Synthesis and Characterization of SnO2 and Fe3O4 Composite Grown by Microwave Method

Sinyee Gan1, K. K. Lim1, M. A. A. Hamid1*, R. Shamsudin1, W. S. Chiu2

1 School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

2 Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia

*Email: azmi@ukm.my

Keywords: Thin film, tin dioxide, domestic microwave

Abstract. In this research, SnO2 and Fe3O4 composite thin film were grown on glass slides by using commercial microwave oven. The obtained samples were characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Ultraviolet-Visible Spectroscopy (UV-Vis) and Photoluminescence (PL). The growth of SnO2 was carried out for the periods of 60 s, 50 s and 40 s with two 5-second time intervals. XRD pattern shows the presence of two phases: SnO2 and Fe3O4 in all samples of grown composites. It was found that the sample grown for 60 s having dominant SnO2 phase while for the durations of 40 s and 50 s, the phase of Fe3O4 are more dominant. The Fe3O4’s phases are believed originated from chemical reaction involving the steel wool which was used to stimulate the oxidation of Sn into SnO2. SEM observations reveal heavily agglomerated spherical-like particles which size ranges from 80.6 nm to 113.6 nm. EDX analysis indicates that composites with the growth time of 60 s contain the highest weight percentage (13.52 %) of Sn, followed by those composites with the growth time of 50 s (5.47 %) and 40 s (4.31 %). UV-Vis spectroscopy shows the optical band gap energy for the 60-second growth time’s composite, is 3.9 eV, which is well-correlated with the value of bulk of SnO2.PL characterization shows that the peaks of the curve fall within the range between 490 nm and 900 nm. The presence of oxygen defects probably causes the deterioration of optical bandwidth.

I. INTRODUCTION

Nanosized semiconductor particles have been studied with extensive efforts both experimentally and theoretically. Their potential in a variety of semiconductor electronics, solar energy conversion, devices in photonics and optoelectronics industry [1,2] necessitates such studies. Synthesis of nanosized materials by controlling the size, morphology and chemical composition of both is likely to create opportunities to explore new physical properties better [3]. Rod semiconductor and nanosized semiconductor wire has attracted the attention of researchers because of their physical and their potential applications in various electronic and photonic devices [4].

Tin dioxide has been used in important areas of transparent oxide conductors, gas sensors and catalysts. Tin dioxide is a substance that has an attractive combination of high electrical conductivity and optical characteristic [5]. Plus, tin dioxide is also used as electrode material in solar cells, light emitting diodes and other optoelectronic devices [6]. In the field of gas sensors, tin dioxide is often chosen as the main material instead of ZnO or In2O3 [5]. This is because tin dioxide is a highly sensitive, cheap gas sensor which can be produced easily. Previous studies present methods based on domestic microwave techniques which are time consuming in preparing tin dioxide. For example, in Cirere et al. [7], the production of tin dioxide using domestic microwave technique after undergoing traditional treatment at high temperatures (450 o C - 1000 o C) with at least 2 hours. Few previous studies require also an additional heat treatment at a temperature of at least 300 o C such as annealing process and the need for a further synthesis after radiation using domestic microwave [3]. Hence, such process increases the processing time, number of steps and cost of the production of tin dioxide. The aim of this study is to produce a shorter growth time of tin

Advanced Materials Research Vol. 895 (2014) pp 291-297Online available since 2014/Feb/13 at www.scientific.net© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.895.291

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 130.207.50.37, Georgia Tech Library, Atlanta, USA-12/11/14,09:23:37)

dioxide composites using a domestic microwave oven. An advantage discovered in this study is the reduction in time needed to grow the tin dioxide without affecting much of the crystallinity, optical properties, and morphology of the grown tin dioxide.

