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Open AccessArticle

by Sinuo Chen, Lichun Wang, Chunlan Zhou, Jinli Yang and Xiaojie Jia

Energies 2025, 18(21), 5623; https://doi.org/10.3390/en18215623 - 26 Oct 2025

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Cu₂O solar cells are regarded as a promising emerging inorganic photovoltaic technology due to their power conversion efficiency (PCE) potential and material sustainability. While previous studies primarily focused on the band offset between n-type buffer layers and Cu₂O optical [...] Read more.

Cu₂O solar cells are regarded as a promising emerging inorganic photovoltaic technology due to their power conversion efficiency (PCE) potential and material sustainability. While previous studies primarily focused on the band offset between n-type buffer layers and Cu₂O optical absorption, this work systematically investigated an ETL/buffer/p-Cu₂O/HTL heterojunction structure using SCAPS-1D simulations. Key design parameters, including bandgap (Eg) and electron affinity (χ) matching across layers, were optimized to minimize carrier transport barriers. Furthermore, the doping concentration and thickness of each functional layer (ETL: transparent conductive oxide; HTL: hole transport layer) were tailored to balance electron conductivity, parasitic absorption, and Auger recombination. Through this approach, a maximum PCE of 14.12% was achieved (V_oc = 1.51V, J_sc = 10.52 mA/cm², FF = 88.9%). The study also identified candidate materials for ETL (e.g., GaN, ZnO:Mg) and HTL (e.g., ZnTe, NiO_x), along with optimal thicknesses and doping ranges for the Cu₂O absorber. These findings provide critical guidance for advancing high-performance Cu₂O solar cells. Full article

(This article belongs to the Special Issue Functional Materials for Advanced Energy Applications)

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14 pages, 3478 KB

Open AccessArticle

Fabrication of Low-Temperature ppb-Level Ethanol Gas Sensor Based on Hierarchical NiO-SnO₂ Nanoflowers Under Hydrothermal Conditions

by Liming Song, Xiaoxin Dou, Jianmei Shao, Yuanzheng Luo, Fumiao Liu, Chengyong Li, Lijuan Yan, Chuhong Wang, Yuting Li, Yuqing Cai, Jinsheng He, Zhenqing Dai, Ruikun Sun and Qin Xie

Nanomaterials 2025, 15(19), 1471; https://doi.org/10.3390/nano15191471 - 25 Sep 2025

Viewed by 354

Abstract

Hierarchical NiO-SnO₂ nanoflowers were prepared via a one-step hydrothermal method. The morphology, structure and components of the hierarchical NiO-SnO₂ nanoflowers were examined via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. [...] Read more.

Hierarchical NiO-SnO₂ nanoflowers were prepared via a one-step hydrothermal method. The morphology, structure and components of the hierarchical NiO-SnO₂ nanoflowers were examined via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The ethanol gas-sensing performance was systematically analyzed between pure hierarchical SnO₂ nanoflowers and the hierarchical NiO-SnO₂ nanoflowers. The results indicated that the hierarchical NiO-SnO₂ nanoflowers showed better gas-sensing properties than the pure hierarchical SnO₂ nanoflowers at 164 °C. The enhanced gas-sensing performance was ascribed to the formation of p-n heterojunctions between p-type NiO and n-type SnO₂. Additionally, NiO has a catalytic role. Therefore, hierarchical NiO-SnO₂ nanoflowers could be a potential gas-sensing material for the fabrication of high-quality ethanol gas sensors. Full article

(This article belongs to the Special Issue Nanomaterials for Micro/Nano Sensing and Detecting Applications)

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15 pages, 5432 KB

Open AccessEditor’s ChoiceArticle

Nano-Heterojunction NO₂ Gas Sensor Based on n-ZnO Nanorods/p-NiO Nanoparticles Under UV Illumination at Room Temperature

by Yoon-Seo Park, Sohyeon Kim, Junyoung Lee, Jae-Hoon Jeong, Sung-Yun Byun, Jiyoon Shin, Il-Kyu Park and Kyoung-Kook Kim

Nanomaterials 2025, 15(18), 1426; https://doi.org/10.3390/nano15181426 - 16 Sep 2025

Viewed by 623

Abstract

Room-temperature (RT) gas sensors for nitrogen dioxide (NO₂) detection face persistent challenges, including reliance on high operating temperatures and inefficient charge carrier utilization under UV activation. To address these limitations, we engineered a p-n nano-heterojunction (NHJ) gas sensor by [...] Read more.

