Figure 5.

Resistivity versus temperature plots of MgB₂ films of different thicknesses. The unetched 80 ± 4 nm thick film (red) has the highest superconducting transition temperature, T_c,0 = 33.3 K, followed by the film etched back to 38.5 ± 2.1 nm in thickness (orange) with T_c,0 = 30.1 K, followed by the film etched back to 22.4 ± 1.1 nm in thickness (green) with T_c,0 = 25.9 K, followed by the film etched back to 11.4 ± 0.6 nm in thickness (blue) with T_c,0 = 25.7 K, and followed by the film etched back to 6.9 ± 0.4 nm in thickness (navy) with T_c,0 = 21.4 K.