Photonic crystals in biology

More documents

Recommendations

Info

Poster Session, Tuesday, June 15 Theme A1 - B702 Temperature and thickness dependence of the grain boundary s cattering of the Ni-Si Silicide Films Formed at 500 C by Rapid Thermal Annealing of the Ni/Si Films G. Utlu 1 *, N.Artunç 1 S.Selvi 1 1 Department of Physics, Ege University, 00, Turkey Abstract-In this study, Ni-Si silicide films with 18-290 nm thicknesses are studied as a function of temperature and film thickness over the temperature range of 100-900 °K. The most striking behavior is that the variation of the resistivity of the Ni-Si silicide films with temperature exhibits an unusual temperature-dependent behavior with respect to those of the transition and un-transition metals. We have also shown t hat in the temperature range of (100-Tm) °K paralel-resistor formula is reduced to Matthiessen’s rule and D Debye temperature is independent of the temperature for a given thickness range, whereas at high temperatures it increases slightly with thickness. We have found that for the temperature range of (100-Tm) °K, lineer variation of the resistivity of the Ni-Si silicide films with temperature is caused from both the grainboundary scattering and electron-phonon scattering and resistivity data could be analyzed very well in terms of the Mayadas-Schatzkes (M-S) model. In recent years silicides, intermetallic co mpounds of silicon and transition metals, have received much attention because of their wide application in very large-scale integrated circuits (VLSI) and ultra large-scale integrated circuits (ULSI) [1-3]. Because they show metallic behavior with low electrical resistivity, high electro-migration resistance, high thermal stability and resistance to acids [1, 4]. Due to these properties, they have been proposed as candidates for replacing aluminum alloys for applications in microelectronics [3-5].Metal silicides can be synthesized by various techniques, e.g. solid-state reaction of thin metal films deposited on Si wafer, explosive silicidation, react ive deposition, and ion implantation [6-9] In this study, the first aim is to deposit Ni thin films, with thicknesses of 7.0 –89 nm, onto n-type Si(100) substrate by thermal evaporation technique, and then to anneal these Ni /Si bilayers by rapid thermal annealing (RTA) process for 60 s at 500 C, so as to synthesize NiSi (n ickel mono-silicide) silicide films by solid-state reaction technique. The second aim is to investigate the temperature dependence of the electrical resistivity of Ni-Si silicides over the temperature range 100- 900 °K. And the final aim is to analyze the resistivity data of Ni-Si silicides in terms of the M-S grain boundary scattering model, and calculate the R reflection coefficient of the films. The correlation of Ni–Si silicide formation with its electrical and morphological properties is also established. The temperature-dependent resistivity measurements of our Ni-Si silicide films with thickness of 18-290 nm are studied as a function of temperature and film thickness over the temperature range of 100-900 °K. The most striking behavior is that the variation of the resistivity of the Ni-Si silicide films with temperature exhibits an unusual temperature-dependent behavior with respect to those of the transition and untransition metals. Our measurements show that the total resistivity of the Ni-Si silicide films increases linearly with temperature up to a Tm temperature, at which resistivity reaches a maximum, thereafter Tm it decreases rapidly and finally is zero at 800 °K. Moreover, in this study, Tm temperature is found to decreases with both decreasing film thickness and annealing temperature / or Si concentration and to shift from 610 °K to 490 °K with decreasing film thickness from 290 to 18 nm, corresponding to increased concentration of Si in the lattice. Paralel–rezistör formula uses for analysing of the temperature dependent resistivity datas for several thin film and metal silicid film in a wide temperature range (4-1000) °K [10-13]. We have shown that in the temperature range of (100-Tm) °K paralel-resistor formula is reduced to Matthiessen’s rule and D Debye temperature is independent of the temperature for a given thickness range, whereas at high temperatures it increases slightly with thickness. D Debye temperature are found to be about 400-430 K for all the Ni-Si films. We have also shown that for the temperature range of (100- Tm) °K, lineer variation of the resistivity of the Ni-Si silicide films