The role of type II FB (I):Tl+ defect in laser light generation and color image formation at the low coordination surface sites of AgBr: ab initio calculations

• Published in: Current applied physics 2006, 6(1), , pp.19-31
• Main Authors: A.S. Shalabi, A.S. Algaber, N.K. Madi, Kh.M. Eid, Z.M. Fathy
• Format: Article
• Language: Korean
• Subjects: 물리학
• ISSN: 1567-1739; 1878-1675

The role of type IIFB (I):Tl+ color center at low coordination surface sites of AgBr thin lms in providing tunable laser activitystructure calculations. Clusters of variable sizes were embedded in simulated Coulomb elds that closely approximate the Madelungelds of the host surfaces, and ions that are the nearest neighbors to theFB defect site were allowed to relax to equilibrium in eachcase. The calculated Stokes shifted optical transition bands suggest that laser activity is relatively weak and fades quickly as thecoordination number of the surface ions decreases from 5 (at) to 4 (edge) to 3 (corner). An attempt has been made to explain thesesurfaces were deep below the lower edges of the conduction bands of the ground-state defect-free surfaces indicating that type IIFB(I):Tl+ is suitable laser defect. The probability of orientational destruction of the two centers, attributed to the assumed saddlepoint ion congurations along theh110i axis, was found to decrease as the coordination number of the surface ions decreases. Thepossibility of exciton (energy) transfer between sites of dierent coordination numbers was claried. The GlasnerTompkins empir-ical relation was generalized to include type IIFB (I):Tl+ doped surfaces. As far as photographic sensitization is concerned, a super-sensitizer increases the sensitizing capabilities of the two examined dye molecules by increasing the relative yield of quantumeciencyU.FA sensitizes the low coordination surface sites of the defect free AgBr by lowering the bottoms of the conductionbands. The dierence in the sensitizing capabilities between the two examined dyes was estimated by calculating the quasi Fermilevels. KCI Citation Count: 4