Threshold switching (TS) and negative differential resistance (NDR) characteristic of niobium oxide (NbO_x) films have been actively studied for neuromorphic computing. Generally, the electroforming process is required for TS and NDR in NbO_x films. However, different electroforming and TS properties have been reported for NbO_x films with different crystallinities or chemical compositions. This study investigates the effect of thermal annealing on the microstructures of NbO_x films and compares the electroforming, TS, and NDR characteristics of amorphous, partially crystallized, and fully crystallized films. The distributions of crystalline NbO₂ phase in NbO_x films annealed at various temperatures were analyzed using transmission electron microscopy dark-field imaging, and it was observed that the distribution of crystalline NbO₂ phase influenced the electroforming process. Moreover, TS characteristics improved in the thermally annealed NbO_x films with crystalline NbO₂ phases.

中文翻译：

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具有结晶 NbO2 相的 NbOx 薄膜的电铸和阈值开关特性

氧化铌 (NbO _x ) 薄膜的阈值开关 (TS) 和负微分电阻 (NDR) 特性已被积极研究用于神经形态计算。通常，NbO _x薄膜中的TS和NDR需要电铸工艺。然而，对于具有不同结晶度或化学成分的NbO _x薄膜，已经报道了不同的​​电铸和 TS 特性。本研究调查了热退火对 NbO _x薄膜微观结构的影响，并比较了非晶、部分结晶和完全结晶薄膜的电铸、TS 和 NDR 特性。结晶NbO ₂相在NbO _{x 中的分布}使用透射电子显微镜暗场成像分析在不同温度下退火的薄膜，观察到结晶NbO ₂相的分布影响电铸过程。此外，在具有结晶 NbO ₂相的热退火 NbO _x膜中，TS 特性得到改善。