-NbN self-shunt junction is a promising candidate in high-speed and high-temperature applications.