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ZnO thin films for organic/inorganic heterojunctions
|Iwona A. Kowalik 1, Łukasz Wachnicki 2, Elżbieta Guziewicz 1, Krzysztof Kopalko 1, Sergiey Yatsunienko 1, Marek Godlewski 1,2, Victor Osinniy 1, Tomasz A. Krajewski 1, Tomasz Story 1, Elżbieta Lusakowska 1, Wojciech Paszkowicz 1|
1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
Zinc oxide is a wide band gap II-VI semiconductor which is characterized by unique physical and chemical properties, which led to many applications of this material. Thin films of ZnO are used for the photogeneration of charge carriers in the solar cells. Appropriately doped ZnO may be transparent and conductive, and can therefore be used as a transparent electrode in the solar battery and microelectronics.
ZnO is also a prospective semiconductor candidate for making hybrid organic/inorganic devices. However, because of destruction of organic materials at high temperatures, these applications of ZnO require extremely low growth temperature. Our studies show that extra-low temperature ZnO growth is crucial to avoid formation of foreign phases and spinodal decomposition when transition metal atoms are introduced during the growth process.
The ZnO thin films were grown by Atomic Layer Deposition (ALD) method at extremely low temperature (60-1200C) with use of the very reactive metalorganic zinc precursor (diethylzinc, DEZn).
The obtained polycrystalline ZnO films are characterized by good crystallographic quality as confirmed by X-ray diffraction. Atomic Force Microscopy (AFM) study confirms good structural quality of these low temperature ZnO films. Root Mean Square (RMS) achieve 0.1 nm for film obtained for growth temperature 60°C.
The room temperature photoluminescence (PL) studies show strong emission of excitonic origin (“edge” PL) observed even for very low temperature grown ZnO. Our studies also show that ZnO thin films obtained at extremely low growth temperature are characterized by low free carrier concentration below 5x1017cm-3 at room temperature.
Our results show that the ALD growth ZnO with DEZn precursor performed at extra-low temperature resulted in unexpectedly high quality material.
The work was supported by polish grant SPUB No. 180/6.PR UE/2006/7 (6 Framework Programme – priorytet 2 (IST)) and European project with an acronym VERSATILE
Presentation: Poster at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Iwona A. Kowalik
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-08-03 14:11 Revised: 2009-06-07 00:44