Electron-enhanced reactions responsible for photoluminescence spectrum change in II-VI compounds

Electron-enhanced reactions in II-VI compounds are shown to be caused by the presence of some mobile defects which diffusion is not enhanced under excitation. At the same time, electron-enhanced diffusion can be imitated in these reactions due to carrier trapping by deep centers that do or even do not take part in the reaction. To elucidate the real defect reaction mechanism a detailed study is required in every case. For this purpose, a method of mobile defect detection and their diffusion characteristic direct investigation has been elaborated

Effect of chemical modification of thin C₆₀ fullerene films on the fundamental absorption edge

Fullerene C₆₀ films were grown using physical vapor deposition on Si substrates at room temperature. Then chemical modification with cross-linking these films was performed using the reaction with 1,8-octanediamine (DA) or octane-1,8- dithiol (DT). These chemically cross-linked C₆₀ films are capable of stable binding the Ag or Au nanoclusters. Optical properties of the obtained nanostructured hybrid films were investigated by both reflectance spectroscopy and spectral ellipsometry within the spectral range 1.55 to 5.0 eV at various angles of incidence. From the spectral dependences of the extinction coefficient in the region of optical absorption edge, the physical nature of the fundamental allowed direct band-gap transitions between HOMOLUMO states Eg, the optical absorption edge near the intrinsic transition Eo, and exponential tail of the density-of-states caused by defects have been determined. Influence of chemical modification and decoration of metal nanoparticles on the above mentioned parameters has been analyzed

Optical and photoluminescent properties of nanostructured hybrid films based on functional fullerenes and metal nanoparticles

The chemically cross-linked C₆₀ thin films, capable of binding Ag or Au nanoparticles, were prepared by the gas-phase treatment with diamine for one set of samples and dithiol for another one and decoration with Ag or Au nanoparticles, respectively. The optical and photoluminescent properties of the obtained nanostructured hybrid films in comparison with the undecorated films were studied. The low temperature photoluminescence (PL) spectra demonstrate significant changes of the band intensity and appearance of fine structure for bands connected with radiative transitions of self-trapped and localized excitons. The decoration of pristine and treated C₆₀ films with Ag nanoparticles leads to a decrease of PL intensity and to slight bandgap reduction. These phenomena can be explained by the increase of the surface recombination velocity at the fullerene-nanoparticle interface. At the same time, the nanoparticles insignificantly decrease the transmittance of light into the fullerene and Si layers, and have almost no influence on photoelectric properties of metal/fullerene/Si barrier structures