Plasma Enhanced Atomic Layer Deposition on Powders

During the last decades atomic layer deposition (ALD) gained a lot of interest for coating three dimensional structures with ultrathin conformal films. Although mainly applied on silicon wafers in microelectronics and solar, experimental efforts confirmed the technique is also applicable to powders and particles. This opens a wide window of new opportunities for ALD such as catalytic activation of powder surfaces, encapsulation and modifying powder rheology. Up to recently only thermal ALD on powders had been reported. For some processes however, plasma enhanced ALD (PE ALD) would be preferable. The higher reactivity during PE ALD results in several advantages including higher deposition rates, lower deposition temperatures and higher purity, while it extends the library of materials that can be grown. This paper elaborates on a rotary reactor for thermal and plasma enhanced ALD on powders, including a brief study of coatings like Al2O3, AlN and TiN.