SrTiO3 (STO) thin films of different thicknesses were deposited on MgAl2O4 (MAO) substrates to investigate the in-plane strain effect on the soft-mode frequency of the STO films. X-ray reciprocal space mapping (X-RSM)...SrTiO3 (STO) thin films of different thicknesses were deposited on MgAl2O4 (MAO) substrates to investigate the in-plane strain effect on the soft-mode frequency of the STO films. X-ray reciprocal space mapping (X-RSM) results indicate that there was no relaxation of the in-plane lattice strain of the STO films on MAO. Shifts in the soft-mode frequencies with a decrease in the film thickness were observed using terahertz time-domain spectroscopy (THz-TDS). However, despite the larger lattice mismatch between STO and MAO than that between STO and DyScO3 (DSO), the shifts in the soft-mode frequencies of the STO films on MAO were smaller than those on DSO. The results indicate that the soft-mode frequencies of the STO films on MAO are affected by the c-axis (out-of-plane) lengths.展开更多
We propose dynamic terahertz(THz) emission microscopy(DTEM) to visualize temporal–spatial dynamics of photoexcited carriers in electronic materials. DTEM utilizes THz pulses emitted from a sample by probe pulses irra...We propose dynamic terahertz(THz) emission microscopy(DTEM) to visualize temporal–spatial dynamics of photoexcited carriers in electronic materials. DTEM utilizes THz pulses emitted from a sample by probe pulses irradiated after pump pulse irradiation to perform time-resolved two-dimensional mapping of the THz pulse emission, reflecting various carrier dynamics. Using this microscopy, we investigated carrier dynamics in the gap region of low-temperature-grown Ga As and semi-insulating Ga As photoconductive switches of the identical-dipole type. The observed DTEM images are well explained by the change in the electric potential distribution between the electrodes caused by the screening effect of the photoexcited electron-hole pairs.展开更多
We have fabricated low-temperature grown GaAs(LT-GaAs)-based plasmonic photoconductive antennas by RF sputtering of Au nanoparticles and have evaluated their terahertz detection properties.Localized surface plasmon re...We have fabricated low-temperature grown GaAs(LT-GaAs)-based plasmonic photoconductive antennas by RF sputtering of Au nanoparticles and have evaluated their terahertz detection properties.Localized surface plasmon resonance enhances the electric fields near the surface and increases the optical absorption of nanoparticles.The resonance frequency depends on the density of electrons,the effective electron mass,and the size and shape of the nanoparticles.Therefore,we tried to develop a high-sensitivity LT-GaAs photoconductive detector(PCD),which is effective over a wide range of wavelengths,by RF sputtering of Au nano-islands with a variety of aspect ratios from 1.2 to 5.1 on the dipole gap region of the PCD.As a result,we succeeded in increasing the sensitivity by 29%and 40%in the amplitude of observed terahertz pulse for 800 nm and 1560 nm femtosecond laser excitations,respectively.展开更多
文摘SrTiO3 (STO) thin films of different thicknesses were deposited on MgAl2O4 (MAO) substrates to investigate the in-plane strain effect on the soft-mode frequency of the STO films. X-ray reciprocal space mapping (X-RSM) results indicate that there was no relaxation of the in-plane lattice strain of the STO films on MAO. Shifts in the soft-mode frequencies with a decrease in the film thickness were observed using terahertz time-domain spectroscopy (THz-TDS). However, despite the larger lattice mismatch between STO and MAO than that between STO and DyScO3 (DSO), the shifts in the soft-mode frequencies of the STO films on MAO were smaller than those on DSO. The results indicate that the soft-mode frequencies of the STO films on MAO are affected by the c-axis (out-of-plane) lengths.
文摘We propose dynamic terahertz(THz) emission microscopy(DTEM) to visualize temporal–spatial dynamics of photoexcited carriers in electronic materials. DTEM utilizes THz pulses emitted from a sample by probe pulses irradiated after pump pulse irradiation to perform time-resolved two-dimensional mapping of the THz pulse emission, reflecting various carrier dynamics. Using this microscopy, we investigated carrier dynamics in the gap region of low-temperature-grown Ga As and semi-insulating Ga As photoconductive switches of the identical-dipole type. The observed DTEM images are well explained by the change in the electric potential distribution between the electrodes caused by the screening effect of the photoexcited electron-hole pairs.
基金Japan Society for the Promotion of Science(JP17H01269,JP18K18861,P18KK0140)。
文摘We have fabricated low-temperature grown GaAs(LT-GaAs)-based plasmonic photoconductive antennas by RF sputtering of Au nanoparticles and have evaluated their terahertz detection properties.Localized surface plasmon resonance enhances the electric fields near the surface and increases the optical absorption of nanoparticles.The resonance frequency depends on the density of electrons,the effective electron mass,and the size and shape of the nanoparticles.Therefore,we tried to develop a high-sensitivity LT-GaAs photoconductive detector(PCD),which is effective over a wide range of wavelengths,by RF sputtering of Au nano-islands with a variety of aspect ratios from 1.2 to 5.1 on the dipole gap region of the PCD.As a result,we succeeded in increasing the sensitivity by 29%and 40%in the amplitude of observed terahertz pulse for 800 nm and 1560 nm femtosecond laser excitations,respectively.
