To realize ultrafast and energy-efficient electronic devices, reducing the switching voltage slope for ON and OFF states that scales the supply voltage and device dimensions is critical. Novel device architectures based on two-dimensional (2D) materials have overcome the fundamental thermionic limit of the switching slope (60 mV/dec); however, a versatile switching device required for highly integrated memory and neuromorphic applications has not been achieved with such exceptional switching slope characteristics. Here, we demonstrate a switching voltage slope down to 0.62 mV/dec in a threshold switching device based on a vertical heterojunction of silver/hexagonal boron nitride (h-BN)/graphene. The sub-1 mV/dec switching slope for the first time, maintaining a high ON/OFF ratio (up to 10¹⁰), originates from the unique coupling between the migrated silver atoms and the chemically-inert graphene electrode through the 2D insulating h-BN. Moreover, our original switching device enables the evolution from a conventional volatile (threshold switching) to non-volatile memristive state by adequate voltage spikes, which is ideal for selector applications in highly integrated crossbar array architecture and in a novel synaptic device for neuromorphic computing.

为了实现超快和节能的电子设备，降低导通和关断状态的开关电压斜率以缩放电源电压和器件尺寸至关重要。基于二维（2D）材料的新型器件架构克服了开关斜率（60 mV / dec）的基本热电子极限；但是，尚未实现具有如此优异的开关斜率特性的，高度集成的存储器和神经形态应用所需的通用开关设备。在这里，我们展示了基于银/六方氮化硼（h-BN）/石墨烯的垂直异质结的阈值开关器件中的开关电压斜率低至0.62 mV / dec。首次低于1 mV / dec的开关斜率，保持高ON / OFF比率（高达10 ¹⁰）源自迁移的银原子与通过2D绝缘h-BN形成的化学惰性石墨烯电极之间的独特耦合。而且，我们的原始开关设备通过适当的电压尖峰使从传统的易失性（阈值开关）状态转变为非易失性忆阻状态，对于高度集成的交叉开关阵列架构中的选择器应用以及用于神经形态计算的新型突触设备而言，这是理想的选择。