with temperature is caused from both the grain-boundary scattering and electron-phonon scattering and resistivity data could be analyzed very well in terms of the Mayadas- Schatzkes(M-S)model. Theoretical and experimental values of Reflection coefficients are calculated by analyzing resistivity data using M-S model and f.d =f(d) plots respectively. According to our analysis, for a given temperature R increases with decreasing film thickness, whereas it is almost constant over a thickness range of 200-67 nm and 47-18 nm, for which silicide films have almost same phases. For room temperature (T=295 °K) the average values of theoretical and experimental reflection coefficient are calculated to be R th = 0.44, R th = 0.66 and R exp = 0.46, R exp = 0.67 by taking an average over the thickness ranges of 200-67 nm and 47-18 nm respectively. According to our XRD, RBS and SEM measurements for the thickness of 200-67 n m Ni, Ni 3 Si and NiSi silicide phases coexist, while NiSi and Si-rich silicide phases are present over the range of 47-18 nm. This phase transformation with decreasing film thickness should be responsible for the increase observed in the values of both R reflection coefficient (or the grain boundary resistivity) and total resistivity of all the Ni-Si silicide films. Corresponding author: gokhan.utlu@ege.edu.tr [1] S.P.Murarka, Silicides for VLSI Application, Academic, NewYork,(1983). [2] M.A. Nicolet, S.S.Lau, in: N.G. Einspruch (Ed.), VLSI Electronic Microstructures Science,6,Academic pres, New York,(1983). [3] Y. Hu and S. P. Tay, J. Vac. Sci. Technol. A 16, 1820 (1998). [4] A.H. Reader et al, Rep.Prog. Phys. 56 1397 (1992). [5] J.P. Gambino, E.G. Colgan, Mater. Chem. Phys. 52, 99 (1998). [6] B.A. Julies et al, Thin Solid Films, 347,201 (1999). [7] S. Abhaya et al, Appl. Surf. Sci. 253,3799 (2007). [8] L.A Clevenger, C.V. Thomson, K.N. Tu, J. Appl. Phys. 67 (1990) 2894. [9] Gi Bum Kim et al, J. Vac. Sci. Technol.B 21, 1319 (2003). [10] M. Gurvitch, Physical Review B, 24, 7404 (1981). [11] M.Milewits et al, Physical Review B, 13, 5199 (1976). [12] F. Nava and K.N. Tu, Journal of Applied Physics, 61, 1085 (1987). [13] F. Nava, K.N. Tu, O. Thomas, J.P. Senateur, R. Madar, A. Borghesi, G. Guizzetti and O. BiSi, Materials Science Reports, 9, 141 (1993). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 373
Poster Session, Tuesday, June 15 Theme A1 - B702 Fabrication of Alumina Borate Nanofibe r by Electros pinning Technique Mehtap Ozdemir 1 *, Aslihan Suslu 1 , Umit Cöcen 1 and Erdal Celik 1 1 Department of Metallurgical and Materials Engineering, Dokuz Eylul University, 35160, Izmir, Turkey Abstract-Alumina borate (Al 18 B 4 O 33 ) nanofibers have been successfully fabricated by electrospinning method using a solution that contains poly (vinyl alcohol) (PVA) and Aluminium acetate stabilizied with boric acid. The effect of viscosity and temperature were investigated. DTA/TG analyses were done to determine the heat treatment regime. Morphology of the fibers was investigated by SEM analyses and phase structure of fibers was obtained using XRD and chemical bonding structure was determined by FTIR. One-dimensional materials, such as nanowires, nanorods, nanowhiskers and nanofibers, have stimulated great interest due to their importance in basic scientific research and potential technology applications. They are expected to play an important role as both interconnects and functional components in the fabrication of nanoscale devices. Many unique properties have already been proposed or demonstrated for this class of materials, such as high elastic modulus and tensile strength, chemical inertness, excellent resistance to oxidation/corrosion, low thermal expansion coefficient, high thermal conductivity, stability at high temperature and low-cost production [1-5]. Of these properties, aluminium borate is one of the most common materials for a variety of applications such as high temperature structure components, nonlinear optical and tribological materials, electronic ceramics and reinforced composites materials [2, 6]. Electrospinning is a most preferred technique to produce fibers with a diameter of 20-1000 nm. The diameter of the fibers depends on process parameters; including viscosity of the solution, applied electric field, distance between the collector and needle and feeding rate of the solution [7]. In this study, we attempt to form alumina borate nanofibers and investigate the effect of viscosity during the electrospinning process on nanofiber morphology