Low temperature growth of In 2O 3 and InN nanocrystals on Si(111) via chemical vapour deposition based on the sublimation of NH 4Cl in In
SourceNanoscale Research Letters
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Indium oxide (In 2O 3) nanocrystals (NCs) have been obtained via atmospheric pressure, chemical vapour deposition (APCVD) on Si(111) via the direct oxidation of In with Ar:10% O 2 at 1000 °C but also at temperatures as low as 500 °C by the sublimation of ammonium chloride (NH 4Cl) which is incorporated into the In under a gas flow of nitrogen (N 2). Similarly InN NCs have also been obtained using sublimation of NH 4Cl in a gas flow of NH 3. During oxidation of In under a flow of O 2 the transfer of In into the gas stream is inhibited by the formation of In 2O 3 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 O 2 leading to a high yield formation of isolated 500 nm In 2O 3 octahedrons but also chains of these nanostructures. No such NCs were obtained by direct oxidation for T G < 900 °C. The incorporation of NH 4Cl in the In leads to the sublimation of NH 4Cl into NH 3 and HCl at around 338 °C which in turn produces an efficient dispersion and transfer of the whole In into the gas stream of N 2 where it reacts with HCl forming primarily InCl. The latter adsorbs onto the Si(111) where it reacts with H 2O and O 2 leading to the formation of In 2O 3 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 H 2O in the air. Upon carrying out the reaction of In with NH 4Cl at 600 °C under NH 3 as opposed to N 2, we obtain InN nanoparticles on Si(111) with an average diameter of 300 nm.