Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 17: II-VI Halbleiter I

HL 17.2: Talk

Tuesday, March 9, 2004, 10:30–10:45, H14

Blue ZnO: New insides from highly concentrated alcoholic colloids — •Michael Hilgendorff and Michael Giersig — caesar research center, Ludwig-Erhard-Allee 2, 53175 Bonn, Germany

UV illumination of colloidal ZnO-solutions generates electron-hole pairs in the nanoparticles which are diffuse to the particles surface where they can react with molecules in solution. While the electrons mainly react with oxygen the holes oxidize solvent molecules and surfactants. In the absence of oxygen the number of surface electrons increases which is accompanied by the occurrence of a broad absorption in the red and near infrared. Thus, ZnO-colloids become blue, which is visible with the naked eye in colloids having a concentration greater than 0.1 M. The influence of n- and p-doping of ZnO on this effect will be discussed.