Direct Observation of Transient Surface Species during Ge Nanowire Growth and Their Influence on Growth Stability Saujan V. Sivaram Naechul Shin Li-Wei Chou Michael A. Filler 10.1021/jacs.5b03818.s001 https://acs.figshare.com/articles/journal_contribution/Direct_Observation_of_Transient_Surface_Species_during_Ge_Nanowire_Growth_and_Their_Influence_on_Growth_Stability/2141395 Surface adsorbates are well-established choreographers of material synthesis, but the presence and impact of these short-lived species on semiconductor nanowire growth are largely unknown. Here, we use infrared spectroscopy to directly observe surface adsorbates, hydrogen atoms and methyl groups, chemisorbed to the nanowire sidewall and show they are essential for the stable growth of Ge nanowires via the vapor–liquid–solid mechanism. We quantitatively determine the surface coverage of hydrogen atoms during nanowire growth by comparing ν­(Ge–H) absorption bands from <i>operando</i> measurements (i.e., during growth) to those after saturating the nanowire sidewall with hydrogen atoms. This method provides sub-monolayer chemical information at relevant reaction conditions while accounting for the heterogeneity of sidewall surface sites and their evolution during elongation. Our findings demonstrate that changes to surface bonding are critical to understand Ge nanowire synthesis and provide new guidelines for rationally selecting catalysts, forming heterostructures, and controlling dopant profiles. 2015-08-12 00:00:00 hydrogen atoms Ge Nanowire Growth Ge nanowire synthesis semiconductor nanowire growth sidewall surface sites Transient Surface Species nanowire sidewall Growth StabilitySurface adsorbates