Correlation between structural and electronic order–disorder effects and optical properties in ZnO nanocrystals

Abstract

The correlation between structural and electronic order-disorder effects in understanding the optical properties of flower-like ZnO nanocrystals synthesized by the microwave-assisted hydrothermal method at low temperatures and short times is discussed. Theoretical simulations were performed at the density functional theory level to gain a better understanding of the experimental data from X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), electron paramagnetic resonance (EPR), ultraviolet-visible diffuse reflectance (UV-vis) spectroscopy and photoluminescence (PL) measurement studies at different temperatures. The decrease in band gap values is due to the presence of intermediate states above the conduction band. These discrete levels are formed by structural and electronic disorder of tetrahedral [ZnO 4 ] clusters which enhance the electron-hole pair.

A large red-shift in the photoluminescence emission of Mg 1−x Sr x TiO 3

“…Structural and electronic order-disorder effects in semiconductor materials have a major influence on the optical properties [7][8][9]25,26]. PL is an interesting technique for probing certain structural aspects to provide information at the short-and medium-range, where the degree of the local order is such that structurally inequitable sites can be distinguished by their different types of electronic transitions and are linked to a specific structural arrangement [26,27]. In this context, Longo and co-workers offered an explanation based on the Kröger-Vink notation to explain the vacancy formation in perovskite oxide materials [25].…”

Mechanism of photoluminescence in intrinsically disordered CaZrO3 crystals: First principles modeling of the excited electronic states

“…The overall result is that the unit cell deforms and the structure is no longer cubic but of reduced symmetry, such as orthorhombic, rhombohedral, tetragonal, monoclinic, and triclinic phases, depending on the details of the [BO6] octahedral rotations and B-site distortions. This influences the electronic and optical properties of materials, behavior of photo-generated charge carriers, including excitation, transfer, and redox reactions, and plays an important role in their technological applications [6,17,[26][27][28][29][30]. It should be realised that the absorption transition of the [BO6] cluster corresponds to an electron transition from a bonding to a nonbonding molecular orbital, i.e.…”

“…In particular, our group is involved in a research project on binary and complex metal oxides as potential alternatives to traditional metal activator based phosphors, because of their advantages of low toxicity, stability, tunable emission color, and low cost. These oxides include TiO2 [5], ZnO [6], ZnS [7], SnO2 [8], molybdates [9][10][11], and tungstates [12,13]. Among the numerous types of perovskite materials (ABO3), alkaline earth metal perovskite oxides are a veritable gold mine of diverse physical and chemical properties with large technological applications [14][15][16][17][18][19][20][21] based on ferroelectricity, piezoelectricity, non-linear optical behavior, and PL emissions, that that arise from the absence of inversion symmetry in a crystal structure [22].…”

The interplay between morphology and photocatalytic activity in ZnO and N-doped ZnO crystals

“…Zinc oxide (ZnO) is an important n-type semiconductor with a broad range of electric, gas sensing and photocatalytic properties with a band gap of 3.2 eV [1][2][3][4][5][6]. Therefore, many efforts have been made to synthesize ZnO-based semiconductors with different morphologies for specific devices, such as nanorods, nanobelts, nanosheets, microrod/microtube arrays, quantum dots and other complex hierarchical micro/nanostructures [7,8].…”

“…Therefore, many efforts have been made to synthesize ZnO-based semiconductors with different morphologies for specific devices, such as nanorods, nanobelts, nanosheets, microrod/microtube arrays, quantum dots and other complex hierarchical micro/nanostructures [7,8]. Synthetic routes to ZnO nanoparticles include modified polymeric precursor (MPP) [9], sputtering [10,11], hydrothermal [12], solvothermal [13,14], sol-gel [15,16], ultrasonic irradiation [17], microwave-assisted hydrothermal (MAH) [6,18,19], and zinc-precursor thermal decomposition with free-solvent [20,21] methods. The MPP method is one of the most common chemical synthesis of inorganic semiconductor materials due to its simplicity and low cost.…”