Papageorgiou et al. Nanoscale Research Letters 2011, 6:311 http://www.nanoscalereslett.com/content/6/1/311 have diameters of ≈50 nm, lengths ≥2 μm and exhibited clear peaks in the XRD as shown in Figure 2 by the top curve, corresponding to the body centred cubic (bcc) crystal structure of In2O3 with a = 10.12 Å, in agree- ment with Dai et al. who obtained twisted In2O3 NWs by wet oxidation [8]. The In2O3 NWs shown in Figure 1 are straight [9,10] and in our case In2O3 NWs grow by a simple chemical route involving the following reaction: 2In + 3H2O ® In2O3 + 3H2 [8]. Wet oxidation is a facile method and generally occurs faster than dry oxi- dation. No NWs were obtained on plain Si(001), sug- gesting the growth of In2O3 NWs occurs via the vapour-liquid-solid (VLS) mechanism with Au acting as the catalyst. In this case, Au NPs absorb In until they become supersaturated after which In2O3 NW growth commences via the reaction of In with H2O as outlined above. The PL spectrum following excitation at 267 nm at 300 K consisted of two broad peaks, centred at 400 and 550 nm as shown in Figure 3 Similar peaks in the PL have been observed by Yan et al. [11] who obtained a broad luminescence band centred at 395 nm from In2O3 nanorods, Liang et al. [12] who found a peak at 470 nm from In2O3 nanofibres and Wu et al. [13] who observed two distinct peaks at 416 and 435 nm from In2O3 nanowires. It is important to point out that these peaks are commonly attributed to the presence of oxy- gen vacancies. Next, we will describe the conversion of In2O3 NWs into InN and in particular consider the nitridation of In2O3 NWs at different temperatures. To begin with In2O3 NWs were subjected to 250 sccm of NH3 for 1 h Figure 2 XRD of In2O3 NWs obtained after nitridation at different temperature as listed in Table 1. Note that CVD841 shown at the top corresponds to the as grown In2O3 NWs. The InN related peaks are shown in bold, while the Al peaks belong to the holder and have also been identified. Page 3 of 5 Figure 3 PL spectrum of In2O3 NWs as grown and after nitridation using NH3 only or NH3 and H2. at various temperatures between 500 and 900°C as listed in Table 1. The XRD spectra of the In2O3 NWs treated at differ- ent temperatures is shown in Figure 2. As can be seen most of the oxide peaks disappear at temperatures >600°C. However, a new peak appears, which corre- sponds to the (101) crystallographic direction of InN [1]. Furthermore, SEM images reveal that the In2O3 NWs have been eliminated above 600°C, but a thin layer of InN remains on the Si(001). Evidently, the nitridation of the In2O3 NWs is destructive above 600°C due to the fast decomposition of In2O3 to In2O, which is a gas. We should also point out that in addition to the tempera- ture we also varied the nitridation time. In particular, we carried out nitridations of In2O3 NWs at 500 and 600°C under a flow of 125 sccm NH3 for different times as described in Table 1. Again the conversion of In2O3 NWs to InN appears to be incomplete as can be clearly seen from the XRD spectra in Figure 4 where one can observe the presence of In2O3 peaks and just one peak at (101) corresponding to InN. In order to achieve the efficient conversion of In2O3 NWs to InN without eliminating them, we used two different approaches. In the first one, we have car- ried out post-growth nitridation, which included H2 as shown in Table 1 and in the second approach, we have utilised a two-step temperature nitridation process. The corresponding XRD spectra are shown in Figure 5. As can be seen from the XRD spectra, H2 plays a significant role in the removal of the oxygen and thus all major oxide peaks are eliminated and the conversion to InN is achieved with 40% H2. As already described above, NH3 alone does not promote the efficient conversion of In2O3 NWs into InN at temperatures between 500 and