Superior nanopatterns via adjustable nanoimprint lithography on aluminum oxide in high-K thin films with ultraviolet curable polymer.

The present study substantiate that ultraviolet-nanoimprint lithography (UV-NIL) can be used to transfer a one-dimensional nano-pattern onto a high-k thin film of aluminum oxide mixed with a UV photocuring agent. Polydimethylsiloxane (PDMS) molds fabricated on silicon wafers were made using deep ultraviolet laser interference lithography in order to investigate one-dimension nanopatterns. These imprinted nano-patterns induce geometric deformations in the liquid crystal (LC), creating collective and elastic properties, which act as a guide for homogeneous alignment. The nanoimprint method can process a large area, so it can be processed much easier, faster, and more accurately than the conventional rubbing method. Moreover, the optical properties of the nano-imprinted aluminum oxide (AlO) thin-film are about 1.5p% superior to that of conventional commercialized cells, so it has a high effect on the luminance and color gamut of the display. After pattern imprinting, atomic force microscope (AFM) was performed to confirm the result. We can compared the cycle of AlO mixed with UV photocuring agent PDMS pattern cycle, the period is 776 and 750 nm, the width is 468 and 450 nm, the spacing is 292 and 300 nm, and the height is 40 and 30 nm. The nano-imprinted film appears to replicate the width, amplitude, and spacing of the PDMS template. In addition, X-ray photoelectron spectroscopy was performed to determine the chemical properties of the thin film and it was confirmed that UV irradiation induces oxidation, thus increases the intensity significantly. The binding energies of Al 2p and C-O spectra were situated at 74.27 ± 0.5 eV and 531.78 ± 0.5 eV, respectively.

Facile and Scalable Fabrication of Flexible Reattachable Ionomer Nanopatterns by Continuous Multidimensional Nanoinscribing and Low-temperature Roll Imprinting.

We develop a facile route to the scalable fabrication of flexible reattachable ionomer nanopatterns (RAINs) by continuous nanoinscribing and low-temperature roll imprinting, which are repeatedly attachable to and detachable from arbitrarily shaped surfaces. First, by sequentially performing continuous nanoinscribing over a polymer substrate along the multiple directions, we readily create the multidimensional nanopattern, which otherwise demands complex nanofabrication. After its transfer to an elastomer pad for use as a soft nanoimprinting stamp, we then conduct a low-temperature roll imprinting of the ionomer film to fabricate a flexible and highly transparent RAIN. Reversible loosening of ionic units in the ionomer material at the mild temperature as low as ∼60-70 °C enables the faithful nanopatterning over thermosensitive organic compounds and fragile materials under a slight pressure. The excellent adhesion purely emerging from ionic interactions uniquely realizes the conformal attachability and clean detachability of RAINs for universal targets in ambient conditions, particularly beneficial for individual wearable and mobile devices requiring the user-specific "on/off" of the nanopattern-driven functionalities. As one vivid example, we demonstrate that a single light-emitting device can be switched from the focused pointer to the widespread flashlight depending on the RAIN application upon user's purpose.

Origin of Mechanoluminescence from Cu-Doped ZnS Particles Embedded in an Elastomer Film and Its Application in Flexible Electro-mechanoluminescent Lighting Devices.

Mechanically driven light emission from particles embedded in elastomer films has recently attracted interest as a strong candidate for next-generation light sources on display devices because it is nondestructive, reproducible, real-time, environmentally friendly, and reliable. The origin of mechanoluminescence (ML) obtained from particles embedded in elastomer films have been proposed as the trapping of drifting charge carriers in the presence of a piezoelectric field. However, in this study, we propose a new origin of ML through the study of the microstructure of a Cu-doped ZnS particles embedded in an elastomer composite film with high brightness using transmission electron microscopy (TEM) to clearly demonstrate the origin of ML with respect to the microstructure of ML composite films. The TEM characterization of the ML composite film demonstrated that the Cu-doped ZnS particles were fully encapsulated by a 500 nm thick Al layer, which acts as an electron source for ML emission. Furthermore, we fabricated a flexible electro-mechanoluminescence (EML) device using a Cu-doped ZnS particles embedded in a flexible elastomer composite film. Our research results on a new emission mechanism for ML and its application in flexible light generating elastomer films represent an important step toward environmentally benign and ecofriendly flexible electro-mechanoluminescent lighting devices.

Homogeneous liquid crystal alignment characteristics on solution-derived HfYGaO films treated with IB irradiation.

