DNA-based organic-on-inorganic semiconductor Schottky structures O ¨ . Gu ¨llu ¨ a, * , M. C ¸ ankaya b ,O ¨ . Barıs ¸ c , M. Biber a , H. O ¨ zdemir b , M. Gu ¨llu ¨ce c , A. Tu ¨ru ¨t a a Department of Physics, Atatu ¨rk University, Erzurum, Turkey b Department of Chemistry, Atatu ¨rk University, Erzurum, Turkey c Department of Biology, Atatu ¨rk University, Erzurum, Turkey Received 29 December 2007; received in revised form 6 February 2008; accepted 7 February 2008 Available online 13 February 2008 Abstract A sandwich device has been fabricated from DNA molecular film by solution processing located between Al and p-type silicon inorganic semiconductor. We have performed the electrical characteristics of the device such as current–voltage (I–V), capacitance–voltage (C–V) and capacitance–frequency (C–f ) at room temperature and in dark. The DNA-based structure has showed the rectifying behavior. From its optical absorbance spectrum, it has been seen that DNA has been a semiconductor-like material with wide optical band energy gap of 4.12 eV and resistivity of 1.6  10 10 V cm representing a p-type conductivity. # 2008 Elsevier B.V. All rights reserved. Keywords: Schottky barrier; Organic–inorganic contact; DNA; Organic semiconductor 1. Introduction Deoxyribo nucleic acid (DNA), the blueprint of life, has taken centre stage in bio-physical chemistry research during the past few decades [1]. The elucidation of the molecule’s structure 50 years ago and the unravelling of the genetic code revolutionized the field of biotechnology. They sparked the creation of whole new industries based on this knowledge and on the various tools and technologies that have subsequently developed. Biologically, the well-known function of DNA is to code for functional proteins that are the expressed form of hereditary, genetic information. But in the past few years, the discovery that DNA can conduct an electrical current has made it an interesting candidate for other roles that nature did not intend for this molecule [1]. In particular, DNA could be useful in nanotechnology for the design of electric circuits, which could help to overcome the limitations that classical silicon- based electronics is facing in the coming years. This field is highly interdisciplinary, merging physics, biology, chemistry, computer science, engineering and so on, to use the DNA molecules for producing a new range of electronic devices that are much smaller, faster and more energy efficient than the present semiconductor-based electronic devices [1]. In mole- cular-scale systems, DNA is one of the most promising materials because they have several unique advantages [2]; such as nanometer-scale molecular film, adjustable length, and self-assembly property [3–5]. Understanding the electrical conduction mechanism through a DNA molecule is essential for electronic device applications, and furthermore, charge transport in DNA molecules is also related with the radiation damage and repair mechanism of DNA in biological implications [3,6]. Recently, several experimental and theore- tical studies have demonstrated conducting behaviors of DNA molecules by direct electrical conductivity measurements [3,7– 12]. In many published works, the current–voltage (I–V) data of double-stranded DNA molecules reported [13]. Several models have been proposed to explain the conduction mechanisms of DNA molecules for which electrical conductions via a multi- step charge transport (i.e., hopping) mechanism [7,9,14–16] and a single-step super-exchange (i.e., tunneling) mechanism [7,14,15] were suggested. Since guanine (G) has been known as the DNA base with the lowest ionization potential, many groups www.elsevier.com/locate/apsusc Available online at www.sciencedirect.com Applied Surface Science 254 (2008) 5175–5180 * Corresponding author. Tel.: +90 442 231 4081; fax: +90 442 236 0948. E-mail address: omergullu@gmail.com (O ¨ . Gu ¨llu ¨). 0169-4332/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2008.02.019