Ti-TiO x -Pt Metal-Oxide-Metal Diodes Fabricated via a Simple Oxidation Technique
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Ti-TiOx-Pt Metal-Oxide-Metal Diodes Fabricated via a Simple Oxidation Technique Linzi E. Dodd1, Andrew J. Gallant1, David Wood1 School of Engineering and Computing Sciences, Durham University Science Laboratories, South Road, Durham, DH1 3LE, United Kingdom 1
ABSTRACT This work presents the successful production, via a simple oxidation process, of Ti-TiOxPt Metal-Oxide-Metal diodes with excellent electrical asymmetry. TEM analysis has been used to verify the oxide thickness. A thicker layer produces better diodes, although they are of a less uniform nature. The conduction mechanism in these diodes is still under investigation. INTRODUCTION Energy recovery systems have attracted much interest in recent years [1-3]. A significant amount of energy is wasted in the form of heat, leading to research dedicated specifically to energy recovery from this source. In electromagnetic terms, heat is infrared radiation, and its energy content will follow Planck’s Law of spectral distribution. The wavelength of maximum emission intensity λmax within this distribution can be calculated using Wien’s Law (Eqn. 1): λmaxT = 2.897 x 10-3 m.K
(1)
An application example is for heat energy recovery from automotive exhaust pipes. Typical internal combustion engines are only 25-30% efficient. Around 40% of the waste is lost as heat in exhaust gases, with 10-20% of this being radiated through the exhaust pipe surface [4]. For an automobile at a cruising speed, this means a typical value in the range of 10-30 kW is lost through exhaust pipe radiation – we have confirmed these calculations with thermal camera analysis. As a result of increasing pressure on automobile manufacturers to make their products more efficient, a significant amount of research is being undertaken into energy recovery systems. An antenna array, with rectifying diodes, could provide a cost effective, scaleable, high efficiency solution to the issue of energy recovery. In the temperature range of 500-1000 K, Eqn. 1 gives a wavelength of ~3-6 µm, or in frequency terms ~50-100 THz. This is extremely challenging for the rectifying capability of any diode technology. Metal-Oxide-Metal (MOM) structures, with electron tunneling as the transport mechanism, [5-6], are the most promising type of diode to use in this application. The diode itself consists of two dissimilar metals, separated by a uniform native oxide layer, which is sufficiently thin to allow electron tunneling to occur, i.e. is
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