Pub Date : 2021-11-23DOI: 10.1088/2399-1984/ac3c8f
Bowen Zheng, Zeyu Zheng, Grace X. Gu
Graphene aerogels (GAs), a special class of 3D graphene assemblies, are well known for their exceptional combination of high strength, lightweightness, and high porosity. However, due to microstructural randomness, the mechanical properties of GAs are also highly stochastic, an issue that has been observed but insufficiently addressed. In this work, we develop Gaussian process metamodels to not only predict important mechanical properties of GAs but also quantify their uncertainties. Using the molecular dynamics simulation technique, GAs are assembled from randomly distributed graphene flakes and spherical inclusions, and are subsequently subject to a quasi-static uniaxial tensile load to deduce mechanical properties. Results show that given the same density, mechanical properties such as the Young’s modulus and the ultimate tensile strength can vary substantially. Treating density, Young’s modulus, and ultimate tensile strength as functions of the inclusion size, and using the simulated GA results as training data, we build Gaussian process metamodels that can efficiently predict the properties of unseen GAs. In addition, statistically valid confidence intervals centered around the predictions are established. This metamodel approach is particularly beneficial when the data acquisition requires expensive experiments or computation, which is the case for GA simulations. The present research quantifies the uncertain mechanical properties of GAs, which may shed light on the statistical analysis of novel nanomaterials of a broad variety.
{"title":"Uncertainty quantification and prediction for mechanical properties of graphene aerogels via Gaussian process metamodels","authors":"Bowen Zheng, Zeyu Zheng, Grace X. Gu","doi":"10.1088/2399-1984/ac3c8f","DOIUrl":"https://doi.org/10.1088/2399-1984/ac3c8f","url":null,"abstract":"Graphene aerogels (GAs), a special class of 3D graphene assemblies, are well known for their exceptional combination of high strength, lightweightness, and high porosity. However, due to microstructural randomness, the mechanical properties of GAs are also highly stochastic, an issue that has been observed but insufficiently addressed. In this work, we develop Gaussian process metamodels to not only predict important mechanical properties of GAs but also quantify their uncertainties. Using the molecular dynamics simulation technique, GAs are assembled from randomly distributed graphene flakes and spherical inclusions, and are subsequently subject to a quasi-static uniaxial tensile load to deduce mechanical properties. Results show that given the same density, mechanical properties such as the Young’s modulus and the ultimate tensile strength can vary substantially. Treating density, Young’s modulus, and ultimate tensile strength as functions of the inclusion size, and using the simulated GA results as training data, we build Gaussian process metamodels that can efficiently predict the properties of unseen GAs. In addition, statistically valid confidence intervals centered around the predictions are established. This metamodel approach is particularly beneficial when the data acquisition requires expensive experiments or computation, which is the case for GA simulations. The present research quantifies the uncertain mechanical properties of GAs, which may shed light on the statistical analysis of novel nanomaterials of a broad variety.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46786747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-22DOI: 10.1088/2399-1984/ac3bd4
Min-Won Kim, Ji-Hun Kim, Jun-Seong Park, Byoung-Seok Lee, S. Yoo, T. Shim, Jea‐Gun Park
In a two-terminal-electrode vertical thyristor, the latch-up and latch-down voltages are decreased when the memory operation temperature of the memory cells increases, resulting in a severe reliability issue (i.e. thermal instability). This study fundamentally solves the thermal instability of a vertical-thyristor by achieving a cross-point memory-cell array using a vertical-thyristor with a structure of vertical n++-emitter, p+-base, n+-base, and p++-emitter. The vertical-thyristor using a Schottky contact metal emitter instead of an n++-Si emitter significantly improves the thermal stability between 293 K and 373 K. Particularly, the improvement degree of the thermal stability is increased significantly with the use of the Schottky contact metal work function. Because the thermal instability (i.e. degree of latch-up voltage decrement vs. memory operation temperature) decreases with an increase in the Schottky contact metal work function, the dependency of the forward current density between the Schottky contact metal and p+-Si based on the memory operation temperature reduces with increase in the Schottky contact metal work function. Consequently, a higher Schottky contact metal work function produces a higher degree of improvement in the thermal stability, i.e. W (4.50 eV), Ti (4.33 eV), Ta (4.25 eV), and Al (4.12 eV). Further research on the fabrication process of a Schottky contact metal emitter vertical-thyristor is essential for the fabrication of a 3D cross-point memory-cell.
