Investigation of dimensionality in superconducting NbN thin film samples with different thicknesses and NbTiN meander nanowire samples by measuring the upper critical field

Nazir Mudassar^{1, 2}, Yang Xiaoyan³, Tian Huanfang¹, Song Pengtao^{1, 2}, Wang Zhan^{1, 2}, Xiang Zhongcheng¹, Guo Xueyi¹, Jin Yirong¹, You Lixing³, Zheng Dongning^{1, 2, 4, †}

Superconducting resistive transition curves under applied magnetic field 0 up to 9 T at different angles for (a) NbN 4 nm at temperature 7.8 K and (b) NbTiN 5 nm at 7.8 K. The upper critical field is defined at half of residual resistance and its angular dependence is shown for (c) NbN 4 nm and (d) NbTiN 5 nm nanowire. The sharp peak is seen at θ = 90° for given samples which is fitted with the 2D Tinkham and 3D anisotropic formulas given in Eqs. (4) and (5) as indicated by the red and blue solid lines, respectively. The black circles represent the experimental data. The inset shows a zoom-in view of the region around θ = 90°.