Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Synthesis of ZnO nanorods by a simple Hydrothermal method Leili Motevalizadeh * 1 ; Zahra Heidary * 1 ; Nasser Shahtahmassebi 2 1 Department of Physics, Faculty of Sciences, Islamic Azad University, Mashhad branch, Mashhad, Iran 2 Department of Physics, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran Abstract- ZnO nanorods have been synthesized in low temperature by a novel simple hydrothermal method without using any substrates, catalysts and autoclave. The samples have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns confirm that the prepared ZnO powders with different time reaction have the single-phase Wurtzite structure. SEM images show that the sample was in the form of ZnO nanorods, with the average lengths of 2-3 μm and diameters of 200-400 nm. In recent years studies on one-dimensional (1-D) nanostructures such as nanotubes, nanowires, and nanorods have received increasing attention because of their great potential applications in the fields of scanning microscopes and sensors [1], field emission devices [2], biological probes [3] , and nanoelectronics [4]. ZnO is one of the most important materials due to its large band gap energy of 3.37 eV and large exciton binding energy of 60 meV at room temperature [5]. One-dimensional ZnO nanostructures have attracted considerable interest because of their promising applications in nanoscale optoelectronic devices [6]. For preparation of 1-D ZnO nanostructures various approach such as chemical vapor deposition (CVD) [7], thermal evaporation [8], and pulsed laser deposition (PLD) [9] have been reported. Recently, Ashfold reported the preparation of 1-D ZnO nanostructures via hydrothermal method [10, 11]. In this paper we reported the synthesis of ZnO nanorods via the hydrothermal method at low temperature (90 ºC) without using autoclave, catalysts, and templates. Aqueous solution of deionized water, zinc chloride and ammonia (25%) were prepared. The mixture solution transferred into closed balloon in presence of nitrogen gas. the balloon was Sealed and heated in an oil bath at 90°C for (a) 5 h, (b) 10 h, (c) 15 h, respectively. After this stage, the balloon was cooled down to room temperature. Following carefully washing with deionized water and drying at 40°C under air atmosphere, the white precipitates were collected, and kept for advance characterization. Figure 1 shows X-ray diffraction patterns from final products with different reaction time. It is observed that all of the diffraction peaks match the hexagonal ZnO structure with lattice constants of a=b=3.249 Å and c=5.206 Å. Figure 2 shows the SEM images of the products. A comparison between SEM images reveals that with the increase of reaction time initial nanoclusters (Fig. 2-a) divide into uniform nanorods. By analysis of SEM images (Fig. 2-b, Fig. 2-c) it is found that the average diameter of fabricated ZnO nanorods is around 250 nm and their length is around 2.5 μm. In summary, we synthesized ZnO nanorods via a simple hydrothermal method without using autoclave. XRD analysis confirmed the formation of hexagonal ZnO structure. SEM images showed that the length and diameter of nanorods were 2-3 m and 200-400 nm, respectively. Meanwhile, had synthesized ZnO nanorods with a diameter of 70 nm using Intensity (a.u.) Intensity (a.u.) Intensity (a.u.) 0.8 0.6 0.4 0.2 1 0.8 0.6 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 1 0 (a) 20 30 40 50 60 2 0 (b) 20 30 40 50 60 70 80 2 0 (c) 20 30 40 50 60 70 80 2 0 Fig. 1: X-ray diffraction patterns from final products with different reaction time, (a) 5h, (b) 10h, (c) 15h. autoclave [12]. The difference between our nanorods diameter and that of Ref. [12] is due to different ambient pressure in the two synthesis processes. *Corresponding authors: lmotevali@mshdiau.ac.ir, z.heidary.62@gmail.com [1] R. Service, Science 281 (1998) 940. [2] S. Fan et al; Science 283 (1999) 512. [3] G.I. Dovbeshko et al; Chem. Phys. Lett. 372 (2003) 432. [4] S.J. Tans, R.M. Verschueren, C. Dekker, Nature 393 (1998) 49. [5] M. Willander et al; Superlattices and Microstructures, 43 (2008) 352. [6] C.R. Gorla et al; J.Appl. Phys. 85 (1999) 2595. [7] J.J.Wu, S.C. Liu, Adv. Mater. 14 (2002) 215. [8] X. Kong et al; Materials Chemistry and Physics; 82 (2003) 997. [9] Ye. Sun et al; Chemical Physics Letters; 396, (2004) 21. [10] M.N.R. Ashfold et al; Chem. Phys. Lett. 431 (2006) 352. [11] M.N.R. Ashfold et al; Adv. Mater. 17 (2005) 2477. [12] J. H. Yang et al; Cryst. Res.Technol. 44 (2009) 87. (a) (b) (c) Fig. 2: SEM images of ZnO nanorods prepared with different reaction time, (a) 5h, (b) 10h, (c) 15h. 6th Nanoscience and Nanotechnology Conference, zmir, 2010 377
