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Yang G, Kim Y, Jeon J, Lee M, Kim D, Kim S, Eom K, Lee H. Reversible Photomodulation of Two-Dimensional Electron Gas in LaAlO 3/SrTiO 3 Heterostructures. NANO LETTERS 2023. [PMID: 37418557 DOI: 10.1021/acs.nanolett.3c01076] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/09/2023]
Abstract
Long-lived photoinduced conductance changes in LaAlO3/SrTiO3 (LAO/STO) heterostructures enable their use in optoelectronic memory applications. However, it remains challenging to quench the persistent photoconductivity (PPC) instantly and reproducibly, which limits the reversible optoelectronic switching. Herein, we demonstrate a reversible photomodulation of two-dimensional electron gas (2DEG) in LAO/STO heterostructures with high reproducibility. By irradiating UV pulses, the 2DEG at the LAO/STO interface is gradually transformed to the PPC state. Notably, the PPC can be completely removed by water treatment when two key requirements are met: (1) the moderate oxygen deficiency in STO and (2) the minimal band edge fluctuation at the interface. Through our X-ray photoelectron spectroscopy and electrical noise analysis, we reveal that the reproducible change in the conductivity of 2DEG is directly attributed to the surface-driven electron relaxation in the STO. Our results provide a stepping-stone toward developing optically tunable memristive devices based on oxide 2DEG systems.
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Affiliation(s)
- Gyeongmo Yang
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Youngmin Kim
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Jaeyoung Jeon
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Minkyung Lee
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Doyeop Kim
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Sungkyu Kim
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea
| | - Kitae Eom
- School of Advanced Materials science and Engineering, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Hyungwoo Lee
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
- Department of Physics, Ajou University, Suwon 16499, Republic of Korea
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2
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Jeon J, Eom K, Hong Y, Eom CB, Heo K, Lee H. Hot Electron Tunneling in Pt/LaAlO 3/SrTiO 3 Heterostructures for Enhanced Photodetection. ACS APPLIED MATERIALS & INTERFACES 2021; 13:47208-47217. [PMID: 34553900 DOI: 10.1021/acsami.1c12394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
LaAlO3/SrTiO3 (LAO/STO) heterostructures, in which a highly mobile two-dimensional electron gas (2DEG) is formed, have great potential for optoelectronic applications. However, the inherently high density of the 2DEG hinders the observation of photo-excitation effects in oxide heterostructures. Herein, a strong photoresponse of the 2DEG in a Pt/LAO/STO heterostructure is achieved by adopting a vertical tunneling configuration. The tunneling of the 2DEG through an ultrathin LAO layer is significantly enhanced by UV light irradiation, showing a maximum photoresponsivity of ∼1.11 × 107%. The strong and reversible photoresponse is attributed to the thermionic emission of photoexcited hot electrons from the oxygen-deficient STO. Notably, the oxygen vacancy defects play a critical role in enhancing the tunneling photocurrent. Our systematic study on the hysteresis behavior and the light power dependency of the tunneling current consistently support the fact that the photoexcited hot electrons from the oxygen vacancies strongly contribute to the tunneling conduction under the UV light. This work offers valuable insights into a novel photodetection mechanism based on the 2DEG as well as into developing ultrathin optoelectronic devices based on the oxide heterostructures.
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Affiliation(s)
- Jaeyoung Jeon
- Department of Physics, Ajou University, Suwon 16499, Republic of Korea
| | - Kitae Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Yunhwa Hong
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Kwang Heo
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea
- Hybrid Materials Research Center (HMC), Sejong University, Seoul 05006, Republic of Korea
| | - Hyungwoo Lee
- Department of Physics, Ajou University, Suwon 16499, Republic of Korea
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
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3
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Halder AK, Melo A, Cordeiro MNDS. A unified in silico model based on perturbation theory for assessing the genotoxicity of metal oxide nanoparticles. CHEMOSPHERE 2020; 244:125489. [PMID: 31812055 DOI: 10.1016/j.chemosphere.2019.125489] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/19/2019] [Accepted: 11/26/2019] [Indexed: 06/10/2023]
Abstract
Nanomaterials (NMs) are an ever-increasing field of interest, due to their wide range of applications in science and technology. However, despite providing solutions to many societal problems and challenges, NMs are associated with adverse effects with potential severe damages towards biological species and their ecosystems. Particularly, it has been confirmed that NMs may induce serious genotoxic effects on various biological targets. Given the difficulties of experimental assays for estimating the genotoxicity of many NMs on diverse biological targets, development of alternative methodologies is crucial to establish their level of safety. In silico modelling approaches, such as Quantitative Structure-Toxicity Relationships (QSTR), are now considered a promising solution for such purpose. In this work, a perturbation theory machine learning (PTML) based QSTR approach is proposed for predicting the genotoxicity of metal oxide NMs under various experimental assay conditions. The application of such perturbation approach to 6084 NM-NM pair cases, set up from 78 unique NMs, afforded a final PTML-QSTR model with an accuracy better than 96% for both training and test sets. This model was then used to predict the genotoxicity of some NMs not included in the modelling dataset. The results for this independent data set were in excellent agreement with the experimental ones. Overall, that thus suggests that the derived PTML-QSTR model is a reliable in silico tool to rapidly and cost-efficiently assess the genotoxicity of metal oxide NMs. Finally, and most importantly, the model provides important insights regarding the mechanism of the genotoxicity triggered by these NMs.
