Double-layer fabrication of cubic-manganites/hexagonal-ZnO on various substrates by ion beam sputtering, and variable electrical property

Abstract

Hetero double-layers of LaBaMnO 3 (LBMO)/ZnO were fabricated by ion beam sputtering on substrates of MgO, sapphire (SP), LaAlO 3 (LAO), and SrTiO 3 (STO). All the surfaces of substrates, ZnO and LBMO have step-terrace morphology. The p-LBMO/n-ZnO/SP shows junction rectification at different temperatures. The junction resistance follows from colossal magnetoresistance (CMR) of LBMO based on DEC model. The different LBMO/ZnO junctions on the different substrates show different junction behaviors at room temperatures. LBMO/ZnO/STO has the largest rectification factor of 210. After running measurement currents, LBMO/ZnO/STO shows current-voltage (I-V) switchings. LBMO/ZnO/MgO shows very clear switching and large hysteresis between upward and downward voltage sweeps. These are interpreted by CMR and DEC model, and phase separation. The switching is caused by disconnection of percolation path consisting of ferromagnetic metallic grains. The higher resistant state cannot be quickly transformed back to the lower resistant state during the downward sweep.

ESR Study of (La,Ba)MnO3/ZnO Nanostructure for Resistive Switching Device

“…The reduced Curie temperature in the LBMO/ZnO nanostructure may be caused by relatively strong lattice mismatch between LBMO and ZnO [22]. …”

“…In addition, it shows a very low resistance near zero Volts in the reverse side. Thus, the sample shows the transition from the very low resistant state, to the intermediate resistant state, and finally to the high resistant state with increasing the reverse voltage [ 22 ]. Further, after running the second measurement cycle, the I – V dependence shows a kink near 4 V in the forward (disappearance of one-step switching) and the one-step switching in the reverse bias (disappearance of two-step switching).…”

“…[22]. The deposition was performed with ultralow deposition rate (near 10 −3  nm/s) in two stages: at first, ZnO underlayer was grown on SrTiO 3 (001) substrate at 400 °C, and then secondary LBMO overlayer was deposited on the ZnO underlayer at 600 °C.…”

“…The LBMO/ZnO nanostructure was fabricated on SrTiO 3 (001) substrate by ion-beam sputtering from (La,Ba)MnO 3 and ZnO targets, as described in Ref. [ 22 ]. The deposition was performed with ultralow deposition rate (near 10 −3 nm/s) in two stages: at first, ZnO underlayer was grown on SrTiO 3 (001) substrate at 400 °C, and then secondary LBMO overlayer was deposited on the ZnO underlayer at 600 °C.…”

“…Okada et al [ 22 ] fabricated and investigated ZnO/substituted manganite bilayers on different substrates. They reported rectification properties and resistive switching over a wide temperature range.…”