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An interesting hydrogen (H2) gas sensor, synthesized by an indium oxide (In2O3) layer and evaporated palladium (Pd) nanoparticles (NPs), is manufactured and studied. The utilized Pd NPs essentially enhance the surface area/volume (${S}_{A}/{V})$ ratio and catalytic reactivity of the Pd metal. Energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), high-resolution scanning electron microscopy (HRSEM), and TEM were used to investigate the relevant material behaviors of the proposed Pd NP/In2O3 sensor device. The sensing mechanism is explicated in this study. A very high-sensing response of 5243 under 1% H2/air gas with a response time of 12 s and an extremely low-detecting content of 100 ppb H2/air were obtained at the optimal operating temperature of 225 °C. In addition, excellent selectivity toward hydrogen gas is observed for the studied device. The proposed sensor also shows advantages of simple structure, low-cost, and relatively easy fabrication process. [ABSTRACT FROM AUTHOR]

A new hydrogen (H2) gas sensor, synthesized with a radio frequency (RF) sputtered cerium oxide (CeO2) thin film and rapid thermal evaporated palladium (Pd) nanoparticles (NPs), is fabricated and reported herein. The employed Pd NPs can effectively increase the surface area/volume (${S}_{A}$ /V) ratio and catalytic reactivity of Pd metal, thereby substantially enhancing the adsorption effect of hydrogen molecules on the device surface and improving the related sensing performance. Energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to characterize the related properties of the studied device. Experimentally, a high sensing response of 120.2 under 1% H2/air gas at 350 °C with a relatively shorter response (recovery) time of 5 s (17 s) is obtained. The studied Pd NP/CeO2-based sensor device shows wide operating ranges of temperature (200 °C–400 °C) and hydrogen concentration (10 ppm—1% H2/air). A thermodynamic analysis employed to study the surface coverage of hydrogen molecules is reported in this work. The studied sensor device also exhibits the advantages of a simple structure, easy fabrication process, and relatively low cost. [ABSTRACT FROM AUTHOR]

A hybrid structure, including 45° sidewalls, a microhole array, and a thin SiO2 nanoparticle (NP)/microsphere (MS) passivation layer, is used to produce GaN-based light-emitting diodes (LEDs). The influences of the microhole depth and SiO2 NP/MS passivation layer on the LED performance are studied. A shallower depth of a microhole array shows better optical properties due to the complete preservation of the GaN/InGaN multiple quantum well (MQW) region. In addition, the use of a thin SiO2 NP/MS passivation layer gives a remarkably reduced reverse-biased leakage current and improved optical performance. Experimentally, under an injection current density of 110 A/cm2, the studied device, with a proper hybrid structure, shows enhancements of 25.9%, 29.2%, and 29.4% in light output power (LOP), external quantum efficiency (EQE), and wall-plug efficiency, respectively, as compared to a LED device with a deeper depth of microhole array. These improvements are mainly caused by the reduced total internal reflection (TIR) and the Fresnel reflection, which increase scattering probability and the opportunity to find photon escape cones. Hence, the studied hybrid structure in this work is a promising route to fabricate high-performance GaN-based LEDs. [ABSTRACT FROM AUTHOR]

The characteristics of GaN-based light-emitting diodes (LEDs) with a hybrid structure incorporating a microhole array, 45 sidewalls, and an appropriate SiO2 nanoparticle (NP)/microsphere (MSs) passivation layer are studied and reported. The use of a SiO2 NP/MSs passivation layer causes a remarkable reduction in reverse-biased leakage current. The employment of this hybrid structure leads to substantial enhancements in optical properties without any degradation in electrical performance. In addition, a lower content of SiO2 NP in the mixed SiO2 NP/MSs solution leads to enhanced optical behavior due to the improved transmittance. Experimentally, as compared with a conventional LED (Device A), the studied Device E shows 50.6%, 50.9%, 48.4%, and 49.9% enhancements in light output power, luminous flux, luminous efficacy, and wall-plug efficiency, respectively. These advantages are mainly attributed to the increased scattering probability and the opportunity to find photon escape cones as well as the reduced total internal reflection and Fresnel reflection effects. Therefore, the studied hybrid structure provides a promise for high-performance GaN-based LED applications. [ABSTRACT FROM AUTHOR]