Energy band diagrams are widely utilized to explain the switching mechanism of resistance random access memory (RRAM). However, a precise and quantitative band theory is still lacking in this field. Although HfS2 has good applications in many fields because of its good electrical and optical properties, its applications in RRAM have seldom been reported. In this work, the exfoliated nanosheets of HfS2 were utilized to fabricate memory devices with a structure of Pt/Al/HfS2/p+-Si, which show typical bipolar resistive switching behavior with high switching voltage and a small ratio of high and low resistive states (R-ratio). According to the density functional theory (DFT) calculation results of energy band diagrams, instead of conductive filament formation in other resistive switching materials, the doping of sulfur vacancy (VS) of 3.8% is already enough to change the whole HfS2 layer from the semiconductor to the metal. The transition is caused by the change in the VS doping concentration from low to high, which is the result of the generation and movement of VS under an electric field. The DFT also calculated that HfS2 devices utilizing Indium Tin Oxide as the bottom electrode can show bipolar resistive switching behavior with lower switching voltage and a higher R-ratio than those utilizing p+-Si, which is confirmed by the experimental results. The DFT calculation can be utilized for both explaining the switching mechanism and designing the device structure to optimize the switching characteristics.Energy band diagrams are widely utilized to explain the switching mechanism of resistance random access memory (RRAM). However, a precise and quantitative band theory is still lacking in this field. Although HfS2 has good applications in many fields because of its good electrical and optical properties, its applications in RRAM have seldom been reported. In this work, the exfoliated nanosheets of HfS2 were utilized to fabricate memory devices with a structure of Pt/Al/HfS2/p+-Si, which show typical bipolar resistive switching behavior with high switching voltage and a small ratio of high and low resistive states (R-ratio). According to the density functional theory (DFT) calculation results of energy band diagrams, instead of conductive filament formation in other resistive switching materials, the doping of sulfur vacancy (VS) of 3.8% is already enough to change the whole HfS2 layer from the semiconductor to the metal. The transition is caused by the change in the VS doping concentration from low to high...

中文翻译：

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通过实验和密度泛函理论计算研究 HfS2 薄膜存储器件的电阻转换行为和机制

能带图被广泛用于解释电阻随机存取存储器 (RRAM) 的开关机制。然而，该领域仍然缺乏精确和定量的能带理论。虽然 HfS2 由于其良好的电学和光学特性在许多领域都有很好的应用，但其在 RRAM 中的应用却鲜有报道。在这项工作中，剥离的 HfS2 纳米片被用来制造具有 Pt/Al/HfS2/p+-Si 结构的存储器件，其表现出典型的双极电阻开关行为，具有高开关电压和小高低阻态比率（R 比）。根据能带图的密度泛函理论（DFT）计算结果，代替其他电阻开关材料中的导电丝形成，硫空位（VS）的掺杂为3。8% 已经足以将整个 HfS2 层从半导体转变为金属。这种转变是由VS掺杂浓度由低到高的变化引起的，这是VS在电场作用下产生和移动的结果。DFT 还计算出，使用氧化铟锡作为底部电极的 HfS2 器件可以表现出双极电阻开关行为，与使用 p+-Si 的器件相比，具有更低的开关电压和更高的 R 比，实验结果证实了这一点。DFT计算既可用于解释开关机制，也可用于设计器件结构以优化开关特性。能带图被广泛用于解释电阻随机存取存储器（RRAM）的开关机制。然而，该领域仍缺乏精确和定量的能带理论。虽然 HfS2 由于其良好的电学和光学特性在许多领域都有很好的应用，但其在 RRAM 中的应用却鲜有报道。在这项工作中，剥离的 HfS2 纳米片被用来制造具有 Pt/Al/HfS2/p+-Si 结构的存储器件，其表现出典型的双极电阻开关行为，具有高开关电压和小高低阻态比率（R 比）。根据能带图的密度泛函理论（DFT）计算结果，与其他电阻开关材料中形成导电细丝不同，3.8%的硫空位（VS）掺杂已经足以从半导体改变整个HfS2层到金属。