Raman scattering from InAs nanocrystals embedded in SiO2 thin films has been measured and studied. Raman spectra of InAs nanocrystals have a similar feature with that of bulk InAs crystal. Broadened and red-shifted Raman scattering peaks were observed from the nanocrystals; this has been attributed to the phonon confinement effect. A compressive stress in the interface between InAs nanocrystals and the SiO2 matrix was also taken into account to interpret the red shift.
A metal nanoparticles-composite thin film (Ag-BaO), doped by rare-earth elements, was grown by vacuum deposition. Compared with the normal Ag-BaO thin film, the photoemission current of the doped Ag-BaO thin film increases by about 40%. The transmission electron micrograph indicated that Ag nanoparticles become smaller when doped with rare-earth. With the smaller size of Ag nanoparticles, photoelectrons are easier to transgress from Ag nanoparticles via tunnel effect. Thus the photomission current increases.
The optical absorption properties of BaO semiconductor thin films deposited by v acuum evaporation were measured when a vertical electric field was applied on th e surface of the thin films.Enhanced absorption in the near-ultraviolet band was observed.The absorption was increased with the increased intensity of applied e lectric field.Theoretical analysis indicates that the energy-band edges of BaO s emiconductor become bent on the application of electric field,and there is an in creased probability for electrons in the valence band to tunnel through the forb idden gap according to the quantum-mechanics.As a result,it becomes possible for the photons with energy less than Eg to be absorbed by the electrons ,and which leads to the enhanced photoabsorption of BaO thin films in the near-u ltraviolet band.Franz-Keldysh effect and Stark effect were used to explain the e lectroabsorption spectrum when metal oxide semiconductor was excited by the phot ons with energy less or more than Eg.
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