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Surface strain engineering through Tb doping to study the pressure dependence of exciton-phonon coupling in ZnO nanoparticles

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Title Surface strain engineering through Tb doping to study the pressure dependence of exciton-phonon coupling in ZnO nanoparticles
 
Creator SHARMA, A
DHAR, S
SINGH, BP
NAYAK, C
BHATTACHARYYA, D
JHA, SN
 
Subject OPTICAL-PROPERTIES
SIZE DEPENDENCE
SEMICONDUCTOR NANOSPHERES
QUANTUM DOTS
PHOTOLUMINESCENCE
ELECTRON
SCATTERING
DYNAMICS
PHASES
CDSE
 
Description A compressive hydrostatic strain has been found to develop in the ZnO lattice as a result of accumulation of Tb ions on the surface of the nanoparticles for Tb mole-fraction less than 0.04. This hydrostatic strain can be controlled up to approximate to 14 GPa by varying the Tb mole-fraction. Here, we have utilized this novel technique of surface strain engineering through Tb doping for introducing hydrostatic compressive strain in the lattice to study the pressure dependent electronic and vibrational properties of ZnO nanoparticles. Our study reveals that when subjected to pressure, nanoparticles of ZnO behave quite differently than bulk in many aspects. Unlike bulk ZnO, which is reported to go through a wurtzite to rock-salt structural phase transition at approximate to 8 GPa, ZnO nanoparticles do not show such transition and remain in wurtzite phase even at 14 GPa of pressure. Furthermore, the Gruneisen parameters for the optical phonon modes are found to be order of magnitude smaller in ZnO nanoparticles as compared to bulk. Our study also suggests an increase of the dielectric constant with pressure, which is opposite to what has been reported for bulk ZnO. Interestingly, it has also been found that the exciton-phonon interaction depends strongly upon pressure in this system. The exciton-phonon coupling has been found to decrease as pressure increases. A variational technique has been adopted to theoretically calculate the exciton-LO phonon coupling coefficient in ZnO nanoparticles as a function of pressure, which shows a good agreement with the experimental results. These findings imply that surface engineering of ZnO nanoparticles with Tb could indeed be an efficient tool to enhance and control the optical performance of this material. (C) 2013 AIP Publishing LLC.
 
Publisher AMER INST PHYSICS
 
Date 2014-10-15T08:32:52Z
2014-10-15T08:32:52Z
2013
 
Type Article
 
Identifier JOURNAL OF APPLIED PHYSICS, 114(21)
0021-8979
1089-7550
http://dx.doi.org/10.1063/1.4838055
http://dspace.library.iitb.ac.in/jspui/handle/100/14692
 
Language en