Metal/carbon nanotube Schottky contacts are studied using particle Monte Carlo simulation. The developed model is based on the WKB approximation and on the Landauer formula. Results are in fairly good agreement with experimental data.
Photo acoustic effect, structural acoustic of membranes, resonance and damping of mechanical waves, vibration measurement, semiconductor devices) ABSTRACT This experimental work presents reproducible measurement conditions to allow amplification of the mechanical vibration generated by photo-thermo-acoustics (PTA) effect using the resonance of circular Silicon membranes clamped by nitrile o-rings on a diameter of 30mm (D i). We use wafers with various thickness (h) between 250 and 1000µm and with carrier lifetime between 3 and 30µs. Under the condition to have a resolution of few picometers for the measurement, it is possible to characterize the resonance mechanism obtained without contact by conventional laser vibrometry using a modulated laser diode of only a few milliwatts of power. Compared to perfect clamped membranes, the first Eigen frequency presents a downward shift of some hundreds Hertz due to the circular clamping by o-ring as predicted by our simplified model. The resonance frequency depends linearly on the thickness as long as D i /h>80. The quality factor (Q) does not exceed ten in agreement with our model for spring loaded membrane in air. The low value of quality factor and its variation according to thickness follow our predictions. Moreover, Q is independent of carrier lifetime whereas first resonance amplitude increases with it but less than prediction for bulks.
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