Controllable Crystallization in Phase-Change Memory for Low-Power Multilevel Storage

We report current-driven crystallization in a TiSi 3 /Ge 2 Sb 2 Te 5 /TiN vertical cell, which can be well controlled and is expected to be applied to multilevel storage with a low threshold voltage of about 1 V. We demonstrate that the number of distinct resistance levels can readily reach 8 and even higher. These levels in this study result from the initial threshold switching and the subsequent current-controlled crystallization induced by Joule heating. The latter allows the creation of many distinct levels, thus enabling the low-cost ultrahigh-density nonvolatile memory.