The two-dimensional electron gas(2DEG)generated at the LaAlO3/SrTiO3 interface has been in the focus of oxides re-search since its first discovery.Although oxygen vacancies play an important role in the generation of ...The two-dimensional electron gas(2DEG)generated at the LaAlO3/SrTiO3 interface has been in the focus of oxides re-search since its first discovery.Although oxygen vacancies play an important role in the generation of the insulator-to-metal transition of the SrTiO3 bare surface,their contribution at the LaAlO3/SrTiO3 interface remains unclear.In this work,we investigated a LaAlO3/SrTiO3 heterostructure with regional distribution of defect-based localized polar sites at the interface.Using static and time-resolved threshold photoemission electron microscopy,we prove that oxygen vacan-cies are induced near those polar sites,resulting in the increase of carrier density of the 2DEG states.In addition,oxy-gen-related surface states were uncovered,which we attributed to the release of lattice oxygen during the formation of oxygen vacancies.Such effects are mainly found spatially located around the defect sites at the buried interface,while other regions remain unaffected.Our results confirm that the itinerant electrons induced by oxygen vacancies can coex-ist with the charge transfer mechanism in the LaAlO3/SrTiO3 heterostructure,together leading to the formation of the metallic interface.These observations provide fundamental insights into the nature of LaAlO3/SrTiO3 interface based 2DEG and unique perspectives for potential applications.展开更多
Transparent thermoelectric CdO thin films exhibit critical flexibility and thermoelectric performance that require focused research to advance flexible transparent self-powered devices.Here,we demon-strate the superio...Transparent thermoelectric CdO thin films exhibit critical flexibility and thermoelectric performance that require focused research to advance flexible transparent self-powered devices.Here,we demon-strate the superior flexibility of freestanding single-crystalline CdO membranes.These membranes achieve a notable room-temperature power factor of 1.48μW·cm^(-1)·K^(-2) and exhibit superior optical transmittance exceeding 94%in the 550–800 nm range.Crucially,freestanding CdO exhibits exceptional mechanical robustness,retaining>90%electrical conductivity after 1000 bending cycles(radius:11.5 mm).Microstructure analyses confirm polycrystalline CdO films suffer from grain boundary cracking under bending due to stress concentration,but single-crystal CdO membranes—without grain boundaries to concentrate stress—exhibit better flexibility and resistance to cracking.Furthermore,curvature-induced strain boosts the power factor by 12.8%,providing a curvature-controlled strain engineering strategy to optimize flexible thermoelectric performance.This work establishes free-standing CdO as a highly efficient and flexible thermoelectric material and suggests a fundamental strategy for designing robust smart materials for transparent,self-powered flexible electronics.展开更多
基金supported by the National Key Research and Development Program of China under Grant Nos.2018YFB2200403 and 2018YFA0704404the National Natural Science Foundation of China under Grant Nos.61775003,11734001,91950204,11527901+1 种基金Beijing Municipal Science&Technology Commission No.Z191100007219001support by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-TRR 173-268565370(projects A02).
文摘The two-dimensional electron gas(2DEG)generated at the LaAlO3/SrTiO3 interface has been in the focus of oxides re-search since its first discovery.Although oxygen vacancies play an important role in the generation of the insulator-to-metal transition of the SrTiO3 bare surface,their contribution at the LaAlO3/SrTiO3 interface remains unclear.In this work,we investigated a LaAlO3/SrTiO3 heterostructure with regional distribution of defect-based localized polar sites at the interface.Using static and time-resolved threshold photoemission electron microscopy,we prove that oxygen vacan-cies are induced near those polar sites,resulting in the increase of carrier density of the 2DEG states.In addition,oxy-gen-related surface states were uncovered,which we attributed to the release of lattice oxygen during the formation of oxygen vacancies.Such effects are mainly found spatially located around the defect sites at the buried interface,while other regions remain unaffected.Our results confirm that the itinerant electrons induced by oxygen vacancies can coex-ist with the charge transfer mechanism in the LaAlO3/SrTiO3 heterostructure,together leading to the formation of the metallic interface.These observations provide fundamental insights into the nature of LaAlO3/SrTiO3 interface based 2DEG and unique perspectives for potential applications.
基金supported by the National Natural Sci-ence Foundation of China(Grant No.11604073,No.51972094)the Nature Science Foundation of Hebei Province(Grant No.A2017201104,E2017201227)+3 种基金the Natural Science Foundation of Educational Department of Hebei Province(BJ2017046)the Basic Research Project of Educational Department of Hebei Province(JZX2024008)the Science and Technology Plan Project of Hebei Province(246Z4401G)the Science and Technology Plan Project of Hebei Province(Grant No.246Z4307G).
文摘Transparent thermoelectric CdO thin films exhibit critical flexibility and thermoelectric performance that require focused research to advance flexible transparent self-powered devices.Here,we demon-strate the superior flexibility of freestanding single-crystalline CdO membranes.These membranes achieve a notable room-temperature power factor of 1.48μW·cm^(-1)·K^(-2) and exhibit superior optical transmittance exceeding 94%in the 550–800 nm range.Crucially,freestanding CdO exhibits exceptional mechanical robustness,retaining>90%electrical conductivity after 1000 bending cycles(radius:11.5 mm).Microstructure analyses confirm polycrystalline CdO films suffer from grain boundary cracking under bending due to stress concentration,but single-crystal CdO membranes—without grain boundaries to concentrate stress—exhibit better flexibility and resistance to cracking.Furthermore,curvature-induced strain boosts the power factor by 12.8%,providing a curvature-controlled strain engineering strategy to optimize flexible thermoelectric performance.This work establishes free-standing CdO as a highly efficient and flexible thermoelectric material and suggests a fundamental strategy for designing robust smart materials for transparent,self-powered flexible electronics.
