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Red-green-blue (RGB) full-color micro light-emitting diodes (μ-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The semipolar (20-21) InGaN/GaN μ-LEDs were fabricated on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. The semipolar μ-LEDs showed a 3.2 nm peak wavelength shift and a 14.7% efficiency droop under 200    A / cm 2 injected current density, indicating significant amelioration of the quantum-confined Stark effect. Because of the semipolar μ-LEDs’ emission-wavelength stability, the RGB pixel showed little color shift with current density and achieved a wide color gamut (114.4% NTSC space and 85.4% Rec. 2020).

We investigate the index sensing characteristics of plasmonic arrays based on square lattice slablike gold nanorings ͑NRs͒ with different ring widths. The gold NR arrays exhibit two extinction peaks in the visible and near-infrared corresponding to antibonding and bonding modes. Redshift and blueshift in antibonding and bonding modes when broadening the average ring width are observed. We experimentally demonstrate the sensitivity of bonding mode can be tuned by varying the average ring width. However, the sensing performance is limited because the enhanced fields concentrate inside the shell-like structures. The nanoring ͑NR͒ structure surmounts this limitation due to the extension of inside field to the environment. This leads to significant increase in the detection sensitivity. 20 The NR plasmonic properties can be seen as the electromagnetic interaction between the nanodisc and the nanohole plasmons. [21][22][23] This results in the splitting of the plasmon mode into two resonance modes, which are the low energy "bonding" mode and the high energy "antibonding" mode. The resonance frequencies of both resonance modes can be easily tuned in the visible ͑VIS͒ and NIR range by adjusting the geometry of NR, which is useful for various optical sensing applications.In this letter, we report our experimental investigation of bonding and antibonding modes in plasmonic arrays based on square lattice slablike gold NRs with different ring widths. The refractive index sensing experiments of such structures are performed by immersing the samples in index matching liquids. We show that the sensitivities of NR arrays exhibit a linear relationship with ring widths for the bonding mode in the NIR regime. These results are crucial in designing LSP resonance ͑LSPR͒ sensors based on periodic metallic nanostructures.The scheme of square lattice gold NR array with ring thickness t, periodicity p, diameter d, and average width w is shown in Fig. 1͑a͒. The periodicity, diameter, and thickness are fixed at 1 m, 500 nm, and 50 nm. In fabrication, the ITO glass is utilized as the substrate to avoid the charge accumulation effect during electron beam lithography ͑EBL͒. First, the ITO glass was spin-coated a 150 nm polymethylmethacrylate ͑PMMA͒ layer. The NR patterns with area of 300ϫ 300 m 2 and different ring widths were defined on the PMMA layer by EBL. After the development process, a gold thin film with thickness of 50 nm was deposited by thermal evaporation. Then the liftoff process is applied by rinsing the sample in acetone for a few hours. The periodicity p of array is 1 m, the ring diameter is 500 nm, and the ring thickness t is 50 nm.APPLIED PHYSICS LETTERS 98, 153108 ͑2011͒

Integration of strain engineering of two-dimensional (2D) materials in order to enhance device performance is still a challenge. Here, we successfully demonstrated the thermally strained band gap engineering of transition-metal dichalcogenide bilayers by different thermal expansion coefficients between 2D materials and patterned sapphire structures, where MoS bilayers were chosen as the demonstrated materials. In particular, a blue shift in the band gap of the MoS bilayers can be tunable, displaying an extraordinary capability to drive electrons toward the electrode under the smaller driven bias, and the results were confirmed by simulation. A model to explain the thermal strain in the MoS bilayers during the synthesis was proposed, which enables us to precisely predict the band gap-shifted behaviors on patterned sapphire structures with different angles. Furthermore, photodetectors with enhancement of 286% and 897% based on the strained MoS on cone- and pyramid-patterned sapphire substrates were demonstrated, respectively.

We report a pentacene thin film transistor nonvolatile memory fabricated on a flexible polyimide substrate. This device shows a low program/erase voltage of 12 V, a speed of 1/100 ms, an initial memory window of 2.4 V, and a 0.78 V memory window after 48 h. This has been achieved by using a high-dielectric as charge trapping, blocking, and tunneling gate insulator layers.