II. MATERIALS AND METHODS

There are 2.5 g of tin granules, a 2.5 g steel wool and a silicon substrate with the dimension (25.4 x 76.2) mm2 were used to prepare tin dioxide. Both tin granules and the steel wool were placed inside a clean alumina crucible followed by two pieces of glass slides placed on top of the alumina crucible. A ceramic cover was put on the glass slides (Fig. 1). The crucible was then put at the middle position of a domestic microwave oven with power of 800 W. The growth time was set to 60 s, 50 s and 40 s with two-step 5 seconds time interval. The discrete number of steps of time interval was chosen over continuous growth time as preliminary studies show no result could be reproduced by setting continuous growth time. Furthermore, the glass slides were break or cracked due to spark created during the reaction of cotton steel wool and tin granules.

Fig. 1. Schematic diagram of thermal evaporation setup

Hence, the overall growth time includes two 5-second resting periods and two 20-second heating periods. For example in a 60-second growth time, an initial 10 s of microwave heating is followed by a 5 s rest time and then continue heating for another 20 seconds, and stopped for 5 s rest followed by continuing heating for another 20 s. The morphology, chemical composition and crystal structure of the as-grown SnO2 nanoparticles were examined using SEM (Supra 55 VP Zeiss) coupled with EDX (oxford instruments) and XRD (D8 advance XRD diffractometer). The PL property of the as-grown SnO2 nanoparticles was investigated at room temperature using Renishaw inVia Raman Microscope with a He-Cd laser as the excitation source with 325 nm line supplied by power of 0.5 mW. UV-Vis (Perkin Elmer LAMDA 900) was used to measure the optical energy band gap and optical properties.

III. RESULTS AND DISCUSSIONS

Fig. 2 illustrates the XRD pattern of the deposited SnO2 composite which can readily be indexed to the tetragonal rutile structure with lattice constants a = 4.74 Å and c = 3.19 Å. With respect to the 60 s growth time XRD pattern shows the presence of both SnO2 and Fe3O4 phases with the former’s intensity peaks are sharper and higher than that of the latter. However for the SnO2 composite deposited in 50 s growth time, the SnO2 phase has relatively lower intensity peaks compared to Fe3O4 phase’s intensity peaks. There are no SnO2 peaks detected in the 40-second grown composite. The impurity Fe3O4 was due to the oxidation of steel wool as a byproduct of the main reaction in

292 Solid State Science and Technology IV

producing SnO2. This result indicates that the steel wool would initially be oxidized first during initial heating period prior to oxidizing tin. The XRD analysis of the 60 s grown tin dioxide shows eight peaks at 2-thetas 26.7°, 33.9°, 38°, 38.9°, 42.8°, 51.8, 54.8° and 59.9° and phases (110), (101), (200), (111), (210), (211), (220) and (002) match with the result observed by [8,9]. On the other hand, the Fe3O4 phasehas 6 peaks at 2-thetas 30.2°, 35.5°, 37.2°, 43.2°, 53.5° and 57° with phases (220), (311), (222), (400), (331), (422) and (511) match with the result observed by [10]. The crystalline size, D of the as-grown composites is computed using Scherrer’s formula and the full width at half maximum (FWHM) of the peak (110) [11]:

D = 0.9λ/(βcosθ), (1)

where λ, β and θ are the X-ray’s wavelength (Cu Kα line of 0.154 nm), FWHM and Bragg diffraction angle respectively. The calculated result shows that size of crystallite for the 60 s grown SnO2 is 16 nm while for those grown for 50 s and 40 s are 41 nm and 11 nm respectively.

