Comparative study of electrical properties of chalcogenide films produced by reaction of Cu, Ag, Ni and NiCu with Sb2S3 in hot wall epitaxy

Abstract

Films of transition-metal–chalcogen alloys are produced using hot wall epitaxy by means of sulphurization in the exposure of Cu, Ag, Ni and NiCu films to Sb2S3 vapor. The properties of the resultant chalcogenide films change widely depending on the material combination and the synthesis conditions. We investigate the influences of the coexistence of Sb in the alloys on the electrical properties of the films. The Ni-containing films are highly conductive, whereas the resistivity of the films produced from Cu and Ag is large. The sulphurization occurs two-dimensionally as homogeneous films consisting of Cu-Sb-S and Ag-Sb-S ternary alloys, giving rise to weak and negligible dependencies of the resistivity on the synthesis temperature in the respective cases. The thermal activation energy for the electrical transport varies in correspondence to the resistivity values. The Cu- and Ag-based films exhibit a suppression of current when Ag electrodes are used in comparison to using Au electrodes. The transient of photocurrent is shown for these films to be remarkably slow with an order of magnitude change of the current. The spontaneous reaction with Al contacts to trigger interfacial resistance switching is weak for the Sb-containing materials. The structural properties of the films are furthermore presented together with the Raman spectra to identify the synthesized alloys. A catalytic effect of Ni in the sulphurization of Cu and the surfactant effect of Sb are thereby revealed.