Deposition of aluminum oxide by evaporative coating at atmospheric pressure (ECAP)

The Center for Plasma-Material Interaction (CPMI) has developed innovative coating method of evaporative coating at atmospheric pressure (ECAP). This new idea is an atmospheric-pressure-based process. Following the similar concept as the laser-assisted plasma coating at atmospheric pressure (LAPCAP) [1], the material captured by the plasma plume is atomic in nature (the evaporated metal atom) and should therefore end up deposited molecule-by-molecule as in a PVD fashion. By using the thermal energy from the microwave plasma, solid 99.99%+purity aluminum were evaporated and then produce a PVD-like alumina coating on a work piece. The aluminum target was inserted in the center of the microwave torch feeding a melt pool and evaporated into the surrounding plasma plume. A bottle neck was made in the antenna and could reduce the heat loss by 84%, thus allowing higher temperatures to exist in the sample-holder antenna tip. Gas shielding was used to keep the work gas pure. The film was deposited as Al2O3 using oxygen from the environment. Deposition rate was around 2μm/min. Gas flow rate around the antenna tip was about 0.9m/s, and the temperature of the plasma was about 1400°C at 1350W input power from simulations. Alpha and other metastable phases of aluminum oxide were found on the deposited films. •Aluminum oxide film deposited with metal aluminum target in atmospheric pressure.•Film characterization techniques were performed on the film deposited.•Film deposition rate was found to be around 2μm/min.•Phase of alumina nanocrystal could be identified by measuring the d-spacing on the TEM images and comparing to known data.