Spectral decomposition of Si 2p spectrum of Si NWs sample GM6001 cell line annealed at 500°C for 60 min, having all the relevant suboxide and silicon peaks (Si 2p3/2 in dark green and Si 2p1/2 in light green). The black line is the original spectrum, while the red graph represents the fitting curve which see more is sum of all of the decomposed peaks and fit well the experimentally obtained spectrum. The amount of each of suboxides, relative to the amount of intact silicon, can be calculated by dividing the integrated area under the suboxide’s peak (A SiOx) by the sum of the integrated area under Si 2p 1/2 and Si 2p 3/2 peaks (A Si 2p1/2 +
A Si 2p3/2). The resulting value is called suboxide intensity, shown by I SiOx. In addition, total oxide intensity (I ox) can be calculated as the sum of all the four suboxide intensities (I ox = I Si2O + I SiO + I Si2O3 + I SiO2). Oxide intensity can also be expressed in number of monolayers, regarding the fact that each 0.21 of oxide intensity corresponds
to one BAY 11-7082 mw oxide monolayer [17]. The total oxide intensity, besides suboxide intensities for the Si NWs specimens annealed at 150°C and 400°C, is listed in Table 1. Except SiO2, all the suboxide intensities for both of the annealing temperatures are comparable and more or less show very slight variations over the annealing time. However, at 150°C, suboxides hold a larger share of the total oxide intensity whereas at 400°C, SiO2 mainly contributes to the overall oxide amount detected. Table 1 Intensity of the silicon suboxides for the samples annealed at 150°C and 400°C T = 150°C T = 400°C Intensity/oxidation time (min) 5 10 20 30 60 5 10 20 30 60 Si2O 0.317 0.269
0.252 0.289 0.198 0.235 0.227 0.186 0.212 0.249 SiO 0.067 0.092 0.102 0.151 0.148 0.107 0.089 0.142 0.095 0.104 Si2O3 0.026 0.078 0.076 0.126 0.088 0.157 0.077 0.149 0.139 0.083 SiO2 0.228 0.350 0.414 0.666 0.787 1.181 1.390 1.569 1.604 1.922 Total 0.640 0.790 0.845 1.234 1.223 1.680 1.785 2.047 2.052 2.360 Variation in the total oxide intensity (I ox) for all the six temperatures over oxidation time up to 60 min is shown in Figure 3. For both the high temperature (T ≥ 200°C) and low-temperature oxidation (T < 200°C), the Sclareol oxide intensity reaches a saturation level beyond which the oxide amount grows negligibly. However, in low-temperature oxidation, the time to reach 80% of the saturation levels (defined as Γsat) is in the range of 20 to 30 min, whereas in high-temperature oxidation it ranges from 8 min to 12 min. Average Γsat for high- and low-temperature oxidation are marked in Figure 3 by dashed and dotted lines, respectively. This indicates roughly both similarities and differences between the underlying oxidation mechanisms in these two temperature ranges.