Surface roughness effects on seebeck coefficient in silicon ultra thin films

Surface roughness effects play a crucial role in determining the performance of a device with dimensionality in the sub-50nm scale. In this work we theoretically investigate surface roughness effects on Seebeck coefficient of ultrathin silicon film using non equilibrium Green´s function technique. To systematically study surface roughness effects, thickness of the film is varied periodically with square wave profile characterized by two parameters: amplitude(A₀) and wavelength(λ). The results show that Seebeck coefficient increases with increasing roughness amplitude and frequency(1/λ). It is found that current which flows through the device, due to temperature gradient, is reduced due to surface roughness. It is interesting to note that, though the current decreases, the voltage required to nullify this current increases. Due to this increase in voltage Seebeck coefficient increases.