Enhancing the Resistive Memory Window through Band Gap Tuning in Solid Solution (Cr_1–xV_x)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 0.95 Cr 0.05 ) 2 O 3, exhibiting a tight memory window. In the present study, V-substituted Cr 2 O 3 compounds (Cr 1– x V x ) 2 O 3 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 Cr 2 O 3 compounds decreases from 3 eV for Cr 2 O 3 to 0 eV for V 2 O 3 . 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 0.30 V 0.70 ) 2 O 3 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 0.05 V 0.95 ) 2 O 3 . 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– x V x ) 2 O 3 solid solution. It thus confirms the potential of correlated insulators for memory applications.