An isomorphic valency transition in SmTe film enabling nonvolatile resistive change

Abstract A NaCl-type SmTe film showed remarkable electrical contrast (> 105) between as-deposited and annealed films in the absence of a transition in the crystal structure. A rigid-band shift induced by a valency transition between Sm2+ and Sm3+ was found to give rise to significant change in the electronic structure along with a concomitant resistivity change. Moreover, operation of a SmTe-based memory device was demonstrated by a standard measurement scheme with switching driven by electrical pulse-induced Joule heating. Since SmTe remains crystalline in both resistive states, resistance drift is suppressed offering improved readout reliability. Furthermore, the SmTe films were found to exhibit much better data retention, maintaining data for 10 years at 262 °C in contrast to conventional nonvolatile recording material such as Ge-Sb-Te (85-110 °C). The use of a valency transition reveals a new approach to the development of nonvolatile high performance resistive change materials.