Density Of ZnO Nanorod Arrays Research Articles

Field Emission Properties of Molybdenum Nanoparticles Decorated ZnO Nanorod Arrays.

Precisely controlled dimensions of heterostructured ZnO nanorod arrays were grown on micropatterned Au films supported by Si substrate using chemical vapor deposition (CVD). The field emission properties were attributed to pointed nanorods, thickness of catalyst, preferential growth, density, morphology of ZnO and Molybdenum (Mo) decorated ZnO nanorod arrays (Mo/ZnO). The selective restrained heterostructure approach resulted in excellent control over periodicity, location and density of ZnO nanorod arrays. Overall, field emission properties of bare ZnO nanorod arrays showed a low turn-on field of ~4.7 V/μm and a high field enhancement factor (β) ~1686 to 7.3 V/μm and (β) ~807 for Mo/ZnO. It was also found that the field emission properties were significantly influenced by densely decorated Mo nanoparticles on as-grown ZnO nanorod arrays.

Large-scale growth of density-tunable aligned ZnO nanorods arrays on GaN QDs

An effective approach for growing large-scale, uniformly aligned ZnO nanorods arrays is demonstrated. The synthesis uses a GaN quantum dot (QD) template produced by a self-assembled Stranski–Krastanow mode in metal organic chemical vapor deposition, which serves as a nucleation site for ZnO owing to the QD’s high surface free energy. The resultant ZnO nanorods with uniform shape and length align vertically on the template, while their density is easily tunable by adjusting the density of GaN QDs, which can be adjusted by simply varying growth interruption. By controlling the density of ZnO nanorod arrays, their optical performance can also be improved. This approach opens the possibility of combining one-dimensional (1D) with 0D nanostructures for applications in sensor arrays, piezoelectric antenna arrays, optoelectronic devices, and interconnects.

Controllable electrodeposition of ZnO nanorod arrays on flexible stainless steel mesh substrate for photocatalytic degradation of Rhodamine B

Well-aligned single-crystalline ZnO nanorod arrays (ZNRAs) were prepared on flexible stainless steel mesh (SSM) substrate in large-scale by using a direct electrodeposition method. The effects of electrochemical parameters, such as applied potential, applied nucleation potential time, substrate pretreatment, electrodeposition duration and times, on the orientation, morphology and density of ZNRAs were systematically studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED). The results showed that ZNRAs on SSM substrate with [001] preferred orientation and well crystallization were obtained by controlling the applied potential in the range of −0.9 to −1.1V. The density of ZNRAs could be increased obviously by applying a nucleation potential (−1.3V for more than 10s before deposition) or by means of substrate pretreatment (the SSM immersed in zinc acetate colloid for more than 10min before deposition), meanwhile, the deposited ZNRAs also had small average diameter (<46±4nm), narrow size distribution and good orientation. In addition, it was also found that the average diameter of ZNRAs could be increased from 89 to 201±5nm by extending the electrodeposition duration from 1800 to 7200s, and the length of rods was from 0.8 to 2.2±0.1μm when the times of the electrodeposition from one to six times. Furthermore, the band gap energy (Eg) of as-prepared ZNTAs was not closely related to the electrodeposition times (only changed from 3.30 to 3.32eV). The ZNRAs prepared with more electrodeposition times showed enhanced photocatalytic performance under the UV-lamp for degradation of Rhodamine B. The degradation efficiency of ZNRAs improved from 89.4% to 98.3% with the deposition times from one to six times.

