Phase‐change memory is one of the most promising candidates for the next generation nonvolatile memory, but their high power consumption and low reliability remain bottleneck problems that limit the data storage density and its storage‐class memory application. Here, an innovative phase change material with embedded self‐precipitated interfaces, where the nanoscale grains of phase change material are cut into interconnecting “crystal islands” by thermally stable self‐precipitated material with low thermal conductivity, is proposed. The precipitated material provides both thermal and atomic migration confinements in three dimensions. The thermal confinement enables low power consumption, and the atomic migration confinement enables high device reliability. The devices based on spontaneously phase‐separated O‐doped Sb2Te3 verify the material design, where Sb oxide acts as the precipitated heterogeneous phase and Sb–Te alloy as the phase change material. O‐doped Sb2Te3 device with 250 nm hole diameter shows an ultralow power consumption, down to a few hundreds of femtojoule, which is comparable with those of phase change nanowires. Besides, good thermal stability and low resistivity drift (drift coefficient 0.005) as well as excellent cycle endurance up to 108 times are also obtained at the same time. The doping fabrication process is quite compatible with current semiconductor industry.

Phase-change memory (PCM) is one of the leading candidates for the next generation nonvolatile memory. As a growth-dominated crystalline material, Sb2Te3 is of rapid crystallization speed while its poor thermal stability limits its application. Doping Ti can significantly enhance its amorphous stability but inevitably slows down its crystallization speed. How to balance the contradiction between thermal stability and operation speed remains challenging. In this work, we proposed a gradient Ti-doped Sb2Te3 phase-change material and device. This gradient doping strategy compensates for the negative effect of Ti doping on the crystallization rate of Sb2Te3 via the template effect of the lower doping concentration layer. Very small lattice mismatch between the Sb2Te3 layers with different Ti doping concentrations is verified by x-ray diffraction characterization. The crystallization temperature of a gradient Ti-doped Sb2Te3 thin film is raised up to 172.6 °C and the same 50 ns operation speed as a pure Sb2Te3 device is achieved in the corresponding PCM device. Furthermore, the gradient distribution of Ti elements and the corresponding progressive crystallization phenomenon are verified by transmission electron microscopy revealing the microscopic origin of rapid crystallization speed. Therefore, with our gradient doping strategy, the amorphous stability is improved without sacrificing the crystallization speed in PCM.

The oxygen transport plays an important role on the uniformity of the transition metal oxides (TMOS) memristors. Here, the effect of incorporating Sb2Te3 layer into TiN/HfO2/Pt memristor on oxygen transport has been systematically explored. The experimental results reveal that the memristor with Sb2Te3 incorporation at TiN/HfO2 interface has improved switching uniformity and memory window. Further theoretical calculations demonstrate that Sb2Te3 is a proper oxygen reservoir as oxygen possesses very low formation energy and migration barrier in Sb2Te3 with many vacancies. During the operation process, the Sb2Te3 will gain more oxygen from the HfO2 layer than TiN once the applied voltage reaches up to forming voltage, producing more oxygen vacancies (VOs) in the HfO2 layer, compared with the device without the Sb2Te3 layer. Thus, the VOs conductive filaments (CF) in the HfO2 layer will be thick, resulting in a decrease in the randomness of CF's formation/rupture and, in turn, improving the device uniformity. Our findings provide an in-depth understanding of the oxygen reservoir in TMOS memristors, which is of great significance for the design and development of memristors.

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