Core Structure and Strain Field of a 90 Degree Disocation in Silicon

(a) What is the orientation of a 90 degree dislocation in Silicon?
(b) What is the core configuration of a 90 degree dislocation in Silicon?
(c) Is the strain (or stress) field of this dislocation radially symmetric?

adesh.zip :Click HERE to Download a DEMO version of ADESH
(ADESH works on PC-DOS. You will need the pkunzip.exe utility for this zipped file.)

Answer

We will take the following steps to answer this question:
(1) Create Silicon cell with following crystallographic orientation: X[-110], Y[001], Z[110].
(2) Place a 90 degree dislocation in the center of this cell.
(3) Relax the cell with static energy minimization technique.

(a) Atomic configuration calculated from ADESH is shown in the figure. The Dislocation line is at the center of the cell, perpendicular to the screen. Ideal silicon cell contains six atom rings for this orientation. The dislocation core is recognized by one seven atom ring and one five atom ring.

(b) Color coding is done to reflect the energy increase above the ideal value, i.e. -4.63 eV. Connecting atoms of similar color give constant stress/strain contours. Note that most strain energy is concentrated near the dislocation core. Furthermore, the stress/strain energy contours are elliptical (not circular) for this dislocation.

90 Degree Dislocation in Si

Questions? Comments? Suggestions?
Send a note to Anjali Nandedkar at CASA Engineering
info@casaengineering.com

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