The presence of a mechanochemical local oxide layer prevented KOH solution etching. Protuberance heights increased until the tensile stress reached 4.5 GPa and then decreased with load. At this peak height, the maximum shear stress attained was more than 8 GPa. This suggests that mechanochemical processing using a 100-nm-radius
diamond tip is load dependent mTOR inhibitor when the shear stress exceeds the strength of silicon, inducing a plastic deformation of several nanometers. Additional KOH solution Selleckchem Torin 2 etching was performed on the processed silicon to evaluate the chemical properties of the processed area. The topography and cross-sectional profiles of a silicon sample pre-processed with a 100-nm-radius diamond tip at loads of 10 and 40 μN were obtained click here by scanning at 1.5 μN over an area of 6 × 6 μm2 as shown in Figure 9. At 10-μN load, a 1.5-nm-high protuberance was mechanochemically generated by the sliding of the diamond tip. In contrast, at 40 μN, the height of the protuberance reached 3 nm as shown in Figure 2, while
plastic deformation produced a groove at the end of the scanning area. The natural oxide layer was removed under the 1.5-μN load at 6 × 6 μm2 scanning area and 256 scanning cycles. At nearly 10-μN load, the 100-nm-radius tip produced protuberances of nearly 1.5 nm through silicon oxidation. However, the maximum shear stress increased beyond the yield criterion at nearly 40-μN load, resulting in silicon plastic deformation and a subsequent change in profile. In this condition, the height 3-mercaptopyruvate sulfurtransferase of the processed area was as much as 3 nm higher
than that of the area processed at 10-μN load, and surface damages such as dislocations were increased in number. Figure 9 Profile of the Si (100) surface processed by diamond tip sliding. (a) Surface profile. (b) Section profile (10 and 40 μN). To understand the dependence of the relative etching depth on etching time, the pre-processed and unprocessed areas were etched with KOH solution for 10, 15, 20, 25, 30, and 40 min. No significant change in the topography of the surface was observed even after 10- and 15-min etching. The heights of the protuberances were slightly increased to 2.3 and 3.4 nm at 10 and 40 μN, respectively. Figure 10 shows the topography and cross-sectional profiles of the processed surface after 20-min KOH etching. The square groove of the 6 × 6 μm2 area processed at 1.5-μN load was slightly etched. Although the depth of this groove was 1 nm or less, the roughness of the processed surface was slightly increased. Meanwhile, the area pre-processed at 10 and 40 μN was not etched.Figure 11 shows the etching profile of pre-processed areas after 25 min. The etching depth of the area pre-processed at 1.5-μN load was significantly increased to more than 110 nm. This rapid increase in etching depth was due to the removal of the natural oxide layer by the low-load pre-processing.