The realization of remarkable thermoelectric (TE) properties in a novel single-crystalline quantum material is a topic of prime interest in the field of thermoelectricity. It necessitates a proper understanding of transport properties under magnetic field and magnetic properties at low field. We report polarized Raman spectroscopic study, TE properties, and magneto-resistance (MR) along with magnetic characterization of single-crystalline Bi2Se3. Polarized Raman spectrum confirms the strong polarization effect of A1g1 and A1g2 phonon modes, which verifies the anisotropic nature of the Bi2Se3 single crystal. Magnetization measurement along the in-plane direction of single crystal divulges a cusp-like paramagnetic response in susceptibility plot, indicating the presence of topological surface states (TSSs) in the material. In-depth MR studies performed in different configurations also confirm the presence of anisotropy in the single-crystalline Bi2Se3 sample. A sharp rise in MR value near zero magnetic field and low-temperature regime manifests a weak anti-localization (WAL) effect, depicting the quantum origin of the conductivity behavior at low temperature. Moreover, in-plane magneto-conductivity data at low-temperature (up to 5 K) and low-field region (≤15 kOe) confirm the dominance of the WAL effect (due to TSS) with a negligible bulk contribution. Quantum oscillation (SdH) in magneto-transport data also exhibits the signature of TSS. Additionally, an exceptional TE power factor of ∼950 μW m−1 K−2 at 300 K is achieved, which is one of the highest values reported for pristine Bi2Se3. Our findings pave the way for designing single crystals, which give dual advantages of being a good TE material along with a topological insulator bearing potential application.
{"title":"Investigation of thermoelectric and magnetotransport properties of single crystalline Bi2Se3 topological insulator","authors":"Pintu Singha, Subarna Das, Nabakumar Rana, Suchandra Mukherjee, Souvik Chatterjee, Sudipta Bandyopadhyay, Aritra Banerjee","doi":"10.1063/5.0168564","DOIUrl":"https://doi.org/10.1063/5.0168564","url":null,"abstract":"The realization of remarkable thermoelectric (TE) properties in a novel single-crystalline quantum material is a topic of prime interest in the field of thermoelectricity. It necessitates a proper understanding of transport properties under magnetic field and magnetic properties at low field. We report polarized Raman spectroscopic study, TE properties, and magneto-resistance (MR) along with magnetic characterization of single-crystalline Bi2Se3. Polarized Raman spectrum confirms the strong polarization effect of A1g1 and A1g2 phonon modes, which verifies the anisotropic nature of the Bi2Se3 single crystal. Magnetization measurement along the in-plane direction of single crystal divulges a cusp-like paramagnetic response in susceptibility plot, indicating the presence of topological surface states (TSSs) in the material. In-depth MR studies performed in different configurations also confirm the presence of anisotropy in the single-crystalline Bi2Se3 sample. A sharp rise in MR value near zero magnetic field and low-temperature regime manifests a weak anti-localization (WAL) effect, depicting the quantum origin of the conductivity behavior at low temperature. Moreover, in-plane magneto-conductivity data at low-temperature (up to 5 K) and low-field region (≤15 kOe) confirm the dominance of the WAL effect (due to TSS) with a negligible bulk contribution. Quantum oscillation (SdH) in magneto-transport data also exhibits the signature of TSS. Additionally, an exceptional TE power factor of ∼950 μW m−1 K−2 at 300 K is achieved, which is one of the highest values reported for pristine Bi2Se3. Our findings pave the way for designing single crystals, which give dual advantages of being a good TE material along with a topological insulator bearing potential application.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"14 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139409224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using the novel process of hot N+-ion implantation at 800 °C into Si quantum dots (Si-QDs) with approximately 3.2 nm fabricated by hot Si+-ion implantation into an SiO2 layer and post-Ar annealing, we experimentally demonstrated that the photoluminescence intensity (IPL) of the Si-QDs increased with increasing N+-ion dose (DN+). Post-N2 high-temperature annealing without hot N+-ion implantation, as a reference process, also increased the IPL of Si-QDs, because N atoms trapped within Si-QDs, which was evaluated by secondary ion mass spectrometry, terminate the dangling bonds within Si-QDs and at the Si/SiO2 interface. Additionally, the IPL of Si-QDs showed the maximum value at the optimal DN+ of 5 × 1015 cm−2, which was 1.4-fold higher than that observed without hot N+-ion implantation. With a short post-annealing time (<60 min), the increase in IPL owing to N+-ion implantation was considerably larger than that caused by N2 annealing, which is likely due to the efficiency of the termination of the dangling bonds of the Si-QDs by the N+-ions. This is an advantage of the hot N+-ion implantation technique. Forming gas annealing after furnace annealing also induced a larger IPL than that observed before forming gas annealing. However, the maximum IPL observed after forming gas annealing was completely independent of the conditions of furnace annealing and DN+. This suggests that the perfect termination of the dangling bonds of the Si-QDs may be realized via forming gas annealing after furnace annealing.
