MOLECULAR ROUTES TO COBALT ARSENIDE AND COBALT PHOSPHIDE THIN-FILMS -COMPARISON OF A 2-SOURCE AND A SINGLE-SOURCE CHEMICAL-VAPOR-DEPOSITION

Cobalt arsenide and phosphide thin films were prepared by organometall ic chemical vapour deposition (OMCVD) at deposition temperatures betwe en 300 and 500-degrees-C in a hot-wall reactor using a two-source meth od and a single-source method. The combination of tricarbonylnitrosylc obalt (-I) and di-t-butylphosphine or di-t-butylarsine was employed as a two-source method. The known hexacarbonyldicobalt clusters, Co2 (CO )6(mu-E2) (E = P, As), and the substituted dicarbonylnitrosylcobalt co mplexes, Co(CO)2 [E(tBu)2H](NO) (E = P, As), were used as single sourc e precursors. Auger electron spectroscopy indicated that the Co : P an d Co : As ratios in most of the films were near unity with only a smal l amount of impurities such as carbon and oxygen. Electrical resistivi ty of the films at room temperature ranged from 450 to 1140 muOMEGA-cm for cobalt phosphide and 115 to 1140 muOMEGA-cm for cobalt arsenide. X-ray diffraction analysis revealed that cobalt arsenide films were po lycrystalline, whereas cobalt phosphide films ranged from amorphous to polycrystalline. The grain size of the films ranged from 150 to 2000 angstrom measured by field-emission scanning electron microscopy. The film growth rate ranged from 4 to 30 angstrom min-1, for the single so urce methods and 150 to 330 angstrom min-1, for the two-source methods .