Structural dependence of terahertz radiation from multiferroicBiFeO3thin films

Abstract

We have investigated the structural dependence of terahertz-radiation emission from the multiferroic BiFeO 3 thin films on ͑LaAlO 3 ͒ 0.3 ͑Sr 2 AlTaO 6 ͒ 0.7 ͑0 0 1͒ substrate. The coherently strained films with thickness ͑t͒ ഛ 75 nm relax partially to bulklike rhombohedral phase at t ജ 110 nm via a coexistence of these two phases in the thickness 80 nmഛ t ഛ 110 nm. The strained films ͑t ഛ 75͒ and the relaxed films ͑t ജ 110 nm͒ exhibit similar terahertz-emission efficiency in the absence of electric-field bias, and this efficiency increases for the intermediate thickness films having coexisting phases. These data combined with the electric-field ͑E͒ dependence of the terahertz-emission amplitude ͑E THz ͒ depict that the terahertz-emission efficiency in zero bias is nearly independent of the lattice, while the ferroelectric properties ͑revealed by E THz -E hysteresis loops͒ are characteristics of both the lattice and the leakage current.

Terahertz wave generation via optical rectification from multiferroic BiFeO3

“…The singledomain nature of these millimeter-sized crystals was confirmed independently by neutron diffraction. 4,5 A different mechanism for terahertz emission from BFO thin films was described by Takahashi et al, 12 Takahashi and Tonouchi, 13 and Rana et al 14 In their work, the emission is due to the injection of photoexcited charge carriers and ultrafast modulation of spontaneous polarization P f . In our measurements, similar processes involving the injection of photocarriers can be ruled out because the energy of our 800 nm pump pulses is lower than the direct optical gap of BFO.…”

“…[8][9][10][11] Recently, it has been proposed that terahertz radiation from BFO thin films can be used in FE domain imaging and optical readout of the state of FE memories. [12][13][14][15] In that work, the terahertz wave was generated by ultrafast modulation of FE polarization when charge carriers were injected in the film by a femtosecond laser pulse.…”

Structural dependent ultrafast electron-phonon coupling in multiferroic BiFeO3 films

“…9 From the applied point of view in photonics, it has been proposed that terahertz radiation from BFO films can be used in ferroelectric domain imaging and optical readout of the state of ferroelectric memories. 10,11 In addition, due to high optical transparency and large third order optical nonlinearities, BFO films are promising for applications in ultrafast photonic devices. 12,13 No matter the structural dependent emission of THz radiation or the nonlinear photonic devices, a detailed understanding of the interaction of electron and lattice over a picosecond time scale is an indispensable issue, 14 which is decisive for determining the functional properties of materials.…”

Strongly enhanced dielectric and energy storage properties in lead-free perovskite titanate thin films by alloying

“…3a). For the mixed BTO-BFO PLD targets, the possible reasons for the double peaks are the coexistence of relaxed and strained phases [61,62], phase separation of the different metal oxides [63][64][65], and twinning [66]. This issue will be discussed later in detail.…”

“…The broader film peaks are not aligned with the SRO/STO peaks along the q x direction indicating the strain relaxation in-plane. The results show that in the BFO, BTO and solid solution films, there is coexistence of both a fully substrate-strained region of the film and a relaxed region [61,62]. The in-plane and out-ofplane lattice parameters of the film determined from measurements of the c parameters from ω-2θ scans (Fig.…”