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Affiliation(s)
- Amit Kumar Halder
- LAQV@REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007, Porto, Portugal.
| | - André Melo
- LAQV@REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007, Porto, Portugal
| | - M Natália D S Cordeiro
- LAQV@REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007, Porto, Portugal.
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4
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Yan H, Zhang Z, Li M, Wang S, Ren L, Jin K. Photoresponsive properties at (0 0 1), (1 1 1) and (1 1 0) LaAlO 3/SrTiO 3 interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:135002. [PMID: 31801125 DOI: 10.1088/1361-648x/ab5ebf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report the photoresponsive characteristics of (0 0 1), (1 1 0), and (1 1 1) LaAlO3/SrTiO3 heterointerfaces deposited at different oxygen pressures using a 360 nm light. The results show that LaAlO3/SrTiO3 interfaces with less oxygen vacancies exhibit a larger resistance change when illuminated by light and a slower recovery process when light is off. In addition, the (1 1 0) LaAlO3/SrTiO3 heterointerfaces present the smallest photoinduced change and residual photoinduced change in the resistance, which are related to the negligible polarization discontinuity at the interfaces. Our results provide a deeper insight into the photoinduced properties in the 2D electron gas system, paving the way for the design of oxide optoelectronic devices.
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Affiliation(s)
- Hong Yan
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Science, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
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Zeeshan HM, Butt MK, Iqbal MA, Wang S, Ren L, Jin K. Revealing the Photocharge-Transfer Mechanism at Manganite-Buffered LaAlO 3/SrTiO 3 Interfaces by Giant Photoresponse. ACS APPLIED MATERIALS & INTERFACES 2020; 12:11197-11203. [PMID: 32028768 DOI: 10.1021/acsami.9b22162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The photoinduced phase transition at complex oxides remains one of the very important issues because of the emergent physics and potential applications. In particular, the mechanism of charge transfer at interfaces under irradiation is challenging. Herein, the photoinduced properties of manganite-buffered LaAlO3/SrTiO3 interfaces with different thicknesses of the buffer layer are systematically investigated. The giant photoresponse is observed, and its relative change in resistance is about 6.24 × 106% at T = 20 K for the sample with a buffer layer thickness of 4.8 nm. Moreover, the transition temperature is enhanced by increasing the thickness of the buffer layer. More importantly, the dead layer effect at the interfaces has been suppressed by using light. All these results are attributed to the charge transfer because of the octahedral tilting at low temperatures and provide a new kind of oxide-based optical devices, such as ultraviolet detectors. This piece of work will pave the way toward two-dimensional electron gas-based optoelectronic devices.
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Affiliation(s)
- Hafiz M Zeeshan
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - Mehwish K Butt
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - Muhammad A Iqbal
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - Shuanhu Wang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - Lixia Ren
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - Kexin Jin
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
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6
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Zhang F, Lv P, Zhang Y, Huang S, Wong CM, Yau HM, Chen X, Wen Z, Jiang X, Zeng C, Hong J, Dai JY. Modulating the Electrical Transport in the Two-Dimensional Electron Gas at LaAlO_{3}/SrTiO_{3} Heterostructures by Interfacial Flexoelectricity. PHYSICAL REVIEW LETTERS 2019; 122:257601. [PMID: 31347866 DOI: 10.1103/physrevlett.122.257601] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 04/12/2019] [Indexed: 06/10/2023]
Abstract
Thin film flexoelectricity is attracting more attention because of its enhanced effect and potential application in electronic devices. Here we find that a mechanical bending induced flexoelectricity significantly modulates the electrical transport properties of the interfacial two-dimensional electron gas (2DEG) at the LaAlO_{3}/SrTiO_{3} (LAO/STO) heterostructure. Under variant bending states, both the carrier density and mobility of the 2DEG are changed according to the flexoelectric polarization direction, showing an electric field effect modulation. By measuring the flexoelectric response of LAO, it is found that the effective flexoelectricity in the LAO thin film is enhanced by 3 orders compared to its bulk. These results broaden the horizon of study on the flexoelectricity effect in the hetero-oxide interface and more research on the oxide interfacial flexoelectricity may be stimulated.
