ABSTRACT
We studied the optical sensing properties of ZnO nanoparticles prepared by spray pyrolysis. To investigate their optical sensing performance, we incubated peptides on ZnO nanoparticles. The photoluminescence (PL) peak intensity of peptides on the ZnO nanoparticles was higher than that of peptides on the ZnO film or on the glass plate. This observed PL enhancement is attributed to the optical confinement of ZnO nanoparticles. The low-temperature spectra displayed a strong exciton emission peak with multiple sidebands, attributed to the bound exciton and its longitudinal optical phonon sidebands. The strong exciton emission is thought to be the combined effect of optical confinement due to the nanoparticle geometry, reduction of defect emission by thermal annealing, and reduction of non-radiative relaxation at low temperatures.
ABSTRACT
Graphene/Si quantum dot (QD) heterojunction diodes are reported for the first time. The photoresponse, very sensitive to variations in the size of the QDs as well as in the doping concentration of graphene and consistent with the quantum-confinement effect, is remarkably enhanced in the near-ultraviolet range compared to commercially available bulk-Si photodetectors. The photoresponse proves to be dominated by the carriertunneling mechanism.
Subject(s)
Electrical Equipment and Supplies , Graphite/chemistry , Nanowires/chemistry , Quantum Dots/chemistry , Silicon/chemistry , Electrons , Hydrophobic and Hydrophilic Interactions , Lasers , Microscopy, Electron, Transmission , Photochemical Processes , Photons , Quantum Theory , Silicon Dioxide/chemistry , Ultraviolet RaysABSTRACT
We have characterized the structural properties of the ternary In(x)Ga(1-x)As nanowires (NWs) grown on silicon (Si) substrates using metalorganic chemical vapor deposition (MOCVD). Au catalyzed vapor-liquid-solid (VLS) mode was used for the NW growth. The density of the In(x)Ga(1-x)As NW array grown under optimized condition exceeds 1 x 10(8)/cm2. X-ray diffraction (XRD) spectra confirm the In composition (x = 0.9-0.3) of the In(x)Ga(1-x)As nanowires which bandgap energy can cover the entire near-infrared (NIR) range. Massive stacking faults and twin planes were observed but no misfit dislocation was found along the NWs as confirmed by transmission electron microscopy (TEM). The energy-dispersive X-ray spectroscopy (EDS) analysis shows the gradual variation of In composition along the NW.
