Superconducting MgB2 thin films prepared by chemical vapor deposition from diborane

Superconducting MgB2 thin films have been prepared on Al2O3(1 - 102) substrate in a two-step ex situ approach. The precursor boron films were deposited by chemical vapor deposition from B2H6 at similar to495 degreesC, followed by post-annealing in magnesium (Mg) vapor at similar to800 degreesC. The annealed films have an onset transition temperature of 39 K and a zero resistance temperature of about 36 K, exhibiting a metallic behavior with a residual resistance ratio, RRR = R(300 K)/R(40 K), of 1.79. X-ray diffraction patterns indicate a highly c-axis-oriented crystal structure perpendicular to the substrate surface. Scanning electron microscopy shows the films consist of well-crystallized MgB2 grains and smooth surface. Having the advantage to prepare superconducting MgB2 thin films in large area and compatible with current semiconductor technology, our method may open new perspective for applications of MgB2 films. (C) 2002 Elsevier Science B.V. All rights reserved.