Effect of Strong Electric Field on the Exciton Absorption Lines in Some Films

Abstract

The spectral dependence of the electro-absorption of single crystal CdS and PbI2 films was examined at 77 K in the exciton absorption region. In the electro-absorption spectrum of CdS there are three negative peaks whose positions are independent of the electric field, and these positions coincide with the positions of three exciton absorption lines of CdS. The dependence of the electro-absorption peak amplitudes on the electric field is linear at weak fields and saturates at Fcr = 1.45 × 105 V/cm. This fact indicates complete disappearance of the exciton absorption lines in such a field. The value of Fcr is in good agreement with theoretical results of Ralph. The electro-absorption spectrum of PbI2 is also closely associated with the exciton structure of the absorption spectrum. However, in this case the exciton absorption line is shifted by an electric field to the shortwave side by 23 Å at F = 2.85 × 105 V/cm.