Fig. 2. XRD pattern of as-grown SnO2 nanoparticles

---- SnO2

Fe3O4

Inte

nsit

y

2theta

Advanced Materials Research Vol. 895 293

The SEM image of Fig. 3 shows that all grown composites thin film produced agglomerated sphere-like particles. For a 60-seconds grown composite, the sizes are between 80 nm and 113 nm, and more dense as compare to the other two growth condition. The composite thin film grown in 60-, 50- and 40-second have similar structure in terms of size and shape. The agglomeration is possibly due to the large surface area of particles and might also be explained by Ostwald ripening phenomenon [12,13]. It is also observed most of the formed particles are similar in size suggesting similar nucleation and growth rate constituted the reaction. The formation of thin film most probably through the by-vapor transport mechanism where the vapor would be deposited on glass slides, nucleate thus forming thin film as described by Stranski-Krastanov growth mode which is typical for non-lattice match substrate-composite [14].

Fig. 3. SEM micrographs of as-grown SnO2 nanoparticles

(a) in 60 s (b) in 50 s (c) in 40 s

The EDX analysis as shown in Fig. 4 shows the presence of the elements in the composites in terms of their weight percentage and atomic percentage. The elements that had been detected from EDX included O, Na, K, Mg, Si, Ca and Sn. Most of the detected elements such as O, Na, K, Mg, Si, Ca originated from the glass slide. The EDX spectrum’s peak for Fe is not shown as the peak is more than 5 keV. The 60-seconds grown composite has the highest weight percentage of element Sn which is 13.52 % compared to 5.47 % for composite grown in 50 s and 4.31 % for composite grown in 40 s, which explains the small or nonexistence of peaks of the element on the XRD spectra. UV-Vis analysis was performed within the wavelength ranged from 200 nm to 800 nm which corresponds to the range from ultraviolet wavelength to visible wavelength. The optical analysis was only performed on the 60 s grown composite as it has a higher composition of SnO2. The optical band gap energy is obtained by plotting the graph of (αh )2 versus h From Fig. 5, the optical band gap energy is discovered to be 3.9 eV which is the value of standardization of the bulk SnO2 [15].

294 Solid State Science and Technology IV

Fig. 4. EDX spectrum of SnO2 structures in (a) 60 s (b) 50 s (c) 40 s

The room temperature PL spectrum of SnO2particles is shown in Fig. 6. There are two peaks in the PL spectrum. The first peak is between the wavelength 490 nm and 620 nm while the second peak is between the wavelength 620 nm to 900 nm which is the dominant. Two visible light emissions with each peak wavelength centered around 590 nm and 720 nm was observed. From the study of Pan et al. [16], the two peak emissions are caused by a donor-recipient pair transition’s dominant peak which is due to the creation of impurities-induced crystal defects during the growth of the tin dioxide. The impurity found in this study is characterized by Fe3O4 as indicated by XRD analysis. Ions Fe 2+ and Fe 3+ are in general have the effect of quenching on luminesen visible due to the fact infrared transitions are characteristic of these ions [17]. This visible light emission is the sign of oxygen vacancies or Sn interstitials that had been formed during the synthesis process, which is known to be related to the level of defection within the band gap of SnO2. The obtained morphology difference may be claimed to exert some influence on PL property. However, according to [3], the PL property of a material is strongly dependent on the type of defect in the crystal.

Advanced Materials Research Vol. 895 295

Fig. 5. UV-Vis for optical band gap energy of SnO2 structures in 60 s

Fig. 6. PL spectrum of SnO2 nanoparticles in 60 s

IV. CONCLUSION

As a conclusion, SnO2 and Fe3O4 composite thin film can be synthesized for at least for a 60 s growth time with resting time interval of 5 s using a domestic microwave oven. Thus, a crystalline with rutile tetragonal structure and morphological sphere-like structure can be achieved within 1 minute of growth time. From UV-Vis observation, the optical band gap energy for the 60-second grown SnO2 is 3.9 eV. PL measurement shows that the SnO2 nanoparticles emitted visible light that may have potential to be applied in electronics or optoelectronics devices.

ACKNOWLEDGMENTS

Authors appreciated the support of Universiti Kebangsaan Malaysia, UKM for facilities and financial assistance under research university grant (UKM-DLP-2011-017).

