Abstract
One-dimensional ZnO nanostructures (nanowires/nanorods) are attractive materials for applications such as gas sensors, biosensors, solar cells, and photocatalysts. This is due to the relatively easy production process of these kinds of nanostructures with excellent charge carrier transport properties and high crystalline quality. In this work, we review the photoluminescence (PL) properties of single and collective ZnO nanowires and nanorods. As different growth techniques were obtained for the presented samples, a brief review of two popular growth methods, vapor-liquid-solid (VLS) and hydrothermal, is shown. Then, a discussion of the emission process and characteristics of the near-band edge excitonic emission (NBE) and deep-level emission (DLE) bands is presented. Their respective contribution to the total emission of the nanostructure is discussed using the spatial information distribution obtained by scanning transmission electron microscopy−cathodoluminescence (STEM-CL) measurements. Also, the influence of surface effects on the photoluminescence of ZnO nanowires, as well as the temperature dependence, is briefly discussed for both ultraviolet and visible emissions. Finally, we present a discussion of the size reduction effects of the two main photoluminescent bands of ZnO. For a wide emission (near ultra-violet and visible), which has sometimes been attributed to different origins, we present a summary of the different native point defects or trap centers in ZnO as a cause for the different deep-level emission bands.
Highlights
Similar to many binary compounds, zinc oxide (ZnO) has been widely used in the last century in a large number of daily applications such as cosmetics (UV screening), antibacterial applications, pigments, catalysts, piezoelectric transducers, and so on [1]
For a wide emission, which has sometimes been attributed to different origins, we present a summary of the different native point defects or trap centers in ZnO as a cause for the different deep-level emission bands
As the scientific community has focused so much attention on the synthesis and applications of semiconductor nanostructures, in the last few decades, ZnO nanostructures have gained much popularity due to their belonging to the rich family of possible nanostructures with tunable morphology and properties [2]
Summary
Similar to many binary compounds, zinc oxide (ZnO) has been widely used in the last century in a large number of daily applications such as cosmetics (UV screening), antibacterial applications, pigments, catalysts, piezoelectric transducers, and so on [1]. The literature on ZnO 1D nanostructures is vast; there are many reviews describing the different synthesis methods [34,35], optical [36] and electrical [37] properties, and practical applications of ZnO nanowires [38,39] and nanorods [40], including photocatalyst material [41], sensing platforms (chemical [42] and biological [43,44]), antibacterial element [45], light emissions sources(LEDs [46] and lasers [47]), dye-sensitized or thin film solar cells [48], field effect transistors [49], and piezoelectric nanogenerators [50]. The total chamber pressure, partial oxygen pressure, catalyst thickness, and the growth temperature are the most critical parameters of the process [4]
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