Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Synthesis of ZnO Nanowires and Nanorods Sadullah Öztürk 1 , 1 , 1, Zafer Ziya Öztürk 1 * 1 Gebze Institute of Technology, Science Faculty, Department of Physics, Kocaeli 41400, Turkey Abstract-In this study, fabrication of ZnO nanostructures such as nanowires and nanorods will be explained in details. ZnO nanowires were grown by cathodically induced sol-gel deposition using an anodic aluminum oxide (AAO) template which is approximately 70 nm diameter and 10 μm length. So vertically aligned ZnO nanowires were grown in AAO template by applying cathodic voltage in aqueous Zinc Nitrate solution at 23 ºC. For electrochemical deposition, three-electrode system was used. The ZnO nanowires are approximately 65 nm diameter and 10 μm lengths. For fabrication of ZnO nanorods hydrothermal technique was used. Firstly sol-gel ZnO solution was coated on glass substrate by spin coating for seed layer. Then ZnO nanorods were grown in Zinc nitrate and HMTA aqueous solution at 90 ºC about 3h. The ZnO nanorods are approximately 40 nm diameter. The vertical nanowires and nanorods were characterized by scanning electron microscope (SEM). ZnO nanostructures are attractive material in last decade because of their n-type semiconducting behavior with large exciton binding energy (60 meV) and a large band gap (3.37 eV). ZnO nanostructures can be used in novel devices, such as photonic devices and very sensitive chemical sensors etc. In literature, there are many techniques for fabricating of ZnO nanowires such as electrochemical and chemical vapor deposition, and also for fabrication ZnO nanorods such as hydrothermal, sonochemical and chemical vapor deposition technique [1,2]. In this study, ZnO nanowires were grown in an AAO template with 75 nm diameter and m in length by electrochemical deposition techniques. The AAO template was grown on Al foil with two anodization techniques and the details were given [1]. ZnO nanowires were electrodeposited in this template with applying -1.5V at room temperature about 2h. Then AAO template was etched in NaOH aqueous solution. So ZnO nanowires was obtained with 70 nm ZnO nanowires was shown in figure 1. On the other hand for preparing ZnO nanorods, ZnO seed layer solution was deposited on glass with spin coating at 2500 rpm about 30s. Then the coated glass was dried in an oven at 130°C for 5min. and this step was repeated 5 times. Finally, ZnO seed layer glass was annealed 300 °C approximately 1h. The ZnO nanorods were grown in Zn(NO 3 ) 2 .6H 2 O and HMTA equmolar aqueous solution at 90 °C about 3h on ZnO seed layer coated glass. For preparing of nanorods, cleavable laboratory bottle was used. ZnO seed layer coated glass was put in vertically. ZnO nanorods were 40nm diameter and 800nm length. ZnO nanorods were shown in Figure 2 It is clearly seen from figure1 that, ZnO nanowires were deposited in AAO template. Because the aspect ratio was very high so the nanowires were come together. Figure 2. Top view of ZnO nanorods It is clearly seen fron fig. 2 that ZnO nanorods were completely covered surface of the ZnO seed layer coated glass. In summary, in this study, two different types of ZnO nanostructures were synthesized by using different techniques. If these two techniques were compared, a hydrothermal technique was easier. In our future works, these nanostructures will be used as gas sensor such as NO2, CO, H2 and volatile organic compound. *Corresponding author: zozturk@gyte.edu.tr [1] N. Tüüzer, Z. Z. Öztürk, 95, 781- 787, 2009 [2] S. Öüzer, Z.Z. Öztürk, Fabrication of ZnO nanowires at room temperature by cathodically induced sol–gel method in press, DOI: 10.1007/s00339-009-5504-8 [3] Z.L. Wang, J. Phys: Cond. Matt. 16, R829 (2004). [4] L. Schmidt-Mende, J. MacManus-Driscoll, Materials Today, 10, 40 (2007). Figure 1. Top view of the free standing of ZnO nanowire 6th Nanoscience and Nanotechnology Conference, zmir, 2010 403