{"title":"Two-terminal vertical thyristor using Schottky contact emitter to improve thermal instability","authors":"Min-Won Kim, Ji-Hun Kim, Jun-Seong Park, Byoung-Seok Lee, S. Yoo, T. Shim, Jea‐Gun Park","doi":"10.1088/2399-1984/ac3bd4","DOIUrl":"https://doi.org/10.1088/2399-1984/ac3bd4","url":null,"abstract":"In a two-terminal-electrode vertical thyristor, the latch-up and latch-down voltages are decreased when the memory operation temperature of the memory cells increases, resulting in a severe reliability issue (i.e. thermal instability). This study fundamentally solves the thermal instability of a vertical-thyristor by achieving a cross-point memory-cell array using a vertical-thyristor with a structure of vertical n++-emitter, p+-base, n+-base, and p++-emitter. The vertical-thyristor using a Schottky contact metal emitter instead of an n++-Si emitter significantly improves the thermal stability between 293 K and 373 K. Particularly, the improvement degree of the thermal stability is increased significantly with the use of the Schottky contact metal work function. Because the thermal instability (i.e. degree of latch-up voltage decrement vs. memory operation temperature) decreases with an increase in the Schottky contact metal work function, the dependency of the forward current density between the Schottky contact metal and p+-Si based on the memory operation temperature reduces with increase in the Schottky contact metal work function. Consequently, a higher Schottky contact metal work function produces a higher degree of improvement in the thermal stability, i.e. W (4.50 eV), Ti (4.33 eV), Ta (4.25 eV), and Al (4.12 eV). Further research on the fabrication process of a Schottky contact metal emitter vertical-thyristor is essential for the fabrication of a 3D cross-point memory-cell.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42429776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-04DOI: 10.1088/2399-1984/ac36b5
Fayong Liu, M. Muruganathan, Yu-Lun Feng, Shinichi Ogawa, Y. Morita, Chunmeng Liu, Jiayu Guo, Marek E. Schmidt, H. Mizuta
Graphene-based thermal rectification was investigated by measuring the thermal transport properties of asymmetric suspended graphene nanomesh devices. A sub-10 nm periodic nanopore phononic crystal structure was successfully patterned on the half area of the suspended graphene ribbon by helium ion beam milling technology. The ‘differential thermal leakage’ method was developed for thermal transport measurement without disturbance from the leakage of electron current through the suspended graphene bridge. A thermal rectification ratio of up to 60% was observed in a typical device with a nanopore pitch of 20 nm. By increasing the nanopore pitch in a particular range, the thermal rectification ratio showed an increment. However, this ratio was degraded by increasing the environmental temperature. This experiment suggests a promising way to develop a high-performance thermal rectifier by using a phononic crystal to introduce asymmetry on homogeneous material.
{"title":"Thermal rectification on asymmetric suspended graphene nanomesh devices","authors":"Fayong Liu, M. Muruganathan, Yu-Lun Feng, Shinichi Ogawa, Y. Morita, Chunmeng Liu, Jiayu Guo, Marek E. Schmidt, H. Mizuta","doi":"10.1088/2399-1984/ac36b5","DOIUrl":"https://doi.org/10.1088/2399-1984/ac36b5","url":null,"abstract":"Graphene-based thermal rectification was investigated by measuring the thermal transport properties of asymmetric suspended graphene nanomesh devices. A sub-10 nm periodic nanopore phononic crystal structure was successfully patterned on the half area of the suspended graphene ribbon by helium ion beam milling technology. The ‘differential thermal leakage’ method was developed for thermal transport measurement without disturbance from the leakage of electron current through the suspended graphene bridge. A thermal rectification ratio of up to 60% was observed in a typical device with a nanopore pitch of 20 nm. By increasing the nanopore pitch in a particular range, the thermal rectification ratio showed an increment. However, this ratio was degraded by increasing the environmental temperature. This experiment suggests a promising way to develop a high-performance thermal rectifier by using a phononic crystal to introduce asymmetry on homogeneous material.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44020411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-09DOI: 10.1088/2399-1984/ac1bfc
Deepika Chauhan, Smriti Sri, Robin Kumar, A. Panda, P. Solanki
Gadolinium (Gd) has a strong paramagnetic response and is used in advanced magnetic resonance imaging (MRI). Gd is used in the complex form in MRI, but these complexes lack in sensitivity, targeting, rapid elimination from the body, and low internalization into the cell. To replace these Gd complex, the nanostructure (NSs) form of Gd has emerged as a viable solution as the NSs are expected to increase cell uptake and biocompatibility. The cytotoxicity evaluation is the key component that needs to be addressed for translating NSs from the lab to the clinic, and their effect on the cells is a vast area of research. Hence, the present study reports the hydrothermal synthesis of gadolinium oxide nanorods (Gd2O3 NRs) and ex-situ functionalized with aspartic acid (Asp-Gd2O3 NRs). The cytotoxicity studies on two cells namely RAW 264.7 and MCF-7 was assessed in terms of cell viability, morphological changes, and cell cycle analysis. Both types of NRs were well characterized and it was found that Asp-Gd2O3 NRs exhibited enhanced hydrophilicity and dispersity. Cell viability assay revealed enhanced biocompatibility of Asp-Gd2O3 NRs with almost 75% viability even at a higher concentration of 250 µg ml−1. The morphological changes upon internalization of both NRs were done through fluorescent microscopy that revealed no significant change in the morphology of the cell or its nucleus. Further, the cell cycle studies again confirmed the biocompatible nature of these NRs. These results suggest that Asp-Gd2O3 NRs are well suited for therapeutic applications, such as thermal cancer therapy, due to their tunable shape, size, low toxicity, and the possibility of surface modification.
