Nucleation and Growth of Silver Nanoparticles by AB and ABC-Type Atomic Layer Deposition

In this work, we report synthesis strategies to produce Ag nanoparticles by AB-type and ABC-type atomic layer deposition (ALD) using trimethylphosphine(hexafluoroacetylacetonato) silver(I) ((hfac)Ag(PMe3)) and formalin (AB-type) and (hfac)Ag(PMe3), trimethylaluminum, and H2O (ABC-type). In situ quartz crystal microbalance measurements reveal a Ag growth rate of 1−2 ng/cm/cycle by ABC-type ALD at 110 °C and 2−10 ng/cm/cycle for AB-type ALD at 170−200 °C. AB-type Ag ALD has a nucleation period before continuous linear growth that is shorter at 200 °C. Transmission electron microscopy reveals that AB-type Ag ALD particles have an average size of ∼1.8 nm after 10 cycles. ABC-type Ag ALD particles have an average size of ∼2.2 nm after 20 cycles. With increasing ALD cycles, ABC-type Ag ALD increases the metal loading while maintaining the particle size but AB-type Ag ALD results in the formation of bigger particles in addition to small particles. The ability to synthesize supported metal nanoparticles with well-defined particle sizes and narrow size distributions makes ALD an attractive synthesis method compared to conventional wet chemistry techniques.