Photoelectronic behaviors of bilayer ultrathin films manganite-based heterojunctions

We presented a systematic study on the photoelectronic properties of the La_0.67Ba_0.33MnO₃ (20 nm)/LaMnO ₃(t)/SrTiO₃:0.05 wt. Nb (LBMO/LMO(t)/STON) junctions with 0 t 30 nm. The short-circuit photocurrent (I_ph) is found to show a complex dependence on the LMO buffer layer. It undergoes first a sharp drop as the layer thickness of LMO increases from 0 to 3 nm and then, after a rigid turn, a slow decrease for further increase in layer thickness. These results indicate that the coupling between LBMO and STON can be effectively depressed by a LMO layer of 3 nm. The photocurrent is further found to be temperature dependent, increasing monotonically upon cooling, and the maximal growth, occurring in the junction of t 3 nm, can be as high as 226 when cooled from 320 K to 40 K. Meanwhile, the I_ph-t dependences at different temperatures are similar, which is an indication of temperature independence for the diffusion length of the photocarriers. Analysis of the capacitance-voltage relations indicates that the change of interfacial barrier is the reason for the peculiar photoelectronic behavior observed.