M. Altaf

Optical absorption studies of sodium cadmium phosphate glasses

Abstract A photoabsorption method was used to study the fundamental absorption edges in sodium cadmium phosphate glasses. The measurements were performed in the UV-visible region of the spectrum. The optical band gap energies lie in the range 2.82 to 3.48 eV and are found to decrease with increasing amount of sodium oxide. The extent of band tailing was worked out from the Urbach plots which show an exponential dependence of absorption coefficients on energies of the photons used.

Optical characteristics of some binary and ternary phosphate glasses

The optical absorption spectra of some binary and ternary phosphate glasses are studied in the UV-visible region by using a spectrophotometer. The observed absorbance versus wavelength curves do not show any sharp edges in these glasses. The optical band gap energies are found to depend significantly on glass composition. The optical band gap energy is found to increase with increasing ZnO content in binary and ternary glass systems.

EFFECT OF ZINC OXIDE ON THE BAND GAP OF CADMIUM–ZINC–PHOSPHATE GLASSES

The fundamental absorption edges of cadmium–zinc–phosphate glass samples were measured in the UV visible wavelength region of the spectrum by photoabsorption method. It is found that the optical band gaps of these glasses are composition-dependent and occur at a photon energy in the range 2.85–3.33 eV. The value of the optical band gaps enhances with ZnO content. The absorption coefficient depicts an exponential dependence on photon energy for the glass samples reported in this communication.

PHOTOCONDUCTIVE RESPONSE IN 9,10-ANTHRAQUINONE SINGLE CRYSTALS

The photoconductive response of ‘home-grown’ 9,10-anthraquinone single crystals has been studied using two types of cells — sandwich and surface types. The existence of true bulk conductivity as well as surface conductivity has been established in such crystals. The photocarrier mobility on the surface is much higher than in the bulk of the crystal specimens. The photocurrent dependence on wavelength in the range 380–550 nm and applied bias field up to 9 kV/cm has been examined in these crystals. The field dependence of photocurrent at constant wavelength shows a nonohmic behavior. The effect of making front-illuminated electrode positive or negative with respect to the back electrode is also examined and the photocurrent is found to be electronic in nature.