Long Range and Collective Impact of Au Surface Adatoms on Nanofin Growth
Babak Nikoobakht, Aaron Johnston-Peck, Jerry Tersoff
In the Au-catalyzed vapor-liquid-solid (VLS) growth of semiconductor nanowires, individual Au nanodroplets can result in single nanowires per site. However, growth of single nanofins per site using the same process becomes unpredictable. Our results show that as the size of a Au catalyst pattern reduces to microscale and smaller, the lateral fin growth becomes a less probable outcome and instead lateral nanowires prevail as the dominant product. In this report, we reveal the origin of this phenomenon and a novel aspect of Au catalysis in growth of ZnO nanostructures. While a Au nanodroplet drives the elongation of the lateral nanowire on the surface via a VLS process, we show that the surface-adsorbed Au atoms at the vapor-semiconductor interface catalyze the out-of-plane growth on the (0002) ZnO plane resulting in fins. Results suggest that this out-of-plane growth depends on the concentration available Au adatoms on (0002) plane, and in its absence only an isotropic growth of ZnO facets occur. As the Au thickness is increased from 2 nm to 8 nm, the out-of-plane fin growth rate increases. Beyond this thickness, the fin growth abruptly stops and only nanowires form. We attribute this behavior to a decline in the Au surface adatom concentration in response to the lower chemical potential (Gibbs-Thomson vapor pressure) of Au as the particle size increases. Results show that the fin formation from a given catalyst pattern strongly depends on the arrangement of the neighboring catalyst patterns, their shape and thickness. These findings enable strategies to facilitate controlled single fin formation in ordered arrays using micro- and sub-micron size catalyst patterns.
, Johnston-Peck, A.
and Tersoff, J.
Long Range and Collective Impact of Au Surface Adatoms on Nanofin Growth, Journal of Physical Chemistry C, [online], https://doi.org/10.1021/acs.jpcc.3c04726, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956146
(Accessed December 10, 2023)