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Affiliation(s)
- Fan Zhang
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Peng Lv
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Yiteng Zhang
- College of Physics, Qingdao University, Qingdao, 266071, China
| | - Shujin Huang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Chi-Man Wong
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Hei-Man Yau
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Xinxin Chen
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Zheng Wen
- College of Physics, Qingdao University, Qingdao, 266071, China
| | - Xiaoning Jiang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials, Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Jiawang Hong
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Ji-Yan Dai
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
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7
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Yan H, Zhang Z, Wang S, Wei X, Chen C, Jin K. Magnetism Control by Doping in LaAlO 3/SrTiO 3 Heterointerfaces. ACS APPLIED MATERIALS & INTERFACES 2018; 10:14209-14213. [PMID: 29619833 DOI: 10.1021/acsami.8b03275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Magnetic two-dimensional electron gases at the oxide interfaces are always one of the key issues in spintronics, giving rise to intriguing magnetotransport properties. However, reports about magnetic two-dimensional electron gases remain elusive. Here, we obtain the magnetic order of LaAlO3/SrTiO3 systems by introducing magnetic dopants at the La site. The transport properties with a characteristic of metallic behavior at the interfaces are investigated. More significantly, magnetic-doped samples exhibit obvious magnetic hysteresis loops and the mobility is enhanced. Meanwhile, the photoresponsive experiments are realized by irradiating all samples with a 360 nm light. Compared to magnetism, the effects of dopants on photoresponsive and relaxation properties are negligible because the behavior originates from SrTiO3 substrates. This work paves a way for revealing and better controlling the magnetic properties of oxide heterointerfaces.
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Affiliation(s)
- Hong Yan
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science , Northwestern Polytechnical University , Xi'an 710072 , China
| | - Zhaoting Zhang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science , Northwestern Polytechnical University , Xi'an 710072 , China
| | - Shuanhu Wang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science , Northwestern Polytechnical University , Xi'an 710072 , China
| | - Xiangyang Wei
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science , Northwestern Polytechnical University , Xi'an 710072 , China
| | - Changle Chen
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science , Northwestern Polytechnical University , Xi'an 710072 , China
| | - Kexin Jin
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science , Northwestern Polytechnical University , Xi'an 710072 , China
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8
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Yan H, Zhang Z, Wang S, Zhang H, Chen C, Jin K. Modulated Transport Behavior of Two-Dimensional Electron Gas at Ni-Doped LaAlO 3/SrTiO 3 Heterointerfaces. ACS APPLIED MATERIALS & INTERFACES 2017; 9:39011-39017. [PMID: 29034682 DOI: 10.1021/acsami.7b11727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Modulating transport behaviors of two-dimensional electron gases are of critical importance for applications of the next-generation multifunctional oxide electronics. In this study, transport behaviors of LaAlO3/SrTiO3 heterointerfaces modified through the Ni dopant and the light irradiation have been investigated. Through the Ni dopant, the resistances increase significantly and a resistance upturn phenomenon due to the Kondo effect is observed at T < 40 K. Under a 360 nm light irradiation, the interfaces exhibit a persistent photoconductivity and a suppressed Kondo effect at low temperature due to the increased mobility measured through the photo-Hall method. Moreover, the relative changes in resistance of interfaces induced by light are increased from 800 to 6600% at T = 12 K with increasing the substitution of Ni, which is discussed by the band bending and the lattice effect due to the Ni dopant. This work paves the way for better controlling the emerging properties of complex oxide heterointerfaces and would be helpful for photoelectric device applications based on all-oxides.
