Photodetectors based on reduced graphene oxide (rGO) have attracted much attention owing to their simple and low‐cost fabrication process. However, the aggregation and defects of rGO flakes still ...limit the performance of rGO photodetectors. Controlling the composition of rGO has become a vital factor for its prospective applications. For example, the interconnection between rGO and polymers for modified morphologies of rGO films leads to an enhanced performance of devices. In this work, a practical approach to engineer surface uniformity and enhance the performance of a photodetector by modifying the rGO film with hydrophilic polymers poly(vinyl alcohol) (PVA) is reported. Compared with the rGO photodetector, the on/off ratio for the PVA/rGO photodetector shows 3.5 times improvement, and the detectivity shows 53% enhancement even when the photodetector is operated at a low bias of 0.3 V. This study provides an effective route to realize PVA/rGO photodetectors with a low‐power operation which shows promising opportunities for the future development of green systems.
A practical approach to enhance the performance of a reduced graphene oxide (rGO) photodetector by modifying the rGO film with poly(vinyl alcohol) (PVA) is reported. Compared with the rGO photodetector, the on/off ratio for the PVA/rGO photodetector shows 3.5 times improvement, and the detectivity shows 53% enhancement at a low operating bias of 0.3 V.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In this work, Ga2O3 films were deposited on sapphire substrates using a plasma-enhanced atomic layer deposition system with trimethylgallium precursor and oxygen (O2) plasma. To improve the quality ...of Ga2O3 films, they were annealed in an O2 ambient furnace system for 15 min at 700, 800, and 900 °C, respectively. The performance improvement was verified from the measurement results of X-ray diffraction, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The optical bandgap energy of the Ga2O3 films decreased with an increase of annealing temperatures. Metal-semiconductor-metal ultraviolet C photodetectors (MSM UVC-PDs) with various Ga2O3 active layers were fabricated and studied in this work. The cut-off wavelength of the MSM UVC-PDs with the Ga2O3 active layers annealed at 800 °C was 250 nm. Compared with the performance of the MSM UVC-PDs with the as-grown Ga2O3 active layers, the MSM UVC-PDs with the 800 °C-annealed Ga2O3 active layers under a bias voltage of 5 V exhibited better performances including photoresponsivity of 22.19 A/W, UV/visible rejection ratio of 5.98 × 104, and detectivity of 8.74 × 1012 cmHz1/2W−1.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this work, Ga2O3 nanorods were converted from GaOOH nanorods grown using the hydrothermal synthesis method as the sensing membranes of NO2 gas sensors. Since a sensing membrane with a high ...surface-to-volume ratio is a very important issue for gas sensors, the thickness of the seed layer and the concentrations of the hydrothermal precursor gallium nitrate nonahydrate (Ga(NO3)3·9H2O) and hexamethylenetetramine (HMT) were optimized to achieve a high surface-to-volume ratio in the GaOOH nanorods. The results showed that the largest surface-to-volume ratio of the GaOOH nanorods could be obtained using the 50-nm-thick SnO2 seed layer and the Ga(NO3)3·9H2O/HMT concentration of 12 mM/10 mM. In addition, the GaOOH nanorods were converted to Ga2O3 nanorods by thermal annealing in a pure N2 ambient atmosphere for 2 h at various temperatures of 300 °C, 400 °C, and 500 °C, respectively. Compared with the Ga2O3 nanorod sensing membranes annealed at 300 °C and 500 °C, the NO2 gas sensors using the 400 °C-annealed Ga2O3 nanorod sensing membrane exhibited optimal responsivity of 1184.6%, a response time of 63.6 s, and a recovery time of 135.7 s at a NO2 concentration of 10 ppm. The low NO2 concentration of 100 ppb could be detected by the Ga2O3 nanorod-structured NO2 gas sensors and the achieved responsivity was 34.2%.
In this study, CdSe/ZnS core-shell quantum dots (QDs) with various dimensions were used as the color conversion materials. QDs with dimensions of 3 nm and 5 nm were excited by gallium nitride ...(GaN)-based blue micro-light-emitting diodes (micro-LEDs) with a size of 30 μm × 30 μm to respectively form the green and red lights. The hybrid Bragg reflector (HBR) with high reflectivity at the regions of the blue, green, and red lights was fabricated on the bottom side of the micro-LEDs to reflect the downward light. This could enhance the intensity of the green and red lights for the green and red QDs/micro-LEDs to 11% and 10%. The distributed Bragg reflector (DBR) was fabricated on the QDs color conversion layers to reflect the non-absorbed blue light that was not absorbed by the QDs, which could increase the probability of the QDs excited by the reflected blue light. The blue light absorption material was deposited on the DBR to absorb the blue light that escaped from the DBR, which could enhance the color purity of the resulting green and red QDs/micro-LEDs to 90.9% and 90.3%, respectively.
