## 3 Results
As shown in Figure 3, in order to evaluate the surface roughening effect, the authors felt that it was prudent to compare the surface topography before and after HF treatment (30 s) so as to demonstrate that the final etching conditions arised solely from the grafting of the alcohol to the silicon surface. All the surface morphologies of various doping and orientation were as displayed, from pristine, HF treated and alcohol reacted surfaces in Figure 3 and it was immediately obvious that all \(p\)-type surfaces exhibit a much rougher topography than compared to \(n\)-type. In fact, despite the crystal orientation, this result seemingly suggests that the roughening was more prominent with the \(p\)-type surfaces than the \(n\)-type in general although it must be stated that the starting roughness on (111) silicon was already much lower compared to the (100) crystal orientation. Cross-section profiling showed that \(p\)-type (111) experienced an increase in surface roughness upon alcohol functionalization, from an initial RMS value of 0.09 nm \(\pm\) 0.05 nm (pristine unmodified silicon) to a final RMS of 0.86 nm \(\pm\) 0.15. On the other hand, there was a near negligible change of surface roughness on the \(n\)-type silicon before functionalization (RMS: 0.06 nm \(\pm\) 0.03) and after the reaction (RMS: 0.11 nm \(\pm\) 0.05). On the other hand, the roughening effects were even more profound for both \(p\)- and \(n\)-type silicon (100) surfaces, with RMS registering at 2.58 nm \(\pm\) 0.03 for the \(p\)-type and 1.05 nm \(\pm\) 0.32 for the \(n\)-type respectively. When these data were corroborated with the XPS in Figure 2, it was clearly noticeable that the effects of grafting did not affect (111) the surface as much as (100), as both Figure 2a,b clearly exhibit the notable levels of Si2P\({}_{3/2}\) and Si2P\({}_{1/2}\) at 99-100 eV. Of the set of data obtained from XPS, \(p\)-type silicon (100) showed the lowest level of Si2P\({}_{3/2}\) and Si2P\({}_{1/2}\) at 99-100 eV and this suggested that much of the Si-Si linkage on the surface of the substrate was disrupted and our AFM seemed to confirm this finding. Since the observed chemical reaction to the surface was very similar for both crystal orientations and XPS had successfully indicated the formation of the Si-O-C linkage, surface roughening could only be conceived as an artefact arising from a collective influence of doping chemistry and crystal orientation. This was further confirmed by wettability studies as the water contact angle for the (111) \(p\)-type and the (111) \(n\)-type was registered at 87.2\({}^{\circ}\)\(\pm\) 4.6\({}^{\circ}\) and 70.8\({}^{\circ}\)\(\pm\) 0.8\({}^{\circ}\), further showing the changes in wettability induced from surface roughening. We found that the hydrophobicity was lower for the (100) surfaces (see Figure 4) and this may be attributed to the lower packing order of the adatom of silicon (100) on the surface of the silicon wafer compared to the silicon (111) surface. Firstly, it is important to state that the focus of this paper is to examine the mechanism behind the Si-Si backbond weakening mechanism rather than describing the entirety of the etching process. Hence, to describe the changes to the \(p\)-type silicon (111) surface roughness and the concurrent absence of roughening on \(n\)-type silicon, it is important to appreciate that atomically flat hydrogen-terminated (111) silicon surfaces are generally less likely to be etched or roughened due to the co-planar arrangement of atoms at the surface that renders it relatively stable. Thus, the weakening of the Si-Si backbond is deemed to be difficult due to the sterics on the surface [28]. For our case, in the first phase of the reaction, the alcohol grafting and the subsequent formation of the Si-O-C linkage on the surface would induce a polarization of the surface. This results in the oxygen species pulling the electron closer towards the silicon surface atoms due to its higher electronegativity.