Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy
Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy
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DOI：
10.1063/1.4759019
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发表时间：
2012-10-15
影响因子：
3.2
通讯作者：
Semba, Kouich
中科院分区：
文献类型：
--
作者：
Krockenberger, Yoshiharu;Karimoto, Shin-ichi;Semba, Kouich
研究了分子束外延和射频激活氮等离子体在(001)MgO衬底上形成氮化钛(TiN)薄膜的过程。虽然立方TiN在很宽的温度范围内是稳定的，但只有在衬底温度超过710℃时才能获得超导TiN薄膜。在720℃生长的TiN薄膜具有大约11的高剩余电阻率比，超导转变温度(T-c)远高于5K。超导电性也得到了磁化测量的证实。此外，我们还通过强磁场下的输运测量确定了上临界磁场(muH-0(C2))以及相应的相干长度(xi(Gl))。高分辨透射电子显微镜数据显示薄膜与衬底完全平面共格，并且薄膜中的缺陷密度很低，这与L的平均自由光程长度约为106 nm相一致，这是根据剩余电阻率值估计的。观察到生长过程中反射高能电子衍射强度的振荡，布拉格主峰周围清晰的劳厄条纹，以及倒易空间图中的高阶衍射斑，表明高质量超导TiN薄膜的厚度是完全可控的。(C)2012年美国物理研究所。[http://dx.doi.org/10.1063/1.4759019]
We have investigated the formation of titanium nitride (TiN) thin films on (001) MgO substrates by molecular beam epitaxy and radio frequency acitvated nitrogen plasma. Although cubic TiN is stabile over a wide temperature range, superconducting TiN films are exclusively obtained when the substrate temperature exceeds 710 degrees C. TiN films grown at 720 degrees C show a high residual resistivity ratio of approximately 11 and the superconducting transition temperature (T-c) is well above 5K. Superconductivity has been confirmed also by magnetiztion measurements. In addition, we determined the upper critical magnetic field (mu H-0(c2)) as well as the corresponding coherence length (xi(GL)) by transport measurements under high magnetic fields. High-resolution transmission electron microscopy data revealed full in plane coherency to the substrate as well as a low defect density in the film, in agreement with a mean-free path length l approximate to 106 nm, which is estimated from the residual resistivity value. The observations of reflection high energy electron diffraction intensity oscillations during the growth, distinct Laue fringes around the main Bragg peaks, and higher order diffraction spots in the reciprocal space map suggest the full controlability of the thickness of high quality superconducting TiN thin films. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759019]