and spinability. We first prepared PVA solutions at different concentrations. Then aluminium acetate stabilized with boric acid (CH 3 CO 2 Al(OH) 2 .1/3H 3 BO 3 ) added to PVA solution and stirring was continued until transparent and homogeneous solution was obtained. Viscosity of solutions was determined by CVO 100 Digital Rheometer. The alumina borate/PVA fibers were heat treated at 800- 1200 o C for 2 h in air. The prepared solution used in the electrospinning was dried at 100 °C for 1 h and the obtained powder subjected to thermogravimetric differential thermal analysis (DTA/TG) to define the reaction type of intermediate temperature products and to use suitable process regime. The chemical bonding structures of fibers before and after heat treatment were determined by Fourier Transform Infrared Spectroscopy (FTIR). The X-ray diffraction (XRD) measurements were performed for crystal phase identification (Rigaku D/Max- 2200/ average fiber diameter of nanofibers was characterized by scanning electron microscope (SEM). Solution viscosity plays a major role for producing uniform nanofiber. At low viscosity, it is common to find beads along the fibers. When the viscosity increases, there is a gradual change in the shape of the fibers until smooth fibers are obtained [8]. For spinability viscosity must be neither very dense nor dilute. Viscosity of the prepared solutions at different concentrations are determined in the range of 0.17- 2.34 Pa.s. After the heat treatment of electrospun fibers at 800 o C and 1200 o C, crystalline Al 4 B 2 O 9 and Al 18 B 4 O 33 fibers were obtained respectively. As a result of high temperature, fiber diameters reduced from 922 nm to 523 nm. In conclusion, the electrospinning technique was used to produce alumina borate/PVA composite nanofibers. The effect of viscosity on spinability and the morphology of alumina borate/PVA nanofibers were investigated. After heat treatment at 1200 o C, alumina borate (Al 18 B 4 O 33 ) fibers were produced. It has been found that viscosity of the prepared solution affects the fiber morphology. Increasing the viscosity as a result of increasing solution concentration thicker fibers are obtained and furthermore spinability of solution become more difficult because dense solution leads to clogging of needle tip. This work was supported by BOREN (National Boron Research Institute) and TUBITAK (Scientific and Technical Research Council of Turkey) project number 105M363. Also, authors M.O and A.S acknowledge the support from TUBITAK, in the framework of the National Scholarship Programmes for PhD Students. *Corresponding author: 0Tmehtap.ozdemir@ogr.deu.edu.tr [1] Jian Wang, Guiling Ning , Xuefeng Yang, Zhihong Gan, Hongyu Liu, Yuan Lin, Materials Letters 62 1208 (2008). [2] Haisheng Song, Junjie Luo, Miaodan Zhou, Elawadmihammed Elssfah, Jun Zhang, Jing Lin, Sujing Liu, Yang Huang, Xiaoxia Ding, Jianming Gao, and Chengcun Tang, Crystal Growth & Design, 7, 576 (2007). [3] Hongqin Dai, Jian Gong, HakyongKim and Doukrae Lee, Nanotechnology 13 674 (2002). [4] Elawad Elssfah and Chengcun Tang, J. Phys. Chem. C, 111, 8176 (2007). [5] C C Tang, EMElssfah, J Zhang and D F Chen, Nanotechnology 17,2362 (2006). [6] Jun Wang , Jian Sha , Qing Yang , Youwen Wang , Deren Yang, Materials Research Bulletin 40, 1551 (2005). [7] Dan Li and Younan Xia, Adv. Mater. 14, 16(2004). [8] RAMAKRISHNA S., Fujihara K., Teo W-E., Lim T-C., Ma Z., “An Introduction to Electrospinning and Nanofibers”, World Scientific Publishing Company, United States of America, (2005). 6th Nanoscience and Nanotechnology Conference, zmir, 2010 374
Page 1 and 2:
Poster Presentations 1st Day 2nd Da
Page 3 and 4:
Poster Session, Tuesday, June 15 Th
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Poster Session, Tuesday, June 15 Sy
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
P Poster Session, Tuesday, June 15
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
P P P,P Poster Session, Tuesday, Ju
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
P P P and Poster Session, Tuesday,
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116: Poster Session, Tuesday, June 15 Th
Page 125 and 126: Poster Session, Tuesday, June 15 Hy
Page 165: Poster Session, Tuesday, June 15 Th
Page 173 and 174: Poster Session, Tuesday, June 15 Pr
Page 201 and 202: P Torr. pressure P pressure P and P
Page 207 and 208: P P Mustafa Poster Session, Tuesday
show all

Photonic crystals in biology

Create successful ePaper yourself

Delete template?

Save as template?