缺硒范德华HfSe2-x中的电输运交叉与大磁电阻
Electrical transport crossover and large magnetoresistance in selenium deficient van der Waals HfSe2-x
AI总结：
本研究系统研究了化学计量比与缺硒HfSe2的输运性质，发现缺硒导致从半导体到金属的转变及大磁电阻，表明缺陷工程可有效调控二维材料电子结构。
摘要：
过渡金属二硫属化物在过去十年中受到了广泛关注，不仅因为其新的基础物理，还因为在这些材料中涌现的应用。目前，人们普遍认为TMDs中的硫属元素缺失要么发生在高温生长过程中，要么发生在纳米加工过程中，从而导致文献中报道的其物理性质发生显著变化。在这里，我们进行了一项系统性研究，涉及原始化学计量比的HfSe2、缺硒的HfSe1.9和HfSe1.8。化学计量比的HfSe2输运结果显示半导体行为，带隙为1.1 eV。在室温下高真空退火HfSe2导致Se损失，形成HfSe1.9，其在低于50 K的低温下表现出非常规的大磁电阻率，遵循扩展的Kohler规则。此外，在HfSe1.9单晶中观察到清晰的电阻率交叉，模拟金属-绝缘体转变。进一步增加HfSe1.8中的缺硒程度，导致在所有温度下直至2 K都呈现完全的金属电输运。化学计量比和缺硒HfSe2输运行为的这种显著差异进一步强调，缺陷控制和工程可能是一种有效的方法，可用于调控二维材料的电子结构，可能解锁新的物质状态，甚至发现新材料。
英文摘要：
Transition metal dichalcogenides have received much attention in the past decade not only due to the new fundamental physics, but also due to the emergent applications in these materials. Currently chalcogenide deficiencies in TMDs are commonly believed either during the high temperature growth procedure or in the nanofabrication process resulting significant changes of their reported physical properties in the literature. Here we perform a systematic study involving pristine stochiometric HfSe2, Se deficient HfSe1.9 and HfSe1.8. Stochiometric HfSe2 transport results show semiconducting behavior with a gap of 1.1eV. Annealing HfSe2 under high vacuum at room temperature causes the Se loss resulting in HfSe1.9, which shows unconventionally large magnetoresistivity following the extended Kohler's rule at low temperatures below 50 K. Moreover, a clear electrical resistivity crossover, mimicking the metal-insulator transition, is observed in the HfSe1.9 single crystal. Further increasing the degree of deficiency in HfSe1.8 results in complete metallic electrical transport at all temperatures down to 2K. Such a drastic difference in the transport behaviors of stoichiometric and Se-deficient HfSe2 further emphasizes that defect control and engineering could be an effective method that could be used to tailor the electronic structure of 2D materials, potentially unlock new states of matter, or even discover new materials.
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