Impurity Metal-Activated Crystal Growth of Niobium Monophosphide from Gas Phase

Abstract

Abstract Niobium monophosphide single crystals were obtained by chemical vapor deposition from a gas mixture of NbCl5, PCl3, H2, and Ar on a quartz substrate using metallic impurity. The existence of Au, Pt, Pd, and Ni resulted in the growth of whiskers or pillar crystals. Maximum whisker length of 5 mm and thickness of 30 μm were obtained at 1150 °C for an hour with the use of Pt impurity. Platelet crystals (400×1000×20 μm, max.) were obtained with the use of Pt at 1240 °C. The growth directions of the whiskers and some platelet crystals were assigned to 〈001〉 and a direction in (001) plane, respectively. The optimum growth conditions for the pillar crystals in the case of Ni impurity: substrate temperature 1000–1020 °C, gas flow ratio PCl3/(NbCl5+PCl3) of 0.7–0.75. From observation of the tip and base of pillar crystals grown with Ni, the growth mechanism seems to be base VLS followed by VS.