Ultra-thin tungsten films were prepared using hotwire assisted atomic layer deposition. The film thickness ranged from 2.5 to 10 nm, as determined by spectroscopic ellipsometry and verified by scanning electron microscopy. The films were implemented in conventional Van der Pauw and circular transmission line method (CTLM) test structures, to explore the effect of film thickness on the sheet and contact resistance, temperature coefficient of resistance (TCR), and external electric field applied. All films exhibited linear current-voltage characteristics. The sheet resistance was shown to considerably vary across the wafer, due to the film thickness non-uniformity. The TCR values changed from positive to negative with decreasing the film thickness. A field-induced modulation of the sheet resistance up to $\sim 4.6\cdot 10^{-4}\,\,\text{V}^{-1}$ was obtained for a 2.5 nm thick film, larger than that generally observed for metals.

中文翻译：

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超薄钨膜中的导电和电场效应

使用热丝辅助原子层沉积制备超薄钨膜。薄膜厚度范围为 2.5 到 10 nm，由光谱椭偏法确定并通过扫描电子显微镜验证。这些薄膜在传统的范德堡和圆形传输线法 (CTLM) 测试结构中实施，以探索薄膜厚度对片材和接触电阻、电阻温度系数 (TCR) 和施加的外部电场的影响。所有薄膜都表现出线性电流-电压特性。由于薄膜厚度的不均匀性，整个晶片的薄层电阻显示出相当大的变化。随着薄膜厚度的减小，TCR 值从正变为负。薄膜电阻的场致调制高达 $\sim 4.6\cdot 10^{-4}\,\,