Surfactant Micelle-Driven High-Efficiency and High-Resolution Length Separation of Carbon Nanotubes for Electronic Applications.

High-efficiency extraction of long single-wall carbon nanotubes (SWCNTs) with excellent optoelectronic properties from SWCNT solution is critical for enabling their application in high-performance optoelectronic devices. Here, a straightforward and high-efficiency method is reported for length separation of SWCNTs by modulating the concentrations of binary surfactants. The results demonstrate that long SWCNTs can spontaneously precipitate for binary-surfactant but not for single-surfactant systems. This effect is attributed to the formation of compound micelles by binary surfactants that squeeze the free space of long SWCNTs due to their large excluded volumes. With this technique, it can readily separate near-pure long (≥500 nm in length, 99% in content) and short (≤500 nm in length, 98% in content) SWCNTs with separation efficiencies of 26% and 64%, respectively, exhibiting markedly greater length resolution and separation efficiency than those of previously reported methods. Thin-film transistors fabricated from extracted semiconducting SWCNTs with lengths >500 nm exhibit significantly improved electrical properties, including a 10.5-fold on-state current and 14.7-fold mobility, compared with those with lengths <500 nm. The present length separation technique is perfectly compatible with various surfactant-based methods for structure separations of SWCNTs and is significant for fabrication of high-performance electronic and optoelectronic devices.

Suppression of Photoinduced Phase Segregation in Mixed-Halide Perovskite Nanocrystals for Stable Light-Emitting Diodes.

Halide segregation is a critical bottleneck that hampers the application of mixed-halide perovskite nanocrystals (NCs) in both electroluminescent and down-conversion red-light-emitting diodes. Herein, we report a strategy that combines precursor and surface engineering to obtain pure-red-emitting (peaked at 624 nm) NCs with a photoluminescence quantum yield of up to 92% and strongly suppresses the halide segregation of mixed-halide NCs under light irradiation. Red-light-emitting diodes (LED) using these mixed-halide NCs as phosphors exhibit color-stable emission with a negligible peak shift and spectral broadening during operation over 240 min. By contrast, a dramatic peak shift and spectral broadening were observed after 10 min of operation in LEDs based on mixed-halide NCs synthesized by a traditional method. Our strategy is critical to achieving photo- and band-gap-stable mixed-halide perovskite NCs for a variety of optoelectronic applications such as micro-LEDs.

Pathological Myopia Image Recognition Strategy Based on Data Augmentation and Model Fusion.

The automatic diagnosis of various retinal diseases based on fundus images is important in supporting clinical decision-making. Convolutional neural networks (CNNs) have achieved remarkable results in such tasks. However, their high expression ability possibly leads to overfitting. Therefore, data augmentation (DA) techniques have been proposed to prevent overfitting while enriching datasets. Recent CNN architectures with more parameters render traditional DA techniques insufficient. In this study, we proposed a new DA strategy based on multimodal fusion (DAMF) which could integrate the standard DA method, data disrupting method, data mixing method, and autoadjustment method to enhance the image data in the training dataset to create new training images. In addition, we fused the results of the classifier by voting on the basis of DAMF, which further improved the generalization ability of the model. The experimental results showed that the optimal DA mode could be matched to the image dataset through our DA strategy. We evaluated DAMF on the iChallenge-PM dataset. At last, we compared training results between 12 DAMF processed datasets and the original training dataset. Compared with the original dataset, the optimal DAMF achieved an accuracy increase of 2.85% on iChallenge-PM.

Temperature-Dependent HfO2/Si Interface Structural Evolution and its Mechanism.

In this work, hafnium oxide (HfO2) thin films are deposited on p-type Si substrates by remote plasma atomic layer deposition on p-type Si at 250 °C, followed by a rapid thermal annealing in nitrogen. Effect of post-annealing temperature on the crystallization of HfO2 films and HfO2/Si interfaces is investigated. The crystallization of the HfO2 films and HfO2/Si interface is studied by field emission transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. The experimental results show that during annealing, the oxygen diffuse from HfO2 to Si interface. For annealing temperature below 400 °C, the HfO2 film and interfacial layer are amorphous, and the latter consists of HfO2 and silicon dioxide (SiO2). At annealing temperature of 450-550 °C, the HfO2 film become multiphase polycrystalline, and a crystalline SiO2 is found at the interface. Finally, at annealing temperature beyond 550 °C, the HfO2 film is dominated by single-phase polycrystalline, and the interfacial layer is completely transformed to crystalline SiO2.

Surface Passivation of Silicon Using HfO2 Thin Films Deposited by Remote Plasma Atomic Layer Deposition System.

Hafnium oxide (HfO2) thin films have attracted much attention owing to their usefulness in equivalent oxide thickness scaling in microelectronics, which arises from their high dielectric constant and thermodynamic stability with silicon. However, the surface passivation properties of such films, particularly on crystalline silicon (c-Si), have rarely been reported upon. In this study, the HfO2 thin films were deposited on c-Si substrates with and without oxygen plasma pretreatments, using a remote plasma atomic layer deposition system. Post-annealing was performed using a rapid thermal processing system at different temperatures in N2 ambient for 10 min. The effects of oxygen plasma pretreatment and post-annealing on the properties of the HfO2 thin films were investigated. They indicate that the in situ remote plasma pretreatment of Si substrate can result in the formation of better SiO2, resulting in a better chemical passivation. The deposited HfO2 thin films with oxygen plasma pretreatment and post-annealing at 500 °C for 10 min were effective in improving the lifetime of c-Si (original lifetime of 1 µs) to up to 67 µs.

Simultaneous dual-wavelength Q-switched Nd:YAG laser at 1052 and 1073 nm.

We report a continuous-wave dual-wavelength Nd:YAG laser at 1052 and 1073 nm, for the first time to the best of our knowledge, in free-running mode. The maximum output power reaches 6.64 W with slope efficiency of about 42.1% with respect to the absorbed power. Inserting a Cr:YAG saturable absorber, the dual-wavelength laser can operate in the Q-switching regime with maximum average output power of 880 mW. The minimum pulse width and the highest pulse repetition rate are 28 ns and 17.12 kHz, respectively. The dual-wavelength laser has potential to generate a 5.7 THz wave via the difference-frequency method.

Sapphire fiber evanescent wave absorption in turbid media.

The influence of particulates on sapphire fiber evanescent wave absorption by water has been studied. Suspensions containing micro-sized graphite flakes and glassy carbon powder were used. Conventional free-space transmittance measurements of these samples showed strong absorption and scattering, which severely screened the absorption by water. However, the absorption on the water band determined from the evanescent wave interaction was unaffected by the presence of the graphite flakes. These results indicate that fiber-optic evanescent wave chemical sensors may be suitable for process control applications involving turbid reactor streams.