{"title":"Photoluminescence enhancement from hot nitrogen-ion implanted Si quantum dots embedded within SiO2 layer","authors":"Tomohisa Mizuno, Koki Murakawa","doi":"10.1063/5.0179699","DOIUrl":"https://doi.org/10.1063/5.0179699","url":null,"abstract":"Using the novel process of hot N+-ion implantation at 800 °C into Si quantum dots (Si-QDs) with approximately 3.2 nm fabricated by hot Si+-ion implantation into an SiO2 layer and post-Ar annealing, we experimentally demonstrated that the photoluminescence intensity (IPL) of the Si-QDs increased with increasing N+-ion dose (DN+). Post-N2 high-temperature annealing without hot N+-ion implantation, as a reference process, also increased the IPL of Si-QDs, because N atoms trapped within Si-QDs, which was evaluated by secondary ion mass spectrometry, terminate the dangling bonds within Si-QDs and at the Si/SiO2 interface. Additionally, the IPL of Si-QDs showed the maximum value at the optimal DN+ of 5 × 1015 cm−2, which was 1.4-fold higher than that observed without hot N+-ion implantation. With a short post-annealing time (&lt;60 min), the increase in IPL owing to N+-ion implantation was considerably larger than that caused by N2 annealing, which is likely due to the efficiency of the termination of the dangling bonds of the Si-QDs by the N+-ions. This is an advantage of the hot N+-ion implantation technique. Forming gas annealing after furnace annealing also induced a larger IPL than that observed before forming gas annealing. However, the maximum IPL observed after forming gas annealing was completely independent of the conditions of furnace annealing and DN+. This suggests that the perfect termination of the dangling bonds of the Si-QDs may be realized via forming gas annealing after furnace annealing.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"2 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139408668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junfeng Zou, Jingmao Huang, Junxian Pei, Xuelong Yang, Zhi Huang, Kang Liu
The rapid development of wearable electronics highlights the urgence to develop the portable energy harvester with excellent output performance, comfortability, and sustainability. This work designs an electromagnetic walking energy harvester based on water turbine that can be embedded in shoes with good comfortability. Its working principle is that the walking generated pressure energy drives a miniature hydraulic turbine to output electricity. Experimental results show that an average power of 300 and 180 mW can be produced at heel and toe, respectively, when a man of 80 kg walks at a speed of 1.8 m s−1. This power output exceeds the piezoelectric, triboelectric, and electromagnetic walking energy harvesters reported in the past. Additionally, the simpler structure endows it better comfortability as compared with the electrostatic capacitances. Computational fluid dynamics simulations provide a further insight that the efficiency of turbine can reach 13.5% by optimizing parameters of blade number and outlet flow ratio. Finally, user real-time positioning and trajectory recording are successfully demonstrated via a wearable GPS means Global Positioning System module powered by the harvester. Due to the combination of high output performance, simple structure and low discomfort, the water turbine based walking energy harvester will provide a wide application potential in wearable devices.
