CVD growth and morphology of transition-metal phosphides

Whiskers of β-HfP (hexagonal), α-ZrP (cubic), and β-TiP (hexagonal) have been prepared from HfCl4/ZrCl4/TiCl4 + PCl3 + H2 + Ar gas mixtures at 1050–1250°C using the mixed-metal impurity-activated chemical-vapor-deposition process. The growth conditions, morphology, and other properties were examined. The mixed impurities of Si + Pt and Si + Pd were very effective for the growth of these whiskers. The growth direction of HfP and TiP is the c-axis, and that of ZrP is 〈111〉 and the a-axis. Some whiskers changed their growth axes from one orientation to another during growth. The whiskers were very stable during a 40 min immersion in a concentrated HCl solution.