I have deposited ZnO films using spray pyrolysis method, optical transmittance was increased with increase in substrate temperature..so may i know what happens for optical energy band gap? Whether it is increasing or decreasing?
Dear friend,
with low substrate temperature, there will be less process of oxidation... so glass substrate may not be more transparent since the coating is not 100% in oxidized form. As you increase the temperature Oxidation increases and material becomes more crystalline. As you know like TiO2 ...ZnO is also transparent semiconducting oxide. Since Oxidation enhances due to higher temperature with each spray there will be the formation of smaller nuclei and hence particles of ZnO whose optical bandgap is higher. HEnce Eg increases. I hope this helps you. good luck. :)
Dear Sindhu
The answer of Mr. Umesh is very right, also you can knew the optical band gap increased or decreased by observation the transmittance if it increase this mean energy gap increase (more incident photons pass through this layer), also when transmittance decrease this mean energy gap decrease. With best regards
pls consider the particle size of ZnO nanoparticles. when the substrate temperature in increases the particle size should decrease leads to higher no.of.grain boundaries in a particular area. so when electrons can be excited by optically or electrically it will cross more no of grain boundaries. this is the reason why electrons face higher resistance due larger band gap..
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