Electrostatic modulation of the electronic properties of Nb-doped SrTiO3 superconducting films

Abstract

We have performed ferroelectric field effect experiments using an epitaxial heterostructure composed of ferroelectric $\mathrm{Pb}({\mathrm{Zr}}_{\text{0.2}}{\mathrm{Ti}}_{\text{0.8}}){\mathrm{O}}_3$ and superconducting Nb-doped ${\mathrm{SrTiO}}_3.$ The films were prepared on (001) ${\mathrm{SrTiO}}_3$ substrates by off-axis radio-frequency magnetron sputtering and pulsed-laser deposition. By switching the polarization field of the 500-Å-thick $\mathrm{Pb}({\mathrm{Zr}}_{\text{0.2}}{\mathrm{Ti}}_{\text{0.8}}){\mathrm{O}}_3$ layer, a large change of about 30% in resistivity and a 20% shift of $T_c$ ${\mathrm{(\Delta T}}_c\text{∼0.05\hspace{0.17em}}\mathrm{K})$ were induced in the 400-Å-thick epitaxial Nb-doped ${\mathrm{SrTiO}}_3$ layer. The relationship between $T_c$ and the electrostatically modulated average carrier concentration can be mapped onto the phase diagram of chemically doped ${\mathrm{SrTiO}}_3.$