Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale...Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale PtTe_(2)films by the pulsed laser deposition(PLD)and the comparison of the magnetotransport properties with the PtTe2films grown by the chemical vapor deposition(CVD).The low-temperature Hall curves of the PLD-grown films exhibit a linear behavior,in contrast with the nonlinear characteristic of the Hall behavior observed in CVD-grown films,in which a defect gradient is introduced.Meanwhile,both PtTe2films show weak antilocalization at low temperatures,which is attributed to the strong spin–orbit coupling.展开更多
Nickel oxide(NiO)based gas sensors have at-tracted intense attention due to its high re-sponse to hydrogen sulfide(H_(2)S)gas.It has been demonstrated that the NiO sensors with exposed(111)facet exhibit excellent perf...Nickel oxide(NiO)based gas sensors have at-tracted intense attention due to its high re-sponse to hydrogen sulfide(H_(2)S)gas.It has been demonstrated that the NiO sensors with exposed(111)facet exhibit excellent perfor-mance,but the single-orientation NiO sensors with exposed(111)facet have rarely been studied.In this work,high quality(111)-ori-ented NiO epitaxial films were fabricated by pulsed laser deposition.Detailed crystalline structural information was revealed by using synchrotron based X-ray diffraction(XRD)technology.These NiO thin films show good se-lectivity for H_(2)S gas detection.Without further modification,the highest response to 100 ppm H_(2)S was measured to be 13.07 at 300℃,and limit of detection(LOD)could be as low as 186 ppb.Fitting of the electrical response curves during adsorption and desorption of H_(2)S gas indicates the two-site Langmuir kinetic processes.Combining with XPS and XAS measure-ments,the mechanism was discussed.Density functional theory(DFT)calculations show that NiO with exposed(111)facets has the most negative adsorption energy,indicating more sen-sitive to H_(2)S.These results could inspire more studies of metal oxide semiconductor-based gas sensors with specific surface.展开更多
Compared to traditional perovskite ferroelectric materials,HfO_(2) has emerged as a prominent research focus due to its ability to retain significant ferroelectricity at the nanoscale.However,systematic studies on its...Compared to traditional perovskite ferroelectric materials,HfO_(2) has emerged as a prominent research focus due to its ability to retain significant ferroelectricity at the nanoscale.However,systematic studies on its performance in thicker films remain limited,leaving the intrinsic relationship between thickness variation and ferroelectric properties poorly understood.In this work,we successfully fabricated doped HfO_(2)-based ferroelectric thin films with thicknesses spanning tens to hundreds of nanometers.All these films exhibit robust ferroelectric characteristics,and their ferroelectric properties demonstrate a non-monotonic evolution with increasing thickness.Macroscopic electrical measurements and mesoscale domain switching analysis confirmed that the ferroelectric properties of Ce:HfO_(2) films first diminish and then recover with the increase of film thickness.By further characterizing the evolution of microscopic structures,we elucidate the thickness effects on the grain size distribution and domain structure evolution.This framework clarifies the physical mechanism underlying the thickness-dependent ferroelectric behavior.Our findings provide critical experimental evidence for developing large-scale HfO_(2)-based ferroelectric devices and lay a theoretical foundation for optimizing thick-film ferroelectric materials for practical applications.展开更多
Tetravalent tin(Sn4+)-based inorganic perovskite semiconductors like Cs_(2)SnI_(6)are expected to replace lead-based perovskite counterparts due to advantages such as structural stability and environmental friendlines...Tetravalent tin(Sn4+)-based inorganic perovskite semiconductors like Cs_(2)SnI_(6)are expected to replace lead-based perovskite counterparts due to advantages such as structural stability and environmental friendliness.In this paper,we reported the dopant compensation effect in the component-dependent self-doped(111)-oriented Cs_(2)SnI_(6)thin films grown with pulsed laser deposition(PLD)at room temperature.The films were grown on(100)-SrTiO_(3)(STO)substrates at room temperature by PLD.Hall results of the Cs_(2)SnI_(6)films with