AVS 51st International Symposium
    Nanometer-scale Science and Technology Thursday Sessions
       Session NS2-ThA

Paper NS2-ThA3
VLS Epitaxy of Si Nanowires: Kinetics and Morphology

Thursday, November 18, 2004, 2:40 pm, Room 213D

Session: Nanowires II
Presenter: T. Clement, Arizona State University
Authors: T. Clement, Arizona State University
J.L. Taraci, Arizona State University
J.W. Dailey, Arizona State University
D.J. Smith, Arizona State University
J. Drucker, Arizona State University
S.T. Picraux, Arizona State University
Correspondent: Click to Email
The high aspect ratios and novel electronic and chemical properties of silicon nanowires have made them increasingly interesting for applications ranging from flexible electronics to chemical sensors to microfluidic surfaces. However the mechanisms behind vapor-liquid-solid (VLS) crystal growth have received only limited attention since the seminal work of Wagner for whisker growth more than 30 years ago.@footnote 1@ Here we study the VLS kinetics and growth modes dominating CVD grown Si nanowires (SiNWs) as a function of growth pressure and temperature. In contrast to our previous studies of Ge nanowires, we observe SiNW growth throughout a wide range of pressures and temperatures. Au nanodots with a nominal thickness of 2.5 nm and average lateral separation of 30 nm are evaporated in UHV on hydrogen terminated Si(111) and Si(100) surfaces; these Au nanodots function as the seeding species for VLS nanowire growth. Subsequent growth using disilane (Si@sub 2@H@sub 6@) gas at pressures ranging from 1x10@super -2@ to 1x10@super -6@ Torr and temperatures ranging between 300°C and 700°C produces highly uniform SiNW structures at low temperatures and unstable structures at higher temperatures, specifically kinks and nonuniformity in SiNW diameter. The initiation of nanowire growth is a nucleation-limited process, and we also report on new in situ optical scattering studies of SiNW nucleation times. Finally, characterization via field-emission SEM, RBS, and TEM will establish the SiNW growth rate dependence on substrate temperatures and pressures. Examples of the dramatic superhydrophobic and superhydrophilic behavior of functionalized SiNW surfaces will be given. @FootnoteText@ @footnote 1@ R.S. Wagner, in Whisker Technology, Levit, A.P. ed, (Wiley-Interscience, New York, 1970) pp 47-119.