Atomic structures and energetics of 90°dislocation cores in Ge films on Si(001)

We report on atomic structures and energetics of 90°dislocation cores in Ge films on Si(001) substrates on the basis of the first-principles total-energy calculations. The dislocation core structure consisting of a row of pairs of five- and seven-membered Ge rings is proposed and found to be stable with increasing Ge overlayers. The scanning tunneling microscopy images of the 90°dislocation core structure are calculated and show the possibility to observe the proposed core structure.