{"title":"A walking energy harvesting device based on miniature water turbine","authors":"Junfeng Zou, Jingmao Huang, Junxian Pei, Xuelong Yang, Zhi Huang, Kang Liu","doi":"10.1063/5.0182563","DOIUrl":"https://doi.org/10.1063/5.0182563","url":null,"abstract":"The rapid development of wearable electronics highlights the urgence to develop the portable energy harvester with excellent output performance, comfortability, and sustainability. This work designs an electromagnetic walking energy harvester based on water turbine that can be embedded in shoes with good comfortability. Its working principle is that the walking generated pressure energy drives a miniature hydraulic turbine to output electricity. Experimental results show that an average power of 300 and 180 mW can be produced at heel and toe, respectively, when a man of 80 kg walks at a speed of 1.8 m s−1. This power output exceeds the piezoelectric, triboelectric, and electromagnetic walking energy harvesters reported in the past. Additionally, the simpler structure endows it better comfortability as compared with the electrostatic capacitances. Computational fluid dynamics simulations provide a further insight that the efficiency of turbine can reach 13.5% by optimizing parameters of blade number and outlet flow ratio. Finally, user real-time positioning and trajectory recording are successfully demonstrated via a wearable GPS means Global Positioning System module powered by the harvester. Due to the combination of high output performance, simple structure and low discomfort, the water turbine based walking energy harvester will provide a wide application potential in wearable devices.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"16 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139408750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we have studied the spin-dependent ballistic transport and anomalous quantum tunneling in bilayer graphene horizontally placed in between two Rashba–Zeeman (RZ) leads under external electric biasing. We investigated the transmission and conductance for the proposed system using scattering matrix formalism and the Landauer–Büttiker formula considering a double delta-like barrier under a set of experimentally viable parameters. We found that the transmission characteristics are notably different for up- and down-spin incoming electrons depending upon the strength of magnetization. Moreover, the transmission of up- and down-spin electrons is found to be magnetization orientation dependent. The maximum tunneling conductance can be achieved by tuning biasing energy and magnetization strength and choosing a material with suitable Rashba spin–orbit coupling (RSOC). This astonishing property of our system can be utilized in fabricating devices, such as spin filters. We found that the Fano factor of our system is 0.4 under strong magnetization conditions, while it reduces to 0.3 under low magnetization conditions. Moreover, we also noticed that the transmission and conductance significantly depend on the Rashba–Zeeman effect. Therefore, considering a suitable RZ material, the tunneling of the electrons can be tuned and controlled. Our result suggests that considering suitable strength and orientation of magnetization with moderate RSOC, one can obtain a different transmission probability for spin species under suitable biasing energy. These results indicate the suitability of the proposed system in fabrication of spintronic devices, such as spin filter, spin transistor, etc.
{"title":"Ballistic transport and spin-dependent anomalous quantum tunneling in Rashba–Zeeman and bilayer graphene hybrid structures","authors":"Saumen Acharjee, Arindam Boruah, Reeta Devi, Nimisha Dutta","doi":"10.1063/5.0174626","DOIUrl":"https://doi.org/10.1063/5.0174626","url":null,"abstract":"In this work, we have studied the spin-dependent ballistic transport and anomalous quantum tunneling in bilayer graphene horizontally placed in between two Rashba–Zeeman (RZ) leads under external electric biasing. We investigated the transmission and conductance for the proposed system using scattering matrix formalism and the Landauer–Büttiker formula considering a double delta-like barrier under a set of experimentally viable parameters. We found that the transmission characteristics are notably different for up- and down-spin incoming electrons depending upon the strength of magnetization. Moreover, the transmission of up- and down-spin electrons is found to be magnetization orientation dependent. The maximum tunneling conductance can be achieved by tuning biasing energy and magnetization strength and choosing a material with suitable Rashba spin–orbit coupling (RSOC). This astonishing property of our system can be utilized in fabricating devices, such as spin filters. We found that the Fano factor of our system is 0.4 under strong magnetization conditions, while it reduces to 0.3 under low magnetization conditions. Moreover, we also noticed that the transmission and conductance significantly depend on the Rashba–Zeeman effect. Therefore, considering a suitable RZ material, the tunneling of the electrons can be tuned and controlled. Our result suggests that considering suitable strength and orientation of magnetization with moderate RSOC, one can obtain a different transmission probability for spin species under suitable biasing energy. These results indicate the suitability of the proposed system in fabrication of spintronic devices, such as spin filter, spin transistor, etc.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"111 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139408751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Temperature-dependent Raman spectral studies of BiFeO3 (BFO) films coated on three different substrates, viz., conducting Si (BFO-Si), sapphire (BFO-SAP), and fluorine-doped tin oxide (BFO-FTO), are reported between 123 and 773 K. The activity of Bi–O and Fe–O modes in these samples as a function of temperature shows different spectral features despite having synthesized from the same precursor. To understand the source of these variations, the spectra obtained on the above films were compared with those of bulk BiFeO3 (BFO-bulk) prepared via spark-plasma sintering. As the temperature increases, modes corresponding to the Bi–O activity at low frequency (120–180 cm−1) exhibit a redshift in their positions in all the samples. Between 350 and 550 K, BFO-SAP and BFO-Si samples show discernible anomalies in the positions of modes corresponding to the Fe–O activity (200–500 cm−1), which is not observed in the BFO-bulk and BFO-FTO samples. These anomalies are more pronounced for the modes between 350 and 500 cm−1, suggesting alterations in the Néel transition temperature (∼643 K for BiFeO3). Concurrently, another composite film of BiFeO3–CoFe2O4 coated on the Si substrate is explored. Raman studies on the composite film are used to compare and verify the influence of the substrate and defects on the magnetic ordering as a function of temperature. Our study highlights the significance and relevance of using Raman spectroscopy as a tool to discern various factors leading to local structural and magnetic variation in a given compound.
