The mechanisms of material removal and atomic-scale damage in InP during elliptical vibration-assisted nanoscratching integrated with laser processing

Abstract

Indium phosphide (InP) crystals exhibit significant potential for applications in photoelectric detectors, artificial intelligence and 5 G communication. The quality of the surface and subsurface layers critically influences their performance as substrates. Therefore, gaining an in-depth understanding of the material removal mechanisms and atomic-scale damage behavior during InP machining is essential to enable its broader implementation. This study proposes an atomic force microscopy (AFM) tip-based elliptical vibration-assisted nanoscratching technique combined with laser processing (EVANL). The mechanical properties of InP following laser processing are evaluated through AFM indentation. Transmission electron microscopy (TEM) observations and molecular dynamics (MD) simulations demonstrate that a thin amorphous layer is formed on the sample surface, which accounts for the reduced hardness observed in the laser-processed material. The material removal mechanisms of InP in tip-based elliptical vibration-assisted nanoscratching (EVAN) and EVANL are investigated. Compared with conventional AFM scratching, a relatively high strain rate of up to 5.7 × 10⁶ s⁻¹ is achieved in both EVAN and EVANL, leading to the embrittlement of the pristine crystalline InP sample. However, due to the formation of an amorphous phase, the material removal behavior of the laser-processed InP sample becomes insensitive to strain rate. The effects of driving frequency and voltage on the machined depth are investigated. The depth of the nanogroove fabricated by EVANL is consistently greater than that achieved by EVAN, which can be attributed to the reduced hardness of the material. TEM observations demonstrate that EVANL results in shallower subsurface damage compared to EVAN. The effects of machining trajectories, including conventional array profiling (CAP) and Lissajous trajectory profiling (LTP), on the resulting nanostructures are investigated. Ultimately, a flatter nano-surface with a surface roughness (Ra) of 2.06 nm is achieved through EVANL using LTP. This research presents a novel approach for machining InP samples with a high-quality surface and shallow subsurface damage, along with mechanistic insights into conventional grinding processes.