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

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 calculated using an 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 (similar to70 nm) DNA films showed a downward shift of similar to2 eV compared to the network samples. (C) 2005 American Institute of Physics.