{"title":"Assessment of cytotoxicity profile of gadolinium oxide nanorods and the analogous surface-functionalized nanorods","authors":"Deepika Chauhan, Smriti Sri, Robin Kumar, A. Panda, P. Solanki","doi":"10.1088/2399-1984/ac1bfc","DOIUrl":"https://doi.org/10.1088/2399-1984/ac1bfc","url":null,"abstract":"Gadolinium (Gd) has a strong paramagnetic response and is used in advanced magnetic resonance imaging (MRI). Gd is used in the complex form in MRI, but these complexes lack in sensitivity, targeting, rapid elimination from the body, and low internalization into the cell. To replace these Gd complex, the nanostructure (NSs) form of Gd has emerged as a viable solution as the NSs are expected to increase cell uptake and biocompatibility. The cytotoxicity evaluation is the key component that needs to be addressed for translating NSs from the lab to the clinic, and their effect on the cells is a vast area of research. Hence, the present study reports the hydrothermal synthesis of gadolinium oxide nanorods (Gd2O3 NRs) and ex-situ functionalized with aspartic acid (Asp-Gd2O3 NRs). The cytotoxicity studies on two cells namely RAW 264.7 and MCF-7 was assessed in terms of cell viability, morphological changes, and cell cycle analysis. Both types of NRs were well characterized and it was found that Asp-Gd2O3 NRs exhibited enhanced hydrophilicity and dispersity. Cell viability assay revealed enhanced biocompatibility of Asp-Gd2O3 NRs with almost 75% viability even at a higher concentration of 250 µg ml−1. The morphological changes upon internalization of both NRs were done through fluorescent microscopy that revealed no significant change in the morphology of the cell or its nucleus. Further, the cell cycle studies again confirmed the biocompatible nature of these NRs. These results suggest that Asp-Gd2O3 NRs are well suited for therapeutic applications, such as thermal cancer therapy, due to their tunable shape, size, low toxicity, and the possibility of surface modification.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49056658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-23DOI: 10.1088/2399-1984/ac0c24
Z. Dang, Yuqing Luo, Yangbing Xu, Pingqi Gao, Xueseng Wang
Transmission electron microscopy (TEM) has been used in the characterizations of the lattice and defect structures as well as electronic and chemical properties of various materials. When TEM analyses were performed on lead halide perovskites (LHPs) and related materials, it has often been found that transformation and damage were easily induced in the specimens by electron beam irradiation. As the structural and chemical instabilities of LHPs and related materials are the main obstacle that must be overcome for their practical large-scale applications in solar cells and other optoelectronic applications, we examine whether and how the TEM-based irradiation and analyses can serve the purpose of rapid evaluation of the instabilities of a LHP to stimuli such as light and electric field which are crucial to its optoelectronic applications. We first provide a brief overview of the basic physical properties of LHPs related to the instability and the current understanding of the general mechanisms of sample damages induced by energetic electrons, followed with an analysis of the distinctive vulnerability and damaging features of LHPs with respect to electron beam irradiation. Based on the analysis of the similarities in the mechanisms of the damages generated by different stimuli, proper conditions are outlined with which the TEM-based investigations can be employed as a speed-up tester for the instabilities of LHPs against photon (including visible, ultraviolet and x-ray) exposure and an applied electric field. Furthermore, the perspectives of employing TEM-based processes in the fabrication of nanostructures and directly carrying out subsequent in situ analysis are elaborated, which is key to acquiring knowledge for improving focused electron beam-based industrial micro- and nanofabrication technologies.