different components realizing by controlling the ratio of SnI_(4)/CsI in the targets demonstrate a clear change of conductivity type from N-type to P-type,while the carrier concentration decreases from 1018 to 1013 and accordingly the film resistivity increases significantly from 3.8 to 2506Ωcm.The defect-relatedopticalfingerprints of Cs_(2)SnI_(6)films werealsoinvestigated withtemperature-dependent photoluminescence spectroscopy.At low temperatures of 10 K,the Cs_(2)SnI_(6)films exhibit donor-bound(D^(0)X)and donor-acceptor pair(DAP)emission,respectively,due to the self-doping effect.These re-sults indicate that controlling the composition of the PLD target is a powerful way to tune the electrical properties of Cs_(2)SnI_(6)films for possible applications in solar cells or X-ray detectors.展开更多
Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by...Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.展开更多
Innovative use of HfO_(2)-based high-dielectric-permittivity materials could enable their integration into few-nanometre-scale devices for storing substantial quantities of electrical charges,which have received wides...Innovative use of HfO_(2)-based high-dielectric-permittivity materials could enable their integration into few-nanometre-scale devices for storing substantial quantities of electrical charges,which have received widespread applications in high-storage-density dynamic random access memory and energy-efficient complementary metal-oxide-semiconductor devices.During bipolar high electric-field cycling in numbers close to dielectric breakdown,the dielectric permittivity suddenly increases by 30 times after oxygen-vacancy ordering and ferroelectric-to-nonferroelectric phase transition of near-edge plasma-treated Hf_(0.5)Zr_(0.5)O_(2) thin-film capacitors.Here we report a much higher dielectric permittivity of 1466 during downscaling of the capacitor into the diameter of 3.85μm when the ferroelectricity suddenly disappears without high-field cycling.The stored charge density is as high as 183μC cm^(−2) at an operating voltage/time of 1.2 V/50 ns at cycle numbers of more than 10^(12) without inducing dielectric breakdown.The study of synchrotron X-ray micro-diffraction patterns show missing of a mixed tetragonal phase.The image of electron energy loss spectroscopy shows the preferred oxygen-vacancy accumulation at the regions near top/bottom electrodes as well as grain boundaries.The ultrahigh dielectric-permittivity material enables high-density integration of extremely scaled logic and memory devices in the future.展开更多
The pressing demand for ultrathin and flexible shields to counter electromagnetic interference(EMI)has sparked interest in Ti_(3)C_(2)T_(x)MXene materials due to their exceptional electrical conductivity,tunable surfa...The pressing demand for ultrathin and flexible shields to counter electromagnetic interference(EMI)has sparked interest in Ti_(3)C_(2)T_(x)MXene materials due to their exceptional electrical conductivity,tunable surface chemistry,and layered structure.However,pure Ti_(3)C_(2)T_(x)MXene films often lack the mechanical properties required for practical engineering applications,and traditional reinforcement methods tend to reduce electrical conductivity.This work demonstrates an effective strategy to enhance the alignment and densely packed layered structure of Ti_(3)C_(2)T_(x)MXene films by regulating the acidity and alkalinity of Ti_(3)C_(2)T_(x)MXene aqueous solutions.This approach simultaneously improves mechanical strength and electromagnetic interference shielding effectiveness(EMI SE).Compared with original Ti_(3)C_(2)T_(x)MXene films,MXene films modified with ammonia solution(NH_(3)·H_(2)O)via OH-show a significant improvement in tensile strength(27.7±1.9 MPa).Meanwhile,MXene films treated with hydrochloric acid(HCl)via H^(+)reach an even higher tensile strength of 39±1.5 MPa.Moreover,the EMI SE values of the treated MXene films increase significantly,each reaching 66.2 and 58.4 dB.The maximum improvements in EMI SE values for the acid-and alkali-treated samples are 17.9%and 4%,respectively.In conclusion,the simultaneous enhancement of mechanical strength and EMI shielding efficacy highlights the potential of acid-and alkali-treated Ti_(3)C_(2)T_(x)MXene films for applications in ultrathin and flexible EMI shielding materials.展开更多