{"title":"Temperature-dependent Raman spectral evidence of local structural changes in BiFeO3 thin films: Influence of substrate and oxygen vacancies","authors":"Subhajit Nandy, Pavana S. V. Mocherla, C. Sudakar","doi":"10.1063/5.0167782","DOIUrl":"https://doi.org/10.1063/5.0167782","url":null,"abstract":"Temperature-dependent Raman spectral studies of BiFeO3 (BFO) films coated on three different substrates, viz., conducting Si (BFO-Si), sapphire (BFO-SAP), and fluorine-doped tin oxide (BFO-FTO), are reported between 123 and 773 K. The activity of Bi–O and Fe–O modes in these samples as a function of temperature shows different spectral features despite having synthesized from the same precursor. To understand the source of these variations, the spectra obtained on the above films were compared with those of bulk BiFeO3 (BFO-bulk) prepared via spark-plasma sintering. As the temperature increases, modes corresponding to the Bi–O activity at low frequency (120–180 cm−1) exhibit a redshift in their positions in all the samples. Between 350 and 550 K, BFO-SAP and BFO-Si samples show discernible anomalies in the positions of modes corresponding to the Fe–O activity (200–500 cm−1), which is not observed in the BFO-bulk and BFO-FTO samples. These anomalies are more pronounced for the modes between 350 and 500 cm−1, suggesting alterations in the Néel transition temperature (∼643 K for BiFeO3). Concurrently, another composite film of BiFeO3–CoFe2O4 coated on the Si substrate is explored. Raman studies on the composite film are used to compare and verify the influence of the substrate and defects on the magnetic ordering as a function of temperature. Our study highlights the significance and relevance of using Raman spectroscopy as a tool to discern various factors leading to local structural and magnetic variation in a given compound.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"14 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139409188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jia Yi Chia, Nuatawan Thamrongsiripak, Sornwit Thongphanit, Noppadon Nuntawong
Radiation damage in semiconductor materials is a crucial concern for electronic applications, especially in the fields of space, military, nuclear, and medical electronics. With the advancements in semiconductor fabrication techniques and the trend of miniaturization, the quality of semiconductor materials and their susceptibility to radiation-induced defects have become more important than ever. In this context, machine learning (ML) algorithms have emerged as a promising tool to study minor radiation-induced defects in semiconductor materials. In this study, we propose a sensitive non-destructive technique for investigating radiation-induced defects using multivariate statistical analyses combined with Raman spectroscopy. Raman spectroscopy is a contactless and non-destructive method widely used to characterize semiconductor materials and their defects. The multivariate statistical methods applied in analyzing the Raman spectra provide high sensitivity in detecting minor radiation-induced defects. The proposed technique was demonstrated by categorizing 100–500 kGy irradiated GaAs wafers into samples with low and high irradiation levels using linear discrimination analysis ML algorithms. Despite the high similarity in the obtained Raman spectra, the ML algorithms correctly predicted the blind testing samples, highlighting the effectiveness of ML in defect study. This study provides a promising approach for detecting minor radiation-induced defects in semiconductor materials and can be extended to other semiconductor materials and devices.
