Effect of swift heavy ion irradiation on lead sulfide quantum dots embedded in polyvinyl alcohol

Abstract

The present study compares structural and optical modifications of lead sulfide (PbS) quantum dots under swift heavy ion (SHI) irradiation. PbS quantum dots are prepared following an inexpensive chemical route using polyvinyl alcohol as the dielectric host matrix. SHI irradiation of the samples is carried out with 100 MeV Si⁷⁺ ion beam with fluences in the range from 1×10¹¹ to 3×10¹³ ions cm⁻² and their structural and optical properties, before and after irradiation, are compared by X-ray diffraction (XRD), photoluminescence (PL) and UV–Vis spectroscopy. The structural parameters of PbS quantum dots are studied by X-ray line profile analysis using the Williamson–Hall plot. The values of average crystallite sizes are found to vary from 8 to 18 nm. XRD studies confirmed the formation of the cubic nanocrystalline PbS. Improvement of crystalline quality for lower fluences is exhibited by an increase in the X-ray intensities of the films. The UV–Vis absorption spectra reveal blue shift relative to the bulk material. Size enhancement of PbS quantum dots after irradiation has been indicated in XRD line profiles of the samples which has also been supported by optical absorption spectra. PL studies of all the samples are carried out with excitation wavelength 350 nm. A broad PL emission with peak centered at 473 nm is observed in pristine as well as all the irradiated samples. PL study also shows that PL intensity increases with ion fluences.

Keywords:

• quantum dots
• SHI
• XRD
• W–H plot
• PL

Acknowledgements

The authors are thankful to IUAC, New Delhi, for providing the ion irradiation facility to carry out this work and Dr. P.K. Kulriya for experimental help during characterization. N.C. thanks the University Grants Commission, New Delhi, India, for awarding the FDP fellowship.