Chace Franey, Sean L. Murray, Bakir M. Al-Ameri, Mohammad Ghashami
The lack of low-work function materials and the negative space charge effect have long prevented vacuum thermionic energy converters (VTECs) from becoming a practical means of power generation. Advancements in microfabrication have since provided solutions to these challenges, such as the suppression of negative space charge via a micro/nanoscale interelectrode vacuum gap distance, reigniting interest in VTECs as a potential clean energy technology. However, the limited operational lifetimes of many low-work function coatings have hindered their practical device-level implementation. Solid-state thermionic energy converters (SSTECs) have been proposed as a viable alternative to VTECs since they do not require an interelectrode vacuum gap or low-work function electrodes. Nevertheless, SSTECs still require a large temperature gradient between electrodes and are limited to low operating voltages. To address these limitations, we propose a near-field enhanced solid-state thermionic energy converter (NF-SSTEC), which leverages the advantages of SSTECs by eliminating the need for a large temperature gradient between the electrodes and increasing the range of possible operating voltages. We theoretically demonstrate conversion efficiencies of 16.8 % and power densities as high as 13.1 W cm−2 without needing a high-temperature gradient between the radiator and SSTEC. Additionally, we compare its performance under different radiation spectra, showing the potential for improvement via further optimization of the radiator.
{"title":"Near-field enhanced solid-state thermionic power generation","authors":"Chace Franey, Sean L. Murray, Bakir M. Al-Ameri, Mohammad Ghashami","doi":"10.1063/5.0238282","DOIUrl":"https://doi.org/10.1063/5.0238282","url":null,"abstract":"The lack of low-work function materials and the negative space charge effect have long prevented vacuum thermionic energy converters (VTECs) from becoming a practical means of power generation. Advancements in microfabrication have since provided solutions to these challenges, such as the suppression of negative space charge via a micro/nanoscale interelectrode vacuum gap distance, reigniting interest in VTECs as a potential clean energy technology. However, the limited operational lifetimes of many low-work function coatings have hindered their practical device-level implementation. Solid-state thermionic energy converters (SSTECs) have been proposed as a viable alternative to VTECs since they do not require an interelectrode vacuum gap or low-work function electrodes. Nevertheless, SSTECs still require a large temperature gradient between electrodes and are limited to low operating voltages. To address these limitations, we propose a near-field enhanced solid-state thermionic energy converter (NF-SSTEC), which leverages the advantages of SSTECs by eliminating the need for a large temperature gradient between the electrodes and increasing the range of possible operating voltages. We theoretically demonstrate conversion efficiencies of 16.8 % and power densities as high as 13.1 W cm−2 without needing a high-temperature gradient between the radiator and SSTEC. Additionally, we compare its performance under different radiation spectra, showing the potential for improvement via further optimization of the radiator.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"26 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Binbin Wu, Yu Li, Yuru Lin, Jingyi Liu, Yu Tao, Xue Chang, Li Lei
The pressure-induced phase transition from hexagonal wurtzite (B4) to cubic rock salt (B1) in semiconductors is generally identified as an important displacement-type structural transition. Despite the important advancements shown in the literature, the B4–B1 transition boundaries have yet to be well determined due to the experiment's technical challenges, especially in the low-temperature region, resulting in a blank in the pressure–temperature (P–T) phase diagrams and in the absence of experimental data on the Clapeyron slopes. Here, we probe the pressure-induced B4–B1 phase transition of some typical semiconductors (ZnO, GaN, AlN, and LiGaO2) at low temperatures (90–300 K) using a self-designed isothermal compression in situ Raman spectroscopy technique. We experimentally determine their B4–B1 phase boundaries at low temperature and obtain the corresponding negative Clapeyron slope parameters, with steeper slopes corresponding to larger entropy changes. Our findings provide insight into the pressure-induced B4–B1 transition in semiconductors and reveal the relationship between the bond energy and the Clapeyron slope in the B4–B1 transition.