半导体材料中的辐射损伤是电子应用中的一个关键问题，尤其是在空间、军事、核和医疗电子领域。随着半导体制造技术的进步和微型化趋势的发展，半导体材料的质量及其对辐射引起的缺陷的敏感性变得比以往任何时候都更加重要。在此背景下，机器学习（ML）算法已成为研究半导体材料中微小辐射诱导缺陷的一种有前途的工具。在本研究中，我们提出了一种灵敏的非破坏性技术，利用多元统计分析与拉曼光谱相结合来研究辐射诱发的缺陷。拉曼光谱是一种广泛用于表征半导体材料及其缺陷的非接触、非破坏性方法。应用于分析拉曼光谱的多元统计方法在检测微小辐射诱发缺陷方面具有很高的灵敏度。通过使用线性判别分析 ML 算法将 100-500 kGy 辐照砷化镓晶片分为低辐照度和高辐照度样品，证明了所提出的技术。尽管获得的拉曼光谱具有很高的相似性，但 ML 算法还是正确预测了盲测样品，突出了 ML 在缺陷研究中的有效性。这项研究为检测半导体材料中由辐射引起的微小缺陷提供了一种很有前景的方法，并可推广到其他半导体材料和器件中。
{"title":"Machine learning-enhanced detection of minor radiation-induced defects in semiconductor materials using Raman spectroscopy","authors":"Jia Yi Chia, Nuatawan Thamrongsiripak, Sornwit Thongphanit, Noppadon Nuntawong","doi":"10.1063/5.0179881","DOIUrl":"https://doi.org/10.1063/5.0179881","url":null,"abstract":"Radiation damage in semiconductor materials is a crucial concern for electronic applications, especially in the fields of space, military, nuclear, and medical electronics. With the advancements in semiconductor fabrication techniques and the trend of miniaturization, the quality of semiconductor materials and their susceptibility to radiation-induced defects have become more important than ever. In this context, machine learning (ML) algorithms have emerged as a promising tool to study minor radiation-induced defects in semiconductor materials. In this study, we propose a sensitive non-destructive technique for investigating radiation-induced defects using multivariate statistical analyses combined with Raman spectroscopy. Raman spectroscopy is a contactless and non-destructive method widely used to characterize semiconductor materials and their defects. The multivariate statistical methods applied in analyzing the Raman spectra provide high sensitivity in detecting minor radiation-induced defects. The proposed technique was demonstrated by categorizing 100–500 kGy irradiated GaAs wafers into samples with low and high irradiation levels using linear discrimination analysis ML algorithms. Despite the high similarity in the obtained Raman spectra, the ML algorithms correctly predicted the blind testing samples, highlighting the effectiveness of ML in defect study. This study provides a promising approach for detecting minor radiation-induced defects in semiconductor materials and can be extended to other semiconductor materials and devices.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"16 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139408671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael M. Salour, James G. Grote, Gitansh Kataria, Mani Chandra, Ravishankar Sundararaman
Electromagnetic shielding is a critical function in various technologies, which is ideally achieved using a metal that reflects all incident radiation below its plasma frequency. Using high-resolution finite difference frequency domain simulations at microwave/RF frequencies, we show that the same efficacy can be achieved using a disordered collection of metal nanoparticles embedded in a flexible material. The mechanism underlying the reflection in the composite material is wave localization, disallowing the propagation of radiation up to the plasma frequency of the metal that constitutes the particles. We realize such a biopolymer composite using DNA–CTMA (deoxyribonucleic acid–cetyltrimethylammonium complex) as a support structure for Ag nanoparticles. This biopolymer composite exhibits an extremely high shielding effectiveness, close to that of a metal slab, because of Anderson localization of the electromagnetic waves.
