First principles investigations of Fe3+ impurity and Fe3+ + V−Cd complex in strongly confined CdSe quantum dot

Abstract

Solitary dopant or defect in a semiconductor is the basis of the emerging field of optoelectronics known as solotronics. It has been shown that the spin of a single magnetic ion impurity can be manipulated optically. Among the magnetic ions, Fe3+ has been proposed as a primary candidate for the design of quantum dots (QDs) for solotronics because of its zero nuclear spin in contrast to Mn2+ and larger magnetic moment compared to Fe2+. In this work, we performed density function theory calculations to determine optimal parameters for the colloidal synthesis of single FeCd3+over FeCd2+ in CdSe of 1 nm in radius. We also investigated Fe3+ plus Cd vacancy complex (FeCd3++VCd−). Transition energy level calculations show FeCd3+ to be a deep-level donor and VCd− to be a shallow acceptor. Charge difference plots show that the charge of the ionized electron is localized around FeCd3+. Tetrahedral symmetry is retained at the FeCd3+ site. The magnetic moment of Fe3+ is almost the same in the core and at the surface and is equal to ∼4.27 μB for passivated QD. The large moment can be manipulated for spin control in conjunction with unoccupied vacancy states of the triplet t2 level of the shallow VCd acceptor to create a hole spin current in a lithographically patterned surface.