{"title":"Determination of the B4-B1 phase boundary in semiconductors using isothermal compression Raman spectroscopy","authors":"Binbin Wu, Yu Li, Yuru Lin, Jingyi Liu, Yu Tao, Xue Chang, Li Lei","doi":"10.1063/5.0258376","DOIUrl":"https://doi.org/10.1063/5.0258376","url":null,"abstract":"The pressure-induced phase transition from hexagonal wurtzite (B4) to cubic rock salt (B1) in semiconductors is generally identified as an important displacement-type structural transition. Despite the important advancements shown in the literature, the B4–B1 transition boundaries have yet to be well determined due to the experiment's technical challenges, especially in the low-temperature region, resulting in a blank in the pressure–temperature (P–T) phase diagrams and in the absence of experimental data on the Clapeyron slopes. Here, we probe the pressure-induced B4–B1 phase transition of some typical semiconductors (ZnO, GaN, AlN, and LiGaO2) at low temperatures (90–300 K) using a self-designed isothermal compression in situ Raman spectroscopy technique. We experimentally determine their B4–B1 phase boundaries at low temperature and obtain the corresponding negative Clapeyron slope parameters, with steeper slopes corresponding to larger entropy changes. Our findings provide insight into the pressure-induced B4–B1 transition in semiconductors and reveal the relationship between the bond energy and the Clapeyron slope in the B4–B1 transition.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"214 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Fully understanding and modulating the nonlinear absorption in GaN are crucial for designing ultrafast photonic devices. In this work, both the ultra-broadband transient absorption spectra and carrier recombination time in GaN were found to be significantly altered by carbon defects. An energy band model for carbon defect dynamics was established based on transient absorption and photoluminescence spectroscopy. Our model discernibly reveals that CN and tri-carbon in GaN intricately modulate both the absorption spectrum and carrier capture process: The rapid capture of holes by the CN defect significantly reduces the hole recombination time to hundreds of femtoseconds in the near-infrared band. Conversely, the tri-carbon defect exhibited a higher absorption cross section by an order of magnitude than that of free carrier in the visible region with a long carrier recombination time. This work clarifies the modulation mechanisms of complex carbon defects in GaN's nonlinear absorption and provides scientific guidance for designing broadband and integrated ultrafast optical nonlinear devices.
{"title":"Broadband carrier capture dynamics mechanism of carbon-related defects in GaN","authors":"Zhanpeng Chen, Fangyuan Shi, Yunfei Lv, Zhengguo Xiao, Xingzhi Wu, Junyi Yang, Quanying Wu, Yinglin Song, Yu Fang","doi":"10.1063/5.0260238","DOIUrl":"https://doi.org/10.1063/5.0260238","url":null,"abstract":"Fully understanding and modulating the nonlinear absorption in GaN are crucial for designing ultrafast photonic devices. In this work, both the ultra-broadband transient absorption spectra and carrier recombination time in GaN were found to be significantly altered by carbon defects. An energy band model for carbon defect dynamics was established based on transient absorption and photoluminescence spectroscopy. Our model discernibly reveals that CN and tri-carbon in GaN intricately modulate both the absorption spectrum and carrier capture process: The rapid capture of holes by the CN defect significantly reduces the hole recombination time to hundreds of femtoseconds in the near-infrared band. Conversely, the tri-carbon defect exhibited a higher absorption cross section by an order of magnitude than that of free carrier in the visible region with a long carrier recombination time. This work clarifies the modulation mechanisms of complex carbon defects in GaN's nonlinear absorption and provides scientific guidance for designing broadband and integrated ultrafast optical nonlinear devices.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"61 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Sylvain Rey, Ferdinand Lédée, Guillaume Freychet, Nicolas Vaxelaire, Jakob Ihrenberger, Eric Gros Daillon, Stéphanie Lombard, Christelle Anglade, Fabrice Emieux, Patrice Gergaud, Louis Grenet
Bulk CsPbBr3 is an emerging semiconductor that has shown unprecedented increase in performance over the last decade for optoelectronic applications. However, further development of devices based on CsPbBr3 is hampered by their poor electrical stability under operation. Migration and accumulation of native ions (Cs+, Pb2+, and Br-) under electric fields has been suggested by many groups to be responsible for the observed device instabilities, although direct experimental evidence of ionic motion during operation has been seldom reported. In our study, ion migration has been probed by grazing incidence x-ray fluorescence (GIXRF) in CsPbBr3 polycrystalline layers grown in vapor phase. Our findings indicate that both Cs and Br experience ionic migration under electric field, suggesting that these ions are responsible for the measured current instability in our devices. In the timescale of a few hours, the ionic drifting rates of mobile Cs and Br under the top electrode were found to be similar, as high as ∼ 20 ppm h−1 V−1 mm. This work paves the way for a better understanding of ion motion issues that play a key role in the optoelectronic properties of CsPbBr3 devices.
