Abstract
Mechanochemical reactions at the gallium nitride-alumina (GaN–Al2O3) interface at nanoscale offer a significant beneficial reference for the high-efficiency and low-destruction ultra-precision machining on GaN surface. Here, the mechanochemical reactions on oxide-free and oxidized GaN surfaces rubbed by the Al2O3 nanoasperity as a function of the ambient humidity were studied. Experimental results reveal that oxidized GaN exhibits a higher mechanochemical removal rate than that of oxide-free GaN over the relative humidity range of 3–80%. The mechanical activation in the mechanochemical reactions at the GaN–Al2O3 interface is well-described by the mechanically-assisted Arrhenius-type kinetics model. The analysis indicates that less external mechanical activation energy is required to initiate the mechanochemical atomic attrition on the oxidized GaN surface compared with the oxide-free GaN surface. These results may not only gain a deep understanding of the mechanochemical removal mechanism of GaN but also provide the basic knowledge for the optimization of the oxidation-assisted ultra-precision machining.
Highlights
Experimental results show that the mechanochemical reactions at the gallium nitride (GaN)–Al2O3 interface can be facilitated by the topmost oxidized surface structure
Slight wear with a depth of ∼0.2 nm occurred on the GaN-hydrofluoric acid (HF) surface in dry N2 condition and the removal volume was dramatically increased from nm3 at 3% relative humidity (RH) to nm3 at 80% RH
Under a purely elastic contact region, evident material removal can occur on GaN-HF and GaN-AR surfaces with the assistance of the interfacial mechanochemical reactions
Summary
Because of the excellent performances in the case of wide direct bandgap, high heat capacity and thermal conductivity, low dielectric constant, and high breakdown voltage, gallium nitride (GaN) materials have aroused great interests in the wide application prospects of optoelectronics and microelectronic, such as high-brightness/efficiency light-emitting diodes, highfrequency/power/temperature transistors, short-wavelength emitters/detectors, etc. (Tsao et al, 2014; Pust et al, 2015; Glavin et al, 2017; Lev et al, 2018; Meneghesso et al, 2018; Sarangadharan et al, 2018). To reveal the mechanochemical removal mechanism during the CMP process of GaN surface, nanowear. Previous studies have indicated that with the assistance of the chemically active counter-surface and ambient medium, the mechanochemical material removal can occur under the pure elastic contact situation (the contact pressure is far below the plastic yield of the substrate). Such material removal is dominated by the interfacial mechanochemical reaction involving the formation of interfacial bonding bridges and the rupture of chemical bonds on the substrate (Chen et al, 2014; Xiao et al, 2017a). Limited literature has been reported on the influence of surface oxidization on mechanochemical removal of GaN surface
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