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Affiliation(s)
- Hong Yan
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University , Xi'an 710072, China
| | - Zhaoting Zhang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University , Xi'an 710072, China
| | - Shuanhu Wang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University , Xi'an 710072, China
| | - Hongrui Zhang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University , Xi'an 710072, China
| | - Changle Chen
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University , Xi'an 710072, China
| | - Kexin Jin
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University , Xi'an 710072, China
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9
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Concu R, Kleandrova VV, Speck-Planche A, Cordeiro MNDS. Probing the toxicity of nanoparticles: a unified in silico machine learning model based on perturbation theory. Nanotoxicology 2017; 11:891-906. [PMID: 28937298 DOI: 10.1080/17435390.2017.1379567] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nanoparticles (NPs) are part of our daily life, having a wide range of applications in engineering, physics, chemistry, and biomedicine. However, there are serious concerns regarding the harmful effects that NPs can cause to the different biological systems and their ecosystems. Toxicity testing is an essential step for assessing the potential risks of the NPs, but the experimental assays are often very expensive and usually too slow to flag the number of NPs that may cause adverse effects. In silico models centered on quantitative structure-activity/toxicity relationships (QSAR/QSTR) are alternative tools that have become valuable supports to risk assessment, rationalizing the search for safer NPs. In this work, we develop a unified QSTR-perturbation model based on artificial neural networks, aimed at simultaneously predicting general toxicity profiles of NPs under diverse experimental conditions. The model is derived from 54,371 NP-NP pair cases generated by applying the perturbation theory to a set of 260 unique NPs, and showed an accuracy higher than 97% in both training and validation sets. Physicochemical interpretation of the different descriptors in the model are additionally provided. The QSTR-perturbation model is then employed to predict the toxic effects of several NPs not included in the original dataset. The theoretical results obtained for this independent set are strongly consistent with the experimental evidence found in the literature, suggesting that the present QSTR-perturbation model can be viewed as a promising and reliable computational tool for probing the toxicity of NPs.
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Affiliation(s)
- Riccardo Concu
- a LAQV@REQUIMTE/Department of Chemistry and Biochemistry, Faculty of Sciences , University of Porto , Porto , Portugal
| | - Valeria V Kleandrova
- b Faculty of Technology and Production Management , Moscow State University of Food Production , Moscow , Russia
| | - Alejandro Speck-Planche
- a LAQV@REQUIMTE/Department of Chemistry and Biochemistry, Faculty of Sciences , University of Porto , Porto , Portugal
| | - M Natália D S Cordeiro
- a LAQV@REQUIMTE/Department of Chemistry and Biochemistry, Faculty of Sciences , University of Porto , Porto , Portugal
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10
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Saha A, Viswanatha R. Magnetism at the Interface of Magnetic Oxide and Nonmagnetic Semiconductor Quantum Dots. ACS NANO 2017; 11:3347-3354. [PMID: 28260377 DOI: 10.1021/acsnano.7b00711] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Engineering interfaces specifically in quantum dot (QD) heterostructures provide several prospects for developing multifunctional building block materials. Precise control over internal structure by chemical synthesis offers a combination of different properties in QDs and allows us to study their fundamental properties, depending on their structure. Herein, we studied the interface of magnetic/nonmagnetic Fe3O4/CdS QD heterostructures. In this work, we demonstrate the decrease in the size of the magnetic core due to annealing at high temperature by the decrease in saturation magnetization and blocking temperature. Furthermore, surprisingly, in a prominently optically active and magnetically inactive material such as CdS, we observe the presence of substantial exchange bias in spite of the nonmagnetic nature of CdS QDs. The presence of exchange bias was proven by the increase in magnetic anisotropy as well as the presence of exchange bias field (HE) during the field-cooled magnetic measurements. This exchange coupling was eventually traced to the in situ formation of a thin antiferromagnetic FeS layer at the interface. This is verified by the study of Fe local structure using X-ray absorption fine structure spectroscopy, demonstrating the importance of interface engineering in QDs.
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Affiliation(s)
- Avijit Saha
- New Chemistry Unit and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560064, India
| | - Ranjani Viswanatha
- New Chemistry Unit and ‡International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bangalore 560064, India
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11
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Mesoporous WN/WO3-Composite Nanosheets for the Chemiresistive Detection of NO2 at Room Temperature. INORGANICS 2016. [DOI: 10.3390/inorganics4030024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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V A, Kumar P, Pal P, Dogra A. Photo-resistive properties of LaAl0.6Cr0.4O3/SrTiO3 heterostructures: a comparative study with LaAlO3/SrTiO3. OPTICS LETTERS 2016; 41:1134-1137. [PMID: 26977652 DOI: 10.1364/ol.41.001134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report photoconductivity measurements on LaAl(1-x)Cr(x)O3/SrTiO3 (x=0, 0.4) heterostructures. A polar layer modification of metallic LaAlO3/SrTiO3 heterostructure with Cr in the Al sites resulted in an increased photo-response (PR) and relaxation time, in addition to a distinct shift in the spectral weight toward the red end of the spectrum. The visible light photoconductivity is explained by d-d photoconductivity of Cr3+ valence states of the x=0.4 sample. Besides the established UV sensitivity, we observe a weak peak in PR around 690 nm possibly emanating from the mid-gap states arising from oxygen vacancies.
