Evaluation of Leakage Current in 1-D Silicon Dangling-Bond Wire Due to Dopants
Résumé
Molecular devices will be contacted by systems with increasingly reduced dimensions. The device will need to be held somehow, possibly on a solid surface, and electronic currents will be addressed to the device via some kind of 1-D interconnect of atomic size. The fact that the device is posed on a surface brings in perturbations and eventually malfunctions of the device. Semiconducting surfaces have been deemed to be good candidates for this molecular technology because they have an electronic gap that prevents current losses from the device plus their surfaces are full of directional chemical bonds that make them ideal to hold a molecular device. However, semiconductors are generally doped, intentionally or unintentionally. Here, we summarized our findings on how destructive the presence of dopants is on the working parameters of a possible device. In fact, instead of a molecular device, we choose an ideal 1-D surface interconnect made out of Si dangling bonds in an otherwise passivated Si(100)-H surface. The current lost into a doped silicon substrate from a surface-supported nanowire is evaluated using transport calculations based on the density functional theory. We considered two concentration limits: either a single-dopant nearby the wire or a massively doped system. Both limits yield qualitatively similar results, stressing the strong perturbation that a single dopant can exert on an atomic-size wire. Our calculations permit us to conclude that n-doped Si will be less leaky than p-doped Si