In case of semiconductor oxide film deposited at 350 degree Celsius i found small bubbles/black holes/ black particles on the film. I am struggling with that bubbles to make a very uniform film. i am using a stabiliser in 2ME solvent to make ZnO film , in this case no bubbles. But if i want to make AlOx or ZrOx i find that problem. Can you suggest?
I tried by reducing the flow rate but i need a thick layer. I repeat the process 6 or times. As no. of layer increases the density of bubbles/black particle increasing.
Hi Jewel,
Could you be a bit more specific in terms of of the precursors used? Different precursors would have a different thermal decomposition pathway with rapid evolution of gases and thereby the formation of a bubble/foam like microstructure. The black matter on the surface could likely be trapped hydrocarbon species. In this case, recucing the precursor concentration and increasing the number of coats could help.
Hope, following article may boost up your knowledge;
https://repository.kaust.edu.sa/bitstream/handle/10754/628443/1.5036809.pdf?sequence=1&isAllowed=y
Metal chlorides have a more or less sharp, single step thermal decomposition at comparatively higher temperatures which could lead to a sudden evolution of volatile byproducts, thereby increasing film porosity. On the other hand, metal nitrates have a more gradual decomposition and at much lower temeperatures. A switch to metal nitrate precursors would certainly reduce the formation of residual carbon species and would provide a much smoother film formation. Another potential reason for the bubbled texture could be the use of ammonium acetate. Is there a specific reason for its use as a stabilizer ? instead of the well established monoethanol amine (MEA). Additionally, evaporation of the solvent (2-ME) at intermediate temperatures and finally annealing them at high temperatures would also improve film density in comparison with direct pyrolysis at 350 degrees.
Majibul babu i know this paper. But i am trying to make good GI by Spray pyrolysis. In spray main problem is bubbles otherwise we can get very good characteristics.
I used either zirconium butoxide or zirconium 2-ethylhexaonate in 2ME solvent without a stabilizer to make precursor. The resultant films made by spin-coating showed a good uniformity and dense structure without bubbles. The annealing temperature might be in the range between 300-600 degree Celcius with an intermediate pyrolysis at 250 degree C. Hope it helps!
By maintaining various deposition parameters viz. molar concentration of precursor solutions (normally o.1 MC), distance bet'n nozzle to substrate, temperature, deposition time, homogeneous clear solution, spray rate, carrier air flow rate, etc better film is possible. In the liquid channel there will be no air. Hot plate temperature to be adjusted depending on the mother solutions of metal ions. Post annealing may also give better result. After film deposition sample can be kept on the hot plate until temperature cool down. There are four forces also responsible like gravitational, electrical, stokes forces as well Thermophoretic force pushes the droplets away from a hot surface.
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