Yao, Y.-F.Y.-F.YaoTu, C.-G.C.-G.TuChang, T.-W.T.-W.ChangChen, H.-T.H.-T.ChenWeng, C.-M.C.-M.WengSu, C.-Y.C.-Y.SuHsieh, C.C.HsiehLiao, C.-H.C.-H.LiaoCHIH-CHUNG YANGYEAN-WOEI KIANG2020-06-112020-06-11201519448244https://scholars.lib.ntu.edu.tw/handle/123456789/497825https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930216351&doi=10.1021%2facsami.5b02063&partnerID=40&md5=fc8fa12e662b24b8cf76649907cd1637The molecular beam epitaxy growth of highly degenerate Ga-doped ZnO (GaZnO) nanoneedles (NNs) based on the vapor-liquid-solid (VLS) growth mode using Ag nanoparticles (NPs) as the growth catalyst is demonstrated. It is shown that when the growth substrate temperature is sufficiently high, a portion of a Ag NP can be melted for serving as the catalyst to precipitate GaZnO on the residual Ag NP and form a GaZnO NN. Record-low turn-on and threshold electric fields in the field emission test of the grown GaZnO NNs are observed. Also, a record-high field enhancement factor in field emission is calibrated. Such superior field emission performances are attributed to a few factors, including (1) the low work function and high conductivity of the grown GaZnO NNs due to highly degenerate Ga doping, (2) the sharp-pointed geometry of the vertically aligned GaZnO NNs, (3) the Ag doping in VLS precipitation of GaZnO for further reducing NN resistivity, and (4) the residual small Ag NP at the NN tip for making the tip even sharper and tip conductivity even higher. © 2015 American Chemical Society.field emission; Ga-doped ZnO; growth catalyst; nanoneedle; vapor-liquid-solid modeCatalysts; Electric fields; Field emission; Gallium; Molecular beam epitaxy; Nanoneedles; Zinc oxide; Emission performance; Field emission tests; Ga-doped ZnO; High conductivity; Threshold electric fields; Vapor liquid solids; Vapor-liquid-solid growth; Vertically aligned; Silverjournal article10.1021/acsami.5b020632-s2.0-84930216351