Direct observation of nanometer-scale Joule and Peltier effects in phase change memory devices

摘要

We measure power dissipation in phase change memory (PCM) devices by scanning Joule expansion microscopy (SJEM) with ～50nm spatial and 0.2 K temperature resolution. The temperature rise in the Ge_2Sb_2Te_5 (GST) is dominated by Joule heating, but at the GST-TiW contacts it is a combination of Peltier and current crowding effects. Comparison of SJEM and electrical measurements with simulations of the PCM devices uncovers a thermopower of ～350μVK~(-1) and a contact resistance of ～2.0 ×10~(8)Ω m~2 (to TiW) for 25 nm thick films of face centered-cubic crystalline GST. Knowledge of such nanometer-scale Joule, Peltier, and current crowding effects is essential for energy-efficient design of future PCM technology.