A multiscale study of misfit dislocations in PbTe/PbSe(001) heteroepitaxy
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INTRINSIC AND EXTRINSIC SIZE EFFECTS IN MATERIALS
A multiscale study of misfit dislocations in PbTe/PbSe(001) heteroepitaxy Yang Li1,a), Zhaochuan Fan2, Weixuan Li1, David L. McDowell3, Youping Chen1 1
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, USA 3 Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA; and School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA a) Address all correspondence to this author. e-mail: yangli1991@ufl.edu 2
Received: 21 December 2018; accepted: 7 February 2019
In this work, we investigate misfit dislocations in PbTe/PbSe heteroepitaxial systems using the concurrent atomistic–continuum (CAC) method. A potential model containing the long-range Coulombic interaction and short-range Buckingham potential is developed for the system. By considering the minimum potential energy of relaxed interface structures for various initial conditions and PbTe layer thicknesses, the equilibrium structure of misfit dislocations and the dislocation spacings in PbTe/PbSe(001) heteroepitaxial thin films are obtained as a function of the PbTe layer thicknesses grown on a PbSe substrate. The critical layer thickness above which misfit dislocations inevitably form, the structure of the misfit dislocations at the interfaces, and the dependence of average dislocation spacing on PbTe layer thickness are obtained and discussed. The simulation results provide an explanation for the narrowing of the spread of the distribution of misfit dislocation spacing as layer thickness increases in PbTe/PbSe(001) heteroepitaxy.
Introduction Heteroepitaxy is a synthesis method that grows a crystalline film on a crystalline substrate of a different material. It is one of the most widely used methods for depositing semiconductor and metallic materials to form thin films or multilayers. The most important type of defects in heteroepitaxial systems is misfit dislocation. In heteroepitaxial growth of films or multilayers with large lattice mismatch, misfit dislocations are generated in the heterostructures when the epilayer thickness exceeds a critical value. This critical thickness can range from a few nanometers to tens or hundreds of nanometers, depending on the lattice mismatch and the growth direction. Misfit dislocations play a significant role in influencing the functional performance of the systems, including electrical, optical, thermal and mechanical performances. Consequently, extensive experimental and theoretical research efforts have been dedicated to understanding the details of the misfit dislocations in epitaxial heterostructures. There are two early theories for the interpretation of experimental observations and for the prediction of critical thickness. The first theory was proposed by Frank and van der
ª Materials Research Society 2019
Merwe (FM) in 1949 [1, 2]. The FM theory is b
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