{"title":"Quantification of the ionic migration rates in thick CsPbBr3 films revealed by operando x-ray fluorescence","authors":"Sylvain Rey, Ferdinand Lédée, Guillaume Freychet, Nicolas Vaxelaire, Jakob Ihrenberger, Eric Gros Daillon, Stéphanie Lombard, Christelle Anglade, Fabrice Emieux, Patrice Gergaud, Louis Grenet","doi":"10.1063/5.0249790","DOIUrl":"https://doi.org/10.1063/5.0249790","url":null,"abstract":"Bulk CsPbBr3 is an emerging semiconductor that has shown unprecedented increase in performance over the last decade for optoelectronic applications. However, further development of devices based on CsPbBr3 is hampered by their poor electrical stability under operation. Migration and accumulation of native ions (Cs+, Pb2+, and Br-) under electric fields has been suggested by many groups to be responsible for the observed device instabilities, although direct experimental evidence of ionic motion during operation has been seldom reported. In our study, ion migration has been probed by grazing incidence x-ray fluorescence (GIXRF) in CsPbBr3 polycrystalline layers grown in vapor phase. Our findings indicate that both Cs and Br experience ionic migration under electric field, suggesting that these ions are responsible for the measured current instability in our devices. In the timescale of a few hours, the ionic drifting rates of mobile Cs and Br under the top electrode were found to be similar, as high as ∼ 20 ppm h−1 V−1 mm. This work paves the way for a better understanding of ion motion issues that play a key role in the optoelectronic properties of CsPbBr3 devices.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"30 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
D. M. Cheshire, D. Backes, L. S. I. Veiga, S. S. Dhesi, S. A. Cavill
The effect of thermal surface cleaning on the Gilbert damping (α) of yttrium iron garnet (YIG), before capping with a metallic layer, has been investigated. Our results show that α is strongly affected by relatively mild annealing conditions (T = 300 °C) when performed in a vacuum. This increase needs to be taken into account when obtaining the spin-mixing conductance from spin pumping measurements. We measure an increase in α by a factor of ×8 when the YIG is vacuum annealed at 300 °C. No such changes in α are observed when annealed at the same temperature in 1 × 10−1 mbar of oxygen. We suggest that the main driver for the increase in α is the reduction of Fe3+ to Fe2+, as demonstrated by soft x-ray magnetic spectroscopy.
{"title":"Increased Gilbert damping in yttrium iron garnet by low temperature vacuum annealing","authors":"D. M. Cheshire, D. Backes, L. S. I. Veiga, S. S. Dhesi, S. A. Cavill","doi":"10.1063/5.0244429","DOIUrl":"https://doi.org/10.1063/5.0244429","url":null,"abstract":"The effect of thermal surface cleaning on the Gilbert damping (α) of yttrium iron garnet (YIG), before capping with a metallic layer, has been investigated. Our results show that α is strongly affected by relatively mild annealing conditions (T = 300 °C) when performed in a vacuum. This increase needs to be taken into account when obtaining the spin-mixing conductance from spin pumping measurements. We measure an increase in α by a factor of ×8 when the YIG is vacuum annealed at 300 °C. No such changes in α are observed when annealed at the same temperature in 1 × 10−1 mbar of oxygen. We suggest that the main driver for the increase in α is the reduction of Fe3+ to Fe2+, as demonstrated by soft x-ray magnetic spectroscopy.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"7 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
A magnetic skyrmion exhibits topological protection property, making it a highly promising candidate as an information carrier in spintronic devices. However, this information carrier may face deformation issues when driven by high current densities, causing the unstable message transmission. In this work, we explore the skyrmion deformation under different magnetic systems, including ferromagnetic, ferrimagnetic, and antiferromagnetic (AFM) systems. We conduct micromagnetic simulations and provide a theoretical analysis of AFM skyrmion deformation, where the skyrmion demonstrates the lowest susceptibility to deformation. We derive a canting term based on the Thiele equation, pointing out an essential term that explains the AFM deformation depression reason. This finding also indicates that the AFM system offers superior stability for skyrmion, making it a promising choice for better option for skyrmion-based spintronics devices.