Solution-derived HfYGaO films have been treated by ion beam (IB) irradiation and used as liquid crystal (LC) alignment layers. Solution processing was adopted due to its simplicity, high throughput, and facile composition modification. Homogeneous and uniform LC alignment was achieved on the IB-irradiated HfYGaO films, and when these films were adopted in twisted nematic (TN) cells, electro-optical performance comparable to that of TN cells with conventional polyimide layers was achieved, with almost no capacitance-voltage hysteresis. Moreover, LC cells based on IB-irradiated HfYGaO films had a high thermal budget. The proposed IB-irradiated solution-derived HfYGaO films have considerable potential for use in advanced LC applications.

Effect of Oxygen on the Structural/Electrical Properties of NIZO Films on Transparent Flexible Substrates.

Thin film transparent oxides have attracted considerable attention over the last few decades for transparent electronic applications, such as flat panel displays, solar cells, touch-pads, and mobile devices. Metallic doped InZnO (IZO) films have been suggested for the transparent layer exhibiting semiconducting or metallic properties because of its controllable mobility and excellent electrical properties, but they show a degradation of the electrical performance under bending conditions. This study assessed Ni doped IZO (NIZO) films as a flexible transparent electrode on different flexible transparent substrates for flexible electronic applications. Thin NIZO films were deposited on cellulose, PES and glass substrates using a sputtering system with a single NIZO target (In2O3 73.8/ZnO 15.7/NiO 10.5 mol.%) at room temperature. During deposition of the NIZO films, the total flow rate of the carrier gas was maintained using a regulating system. The effects of the oxygen content in the carrier gas on the structural, electrical and optical properties of the thin films deposited on flexible substrates was characterized. The results highlight the feasibility of the transparent NIZO oxide layer on flexible substrates as a flexible electrode with a relatively high sheet resistance, which is strongly related to the crystallographic structure and oxygen content during the film deposition process.

Optical Properties of Hybrid Inorganic/Organic Thin Film Encapsulation Layers for Flexible Top-Emission Organic Light-Emitting Diodes.

Inorganic/organic hybrid thin film encapsulation layers consist of a thin Al2O3 layer together with polymer material. We have investigated optical properties of thin film encapsulation layers for top-emission flexible organic light-emitting diodes. The transmittance of hybrid thin film encapsulation layers and the electroluminescent spectrum of organic light-emitting diodes that were passivated by hybrid organic/inorganic thin film encapsulation layers were also examined as a function of the thickness of inorganic Al203 and monomer layers. The number of interference peaks, their intensity, and their positions in the visible range can be controlled by varying the thickness of inorganic Al2O3 layer. On the other hand, changing the thickness of monomer layer had a negligible effect on the optical properties. We also verified that there is a trade-off between transparency in the visible range and the permeation of water vapor in hybrid thin film encapsulation layers. As the number of dyads decreased, optical transparency improved while the water vapor permeation barrier was degraded. Our study suggests that, in top-emission organic light-emitting diodes, the thickness of each thin film encapsulation layer, in particular that of the inorganic layer, and the number of dyads should be controlled for highly efficient top-emission flexible organic light-emitting diodes.

Electro-optical switching of liquid crystals sandwiched between ion-beam-spurted graphene quantum dots-doped PEDOT:PSS composite layers.

Graphene quantum dots (GQDs)-doped PEDOT: PSS composite layers were utilized to align liquid crystals (LCs) via an ion-beam (IB)-spurting pre-treatment process. LCs were homogeneously aligned between sandwiched GQDs/ PEDOT: PSS composite thin layers, and the alignment of LCs was found to be affected by both the quantity of doped GQDs and IB-spurting intensity. Competitive electro-optical switching properties and non-residual DC performance of the cell equipped with GQDs/ PEDOT: PSS composite alignment layers were obtained because of the enhanced field effect and charge transport induced by doped GQDs. Notably, using IB-spurted GQDs/ PEDOT: PSS layers as alignment layers for next generation high-performance liquid crystal display (LCD) is promising.

Synthesis of TaZnO thin films using combinatorial magnetron sputtering and its electrical, structural and optical properties.

The structural, electrical, and optical properties of tantalium zinc oxide (TaZnO) thin films grown using combinatorial magnetron sputtering system were investigated. To explore the effects of film thickness and post annealing treatment on the properties of the films, we have fabricated TaZnO sample libraries having different thicknesses and carried out post annealing treatment. Sample libraries fabricated at room temperature showed the resistivity ranged 2.1 to approximately 7.1 x 10(-3) Omega cm, while the films post annealed at 200 degrees C under 1 mTorr exhibited the resistivity as low as 1.2 x 10(-3) Omega cm. XRD measurements revealed that the film structure was strongly depended on the film thickness, showing that the structure was changed from amorphous to polycrystalline with increasing the film thickness. Furthermore, it was found that figure of merit (0TC), which was determined by T% and Rs of the TaZnO films, showed maximum value as the films with a thickness of 230 nm was post-annealed at 200 degrees C under vacuum of 1 mTorr.

