HgTe1−xSex solid solutions have been prepared, with x varying from 0 to 1. The samples are n type near x=1 and p type near x=0, but, due to the high electron-to-hole mobility ratio, electronic conudction is dominant in the range 100–400°K in all samples. The concentration of free electrons lies between 5·1016 and 3·1018 cm−3. Measurements of the Hall mobility μH and magnetothermoelectric effect ΔQ show that, for Se-rich samples, lattice scattering is dominant in the range 77–400°K and that, near room temperature, μH ∝ T−2. For Te-rich samples, lattice scattering is dominant in the range 200–400°K and, near room temperature, μH ∝ T−1. Effective masses have been calculated and it is seen that the conduction band is not parabolic. The detailed band structure and the exact value of the mobility seem to depend little upon structural factors. For x=0.5 and x=0.9, the electron mobility can reach 12 000 cm2 v−1 sec−1 at 293°K and 30 000 cm2 v−1 sec−1 at 77°K.
A novel approach is reported for minimizing light conversion efficiency losses on n-type silicon due to surface recombination and reflection of the incident light, using photoelectrochemical etching. Efficiency and stability of aqueous (concentrated HI) photoelectrochemical cells can be improved by this process.
ABSTRACTThe relation between structure and preparation conditions of polyaniline (PANI) was determined using scanning tunneling microscopy in air. The morphology of a PANI film grown with fast cyclic potential scans (20 V/s) was uniform and dense, whereas a film grown with slow scans (50 mV/s) over the same potential range with the same number of coulombs passed was amorphous and rough. The possibility of control of PANI morphology based on the electropolymerization kinetics is discussed.
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