{"title":"Transformation and degradation of metal halide perovskites induced by energetic electrons and their practical implications","authors":"Z. Dang, Yuqing Luo, Yangbing Xu, Pingqi Gao, Xueseng Wang","doi":"10.1088/2399-1984/ac0c24","DOIUrl":"https://doi.org/10.1088/2399-1984/ac0c24","url":null,"abstract":"Transmission electron microscopy (TEM) has been used in the characterizations of the lattice and defect structures as well as electronic and chemical properties of various materials. When TEM analyses were performed on lead halide perovskites (LHPs) and related materials, it has often been found that transformation and damage were easily induced in the specimens by electron beam irradiation. As the structural and chemical instabilities of LHPs and related materials are the main obstacle that must be overcome for their practical large-scale applications in solar cells and other optoelectronic applications, we examine whether and how the TEM-based irradiation and analyses can serve the purpose of rapid evaluation of the instabilities of a LHP to stimuli such as light and electric field which are crucial to its optoelectronic applications. We first provide a brief overview of the basic physical properties of LHPs related to the instability and the current understanding of the general mechanisms of sample damages induced by energetic electrons, followed with an analysis of the distinctive vulnerability and damaging features of LHPs with respect to electron beam irradiation. Based on the analysis of the similarities in the mechanisms of the damages generated by different stimuli, proper conditions are outlined with which the TEM-based investigations can be employed as a speed-up tester for the instabilities of LHPs against photon (including visible, ultraviolet and x-ray) exposure and an applied electric field. Furthermore, the perspectives of employing TEM-based processes in the fabrication of nanostructures and directly carrying out subsequent in situ analysis are elaborated, which is key to acquiring knowledge for improving focused electron beam-based industrial micro- and nanofabrication technologies.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42510393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-04DOI: 10.1088/2399-1984/ac14c8
Z. Balogh, G. Mezei, László Pósa, Botond Sánta, A. Magyarkuti, A. Halbritter
In this paper, we review the 1/f-type noise properties of nanoelectronic devices focusing on three demonstrative platforms: resistive switching memories, graphene nanogaps and single-molecule nanowires. The functionality of such ultrasmall devices is confined to an extremely small volume, where bulk considerations on the noise lose their validity: the relative contribution of a fluctuator heavily depends on its distance from the device bottleneck, and the noise characteristics are sensitive to the nanometer-scale device geometry and details of the mostly non-classical transport mechanism. All these are reflected by a highly system-specific dependence of the noise properties on the active device volume (and the related device resistance), the frequency, or the applied voltage. Accordingly, 1/f-type noise measurements serve as a rich fingerprint of the relevant transport and noise-generating mechanisms in the studied nanoelectronic systems. Finally, we demonstrate that not only the fundamental understanding and the targeted noise suppression is fueled by the 1/f-type noise analysis, but novel probabilistic computing hardware platforms heavily seek well tailorable nanoelectric noise sources.
{"title":"1/f noise spectroscopy and noise tailoring of nanoelectronic devices","authors":"Z. Balogh, G. Mezei, László Pósa, Botond Sánta, A. Magyarkuti, A. Halbritter","doi":"10.1088/2399-1984/ac14c8","DOIUrl":"https://doi.org/10.1088/2399-1984/ac14c8","url":null,"abstract":"In this paper, we review the 1/f-type noise properties of nanoelectronic devices focusing on three demonstrative platforms: resistive switching memories, graphene nanogaps and single-molecule nanowires. The functionality of such ultrasmall devices is confined to an extremely small volume, where bulk considerations on the noise lose their validity: the relative contribution of a fluctuator heavily depends on its distance from the device bottleneck, and the noise characteristics are sensitive to the nanometer-scale device geometry and details of the mostly non-classical transport mechanism. All these are reflected by a highly system-specific dependence of the noise properties on the active device volume (and the related device resistance), the frequency, or the applied voltage. Accordingly, 1/f-type noise measurements serve as a rich fingerprint of the relevant transport and noise-generating mechanisms in the studied nanoelectronic systems. Finally, we demonstrate that not only the fundamental understanding and the targeted noise suppression is fueled by the 1/f-type noise analysis, but novel probabilistic computing hardware platforms heavily seek well tailorable nanoelectric noise sources.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46484793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.1088/2399-1984/abfb7d
M. Zouheir, O. Assila, K. Tanji, A. El Gaidoumi, J. Araña, J. M. Doña Rodríguez, J. Smått, T. Huynh, A. Kherbeche
This work reports a key factor, the H2SO4 concentration, in controlling the physicochemical properties of titanium dioxide (TiO2) photocatalysts during the sol–gel synthesis. The photocatalysts synthesized using different concentrations of H2SO4 possess specific anatase/rutile ratios and crystallite sizes as well as surface areas, resulting in different photocatalytic performance in the degradation of formic acid in solution. The best photocatalytic performance is observed for the TiO2 photocatalyst containing a relatively high percentage of the rutile phase (∼84%), which is obtained from the sol–gel synthesis without H2SO4.