{"title":"Skyrmion deformation under the antiferromagnetic system","authors":"Xiuzhu Wang, Zehan Chen, Qiming Shao","doi":"10.1063/5.0253620","DOIUrl":"https://doi.org/10.1063/5.0253620","url":null,"abstract":"A magnetic skyrmion exhibits topological protection property, making it a highly promising candidate as an information carrier in spintronic devices. However, this information carrier may face deformation issues when driven by high current densities, causing the unstable message transmission. In this work, we explore the skyrmion deformation under different magnetic systems, including ferromagnetic, ferrimagnetic, and antiferromagnetic (AFM) systems. We conduct micromagnetic simulations and provide a theoretical analysis of AFM skyrmion deformation, where the skyrmion demonstrates the lowest susceptibility to deformation. We derive a canting term based on the Thiele equation, pointing out an essential term that explains the AFM deformation depression reason. This finding also indicates that the AFM system offers superior stability for skyrmion, making it a promising choice for better option for skyrmion-based spintronics devices.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"72 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Compared to two-dimensional (2D) monolayered ferrovalley semiconductors (FVS), 2D FVS bilayers with interlayer coupling are more sensitive to external electric fields, and their applications for valleytronics and spintronics are very promising. Using first principles calculations, we demonstrate that the valley and spin degeneracy in the SVSiN2 bilayer can be manipulated through different interlayer magnetic orders and stackings. Compared with its monolayer counterpart, the valley/spin polarization in the SVSiN2 bilayer is highly tunable by electric field. Specifically, different stackings, magnetic orders, and vertical electric fields could result in various transport behaviors for the SVSiN2 bilayer, including spin Hall current, valley Hall current, and anomalous Hall current with different valley, spin, and layer combinations. In addition, the AB and AC stacked SVSiN2 bilayers with mirror symmetry breaking exhibit the coexistence of ferrovalley and ferroelectric polarization. Our work provides a theoretical foundation and an effective route to manipulate valley/spin in 2D bilayers.
{"title":"Tunable spin/valley splitting and multiple Hall effects in interlayer coupling-dependent SVSiN2 multiferroic bilayers","authors":"Yunxi Qi, Jun Zhao, Hui Zeng","doi":"10.1063/5.0241163","DOIUrl":"https://doi.org/10.1063/5.0241163","url":null,"abstract":"Compared to two-dimensional (2D) monolayered ferrovalley semiconductors (FVS), 2D FVS bilayers with interlayer coupling are more sensitive to external electric fields, and their applications for valleytronics and spintronics are very promising. Using first principles calculations, we demonstrate that the valley and spin degeneracy in the SVSiN2 bilayer can be manipulated through different interlayer magnetic orders and stackings. Compared with its monolayer counterpart, the valley/spin polarization in the SVSiN2 bilayer is highly tunable by electric field. Specifically, different stackings, magnetic orders, and vertical electric fields could result in various transport behaviors for the SVSiN2 bilayer, including spin Hall current, valley Hall current, and anomalous Hall current with different valley, spin, and layer combinations. In addition, the AB and AC stacked SVSiN2 bilayers with mirror symmetry breaking exhibit the coexistence of ferrovalley and ferroelectric polarization. Our work provides a theoretical foundation and an effective route to manipulate valley/spin in 2D bilayers.