Quantized Conduction Device with 6-Bit Storage Based on Electrically Controllable Break Junctions

Abstract

Atomic-level control of conductance in a Cu/Ti/HfO2/TiN-based electrically controllable break junction (ECBJ) is demonstrated. The ECBJ is designed through sophisticated stack engineering and refined electrical operation. Control over bias-induced ion migration is the key to forming the ECBJ. Precise atomic-level control is accomplished with an optimized high temperature forming (OHTF) scheme. OHTF-controlled single-atomic switching in ECBJs has not yet been studied in detail. During OHTF, higher ion migration, higher defect generation speed, and lower barrier height reduce the forming voltage to half of its room temperature level. OHTF significantly improves switching uniformity and step-wise control of conductance. For OHTF devices, intrinsic single atomic movement, i.e., single-atomic switching, is controlled for >2 x 10(3) DC cycles, with an extrinsic voltage of +/- 650 mV to make or break the atomic junction, hence the name ECBJ. In such thermally guided devices, meticulous control over quantum levels manifests a 6 bit per cell storage capability. Finally, the applicability of Cu/Ti/HfO2/TiN based ECBJs to the realization of forming free, low power (a few hundred of femto-watts), sub-atomic switching is suggested.