Correlation between surface phonon mode and luminescence in nanocrystalline CdS thin films: An effect of ion beam irradiation
- Department of Physics, Bareilly College, Bareilly 243 005, Uttar Pradesh (India)
- Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)
- Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India)
The influence of swift heavy ion irradiation (SHII) on surface phonon mode (SPM) and green emission in nanocrystalline CdS thin films grown by chemical bath deposition is studied. The SHII of nanocrystalline CdS thin films is carried out using 70 MeV Ni ions. The micro Raman analysis shows that asymmetry and broadening in fundamental longitudinal optical (LO) phonon mode increases systematically with increasing ion fluence. To analyze the role of phonon confinement, spatial correlation model (SCM) is fitted to the experimental data. The observed deviation of SCM to the experimental data is further investigated by fitting the micro Raman spectra using two Lorentzian line shapes. It is found that two Lorentzian functions (LFs) provide better fitting than SCM fitting and facilitate to identify the contribution of SPM in the observed distortion of LO mode. The behavior of SPM as a function of ion fluence is studied to correlate the observed asymmetry (Γ{sub a}/Γ{sub b}) and full width at half maximum of LO phonon mode and to understand the SHII induced enhancement of SPM. The ion beam induced interstitial and surface state defects in thin films, as observed by photoluminescence (PL) spectroscopy studies, may be the underlying reason for enhancement in SPM. PL studies also show enhancement in green luminescence with increase in ion fluence. PL analysis reveals that the variation in population density of surface state defects after SHII is similar to that of SPM. The correlation between SPM and luminescence and their dependence on ion irradiation fluence is explained with the help of thermal spike model.
- OSTI ID:
- 22308523
- Journal Information:
- Journal of Applied Physics, Vol. 116, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ASYMMETRY
CADMIUM SULFIDES
CORRELATIONS
CRYSTAL DEFECTS
CRYSTALS
DEPOSITION
HEAVY IONS
MEV RANGE 10-100
NANOSTRUCTURES
NICKEL IONS
PHOTOLUMINESCENCE
POPULATION DENSITY
RAMAN SPECTRA
SIMULATION
SPECTROSCOPY
SURFACES
THERMAL SPIKES
THIN FILMS