(a) Relative contribution of the HF (Si-NC) and LF (a-Si) Raman bands to the total scattering intensity is shown as a function of r H. (b) Integrated Raman intensities of HF (Si-NC) and LF (a-Si) bands are shown as a function of absorption coefficient. Pearson’s correlation coefficients have been also shown for a-Si and Si-NC. Figure 2b shows the integrated Raman intensities of Si-NCs and a-Si bands as a function of absorption

coefficient selleck chemicals llc (α). The absorption coefficient was determined at 4 eV (high-energy part of the absorption spectra). It can be seen that there is a linear correlation between α and the Raman intensity for Si-NCs as well as a-Si, with correlation coefficient equal to 0.98 and 0.97, respectively. Since both the Raman intensity and α depend linearly on the number of nanoparticles (e.g., Si-NCs), the obtained correlation indicates that the high-energy absorption is related to both: Si-NCs Selleck MLN4924 and a-Si. It should be also noted here that we obtained a strong correlation for the whole high-energy part of the absorption spectra (between 3 and 5 eV). Moreover, the correlation coefficient calculated for Si-NCs was always slightly higher than for a-Si. On the other hand, when energy drops approximately below 2.5 eV, the correlation coefficient also drops below 0.7. This result can be expected if we bear in mind that the estimated optical band gap exceeds 2.5 eV for all

of the investigated structures (see Table 1). This result may also indicate that the low-energy part of the absorption spectra is (at least partially) related to some different structures e.g., defects in

the matrix. In order to explore the matrix properties for more details, we conducted FTIR measurements in ATR mode. Figure 3 shows normalized IR spectra obtained for the samples deposited with different r H. To compare, Figure 3 also contains a reference spectrum measured for pure quartz. In each case, the main band located in the range 1,000 to 1,300 cm−1 is associated with the asymmetric stretching GNA12 Si-O-Si mode [23], where the bridging oxygen atoms move in the direction opposite to their Si neighbors and roughly parallel to the Si-Si lines. Moreover, the band around 800 cm−1 is identified as the bending Si-O-Si vibration [23] in which the oxygen move approximately at right angles to the Si-Si lines and in the Si-O-Si planes. Figure 3 Normalized FTIR spectra measured in ATR mode for samples deposited with different r H . The buy AZD8931 quartz reference spectrum is also shown for comparison (dotted line). Figure 3 one can also see that the spectra of the samples deposited with excess silicon are much broader in comparison with the IR spectra of pure quartz. Moreover, the decrease of the r H used during deposition leads to a significant broadening of the IR spectra. This effect can be related to the lowering of the degree of matrix structural order. It should be emphasized here that we consider a short-range order since the matrix is non-crystalline.