To mitigate secondary electromagnetic pollution,there is an urgent need to develop absorption-dominant electromagnetic interference(EMI)shielding materials with low density,reduced thickness,lightweight construction,f...To mitigate secondary electromagnetic pollution,there is an urgent need to develop absorption-dominant electromagnetic interference(EMI)shielding materials with low density,reduced thickness,lightweight construction,flexibility,exceptional mechanical strength,and superior electrothermal and photothermal properties,particularly for flexible and wearable electronics.In this regard,we designed an absorption-based composite film comprising carbon nanotubes(CNT)and α-Fe_(2)O_(3),featuring a CNT layer sandwiched between twoα-Fe_(2)O_(3)layers on the upper and lower surfaces.This composite film was fabricated through an electrodeposition process followed by a thermal annealing procedure to achieve enhanced EMI shielding performance along with improved electrothermal and photothermal properties.The strategically designed sandwich structure allows the rough surface of the upper α-Fe_(2)O_(3)layer to not only improve the impedance mismatch between free space and the composite film,facilitating the penetration of incident electromagnetic(EM)waves into the film and promoting increased EM absorption rather than reflection,but also to enhance electrical conductivity,thereby improving electron mobility and density.Consequently,the average total shielding effectiveness(SE)of the CNT/Fe_(16)-300 composite demonstrates remarkable EMI shielding effectiveness(EMI SE:56.8 dB).Furthermore,the alteration in the absorption-to-reflection ratio(A/R)signifies a transition in the EMI shielding mechanism from reflection(0.69 for the pristine CNT film)to absorption(1.86 for the CNT/Fe_(16)-300)with the incremental deposition of α-Fe_(2)O_(3)nanoparticles.This work presents a feasible manufacturing approach for developing composite films with a sandwich structure that exhibits absorption-dominant EMI shielding capabilities,contributing to advancements in thermal management and multifunctional electromagnetic shielding applications.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1402404)the National Natural Science Foundation of China(Grant Nos.T2394473,624B2070,and 62274085)。
文摘Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale PtTe_(2)films by the pulsed laser deposition(PLD)and the comparison of the magnetotransport properties with the PtTe2films grown by the chemical vapor deposition(CVD).The low-temperature Hall curves of the PLD-grown films exhibit a linear behavior,in contrast with the nonlinear characteristic of the Hall behavior observed in CVD-grown films,in which a defect gradient is introduced.Meanwhile,both PtTe2films show weak antilocalization at low temperatures,which is attributed to the strong spin–orbit coupling.
基金supported by the National Key Research and Development Program of China(No.2022YFA1603902)the National Natural Science Foundation of China(No.12175235,No.62271462,and No.12004407)。
文摘Nickel oxide(NiO)based gas sensors have at-tracted intense attention due to its high re-sponse to hydrogen sulfide(H_(2)S)gas.It has been demonstrated that the NiO sensors with exposed(111)facet exhibit excellent perfor-mance,but the single-orientation NiO sensors with exposed(111)facet have rarely been studied.In this work,high quality(111)-ori-ented NiO epitaxial films were fabricated by pulsed laser deposition.Detailed crystalline structural information was revealed by using synchrotron based X-ray diffraction(XRD)technology.These NiO thin films show good se-lectivity for H_(2)S gas detection.Without further modification,the highest response to 100 ppm H_(2)S was measured to be 13.07 at 300℃,and limit of detection(LOD)could be as low as 186 ppb.Fitting of the electrical response curves during adsorption and desorption of H_(2)S gas indicates the two-site Langmuir kinetic processes.Combining with XPS and XAS measure-ments,the mechanism was discussed.Density functional theory(DFT)calculations show that NiO with exposed(111)facets has the most negative adsorption energy,indicating more sen-sitive to H_(2)S.These results could inspire more studies of metal oxide semiconductor-based gas sensors with specific surface.
基金supported by the National Natural Science Foundation of China(Nos.12372331,12072307,and 12302429)the Science and Technology Innovation Program of Hunan Province,China(No.2024RC3160)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110116).