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Evidence for lattice-polarization-enhanced field effects at the SrTiO3-based heterointerface. Sci Rep 2016; 6:22418. [PMID: 26926433 PMCID: PMC4772472 DOI: 10.1038/srep22418] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/15/2016] [Indexed: 11/08/2022] Open
Abstract
Electrostatic gating provides a powerful approach to tune the conductivity of the two-dimensional electron liquid between two insulating oxides. For the LaAlO3/SrTiO3 (LAO/STO) interface, such gating effect could be further enhanced by a strong lattice polarization of STO caused by simultaneous application of gate field and illumination light. Herein, by monitoring the discharging process upon removing the gate field, we give firm evidence for the occurrence of this lattice polarization at the amorphous-LaAlO3/SrTiO3 interface. Moreover, we find that the lattice polarization is accompanied with a large expansion of the out-of-plane lattice of STO. Photo excitation affects the polarization process by accelerating the field-induced lattice expansion. The present work demonstrates the great potential of combined stimuli in exploring emergent phenomenon at complex oxide interfaces.
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Lin JC, Tra VT, Tsai DS, Lin TT, Huang PC, Hsu WL, Wu HJ, Huang R, Van Chien N, Yoshida R, Lin JY, Ikuhara Y, Chiu YP, Gwo S, Tsai DP, He JH, Chu YH. Control of the Metal-Insulator Transition at Complex Oxide Heterointerfaces through Visible Light. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:764-770. [PMID: 26607052 DOI: 10.1002/adma.201503499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 10/14/2015] [Indexed: 06/05/2023]
Abstract
The coupling of the localized surface plasmon resonance of Au nanoparticles is utilized to deliver a visible-light stimulus to control conduction at the LaAlO3 /SrTiO3 interface. A giant photoresponse and the controllable metal-insulator transition are characterized at this heterointerface. This study paves a new route to optical control of the functionality at the heterointerfaces.
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Affiliation(s)
- Jheng-Cyuan Lin
- Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan
| | - Vu Thanh Tra
- Institute of Physics, National Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Dung-Sheng Tsai
- Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Taipei, 11529, Taiwan
| | - Tai-Te Lin
- Department of Physics, National Sun Yat-sen University, Kaohsiung, 804, Taiwan
| | - Po-Cheng Huang
- Department of Physics, National Sun Yat-sen University, Kaohsiung, 804, Taiwan
| | - Wei-Lun Hsu
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - Hui Jun Wu
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - Rong Huang
- Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai, 200062, China
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, 456-8587, Japan
| | - Nguyen Van Chien
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Ryuji Yoshida
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, 456-8587, Japan
| | - Jiunn-Yuan Lin
- Institute of Physics, National Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Yuichi Ikuhara
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, 456-8587, Japan
- Institute of Engineering Innovation, The University of Tokyo, Tokyo, 113-8656, Japan
| | - Ya-Ping Chiu
- Department of Physics, National Sun Yat-sen University, Kaohsiung, 804, Taiwan
- Department of Physics, National Taiwan Normal University, Taipei, 116, Taiwan
| | - Shangjr Gwo
- Department of Physics, National Tsing-Hua University, Hsinchu, 30013, Taiwan
| | - Din Ping Tsai
- Research Center for Applied Sciences, Academia Sinica, Taipei, 11529, Taiwan
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - Jr-Hau He
- Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617, Taiwan
- Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Ying-Hao Chu
- Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 30010, Taiwan
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15
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Fang H, Lin Z, Wang X, Tang CY, Chen Y, Zhang F, Chai Y, Li Q, Yan Q, Chan HLW, Dai JY. Infrared light gated MoS₂ field effect transistor. OPTICS EXPRESS 2015; 23:31908-31914. [PMID: 26698982 DOI: 10.1364/oe.23.031908] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Molybdenum disulfide (MoS₂) as a promising 2D material has attracted extensive attentions due to its unique physical, optical and electrical properties. In this work, we demonstrate an infrared (IR) light gated MoS₂ transistor through a device composed of MoS₂ monolayer and a ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O₃-PbTiO₃ (PMN-PT). With a monolayer MoS₂ onto the top surface of (111) PMN-PT crystal, the drain current of MoS₂ channel can be modulated with infrared illumination and this modulation process is reversible. Thus, the transistor can work as a new kind of IR photodetector with a high IR responsivity of 114%/Wcm⁻². The IR response of MoS₂ transistor is attributed to the polarization change of PMN-PT single crystal induced by the pyroelectric effect which results in a field effect. Our result promises the application of MoS₂ 2D material in infrared optoelectronic devices. Combining with the intrinsic photocurrent feature of MoS₂ in the visible range, the MoS₂ on ferroelectric single crystal may be sensitive to a broadband wavelength of light.
