The contact pressure and contact diameter were evaluated using the Hertzian equation. At 1 and 6 μN, the contact pressures were 6.9 and 12.5 GPa, respectively.The selleck chemicals scanning density selleck products decreased with the scanning cycle number. The total contact sliding width can be evaluated from the product of the contact diameter

and scan number. Then, to evaluate the overlap ratio, the total contact width is divided by the scanning width. For example, at 6-μN load, the Hertzian contact diameter is nearly 30.3 nm; therefore, the total contact width for 128 scans was 30.3 × 128 nm and the overlap ratio was nearly 0.97, as shown in Figure  6b. In this case, the total contact width was smaller than the scanning width. The natural oxide layer formed on the Si surface was removed at low scan number conditions; overlap of the sliding contact area appeared to produce an etching-resistant layer. Figure 3 Etching profile for 128-scan pre-processing. (a) Surface profile. (b) Section profile (1 and 2 μN). (c) Section profile (4 and 6 μN). Figure 4 Etching profile for 256-scan pre-processing. (a) Surface profile. (b) Section profile (1 and 2 μN). (c) Section profile (4 and 6 μN). Figure 5 Etching profile for 512-scan pre-processing. (a) Surface Poziotinib mw profile. (b) Section profile (1 and 2 μN). (c) Section profile (4 and 6 μN). Figure 6 Dependence of etching depth

(a) and overlap ratio (b) on load and scanning number of pre-mechanical processing. Owing to the removal of the natural oxide layer, 512 scans at 1-μN load also increased the etching rate. Processing at higher loads of 4 and 6 μN increased the amount of mechanochemical oxidation owing to the high density of the scanning and thus decreased the etching depth. At 512 scans, the total contact width was larger than the scanning width, so the contact area overlapped. Pre-processing at low load and scanning density efficiently removed the natural oxide layer by mechanical action while also mechanochemically generating a thin oxide layer because of the sliding overlap.To clarify the etch properties of pre-processed areas at higher

load, the etching profiles obtained at 8-, 10-, 15-, and 20-μN load after 256 scans were evaluated as shown in Figure  7. In these cases, etching grooves could not be detected in any of the processed areas. The Bortezomib order heights of all of the processed areas were slightly greater than those of the unprocessed areas. Thus, the effect of any increases in etching rate resulting from the removal of the natural oxide layer could not be obtained. This is conceivable because mechanochemical oxidization increases at higher load, resulting in improved resistance towards etching with KOH solution.To compare the resistances of the natural oxide layer and the mechanochemically generated oxide layer to etching, we extended the etching time by 5 min. Figure  8 shows the etching profiles of pre-processed areas at 2-, 4-, 8-, and 15-μN loads.