Preparation of nanocrystalline silicon quantum dot structure by a digital plasma process

Nanocrystalline silicon (nc-Si) is an ultrafine particle of silicon with dimensions less than 10 nm. Particles of this size exhibit quantum effects. We developed a novel method called digital plasma processing for the control of particle size, position, and surface electronic states of nc-Si. Preparation conditions for nc-Si were studied by using both solid-phase and vapor-phase nucleation methods. The ultrafine structure of nc-Si was investigated using high-resolution transmission electron microscopy. An atomic force microscope was used to image the surface morphology, to manipulate the position, and to measure the electrical properties of nc-Si. Quantum effect properties in nc-Si were investigated by using photoluminescence and Coulomb blockade characteristics. Monodispersed nc-Si with size variation of 8 ± 1 nm were obtained by a pulsed plasma process. Coulomb staircase was observed in current-voltage characteristics from nc-Si at room temperature. These results suggest that nc-Si is a promising candidate for the application of future ultra large scale integrated devices.