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16
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Speck-Planche A, Kleandrova VV, Luan F, Cordeiro MNDS. Computational modeling in nanomedicine: prediction of multiple antibacterial profiles of nanoparticles using a quantitative structure-activity relationship perturbation model. Nanomedicine (Lond) 2015; 10:193-204. [PMID: 25600965 DOI: 10.2217/nnm.14.96] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
AIMS We introduce the first quantitative structure-activity relationship (QSAR) perturbation model for probing multiple antibacterial profiles of nanoparticles (NPs) under diverse experimental conditions. MATERIALS & METHODS The dataset is based on 300 nanoparticles containing dissimilar chemical compositions, sizes, shapes and surface coatings. In general terms, the NPs were tested against different bacteria, by considering several measures of antibacterial activity and diverse assay times. The QSAR perturbation model was created from 69,231 nanoparticle-nanoparticle (NP-NP) pairs, which were randomly generated using a recently reported perturbation theory approach. RESULTS The model displayed an accuracy rate of approximately 98% for classifying NPs as active or inactive, and a new copper-silver nanoalloy was correctly predicted by this model with consensus accuracy of 77.73%. CONCLUSION Our QSAR perturbation model can be used as an efficacious tool for the virtual screening of antibacterial nanomaterials.
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Affiliation(s)
- Alejandro Speck-Planche
- REQUIMTE/Department of Chemistry & Biochemistry, University of Porto, 4169-007 Porto, Portugal
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17
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Jin KX, Lin W, Luo BC, Wu T. Photoinduced modulation and relaxation characteristics in LaAlO3/SrTiO3 heterointerface. Sci Rep 2015; 5:8778. [PMID: 25739889 PMCID: PMC4350088 DOI: 10.1038/srep08778] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/03/2015] [Indexed: 11/21/2022] Open
Abstract
We report the modulation and relaxation characteristics in the two-dimensional electron gas system at LaAlO3/SrTiO3 heterointerface induced by the ultraviolet light illumination (365 nm). The suppression of Kondo effect at the interface illuminated by the light originates from the light irradiation-induced decoherence effect of localized states. It is interesting to note that the persistent and transient photoinduced effects are simultaneously observed and the photoinduced maximum change values in resistance are 80.8% and 51.4% at T = 20 K, respectively. Moreover, the photoinduced relaxation processes after the irradiation are systematically analyzed using the double exponential model. These results provide the deeper understanding of the photoinduced effect and the experimental evidence of tunable Kondo effect in oxides-based two-dimensional electron gas systems.
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Affiliation(s)
- K X Jin
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - W Lin
- Materials Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - B C Luo
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
| | - T Wu
- Materials Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
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18
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Kim H, Chan NY, Dai JY, Kim DW. Enhanced surface-and-interface coupling in Pd-nanoparticle-coated LaAlO3/SrTiO3 heterostructures: strong gas- and photo-induced conductance modulation. Sci Rep 2015; 5:8531. [PMID: 25704566 PMCID: PMC4336932 DOI: 10.1038/srep08531] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 01/23/2015] [Indexed: 11/09/2022] Open
Abstract
Pd nanoparticle (NP) coated LaAlO3/SrTiO3 (LAO/STO) heterointerface exhibits more notable conductance (G) change while varying the ambient gas (N2, H2/N2, and O2) and illuminating with UV light (wavelength: 365 nm) than a sample without the NPs. Simultaneous Kelvin probe force microscopy and transport measurements reveal close relationships between the surface work function (W) and G of the samples. Quantitative analyses suggest that a surface adsorption/desorption-mediated reaction and redox, resulting in a band-alignment modification and charge-transfer, could explain the gas- and photo-induced conductance modulation at the LAO/STO interface. Such surface-and-interface coupling enhanced by catalytic Pd NPs is a unique feature, quite distinct from conventional semiconductor hetero-junctions, which enables the significant conductance tunability at ultrathin oxide heterointerfaces by external stimuli.
