MgO nanowires synthesized at lower temperatures by metal organic chemical vapor deposition

MgO nanowires were synthesized on MgO(100) and Si(100) substrates by MOCVD with β-diketonate Mg(tmhd)2 (tmhd=2,2,6,6-tetramethyl-3,5-heptanedionate, with formula C₁₁H₁₉O₂). Very thin gold layers (<;5nm) were sputtered onto Si(100) and MgO(100) substrates, followed by heating at high temperatures to form catalyst clusters. The alignment of MgO nanowires on MgO(100) substrates are mainly along [100] but they are in [100] and [110] alignments on Si(100) substrate. Whatever the substrates are, the growth direction of a single nanowire is normally in<;001>; direction. The synthesis temperature, injection period, catalyst starting thickness, oxygen partial pressure and injection mass/period have strong effects on the synthesis and dimensions of nanowires. It shows that the quantity matching between the two reactive species (magnesium and oxygen) is very important for the vertical growth of nanowires. The quantity mismatching between the reactive species is subject to branching structures or totally kills the vertical alignments to be random ones. The synthesized MgO nanowires are needle-shaped with a decreasing diameter from the base to tip, which is probably due to the lateral growth as well as the catalyst diffusion during the synthesis.