Enhancing the Resistive Memory Window through Band Gap Tuning in Solid Solution (Cr_1-V)₂O₃

Memories based on the insulator-to-metal transition in correlated insulators are promising to overcome the limitations of alternative nonvolatile memory technologies. However, associated performances have been demonstrated so far only on narrow-gap compounds, such as (V_0.95Cr_0.05)₂O₃, exhibiting a tight memory window. In the present study, V-substituted Cr₂O₃ compounds (Cr_1-V)₂O₃ have been synthesized and widely investigated in thin films, single crystals, and polycrystalline powders, for the whole range of chemical composition (0 < x < 1). Physicochemical, structural, and optical properties of the annealed magnetron-sputtered thin films are in very good agreement with those of polycrystalline powders. Indeed, all compounds exhibit the same crystalline structure with a cell parameter evolution consistent with a solid solution over the whole range of x values, as demonstrated by X-ray diffraction and Raman scattering. Moreover, the optical band gap of V-substituted Cr₂O₃ compounds decreases from 3 eV for Cr₂O₃ to 0 eV for V₂O₃. In the same way, resistivity is decreased by almost 5 orders of magnitude as the V content x is varying from 0 to 1, similarly in thin films and single crystals. Finally, a reversible resistive switching has been observed for thin films of three selected V contents (x = 0.30, 0.70, and 0.95). Resistive switching performed on MIM devices based on a 50 nm thick (Cr_0.30V_0.70)₂O₃ thin film shows a high endurance of 1000 resistive switching cycles and a memory window R_OFF/R_ON higher by 3 orders of magnitude, as compared to (Cr_0.05V_0.95)₂O₃. This comprehensive study demonstrates that a large range of memory windows can be reached by tuning the band gap while varying the V content in the (Cr_1-V)₂O₃ solid solution. It thus confirms the potential of correlated insulators for memory applications.