Room-temperature (RT) gas sensors for nitrogen dioxide (NO₂) detection face persistent challenges, including reliance on high operating temperatures and inefficient charge carrier utilization under UV activation. To address these limitations, we engineered a p-n nano-heterojunction (NHJ) gas sensor by integrating p-type nickel oxide (NiO) nanoparticles onto n-type zinc oxide (ZnO) nanorods. This architecture leverages UV-driven carrier generation and interfacial electric fields at the NHJ to suppress recombination, enabling unprecedented RT performance. By optimizing thermal annealing conditions, we achieved a well-defined heterojunction with uniform NiO distribution on the top of the ZnO nanorods, validated through electron microscopy and X-ray photoelectron spectroscopy. The resulting sensor exhibits a 5.4-fold higher normalized response to 50 ppm NO₂ under 365 nm UV illumination compared to pristine ZnO, alongside rapid recovery and stable cyclability. The synergistic combination of UV-assisted carrier generation and heterojunction-driven interfacial modulation offers a promising direction for next-generation RT gas sensors aimed at environmental monitoring. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Sensing Applications)

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12 pages, 2274 KB

Open AccessArticle

Simulation Study on Electrical Characteristics of NiO/β-Ga₂O₃ Heterojunction Enhancement Mode HJ-FinFET

by Jiangang Yu, Ziwei Li, Fengchao Li, Haibing Qiu, Tengteng Li, Cheng Lei and Ting Liang

Crystals 2025, 15(9), 771; https://doi.org/10.3390/cryst15090771 - 29 Aug 2025

Viewed by 688

Abstract

In this paper, a novel enhancement-mode β-Ga₂O₃-based FinFET structure with a gate formed by the NiO/β-Ga₂O₃ heterojunction named HJ-FinFET has been proposed, and the excellent performance of the device has also been demonstrated. The primary operational [...] Read more.

In this paper, a novel enhancement-mode β-Ga₂O₃-based FinFET structure with a gate formed by the NiO/β-Ga₂O₃ heterojunction named HJ-FinFET has been proposed, and the excellent performance of the device has also been demonstrated. The primary operational mechanism of this structure involves integrating p-type NiO on both sides of the fin-shaped channel, which forms p-n junctions with β-Ga₂O₃. The depletion regions thus generated are utilized to establish electron channels, enabling enhancement-mode operation. The reverse p-NiO/n-Ga₂O₃ heterojunction diode is integrated to reduce the reverse free-wheeling loss. Compared with the conventional devices, the threshold voltage of the HJ-FinFET is greatly improved, and normally off operation is realized, showing a positive threshold voltage of 2.14 V. Meanwhile, the simulated breakdown voltage of the HJ-FinFET reaches 2.65 kV with specific on-resistance (R_on,sp) of 2.48 mΩ·cm² and the power figure of merit (PFOM = BV²/R_on,sp) reaches 2840 MW/cm², respectively. In addition, the influence of the doping concentration of the heterojunction layer constituting the gate, the doping concentration of the drift layer, and the channel width on the electrical characteristics of the devices were focused on. This structure provides a feasible idea for high-performance β-Ga₂O₃-based FinFET. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 2994 KB

Open AccessArticle

Band-Engineered α-Fe₂O₃@NiO P-N Heterojunction for Room-Temperature NH₃ Detection and Real-Time Meat Spoilage Monitoring

by Mingjia Li, Gaoshan Zeng, Haoyue You, Ding Xi, Hui Huang, Xin Kou, Amjad Farid and Yongpeng Zhao

Nanomaterials 2025, 15(13), 987; https://doi.org/10.3390/nano15130987 - 25 Jun 2025

Viewed by 711

Abstract

Recent advancements in biomarker technology have revolutionized diagnostic and monitoring applications, yet their potential in food quality assessment remains largely untapped. Herein, we report a breakthrough in gas-sensitive nanocomposite engineering through the design of α-Fe₂O₃-NiO heterostructures synthesized via a [...] Read more.