文摘Compared to traditional perovskite ferroelectric materials,HfO_(2) has emerged as a prominent research focus due to its ability to retain significant ferroelectricity at the nanoscale.However,systematic studies on its performance in thicker films remain limited,leaving the intrinsic relationship between thickness variation and ferroelectric properties poorly understood.In this work,we successfully fabricated doped HfO_(2)-based ferroelectric thin films with thicknesses spanning tens to hundreds of nanometers.All these films exhibit robust ferroelectric characteristics,and their ferroelectric properties demonstrate a non-monotonic evolution with increasing thickness.Macroscopic electrical measurements and mesoscale domain switching analysis confirmed that the ferroelectric properties of Ce:HfO_(2) films first diminish and then recover with the increase of film thickness.By further characterizing the evolution of microscopic structures,we elucidate the thickness effects on the grain size distribution and domain structure evolution.This framework clarifies the physical mechanism underlying the thickness-dependent ferroelectric behavior.Our findings provide critical experimental evidence for developing large-scale HfO_(2)-based ferroelectric devices and lay a theoretical foundation for optimizing thick-film ferroelectric materials for practical applications.
基金financially supported by the National Key Re-search and Development Program of China(No.2022YFC3700801)the Key R&D Program of Shandong Province,China(No.2024SFGC0102),the Jinan Bureau of Education(No.JNSX2023015)the Jinan Bureau of Science and Technology(No.202333042).
文摘Tetravalent tin(Sn4+)-based inorganic perovskite semiconductors like Cs_(2)SnI_(6)are expected to replace lead-based perovskite counterparts due to advantages such as structural stability and environmental friendliness.In this paper,we reported the dopant compensation effect in the component-dependent self-doped(111)-oriented Cs_(2)SnI_(6)thin films grown with pulsed laser deposition(PLD)at room temperature.The films were grown on(100)-SrTiO_(3)(STO)substrates at room temperature by PLD.Hall results of the Cs_(2)SnI_(6)films with different components realizing by controlling the ratio of SnI_(4)/CsI in the targets demonstrate a clear change of conductivity type from N-type to P-type,while the carrier concentration decreases from 1018 to 1013 and accordingly the film resistivity increases significantly from 3.8 to 2506Ωcm.The defect-relatedopticalfingerprints of Cs_(2)SnI_(6)films werealsoinvestigated withtemperature-dependent photoluminescence spectroscopy.At low temperatures of 10 K,the Cs_(2)SnI_(6)films exhibit donor-bound(D^(0)X)and donor-acceptor pair(DAP)emission,respectively,due to the self-doping effect.These re-sults indicate that controlling the composition of the PLD target is a powerful way to tune the electrical properties of Cs_(2)SnI_(6)films for possible applications in solar cells or X-ray detectors.
基金supported by the National Key Research and Development Program of China(No.2021YFA0715600)the National Natural Science Foundation of China(Nos.62274125,52192611)+2 种基金the Guangdong Basic and Applied Basic Research Fund(No.2023A1515030084)the Key Research and Development Program of Shaanxi Province(Grant No.2024GX-YBXM-410)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202220).
文摘Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.
基金supported by the National Key Basic Research Program of China (2022YFA1402904)Basic Research Project of Shanghai Science and Technology Innovation Action (grant number 24CL2900900)the National Natural Science Foundation of China (grant number 61904034)
文摘Innovative use of HfO_(2)-based high-dielectric-permittivity materials could enable their integration into few-nanometre-scale devices for storing substantial quantities of electrical charges,which have received widespread applications in high-storage-density dynamic random access memory and energy-efficient complementary metal-oxide-semiconductor devices.During bipolar high electric-field cycling in numbers close to dielectric breakdown,the dielectric permittivity suddenly increases by 30 times after oxygen-vacancy ordering and ferroelectric-to-nonferroelectric phase transition of near-edge plasma-treated Hf_(0.5)Zr_(0.5)O_(2) thin-film capacitors.Here we report a much higher dielectric permittivity of 1466 during downscaling of the capacitor into the diameter of 3.85μm when the ferroelectricity suddenly disappears without high-field cycling.The stored charge density is as high as 183μC cm^(−2) at an operating voltage/time of 1.2 V/50 ns at cycle numbers of more than 10^(12) without inducing dielectric breakdown.The study of synchrotron X-ray micro-diffraction patterns show missing of a mixed tetragonal phase.The image of electron energy loss spectroscopy shows the preferred oxygen-vacancy accumulation at the regions near top/bottom electrodes as well as grain boundaries.The ultrahigh dielectric-permittivity material enables high-density integration of extremely scaled logic and memory devices in the future.