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Affiliation(s)
- Haeri Kim
- 1] Department of Physics, Ewha Womans University, Seoul 120-750, Korea [2] Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea
| | - Ngai Yui Chan
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China
| | - Ji-yan Dai
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China
| | - Dong-Wook Kim
- Department of Physics, Ewha Womans University, Seoul 120-750, Korea
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19
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Kleandrova VV, Luan F, González-Díaz H, Ruso JM, Speck-Planche A, Cordeiro MNDS. Computational tool for risk assessment of nanomaterials: novel QSTR-perturbation model for simultaneous prediction of ecotoxicity and cytotoxicity of uncoated and coated nanoparticles under multiple experimental conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:14686-14694. [PMID: 25384130 DOI: 10.1021/es503861x] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nanomaterials have revolutionized modern science and technology due to their multiple applications in engineering, physics, chemistry, and biomedicine. Nevertheless, the use and manipulation of nanoparticles (NPs) can bring serious damages to living organisms and their ecosystems. For this reason, ecotoxicity and cytotoxicity assays are of special interest in order to determine the potential harmful effects of NPs. Processes based on ecotoxicity and cytotoxicity tests can significantly consume time and financial resources. In this sense, alternative approaches such as quantitative structure-activity/toxicity relationships (QSAR/QSTR) modeling have provided important insights for the better understanding of the biological behavior of NPs that may be responsible for causing toxicity. Until now, QSAR/QSTR models have predicted ecotoxicity or cytotoxicity separately against only one organism (bioindicator species or cell line) and have not reported information regarding the quantitative influence of characteristics other than composition or size. In this work, we developed a unified QSTR-perturbation model to simultaneously probe ecotoxicity and cytotoxicity of NPs under different experimental conditions, including diverse measures of toxicities, multiple biological targets, compositions, sizes and conditions to measure those sizes, shapes, times during which the biological targets were exposed to NPs, and coating agents. The model was created from 36488 cases (NP-NP pairs) and exhibited accuracies higher than 98% in both training and prediction sets. The model was used to predict toxicities of several NPs that were not included in the original data set. The results of the predictions suggest that the present QSTR-perturbation model can be employed as a highly promising tool for the fast and efficient assessment of ecotoxicity and cytotoxicity of NPs.
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Affiliation(s)
- Valeria V Kleandrova
- REQUIMTE/Department of Chemistry and Biochemistry, University of Porto , 4169-007 Porto, Portugal
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20
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Kleandrova VV, Luan F, González-Díaz H, Ruso JM, Melo A, Speck-Planche A, Cordeiro MNDS. Computational ecotoxicology: simultaneous prediction of ecotoxic effects of nanoparticles under different experimental conditions. ENVIRONMENT INTERNATIONAL 2014; 73:288-94. [PMID: 25173945 DOI: 10.1016/j.envint.2014.08.009] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 07/10/2014] [Accepted: 08/09/2014] [Indexed: 05/14/2023]
Abstract
Nanotechnology has brought great advances to many fields of modern science. A manifold of applications of nanoparticles have been found due to their interesting optical, electrical, and biological/chemical properties. However, the potential toxic effects of nanoparticles to different ecosystems are of special concern nowadays. Despite the efforts of the scientific community, the mechanisms of toxicity of nanoparticles are still poorly understood. Quantitative-structure activity/toxicity relationships (QSAR/QSTR) models have just started being useful computational tools for the assessment of toxic effects of nanomaterials. But most QSAR/QSTR models have been applied so far to predict ecotoxicity against only one organism/bio-indicator such as Daphnia magna. This prevents having a deeper knowledge about the real ecotoxic effects of nanoparticles, and consequently, there is no possibility to establish an efficient risk assessment of nanomaterials in the environment. In this work, a perturbation model for nano-QSAR problems is introduced with the aim of simultaneously predicting the ecotoxicity of different nanoparticles against several assay organisms (bio-indicators), by considering also multiple measures of ecotoxicity, as well as the chemical compositions, sizes, conditions under which the sizes were measured, shapes, and the time during which the diverse assay organisms were exposed to nanoparticles. The QSAR-perturbation model was derived from a database containing 5520 cases (nanoparticle-nanoparticle pairs), and it was shown to exhibit accuracies of ca. 99% in both training and prediction sets. In order to demonstrate the practical applicability of our model, three different nickel-based nanoparticles (Ni) with experimental values reported in the literature were predicted. The predictions were found to be in very good agreement with the experimental evidences, confirming that Ni-nanoparticles are not ecotoxic when compared with other nanoparticles. The results of this study thus provide a single valuable tool toward an efficient prediction of the ecotoxicity of nanoparticles under multiple experimental conditions.
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Affiliation(s)
- Valeria V Kleandrova
- REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007 Porto, Portugal
| | - Feng Luan
- REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007 Porto, Portugal; Department of Applied Chemistry, Yantai University, Yantai 264005, People's Republic of China
| | - Humberto González-Díaz
- Department of Organic Chemistry II, University of the Basque Country UPV/EHU, 48940 Bilbao, Spain; IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Juan M Ruso
- Department of Applied Physics, University of Santiago de Compostela (USC), 15782 Santiago de Compostela, Spain
| | - André Melo
- REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007 Porto, Portugal
| | - Alejandro Speck-Planche
- REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007 Porto, Portugal; Department of Applied Physics, University of Santiago de Compostela (USC), 15782 Santiago de Compostela, Spain.
| | - M Natália D S Cordeiro
- REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, 4169-007 Porto, Portugal.