Poster Session, Tuesday, June 15 Theme A1 - B702 The Effect of Annealing Temperature of the Electrical Properties of Tin (IV) Oxide Films Synthesized by Sol-Gel Methods Deniz Gu ltekin 1 *, Mehmet Oguz Guler 1 , Ozgur Cevher 1 , Mustafa Basaran 1 , Hatem Akbulut 1 1 Department of Metallurgical & Materials Engineering, Sakarya University,Sakarya 54187, Turkey Abstract-Semiconducting thin films with tin dioxide have been deposited on soda lime glass substrates from tin (II) chloride dihydrate (SnCl 2 2H 2 O) precursor using the dip-coating sol-gel method. They are prepared from a powder obtained from chlorides directly in our laboratory: 8.37 g of SnCl 2 2H 2 Oare dissolved in 100 ml of absolute ethanol. Finally, sintering was done in a furnace with a heating rate (2 o C/min) to 500 o C and kept for 2 hours). Transparent conductive oxides (TCOs) are very important in modern electronic industry and have been used as plastic liquid crystal display devices, touch sensitive overlays, transparent electromagnetic shielding materials, front electrodes of solar cells, energy efficient windows, etc. Numerous works have been performed on SnO2 thin films for improvement of their electrical conductivity to utilize it as a TCO material in transparent electrode applications [1–6]. SnO2 films are low cost, chemically and environmentally more stable than other TCOs such as ZnO, and Sn-doped In 2 O 3 (ITO) [7,8]. Tin oxide films have been widely fabricated by several workers using a variety of techniques such as chemical vapor deposition [9], metal-organic deposition [10], dc and rf-sputtering, etc. [11,12], among which sol-gel lies in the fact that the doping level, solution concentration and homogeneity can be controlled easily without using expensive and complicated equipment. The Sol-Gel Dip-Coating (SGDC) method is more and more used for the deposition of various thin films on different substrates. This low temperature soft process presents major advantages and the possibility of h igh purity starting materials, an easy coating of large and complex-shaped substrates, almost no perturbations of devices in the case of deposition on top, an easy technology and most of the time a low cost. In the present work the mechanism of formation of a SnO 2 film prepared by the sol-gel method from an ethanolic solution of SnCl 2 .2H 2 O precursor onto soda-lime glass. The precursor salt -SnCl 2 .2H 2 O (Merck)- was dissolved in ethanol and a 0.05M stock solution was made. The gel-like film was prepared onto soda-lime glass (size 4 cm x 2 cm, thickness 2 mm). Before starting the processes, sodium silicate glass substrates were cleaned using distilled water, ammon ia and hydrogen peroxide (5:1:1 by volume) and then rinsed carefully using methanol, acetone and distilled water, respectively The coating was made by applying the precursor salt solution (after a 10-fold dilution with ethanol) drop by drop onto the support and removing the solvent by hot air (60°C). This procedure was continued until a relatively thickness of 400-800 nm layer was deposited. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) us microstructural data. The crystallinity of each film was calculated fro m XRD spectra by Scherrer’s formula. Chemical composition of the synthesized thin films was analyzed by Fourier transform infrared spectra. The surface topography of the thin films were observed by scanning electron microscopy (SEM). The effect of different annealing temperature on the electrical resistivity of the thin films were also analyzed by using four probe resistivity techniques. [1] H.J. Kim, J.W. Bae, J.S. Kim, Y.C. Jang, G.Y. Yeom, N.E. Lee, Surf. Coat. Technol. 131 (2000) 201. [2] Y.K. Fang, J.J. Lee, Thin Solid Films 169 (1989) 52. [3] W.A. Badway, H.H. Afifi, E.M. Elgair, J. Electrochem. Soc. 137 (1990) 1592. [4] J.C. Mannifacier, L. Szepessy, J.F. Bresse, M. Perotin, R. Stuck, Mater. Res. Bull. 14 (1979) 163. [5] E. Shanthi, V. Dutta, A. Banerkee, K.L. Chopra, J. Appl. Phys. 51 (1980) 6243. [6] I.H. Kim, J.H. Ko, D. Kim, K.S. Lee, T.S. Lee, J.-h. Jeong, B. Cheong, Y.-J. Baik, W.M. Kim, Thin Solid Films 515 (2006) 2475. [7] T. Minami, S. Takata, H. Sato, J. Vac. Sci. Technol. 13 (1995) 1095. [8] B. Thangaraju, Thin Solid Films 402 (2002) 71. [9] J. Kane, H.P. Schwiezer, J. Electrochem. Soc. 123 (1976) 270. [10] T.N. Blanton, M. Lelental, Mater. Res. Bull. 29 (1994) 537. [11] R.S. Dale, C.S. Rastomjee, F.H. Potter, R.G. Egdell, Appl. Surf. Sci. 70/71 (1993) 359. [12] A. Martel, F. C-Briones, J. Fandino, R. C-Rodriguez, P. B-Perez, A. Z-Navarro, M. ZTorres, J.L. Pena, Surf. Coat. Technol. 122 (1999) 136. *Corresponding author: dkurt@sakarya.edu.tr 6th Nanoscience and Nanotechnology Conference, zmir, 2010 404
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