The ability to combine continuously tunable narrow-band terahertz(THz)generation that can access both the farinfrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifyin...The ability to combine continuously tunable narrow-band terahertz(THz)generation that can access both the farinfrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifying underlying light-matter interactions and realizing selective control of rotational or vibrational resonances in nanoparticles or molecules.Here,we report selective difference frequency generation with over 100 THz bandwidth via femtosecond optical pulse shaping.The THz emission is generated at nanoscale junctions at the interface of LaAlO_(3)/SrTiO_(3)(LAO/STO)that is defined by conductive atomic force microscope lithography,with the potential to perform THz spectroscopy on individual nanoparticles or molecules.Numerical simulation of the time-domain signal facilitates the identification of components that contribute to the THz generation.This ultra-wide-bandwidth tunable nanoscale coherent THz source transforms the LAO/STO interface into a promising platform for integrated lab-on-chip optoelectronic devices with various functionalities.展开更多
LaAlO_(3)/SrTiO_(3)(LAO/STO)heterostructures have shown a strong persistent photoconductivity(PPC)at room temperature.The abnormally strong PPC has attracted immense research interest due to its possible applications ...LaAlO_(3)/SrTiO_(3)(LAO/STO)heterostructures have shown a strong persistent photoconductivity(PPC)at room temperature.The abnormally strong PPC has attracted immense research interest due to its possible applications in optically-tunable electronic devices.Despite its promise,the fundamental understanding of the PPC in the LAO/STO heterostructures is still elusive.Herein,we report that the giant PPC origi-nates from the photo-induced valence change in oxygen vacancies near the LAO/STO interface.Our spec-tral analysis of the photocurrent and the model-fitting study consistently show that the ionized oxygen vacancies near the interface are neutralized during the electron relaxation process.They hinder the complete relaxation of the photoexcited electrons by the deeply-located oxygen vacancies and result in the strong PPC.The change in the ionization state distribution of the oxygen vacancies is probed by the per-sistent noise behavior at the frequency between 1 kHz and 20 kHz regime.These results provide insight into the role of oxygen vacancies in influencing the internal charge distribution and triggering the PPC phenomena in complex oxide heterostructures.展开更多
基金supported by the Office of Naval Research(N00014-16-1-3152)AFOSR FA9550-15-1-0334(C.B.E.)+5 种基金grants from the National Science Foundation DMR-1629270(C.B.E.)MRSEC,DMR-1420645(C.B.E)support from a National Science Foundation Graduate Research Fellowship Program under Grant No.1747452supports from the Vannevar Bush Faculty Fellowship programby the Basic Research Office of the Assistant Secretary of Defense for Research and Engineeringfunded by the Office of Naval Research through grant N00014-15-1-2847.
文摘The ability to combine continuously tunable narrow-band terahertz(THz)generation that can access both the farinfrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifying underlying light-matter interactions and realizing selective control of rotational or vibrational resonances in nanoparticles or molecules.Here,we report selective difference frequency generation with over 100 THz bandwidth via femtosecond optical pulse shaping.The THz emission is generated at nanoscale junctions at the interface of LaAlO_(3)/SrTiO_(3)(LAO/STO)that is defined by conductive atomic force microscope lithography,with the potential to perform THz spectroscopy on individual nanoparticles or molecules.Numerical simulation of the time-domain signal facilitates the identification of components that contribute to the THz generation.This ultra-wide-bandwidth tunable nanoscale coherent THz source transforms the LAO/STO interface into a promising platform for integrated lab-on-chip optoelectronic devices with various functionalities.
基金This work is supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Nos.2021R1C1C1011219 and2021R1A4A1032085)K.Eomwould like to acknowledge the support by National Research Founda-tion of Korea through the Basic Science Research Program(NRF-2022R1C1C2010693)J.W.Lee acknowledges the support from Ba-sic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2022R1I1A1A01068965).
文摘LaAlO_(3)/SrTiO_(3)(LAO/STO)heterostructures have shown a strong persistent photoconductivity(PPC)at room temperature.The abnormally strong PPC has attracted immense research interest due to its possible applications in optically-tunable electronic devices.Despite its promise,the fundamental understanding of the PPC in the LAO/STO heterostructures is still elusive.Herein,we report that the giant PPC origi-nates from the photo-induced valence change in oxygen vacancies near the LAO/STO interface.Our spec-tral analysis of the photocurrent and the model-fitting study consistently show that the ionized oxygen vacancies near the interface are neutralized during the electron relaxation process.They hinder the complete relaxation of the photoexcited electrons by the deeply-located oxygen vacancies and result in the strong PPC.The change in the ionization state distribution of the oxygen vacancies is probed by the per-sistent noise behavior at the frequency between 1 kHz and 20 kHz regime.These results provide insight into the role of oxygen vacancies in influencing the internal charge distribution and triggering the PPC phenomena in complex oxide heterostructures.
