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Towards an optimal contact metal for CNTFETs

Reference

Artem Fediai, Dmitry A. Ryndyk, Gotthard Seifert, Sven Mothes, Martin Claus, Michael Schroter, Gianaurelio Cuniberti, "Towards an optimal contact metal for CNTFETs" , In Nanoscale, The Royal Society of Chemistry, vol. 8, pp. 10240-10251, 2016. [doi]

Abstract

Downscaling of the contact length Lc of a side-contacted carbon nanotube field-effect transistor (CNTFET) is challenging because of the rapidly increasing contact resistance as Lc falls below 20-50 nm. If in agreement with existing experimental results, theoretical work might answer the question, which metals yield the lowest CNT-metal contact resistance and what physical mechanisms govern the geometry dependence of the contact resistance. However, at the scale of 10 nm, parameter-free models of electron transport become computationally prohibitively expensive. In our work we used a dedicated combination of the Green function formalism and density functional theory to perform an overall ab initio simulation of extended CNT-metal contacts of an arbitrary length (including infinite), a previously not achievable level of simulations. We provide a systematic and comprehensive discussion of metal-CNT contact properties as a function of the metal type and the contact length. We have found and been able to explain very uncommon relations between chemical, physical and electrical properties observed in CNT-metal contacts. The calculated electrical characteristics are in reasonable quantitative agreement and exhibit similar trends as the latest experimental data in terms of: (i) contact resistance for Lc = [infinity], (ii) scaling of contact resistance Rc(Lc); (iii) metal-defined polarity of a CNTFET. Our results can guide technology development and contact material selection for downscaling the length of side-contacts below 10 nm.

Bibtex

@Article{C6NR01012A,
author ="Fediai, Artem and Ryndyk, Dmitry A. and Seifert, Gotthard and Mothes, Sven and Claus, Martin and Schroter, Michael and Cuniberti, Gianaurelio",
title ="Towards an optimal contact metal for CNTFETs",
journal ="Nanoscale",
year ="2016",
volume ="8",
issue ="19",
pages ="10240-10251",
publisher ="The Royal Society of Chemistry",
doi ="10.1039/C6NR01012A",
url ="http://dx.doi.org/10.1039/C6NR01012A",
abstract ="Downscaling of the contact length Lc of a side-contacted carbon nanotube field-effect transistor (CNTFET) is challenging because of the rapidly increasing contact resistance as Lc falls below 20-50 nm. If in agreement with existing experimental results{,} theoretical work might answer the question{,} which metals yield the lowest CNT-metal contact resistance and what physical mechanisms govern the geometry dependence of the contact resistance. However{,} at the scale of 10 nm{,} parameter-free models of electron transport become computationally prohibitively expensive. In our work we used a dedicated combination of the Green function formalism and density functional theory to perform an overall ab initio simulation of extended CNT-metal contacts of an arbitrary length (including infinite){,} a previously not achievable level of simulations. We provide a systematic and comprehensive discussion of metal-CNT contact properties as a function of the metal type and the contact length. We have found and been able to explain very uncommon relations between chemical{,} physical and electrical properties observed in CNT-metal contacts. The calculated electrical characteristics are in reasonable quantitative agreement and exhibit similar trends as the latest experimental data in terms of: (i) contact resistance for Lc = [infinity]{,} (ii) scaling of contact resistance Rc(Lc); (iii) metal-defined polarity of a CNTFET. Our results can guide technology development and contact material selection for downscaling the length of side-contacts below 10 nm."}

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