Interface-enhanced sensitivity of photoconductivity to the electric current and magnetic field in La0.67Ca0.33MnO3/Nb-SrTiO3 p-n junctions

Abstract

The effects of electric current and magnetic field on the photoconductivity (PC) of La0.67Ca0.33MnO3 (LCMO) films have been investigated within a comparative study on LCMO films on an n-type semiconducting Nb-doped SrTiO3 (NSTO) and insulating SrTiO3 (STO) substrates separately. At room temperature, LCMO on NSTO (LCMO/NSTO) was found to show remarkable PC effect than that on STO (LCMO/STO). More attractive is that, compared with that of LCMO/STO, the room-temperature PC of LCMO/NSTO also shows a high sensitivity to the change of current or magnetic field: for LCMO/NSTO under a light illumination with an intensity of 60 mW/cm2, the increment of current yields a decreases of PC at a rate of 7.6%/μA, while an application of magnetic field of 1.2 T can suppress PC by a percentage as high as ∼20%. In contrast, under the same stimulus of current or field, PC of LCMO/STO remains almost unchanged. The phenomena can be explained based on the interface effects correlated with the photocarrier injection, current shunting, and magnetic tunability occurred at the interface. This work demonstrates that manganite-based heterojunctions with interface engineering are promising for developing a new type of photoelectric device with high sensitivity and multifunctionality.

Study on the Multi-level Resistance-Switching Memory and Memory-State-Dependent Photovoltage in Pt/Nd:SrTiO3 Junctions

“…It is generally known that the photovoltaic (PV) effect is related to the internal electric field [ 22 – 26 ]. So, the PV effect is expected to be dependent on the memory states if the RS is mainly determined by the depletion layer near the metal and n-type STO interface.…”

Off-axis electron holography of manganite-based heterojunctions: Interface potential and charge distribution

“…The bandgap of STON, LMO, and LCMO are 3.2 eV, 1.7 eV, and 1.0 eV, respectively. [23,24] The E F of both STON and LMO are higher than that of LCMO, [21,25] and the E V of LMO is lower than that of LCMO and higher than that of STON. [26] When they contact with each other, electrons will migrate at the interface of LCMO/LMO and LMO/STON, thus producing the band bending at the two interfaces.…”

“…As reported, the bandgap is 3.2 eV for STON and 1.0 eV for LCMO. [23] To obtain a comprehensive understanding of the interface influence on potential and charge distribution, an electron holography study is also performed on the LCMO/STON junction with a 2-nm-thick LMO buffer layer. Figure 6(a) is a hologram taken from the interface region of LCMO/LMO/STON under a positive bias potential of 80 V. To determine the locations of interfaces among LCMO, LMO, and STON, we first mark the interfacial locations in the TEM image of LCMO/LMO/STON heterojunction, and then obtain the hologram image of the heterojunction at the same magnification.…”