Improving the performance of phase-change memory by grain refinement

Many experiments have shown that three-dimensional-confined grain refinement (GR) textures in phase-change memory reduce power consumption and improve endurance performance. However, a lack of knowledge on the GR mechanisms and their influence on device performances challenges designs that concurrently enhance the comprehensive device performances using the same impurity-doped strategy. Here, we experimentally observe dramatic GR in carbon-doped Ge2Sb2Te5 (GST), which also presents reduced power consumption and enhanced endurance performances. We provide low power consumption evidence that thermal conductivity controls the thermal transport heat loss and is proportional to the size of nanoscale grains because the boundary severely scatters phonons. Our simulations indicate that the short carbon chains in the boundary interlace with each other and trend to form trialkyl carbon atoms that constitute the basic local environment of graphene. The stable sheet consists of aggregated carbon, which is even stable above the melting temperature of GST and acts as a second-phase drag to refine the grain size. The enhanced endurance is explained by the restricted migration from the stable carbon sheet, which is verified by the greatly reduced diffusion coefficient of the host atoms in the boundary because of the less shielding effect from the core electrons in carbon and strong bonds formed between host and carbon atoms. Our findings show that the reduced power consumption and enhanced endurance from GR engineering are feasible in phase-change memory, which has been largely overlooked.