Nanoscale Bipolar Electrical Switching of Ge2Sb2Te5 Phase‐Change Material Thin Films

Abstract

AbstractChalcogenide phase‐change materials (PCMs) exhibit distinct rapid changes in electrical properties upon repeatable switching between amorphous and crystalline structure and are thus attractive for emerging nonvolatile memory (phase‐change random access memory, PCRAM) applications. However, one of the key limitations of PCRAM concepts is their power consumption due to high RESET current requirement. In this work, the electrical memory switching behavior of Ge2Sb2Te5 phase‐change thin films is investigated in detail. Bipolar electrical switching of PCMs at the nanoscale is demonstrated by use of conductive atomic force microscopy and visualized by simultaneously recording topography and electric current maps. The memory cell exhibits excellent scalability (≈15 nm lateral size), low RESET/SET operation voltages (0.5 V), and high on/off resistance ratios (≈5 × 103) with a data storage density higher than 0.7 Tbit in.−2. The physical switching mechanism of the memory is explored by investigation of the local conduction channel, evaluating the local microstructure and local chemical composition by advanced electron microscopy. The switching process is interpreted as a combination of both phase‐change and electrolytic mechanisms.