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21
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Luan F, Kleandrova VV, González-Díaz H, Ruso JM, Melo A, Speck-Planche A, Cordeiro MNDS. Computer-aided nanotoxicology: assessing cytotoxicity of nanoparticles under diverse experimental conditions by using a novel QSTR-perturbation approach. NANOSCALE 2014; 6:10623-10630. [PMID: 25083742 DOI: 10.1039/c4nr01285b] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Nowadays, the interest in the search for new nanomaterials with improved electrical, optical, catalytic and biological properties has increased. Despite the potential benefits that can be gathered from the use of nanoparticles, only little attention has been paid to their possible toxic effects that may affect human health. In this context, several assays have been carried out to evaluate the cytotoxicity of nanoparticles in mammalian cells. Owing to the cost in both resources and time involved in such toxicological assays, there has been a considerable increase in the interest towards alternative computational methods, like the application of quantitative structure-activity/toxicity relationship (QSAR/QSTR) models for risk assessment of nanoparticles. However, most QSAR/QSTR models developed so far have predicted cytotoxicity against only one cell line, and they did not provide information regarding the influence of important factors rather than composition or size. This work reports a QSTR-perturbation model aiming at simultaneously predicting the cytotoxicity of different nanoparticles against several mammalian cell lines, and also considering different times of exposure of the cell lines, as well as the chemical composition of nanoparticles, size, conditions under which the size was measured, and shape. The derived QSTR-perturbation model, using a dataset of 1681 cases (nanoparticle-nanoparticle pairs), exhibited an accuracy higher than 93% for both training and prediction sets. In order to demonstrate the practical applicability of our model, the cytotoxicity of different silica (SiO2), nickel (Ni), and nickel(ii) oxide (NiO) nanoparticles were predicted and found to be in very good agreement with experimental reports. To the best of our knowledge, this is the first attempt to simultaneously predict the cytotoxicity of nanoparticles under multiple experimental conditions by applying a single unique QSTR model.
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Affiliation(s)
- Feng Luan
- Department of Applied Chemistry, Yantai University, Yantai 264005, People's Republic of China
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22
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Chan NY, Zhao M, Huang J, Au K, Wong MH, Yao HM, Lu W, Chen Y, Ong CW, Chan HLW, Dai J. Highly sensitive gas sensor by the LaAlO3 /SrTiO3 heterostructure with Pd nanoparticle surface modulation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:5962-5968. [PMID: 25042007 DOI: 10.1002/adma.201401597] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 05/29/2014] [Indexed: 06/03/2023]
Abstract
The palladium nanoparticle (Pd NP)-decorated LaAlO3 /SrTiO3 (LAO/STO) heterostructure is for the first time used as a hydrogen-gas sensor with very high sensitivity and workability at room temperature. The outstanding gas-sensing properties are due to the Pd NPs' catalytic effect to different gases, resulting in charge coupling between the gas molecules and the two-dimensional electron gas (2DEG) through the Pd NPs by either a direct charge exchange or a change of the electron affinity. These results provide insight into the emerging properties at LAO/STO interfaces.
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Affiliation(s)
- Ngai Yui Chan
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
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23
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Kim H, Moon SY, Kim SI, Baek SH, Jang HW, Kim DW. Influence of gas ambient on charge writing at the LaAlO₃/SrTiO₃ heterointerface. ACS APPLIED MATERIALS & INTERFACES 2014; 6:14037-14042. [PMID: 25004117 DOI: 10.1021/am503367f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigated the influences of charge writing on the surface work function (W) and sheet resistance (R) of the LaAlO3/SrTiO3 (LAO/STO) heterointerface in several gas environments: H2(2%)/N2(98%), air, N2, and O2. The decrease in W and R due to charge writing was much larger in air (ΔW = -0.45 eV and ΔR = -40 kΩ/S) than in O2 (ΔW = -0.21 eV and ΔR = -19 kΩ/S). The reduced R could be maintained more than 100 h in H2/N2. Such distinct behaviors were quantitatively discussed, based on the proposed charge-writing mechanisms. Such analyses showed how several processes, such as carrier transfer via surface adsorbates, surface redox, electronic state modification, and electrochemical surface reactions, contributed to charge writing in each gas.
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Affiliation(s)
- Haeri Kim
- Department of Physics, Ewha Womans University , Seoul 120-750, Republic of Korea
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