Poster Session, Tuesday, June 15 Theme A1 - B702 Photoluminescence enhancement from Silicon/Germanium quantum structures 1 . Kalem, 2 P. Werner, 3 V. Talalaev, 4 Ö. Arthursson TUBITAK-UEKAE National Research Institute of Electronics and Cryptology, Gebze-Kocaeli, Turkey 2 Max-Planck-Institute, Department of Experimental Physics, Halle(Saale), Germany 3 ZIK "SiLi-nano" Martin-Luther-Universität (Halle), Karl-Freiherr-von-Fritsch-Str. 3 D - 06120 Halle, Germany 4 Microtechnology and Nanosciences Department., Chalmers University of Technology, Göteborg, Sweden Abstract— This work describes the results of an investigation of optical and electronic properties of Si/Ge quantum heterostructures grown by molecular beam epitaxy on Silicon wafers. During the last decade, the group IV semiconductor nano structures has been at the focus of intense research for promising applications in the field of information storage, optoelectronic devices, communications and sensors. Focusing on the Si and Ge based quantum structures concerns the development of nano memories, novel electroluminescent devices, fabrication of new light harvesting layers for the next generation of solar cells, biosensors, development of new information processing devices, etc. Basic scientific research activity on the light emission of these Group IV nano structures has particular reasons for understanding microscopic mechanisms behind the related effect [1-4]. Knowledge generated from these activities can pave the way to manufacturing where, for example, CMOS compatible electronic and photonic components can be integrated with a lower cost while enhancing performance values for processors. In order to realize above mentioned applications, the fundamental mechanism of the excitation process, optical and electronic properties, the charge trapping in Si and Ge based quantum structures (nano wires, nano clusters, superlattices) are to be explored in greater extent. In this work, an investigation of optical, electronic and structural properties was carried out on Si/Ge multilayer nano wires grown by molecular beam epitaxy on Si wafers. The layers were treated by acid based vapors in an attempt to induce efficient carrier confinement in the Ge dots and wells. A significant enhancement in infrared photoluminescence at room temperature was observed from Si/Ge quantum structures (multilayers, nano wires, dots) as shown in Figure for a variety of quantum structures exposed to HF based acid vapors. The emission (>1200 nm) originates mainly from Ge dots and the band edge emission from Si at 1100nm (Si TO ) with possible contribution from dislocations. The results are correlated with Raman, ellipsometry and TEM analysis in an attempt to clarify the origin of the emission enhancement from Si/Ge nanostructures. PL intensity, a.u. Ge dots 804d Si(9)/Ge(2)x9ML 3x10 5 2x10 5 Si(100)/Ge(80)-060425 1x10 5 0 . Si(200)/Ge(100)-070614 . 800 1000 1200 1400 1600 Wavelength, nm Figure : Room temperature photoluminescence from Si/Ge multilayers as compared to a reference Ge dot. Controlling light emission in tele communication wavelengths from Si/Ge quantum structures has a great potential for novel LED device fabrication particularly for applications ranging from biology to interconnects in nanoelectronics. This work was supported by TUBITAK-BMBF programme under contract No: TBAG-107T624. *Corresponding author: s.kalem@uekae.tubitak.gov.tr [1] D. Grützmacher et al., Materials Science and Engineering C 27, 947 (2007) [2] Talalaev et al., Physica Status Solidi A 198, R4- R6 (2003). [3] N.D. Zakharov et al., Appl. Phys. Lett. 83, 3084- 3086 (2003). [4] G.E. Cirlin et al, phys.stat.sol. (b) 232, R1-R3 (2002). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 378
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