Synthesis of gallium nitride nano-wires on nickel-alumina composites from gallium oxide powder under a low partial pressure of ammonia

GaN nanowires were synthesized on silicon, nickel nitrate [Ni(NO₃)₂]-dispersed silicon, and a nickel-dispersed alumina (Ni/Al₂O₃) composite under an argon atmosphere containing a low partial pressure of ammonia (PNH3 = 10 kPa). GaN nanowires were formed on the Ni(NO₃)₂-dispersed silicon and Ni/Al₂O₃ composite substrates. Two kinds of nanowires with different morphologies were observed. Initially, the formation of rough-surfaced nanowires occurred, which was followed by the formation of smoothsurfaced nanowires. In the case of the Ni/Al₂O₃ composite, GaN nanowires with rough surfaces were formed after 15 min at 1000°C, and the number of nanowires increased with the holding time. TEM observations showed that the nanowires grew in the [100] direction, which supported the proposed vapor-liquid-solid growth mechanism.