Seki Kazuhiko, Kubo Toshitaka, Ye Nan, Shimizu Tetsuo
National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, Higashi 1-1-1, Tsukuba, Ibaraki, 305-8565, Japan.
Yazaki Corporation 1500 Mishuku, Susono-city, Shizuoka, 410-1194, Japan.
Sci Rep. 2020 Jun 30;10(1):10633. doi: 10.1038/s41598-020-66739-7.
Recently, highly anisotropic conductors, such as multilayer graphene, have been attracting much attention. The local resistivity can be determined by measuring the contact resistance; however, the theoretical expressions of contact resistance have been developed for isotropic slabs but have not been well developed for highly anisotropic film conductors. We obtain theoretical expressions of the spreading resistance below the circular contact for a highly anisotropic film on a bulk slab. The film spreading resistance of isotropic conductors deviates from the bulk spreading resistance when the film thickness is smaller than the contact radius. Nevertheless, the spreading resistance of anisotropic conducting films can be approximated by that of the bulk slabs even when the film thickness is smaller than the contact radius if the in-plane electrical conductivity is larger than the out-of-plane electrical conductivity. Owing to the high in-plane conductivity, the spreading resistance of anisotropic bulk conductors can be lowered from that predicted by the Holm's equation obtained using the out-of-plane conductivity and the contact radius. We show that these characteristics are beneficial to use the highly anisotropic film as a cover layer when the in-plane conductivity of the film is high and the conductivity of the base slab is low.
最近，诸如多层石墨烯之类的高度各向异性导体备受关注。局部电阻率可通过测量接触电阻来确定；然而，接触电阻的理论表达式是针对各向同性平板推导出来的，对于高度各向异性的薄膜导体尚未得到充分发展。我们得出了在块状平板上的高度各向异性薄膜圆形接触下方扩展电阻的理论表达式。当薄膜厚度小于接触半径时，各向同性导体的薄膜扩展电阻偏离块状扩展电阻。然而，如果面内电导率大于面外电导率，即使薄膜厚度小于接触半径，各向异性导电薄膜的扩展电阻也可近似为块状平板的扩展电阻。由于高面内电导率，各向异性块状导体的扩展电阻可低于使用面外电导率和接触半径通过霍尔姆方程预测的值。我们表明，当薄膜的面内电导率高而基片的电导率低时，这些特性有利于将高度各向异性薄膜用作覆盖层。