{"title":"Electromagnetic shielding using Anderson localization in nanoparticle–biopolymer composites","authors":"Michael M. Salour, James G. Grote, Gitansh Kataria, Mani Chandra, Ravishankar Sundararaman","doi":"10.1063/5.0159787","DOIUrl":"https://doi.org/10.1063/5.0159787","url":null,"abstract":"Electromagnetic shielding is a critical function in various technologies, which is ideally achieved using a metal that reflects all incident radiation below its plasma frequency. Using high-resolution finite difference frequency domain simulations at microwave/RF frequencies, we show that the same efficacy can be achieved using a disordered collection of metal nanoparticles embedded in a flexible material. The mechanism underlying the reflection in the composite material is wave localization, disallowing the propagation of radiation up to the plasma frequency of the metal that constitutes the particles. We realize such a biopolymer composite using DNA–CTMA (deoxyribonucleic acid–cetyltrimethylammonium complex) as a support structure for Ag nanoparticles. This biopolymer composite exhibits an extremely high shielding effectiveness, close to that of a metal slab, because of Anderson localization of the electromagnetic waves.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"25 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139409223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Fettar, L. Cagnon, D. Barral, P. David, L. Naudin, F. Blondelle, F. Gay
There exists a controversy in the literature concerning the values of coercive and bias fields in antidots magnetic structures formed by a hexagonal network of nanoholes. The coercive fields (HC) and the exchange bias fields (∣HEXC∣) for antidots (deposited on ultrathin anodic aluminum oxide, namely, AAO) are either increased or diminished by comparison with the same magnetic nanostructures grown on continuous substrates (namely, CML). We propose to elucidate these debates by showing the importance of the easy axis of the magnetization, the direction of the applied magnetic field, the thicknesses of the layers, and the 3D-topology of nanoholes, as well as the magnetic and thermal history of the magnetic measurements. Here, biased Ta(5 nm)/Pt(5 nm)/Co(0.6 nm)/Fe50Mn50(X)/Ta(5 nm) antidots are investigated by extraordinary Hall effect measurements at 5 K, where X varies in the (0–5.5) nm range. The substrate consists in a hexagonal array of holes, described by the pair of (p,d) values, respectively, the period as the distance from center to center of two consecutive holes and the hole diameter. The dimensions of antidots are (p≈100 and d≈40 nm) for X=(2–5.5) nm, (p≈150 and d≈60 nm) for X=3.5 nm, and (p≈100 and d≈60 nm) for X=0. A continuous stack using Si/SiO2(100 nm) is used for comparison. HC and ∣HEXC∣ gradually increase when X is enhanced for both substrates, with nevertheless a weak decrease at high X for the continuous system. Perpendicular magnetic anisotropy is only observed for both unbiased samples, the X=2 nm continuous sample, and both X=5 nm samples that have undergone field cooling treatment from 500 to 5 K under −2 T. Usually, HC(AAO)>HC(CML), ∣HEXC(AAO)∣>∣HEXC(CML)∣, and ∣HA(AAO)∣<∣HA(CML)∣ (HA designating the anisotropy field). However, for certain conditions, as, for instance, for FC-procedures starting from high temperatures and/or strong magnetic field, other situations might be observed. A discussion pertaining to the amplitudes of HC, ∣HEXC∣ and the anisotropy field (∣HA∣) of continuous and discontinuous samples is given for our experimental results as well as for published data in the literature, in the light of structural characteristics (wedge-to-wedge distance, porosity, or coverage ratio). Such biased perpendicular antidots might be particularly used in specific nanomaterials devoted to spintronics.
关于由纳米孔六边形网络形成的反点阵磁结构中的矫顽力场和偏置场的值，文献中存在争议。与生长在连续基底（即 CML）上的相同磁性纳米结构相比，沉积在超薄阳极氧化铝（即 AAO）上的 antidots 的矫顽力场 (HC) 和交换偏置场 (∣HEXC∣) 要么增大，要么减小。我们建议通过说明磁化易轴、外加磁场方向、层厚度和纳米孔三维拓扑结构以及磁性测量的磁性和热历史的重要性来阐明这些争论。在此，通过在 5 K 条件下进行非凡霍尔效应测量，研究了偏置的 Ta(5 nm)/Pt(5 nm)/Co(0.6 nm)/Fe50Mn50(X)/Ta(5 nm) antidots，其中 X 在 (0-5.5) nm 范围内变化。衬底由六边形孔阵列组成，分别用一对（p,d）值来描述，周期为两个连续孔中心到中心的距离和孔直径。当 X=(2-5.5) nm 时，锑点的尺寸为（p≈100 和 d≈40 nm）；当 X=3.5 nm 时，锑点的尺寸为（p≈150 和 d≈60 nm）；当 X=0 时，锑点的尺寸为（p≈100 和 d≈60 nm）。当 X 增强时，两种基底的 HC 和 ∣HEXC∣ 都会逐渐增加，然而在连续系统中，当 X 高时，HC 和 ∣HEXC∣ 会有微弱的下降。只有在两个无偏样品、X=2 nm 的连续样品以及在 -2 T 条件下经过从 500 K 到 5 K 的场冷却处理的两个 X=5 nm 样品中才能观察到垂直磁各向异性。通常，HC(AAO)>HC(CML)、∣HEXC(AAO)∣>∣HEXC(CML)∣和∣HA(AAO)∣<∣HA(CML)∣（HA 表示各向异性场）。然而，在某些条件下，例如从高温和/或强磁场开始的 FC 过程，可能会出现其他情况。根据结构特征（楔刃间距、孔隙率或覆盖率），对连续和不连续样品的 HC、∣HEXC∣ 和各向异性场 (∣HA∣) 的振幅进行了讨论。这种偏压垂直反向点可能特别适用于自旋电子学的特定纳米材料。
