Department of Materials Science and Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
Department of Electrical and Computer Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
ACS Appl Mater Interfaces. 2016 Aug 10;8(31):20176-84. doi: 10.1021/acsami.6b05034. Epub 2016 Jul 26.
We present data on the filament size and temperature distribution in Hf0.82Al0.18Ox-based Resistive Random Access Memory (RRAM) devices obtained by transient thermometry and high-resolution transmission electron microscopy (HRTEM). The thermometry shows that the temperature of the nonvolatile conducting filament can reach temperatures as high as 1600 K at the onset of RESET at voltage of 0.8 V and power of 40 μW. The size of the filament was estimated at about 1 nm in diameter. Hot filament increases the temperature of the surrounding high resistivity oxide, causing it to conduct and carry a significant fraction of the total current. The current spreading results in slowing down the filament temperature increase at higher power. The results of thermometry have been corroborated by HRTEM analysis of the as-fabricated and switched RRAM devices. The functional HfAlOx layer in as-fabricated devices is amorphous. In devices that were switched, we detected a small crystalline region of 10-15 nm in size. The crystallization temperature of the HfAlOx was determined to be 850 K in an independent annealing experiment. The size of the crystalline region agrees with thermal modeling based on the thermometry data. Scanning transmission electron microscopy (TEM) coordinated with electron energy loss spectroscopy could not detect changes in the chemical makeup of the filament.
我们展示了通过瞬态热测量和高分辨率透射电子显微镜（HRTEM）获得的基于 Hf0.82Al0.18Ox 的阻变随机存取存储器（RRAM）器件中细丝尺寸和温度分布的数据。热测量表明，在 0.8 V 电压和 40 μW 功率的 RESET 起始时，非易失性导电细丝的温度可高达 1600 K。细丝的尺寸估计约为 1 nm 直径。热丝会增加周围高电阻率氧化物的温度，使其导电并承载总电流的很大一部分。在更高功率下，电流扩展会导致细丝温度升高速度减慢。热测量的结果得到了制造和开关 RRAM 器件的 HRTEM 分析的证实。在制造的器件中，功能 HfAlOx 层是非晶的。在已切换的器件中，我们检测到一个 10-15 nm 大小的小结晶区。在独立的退火实验中，确定 HfAlOx 的结晶温度为 850 K。结晶区的大小与基于热测量数据的热模拟一致。扫描透射电子显微镜（TEM）与电子能量损失光谱的协调无法检测到细丝化学成分的变化。
