Abstract
Anisotropic picosecond photovoltaic responses were observed in lanthanum doped manganiteLaxCa1-xMnO3(x=0.67and 0.4) thin films, which were deposited on miscut LaSrAlO4substrates under ultraviolet pulsed laser irradiation without external bias. The 10%–90% rise time and the full width at half maximum of La0.67Ca0.33MnO3were 470 and 585 ps, respectively, and those of La0.4Ca0.6MnO3were 220 and 515 ps. The photovoltage sensitivities of La0.67Ca0.33MnO3and La0.4Ca0.6MnO3, which are sensitive to the concentrations of lanthanum of the samples, are 0.28 V/mJ and 3.47 V/mJ, respectively. The photosensitivity in the films deposited on MgO is higher than that in those deposited on LaSrAlO4substrates, for it has a big lattice mismatch. These results should open a route for the application of lanthanum doped manganite as an ultrafast photodetector material.
Highlights
The photovoltaic effect was reported in the perovskite-based p-n junctions, thin films, and single crystals [1– 6]
When the LaxCa1−xMnO3 (LCMO) thin film is connected in parallel with a 0.5 Ω resistance, the 10%–90% rise time (RT) and the full width at half maximum (FWHM) decrease to 470 ps and 585 ps for LCMO1, and 220 ps and 515 ps for LCMO2
The microstructure of LCMO/LSAO sample with different lanthanum component was checked with X-ray diffraction (XRD) θ-2θ scan as shown in Figure 1(a), where the [001] axis was aligned carefully and the offset point was set by 10∘ to satisfy Bragg’s diffraction
Summary
The photovoltaic effect was reported in the perovskite-based p-n junctions, thin films, and single crystals [1– 6]. Focus on tilted structures in lanthanide doped perovskite oxides which present ultrafast photoresponses and high sensitivities in photodetection [7–9]. We deposited different concentrations of lanthanum doped manganite thin films, La0.67Ca0.33 MnO3 (LCMO1) and La0.4Ca0.6MnO3 (LCMO2), on miscut LaSrAlO4 (LSAO) substrates, and observed picosecond ultraviolet (UV) photovoltaic effect under pulsed laser irradiations without external bias. The comparative experiments on LCMO film deposited on miscut MgO substrates prove that the photo sensitivity is higher in a big lattice mismatch system. All these experimental results reveal that the lanthanum doped manganite films on miscut substrates can be used as ultrafast photodetective materials
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