Photoluminescence phenomena prevailing in c-axis oriented intrinsic ZnO thin films prepared by RF magnetron sputtering

Abstract

The substantial amount of –OH groups attached to the Zn lattice has been correlated to the dominant c-axis orientation of the hexagonal ZnO crystals with wurtzite structure, which demonstrates two preferred first-order Raman peaks and also exhibits a distinct UV luminescence band due to the typical exciton emission or near-band-edge emission.

Optical and Structure Analysis of ZnO:Al Film

“…The exact origin of the defect emission band in ZnO is not well understood and has been the subject of various interpretations, such as oxygen vacancies, zinc interstices, Zn antisites, extrinsic impurities and complex defects (Bixia et al, 2001;Martins, 2012;Das and Mondal, 2014). Previous reports indicate that the radiative lifetime of ex-citons pure ZnO is in the nanosecond range, while in the visible range the lifetime of the emission is longer, i.e., in the range of microseconds, so this justifies the emission is stronger in the visible (Das and Mondal, 2014). However, the complex dependence of UV and visible emission intensities is still subject of controversy in the literature (Mohanta, 2014;Manzano et al, 2011;Khan et al, 2013).…”

“…The UV band emission is dominated by excitonic transitions (Bixia et al, 2001;Das and Mondal, 2014). According to Das and Mondal (2014) the appearance of the band around 3.35 eV is related to exciton emission or emission qua-si-band, that is, the photo-excited electrons recombine with holes in the valence band or traps near the valence band, considering that this is a value below the gap for pure ZnO.…”

“…According to Das and Mondal (2014), the visible PL emissions from pure ZnO films prepared by magnetron sputtering, correspond to a broadband coming from a convolution of different transitions that are related to the oxygen vacancy states, Zn interstitial, doubly ionized Zn vacancy and oxygen antisite.Due to the different assignments found to the sub-bands of the visible PL emission, it was not possible to attribute a single set of contributions to the observed signal. The difficulty in identifying the origins of emissions-related defects is due to the complexity of microscopic details involved (Das and Mondal, 2014).…”

“…The difficulty in identifying the origins of emissions-related defects is due to the complexity of microscopic details involved (Das and Mondal, 2014). So, we would rather let them generically attributed to the different kinds of defects, while the narrow UV bands were attributed to Two Electrons Satellites ( It is observed that the extinction coefficient for the doped and the undoped samples no more than 0.05 to the visible spectrum, with typical extinction coefficients of transparent films.…”

Synthesis, characterization and catalytic performance of ZnO–CeO2 nanoparticles in wet oxidation of wastewater containing chlorinated compounds

“…Zn 2p 3/2 spectra presented a peak at 1020.9, corresponding to the presence of Zn 2? in ZnO lattice (Das and Mondal 2014). O1s spectra exhibited three peaks.…”