Ha Hoesung, Pyo Juyeong, Lee Yunseok, Kim Sungjun
Division of Electronics and Electrical Engineering, Dongguk University, Seoul 04620, Republic of Korea.
Materials (Basel). 2022 Dec 19;15(24):9087. doi: 10.3390/ma15249087.
In this study, we investigate the synaptic characteristics and the non-volatile memory characteristics of TiN/CeOx/Pt RRAM devices for a neuromorphic system. The thickness and chemical properties of the CeOx are confirmed through TEM, EDS, and XPS analysis. A lot of oxygen vacancies (ions) in CeOx film enhance resistive switching. The stable bipolar resistive switching characteristics, endurance cycling (>100 cycles), and non-volatile properties in the retention test (>10,000 s) are assessed through DC sweep. The filamentary switching model and Schottky emission-based conduction model are presented for TiN/CeOx/Pt RRAM devices in the LRS and HRS. The compliance current (15 mA) and reset stop voltage (−1.3−2.2 V) are used in the set and reset processes, respectively, to implement multi-level cell (MLC) in DC sweep mode. Based on neural activity, a neuromorphic system is performed by electrical stimulation. Accordingly, the pulse responses achieve longer endurance cycling (>10,000 cycles), MLC (potentiation and depression), spike-timing dependent plasticity (STDP), and excitatory postsynaptic current (EPSC) to mimic synapse using TiN/CeOx/Pt RRAM devices.
在本研究中，我们研究了用于神经形态系统的TiN/CeOx/Pt电阻式随机存取存储器（RRAM）器件的突触特性和非易失性存储特性。通过透射电子显微镜（TEM）、能谱仪（EDS）和X射线光电子能谱（XPS）分析确定了CeOx的厚度和化学性质。CeOx薄膜中的大量氧空位（离子）增强了电阻开关特性。通过直流扫描评估了稳定的双极电阻开关特性、耐久性循环（>100次循环）以及保持测试（>10,000秒）中的非易失性特性。针对低电阻状态（LRS）和高电阻状态（HRS）下的TiN/CeOx/Pt RRAM器件，提出了丝状开关模型和基于肖特基发射的传导模型。在设置和重置过程中分别使用合规电流（15 mA）和重置停止电压（-1.3-2.2 V），以在直流扫描模式下实现多级单元（MLC）。基于神经活动，通过电刺激执行神经形态系统。因此，利用TiN/CeOx/Pt RRAM器件，脉冲响应实现了更长的耐久性循环（>10,000次循环）、MLC（增强和抑制）、尖峰时间依赖可塑性（STDP）以及兴奋性突触后电流（EPSC），以模拟突触。
