Myung Sub Kim

Effect of AZO seed layer on electrochemical growth and optical properties of ZnO nanorod arrays on ITO glass

We report the structural and optical properties of ZnO nanorod arrays (NRAs) grown by an electrochemical deposition process. The ZnO NRAs were grown on indium tin oxide (ITO) coated glass substrates with a thin sputtered Al-doped ZnO (AZO) seed layer and compared with ones directly grown without the seed layer. The growth condition dependence of ZnO NRAs was investigated for various synthetic parameters. The morphology and density of the ZnO NRAs were accordingly controlled by means of zinc nitrate concentration and growth time. From photoluminescence results, the ultraviolet emission was significantly enhanced after thermal treatment. For ZnO NRAs grown on ITO glass without the seed layer, the diffuse transmittance was enhanced despite the reduction in the total transmittance, indicating a high haze value. By using a thin AZO seed layer, the well-aligned ZnO NRAs on AZO/ITO glass are controllably and reproducibly synthesized by varying the growth parameters, exhibiting a total transmittance higher than 91% in the visible wavelength range as well as good optical and crystal quality.

Well-integrated ZnO nanorod arrays on conductive textiles by electrochemical synthesis and their physical properties

We reported well-integrated zinc oxide (ZnO) nanorod arrays (NRAs) on conductive textiles (CTs) and their structural and optical properties. The integrated ZnO NRAs were synthesized by cathodic electrochemical deposition on the ZnO seed layer-coated CT substrate in ultrasonic bath. The ZnO NRAs were regularly and densely grown as well as vertically aligned on the overall surface of CT substrate, in comparison with the grown ZnO NRAs without ZnO seed layer or ultrasonication. Additionally, their morphologies and sizes can be efficiently controlled by changing the external cathodic voltage between the ZnO seed-coated CT substrate and the counter electrode. At an external cathodic voltage of −2 V, the photoluminescence property of ZnO NRAs was optimized with good crystallinity and high density.

Light-Extraction Enhancement of Large-Area GaN-Based LEDs With Electrochemically Grown ZnO Nanorod Arrays

We reported the improvement in light-extraction efficiency of large-area InGaN/GaN blue light-emitting diodes (LEDs) with zinc oxide (ZnO) nanorod arrays (NRAs), together with theoretical analysis. The ZnO NRAs with high transmittance were grown on the indium-tin-oxide surface with a thin Al-doped ZnO seed layer by electrochemical deposition. The vertically well-aligned ZnO NRAs exhibited an excellent suppression of internal reflections as well as a good transmittance. For LEDs with optimized ZnO NRAs, the light output power was improved by ~20% at 350 mA compared to that of the conventional LED.

Structural and optical properties of ZnO nanorods by electrochemical growth using multi-walled carbon nanotube-composed seed layers

We reported the enhancement of the structural and optical properties of electrochemically synthesized zinc oxide [ZnO] nanorod arrays [NRAs] using the multi-walled carbon nanotube [MWCNT]-composed seed layers, which were formed by spin-coating the aqueous seed solution containing MWCNTs on the indium tin oxide-coated glass substrate. The MWCNT-composed seed layer served as the efficient nucleation surface as well as the film with better electrical conductivity, thus leading to a more uniform high-density ZnO NRAs with an improved crystal quality during the electrochemical deposition process. For ZnO NRAs grown on the seed layer containing MWCNTs (2 wt.%), the photoluminescence peak intensity of the near-band-edge emission at a wavelength of approximately 375 nm was enhanced by 2.8 times compared with that of the ZnO nanorods grown without the seed layer due to the high crystallinity of ZnO NRAs and the surface plasmon-meditated emission enhancement by MWCNTs. The effect of the MWCNT-composed seed layer on the surface wettability was also investigated.PACS: 81.07.-b; 81.16.-c; 81.07.Pr; 61.48.De.

Improved light extraction of InGaN/GaN blue LEDs by GaOOH NRAs using a thin ATO seed layer.

We investigated the effect of gallium oxide hydroxide (GaOOH) nanorod arrays (NRAs) on the light extraction of InGaN/GaN multiple quantum well blue light-emitting diodes (LEDs). GaOOH NRAs were prepared on an indium tin oxide electrode (ITO) layer of LEDs by electrochemical deposition method. The GaOOH NRAs with preferred orientations were grown on the ITO surface by sputtering a thin antimony-doped tin oxide seed layer, which enhances heterogeneous reactions. Surface density and coverage were also efficiently controlled by the different growth voltages. For LEDs with GaOOH NRAs grown at −2 V, the light output power was increased by 22% without suffering from any serious electrical degradation and wavelength shift as compared with conventional LEDs.

Enhanced Light Extraction of GaN-Based Green Light-Emitting Diodes With GaOOH Rods

We reported the enhanced light extraction efficiency in InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) with gallium oxide hydroxide (GaOOH) rods. The GaOOH rods were prepared by an aqueous gallium nitrate solution at 80°C and then coated on the surface of indium tin oxide electrodes of LEDs by a simple drop coating process. The synthesized GaOOH rods indicated a rhombus-shaped rod structure with average lengths of 2 μm and lateral dimensions of 50-500 nm. For LEDs with GaOOH rods, the light output powers were increased by 24.3% and 26.4% compared to the conventional LED on patterned sapphire substrate at 20 mA and 100 mA, respectively. Also, there was no distinct degradation in electrical characteristics of LEDs with GaOOH rods.