Influence of nuclear quantum effects on the mobility gap of amorphous carbon

Amorphous carbon (a-C) films are interesting for a variety of applications, for example as components of thin-film transistors, solar cells, and microelectromechanical devices. Recently we investigated the electronic properties of diamond-like a-C and we showed that quantum vibronic coupling is critical in determining its mobility gap, and hence the concentration of charge carriers, while it has a moderate influence on the structural properties of the film [1]. Here we couple stochastic methods with first principle electronic structure calculations, using the PyEPFD (https://pyepfd.readthedocs.io/) package and the Qbox (http://qboxcode.org/) code. We study the mobility gap of a-C films as a function of mass density and dopants, with the goals of optimizing the performance of electronic devices based on amorphous carbon. We also discuss the efficacy of stochastic methods compared to FPMD coupled to path integral simulations and quantum thermostats [2], implemented through the coupling of and i-PI (http://ipi-code.org/) and Qbox.

[1] A. Kundu et al, PNAS 2022; [2] A. Kundu et al, J. Chem. Theory Comput. 2023, J. Phys. Chem. Lett. 2024.