Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer
Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer
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DOI：
10.1088/0953-2048/23/4/045004
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发表时间：
2010-04-01
影响因子：
3.6
通讯作者：
Yamamoto, Satoshi
中科院分区：
文献类型：
--
作者：
Shiino, Tatsuya;Shiba, Shoichi;Yamamoto, Satoshi
薄的超导型NBTIN和NBN薄膜具有几个NM厚度，包括在包括热电子钢计搅拌机中的各种设备应用中。这种薄膜的临界温度（t（c））较低，电阻率较高，而电阻率较高。为了改善它们，我们研究了膜和底物（石英或苏打石灰玻璃）之间ALN缓冲层的影响。 ALN膜通过DC磁控溅射沉积，并优化了过程条件，因此从Wurtzite Aln的002表面的X射线衍射强度变为最高。与没有缓冲层的那些相比，通过使用该特征良好的缓冲层，T（c）和厚度为NM厚度的NBTIN膜的电阻率分别大大增加和减少。更重要的是，发现ALN缓冲层对NBN有效。使用ALN缓冲层，对于8 nm NBN膜，T（C）从7.3增加到10.5 K。 t（c）和电阻率的改善起源于ALN 002表面与NBTIN或NBN的111表面之间的良好晶格匹配，从而可以更好地结晶NBTIN或NBN膜。 X射线衍射测量进一步证实了这一点。
Thin superconducting NbTiN and NbN films with a few nm thickness are used in various device applications including in hot electron bolometer mixers. Such thin films have lower critical temperature (T(c)) and higher resistivity than corresponding bulk materials. In an effort to improve them, we have investigated an effect of the AlN buffer layer between the film and the substrate (quartz or soda lime glass). The AlN film is deposited by DC magnetron sputtering, and the process condition is optimized so that the x-ray diffraction intensity from the 002 surface of wurtzite AlN becomes the highest. By use of this well-characterized buffer layer, T(c) and the resistivity of the NbTiN film with a few nm thickness are remarkably increased and decreased, respectively, in comparison with those without the buffer layer. More importantly, the AlN buffer layer is found to be effective for NbN. With the AlN buffer layer, T(c) is increased from 7.3 to 10.5 K for the 8 nm NbN film. The improvement of T(c) and the resistivity originates from the good lattice matching between the 002 surface of AlN and the 111 surface of NbTiN or NbN, which results in better crystallization of the NbTiN or NbN film. This is further confirmed by the x-ray diffraction measurement.