ABSTRACT
Micro light-emitting diodes (micro-LEDs) are pivotal in next-generation display technologies, driven by the need for high pixel density. This study introduces a novel methodology utilizing wide sapphire nanomembranes (W-SNM) as a dual-purpose template for high-quality epitaxial growth and the mechanical lift-off of individual micro-LEDs. Micro-LEDs grow individually on W-SNM, obviating the chip singulation process. By employing mechanical fracturing of the thin W-SNM, our method facilitates the transfer of micro-LEDs without the conventional laser lift-off (LLO) process. Previously introduced sapphire nanomembranes (SNM) have shown promise in enhancing epitaxial layer quality; however, they encountered challenges in managing micro-LED size variation and achieving efficient mechanical transfer. Here, we apply simple yet effective adjustments to the SNM structure, specifically, its elevation and widening. This strategic modification allows micro-LEDs to endure applied forces without incurring cracks or defects, ensuring that only the targeted W-SNM are selectively fractured. The mechanically transferred vertical 15 × 15 µm2 micro-LED device operates at an optimal turn-on voltage of 3.3 V. Finite element simulations validate the mechanical strain distribution between the W-SNM and GaN when pressure is applied, confirming the efficacy of our design approach. This pioneering methodology offers a streamlined, efficient pathway for the production and mechanical transfer of micro-LEDs, presenting new avenues for their integration into next-generation, high-performance displays.
ABSTRACT
Micro-light-emitting diodes (µLEDs) have gained significant interest as an activation source for gas sensors owing to their advantages, including room temperature operation and low power consumption. However, despite these benefits, challenges still exist such as a limited range of detectable gases and slow response. In this study, we present a blue µLED-integrated light-activated gas sensor array based on SnO2 nanoparticles (NPs) that exhibit excellent sensitivity, tunable selectivity, and rapid detection with micro-watt level power consumption. The optimal power for µLED is observed at the highest gas response, supported by finite-difference time-domain simulation. Additionally, we first report the visible light-activated selective detection of reducing gases using noble metal-decorated SnO2 NPs. The noble metals induce catalytic interaction with reducing gases, clearly distinguishing NH3, H2, and C2H5OH. Real-time gas monitoring based on a fully hardware-implemented light-activated sensing array was demonstrated, opening up new avenues for advancements in light-activated electronic nose technologies.
ABSTRACT
Exsolution generates metal nanoparticles anchored within crystalline oxide supports, ensuring efficient exposure, uniform dispersion, and strong nanoparticle-perovskite interactions. Increased doping level in the perovskite is essential for further enhancing performance in renewable energy applications; however, this is constrained by limited surface exsolution, structural instability, and sluggish charge transfer. Here, hybrid composites are fabricated by vacuum-annealing a solution containing SrTiO3 photoanode and Co cocatalyst precursors for photoelectrochemical water-splitting. In situ transmission electron microscopy identifies uniform, high-density Co particles exsolving from amorphous SrTiO3 films, followed by film-crystallization at elevated temperatures. This unique process extracts entire Co dopants with complete structural stability, even at Co doping levels exceeding 30%, and upon air exposure, the Co particles embedded in the film oxidize to CoO, forming a Schottky junction at the interface. These conditions maximize photoelectrochemical activity and stability, surpassing those achieved by Co post-deposition and Co exsolution from crystalline oxides. Theoretical calculations demonstrate in the amorphous state, dopantâO bonds become weaker while TiâO bonds remain strong, promoting selective exsolution. As expected from the calculations, nearly all of the 30% Fe dopants exsolve from SrTiO3 in an H2 environment, despite the strong FeâO bond's low exsolution tendency. These analyses unravel the mechanisms driving the amorphous exsolution.
ABSTRACT
Long-term results of orthotopic heart transplantation vary among different institutions. The purpose of the present study was to assess the factors, which might affect long-term survival and complications. Between November 1992 and July 2003, 112 heart transplantations (M/F=89: 23) were performed. The standard technique was used in the first 57 patients and the bicaval technique in the latter 55 patients. Indications for transplantation in decreasing order of frequency were dilated cardiomyopathy (75%), ischemic cardiomyopathy (7%), and others (18%). The mean follow up duration was 51.8 +/- 31.3 months with 98 patients remaining alive. Preoperatively, all patients were either in NYHA functional class III or IV. Postoperatively, all patients showed improvement to functional class II or I, except 3 patients that remained in NYHA class III. The mean number of rejection cases within the first year was 0.6 +/- 0.8, with humoral rejection noted in 3 cases. The graft vascular disease (GVD) -free survival at 3 and 5 years was 96% and 83%, respectively. The 7-year survival after heart transplantation was 84%. There were 16 deaths, of which infection (n=4) was the most common followed by rejection (n=3), and malignancy (n=2). The present long-term results, were relatively superior to those seen in western countries. The relatively low GVD-free survival rate is thought to have contributed. The complications encountered after transplantation were mostly immunosuppressive drug related, suggesting further potentials for improvement in long-term survival.