Papageorgiou et al. Nanoscale Research Letters 2011, 6:311 http://www.nanoscalereslett.com/content/6/1/311 N A N O E X P R E S S Open Access An investigation into the conversion of In O into 2 3 InN nanowires Polina Papageorgiou1, Matthew Zervos2* and Andreas Othonos1 Abstract Straight In2O3 nanowires (NWs) with diameters of 50 nm and lengths ≥2 μm have been grown on Si(001) via the wet oxidation of In at 850°C using Au as a catalyst. These exhibited clear peaks in the X-ray diffraction corresponding to the body centred cubic crystal structure of In2O3 while the photoluminescence (PL) spectrum at 300 K consisted of two broad peaks, centred around 400 and 550 nm. The post-growth nitridation of In2O3 NWs was systematically investigated by varying the nitridation temperature between 500 and 900°C, flow of NH3 and nitridation times between 1 and 6 h. The NWs are eliminated above 600°C while long nitridation times at 500 and 600°C did not result into the efficient conversion of In2O3 to InN. We find that the nitridation of In2O3 is effective by using NH3 and H2 or a two-step temperature nitridation process using just NH3 and slower ramp rates. We discuss the nitridation mechanism and its effect on the PL. Introduction Group III-Nitride (III-N) semiconductors have been investigated extensively over the past decades due to their applications as electronic and optoelectronic devices. In addition, they are promising for the realiza- tion of high efficiency, multi-junction solar cells since their band-gaps vary from 0.7 eV in InN through to 3.4 eV in GaN up to 6.2 eV in AlN; thereby, allowing the band gaps of the ternaries InxGa1-xN and AlxGa1-xN to be tailored in between by varying x. Nanowires solar cells (NWSCs) are also receiving increasing attention but so far they have been fabricated from Si and metal- oxide (MO) NWs. Nitride NWs such as InN [1], GaN [2] and AlN [3] are, therefore, promising for the realiza- tion of full-spectrum third generation NWSCs. However, their growth and properties must be understood before- hand in order to make nanoscale devices. So far we have grown InN [1] and GaN NWs [2] using the direct reaction of In or Ga with NH3, while more recently we showed that Ga2O3 NWs may be converted to GaN by post-growth nitridation using NH3 and H2 [4]. Here, we have undertaken a systematic investigation into the conversion of In2O3 to InN NWs, which has not been * Correspondence: zervos@ucy.ac.cy 2Nanostructured Materials and Devices Laboratory, Department of Mechanical Engineering, Materials Science Group, School of Engineering, University of Cyprus, P.O. Box 20537, Nicosia, 1678, Cyprus. Full list of author information is available at the end of the article carried out previously by others, thereby complement- ing our earlier work on the conversion of Ga2O3 to GaN NWs. Therefore, we have grown straight In2O3 NWs with diameters of 50 nm and a high yield and uniformity. We find that the post-growth nitridation of In2O3 NWs using NH3 leads to the elimination of the NWs above 600°C. The In2O3 NWs are preserved for temperatures less than 700°C but are not converted into InN even after long nitridation times of 6 h. However, the nitrida- tion process was enhanced significantly via the use of H2 or by employing a two-step temperature nitridation process, which also lead to a suppression of the photolu- minescence (PL) peak at 550 nm similar to the nitrida- tion of Ga2O3 NWs [4]. Experimental method Initially In2O3 NWs were grown using an atmospheric pressure chemical vapour deposition (APCVD) reactor described elsewhere [5]. For the growth of In2O3 NWs, 0.2 g of fine In powder (Aldrich, Cyprus, Mesh 100, 99.99%) was weighed and loaded in a quartz boat, while square pieces of n+ Si(001) ≈ 7 mm × 7 mm, coated with ≈1.0 nm of Au, were loaded at various distances from the In. The Au layer was deposited via sputtering using Ar under a pressure of ≈10-2 mBar. The boat was positioned directly above the thermocouple used to measure the heater temperature at the centre of the 1” © 2011 Papageorgiou et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.