High-T_c superconducting NbN films with low particulate density grown at 25 °C using pulsed laser deposition

The growth and characterization of high-T_c NbN films formed on room temperature substrates by pulsed laser deposition is described. The growth was performed at a high laser power density (>5 × 10⁸ W/cm²), where the enhanced reactivity of species in the plume is proposed as the mechanism for increased nitrogen incorporation in films on unheated substrates. The T_cs were 16.2 K on MgO and 13 K on SiN_x/Si substrates. In addition to electrical transport measurements, the films were characterized using RBS and x-ray diffraction. The particulate density on films grown at high power density was significantly reduced, which is correlated with the Nb target having a smoother morphology, characteristic of a quenched molten surface layer in the ablated area.