{"title":"Bandgap optimization of sol–gel-derived TiO2 and its effect on the photodegradation of formic acid","authors":"M. Zouheir, O. Assila, K. Tanji, A. El Gaidoumi, J. Araña, J. M. Doña Rodríguez, J. Smått, T. Huynh, A. Kherbeche","doi":"10.1088/2399-1984/abfb7d","DOIUrl":"https://doi.org/10.1088/2399-1984/abfb7d","url":null,"abstract":"This work reports a key factor, the H2SO4 concentration, in controlling the physicochemical properties of titanium dioxide (TiO2) photocatalysts during the sol–gel synthesis. The photocatalysts synthesized using different concentrations of H2SO4 possess specific anatase/rutile ratios and crystallite sizes as well as surface areas, resulting in different photocatalytic performance in the degradation of formic acid in solution. The best photocatalytic performance is observed for the TiO2 photocatalyst containing a relatively high percentage of the rutile phase (∼84%), which is obtained from the sol–gel synthesis without H2SO4.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45865028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.1088/2399-1984/ac094c
Mingze Yang, A. Darbandi, S. Watkins, K. Kavanagh
We report electron-beam-induced current (EBIC) microscopy carried out on free-standing GaAs nanowire core–shell, p–n tunnel junctions. The carrier kinetics in both the n-type core and the p-type shell were determined by analyzing radial EBIC profiles as a function of beam energy. These profiles are highly sensitive to geometric effects such as facet width, shell and core thicknesses, and depletion widths. Combined with Monte Carlo simulations, they permitted measurement of the minority carrier diffusion lengths in the core and the shell, as well as the depletion widths as a function of radial direction. The relatively short minority carrier diffusion length in the core (50 nm), can be attributed to bulk point defects originating from low-temperature core growth (400 ∘C), or to interfacial recombination at traps at the p–n junction.
{"title":"Geometric effects on carrier collection in core–shell nanowire p–n junctions","authors":"Mingze Yang, A. Darbandi, S. Watkins, K. Kavanagh","doi":"10.1088/2399-1984/ac094c","DOIUrl":"https://doi.org/10.1088/2399-1984/ac094c","url":null,"abstract":"We report electron-beam-induced current (EBIC) microscopy carried out on free-standing GaAs nanowire core–shell, p–n tunnel junctions. The carrier kinetics in both the n-type core and the p-type shell were determined by analyzing radial EBIC profiles as a function of beam energy. These profiles are highly sensitive to geometric effects such as facet width, shell and core thicknesses, and depletion widths. Combined with Monte Carlo simulations, they permitted measurement of the minority carrier diffusion lengths in the core and the shell, as well as the depletion widths as a function of radial direction. The relatively short minority carrier diffusion length in the core (50 nm), can be attributed to bulk point defects originating from low-temperature core growth (400 ∘C), or to interfacial recombination at traps at the p–n junction.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43239491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-09DOI: 10.1088/2399-1984/abf6b2
P. Philip, Tomlal Jose, J. T. Mathew, Jinesh M. Kuthanapillil
Natural fibers and materials are well known for adsorption studies, whereas synthetic fibers have not received enough attention in this field. Therefore, an attempt is made here to study the adsorption properties of synthetic poly(methyl methacrylate) (PMMA) nanofibers and methods for improving or modifying their adsorption properties. PMMA nanofibers are prepared by the most recent electrospinning technique and the structural, and hence, the adsorption properties of the PMMA nanofibers are modified by preparing them in surface-roughened and coaxial hollow forms through electrospinning. Studies of the adsorption of methylene blue (MB) and brilliant green (BG) dyes by the three types of PMMA nanofiber demonstrate that all the PMMA nanofibers show a certain amount of adsorption. Fiber samples that had adsorbed MB and BG were subjected to various adsorption isotherms which confirmed the multilayer adsorption properties of the fiber samples by satisfying various isotherms, mainly the Freundlich and Elovich adsorption isotherms. Kinetic studies of pure and structurally modified PMMA nanofibers that had adsorbed MB and BG dyes proved that the intraparticle diffusion model applied to these fiber samples. Here, it is also shown that the adsorption properties of electrospun synthetic fibers can be further improved by structural modification using the possibilities of electrospinning.
