<i>In situ</i> synthesis of MgB2 thin films for tunnel junctions

Abstract

An approach to the in situ preparation of as-grown MgB2 thin films is presented. It comprises a conventional B sputter gun and a special Mg evaporator that provides a high Mg vapor pressure at the position of the substrate. Thin films deposited on r-plane sapphire substrates at a temperature of 440°C had a zero resistance Tc of 33K and a residual resistivity of 111μΩcm. Sandwich-type tunnel junctions with a natural MgB2 oxide as the potential barrier were prepared for superconducting tunneling spectroscopy. Voltage-dependent conductance measurements revealed estimates of the barrier thickness, height, and shape.