Effect of ion implantation on the electronic structure of bismuth

The magnetoreflection technique has been used to determine the effects of isoelectronic implantation on the bismuth electronic structure as a function of various implantation parameters, including fluence and size of implanted species, temperature of sample during implantation, and ion-beam current. Measured changes in the magnetic energy subbands have been related to strains and defects introduced into the crystal lattice by the implantation process. Implantation-induced strains have been shown to be the cause of a decrease in the L-point energy-band gap. A model has been proposed to calculate the strains which are then related to the measured energy gap changes via deformation potential theory. Extended x-ray-absorption fine-structure and Rutherford-backscattering channeling measurements locate the implanted atoms preferentially at substitutional sites for implantation temperatures of 50?deC and at interstitial sites for lower temperatures. Interstitials give rise to inversion-symmetry-breaking magneto-optical transitions and a broadening of the resonance linewidth. Observation of a line-shape reversal indicates an increase of the plasma frequency by an order of magnitude for Bi-ion fluences 2×1015 cm-2.