CaO reacts quickly with water to form Ca(OH)2. Normally one would not consider making a thin film of this as it would quickly hydrolyze in the ambient. You'd need to keep the material in a dry inert atmosphere. One could consider a process where the CaO would be covered with a barrier layer, say of SiO2. Only route to a thin film would be some form of deposition process such as CVD. Your Ca(NO3)2 will just form crystals on evaporation prior to firing.

CaO, TiO2 easily react with water to form Ca(OH)2. You had need to keep the material in dry inert atmosphere. Spry pyrolysis process CaO thin film is prepared easily.

Attached paper may be help to you.

Nurul Islam TiO2 does not react with water and this material is not mentioned in the question.

Yes sir. Basically i am implies that oxide family member.

Thanks you sir.

@Alan F Rawle Thanks for your detailed answer. Can i make CaO thin films by CVD by not covering with barrier layer? or i have to cover them with barrier layer.

Munir Ullah Khan If you don't cover them with a barrier layer than they won't be CaO after a few minutes in air... I assume that you are not a chemist?

@Alan F Rawle Thanks Sir for your satisfactory explanations. I am chemist and pharmacist. I desperately need to prepare basic thin films on silicon Wafer. Actually thin films synthesis is new research area for me. Support material should be only basic materials. We need a basic support ie CaO so that basic pyridine selectively adsorbs on acidic WOx nanorods and not on basic CaO support. We want to make acid base titration on the solid surface.

Dear Munir Ullah Khan

maybe a simple CaO precipitation method[1] on[2] a bilayer substrate of W-O (surface oxidized film) // W(metal) configuration is near to your project's target.

1. CaO–ZrO2 Solid Solution: A Highly Stable Catalyst for the Synthesis of Dimethyl Carbonate from Propylene Carbonate and Methanol

https://www.researchgate.net/publication/225813086_CaO-ZrO2_Solid_Solution_A_Highly_Stable_Catalyst_for_the_Synthesis_of_Dimethyl_Carbonate_from_Propylene_Carbonate_and_Methanol

2. in an Ar-filled GB.

Dear Munir Ullah Khan in addition to the above comments, if you have access to PLD setup there, I would encourage you to make a target (around 2.5 inch dia) by solid state synthesis of your desired final composition. This will then lead to excellent structural control with epitaxial well ordered films with higher performance. I believe your research is for some application of this material!

Good luck