{"title":"Investigation of magnetic hysteresis in biased Ta/Pt/Co/FeMn/Ta antidots: Influence of structural dimensions","authors":"F. Fettar, L. Cagnon, D. Barral, P. David, L. Naudin, F. Blondelle, F. Gay","doi":"10.1063/5.0173469","DOIUrl":"https://doi.org/10.1063/5.0173469","url":null,"abstract":"There exists a controversy in the literature concerning the values of coercive and bias fields in antidots magnetic structures formed by a hexagonal network of nanoholes. The coercive fields (HC) and the exchange bias fields (∣HEXC∣) for antidots (deposited on ultrathin anodic aluminum oxide, namely, AAO) are either increased or diminished by comparison with the same magnetic nanostructures grown on continuous substrates (namely, CML). We propose to elucidate these debates by showing the importance of the easy axis of the magnetization, the direction of the applied magnetic field, the thicknesses of the layers, and the 3D-topology of nanoholes, as well as the magnetic and thermal history of the magnetic measurements. Here, biased Ta(5 nm)/Pt(5 nm)/Co(0.6 nm)/Fe50Mn50(X)/Ta(5 nm) antidots are investigated by extraordinary Hall effect measurements at 5 K, where X varies in the (0–5.5) nm range. The substrate consists in a hexagonal array of holes, described by the pair of (p,d) values, respectively, the period as the distance from center to center of two consecutive holes and the hole diameter. The dimensions of antidots are (p≈100 and d≈40 nm) for X=(2–5.5) nm, (p≈150 and d≈60 nm) for X=3.5 nm, and (p≈100 and d≈60 nm) for X=0. A continuous stack using Si/SiO2(100 nm) is used for comparison. HC and ∣HEXC∣ gradually increase when X is enhanced for both substrates, with nevertheless a weak decrease at high X for the continuous system. Perpendicular magnetic anisotropy is only observed for both unbiased samples, the X=2 nm continuous sample, and both X=5 nm samples that have undergone field cooling treatment from 500 to 5 K under −2 T. Usually, HC(AAO)&gt;HC(CML), ∣HEXC(AAO)∣&gt;∣HEXC(CML)∣, and ∣HA(AAO)∣&lt;∣HA(CML)∣ (HA designating the anisotropy field). However, for certain conditions, as, for instance, for FC-procedures starting from high temperatures and/or strong magnetic field, other situations might be observed. A discussion pertaining to the amplitudes of HC, ∣HEXC∣ and the anisotropy field (∣HA∣) of continuous and discontinuous samples is given for our experimental results as well as for published data in the literature, in the light of structural characteristics (wedge-to-wedge distance, porosity, or coverage ratio). Such biased perpendicular antidots might be particularly used in specific nanomaterials devoted to spintronics.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"7 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139375804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The dual-scrambling scheme that combines position transformation and bit-plane transformation is a popular image encryption scheme. However, such schemes need more key information, and the encryption and decryption processes are complicated. In addition, the existing quantum image dual-scrambling schemes mainly deal with square images. In this paper, we propose a hybrid scrambling encryption scheme for multi-mode quantum image representation (MQIR) images based on random permutation, in which the H×W quantum image is represented in MQIR. A random number generator factor s uniquely associates one of the random permutations of integers from 1 to a positive integer, so as to hybrid scramble both the pixel position and the binarized position of each pixel value. Meanwhile, the quantum circuits and some examples of scrambling are given. Furthermore, various analyses of the performance of this scheme were conducted, including effectiveness, key space, and computational complexity. By modifying the random generation factor to construct multiple binary grayscale images, the simulated results on the IBM Quantum Cloud platform demonstrate that the proposed quantum image encryption scheme is effective. In comparison to existing quantum image dual scrambling schemes, it is both simple and effective, offering a large key space, lower computational complexity, and applicability to non-square quantum images.
