Structure and photoluminescence studies on ZnS:Mn nanoparticles

Abstract

ZnS:Mn was produced in nanocrystalline form by a chemical method using polyvinylpyroledone as a chemical capping agent. Mn was stoichiometrically substituted for Zn in ZnS. The manganese (Mn) concentration was varied over its whole solid solution limit in ZnS, i.e., from 0 to 40%. In the high concentration regime this material formed may be thus written as nanocrystalline (Zn, Mn)S. The material formed is thus a wide gap diluted magnetic semiconductor. The characterized material was in powder form. X-ray diffraction was used to estimate the crystallite size and to confirm formation of the material in single phase. The average crystallite size obtained was about 2 nm. The material remained cubic over the whole Mn solid solution range. The room temperature photoluminescence (PL) when deconvoluted using a Gaussian fit showed two extra peaks in nanocrystalline ZnS:Mn when compared to pure nanocrystalline ZnS, which had only two peaks. Mn incorporation significantly enhanced the PL intensity in nanocrystalline ZnS:Mn (400–850 nm range) thereby suggesting Mn2+ induced PL. The red shift of the two new peaks with increase in Mn2+ concentration can be attributed to the change in band structure due to the formation of ZnS:Mn alloy. These extra peaks were due to (a) various Mn2+ transitions in the ZnS host, (b) related to S as the nearest neighbor of Mn2+ ion in the nanocrystallite (due to the high concentration of Mn2+), or (c) Mn–Mn interactions at high Mn concentrations. However, our prepared pure MnS samples did not show any photoluminescence at room temperature. So it is concluded that the observed PL is Mn2+ induced in the nanocrystalline ZnS host.

Improved Optical Properties of Sulphide based Core/Shell Nanostructures

“…The appearance of a strong blue emission at around 419 nm is attributed to the presence of sulphur vacancies in the lattice [2,23]. Similar results are reported by Namrata et al [24].…”

“…In the PL process, an electron from the ZnS valence band is excited across the band gap and the photoexcited electron subsequently decays by a normal recombination process to some surface or defect states [2].…”

“…Nanoscale semiconductor materials doped with impurities as activators have been the subject of an extensive research interest in recent years due to their applications for a variety of commercial devices [2][3][4][5][6]. As one of well-known II-VI compound semiconductors, ZnS is particularly suitable for use as a luminescent host material for a variety of dopants due to its wide band gap energy at room temperature [7].…”

Controlled synthesis of Eu2+ and Eu3+ doped ZnS quantum dots and their photovoltaic and magnetic properties

“…7,33 Eu 3+ ions generally produce characteristic luminescence due to the transition from the excited energy level 5 D 0 to the 7 F levels of their 4f 6 electronic configuration. Three sharp emission peaks at 591 nm, 616 nm, and 700 nm, which correspond to the 5 For ZnS:Eu 2+ QDs, its PL spectrum shows a broadband emission at 512 nm, which is due to the 4f 6 5d 1 -4f 7 transition of the Eu 2+ ions. This emission band is not observed in bulk ZnS:Eu 2+ .…”

“…[1][2][3][4] ZnS is a ubiquitous semiconductor that has been studied widely as an important phosphor for optoelectronic and energy applications due to its better chemical stability and environmental friendliness compared to other chalcogenides. 5,6 On the other hand, ZnS's wide band gap limits its use as a sensitizer in quantum dot sensitized PV solar cells.…”