Abstract
We study the influence of the substrate tilt angle on the microstructure and optoelectronic properties of gallium-doped zinc oxide (GZO) thin films deposited by the atmosphere pressure plasma jet (APPJ) method. The nozzle trajectories play a key role in oblique angle deposition. In the process of oblique angle deposition, if the nozzle scanned from the upstream side to the downstream side, the electrical properties such as resistivity, carrier concentration and mobility deteriorate considerably. The optical properties also worsen — specular transmittance goes down and diffuse transmittance increase to a significant amount. This degradation can be attributed to the “pre-deposition” of the GZO adsorbed particles (ad-particles) on the downstream side of the raw glass where the nozzle has not scanned. These GZO ad-particles serve as nuclei on which the incoming vapor particles deposit preferentially. Scanning electron microscopy (SEM), and grazing incidence X-ray diffraction (GIXRD confirmed that the film near the downstream is thicker, less smooth, and porous than that near the upstream. The undesirable situation can be mitigated or even completely removed via proper nozzle scanning trajectories — reversing the scanning trajectory of the nozzle. If the nozzle scans from the downstream side to the upstream side, no pre-deposition of the GZO ad-particles to deteriorate the film properties and therefore the obliquely deposited films perform as well as the films deposited without tilt, i.e. flat substrate. This work presents a solution to the challenge of depositing TCO on tilted and curved surfaces.