Recent advancements in biomarker technology have revolutionized diagnostic and monitoring applications, yet their potential in food quality assessment remains largely untapped. Herein, we report a breakthrough in gas-sensitive nanocomposite engineering through the design of α-Fe₂O₃-NiO heterostructures synthesized via a single-step hydrothermal protocol. The introduction of NiO led to increased oxygen vacancies and active sites, thereby reducing the sensor’s operating temperature. Additionally, the P-N heterojunction structure promoted the redistribution of electrons and hole, thus enhancing its conductivity. The optimized sensor exhibited high sensitivity (75.5% at 100 ppm), fast response/recovery (20 s/92 s), and perfect selectivity for NH₃ at room temperature. In the end, based on this sensor and combined with a Programmable Logic Controller (PLC), a rapid and nondestructive meat spoilage detection system was constructed to reflect the degree of spoilage of meat with the help of NH₃ concentration, providing a valuable strategy for the application of biomarker detection in the food industry. Full article

(This article belongs to the Special Issue Gas-Sensing Properties of Nanomaterials)

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13 pages, 3451 KB

Open AccessArticle

Performance Degradation of Ga₂O₃-Based X-Ray Detector Under Gamma-Ray Irradiation

by Xiao Ouyang, Silong Zhang, Tao Bai, Zhuo Chen, Yuxin Deng, Leidang Zhou, Xiaojing Song, Hao Chen, Yuru Lai, Xing Lu, Liang Chen, Liangliang Miao and Xiaoping Ouyang

Micromachines 2025, 16(3), 339; https://doi.org/10.3390/mi16030339 - 14 Mar 2025

Cited by 5 | Viewed by 1041

Abstract

X-ray response performances of a p-NiO/β-Ga₂O₃ hetero-junction diode (HJD) X-ray detector were studied before and after γ-ray irradiation at −200 V, with a total dose of 13.5 kGy(Si). The response performances of the HJD X-ray detector were influenced [...] Read more.

X-ray response performances of a p-NiO/β-Ga₂O₃ hetero-junction diode (HJD) X-ray detector were studied before and after γ-ray irradiation at −200 V, with a total dose of 13.5 kGy(Si). The response performances of the HJD X-ray detector were influenced by the trap-assistant conductive process of the HJD under reverse bias, which exhibited an increasing net (response) current, nonlinearity, and a long response time. After irradiation, the Poole–Frenkel emission (PFE) dominated the leakage current of HJDs due to the higher electric field caused by the increased net carrier concentration of β-Ga₂O₃. This conductive process weakened the performance of the HJD X-ray detector in terms of sensitivity, output linearity, and response speed. This study provided valuable insights into the radiation damage and performance degradation mechanisms of Ga₂O₃-based radiation detectors and offered guidance on improving the reliability and stability of these radiation detectors. Full article

(This article belongs to the Special Issue High-Reliability Semiconductor Devices and Integrated Circuits, 3rd Edition)

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15 pages, 3775 KB

Open AccessArticle

An Environmental Engineering Study Case: Constructing Cataluminescence Sensors Based on Octahedral Nanocomposites for Isovaleraldehyde Detection

by Bai Sun, Mao Cai, Guoji Shi, Yun Wang, Lining Bao, Qiang Zhao, Mingjian Yi and Shuguang Zhu

Molecules 2025, 30(3), 646; https://doi.org/10.3390/molecules30030646 - 1 Feb 2025

Cited by 1 | Viewed by 963

Abstract

Isovaleraldehyde is an important chemical raw material for the production of flavors, which is volatile and flammable and poses a health risk to humans. It is, therefore, essential to develop a rapid assay for the identification of isovaleraldehyde. In this study, octahedral NiCo [...] Read more.

