Photoemission study of poly(dA)-poly(dT) DNA : Experimental and theoretical approach to the electronic density of states

TL;DR

This study combines experimental ultraviolet photoemission spectroscopy with theoretical density-functional theory calculations to analyze the electronic density of states in poly(dA)-poly(dT) DNA molecules, revealing substrate effects and energy level shifts.

Contribution

It provides a combined experimental and theoretical analysis of DNA's electronic states, showing good agreement and substrate influence on energy levels.

Findings

Fermi level is in the middle of DNA's band gap

Thick DNA films exhibit a 2 eV energy shift

Experimental and theoretical results are in good agreement

Abstract

We present results of an ultraviolet photoemission spectroscopy study of artificially synthesized poly(dA)-poly(dT) DNA molecules on $p$-type Si substrates. For comparison, we also present the electronic density of states (DOS) calculated using an \emph{ab initio} tight-binding method based on density-functional theory (DFT). Good agreement was obtained between experiment and theory. The spectra of DNA networks on the Si substrate showed that the Fermi level of the substrate is located in the middle of the band gap of DNA. The spectra of thick ($\sim 70$ nm) DNA films showed a downward shift of $\sim 2$ eV compared to the network samples.