Nanoparticle Deposition of Al<SUB>2</SUB>O<SUB>3</SUB> Powders on Various Substrates

Abstract

Most means of powder deposition impart high energy to the particles involved by means of high acceleration. Cold gas dynamic spray (CGDS) 1–3) and the aerosol deposition method (ADM) 4–6) are typical conventional processes. The depositional rate of both methods is faster than other traditional methods such as chemical vapor deposition or sputtering. In CGDS, the metallic powders exceed supersonic speed prior to being deposited on a substrate. In ADM, ceramic powders are accelerated to subsonic speeds. Both methods also offer the advantages of a low processing temperature and can be used with flexible substrates involving film deposition. ADM has been widely studied in various types of microstructure fabrication, especially in forming thick Lead Zirconate Titanate (PZT) films used in micro electro mechanical systems (MEMS). 7–10) In these cases, a sacrificial layer is employed to provide fine patterns or templates on the substrate. Nano particle deposition systems (NPDS) are novel methods of powder deposition that offer new benefits for both ceramic and metallic powders, not available with either CGDS or ADM. 11) Air provides the carrier gas to transport the particles that are accelerated up to supersonic speeds at the nozzle tip. The much greater velocity of the powder in NPDS is the major difference from ADM. Moreover, powder deposition occurs at room temperature, considerably lower than the conditions commonly used for CGDS. A previous study showed that NPDS can be used successfully to deposit a variety of powders on different substrates. 11)