Electronic band structures and surface states were investigated for ZnO finite wells or slabs grown along <0001> and <1-100> directions using tight binding representation. The dangling bonds on two end-surfaces caused surface bands for different directions grown slabs, of which the wavefunctions tend to localize at the end surfaces. The increasing splitting of the degenerate surface bands at the Γ point was observed decreasing with the thickness of the nonpolar [1-100] slab. And, the quantum confinement effect is distinctively enhanced by the extra electron-field induced in the <0001> grown finite well with the polar end-surfaces.
AbstractSilicon nanocrystals were in situ grown in a silicon nitride film by plasma enhanced chemical vapor deposition. The size and structure of silicon nanocrystals were confirmed by high-resolution transmission electron microscopy. Depending on the size, the photoluminescence of silicon nanocrystals can be tuned from the near infrared (1.38 eV) to the ultraviolet (3.02 eV). The fitted photoluminescence peak energy as E(eV) = 1.16 + 11.8/d2 is an evidence for the quantum confinement effect in silicon nanocrystals. The results demonstrate that the band gap of silicon nanocrystals embedded in silicon nitride matrix was more effectively controlled for a wide range of luminescent wavelengths.
THE PHOTOLUMINESCENCE MECHANISM STUDY IN SILICON NANOCRYSTALS: A QUANTUM CONFINEMENT EFFECT (QCE) MODEL INVESTIGATION
