Scanning Microscopy


Structural and optical properties of porous Si are reviewed with the main emphasis on the radiative recombination mechanisms. Behaviors of the visible photoluminescence and another intense luminescence process (the infrared luminescence) are discussed based on the available data provided by photoluminescence and related techniques. It is demonstrated that a further insight into the interrelation of these luminescence processes can be obtained by the optically-detected magnetic resonance method, in which non-radiative point defects (surface dangling bonds) are used as a local structural probe for the radiative states.

As for the model for the visible light emission, the implication of the quantum confinement model (quantum wire or dot model) is discussed together with its limitations. We also discuss the possible role of localized states as the source of this visible photoluminescence. Such states may be present near the surface regions of small Si clusters to provide the radiative states. On the other hand, the infrared luminescence is speculated to be the carrier recombination in the perturbed crystalline Si regions, having rather large dimensions compared to those of the Si-microcrystallies.

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