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"64 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Diamond and graphene, which have extremely high thermal conductivity, are considered ideal candidates for the preparation of high-performance thermal interface materials (TIMs). However, the development of flexible TIMs with efficient heat transfer paths still hampers their thermal management applications. Herein, a highly oriented diamond–graphene composite film (DGCF) was prepared by one-step microwave plasma chemical vapor deposition on carbon cloth (CC) using N-butylamine as a single liquid carbon source. The hybridized composition of sp3/sp2 and the heat transfer path length of DGCF are regulated by the deposition temperature and the thermal conductivity of CC/DGCF at 30 °C is 2.71 W m−1 K−1, which is 15 times higher than that of CC. Further flexible TIMs of CC/DGCF are achieved using thermal silicone grease (TG) as filler, and the thermal conductivity of the final flexible compound of CC/DGCF/TG is 6.97 W m−1 K−1 at 30 °C, which is 39 times higher than that of pure CC and 2 times higher than that of TG, respectively. In the actual TIMs performance test, the cooling efficiency is 1.4 times higher than that of the commercial thermal conductive silicone pad. Furthermore, finite element simulations demonstrated that the film at 800 °C has the optimal sp3/sp2 ratio for thermal response and the best thermal conductivity path structure. This finding provides a method for the design of highly flexible TIMs and increases the possibility of their practical application in electronic thermal management.
{"title":"Flexible thermal interface materials based on diamond–graphene composite films prepared at different temperatures","authors":"Yifan Xu, Huiqiang Liu, Bing Wang, Wen Zhang, Zhaoxin Zhong, Chao Long, Xu Lin, Xian Jian, Ying Xiong","doi":"10.1063/5.0255818","DOIUrl":"https://doi.org/10.1063/5.0255818","url":null,"abstract":"Diamond and graphene, which have extremely high thermal conductivity, are considered ideal candidates for the preparation of high-performance thermal interface materials (TIMs). However, the development of flexible TIMs with efficient heat transfer paths still hampers their thermal management applications. Herein, a highly oriented diamond–graphene composite film (DGCF) was prepared by one-step microwave plasma chemical vapor deposition on carbon cloth (CC) using N-butylamine as a single liquid carbon source. The hybridized composition of sp3/sp2 and the heat transfer path length of DGCF are regulated by the deposition temperature and the thermal conductivity of CC/DGCF at 30 °C is 2.71 W m−1 K−1, which is 15 times higher than that of CC. Further flexible TIMs of CC/DGCF are achieved using thermal silicone grease (TG) as filler, and the thermal conductivity of the final flexible compound of CC/DGCF/TG is 6.97 W m−1 K−1 at 30 °C, which is 39 times higher than that of pure CC and 2 times higher than that of TG, respectively. In the actual TIMs performance test, the cooling efficiency is 1.4 times higher than that of the commercial thermal conductive silicone pad. Furthermore, finite element simulations demonstrated that the film at 800 °C has the optimal sp3/sp2 ratio for thermal response and the best thermal conductivity path structure. This finding provides a method for the design of highly flexible TIMs and increases the possibility of their practical application in electronic thermal management.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"20 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Soroush Arabi, Qili Li, Ritika Dhundhwal, Dirk Fuchs, Thomas Reisinger, Ioan M. Pop, Wulf Wulfhekel
In the fabrication of superconducting devices, both in situ and ex situ processes are utilized, making the removal of unwanted oxide layers and impurities under vacuum conditions crucial. Oxygen descumming and argon milling are standard in situ cleaning methods employed for device preparation. We investigated the impact of these techniques on tantalum superconducting thin films using scanning tunneling microscopy at millikelvin temperatures. We demonstrate that these cleaning methods inadvertently introduce magnetic bound states within the superconducting gap of tantalum, likely by oxygen impurities. These bound states can be detrimental to superconducting qubit devices, as they add to dephasing and energy relaxation.
