Contacts for organic switches with carbon-nanotube leads

TL;DR

This study investigates how different atomic contacts between organic molecular switches and carbon nanotube leads influence their electronic switching behavior, revealing that contact choice significantly affects device performance and switching bias.

Contribution

It introduces a first-principles simulation approach to identify atomic contacts that optimize switching properties in organic molecular devices with carbon nanotube leads.

Findings

Certain contacts enhance the distinction between tautomeric states.

Peroxide contacts or direct connections outperform sulfur contacts in some regimes.

Switching bias depends strongly on contact type, not just the molecule itself.

Abstract

Molecular devices, as future electronics, seek low-resistivity contacts for the energy saving. At the same time, the contacts should intensify desired properties of tailored electronic elements. In this work, we focus our attention on two classes of organic switches connected to carbon-nanotube leads and operating due to photo- or field-induced proton transfer (PT) process. By means of the first-principles atomistic simulations of the ballistic conductance, we search for atomic contacts which strengthen diversity of the two swapped I-V characteristics between two tautomers of a given molecular system. We emphasize, that the low-resistive character of the contacts is not necessarily in accordance with the switching properties. Very often, the higher-current flow makes it more difficult to distinguish between the logic states of the molecular device. Instead, the resistive contacts multiply a current gear at the tautomeric transition to a larger extent. The low- and high-bias work regimes set additional conditions, which are fulfilled by different contacts. In some cases, the peroxide contacts or the direct connection to the tube perform better than the popular sulfur contact. Additionally, we find that the switching-bias value is not an inherent property of the conducting molecule, but it strongly depends on the chosen contacts.