Abstract
Mechanical activation in mechanical removal of GaN using diamond tip and mechanochemical removal using Al2O3 tip are described by the Archard equation and mechanically assisted Arrhenius-type kinetic model, respectively. Evident material-removal under elastic contact occurs with the assistance of interfacial mechanochemical reactions. By analyzing the mechanochemical reactions with Arrhenius-type kinetic model and Hertzian contact mechanics, the critical activation volume and activation barrier are determined semiquantitatively. The mechanical activation originating from the chemically active counter-surface facilitates the mechanochemical atomic attrition by altering the energy barrier of the reaction kinetics. This work can provide deep insights into the mechanochemical-removal mechanism of GaN.
Highlights
Gallium nitride (GaN) has superior properties, a wide direct bandgap, low dielectric constant, high breakdown electric field, excellent chemical stability, and high thermal conductivity
To elim inate the influence of the oxide layer in the material removal behavior, the GaN sample was treated with 3 wt.% diluted hydrofluoric acid (HF) solution for 3 min to remove the oxide layer before nanowear tests
The critical contact pressure for the material-removal pro cess may be related to the activation energy of the chemical reactions that can be triggered by the mechanical action between GaN substrate and Al2O3 counter-surface
Summary
Gallium nitride (GaN) has superior properties, a wide direct bandgap, low dielectric constant, high breakdown electric field, excellent chemical stability, and high thermal conductivity. Due to the lack of the scientific understanding of the nanoscale GaN materials’ removal mechanism dominated by the mechanochemical interactions across the tribological interface, the further improvement in the accuracy and efficiency of the surface planarization is severely restricted. Many studies have indicated that the macro/ microscopic removal behaviors dominated by mechanochemical in teractions are strongly affected by the loading parameters (e.g., load/pressure, velocity/reaction time, and sliding direction), environ mental conditions (e.g., humidity, temperature), and surface properties (e.g., bonding energy, chemical activity, particle size, roughness, and mechanical properties) [11,12,13,14,15,16,17,18,19]. To fundamental comprehend the physico chemical processes in the CMP of GaN surface, a well-designed approach in a single-asperity sliding contact with the precisely controlled contact pressure/area, velocity, reactant concentration, and reaction time, should be applied
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