Giant piezoresistance and its origin in Si(111) nanowires: First-principles calculations

Through systematic first-principles calculations, we found extraordinarily high piezoresistance coefficients in a pristine Si(111) nanowire. This stems from interplay between the presence of two surface states with different localizations and unusual surface relaxation. Lattice compression along the axis causes switch between light and heavy surface states and, subsequently, alters the effective masses of carriers. Fascinatingly, model calculations produced main features of experimental data [R. R. He and P. D. Yang, Nat. Nanotechnol. 1, 42 (2006)] despite much difference in wire sizes and surface conditions.