Electrostatic Spray Deposition of Copper-Indium Thin Films

Abstract

Electrostatic spray deposition is an innovative coating technique that produces fine, uniform, self-dispersive (due to Coulombic repulsion), and highly wettable, atomized droplets. Copper-indium salts are dissolved in an alcohol-based solvent; this precursor is then electrostatically sprayed onto a moderately heated, molybdenum-coated substrate. Precursor flowrates range from 0.02 to 5 mL/h under applied voltages of 1-18 kV, yielding droplet sizes around a few hundred nanometers. Comparing scanning electron microscope images of the coated samples showed that the substrate temperature, applied voltage, and precursor flowrate were the primary parameters controlling coating quality. Also, the most stable electrostatic spray mode that reliably produced uniform and fine droplets was the cone-jet mode with a Taylor cone issuing from the nozzle.