There is the link to describe the spincoating theory. Please see the link below.

https://www.ossila.com/pages/spin-coating

In summary, the spincoating techniques are involved in several features.

1. Liquids (dilutes and solvents): concentrations, vescosity, solvent boiling points, adhension to a substrate;

2. The properties of substrates to be used for coating such as the treatment on the surface;

3. The spincoating speed and duration;

4. The chuck to hold a substrate from a spin-coater; The geometry of a chuck could affect the homogenous coating as well.

Hope it helps.

You could look into:

Britten et al. J. Appl. Phys. 71, 972 1992. Non-Newtonian flow effects during spin coating large-area optical coatings with colloidal suspensions

Meyerhofer, J. Appl. Phys. 49, 3993 (1971). Characteristics of resist films produced by spin coating.

The spin coating process is carried out in four steps. In the first step, the solvent solution applied or deposit to the substrate. Then, spin up the substrate around an axis perpendicular to the coating area. This step followed by a spin-off, and finally gelation by evaporation of the solvent solution.

The balance between radially outward centrifugal force and radially inward viscous force the obtained film tends to be uniform and thin.

There are several descriptions of the thickness of the prepared film by the spin coating process. Of these, dependable thickness on the materials and processing parameters such as, solvent solution evaporation and the angular velocity according to the relationship derived by :

- Selomulya R, Ski S, Pita K, et al., Luminescence properties of Zn2SiO4:Mn2+ thin-films by a sol–gel process [J]. Materials Science and Engineering: B. 2003, 100(2): 136-141.

- Lin C M, Tsai Y Z, Chen J S, The microstructure and cathodoluminescence characteristics of sputtered Zn2SiO4: Ti phosphor thin films [J]. Thin Solid Films. 2007, 515(20-21): 7994-7999.

- Mai M, Feldmann C, Two-color emission of Zn2SiO4: Mn from ionic liquid mediated synthesis [J]. Solid State Sciences. 2009, 11(2): 528-532.

- Zhang H, Buddhudu S, Kam C, et al., Luminescence of Eu3+ and Tb3+ doped Zn2SiO4 nanometer powder phosphors [J]. Materials chemistry and physics. 2001, 68(1): 31-35.

Spin coating is a method to apply a uniform film onto a solid surface by using centrifugal force and requires a liquid-vapor interface. In a typical procedure, a liquid is placed at the center of a circular surface and is rapidly rotated to produce uniform films of 1–10 μm in thickness.

These two papers may be helpful:

(1) Karpitschka, S.; Weber, C. M.; Riegler, H. Spin Casting of Dilute Solutions: Vertical Composition Profile During Hydrodynamic-Evaporative Film Thinning. Chem. Eng. Sci. 2015, 129, 243-248, DOI: 10.1016/j.ces.2015.01.028.

(2) Danglad-Flores, J.; Eickelmann, S.; Riegler, H. Deposition of Polymer Films by Spin Casting: A Quantitative Analysis. Chem. Eng. Sci. 2018, 179, 257-264, DOI: 10.1016/j.ces.2018.01.012.

Hi:

Hope these papers help you:

Structure and optical properties of nanocrystalline NiO thin film synthesized by sol–gel spin-coating method

High-performance, spin-coated zinc tin oxide thin-film transistors