Selective growth and characterization of ZnO nanorods assembled a hexagonal pattern on H2-decomposed GaN epilayer

This paper reported a simple and effective method for fabricating and patterning highly ordered ZnO nanorod arrays on H2-decomposed GaN epilayer via hydrothermal route. The edge of pattern, which has been decomposed by H2 flow, provides appropriate nucleation sites for the selective-growth of aligned ZnO nanorods. The density of ZnO nanorod arrays assembled the hexagonal pattern can be tuned by varying the solution concentrations, growth time and reaction temperatures. The results have demonstrated that the ZnO nanorods are highly uniform in diameter and height with perfect alignment and are epitaxially grown along [0001] direction. This work provides a novel and accessible route to prepare oriented and aligned ZnO nanorod arrays pattern. And the aligned ZnO nanorods form an ideal hexagonal pattern that might be used in many potential applications of ZnO nanomaterials.

Density Control of ZnO Nanorod Arrays on Mixed Self-Assembled Monolayers

We demonstrate the feasibility of controlling the density of ZnO nanorod arrays by using mixed self-assembled monolayers (SAMs) composed of molecules with hydrophobic methyl end groups and hydrophi...

Low-Temperature Growth of Surface-Architecture-Controlled ZnO Nanorods on Si Substrates

ZnO nanorod arrays with controlled diameter and density were synthesized on Si substrate with thereon two-dimensional periodic polymer aperture arrays at low temperature. A sharp size and density variation of ZnO nanorod arrays with the size of aperture was observed. Surprisingly, the diameter of the ZnO nanorod was larger than the opening of the aperture when the aperture size was smaller than 300 nm. Besides, as the aperture size increased, the diameter of ZnO nanorod decreased and the density of ZnO nanorod arrays increased. It was also observed that the ZnO nanorods were not grown directly through the aperture template. The detailed growth behavior was characterized and analyzed. This growth phenomenon of ZnO nanorods offers a capability to control the formation of single/multiple ZnO nanorod(s) with both size and density onto random substrates for potential optoelectronics applications.

Effect of Aspect Ratio on Field Emission Properties of ZnO Nanorod Arrays.

ZnO nanorod arrays are prepared on a silicon wafer through a multi-step hydrothermal process. The aspect ratios and densities of the ZnO nanorod arrays are controlled by adjusting the reaction times and concentrations of solution. The investigation of field emission properties of ZnO nanorod arrays revealed a strong dependency on the aspect ratio and their density. The aspect ratio and spacing of ZnO nanorod arrays are 39 and 167 nm (sample C), respectively, to exhibit the best field emission properties. The turn-on field and threshold field of the nanorod arrays are 3.83 V/μm and 5.65 V/μm, respectively. Importantly, the sample C shows a highest enhancement of factorβ, which is 2612. The result shows that an optimum density and aspect ratio of ZnO nanorod arrays have high efficiency of field emission.

Controlled growth of ZnO nanorod templates and TiO2 nanotube arrays by using porous TiO2 film as mask

Porous TiO2 thin films obtained from sol–gel self-organize approach were firstly used as masks to control the growth of ZnO nanorod arrays by aqueous solution method. The effect of TiO2 pore size on the density of ZnO nanorod arrays was investigated by atomic force microscopy and field emission scanning electron microscope. The results show that the density of ZnO nanorod arrays obviously decreases after using porous TiO2 masks, and increases with increasing the TiO2 pore size. Additionally, the existence of TiO2 mask can also effectively prolong the wet-chemical etching time of TiO2 nanotube arrays manufactured from ZnO nanorod templates assisted sol–gel method, to completely remove the ZnO nanorod templates and to avoid collapsing of TiO2 nanotube arrays from the substrates.

Controlled selective growth of ZnO nanorod arrays and their field emission properties

Controlled, ordered arrays of ZnO nanorods having a high aspect ratio of∼30:1 anddiameter of ∼50 nm were fabricated on silicon substrates by combining electron-beam lithography and simplesolution growth techniques. This top-down and bottom-up hybrid approach resulted in excellentcontrol of periodicity, location, and density of ZnO nanorod arrays on silicon substrates. The fieldemission measurements from the as-grown ZnO nanorod arrays showed a low turn-on field of∼2.85 V µm−1 and a highfield-enhancement factor (β) of ∼1.68 × 103.