Fig. 5: Electrical behavior of two-terminal devices based on nonstoichiometric 2D materials.

a Digit photo images and an optical image of a two-terminal nanogenerator based on a nonstoichiometric 2D Cr_1+σSe₂ nanoflake. b Output voltage and short circuit current of a 2D Cr_1+σSe₂ nanoflake under one release-stretch-release cycle. c–d Output voltage and short circuit current as a function of time under several cycles of tensile strain. e Electrical transport behaviors of the nonstoichiometric 2D Fe_1+αTe₂ nanoflakes along OOP direction. The inset illustrates the principal scheme of conductive force microscopy (CFM) using a conductive tip and Au layer as top and bottom electrodes, respectively. The lines with colors changed from deep blue to light blue represent the fitted curves tested at the voltages ranged from 10 V, 7.5 V to 5.5 V, respectively. f I-V curves of a two-terminal nonstoichiometric 2D Fe_1+αTe₂ nanoflake device with different maximum sweeping voltages. The red to light red lines indicate the I-V curves tested at the voltage of 4 V, 3 V, 2 V and 1 V, respectively. g I-V curves of a two-terminal nonstoichiometric 2D Fe_1+αTe₂ nanoflake device with 109 cycle sweeping. The sweeping voltage is set in a range of ‒4 to 4 V. h Drain currents retention curves read at drain voltages of 10 V (khaki line) and 0.5 V (red line) in the up panel and read at 2 V after 10 V (dark khaki line) and ‒10 V (orange line) bias poling (below panel). i I-V curves after 7 times accumulation indicated by lines with colors evolved from dark blue to light blue. The inset shows the enlarged grey dotted frame of the curves in logarithmic coordinates. Drain voltage sweeps from 0 V to 10 V in each cycle. j Currents (blue dots and line) and open circuit voltages (red squares and line) evolution in the 7 cycles sweeping.