I deposited CdSe thin film using PVD technique and I measured the energy gap for the as-deposited thin films and after annealing for different temperature but constant time of annealing.The annealed film became almost transparent after annealing with high temp.
I just wondered, does the energy gap decrease, increase or is not affected by annealing? The transmission increased as the film became more transparent.
Thank you
Yes, energy band gap changes after annealing films. Lots of research work available for annealing effect on optical band-gap and you can easily access those literature. About Transparency, I suspect that your film damaged (due to high temperature). While annealing you should be very careful as its very easy to damage at high temperature, Normally around and above temperature 80-100C thin films starts damaging.
I suggest you to repeat experiment and examine carefully to make sure that it didnt get damaged.
Energy band gap has been increased by annealing because the semiconducting samples become more crystalline. Transparent as deposited sample will be more transparent after annealing if the band gap of as deposited samples near or little low than the energy of visible light.
If you can see the following article It was observed that the energy gap decreases
with the increase in the film thickness and increases with the increase in the annealing
temperature.
There are 2 types of semiconductors: the first one increases the Bg with annealing but the 2nd one - decreases in result of d8ifferent physical phenomena.
You should check for your material
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