First-Principles Calculations Of Silicon Interstitial Defects At The Amorphous-Sio2/Si Interface

The migration barriers and formation energies of the silicon interstitials in an amorphous-SiO2/Si (a-SiO2/Si) interface are investigated in this work. The migration dynamics and energy profiles of the interstitials in the sublayers and the a-SiO2/Si interface are compared using the CI-NEB method. The results indicate that the neutral interstitial defects may migrate into a-SiO2/Si interface via several low-barrier channels, and get trapped at the interface because of the high energy barrier of the reverse migration. In addition, the formation energies and the charge transition levels of the interstitial defects at the a-SiO2/Si interface are also calculated with sophisticated corrections. The classical electrostatic calculation based on the finite element method is introduced to correct the long-range Coulomb interactions between the charged defect and its periodic images. The formation energy of the neutral interstitial defect shows dependence on the layer depth beneath the interface due to the unevenly distributed strain. The neutral interstitials on the H and split-< 110 > sites are close in energy and are 0.2-1.3 eV higher than those on the split-< 111 >. Besides, the tetrahedral site is the most stable configuration in the double-positive charge state. In fact, the stable site for the interstitial silicon in the a-SiO2/Si interface depends on the relative position of the Fermi level and the interfacial strain.