Nanoparticle Deposition of Al2O3 Powders on Various Substrates

Al2O3 powders of 100 nm diameter were deposited on Al, Cu, and Si substrates using a micro-nozzle in nano-particle deposition system (NPDS). This procedure allowed the production of fine-scale depositional patterns or templates not possible using conventional semiconductor processing techniques. For a given set of depositional conditions, the Al2O3 powder layers developed different thicknesses on different substrates. Following deposition, the powders were sintered to provide ceramic layers. In the first instance, the depositional behavior of Al2O3 was determined by Stokes number, where a number greater than 1 meant that more powder was deposited. However, the extent of deposition was also influenced by substrate type, where a Si substrate yielded the thickest powder layer. This phenomenon was related to both substrate hardness and melting temperature. Most powder particles fragmented on impact (with pieces deposited on the substrate) when substrate hardness was high. In addition, when the melting temperature of substrate was low, more powder accumulated as a result of the kinetic energy of a colliding powder particle being transformed into heat. The Al substrate, with its relatively low melting point, developed a thicker powder deposit than those formed on Cu. Therefore, hardness and melting temperature of substrates are the key parameters influencing the depositional behavior of powders. [doi:10.2320/matertrans.M2009272]