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We demonstrate frequency-triggered internal circuit transition in high-performance organic light-emitting diodes. Blue fluorescent light-emitting devices are fabricated based on a stable and efficient host-dopant material system. Broad-band impedance spectroscopy reveals that these diodes systematically undergo two abrupt spectral transitions at two bands of small-signal frequencies. Nyquist plots recorded over a wide range of conditions are fitted to an equivalent circuit model, decoupling the key interface and bulk parameters. The sharp conductance increases identified from this procedure are conceptually linked to the trap deactivation at specific cut-off frequencies, suggesting new opportunities for alternating-current applications of organic light-emitting diodes. [ABSTRACT FROM AUTHOR]

The etch characteristics of Si and TiO2 nanostructures for optical devices were investigated using pulse biased inductively coupled plasmas (ICP) with SF6/C4F8/Ar and BCl3/Ar, respectively, and the results were compared with those etched using continuous wave (CW) biased ICP. By using pulse biasing compared to CW biasing in the etching of the line/pillar nanostructures with various aspect ratios, there was a reduction of the aspect ratio dependent etching (ARDE) and therefore, uniform etch depths for nanostructures with different pattern widths, as well as the improvement of the etch profiles without any notching, were obtained not only for silicon nanostructures but also for TiO2 nanostructures. The investigation has determined that the improvement of etch profiles and reduced ARDE effect when using pulse biasing are related to the decreased surface charging caused by neutralization of the surface and the improved radical adsorption (or etch byproduct removal) on the etched surfaces during the pulse-off period for pulse biasing compared to CW biasing. [ABSTRACT FROM AUTHOR]

Perfluorocarbon gases are commonly used for nanoscale etching in semiconductor processing; however, they have the disadvantages of a long lifetime and inducing global warming effects when released into the atmosphere. In this study, the SiO2 etch characteristics and global warming effects of C3F6O gas chemistry, which has a low global warming potential, were compared with those of C4F8 chemistry, which is commonly used in semiconductor processing. Using Ar/C3F6O, the SiO2 etch rate was higher and the etch selectivity of SiO2 over the amorphous carbon hardmask layer was lower than the etch rate and etch selectivity using Ar/C4F8/O2, with all other etch conditions the same. Furthermore, using Ar/C3F6O exhibited more anisotropic SiO2 etch profiles by suppressing the bowing, narrowing, and necking effects compared to the etch profiles using Ar/C4F8/O2. The global warming effects were evaluated by calculating the million metric ton carbon equivalents (MMTCEs) from the volumetric concentrations of the emitted by-product species and process gases, and the results showed that, in the optimized conditions, Ar/C3F6O exhibited a lower environmental impact with an MMTCE of <24% than that of Ar/C4F8/O2. Therefore, it is suggested that the Ar/C3F6O gas mixture is a potential replacement for Ar/C4F8/O2 because of its lower MMTCE and acceptable SiO2 etch characteristics. [ABSTRACT FROM AUTHOR]

High-aspect-ratio patterns are required for next-generation three-dimensional (3D) semiconductor devices. However, it is challenging to eliminate voids and seams during gap-filling of these high-aspect-ratio patterns, such as deep trenches, especially for nanoscale high-aspect-ratio patterns. In this study, a SiO 2 plasma-enhanced atomic layer deposition process incorporated with ion collision using bias power to the substrate was used for bottom-up trench gap-filling. The effect of bias power frequency on SiO 2 trench gap-filling was then investigated. Results showed that changes in bias power frequency did not significantly change the process rate, such as SiO 2 growth per cycle. At relatively low bias power frequencies, high-energy ions formed an overhang at the entrance of the high-aspect-ratio trench pattern through sputter etching and redeposition, blocking the pattern entrance. However, at relatively high-frequency bias power, overhang formation due to sputtering did not occur. In the trench interior, due to a scattering effect of ions, deposition was thicker at the bottom of the trench than that at the top, achieving bottom-up gap-filling and void-free gap-filling.

The etch characteristics of Si and TiO 2 nanostructures for optical devices were investigated using pulse biased inductively coupled plasmas (ICP) with SF 6 /C 4 F 8 /Ar and BCl 3 /Ar, respectively, and the results were compared with those etched using continuous wave (CW) biased ICP. By using pulse biasing compared to CW biasing in the etching of the line/pillar nanostructures with various aspect ratios, there was a reduction of the aspect ratio dependent etching (ARDE) and therefore, uniform etch depths for nanostructures with different pattern widths, as well as the improvement of the etch profiles without any notching, were obtained not only for silicon nanostructures but also for TiO 2 nanostructures. The investigation has determined that the improvement of etch profiles and reduced ARDE effect when using pulse biasing are related to the decreased surface charging caused by neutralization of the surface and the improved radical adsorption (or etch byproduct removal) on the etched surfaces during the pulse-off period for pulse biasing compared to CW biasing.

We demonstrate plasma-treated Ag nanowires (NWs) as flexible transparent electrode materials with enhanced long-term stability against oxidation even in a high humidity environment (80% humidity, 20 °C). Through a simple fluorocarbon (C 4 F 8 or C 4 F 6 ) plasma treatment method, a C x F y protective polymer was sufficiently cross-linked and attached on the surface of the AgNWs strongly and uniformly. Even though C 4 F 8 and C 4 F 6 activate differently on the AgNW surface due to the different dissociated radicals formed in the plasma, it was found that the C x F y protective polymers obtained by both chemicals work similarly as a protective layer for transparent conductive electrodes; a nearly constant sheet resistance ratio (R s /R o ) of 1.6 was found for AgNWs treated with C 4 F 8 and C 4 F 6 plasmas, while the AgNWs without the plasma treatment exhibited a ratio of 176.2 after 36 days in a harsh environment. It is believed that the fluorocarbon plasma treatment can be used as a key method for ensuring long-term oxidation stability in numerous electronic applications including flexible solar cells utilizing various types of metallic nanowires.