Induced Photonic Response of ZnO Nanorods Grown on Oxygen Plasma-Treated Seed Crystallites

Abstract

We examined the influence of O2 plasma treatment for the ZnO seed layer (SL) crystallites on the material characteristics of ZnO nanorods (NRs) synthesized by the hydrothermal method. Diode photocurrent and photo-response transient characteristics of the p-Si/n-ZnO-NR heterojunction-based ultraviolet (UV) photodetectors were also examined according to the plasma treatment for the SLs. The superior optical properties of NRs were measured from the photoluminescence by exhibiting 4.6 times greater near-band edge emission when grown on the O2-plasma-treated SL. The degree of (002) orientation of the NR crystals was improved from 0.67 to 0.95, as revealed by X-ray diffraction analysis, and a higher NR surface density of ~80 rods/μm2 with a smaller mean diameter of 65 nm were also observed by the SL modification using plasma-treatment. It was shown by X-ray photo-electron spectroscopy that this improvement of NR crystalline quality was due to the recovery of stoichiometric oxygen with significant reduction of oxygenated impurities in the SL crystals and the subsequent low-energy growth mode for the NRs. UV PDs fabricated by the proposed SL plasma treatment technique showed significantly enhanced UV-to-dark current ratio from 2.0 to 83.7 at a forward bias of +5 V and faster photo-response characteristics showing the reduction in recovery time from 16 s to 9 s.

Ultraviolet Photodetection Based on High-Performance Co-Plus-Ni Doped ZnO Nanorods Grown by Hydrothermal Method on Transparent Plastic Substrate

“…Explicit Zn doublet peaks were highlighted as Zn-2p 3/2 (~1020.8 ± 0.1 eV) and Zn-2p 1/2 (~1044.1 ± 0.1 eV) [see Figure 5 a]. Symmetrical outlines of the observed photoemission peaks, their positions, and spin orbital splitting level at ~23.3 eV of the Zn-2p doublet substantiate the factual presence of Zn 2+ chemical state in the stoichiometry of ZnO matrix [ 39 ]. Shown in Figure 5 b,c are the collected photoemission peaks from Co-2p and Ni-2p core levels, respectively.…”

“…The broadband spectral emissions in visible range of 400–760 nm are known to be associated with deep-level emissions (DLEs) caused by the recombination of photo-excited carriers from various categories of intrinsic defects in the crystals. The exact location of these defects and the theoretical judgment of their nature have been still controversial and did not come to a final conclusion [ 38 , 39 ]; however, it will be unavoidable to have various types of intrinsic defects in the ZnO nano-crystals grown as in this work which were synthesized by a solution method at low temperature. Many different residual organic constituents present in growth solution can be incorporated into the growing NR crystals, and they can lead to deep-level defects.…”

“…In the spectra of C-1s, the first peak of C-C was observed at ~284.6 eV, and the second peak from COOH or COOR was measured at ~288.6 eV. Clear reduction in unwanted carbon impurities after TM dopings can be attributed to the reduced formation of carboxyl groups or oxygenated hydrocarbons caused by the bonding of OH - with carbon oxides, as more reduction in carbon impurity was observed after doping in ZnO nanocrystals with the reduction of OH - and the recovery of stoichiometric oxygen [ 39 ]. It can be also postulated that the external TM dopant precursors suppressed the incorporation of carbon impurities into the ZnO crystals by changing the reaction kinetics of carbon complex formation in the solution [ 48 ].…”

Ultraviolet Photodetecting and Plasmon-to-Electric Conversion of Controlled Inkjet-Printing Thin-Film Transistors

“…For the reasons stated above, a high-quality ZnO oxide channel film can be improved by solution deposition followed by a simple processing of O 2 plasma treatment. Moreover, solution-based deposition followed by an O 2 plasma treatment could be a desirable method of a low-temperature technique for manufacturing high-performance TFT device [34][35][36][37]. To comprehensively investigate the electrical characteristics of the ZnO-based TFTs after the O 2 plasma treatment on the semiconducting ZnO channel film in TFTs, the typical output characteristics of the drain current-gate voltage (I DS -V GS ) curves are shown in Figure 3c (green line).…”

Effects of Different Oxidation Degrees of Graphene Oxide on P-Type and N-Type Si Heterojunction Photodetectors

“…Heterojunction photodetectors combine two types of materials for light detection, and Si is the optimal choice for one of the two materials due to mature and cheap Si complementary metal–oxide–semiconductor (CMOS) technology with Si acting as the substrate [ 1 , 2 , 3 ]. Numerous materials have been investigated to be combined with the Si substrate in heterojunction photodetectors for the optimization of photodetector applications, and studies increasingly concentrate on graphene-based materials [ 4 ].…”