Isovaleraldehyde is an important chemical raw material for the production of flavors, which is volatile and flammable and poses a health risk to humans. It is, therefore, essential to develop a rapid assay for the identification of isovaleraldehyde. In this study, octahedral NiCo₂O₄/MIL-Fe₅₃ nanocomposites were successfully fabricated for the rapid detection of isovaleraldehyde. The prepared NiCo₂O₄/MIL-Fe₅₃ nanocomposites were characterized by SEM, XRD, FTIR, and XPS to analyze the material properties. The effects of temperature, carrier gas flow rate, selectivity, and stability on the cataluminescence performance of this sensor were investigated. The results showed that NiCo₂O₄/MIL-Fe₅₃ nanocomposites have excellent selectivity to isovaleraldehyde with response and recovery times of 6 and 8 s, respectively. A linear relationship was found between the CTL signal and isovaleraldehyde concentration Y = 9.56X − 23.3 (R² = 0.99) over the concentration range of 13.66 to 437.22 ppm with a detection limit of 2.44 ppm. The relative deviation RSD = 4.18% for multiple tests of the sensor indicates good stability and longevity. Mechanistic studies have shown that the heterojunction formed by NiCo₂O₄/MIL-Fe₅₃ nanocomposites has the advantage of improving CTL sensing performance. This study may advance the application of cataluminescence sensors in the detection of isovaleraldehyde. Full article

(This article belongs to the Special Issue Nano-Functional Materials for Sensor Applications—2nd Edition)

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13 pages, 7956 KB

Open AccessArticle

Construction of Electrospun ZnO-NiO Nanofibers for Enhanced Ethanol Gas Sensing

by Maryam Bonyani, Seyed Mojtaba Zebarjad, Tae-Un Kim, Hyoun Woo Kim and Sang Sub Kim

Sensors 2024, 24(23), 7450; https://doi.org/10.3390/s24237450 - 22 Nov 2024

Cited by 4 | Viewed by 1453

Abstract

Semiconducting metal oxides with nanofiber (NF) morphologies are among the most promising materials for the realization of gas sensors. In this study, we have prepared electrospun ZnO-NiO composite NFs with different amounts of NiO (0, 20, 40, 60 and 80% wt%) for the [...] Read more.

Semiconducting metal oxides with nanofiber (NF) morphologies are among the most promising materials for the realization of gas sensors. In this study, we have prepared electrospun ZnO-NiO composite NFs with different amounts of NiO (0, 20, 40, 60 and 80% wt%) for the systematic study of ethanol gas sensing. The fabricated composite NFs were annealed at 600 °C for crystallization. Based on characterization studies, NFs were produced with desired morphologies, phases, and chemical compositions. Ethanol gas sensing studies revealed that the sensor with 40 wt% NiO had the highest response (3.6 to 10 ppm ethanol) at 300 °C among all gas sensors. The enhanced gas response was ascribed to the formation of sufficient amounts of p-n NiO-ZnO heterojunctions, NFs’ high surface areas due to their one-dimensional morphologies, and acid–base interactions between ZnO and ethanol. This research highlights the need for the optimization of ZnO-NiO composite NFs so that they achieve the highest sensing response, which can be extended to other similar metal oxides. Full article

(This article belongs to the Special Issue (Electro)chemical and Optical (Bio)sensing Devices for Decentralized Cost-Effective (Bio)chemical Monitoring)

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13 pages, 3314 KB

Open AccessArticle

Nonaqueous Synthesis of Pd/PdO-Functionalized NiFe₂O₄ Nanoparticles Enabled Enhancing n-Butanol Detection

by Hongyang Wu and Chen Chen

Nanomaterials 2024, 14(14), 1188; https://doi.org/10.3390/nano14141188 - 12 Jul 2024

Cited by 4 | Viewed by 1360

Abstract

The efficient detection of n-butanol, which is in demand for highly sensitive materials, is essential for multiple applications. A nonaqueous method was applied to prepare NiFe₂O₄ nanoparticles (NPs) using benzyl alcohol as a solvent, which shows a size of 7.9 [...] Read more.

The efficient detection of n-butanol, which is in demand for highly sensitive materials, is essential for multiple applications. A nonaqueous method was applied to prepare NiFe₂O₄ nanoparticles (NPs) using benzyl alcohol as a solvent, which shows a size of 7.9 ± 1.6 nm and a large surface area of 82.23 m²/g. To further improve the sensing performance for n-butanol, Pd/PdO functionalization was sensitized with NiFe₂O₄ NPs. Gas sensing results demonstrate that the Pd/PdO-NiFe₂O₄ exhibits an enhanced response of 36.9 to 300 ppm n-butanol and a fast response and recovery time (18.2/17.6 s) at 260 °C. Furthermore, the Pd/PdO-NiFe₂O₄-based sensor possesses a good linear relationship between responses and the n-butanol concentration from 1 to 1000 ppm, and great selectivity against other volatile organic compounds (VOCs). The excellent sensing enhancement is attributed to the catalytic effects of Pd/PdO, the increase of oxygen vacancies, and the formation of heterojunction between PdO and NiFe₂O₄. Thus, this study offers an effective route for the synthesis of Pd/PdO-functionalized NiFe₂O₄ NPs to achieve n-butanol detection with excellent sensing performance. Full article

