During the first days of 2018, we have been working on a new Atomic Layer Deposition (ALD) reactor system as well as an entirely new material system for our group: tin (IV) oxide (SnO2). Given the novelty of both the reactor and the precursors (ozone and tetrakis(ethylamino) tin), it is not surprising that the first film produced by the reactor showed evidence of gas-phase particle production and high spatial non uniformity (see the left image).
The production of tin oxide particles was key to tracking down the source of our problems – insufficient purge time, as measured by our reactor pressure sensor, resulted in some residual precursor in the reactor chamber after each purge period, leading to gas-phase nucleation and particle growth in the reactor. After doubling the post-Sn and tripling the post-O3 purge periods, a visually uniform and particle-free film was produced (right image).
This work is part of a collaboration with Dr. Vivek Dwivedi of the NASA GSFC, is supported by NASA, and represents part of the PhD thesis research of Hossein Salami and Alan Uy.