Thin transparent W-doped indium-zinc oxide (WIZO) layer on glass.

Annealing effect on structural and electrical properties of W-doped IZO (WIZO) films for thin film transistors (TFT) was studied under different process conditions. Thin WIZO films were deposited on glass substrates by RF magnetron co-sputtering technique using indium zinc oxide (10 wt.% ZnO-doped In2O3) and WO3 targets in room temperature. The post annealing temperature was executed from 200 degrees C to 500 degrees C under various O2/Ar ratios. We could not find any big difference from the surface observation of as grown films while it was found that the carrier density and sheet resistance of WIZO films were controlled by O2/Ar ratio and post annealing temperature. Furthermore, the crystallinity of WIZO film was changed as annealing temperature increased, resulting in amorphous structure at the annealing temperature of 200 degrees C, while clear In2O3 peak was observed for the annealed over 300 degrees C. The transmittance of as-grown films over 89% in visible range was obtained. As an active channel layer for TFT, it was found that the variation of resistivity, carrier density and mobility concentration of WIZO film decreased by annealing process.

Effect of zinc content on the refractive index of Co-sputtered Zn-doped ITO films.

In this study, we investigated the possibility of using Zn-doped ITO film as an alternative material for conventional SiO2 waveguides used in optical communication. The Zn-doped ITO films were deposited on quartz substrates using a combinatorial sputtering system, which yielded composition spread Zn-In-Sn-O (ZITO) films by co-sputtering two targets of ITO and ZnO. The Zn-doped ITO films deposited at room temperature exhibited an amorphous phase in the Zn content [Zn/(Zn+In+Sn)] range of 39-54 at%. The Zn-doped ITO films deposited at low oxygen partial pressure showed resistivity below 10(-3) ohms cm and optical transmittance of approximately 85% at 550 nm. The refractive index calculated by the Swanepoel method was found to be dependent on the Zn content in the Zn-doped ITO films. The calculated bending loss from the refractive index indicated that Zn-doped ITO could be utilized as a new waveguide material for various optical devices, such as optical splitters, wavelength division multiplexers (WDMs), optical modulators, and optical switches.

Decrease in work function of transparent conducting ZnO tin films by phosphorus ion implantation.

To confirm the possibility of engineering the work function of ZnO thin films, we have implanted phosphorus ions into ZnO thin films deposited by radio-frequency magnetron sputtering. The fabricated films show n-type characteristics. It is shown that the electrical and optical properties of those thin films vary depending sensitively on the ion dose and rapid thermal annealing time. Compared to as-deposited ZnO films, the work-function of phosphorus ion-implanted ZnO thin films is observed to be lower and decreases with increasing ion doses. It is likely that the zinc or oxygen vacancies are firstly filled with the implanted phosphorus ions. With further increased ions, free electrons are generated as Zn2+ sites are replaced by those ions or interstitial phosphorus ions increase at the lattice sites, the fermi level by which approaches the conduction band and thus the work function decreases. Those films exhibit the optical transmittance higher than 85% within the visible wavelength range (up to 800 nm).

Decrease in work function of boron ion-implanted ZnO thin films.

We have fabricated boron ion-implanted ZnO thin films by ion implantation into sputtered ZnO thin films on a glass substrate. An investigation of the effects of ion doses and activation time on the electrical and optical properties of the films has been made. The electrical sheet resistance and resistivity of the implanted films are observed to increase with increasing rapid thermal annealing (RTA) time, while decreasing as the ion dose increases. Without any RTA process, the variation of the carrier density is insensitive to the ion dose. With the RTA process, however, the carrier density of the implanted films increases and approaches that of the un-implanted ZnO film as the ion dose increases. On the other hand, the carrier mobility is shown to decrease with increasing ion doses when no RTA process is applied. With the RTA process, however, there is almost no change in the mobility. We have achieved the optical transmittance as high as 87% within the visible wavelength range up to 800 nm. It is also demonstrated that the work function can be engineered by changing the ion dose during the ion implantation process. We have found that the work function decreases as the ion dose increases.

Work function increase of Al-doped ZnO thin films by B+ ion implantation.

The work function of an Al-doped ZnO (AZO) thin film can be increased via B+ ion implantation from 3.92 eV up to 4.22 eV. The ion implantation has been carried out with the ion dose of 1 x 10(16) cm(-2) and ion energy of 5 keV. The resistance of the B+ implanted AZO films has been a bit raised, while their transmittance is slightly lowered, compared to those of un-implanted AZO films. These behaviors can be explained by the doping profile and the resultant band diagram. It is concluded that the coupling between the B+ ions and oxygen vacancies would be the main reason for an increase in the work function and a change in the other properties. We also address that the work function is more effectively alterable if the defect density of the top transparent conducting oxide layer can be controlled.