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12 pages, 6562 KB

Open AccessArticle

Synthesis of Fe₂O₃ Nanorod and NiFe₂O₄ Nanoparticle Composites on Expired Cotton Fiber Cloth for Enhanced Hydrogen Evolution Reaction

by Sun Hua, Sayyar Ali Shah, Noor Ullah, Nabi Ullah and Aihua Yuan

Molecules 2024, 29(13), 3082; https://doi.org/10.3390/molecules29133082 - 28 Jun 2024

Cited by 6 | Viewed by 1894

Abstract

The design of cheap, noble-metal-free, and efficient electrocatalysts for an enhanced hydrogen evolution reaction (HER) to produce hydrogen gas as an energy source from water splitting is an ideal approach. Herein, we report the synthesis of Fe₂O₃ nanorods–NiFe₂O [...] Read more.

The design of cheap, noble-metal-free, and efficient electrocatalysts for an enhanced hydrogen evolution reaction (HER) to produce hydrogen gas as an energy source from water splitting is an ideal approach. Herein, we report the synthesis of Fe₂O₃ nanorods–NiFe₂O₄ nanoparticles on cotton fiber cloth (Fe₂O₃-NiFe₂O₄/CF) at a low temperature as an efficient electrocatalyst for HERs. Among the as-prepared samples, the optimal Fe₂O₃-NiFe₂O₄/CF-3 electrocatalyst exhibits good HER performance with an overpotential of 127 mV at a current density of 10 mA cm⁻², small Tafel slope of 44.9 mV dec⁻¹, and good stability in 1 M KOH alkaline solution. The synergistic effect between Fe₂O₃ nanorods and NiFe₂O₄ nanoparticles of the heterojunction composite at the heterointerface is mainly responsible for improved HER performance. The CF is an effective substrate for the growth of the Fe₂O₃-NiFe₂O₄ nanocomposite and provides conductive channels for the active materials’ HER process. Full article

(This article belongs to the Special Issue Development of Nanomaterials for Energy and Environmental Applications)

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12 pages, 4555 KB

Open AccessArticle

Synergistic Effect of ZIF-8 and Pt-Functionalized NiO/In₂O₃ Hollow Nanofibers for Highly Sensitive Detection of Formaldehyde

by Lei Zhu, Ze Wang, Jianan Wang, Jianwei Liu, Wei Zhao, Jiaxin Zhang and Wei Yan

Nanomaterials 2024, 14(10), 841; https://doi.org/10.3390/nano14100841 - 10 May 2024

Cited by 3 | Viewed by 1907

Abstract

A rapid and accurate monitoring of hazardous formaldehyde (HCHO) gas is extremely essential for health protection. However, the high-power consumption and humidity interference still hinder the application of HCHO gas sensors. Hence, zeolitic imidazolate framework-8 (ZIF-8)-loaded Pt-NiO/In₂O₃ hollow nanofibers (ZPNiIn [...] Read more.

A rapid and accurate monitoring of hazardous formaldehyde (HCHO) gas is extremely essential for health protection. However, the high-power consumption and humidity interference still hinder the application of HCHO gas sensors. Hence, zeolitic imidazolate framework-8 (ZIF-8)-loaded Pt-NiO/In₂O₃ hollow nanofibers (ZPNiIn HNFs) were designed via the electrospinning technique followed by hydrothermal treatment, aiming to enable a synergistic advantage of the surface modification and the construction of a p-n heterostructure to improve the sensing performance of the HCHO gas sensor. The ZPNiIn HNF sensor has a response value of 52.8 to 100 ppm HCHO, a nearly 4-fold enhancement over a pristine In₂O₃ sensor, at a moderately low temperature of 180 °C, along with rapid response/recovery speed (8/17 s) and excellent humidity tolerance. These enhanced sensing properties can be attributed to the Pt catalysts boosting the catalytic activity, the p-n heterojunctions facilitating the chemical reaction, and the appropriate ZIF-8 loading providing a hydrophobic surface. Our research presents an effective sensing material design strategy for inspiring the development of cost-effective sensors for the accurate detection of indoor HCHO hazardous gas. Full article

