29 research outputs found
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