Vapor–Solid growth of InP and Ga2O3 based composite nanowires

Abstract

InP/Ga 2 O 3 core-shell nanowires were grown on Si substrate at 400 oC in the hydrazine (N 2 H 4 ) vapor diluted with 3 mol. % H 2 O. The crystalline InP and solid Ga served as source materials for the growth of nanowires. According to TEM and EDX data the nanowires consisted of wurtzite InP core with an amorphous Ga 2 O 3 shell. The minimum diameter of NWs was 14 nm, while the maximum lengths reached several micrometers. The twinned planes appeared in WZ InP core at increased nanowire diameters. Based on the obtained results and possible chemical reactions, the following mechanism was proposed for the growth of core-shell nanowires: pyrolytic decomposition of hydrazine caused the appearance of intermediate NH 2 , NH and H species in the vapor. At elevated temperatures the crystalline InP source was also dissociated to In droplets and phosphorus precursors. At source temperatures close to 600 oC, due to the interaction of In and Ga sources with water molecules and hydrazine decomposition products the volatile Ga 2 O and In 2 O were formed. These molecules reached the Si substrate which was heated to 400oC. The final chemical reaction involved Ga 2 O 3 , I 2 O 3 and phosphorus precursors. As a result of a spontaneous reaction the Ga 2 O 3 and InP phases were produced and segregated. The InP crystallized as a core while Ga 2 O 3 created the amorphous shell, because the growth temperature was insufficient for its crystallization.