BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:2
UID:UW-Physics-Event-4639
DTSTART:20171102T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T021756Z
LAST-MODIFIED:20171030T161532Z
LOCATION:Chamberlin 5310
SUMMARY:Design and Synthesis of 1D and 2D Nanomaterials Away from Equi
 librium\, R. G. Herb Condensed Matter Seminar\, Xudong Wang\, UW-Madis
 on (Materials Science and Engineering)
DESCRIPTION:Morphology is one essential element that gives rise to ext
 raordinary physical\, chemical\, and mechanical properties in nanomate
 rials. Precise morphology control of nanomaterials is a notorious task
 \, which heavily relies on fundamental understanding of the governing 
 mechanisms and kinetics at the nanoscale. In this talk\, I will presen
 t our three recent discoveries of the growth kinetics in 1D and 2D nan
 omaterial evolution. Firstly\, the surface-reaction-limited pulsed che
 mical vapor deposition (SPCVD) technique will be discussed. The SPCVD 
 technique effectively decouples the crystal growth from precursor vapo
 r concentration\, thus makes the conform growth of dense NW arrays ins
 ide highly-confined submicron-sized spaces possible. The evolution of 
 NRs was found to be a manifestation of the Ostwald-Lussac Law. SPCVD o
 pens a new route toward the design and creation of complex 3D hierarch
 ical nanostructures\, which can advantageously impact the devices perf
 ormance of solar energy harvesting. Secondly\, I will present our disc
 overy of the wedding cake growth mechanism in the formation of 1D and 
 2D ZnO nanostructures. Within a narrow kinetic window\, the surfaces o
 f the 1D and 2D structures were covered with a unique concentric terra
 ce feature\, different from the screw-dislocation features. An interes
 ting 1D to 2D morphology transition was found during the wedding cake 
 growth\, when the adatoms overcome the Ehrlich-Schwoebel (ES) barrier.
  At last\, I will present a new ionic layer epitaxy (ILE) technique th
 at uses surfactant monolayers to serve as soft templates guiding the n
 ucleation and growth of 2D nanomaterials in large area beyond the limi
 tation of van der Waals solids. One- to two-nm-thick\, single-crystall
 ine free-standing ZnO nanosheets with sizes up to tens of micrometers 
 were synthesized at the water-air interface. ILE of other metals and o
 xides have also been proved to be successful. 
URL:https://www.physics.wisc.edu/events/?id=4639
END:VEVENT
END:VCALENDAR