Room-Temperature Plasticity of a Nanosized GaN Crystal
M Fujikane and S Nagao and D Chrobak and T Yokogawa and R Nowak, NANO LETTERS, 21, 6425-6431 (2021).
GaN wurtzite crystal is commonly regarded as eminently brittle. However, our research demonstrates that nanodeconfined GaN compressed along the M direction begins to exhibit room-temperature plasticity, yielding a dislocation-free structure despite the occurrence of considerable, irreversible deformation. Our interest in M-oriented, strained GaN nano- objects was sparked by the results of first-principles bandgap calculations, whereas subsequent nanomechanical tests and ultrahigh- voltage (1250 kV) transmission electron microscopy observations confirmed the authenticity of the phenomenon. Moreover, identical experiments along the C direction produced only a quasi-brittle response. Precisely how this happens is demonstrated by molecular dynamics simulations of the deformation of the C- and M-oriented GaN frustum, which mirror our nanopillar crystals.
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