The Influence Of Stress On The Optical And Electrical Properties Of Nanocrystals

Growth of nanocrystals embedded in a host matrix can lead to substantial stresses. Understanding of the role of growth stresses on electrical and optical properties of nanocrystals is critical to realizing its full potential in future technological application. In the thesis, the strain distributions generated by the thermal expansion mismatch because of the growth of nanocrystals embedded in a host matrix are qualitatively simulated by two dimensional finite element calculations, which are performed using a commercial software package ANSYS.In this thesis, we fabricated nanocrystals embedded in solid state matrix using pulsed laser deposition (PLD) method. Surface morphology, microstructure and optical properties of the as-deposited and annealed sample were characterized and analyzed using Raman spectra, transmission electron microscopy (TEM), photoluminescence (PL) and C-V measurements. Meanwhile, with the simulation results of large-scale finite element analysis software of ANSYS10.0, we found that growth of nanocrystals embedded in a host matrix can lead to substantial stresses because the Young modulus and Poisson's ratio of matrix and nanocrystals were different. Both the same nanocrystals embedded in different host matrix and different nanocrystals embedded in the same host matrix-, the stress experienced by nanocrystals are much different, which result in much defects generated in or at the interface of nanocrystals during the growth of nanocrystals to relax the stress. And, the stronger stress experienced by nanocrystals, the more defects generated. PL results and the C-V characteristics also indicated that these defects have significantly influence on photoluminescence and electrical storage properties.