Room-Temperature Plasticity of a Nanosized GaN Crystal

Funding Information: We gratefully acknowledge Prof. Shuji Nakamura (University of California, Santa Barbara) for his invaluable criticism, stimulating comments. and important suggestions. Equally appreciated are the observations and remarks by Prof. William D. Nix (Stanford University). R.N. acknowledges invaluable discussions with Prof. Toshihiro Shimada (Hokkaido University) and his role in ascertaining the quality of the nanopillars used in our experiments. R.N. also expresses appreciation to Prof Koichi Niihara and Prof. Hisayuki Suematsu (Nagaoka University of Technology) as well as to Mr. Michael Berg (Bruker Nano Surfaces, Los Angeles) for their long-standing support and many an eye-opener. MF is thankful to Mr. Hideki Hata and Tomohiko Ueda (Panasonic Corp.) for rewarding discussions concerning TEM observations. Finally, R.N. and D.C. acknowledge the support from Osaka University and Nagaoka University of Technology during their time as guest-scholars. This research was sponsored by Panasonic Corp.,Japan, as part of cooperation with Japanese universities. Publisher Copyright: ©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 nanoobjects 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.Peer reviewe