I have realized the growth of ZnSe nanowires (diameter : 50-80 nm) through a CVD route, but their electrical conductivity is very weak, I want to know how to increase their electrical conductivity?
1. By increasing conductivity of a wire itself.
2. By decreasing contact resistance.
Strain the device. Look as to how mobility is a function of stress-strain since rho=mobility*carrier number*charge. Alternatively you can heat the device to generate carriers.
Looking at the structure of the material, anneals to improve the grain structure can also help.
First: You should check, if your measurement setup is okay. One serious problem is the contact resistance. Therefore at least you should measure in 4 point geometry. But this does not make shure, that your measurment is right. Check the results by changing the position of the sample be 180 degree. To avoid contact resistance caused by diffusion of contact material into the sample you should use diffusion barriers.
Second: Compare your results to ZnSe-bulk material. To see the effect of reducing the diameter of bulk-wire you should have some samples with different diameters, for example: 1 µm, 100 nm, 10 nm, 5 nm, 2 nm. The mean free path of the electrons or holes will go down dramatically, but if theory is right, then you should see an increase in some transport parameters when sample is affected by the quantum confinement.
I did a lot of measurements on QW- and MQW-structures. We could see an increase of the Seebeck-coefficient, but the mobility was not negative affected by quantum confinement. The mobility decreased dramatically for Film thicknesses lower 4 nm. Therefore you should calculate the mean free path of bulk, Then check if in that area of diameter of your samples the mobility will go down.
An increase of the mobility by doping or heat treatment you will have as long there is no quantum confinement (qc). From my experience I can say, that the drop down of mobility is much more than the increase of doping or heat treatment for samples with qc.
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