Optical absorption of Ag-BaO thin film in the visible and near-infrared region with applied electric field

The optical absorption properties of Ag-BaO composite thin film with excess barium were measured while a vertical electric field was applied on the fi lm surface. Total two absorption peaks were observed in the visible and nea r-infrared region,and only the peak that lies in the near-infrared region w as dependent on the applied electric filed,i.e.,the absorption intensity wa s decreased with the increasing electric field. The dominant peak in the vi sible region is attributed to the surface plasmons resonance of Ag ultrafin e particles embedded into the BaO semiconductor matrix. However, the weaker one in the near-infraed region is considered to arise from the transition of bound electrons at impurity energy level of the BaO semiconductor matrix , and such an impurity energy level is related to the negative ion vacancie s caused by the excess braium in the BaO crystal. When the external surface electric field was applied,some of the impurities in the BaO Semiconductor matrix were ionized,and which further resulted in a decrease of the densit y of bound electrons at the impurity energy level. So that,part of the opti cal absorption owing to the impurity energy level was decreased with the en hanced electric field.