{"title":"Magnetic bound states embedded in tantalum superconducting thin films","authors":"Soroush Arabi, Qili Li, Ritika Dhundhwal, Dirk Fuchs, Thomas Reisinger, Ioan M. Pop, Wulf Wulfhekel","doi":"10.1063/5.0251996","DOIUrl":"https://doi.org/10.1063/5.0251996","url":null,"abstract":"In the fabrication of superconducting devices, both in situ and ex situ processes are utilized, making the removal of unwanted oxide layers and impurities under vacuum conditions crucial. Oxygen descumming and argon milling are standard in situ cleaning methods employed for device preparation. We investigated the impact of these techniques on tantalum superconducting thin films using scanning tunneling microscopy at millikelvin temperatures. We demonstrate that these cleaning methods inadvertently introduce magnetic bound states within the superconducting gap of tantalum, likely by oxygen impurities. These bound states can be detrimental to superconducting qubit devices, as they add to dephasing and energy relaxation.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"22 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Yanbin Chen, Yu Zhang, Xianghan Li, Lei Zhang, Meifeng Xu, Chaonan Wang
Titanium dioxide (TiO2) is widely employed as an electron transport layer in perovskite solar cells due to its low manufacturing cost and favorable energy-level alignment. However, the suboptimal quality of TiO2 films and the presence of multiple defects at the TiO2/perovskite interface, such as uncoordinated Pb2+ and oxygen vacancy defects, significantly compromise both device efficiency and stability. This study proposes a synergistic passivation strategy through the introduction of an acetylamino-functionalized interlayer between the perovskite and TiO2. The acetylamino groups within the passivation layer establish strong interactions with uncoordinated Pb2+ in the perovskite, thereby enhancing interface stability. Acetylamino groups can also interact with the TiO2 layer by bonding with Ti4+ and reducing oxygen vacancy defects, thereby enhancing the electron transport potential of the TiO2 layer. The enhanced hydrophobicity of the TiO2 film, induced by the passivation layer, further promotes perovskite crystallization by minimizing surface tension effects during film growth. Therefore, the device efficiency significantly increased from 16.49% to 19.26%. The lifetime of the unencapsulated device was evaluated under environmental conditions (relative humidity: 30% ± 5%, temperature: 25 ± 5 °C). The efficiency of the unmodified device decreased to 75.3% after 800 h, whereas the modified device maintained 90.1% of its initial efficiency, demonstrating higher stability.
{"title":"Synergic passivation of the interface between TiO2 and perovskite by multifunctional small molecules","authors":"Yanbin Chen, Yu Zhang, Xianghan Li, Lei Zhang, Meifeng Xu, Chaonan Wang","doi":"10.1063/5.0255283","DOIUrl":"https://doi.org/10.1063/5.0255283","url":null,"abstract":"Titanium dioxide (TiO2) is widely employed as an electron transport layer in perovskite solar cells due to its low manufacturing cost and favorable energy-level alignment. However, the suboptimal quality of TiO2 films and the presence of multiple defects at the TiO2/perovskite interface, such as uncoordinated Pb2+ and oxygen vacancy defects, significantly compromise both device efficiency and stability. This study proposes a synergistic passivation strategy through the introduction of an acetylamino-functionalized interlayer between the perovskite and TiO2. The acetylamino groups within the passivation layer establish strong interactions with uncoordinated Pb2+ in the perovskite, thereby enhancing interface stability. Acetylamino groups can also interact with the TiO2 layer by bonding with Ti4+ and reducing oxygen vacancy defects, thereby enhancing the electron transport potential of the TiO2 layer. The enhanced hydrophobicity of the TiO2 film, induced by the passivation layer, further promotes perovskite crystallization by minimizing surface tension effects during film growth. Therefore, the device efficiency significantly increased from 16.49% to 19.26%. The lifetime of the unencapsulated device was evaluated under environmental conditions (relative humidity: 30% ± 5%, temperature: 25 ± 5 °C). The efficiency of the unmodified device decreased to 75.3% after 800 h, whereas the modified device maintained 90.1% of its initial efficiency, demonstrating higher stability.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"2 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
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