Size Dependence of Nanoscale Wear of Silicon Carbide

Abstract

Nanoscale, single-asperity wear of single-crystal silicon carbide (sc-SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native oxide layers. We discovered a transition in the relative wear resistance of the SiC samples compared to that of Si as a function of contact size. With larger nanoindenter tips (tip radius ≈ 370 nm), the wear resistances of both sc-SiC and nc-SiC are higher than that of Si. This result is expected from the Archard's equation because SiC is harder than Si. However, with the smaller AFM tips (tip radius ≈ 20 nm), the wear resistances of sc-SiC and nc-SiC are lower than that of Si, despite the fact that the contact pressures are comparable to those applied with the nanoindenter tips, and the plastic zones are well-developed in both sets of wear experiments. We attribute the decrease in the relative wear resistance of SiC compared to that of Si to a transition from a wear regime dominated by the materials' resistance to plastic deformation (i.e., hardness) to a regime dominated by the materials' resistance to interfacial shear. This conclusion is supported by our AFM studies of wearless friction, which reveal that the interfacial shear strength of SiC is higher than that of Si. The contributions of surface roughness and surface chemistry to differences in interfacial shear strength are also discussed.

Pushing the Limits of Piezoresistive Effect by Optomechanical Coupling in 3C-SiC/Si Heterostructure

“…911 Among these materials, SiC emerged as a promising candidate courtesy of its high bandgap and excellent mechanical and chemical properties. 12,13 The gauge factors of the piezoresistive eect in SiC have been reported to be approximately 30, which is approximately four times smaller than Si. 10,14 To enhance the sensitivity, scaling down the piezoresistor to a nanometer-scale has drawn signicant attention recently.…”

Advances in Atomic-Scale Frictions with Stick-Slip and Super-Lubricity

“…Compared to Si, SiC with high hardness exhibits low friction and less wear under low normal loads [47]. But the plastic deformation and wear are supposed to be induced on SiC surface when the normal load increases to the load regime applied in MEMS devices (> 100 nN) [48].…”

Direct Atomic Simulations of Facet Formation and Equilibrium Shapes of SiC Nanoparticles

“…Silicon carbide is attractive due to its high mechanical strength. Accordingly, mechanisms and transitions during mechanical loading of silicon carbide have been studied in experiments , and molecular simulations. − On the nanoscale, the shape of crystals directly affects their propeties. − Despite advances in nanoscale imaging − and modeling, the detailed atomic mechanisms of nanocrystal formation has not been directly observed in experiments or simulation. ,, The transformation of a crystalline particle from any initial shape to its equilibrium crystal shape involves a series of complex processes. − The final equilibrium shape has facets resulting from the minimization of surface free energy for a given volume . The equilibrium shape of a nanocrystal is uniquely determined by the Wulff construction according to the surface free energy associated with all crystal directions, resulting in certain planes being preferred.…”

“…5 Silicon carbide is attractive due to its high mechanical strength. Accordingly, mechanisms and transitions during mechanical loading of silicon carbide have been studied in experiments 6,7 and molecular simulations. 8−11 On the nanoscale, the shape of crystals directly affects their propeties.…”