Tunable quantum confinement in ultrathin, optically active semiconductor nanowires via reverse-reaction growth.

A unique growth scheme is demonstrated to realize ultrathin GaAs nanowires on Si with sizes down to the sub-10 nm regime. While this scheme preserves the bulk-like crystal properties, correlated optical experiments reveal huge blueshifted photo-luminescence (up to ≈100 meV) with decreasing nanowire cross-section, demonstrating very strong quantum confinement effects.