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. 2023 Jul 27;22(9):1128–1135. doi: 10.1038/s41563-023-01612-2

Fig. 4. Electrochemical and electronic properties of epitaxial T-Nb2O5 thin films.

Fig. 4

a,b, Galvanostatic discharge–charge curves (a) and specific capacity obtained at each cycle (b) at different current rates for a 40 nm T-Nb2O5/LSAT(110). An irreversible capacity is observed at the slowest current densities, which is attributed to corrosion of parts of the device. c, Cyclic voltammogram recorded at different scan rates. The second cycle of each cycling rate is shown. d,e, Schematics of the ILG device with the Au gate electrode (d) and using the LNbO gate electrode (e). G represents gate electrode. Blue spheres denote Li-ion migrations from gating. f, Temperature-dependent resistivity curves at different gate voltages. g, Vg-dependent resistivity and leakage current curves for several ILs. The sweeping rate was 16 mV s−1. h, Vg-dependent carrier concentration (n), Li composition (x), mobility (μ) and resistivity (ρ) curves from Hall measurements at 200 K for LixNb2O5. The mean and standard deviation are represented with the error bars after three measurements. The resistivity of the pristine film is indicated by the red pentacle. Multistep transitions are shown with increasing Vg, that is, (i) orthorhombic insulator (white regime), (ii) orthorhombic metal (blue), (iii) monoclinic metal (red) and (iv) insulating state (grey). The carrier concentration suddenly increases, and the mobility starts to decrease at ~4 V, indicating carrier scattering at high Li concentrations. The Li concentrations are obtained from Hall measurements, assuming that each Li atom creates one charge carrier. i, Vg-dependent ρ curves for the 16 nm T-Nb2O5/LSAT(110) devices using the LNbO gate electrode (blue and light blue curves) and the Au electrode (the dotted black curve). The sweeping rate was 16 mV s−1. j, Pulse voltage gating of twin T-Nb2O5 devices. The device structure is depicted in e. Pulse voltages of 3 V/−3 V were applied with a pulse with of 50 ms. The channel resistances were measured at 1 µA (Isd). The film thickness and channel size were 30 nm and 60 × 30 µm2, respectively.