Mi Jung

Enhancement of hole injection and electroluminescence by ordered Ag nanodot array on indium tin oxide anode in organic light emitting diode

We report the enhancement of hole injection and electroluminescence (EL) in an organic light emitting diode (OLED) with an ordered Ag nanodot array on indium-tin-oxide (ITO) anode. Until now, most researches have focused on the improved performance of OLEDs by plasmonic effects of metal nanoparticles due to the difficulty in fabricating metal nanodot arrays. A well-ordered Ag nanodot array is fabricated on the ITO anode of OLED using the nanoporous alumina as an evaporation mask. The OLED device with Ag nanodot arrays on the ITO anode shows higher current density and EL enhancement than the one without any nano-structure. These results suggest that the Ag nanodot array with the plasmonic effect has potential as one of attractive approaches to enhance the hole injection and EL in the application of the OLEDs.

Enhanced Light Extraction from Nanoporous Surfaces of InGaN/GaN-Based Light Emitting Diodes

The authors fabricated anodic alumina by a two-step anodization process for samples of an Al foil template and an Al deposited film in order to form nanopores on the p-GaN surfaces of InGaN/GaN multi-quantum-well (MQW) light-emitting diodes (LEDs). The GaN nanopores formed by nanopatterning with the alumina template in an inductively coupled plasma dry etching process shows enhanced light extraction at a wavelength of 450 nm. The nanoporous alumina anodized from the deposited Al layer has a channel to allow the flow of electrolytes into the GaN surface and results in the surface etching effect showing light enhancement at 474 nm. The significant enhancement of light extraction has been correlated with the nanoscaled roughness of a randomly distributed and nanoporous p-GaN surface.

Nanohole arrays with sub-30 nm diameter formed on GaAs using nanoporous alumina mask

Nanohole arrays with a sub-30 nm diameter were formed on GaAs substrates by inductively coupled plasma reactive-ion etching (ICP-RIE) using nanoporous alumina films as transfer masks. Whether the pore configurations of the alumina masks were transferred onto the GaAs substrates depended on the exposure time of ICP-RIE. In spite of the sub-30 nm pore diameter of the alumina masks, the ion bombardment induced in SiCl4/Ar gas by ICP-RIE properly responded on the GaAs substrate through the pores of the alumina masks. ICP-RIE using nanoporous alumina masks can be used as a prospective method to produce nanostructures.

Ag nanodot array as a platform for surface-enhanced Raman scattering

Well-ordered Ag nanodot array on indium-tin-oxide (ITO) glass is adopted as a sensor platform based on surface-enhanced Raman scattering (SERS). SERS has attracted extensive attention in the development of sensitive chemical or biological sensors due to its property of the amplification of electromagnetic fields on a metal nanostructure. The key issue for the applications of SERS is to secure the fabrication technique of a noble metal nanostructured surface. For an SERS-active surface with stability and reproducibility, a Ag nanodot array is fabricated on the ITO glass using a nanoporous alumina mask with uniform through holes. The signal intensity of SERS from methylene blue (MB) adsorbed on the Ag nanodot array showed much stronger scattering than the one from the Ag film of 50-nm thick. The SERS intensity on the Ag nanodot array is consistently enhanced by increased concentration of MB. These results confirm that the Ag nanodot array on ITO glass can be utilized as a stable platform for the sensitive detection of chemical materials based on SERS.

Enhanced Fabry–Perot Interferences from Nanoporous Surfaces of GaN Thin Films Patterned by Anodic Alumina Templates

The authors fabricated a nanoporous alumina template with an electrochemical anodization process and implemented this template as a mask for the nanopatterning process onto the GaN surface of an InGaN/GaN multi-quantum-well structure. The fabricated nanohole structure shows a locally ordered periodicity of a photonic crystal slab with an averaged hole distance of 105 nm and hole diameter of 60 nm. The nanohole array as a subwavelength grating shows an enhanced intensity peak at 454.8 nm with enhanced optical interference indicating the formation of subwavelength nanohole diffraction grating.

Effect of a nanoporous surface on photoluminescence from nanopatterned GaN thin films fabricated by anodic alumina templates

GaN photonic crystal slabs on InGaN/GaN multi-quantum well light-emitting diodes have been formed by dry etching using nanoporous anodic alumina templates, which have a periodic lattice constant of 105 nm and a hole diameter of 45 nm. The photonic crystal slab shows an enhanced intensity of photoluminescence due to the nanohole pattern array producing Fabry–Perot like interference. A rough surface of nanoholes results in a broad spectrum with a small oscillation, and well-ordered multiple facets of nanoholes results in a relatively sharp spectrum with a large oscillation.

Characteristics and fabrication of nanohole array on InP semiconductor substrate using nanoporous alumina

Uniform arrays of nano-sized pore produced in porous alumina were transferred into InP substrates by inductively coupled plasma reactive ion etching (ICP-RIE). We observed a significant enhancement in the light output from InP substrate with nanohole arrays on the surface. Photoluminescence intensity of triangular arrays of air cylinders on InP substrate showed an enhancement up to 3 times compared with that from a raw InP substrate without such structure. The ICP-RIE technique using nanoporous alumina mask can be used as a prospective method in the fabrication of nanostructure materials for increasing the light output from semiconductor light emitting devices.

Plasmonic properties of metal nanodot arrays with same diameter utilizing nanoporous alumina mask

Metal nanodot arrays with the uniform diameter were fabricated utilizing nanoporous alumina mask with through-holes as an evaporation mask. Ag, Cu, and Au nanodot arrays were fabricated on indium tin oxide coated glass as a replica of the nanoporous alumina mask. The localized surface plasmon resonance (LSPR) properties of metal nanodot arrays were experimentally measured by the ultraviolet-visible spectroscopy. The dependency of LSPR wavelength on nanodot composition was examined.

Fabrication of plasmonic materials via nanoporous alumina mask

Plasmonic materials have attracted considerable attention because of scientific interest and their potential applications. Using the nanoporous alumina mask as an evaporation mask, Ag nanodot array was directly formed on indium-tin-oxide glass. Its optical properties are studied.

Fabrication and optical properties of size-controlled Ag nanodot array via nanoporous alumina mask

Ag nanostructure has been widely used for optical sensing applications for localized surface plasmon resonance (LSPR). Many efforts have been tried to fabricate and control silver nanostructure. The pore diameter of the nanoporous alumina mask with through-holes was controlled by two-time dipping in 5 wt% phosphoric acid at 30°C. Using the nanoporous alumina mask as an evaporation mask, size-controlled Ag nanodot arrays were directly formed on indium-tin-oxide coated glass. With this process, Ag nanodot arrays with different size (42 nm, 60 nm, 80 nm) could be fabricated in periodic patterns with same separation distance of 105 nm. A large area Ag nanodot array was fabricated from the hard-won alumina mask. Their LSPR properties are examined by UV-vis extinction spectroscopy.