Web Release Date: December 29,
From ZnO Nanorods to Nanoplates: Chemical Bath Deposition Growth and Surface-Related Emissions
and
Key Lab of Materials Physics and Anhui Kay Lab of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, Anhui, China
Received: August 28, 2007
In Final Form: October 2, 2007
Abstract:
In this paper, a low-temperature controllable chemical bath deposition method was demonstrated to prepare
one-dimensional ZnO nanorods and two-dimensional nanoplates, and their surface-related emissions were
studied by temperature-dependent cathodoluminescence spectra. By changing the precursor concentration,
the ZnO morphology evolves from nanorods to nanoplates. ZnO nanorods grow fast along the c-axis direction
due to the high surface energy of the polar (0001) plane when the concentration of OH- ions is low in the
precursor solution. When the OH- concentration is increased, more OH- ions preferably adsorb on the (0001)
plane of ZnO, and the growth of the ZnO nanocrystallite along the c axis is partially suppressed. However,
they can still grow sideways along <2
0> directions. Therefore, with the OH- concentration increased, the
average aspect ratio (high/width) of ZnO nanorods is decreased. Finally, two-dimensional ZnO nanoplates
are formed. Low-temperature cathodoluminescence spectra of such ZnO nanostructures exhibit donor-bound
exciton emission and surface-state-related exciton emission caused by surface impurities. With increasing
temperature, the bound exciton emission decreases gradually due to the ionization of donors and finally vanishes
when the temperature is above 130 K. The near-band-gap ultraviolet emission at room temperature is dominated
by surface-related exciton emission.
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