(This article belongs to the Special Issue Nanoscale Material-Based Gas Sensors)

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28 pages, 14874 KB

Open AccessReview

β-Ga₂O₃-Based Heterostructures and Heterojunctions for Power Electronics: A Review of the Recent Advances

by Dinusha Herath Mudiyanselage, Bingcheng Da, Jayashree Adivarahan, Dawei Wang, Ziyi He, Kai Fu, Yuji Zhao and Houqiang Fu

Electronics 2024, 13(7), 1234; https://doi.org/10.3390/electronics13071234 - 27 Mar 2024

Cited by 22 | Viewed by 6464

Abstract

During the past decade, Gallium Oxide (Ga₂O₃) has attracted intensive research interest as an ultra-wide-bandgap (UWBG) semiconductor due to its unique characteristics, such as a large bandgap of 4.5–4.9 eV, a high critical electric field of ~8 MV/cm, and [...] Read more.

During the past decade, Gallium Oxide (Ga₂O₃) has attracted intensive research interest as an ultra-wide-bandgap (UWBG) semiconductor due to its unique characteristics, such as a large bandgap of 4.5–4.9 eV, a high critical electric field of ~8 MV/cm, and a high Baliga’s figure of merit (BFOM). Unipolar β-Ga₂O₃ devices such as Schottky barrier diodes (SBDs) and field-effect transistors (FETs) have been demonstrated. Recently, there has been growing attention toward developing β-Ga₂O₃-based heterostructures and heterojunctions, which is mainly driven by the lack of p-type doping and the exploration of multidimensional device architectures to enhance power electronics’ performance. This paper will review the most recent advances in β-Ga₂O₃ heterostructures and heterojunctions for power electronics, including NiO_x/β-Ga₂O₃, β-(Al_xGa_1−x)₂O₃/β-Ga₂O₃, and β-Ga₂O₃ heterojunctions/heterostructures with other wide- and ultra-wide-bandgap materials and the integration of two-dimensional (2D) materials with β-Ga₂O₃. Discussions of the deposition, fabrication, and operating principles of these heterostructures and heterojunctions and the associated device performance will be provided. This comprehensive review will serve as a critical reference for researchers engaged in materials science, wide- and ultra-wide-bandgap semiconductors, and power electronics and benefits the future study and development of β-Ga₂O₃-based heterostructures and heterojunctions and associated power electronics. Full article

(This article belongs to the Special Issue Young Investigators in Electronics)

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17 pages, 8020 KB

Open AccessArticle

Heterojunction Devices Fabricated from Sprayed n-Type Ga₂O₃, Combined with Sputtered p-Type NiO and Cu₂O

by Theodoros Dimopoulos, Rachmat Adhi Wibowo, Stefan Edinger, Maximilian Wolf and Thomas Fix

Nanomaterials 2024, 14(3), 300; https://doi.org/10.3390/nano14030300 - 1 Feb 2024

Cited by 4 | Viewed by 2621

Abstract

This work reports on the properties of heterojunctions consisting of n-type Ga₂O₃ layers, deposited using ultrasonic spray pyrolysis at high temperature from water-based solution, combined with p-type NiO and Cu₂O counterparts, deposited by radio frequency and [...] Read more.

This work reports on the properties of heterojunctions consisting of n-type Ga₂O₃ layers, deposited using ultrasonic spray pyrolysis at high temperature from water-based solution, combined with p-type NiO and Cu₂O counterparts, deposited by radio frequency and reactive, direct-current magnetron sputtering, respectively. After a comprehensive investigation of the properties of the single layers, the fabricated junctions on indium tin oxide (ITO)-coated glass showed high rectification, with an open circuit voltage of 940 mV for Ga₂O₃/Cu₂O and 220 mV for Ga₂O₃/NiO under simulated solar illumination. This demonstrates in praxis the favorable band alignment between the sprayed Ga₂O₃ and Cu₂O, with small conduction band offset, and the large offsets anticipated for both energy bands in the case of Ga₂O₃/NiO. Large differences in the ideality factors between the two types of heterojunctions were observed, suggestive of distinctive properties of the heterointerface. Further, it is shown that the interface between the high-temperature-deposited Ga₂O₃ and the ITO contact does not impede electron transport, opening new possibilities for the design of solar cell and optoelectronic device architectures. Full article

