Modeling and the main stages of spin coating process: A review

Spin coating is a technique employed for the deposition of uniform thin films of organic materials in the range of micrometer to nanometer on flat substrates. Typically, a small amount of coating material generally as a liquid is dropped over the substrate center, which is either static or spinning at low speed. The substrate is then rotated at the desired speed and the coating material has been spread by centrifugal force. A device that is used for spin coating is termed a spin coater or just a spinner. The substrate continued to spin and the fluid spins off the boundaries of the substrate until the film is reached the required thickness. The thickness and the characteristics of coated layer (film) are depending on the number of rotations per minute (rpm) and the time of rotation. Therefore, a mathematical model is obtained to clarify the prevalent method controlling thin film fabrication. Viscosity and the concentration of (solution) spin coating material are also affecting the thickness of the substrate. This article reviews spin coating techniques including stages in the coating process such as deposition, spin-up, stable fluid outflow (spin-off), and evaporation. Additionally, the main affecting factors on the film thickness in the coating process are reviewed.

Enhanced Heat-Electric Conversion via Photonic-Assisted Radiative Cooling

In this paper, an inorganic polymer composite film is proposed as an effective radiative cooling device. The inherent absorption is enhanced by choosing an appropriately sized SiO2 microsphere with a diameter of 6 μm. The overall absorption at the transparent window of the atmosphere is higher than 90%, as the concentration of SiO2–PMMA composite is 35 wt%. As a result, an effective radiative device is made by a spin coating process. Moreover, the device is stacked on the cold side of a thermoelectric generator chip. It is found that the temperature gradient can be increased via the effective radiative cooling process. An enhanced Seebeck effect is observed, and the corresponding output current can be enhanced 1.67-fold via the photonic-assisted radiative cooling.