296 Solid State Science and Technology IV

REFERENCES

[1] J.J. Zhu, M.Z. Zhu, X.H. Liao, J.L. Fang, M.G. Zhou & H.Y. Chen, Rapid synthesis of nanocrystalline SnO2 powders by microwave heating method. Materials Letters 53(1-2) (2002)12-19.

[2] M. Krishna & S. Komameni, Conventional-vs microwave-hydrothermal synthesis of tin oxide, SnO2 nanoparticles.Ceramic International 35(8) (2009) 3375-3379.

[3] T. Krishnakumar, N. Pinna, K.P. Kumari, K.Perumal & R. Jayaprakash, Microwave-assisted synthesis and characterization of tin oxide nanoparticles. Materials Letters62(19) (2008) 3437-3440.

[4] N. Takahashi, Simple and rapid synthesis of MgO with nano-cube shape by means of adomestic microwave oven.Solid State Sciences9(8) (2007) 722-724.

[5] M. Batzill & U. Diebold. The surface and materials science of tin oxide.Progress in Surface Science 79(2-4) (2005) 47-154.

[6] N.A. Razana, 2007. Penyediaandanpencirianzarahnano SnO2dannikeltersokong

SnO2sertakajianaktivitipemangkinnyaterhadappenghidrogenanstirena.TesisSarjana:Universiti Sains Malaysia.

[7] A. Cirere, A. Vila, A. Cornet & J.R. Morante, Properties of nanocrystalline SnO2 obtained by means of a microwave process. Materials Letters and Engineering C 15(1-2) (2001) 203-305.

[8] G. Dai, X. Jiang & Y. Zhang, Excimer laser deposition and characteristics of tin oxide thin films. Thin Solid Films 320(2) (1998) 216-219.

[9] Jagriti & Chuhan. Investigation of structural and optical properties of tin oxide.Applied Science Innovations Private Limited, India (2009) 160-168.

[10] X.J. Wang, B. Dong, & Z. Zhou, Preparation and photoluminescence of high density SiOx

nanowires with Fe3O4 nanoparticles catalyst.Materials Letters 63(13-14) (2009) 1149-1152.

[11] H. Yuan & J. Xu, Preparation, characterization and photocatalytic activity of nanometer SnO2. International Journal of Chemical Engineering and Applications 1(3) (2010) 241-246.

[12] K. Murakami, K. Nakajima & S. Kaneko, Initial growth of SnO2 thin film on glass substrate deposited by the spray pyrolysis technique. Thin Solid Films 515(24) (2007) 8632-8636.

[13] Q. Yan, S. Tao & H.Toghiani, Optical fiber evanescent wave absorption spectrometry of nanocrystalline tin oxide thin films for selective hydrogen sensing in high temperatures gas samples. Talanta77(3) (2009) 953-961.

[14] Z. Othaman, K.B. Lim, S.Sakrani, & S. Muhammad, The stranski-krastanov three dimensional island growth prediction on finite size model. Jurnal Fizik UTM 3 (2008) 1-5.

[15] P.S. Raghupathi, J. George, & C.S. Menon, Effect of substrate temperature on the electrical and optical properties of respectively evaporated tin oxide thin films. Indian Journal of Pure & Applied Physics43 (2005) 620-623.

[16] S.S. Pan, C. Ye, X.M.Teng, L. Li, & G.H. Li, 2006. Localized exciton luminescence in nitrogen-incorporated SnO2 thin films. Applied Physics Letters 89 (2006) 291511(1)-291511(3).

[17] M.R. Hall, & P.H. Ribbe, An electron microprobe study of luminescence centers in cassiterite.The American Mineralogist 56 (1971) 31-45.

Advanced Materials Research Vol. 895 297

Solid State Science and Technology IV 10.4028/www.scientific.net/AMR.895 Synthesis and Characterization of SnO2 and Fe3O4 Composite Grown by Microwave Method 10.4028/www.scientific.net/AMR.895.291