基金supported by the National Key R&D Program of China(No.2019YFA0706802)the National Natural Science Foundation of China(Nos.52273085 and 52303113)Key Scientific Research Projects of Colleges and Universities in Henan Province,China(No.24A430045).
文摘The pressing demand for ultrathin and flexible shields to counter electromagnetic interference(EMI)has sparked interest in Ti_(3)C_(2)T_(x)MXene materials due to their exceptional electrical conductivity,tunable surface chemistry,and layered structure.However,pure Ti_(3)C_(2)T_(x)MXene films often lack the mechanical properties required for practical engineering applications,and traditional reinforcement methods tend to reduce electrical conductivity.This work demonstrates an effective strategy to enhance the alignment and densely packed layered structure of Ti_(3)C_(2)T_(x)MXene films by regulating the acidity and alkalinity of Ti_(3)C_(2)T_(x)MXene aqueous solutions.This approach simultaneously improves mechanical strength and electromagnetic interference shielding effectiveness(EMI SE).Compared with original Ti_(3)C_(2)T_(x)MXene films,MXene films modified with ammonia solution(NH_(3)·H_(2)O)via OH-show a significant improvement in tensile strength(27.7±1.9 MPa).Meanwhile,MXene films treated with hydrochloric acid(HCl)via H^(+)reach an even higher tensile strength of 39±1.5 MPa.Moreover,the EMI SE values of the treated MXene films increase significantly,each reaching 66.2 and 58.4 dB.The maximum improvements in EMI SE values for the acid-and alkali-treated samples are 17.9%and 4%,respectively.In conclusion,the simultaneous enhancement of mechanical strength and EMI shielding efficacy highlights the potential of acid-and alkali-treated Ti_(3)C_(2)T_(x)MXene films for applications in ultrathin and flexible EMI shielding materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52222202 and 51772310)Chinese Academy of Sciences Key Research Program of Frontier Sciences(No.QYZDY-SSWJSC031)Shanghai Pilot Program for Basic Research-Chinese Academy of Science,Shanghai Branch(No.JCYJ-SHFY-2021-001).
文摘To mitigate secondary electromagnetic pollution,there is an urgent need to develop absorption-dominant electromagnetic interference(EMI)shielding materials with low density,reduced thickness,lightweight construction,flexibility,exceptional mechanical strength,and superior electrothermal and photothermal properties,particularly for flexible and wearable electronics.In this regard,we designed an absorption-based composite film comprising carbon nanotubes(CNT)and α-Fe_(2)O_(3),featuring a CNT layer sandwiched between twoα-Fe_(2)O_(3)layers on the upper and lower surfaces.This composite film was fabricated through an electrodeposition process followed by a thermal annealing procedure to achieve enhanced EMI shielding performance along with improved electrothermal and photothermal properties.The strategically designed sandwich structure allows the rough surface of the upper α-Fe_(2)O_(3)layer to not only improve the impedance mismatch between free space and the composite film,facilitating the penetration of incident electromagnetic(EM)waves into the film and promoting increased EM absorption rather than reflection,but also to enhance electrical conductivity,thereby improving electron mobility and density.Consequently,the average total shielding effectiveness(SE)of the CNT/Fe_(16)-300 composite demonstrates remarkable EMI shielding effectiveness(EMI SE:56.8 dB).Furthermore,the alteration in the absorption-to-reflection ratio(A/R)signifies a transition in the EMI shielding mechanism from reflection(0.69 for the pristine CNT film)to absorption(1.86 for the CNT/Fe_(16)-300)with the incremental deposition of α-Fe_(2)O_(3)nanoparticles.This work presents a feasible manufacturing approach for developing composite films with a sandwich structure that exhibits absorption-dominant EMI shielding capabilities,contributing to advancements in thermal management and multifunctional electromagnetic shielding applications.
