Three-Dimensional Cross-Linked Arrays of Comb-Like ZnO: Epitaxial Growth and Modulation

The method to construct the three-dimensional (3D) ordered nanostructure of ZnO for improving its performance has attracted considerable attention and remains a challenging issue, which has theoretical and practical implications for nanoscale applications such as optoelectronics and gas sensors. Herein, we demonstrate a straightforward chemical vapor deposition (CVD) technique for the epitaxial growth of 3D cross-linked comb-like ZnO arrays on r-plane sapphire substrates. The morphological, structural, and optical properties of the as-synthesized samples were examined using X-ray diffraction, field emission scanning electron microscopy, field emission transmission electron microscopy, Raman spectroscopy, UV–vis spectroscopy, and photoluminescence spectroscopy. A cooperative growth mechanism is suggested to construct 3D cross-linked comb-like ZnO arrays: The supersaturated alloy forms a backbone of oblique nanosails along [101̅0] by the Au-assisted catalytic vapor–liquid–solid (VLS) growth mechanism and the inevitable vapor–solid (VS) lateral extension growth process; simultaneously discrete nanoteeth are grown along the unilateral c-direction [0001] by the Zn self-catalytic VLS mechanism, culminating in a 3D cross-linked array of comb-like ZnO. The development of such a unique 3D cross-linked array allows the exploration of performance in gas-sensitive devices, optoelectronics, and quantum electrical information applications

Integration of Nanoscale Light Emitters and Hyperbolic Metamaterials: An Efficient Platform for the Enhancement of Random Laser Action

Hyperbolic metamaterials have emerged as novel materials with exciting functionalities, especially for optoelectronic devices. Here, we provide the first attempt to integrate hyperbolic metamaterials with light emitting nanostructures, which enables to strongly enhance random laser action with reduced lasing threshold. Interestingly, the differential quantum efficiency can be enhanced by more than four times. The underlying mechanism can be interpreted well based on the fact that the high-<i>k</i> modes excited by hyperbolic metamaterials can greatly increase the possibility of forming close loops decreasing the energy consumption for the propagation of scattered photons in the matrix. In addition, out-coupled propagation of the high-<i>k</i> modes reaches to the far-field without being trapped inside the metamaterials due to the coupling with the random distribution of light emitting nanoparticles also plays an important role. Electromagnetic simulations derived from the finite-difference time-domain (FDTD) method are executed to support our interpretation. Realizing strong enhancement of laser action assisted by hyperbolic metamaterials provides an attractive, very simple and efficient scheme for the development of high performance optoelectronic devices, including phototransistors, and many other solid state lighting systems. Besides, because of increasing light absorption assisted by hyperbolic metamaterials structure, our approach shown is also useful for the application of highly efficient solar cells