Abstract
The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and 90° full-edge dislocation. The full-field strains at the Ge/Si heterostructure interface were mapped by using the geometric phase analysis (GPA) and peak pairs analysis (PPA), respectively. The effect of the mask size on the GPA and PPA results was analyzed in detail. For comparison, the theoretical strain fields of the misfit dislocations were also calculated by the Peierls-Nabarro and Foreman dislocation models. The results showed that the optimal mask sizes in GPA and PPA were approximately three tenths and one-tenth of the reciprocal lattice vector, respectively. The Foreman dislocation model with an alterable factor a = 4 can best describe the strain field of the misfit dislocation at the Ge/Si heterostructure interface.
Highlights
Heterostructures have a wide range of applications, including electronic, optoelectronic, and energy conversion devices [1,2,3]
It is seen that the only defects in the Ge/Si heterostructure are the misfit dislocations located at the Ge/Si interface
Given that the atomic arrangements of the 60° dislocation were projected onto the high-resolution transmission electron microscopy (HRTEM) image, the Burgers vector decided by the current Burgers circuit in Figure 1b is the edge component corresponding to the Burgers vector 1/2[ 101 ] in the projection plane [31]
Summary
Heterostructures have a wide range of applications, including electronic, optoelectronic, and energy conversion devices [1,2,3]. Analyzing misfit dislocation and strain fields at the heterostructure interface is highly significant for the material performance improvement and extensive application potential. By selecting a geometric phase image, a desired numerical Moiré image corresponding to a group of special crystal planes can be obtained, allowing a detailed analysis of this group of crystal planes [26]. For the both methods above, the selection of mask size is a necessary process, which has very important effect on the calculation results of strain fields. The theoretical strain fields were mapped by Peierls-Nabarro and Foreman dislocation models
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