Large scale computer simulations of strain distribution and electron effective masses in silicon ⟨100⟩ nanowires

A multiscale method is proposed to analyze the internal redistribution of tensile strain applied to silicon ⟨100⟩ nanowires and its effect on electron effective masses m∗. Nonperiodic, realistic models of unprecedented size containing up to 2.2×107 atoms (652×26×26 nm3) allow the identification of nonuniform redistribution patterns specific to the constraints applied to impose external strain. Depending on how the external strain is imposed, silicon nanowires can show m∗ behavior similar to strained bulk silicon, or, as a function of nanowire size, can display intrinsic strain large enough that external strain hardly reduces m∗ further. For nanowire cross section sizes smaller than 8×8 nm2 quantum confinement leads to an increase in m∗ which cannot be compensated for by tensile strain.