结合了位置变换和位平面变换的双重加扰方案是一种流行的图像加密方案。然而，这种方案需要较多的密钥信息，加解密过程复杂。此外，现有的量子图像双扫描方案主要针对正方形图像。本文提出了一种基于随机置换的多模量子图像表示（MQIR）混合加扰加密方案，其中 H×W 量子图像用 MQIR 表示。随机数发生器因子 s 唯一关联一个从 1 到正整数的整数随机排列，从而对每个像素值的像素位置和二值化位置进行混合加扰。同时，还给出了量子电路和一些加扰实例。此外，还对该方案的性能进行了各种分析，包括有效性、密钥空间和计算复杂度。通过修改随机生成因子来构建多个二进制灰度图像，在 IBM 量子云平台上的模拟结果表明，所提出的量子图像加密方案是有效的。与现有的量子图像双重加扰方案相比，该方案既简单又有效，具有较大的密钥空间、较低的计算复杂度，并且适用于非正方形量子图像。
{"title":"Random permutation-based mixed-double scrambling technique for encrypting MQIR image","authors":"Hai-hua Zhu, Zi-gang Chen, Tao Leng","doi":"10.1063/5.0177920","DOIUrl":"https://doi.org/10.1063/5.0177920","url":null,"abstract":"The dual-scrambling scheme that combines position transformation and bit-plane transformation is a popular image encryption scheme. However, such schemes need more key information, and the encryption and decryption processes are complicated. In addition, the existing quantum image dual-scrambling schemes mainly deal with square images. In this paper, we propose a hybrid scrambling encryption scheme for multi-mode quantum image representation (MQIR) images based on random permutation, in which the H×W quantum image is represented in MQIR. A random number generator factor s uniquely associates one of the random permutations of integers from 1 to a positive integer, so as to hybrid scramble both the pixel position and the binarized position of each pixel value. Meanwhile, the quantum circuits and some examples of scrambling are given. Furthermore, various analyses of the performance of this scheme were conducted, including effectiveness, key space, and computational complexity. By modifying the random generation factor to construct multiple binary grayscale images, the simulated results on the IBM Quantum Cloud platform demonstrate that the proposed quantum image encryption scheme is effective. In comparison to existing quantum image dual scrambling schemes, it is both simple and effective, offering a large key space, lower computational complexity, and applicability to non-square quantum images.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"13 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139375834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Orfao, M. Abou Daher, R. A. Peña, B. G. Vasallo, S. Pérez, I. Íñiguez-de-la-Torre, G. Paz-Martínez, J. Mateos, Y. Roelens, M. Zaknoune, T. González
In this paper, we report an analysis of reverse current mechanisms observed in GaN Schottky barrier diodes leading to hysteretic behavior of the I–V curves at low temperature. By means of DC measurements from 33 to 475 K, we demonstrate the presence of two leakage mechanisms when comparing the experiments with the results obtained using a unified model to predict the ideal reverse current of the diode. Poole–Frenkel emission is the dominant mechanism for temperatures above 200 K, while trap-assisted tunneling prevails for lower temperatures, where also, hysteresis cycles are revealed by means of DC dual-sweep voltage measurements. The energy of the corresponding traps has also been determined, being around 0.2 and 0.45 eV, respectively. The hysteresis phenomenon is attributed to the bias-induced occupancy of the energy states originating the leakage-current processes, which leads to the reduction of the reverse current after a high negative voltage is applied to the diode.
本文分析了在 GaN 肖特基势垒二极管中观察到的导致低温下 I-V 曲线滞后行为的反向电流机制。通过从 33 到 475 K 的直流测量，我们将实验结果与使用统一模型预测二极管理想反向电流得到的结果进行比较，证明存在两种泄漏机制。在温度高于 200 K 时，普尔-弗伦克尔发射是主要机制，而在较低温度时，阱辅助隧穿则占主导地位。相应陷阱的能量也已确定，分别约为 0.2 和 0.45 eV。滞后现象归因于偏压引起的漏电流过程能态占据，这导致在二极管上施加高负压后反向电流减小。
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