2 15. Tin oxide (SnO ) is a w ide-bandgap, n-type semiconductor w ith a high concentration of 2 electrons. The properties of a spray-deposited SnO film are as follow s: G Bandgap E = 3.5 eV. Electron concentration n = 10 cm . 20-3 n Electron mobility : = 50 cm /V-sec. 2 e Electron affinity O = 4.8 eV. 2 (a) Sketch and label the energy band diagram of SnO , clearly identifying the relative locations of the various energy levels. F (b) Sketch and label the energy band diagram of gold (Au) w hich has a Fermi energy E m = 5.5 eV, an electron concentration n = 5.9 x 10 cm and w ork function N = 22-3 4.8 eV. 2 n (c) Calculate the conductivity of SnO and compare it w ith that of Au. Assume : = 50 cm /V-sec for Au also. 2 2 (d) The SnO film may be used as an optical filter. Will it be a low -pass (passes low -frequency, cuts off high frequency) or a high-pass filter? 2 (e) Suggest a few uses for SnO , a ‘ transparent conductor.’ 16.
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