Narrow Luminescence Linewidth of a Silicon Quantum Dot

Single-dot luminescence spectroscopy was used to study the emission linewidth of individual silicon nanocrystals from low temperatures up to room temperature. The results show a continuous line narrowing towards lower temperatures with a linewidth as sharp as 2 meV at 35 K. This value, clearly below the thermal broadening at this temperature, proves the atomiclike emission from silicon quantum dots subject to quantum confinement. The low temperature measurements further reveal a $\ensuremath{\sim}6\text{ }\text{ }\mathrm{m}\mathrm{e}\mathrm{V}$ replica, whose origin is discussed. In addition, an $\ensuremath{\sim}60\text{ }\text{ }\mathrm{m}\mathrm{e}\mathrm{V}$ TO-phonon replica was detected, which is only present in a fraction of the dots.