When scratching a diamond tip under the same loading condition, silicon crystal plane with lower elastic modulus will induce larger Cilengitide cost Contact area and more pressed volume, which provides more probability for deformation of silicon matrix below the scratching tip. As shown in Table 1, since the elastic modulus of Si(100) surface is 23%/31% lower than that of Si(110)/Si(111)

surface, the pressed volume on Si(100) is 36%/53% larger than that on Si(110)/Si(111) surface at F n = 50 μN. Table 1 Comparison of the contact of a diamond tip on various silicon crystal planes Sample Si(100) Si(110) Si(111) Contact area A (nm2) 8.86 × 103 7.61 × 103 7.17 × 103 Pressed volume V (nm3) 2.49 × 104 1.83 × 104 1.63 × 104 The tip radius (R) is 500 MDV3100 in vivo nm, and the normal load (F n) is 50 μN. Such results can be further confirmed by the indentation tests with a spheric diamond tip (R = 1 μm). As shown in Figure 5, since the measured loading/unloading curves were overlapped at the maximum indentation depth of 20 nm, the deformation during the indentation process was purely elastic. At the same indentation force,

the indentation depth and the pressed volume on Si(100) surface were the largest, while those on Si(111) surface were the smallest. The larger pressed volume provides more probability for deformation of silicon matrix below the scratching tip. Therefore, the highest/lowest hillock was produced on Si(100)/Si(111) in the present study. Figure 5 Comparison of the GSK1120212 indentation force-depth FER curves on Si(100), Si(110), and Si(111) surfaces. Indentation force-depth curves during loading process measured by a diamond tip with R = 1 μm. The inset showed that the indentation force-depth curves on Si(100) surface during loading and unloading process overlapped with each other, suggesting that the deformation during indentation process was purely elastic. The effect of pressed volume on the hillock height can be further verified by the fabrication

tests with different diamond tips. As shown in Figure 6, friction-induced hillocks were produced on Si(100) surface with two different diamond tips (R=500 and 250 nm) under the same contact pressure (8.5 GPa). The hillock produced by the blunt tip was 4.9 nm in height, while the hillock produced by the sharp tip was only 3.3 nm in height. When the pressed volume increased by 692%, the height of the produced hillock increased by 48%. Clearly, the pressed volume had a strong effect on the hillock formation. The larger pressed volume corresponds to the formation of more amorphous silicon and higher hillock. Figure 6 Comparison of the hillocks produced with different diamond tips under the same contact pressure. (a) R = 500 nm; (b) R = 250 nm. The number of scratch cycles was 100.