NANO EXPRESS Low Temperature Growth of In2O3 and InN Nanocrystals on Si(111) via Chemical Vapour Deposition Based on the Sublimation of NH4Cl in In

Indium oxide (In2O3) nanocrystals (NCs) have been obtained via atmospheric pressure, chemical vapour deposition (APCVD) on Si(111) via the direct oxidation of In with Ar:10% O2 at 1000 C but also at temperatures as low as 500 C by the sublimation of ammonium chloride (NH4Cl) which is incorporated into the In under a gas flow of nitrogen (N2). Similarly InN NCs have also been obtained using sublimation of NH4Cl in a gas flow of NH3. During oxidation of In under a flow of O2 the transfer of In into the gas stream is inhibited by the formation of In2O3 around the In powder which breaks up only at high temperatures, i.e. T [ 900 C, thereby releasing In into the gas stream which can then react with O2 leading to a high yield formation of isolated 500 nm In2O3 octahedrons but also chains of these nanostructures. No such NCs were obtained by direct oxidation for TG \ 900 C. The incorporation of NH4Cl in the In leads to the sublimation of NH4Cl into NH3 and HCl at around 338 C which in turn produces an efficient dispersion and transfer of the whole In into the gas stream of N2 where it reacts with HCl forming primarily InCl. The latter adsorbs onto the Si(111) where it reacts with H2O and O2 leading to the formation of In2O3 nanopyramids on Si(111). The rest of the InCl is carried downstream, where it solidifies at lower temperatures, and rapidly breaks down into metallic In upon exposure to H2O in the air. Upon carrying out the reaction of In with NH4Cl at 600 C under NH3 as opposed to N2, we obtain InN nanoparticles on Si(111) with an average diameter of 300 nm.