Reversible Electrical Resistance Switching in GeSbTe Thin Films: An Electrolytic Approach without Amorphous-Crystalline Phase-Change

Besides the well-known resistance switching originating from the amorphous-crystalline phase-change in GeSbTe thin films, we demonstrate another switching mechanism named ‘polarity-dependent resistance (PDR) switching’. The electrical resistance of the film switches between a low- and high-state when the polarity of the applied electric field is reversed. This switching is not connected to the phase-change, as it only occurs in the crystalline phase of the film, but connected to the solid-state electrolytic behavior i.e. high ionic conductivity of (Sb-rich) GeSbTe under an electric field. I-V characteristics of nonoptimized capacitor-like prototype cells of various dimensions clearly exhibited the switching behavior when sweeping the voltage between +1 V and -1 V (starting point: 0 V). The switching was demonstrated also with voltage pulses of amplitudes down to 1 V and pulse widths down to 1 microsecond for several hundred of cycles with resistance contrasts up to 150 % between the resistance states. Conductive atomic force microscopy (CAFM) was used to examine PDR switching at nanoscales in tip-written crystalline marks, where the switching occurred for less than 1.5 V with more than three orders of resistance contrasts. Our experiments demonstrated a novel and technologically important switching mechanism, which consumes less power than the usual phase-change switching and provide opportunity to bring together the two resistance switching types (phase-change and PDR) in a single system to extend the applicability of GeSbTe materials.