High Magnetic Field Laboratory, Chinese Academy of Sciences , Hefei, Anhui 230031, PR China.
J Am Chem Soc. 2015 Dec 2;137(47):15043-8. doi: 10.1021/jacs.5b10212. Epub 2015 Nov 17.
Fabricating a flexible room-temperature ferromagnetic resistive-switching random access memory (RRAM) device is of fundamental importance to integrate nonvolatile memory and spintronics both in theory and practice for modern information technology and has the potential to bring about revolutionary new foldable information-storage devices. Here, we show that a relatively low operating voltage (+1.4 V/-1.5 V, the corresponding electric field is around 20,000 V/cm) drives the dual vacancies evolution in ultrathin SnO2 nanosheets at room temperature, which causes the reversible transition between semiconductor and half-metal, accompanyied by an abrupt conductivity change up to 10(3) times, exhibiting room-temperature ferromagnetism in two resistance states. Positron annihilation spectroscopy and electron spin resonance results show that the Sn/O dual vacancies in the ultrathin SnO2 nanosheets evolve to isolated Sn vacancy under electric field, accounting for the switching behavior of SnO2 ultrathin nanosheets; on the other hand, the different defect types correspond to different conduction natures, realizing the transition between semiconductor and half-metal. Our result represents a crucial step to create new a information-storage device realizing the reversible transition between semiconductor and half-metal with flexibility and room-temperature ferromagnetism at low energy consumption. The as-obtained half-metal in the low-resistance state broadens the application of the device in spintronics and the semiconductor to half-metal transition on the basis of defects evolution and also opens up a new avenue for exploring random access memory mechanisms and finding new half-metals for spintronics.
制造柔性室温铁磁阻变随机存储器（RRAM）器件对于将非易失性存储器和自旋电子学集成到现代信息技术中具有重要的理论和实践意义，并且有可能带来革命性的新型可折叠信息存储设备。在这里，我们展示了相对较低的工作电压（+1.4 V/-1.5 V，相应的电场约为 20,000 V/cm）可以在室温下驱动超薄 SnO2 纳米片中的双空位演变，这导致半导体和半金属之间的可逆转变，伴随着高达 10（3）倍的导电性急剧变化，在两个电阻状态下表现出室温铁磁性。正电子湮没谱和电子自旋共振结果表明，超薄 SnO2 纳米片中的 Sn/O 双空位在电场下演化成孤立的 Sn 空位，这解释了 SnO2 超薄纳米片的开关行为；另一方面，不同的缺陷类型对应于不同的传导性质，实现了半导体和半金属之间的转变。我们的结果代表了朝着创建新的信息存储设备迈出的关键一步，该设备可以在低能耗下实现半导体和半金属之间的可逆转变，同时具有柔韧性和室温铁磁性。在低电阻状态下获得的半金属拓宽了基于缺陷演变的器件在自旋电子学和半导体到半金属转变中的应用，也为探索随机存取存储器机制和寻找用于自旋电子学的新半金属开辟了新途径。
