Position and density control in hydrothermal growth of ZnO nanorod arrays through pre-formed micro/nanodots

Abstract

Position- and density-controlled ZnO nanorod arrays (ZNAs) were successfully grown on a Si substrate through a low temperature (90 °C) hydrothermal approach assisted by pre-formed ZnO micro/nanodots. The ZnO dots on Si substrates were prepared by a spin-coating technique, through which the pattern and density of the dots could be easily changed. Accordingly, the position- and density-controlled growth of ZNAs was achieved. For the resulting density-controlled ZNAs, the density could range from (5.6 ± 0.01) × 10(2) to (1.2 ± 0.01) × 10(2) rods µm(-2). The room-temperature photoluminescence (PL) spectrum of ZNAs exhibited excellent UV emission. The water wettability measurements of the ZNAs with different density showed good hydrophobicity, and the ZNAs with the lowest density revealed a superhydrophobic characteristic with a water contact angle of 166.1°.

Synthesis of Mg(OH)2 micro/nano flowers at room temperature

“…This process can then lead to a heterogeneous nucleation stage conducive for most corroborative localized crystal growth [28] at an optimum number of dipping times, e.g., 30 dippings. When this scenario prevails, some of the nuclei may coalesce to form the platelet structures (Fig.…”

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…The seed layer can be prepared in a number of ways. Sputtering of bulk materials and spin coating of colloidal quantum dots are the two most commonly used methods [100][101][102]. During the growth, ZnO nanowires preferentially nucleate from the cup tip near the grain boundaries between two adjacent grains in the ZnO seed film [103].…”

“…If the seed layer was prepared by spin coating of colloidal dots, controlling the spin speed enabled control of the density of the colloidal dots on the substrate. By tuning the spin speed from 4000 to 8000 r/min, the dot density changed from (1.8 ± 0.03) × 10 3 to (1.8 ± 0.03) × 10 2 dots/μm 2 , and consequently the ZnO nanowire array density varied from (5.6 ± 0.01) × 10 2 to (1.2 ± 0.01) × 10 2 nanowires/μm 2 [101]. Besides controlling the seed density, diffusion obstacle layers have also been applied to the ZnO seed layer in order to control the nanowire density [113].…”

“…Wettability is governed by the material surface chemistry and also the geometrical structure of the surface [304,328]. An as-grown ZnO nanowire array with appropriate density is a rather porous structure and exposes mostly the low energy non-polar side surfaces [101], which greatly enhances the hydrophobic behavior. Under UV irradiation, ZnO nanowires generate electron and hole pairs, and the holes can free the negatively charged [325].…”

Room temperature synthesis of ZnO nanoflowers on Si substrate via seed-layer assisted solution route

“…Therefore, homogeneous nucleation in this solution becomes very difficult [26]. The existence of the ZnO seed-layer can effectively lower the nucleation energy barrier, so it is able to afford heterogeneous nucleation for crystal growth [27]. The 500 • C calcined seed-layer is an ultrathin, continuous and homogeneous film which is composed of many small crystalline grains.…”