Generation of positively charged nanoparticles by fracto-emission and their deposition into films during aerosol deposition

Abstract

Thin film growth through non-classical crystallization with a building block of charged nanoparticles (CNPs) has been studied in several fields, including chemical vapor deposition (CVD) and physical vapor deposition (PVD). To determine whether the same mechanism can be applied for aerosol deposition (AD) at room temperature, the generation and deposition behavior of CNPs were studied in the AD process for the first time. By measuring the current and examining the bias effect on the deposition behavior, it was confirmed that the fragmentation of Al2O3 particles generated numerous positively charged secondary nanoparticles as well as electrons by fracto-emission. The bias experiment indicated that positively charged secondary particles produced a dense film, whereas neutral secondary particles produced a porous film. The hypothesis that positive charges induce plastic deformation of secondary particles was supported by experiments and ab initio calculations. These results suggest that the positively charged secondary particles may be a major flux for film growth in the AD process.