Coherent states in a coupled quantum dot nanocrystalline silicon transistor

Abstract

We investigate the coherent coupling of electronic states in a nanocrystalline silicon quantum dot transistor. The device consists of a nanometer-scale point-contact containing only a few silicon grains. The grains form quantum dots, tunnel-coupled across thin silicon sub-oxide grain boundaries. At 4.2K, we observe a pattern of single-electron conductance peaks versus two gate voltages, caused by electrostatic coupling between the quantum dots. Additional peaks are observed when the energy levels from two adjacent quantum dots are resonant, which may be associated with “quasi-molecular” states formed by coherent coupling of the levels. The tunnel splitting obtained from the peak separation is ∼0.4meV, which is from a few times to an order-of-magnitude larger than reported previously in GaAs∕AlGaAs quantum dots.