In this study, magnesium-doped gallium oxide (Ga2O3:Mg) films with various Mg contents were deposited by a plasma-enhanced atomic layer deposition (PE-ALD) system and were used as an active layer of ...metal-semiconductor-metal ultraviolet C photodetectors (MSM UVC-PDs). Compared with Ga element, owing to the lower electronegativity of Mg element, Mg–O bonds were more easily formed than Ga–O bonds. Consequently, oxygen vacancies could be reduced to improve properties. By using the measurement of X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL), the results verified that Ga2O3:Mg films with Mg content of 3.28 at.% had the lowest oxygen vacancy density. The cut-off wavelength of the devices was blue-shifted from 250 nm to 220 nm by increasing Mg content from 0 at.% to 5.22 at.%. The maximum photoresponsivity of 22.06, 10.24, 6.89, and 1.67 A/W was obtained for the devices with the Mg content of 0 at.%, 1.91 at.%, 3.28 at.%, and 5.22 at.%, respectively. The corresponding UV–visible rejection ratio was 3.56 × 104, 3.86 × 104, 4.42 × 104, and 3.48 × 103, respectively. The flicker noise was the dominant noise. By appropriately doping the Mg content in Ga2O3 films, the detectivity of the MSM UVC-PDs was effectively improved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, novel NO2 gas sensors having p-n heterojunction bi-sensing membranes obtained using gold black/VOx films were developed. VOx and gold black films were sequentially deposited on quartz ...substrates through radio frequency magnetron sputtering system and low-temperature vapor cooling condensation system, respectively. Scanning electron microscopy and atomic force microscopy images revealed that a rougher surface was obtained for gold black/VOx bi-sensing membranes than for VOx sensing membranes. After the detection of NO2 gas by using an NO2 gas sensor with a gold black sensing membrane and another with a VOx sensing membrane, results confirmed that the p-n heterojunction could be formed using gold black/VOx bi-sensing membranes. Because of a large surface area-to-volume ratio and the formation of the p-n junction of gold black/VOx bi-sensing membranes, the gas response of prepared NO2 gas sensors was improved from 78.78% to 188.15% compared with NO2 gas sensors with VOx membranes operated under 100 ppm NO2 concentration at its respectively optimal operating temperature. Furthermore, in NO2 gas sensors with gold black/VOx bi-sensing membranes, a minimum NO2 concentration of 1 ppm could be detected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, various reciprocating cycle times of 80, 160, 240, and 320 sec in the diamond wire sawing (DWS) process were adjusted to improve the slicing ability in solar industry. During the same ...slicing time, the long reciprocating cycle time had less velocity inverse points in comparison with the short reciprocating cycle time. Consequently, the total friction force of the slicing wires used in the DWS process with the short reciprocating cycle time was larger than that of the slicing wires used in the DWS process with the long reciprocating cycle time. It was noting that the lower diamond consumption and better slicing ability in the DWS process with a reciprocating cycle time of 320 sec was obtained in comparison with a reciprocating cycle time of 80 sec. However, since the diamond grits with too high slicing strength to collide the Si material, the serious damages were form on the wafer edge. Therefore, the edge chipping increased to 1.63% as the reciprocating cycle time of 320 sec. The highest mass production yield of 94.22% and the lowest edge chipping of 1.23% for the DWS-sliced mc-Si wafers were obtained as the suitable reciprocating cycle time was 240 sec.
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this work, a vapor cooling condensation system was utilized to deposit various amounts of p-type gold-black nanoparticles (NPs) onto the surface of n-type gallium oxide (Ga2O3) nanorods forming ...p–n heterojunction-structured sensing membranes of nitrogen dioxide (NO2) gas sensors. The role and the sensing mechanism of the various gold-black NP-decorated Ga2O3 nanorods in NO2 gas sensors were investigated. The coverage and atomic percentage of the sensing membranes were observed using high-resolution transmission electron microscopy (HRTEM) measurements and energy-dispersive spectroscopy (EDS), respectively. For the NO2 gas sensor using the sensing membrane of 60 s-deposited gold-black NP-decorated Ga2O3 nanorods under a NO2 concentration of 10 ppm, the highest responsivity of 5221.1% was obtained. This result was attributed to the spillover effect and the formation of the p–n heterojunction, which increased more ionized-oxygen adsorption sites and promoted the reaction between NO2 gas and Ga2O3 nanorods. Furthermore, the NO2 gas sensor could detect the low NO2 concentration of 100 ppb and achieved a responsivity of 56.9%. The resulting NO2 gas sensor also exhibited excellent selectivity for detecting NO2 gas, with higher responsivity at a NO2 concentration of 10 ppm compared with that of the C2H5OH and NH3 concentrations of 100 ppm.
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IJS, KILJ, NUK, PNG, UL, UM
10.
MVIN Tai, Chang-You; Wu, Meng-Ru; Chu, Yun-Wei ...
Proceedings of the 43rd International ACM SIGIR Conference on Research and Development in Information Retrieval,
07/2020
Conference Proceeding
Open access
Researchers have begun to utilize heterogeneous knowledge graphs(KGs) as auxiliary information in recommendation systems to mitigate the cold start and sparsity issues. However, utilizing a graph ...neural network (GNN) to capture information in KG and further apply in RS is still problematic as it is unable to see each item's properties from multiple perspectives. To address these issues, we propose the multi-view item network (MVIN), a GNN-based recommendation model that provides superior recommendations by describing items from a unique mixed view from user and entity angles. MVIN learns item representations from both the user view and the entity view. From the user view, user-oriented modules score and aggregate features to make recommendations from a personalized perspective constructed according to KG entities which incorporates user click information. From the entity view, the mixing layer contrasts layer-wise GCN information to further obtain comprehensive features from internal entity-entity interactions in the KG. We evaluate MVIN on three real-world datasets: MovieLens-1M (ML-1M), LFM-1b 2015 (LFM-1b), and Amazon-Book (AZ-book). Results show that MVIN significantly outperforms state-of-the-art methods on these three datasets. Besides, from user-view cases, we find that MVIN indeed captures entities that attract users. Figures further illustrate that mixing layers in a heterogeneous KG plays a vital role in neighborhood information aggregation.
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