Deposition of conductive TiN shells on SiO₂ nanoparticles with a fluidized bed ALD reactor

Conductive TiN shells have been deposited on SiO₂ nanoparticles (10–20 nm primary particle size) with fluidized bed atomic layer deposition using TDMAT and NH₃ as precursors. Analysis of the powders confirms that shell growth saturates at approximately 0.4 nm/cycle at TDMAT doses of >1.2 mmol/g of powder. TEM and XPS analysis showed that all particles were coated with homogeneous shells containing titanium. Due to the large specific surface area of the nanoparticles, the TiN shells rapidly oxidize upon exposure to air. Electrical measurements show that the partially oxidized shells are conducting, with apparent resistivity of approximately ~11 kΩ cm. The resistivity of the powders is strongly influenced by the NH₃ dose, with a smaller dose giving an order-of-magnitude higher resistivity.