ZnO and MgZnO Nanocrystalline Flexible Films: Optical and Material Properties

Abstract

An emerging material for flexible UV applications isMgxZn1−xO which is capable of tunable bandgap and luminescence in the UV range of ~3.4 eV–7.4 eV depending on the compositionx. Studies on the optical and material characteristics of ZnO and Mg0.3Zn0.7O nanocrystalline flexible films are presented. The analysis indicates that the ZnO and Mg0.3Zn0.7O have bandgaps of 3.34 eV and 4.02 eV, respectively. The photoluminescence (PL) of the ZnO film was found to exhibit a structural defect-related emission at ~3.316 eV inherent to the nanocrystalline morphology. The PL of the Mg0.3Zn0.7O film exhibits two broad peaks at 3.38 eV and at 3.95 eV that are discussed in terms of the solubility limit of the ZnO-MgO alloy system. Additionally, external deformation of the film did not have a significant impact on its properties as indicated by the Raman LO-mode behavior, making these films attractive for UV flexible applications.

Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films

“…It is notable that these calculated values of the grain size are relatively smaller than those presented in the SEM images. A similar observation has been reported previously where the grain sizes calculated using XRD measurements was found to be smaller than the values revealed under SEM [17,18]. The underlying reasons for the smaller values of grain size estimated via XRD have been attributed to the presence of defects, and to the nature of the method itself [17,18].…”

“…A similar observation has been reported previously where the grain sizes calculated using XRD measurements was found to be smaller than the values revealed under SEM [17,18]. The underlying reasons for the smaller values of grain size estimated via XRD have been attributed to the presence of defects, and to the nature of the method itself [17,18]. Specifically, the XRD method provides preferential information about the size of the region with highly-coherent scattering; such scattering usually occurs in smaller regions [19].…”

Optical Properties of ZnO‐Alloyed Nanocrystalline Films

“…When the absorbance bandgap is not sharply defined, the usual method of extrapolation [20] may not render good results. To estimate the bandgap in such cases, transmission derivative procedures can be utilized, which were successfully used previously for the analysis of the bandgaps of Mg x Zn 1−x O and In x Ga 1−x N [6,[21][22][23]. In the following, we present the derivation of the method applicable to direct bandgap transitions.…”

“…Zinc oxide (ZnO) is a direct bandgap semiconductor with a bandgap of ∼3.37 eV at room temperature and relatively deep excitonic binding energy of 60 meV, both attributes of which make ZnO an efficient UV optical material at and above room temperature [1][2][3][4][5][6]. Due to their environmentally friendly chemical nature, resistivity to harsh environments, and deep excitonic level, ZnO as well as Mg x Zn 1−x O (where x is the composition) are emerging materials capable of highefficiency luminescence in a wide range of the ultraviolet (UV) spectrum [6][7][8].…”

High responsivity solar blind photodetector based on high Mg content MgZnO film grown via pulsed metal organic chemical vapor deposition

“…Nevertheless, researchers have continuously been improving epitaxial film growth techniques, including pulsed laser deposition (PLD), [10,12,15] molecular beam epitaxy (MBE) [16][17][18] and metal organic chemical vapor deposition (MOCVD) [19,20] to achieve successful growth of wurtzite MgZnO with a Mg content of up to 0.37 (4.28 eV) and cubic MgZnO with a Mg content exceeding 0.62 (5.40 eV). Alloys with a Mg composition between 0.37 and 0.62 have been found to be mixed phase material without a defined band gap thereby leading to a discontinuity in the band gap tailoring between 4.28 eV and 5.40 eV [12,21]. This missing band adversely affects possible UV detection applications as it covers a large portion of the solar blind spectral region.…”