2025-11-11 東北大学
図1. a：Co26Mg18F56ナノグラニュラー薄膜の高分解能透過電子顕微鏡像。暗い粒子状の部分がCoナノ粒子で、明るい部分がMgF2マトリックスです。
b：ナノグラニュラー薄膜中での電子のトンネル伝導の模式図。電子は絶縁体をトンネルすることでナノ粒子間を伝導します。
c：ナノグラニュラー薄膜に引張ひずみを加えたときの微細構造変化の模式図。図中のsは粒子間距離、dは粒子径です。s0とd0はひずみが加わっていないときの粒子間距離と粒径です。ナノ粒子（d）は変形せず、ナノ粒子間のマトリックス（s）のみが変形することで、大きな電気抵抗の変化が起きます。
＜関連情報＞
- https://www.tohoku.ac.jp/japanese/2025/11/press20251111-01-nanogranular.html
- https://www.tohoku.ac.jp/japanese/newimg/pressimg/tohokuuniv-press20251111_01web_nanogranular.pdf
- https://www.nature.com/articles/s41598-025-24084-7
大きなゲージ因子を持つ金属-絶縁体ナノグラニュラー膜における高感度機械応答 High-sensitive mechanical response in metal–insulator nanogranular films with large gauge factor
Tomoharu Uchiyama,Cheng Wang,Yui Hasegawa,Nobukiyo Kobayashi,Hiroshi Masumoto,Saburo Takahashi & Sadamichi Maekawa
Scientific Reports Published:10 November 2025
DOI:https://doi.org/10.1038/s41598-025-24084-7
Abstract
Metal strain gauges have been employed for strain and stress measurements for more than 50 years, given their low cost and ease of implementation. However, they face challenges in achieving high sensitivity and miniaturization from the millimeter to the micrometer scale due to their small gauge factor (≃ 2) and low electrical resistivity (≤ 1.1 μΩ∙m). Here, we discovered that metal–insulator nanogranular films can become a novel high-sensitive and micro-scale strain gauge. A Co–(Mg–F) nanogranular film, which comprises metal Co nanogranules and an insulating MgF2 matrix, exhibited a gauge factor 5 times larger and an electrical resistivity 107 times higher than those of practical metal strain gauges. These superior properties originate from the electronic tunneling conduction between the nanogranules, as opposed to the metallic conduction occurring in metal strain gauges. The large gauge factor of nanogranular films is given by the deformation in the intergranular spacing, which causes the modulation of electron tunneling, and thus, the resistivity.