{"title":"Multilayer adsorption and kinetic studies of dyes on pure and structurally modified poly(methyl methacrylate) electrospun nanofibers","authors":"P. Philip, Tomlal Jose, J. T. Mathew, Jinesh M. Kuthanapillil","doi":"10.1088/2399-1984/abf6b2","DOIUrl":"https://doi.org/10.1088/2399-1984/abf6b2","url":null,"abstract":"Natural fibers and materials are well known for adsorption studies, whereas synthetic fibers have not received enough attention in this field. Therefore, an attempt is made here to study the adsorption properties of synthetic poly(methyl methacrylate) (PMMA) nanofibers and methods for improving or modifying their adsorption properties. PMMA nanofibers are prepared by the most recent electrospinning technique and the structural, and hence, the adsorption properties of the PMMA nanofibers are modified by preparing them in surface-roughened and coaxial hollow forms through electrospinning. Studies of the adsorption of methylene blue (MB) and brilliant green (BG) dyes by the three types of PMMA nanofiber demonstrate that all the PMMA nanofibers show a certain amount of adsorption. Fiber samples that had adsorbed MB and BG were subjected to various adsorption isotherms which confirmed the multilayer adsorption properties of the fiber samples by satisfying various isotherms, mainly the Freundlich and Elovich adsorption isotherms. Kinetic studies of pure and structurally modified PMMA nanofibers that had adsorbed MB and BG dyes proved that the intraparticle diffusion model applied to these fiber samples. Here, it is also shown that the adsorption properties of electrospun synthetic fibers can be further improved by structural modification using the possibilities of electrospinning.","PeriodicalId":54222,"journal":{"name":"Nano Futures","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42445374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-09DOI: 10.1088/2399-1984/abf6b1
Luis Portilla, Jianwen Zhao, Jing Zhao, L. Occhipinti, V. Pecunia
The proliferation of place-and-forget devices driven by the exponentially-growing Internet of Things industry has created a demand for low-voltage thin-film transistor (TFT) electronics based on solution-processible semiconductors. Amongst solution-processible technologies, TFTs based on semiconducting single-walled carbon nanotubes (sc-SWCNTs) are a promising candidate owing to their comparatively high current driving capability in their above-threshold region at low voltages, which is desirable for applications with constraints on supply voltage and switching speed. Low-voltage above-threshold operation in sc-SWCNTs is customarily achieved by using high-capacitance-density gate dielectrics such as metal-oxides fabricated via atomic layer deposition (ALD) and ion-gels. These are unattractive, as ALD requires complex-processing or exotic precursors, while ion-gels lead to slower devices with poor stability. This work demonstrates the fabrication of low-voltage above-threshold sc-SWCNTs TFTs based on a high-capacitance-density hybrid nanodielectric, which is composed of a readily-made AlO x nanolayer and a solution-processed self-assembled monolayer (SAM). The resultant TFTs can withstand a gate-channel voltage of 1–2 V, which ensures their above-threshold operation with balanced ambipolar behavior and electron/hole mobilities of 7 cm2 V−1 s−1. Key to achieving balanced ambipolarity is the mitigation of environmental factors via the encapsulation of the devices with an optimized spin-on polymer coating, which preserves the inherent properties of the sc-SWCNTs. Such balanced ambipolarity enables the direct implementation of CMOS-like circuit configurations without the use of additional dopants, semiconductors or source/drain electrode metals. The resultant CMOS-like inverters operate in the above-threshold region with supply voltages in the 1–2 V range, and have positive noise margins, gain values surpassing 80 V/V, and a bandwidth exceeding 100 kHz. This reinforces SAM-based nanodielectrics as an attractive route to easy-to-fabricate sc-SWCNT TFTs that can operate in the above-threshold region and that can meet the demand for low-voltage TFT electronics requiring moderate speeds and higher driving currents for wearables and sensing applications.
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