Effective way to control the size of well-aligned ZnO nanorod arrays with two-step chemical bath deposition

Abstract

The diameter of well-aligned ZnO nanorod arrays (ZNAs) grown on Si substrates has been well controlled from 150nm to 40nm by two-step chemical bath deposition method (CBD), i.e. substrate pretreatment with spin coating to form ZnO nanoparticles seed layer and CBD growth. The effects of ZnO nanoparticles density and diameter on size and alignment of ZNAs were investigated in detail by atomic force microscope (AFM), X-ray diffraction (XRD), scan electronic microscope (SEM), transmission electron microscope (TEM) and photoluminescence (PL). The results indicate that both diameter and density of ZnO nanoparticles which were pre-coated on the substrates will influence the size and alignment of ZNAs, but the density will play a key role to determine the diameter of ZNAs when the density is higher than the value of 2.3×10 8 cm -2 . Moreover, only a strong UV peak at 385 nm appears in room temperature PL spectrum for these samples, which indicates that as-synthesized ZnO nanorods have a perfect crystallization and low density of deep level defects.

Indirect optical transition due to surface band bending in ZnO nanotubes

“…The details on controlling the size of ZNRs through manipulating seeding layer can be found in our earlier report. 24,25 So the average defect concentration in both of them should be similar. Thus we can conclude that the defect concentration is not the main factor to influence the etching process, supporting the conclusion that the diameter plays an important role when ZNRs were converted into ZNTs.…”

“…Among these methods, we prefer the simple chemical etching process to convert the ZnO nanorods ͑ZNRs͒ into ZNTs. One reason is that our technique to control the growth of ZNRs is already mature, 24,25 which can provide the precursor with appropriate size and good crystal quality for the conversion of ZNTs. The other reason is that previously we have not only already investigated the optical properties of ZNRs in detail but also optimized their optical properties by effectively suppressing the surface recombination.…”

Origin of the surface recombination centers in ZnO nanorods arrays by X-ray photoelectron spectroscopy

“…a substrate treatment prior to the ZNAs and some other controllable growth conditions can be found elsewhere [21][22][23][24].…”

“…Recently, we successfully controlled the size of well-aligned ZnO nanorod arrays (ZNAs) from 40nm to 150nm with the two-step chemical bath deposition (CBD) method [21,22], i.e. by first spin coating the substrate with a seed layer of ZnO nanoparticles and then using the CBD growth.…”

Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process

“…a substrate treatment prior to the CBD growth. [12][13]. But in our case, the only difference between two asgrown ZnO nanorods arrays during the growth processes is that the beaker is sealed or Scanning electron microscopy (SEM) pictures were recorded by using a JEOL JSM-6301F.…”