(This article belongs to the Topic Advances in Functional Thin Films)

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18 pages, 14269 KB

Open AccessArticle

H₂S/Butane Dual Gas Sensing Based on a Hydrothermally Synthesized MXene Ti₃C₂T_x/NiCo₂O₄ Nanocomposite

by Shama Sadaf, Hongpeng Zhang and Ali Akhtar

Molecules 2024, 29(1), 202; https://doi.org/10.3390/molecules29010202 - 29 Dec 2023

Cited by 2 | Viewed by 1790

Abstract

Real-time sensing of hydrogen sulfide (H₂S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene Ti₃C₂T_x, Ti₃AlC₂, WS [...] Read more.

Real-time sensing of hydrogen sulfide (H₂S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene Ti₃C₂T_x, Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄, were synthesized using the hydrothermal method in this paper. Initially, the intrinsic properties of the synthesized nanocomposites were studied using different techniques. P-type butane and H₂S-sensing behaviors of nanocomposites were performed and analyzed deeply. Four sensor sheets were fabricated using a spin-coating method. The gas sensor was distinctly part of the chemiresistor class. The MXene Ti₃C₂T_x/NiCo₂O₄-based gas sensor detected the highest response (16) toward 10 ppm H₂S at room temperature. In comparison, the sensor detected the highest response (9.8) toward 4000 ppm butane at 90 °C compared with the other three fabricated sensors (Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄). The MXene Ti₃C₂T_x/NiCo₂O₄ sensor showed excellent responses, minimum limits of detection (0.1 ppm H₂S and 5 ppm butane), long-term stability, and good reproducibility compared with the other fabricated sensors. The highest sensing properties toward H₂S and butane were accredited to p–p heterojunctions, higher BET surface areas, increased oxygen species, etc. These simply synthesized nanocomposites and fabricated sensors present a novel method for tracing H₂S and butane at the lowest concentration to prevent different gas-exposure-related diseases. Full article

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11 pages, 1688 KB

Open AccessArticle

Impact of Solid-State Charge Injection on Spectral Photoresponse of NiO/Ga₂O₃ p–n Heterojunction

by Alfons Schulte, Sushrut Modak, Yander Landa, Atman Atman, Jian-Sian Li, Chao-Ching Chiang, Fan Ren, Stephen J. Pearton and Leonid Chernyak

Condens. Matter 2023, 8(4), 106; https://doi.org/10.3390/condmat8040106 - 2 Dec 2023

Cited by 1 | Viewed by 2606

Abstract

Forward bias hole injection from 10-nm-thick p-type nickel oxide layers into 10-μm-thick n-type gallium oxide in a vertical NiO/Ga₂O₃ p–n heterojunction leads to enhancement of photoresponse of more than a factor of 2 when measured from this junction. While it [...] Read more.

Forward bias hole injection from 10-nm-thick p-type nickel oxide layers into 10-μm-thick n-type gallium oxide in a vertical NiO/Ga₂O₃ p–n heterojunction leads to enhancement of photoresponse of more than a factor of 2 when measured from this junction. While it takes only 600 s to obtain such a pronounced increase in photoresponse, it persists for hours, indicating the feasibility of photovoltaic device performance control. The effect is ascribed to a charge injection-induced increase in minority carrier (hole) diffusion length (resulting in improved collection of photogenerated non-equilibrium carriers) in n-type β-Ga₂O₃ epitaxial layers due to trapping of injected charge (holes) on deep meta-stable levels in the material and the subsequent blocking of non-equilibrium carrier recombination through these levels. Suppressed recombination leads to increased non-equilibrium carrier lifetime, in turn determining a longer diffusion length and being the root-cause of the effect of charge injection. Full article

(This article belongs to the Special Issue Wide-Band-Gap Semiconductors for Energy and Electronics)

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