Preparing of Copper Oxides Thin Films by Chemical Bath Deposition (CBD) for Using in Environmental Application

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ScienceDirect Energy Procedia 74 (2015) 1459 – 1465

International Conference on Technologies and Materials for Renewable Energy, Environment and Sustainability, TMREES15

Preparing of Copper Oxides Thin Films by Chemical Bath Deposition (CBD) for Using in Environmental Application NASSERa *. Saadaldin, Alsloum M.Na, Hussain Nb* AL-Baath University, Homs P.O Box 77, Syria Damascus University, Damascus P.O Box 30621, Syria

Abstract Thin films of copper oxide were prepared by chemical bath deposition (CBD) method on substrates of glasses by Alternate immersions method (AI) at room temperature for 20 second using heated liquid of sodium hydroxide up to 70ஈ and copper thiosulfate complex. The substrates were annealed at different temperatures (200-300-400) in the air; the crystalline structure of prepared samples was studied by using XRD and (SEM) technologies. The results were indicated to; the crystalline structure of prepared films was related to temperature of annealing of copper-oxide (Tenorite), cubic of Cu2o (Cuprite). Optical studies showed that the prohibited rang between (1.3-2.4)ev was related to annealing temperature (monoclinic). Therefore, application of solar cells is very promising as a suitable material for conversion of photovoltaic energy with high absorbency solar and low thermal issue. Real and imaginary dielectric constants were calculated (‫ܭ‬1 and ‫ܭ‬2). Significant improvement in structure as a follower of annealing temperature required by oxide layer, SEM image showed that porous structure were distinctive materials for the manufacture of gas sensors. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

© 2015 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review underresponsibility responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD). Peer-review under of the Euro-Mediterranean Institute for Sustainable Development (EUMISD) Keywords: Copper oxide; CBD method; Real and imaginary dielectric constants

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: [email protected]

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4 .0/). Peer-review under responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD) doi:10.1016/j.egypro.2015.07.794

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Nomenclature CBD

Chemical bath deposition

SEM

Scanning electron microscope

1 Introduction Copper oxide tenorite (CuO) is one of the important semiconductors, advantageous materials and has been studied for photovoltaic applications, Could be obtained by the oxidation of copper and has a monoclinic-crystal structure as a characteristic. Furthermore, Copper Oxide is p-type semiconductor (most of Charge carriers are holes) and has a prohibited area (1.4-2.4) ev [1]. Copper oxide has dark brown color and many applications about optical-thermal collectors of solar due to high efficiency [2], good level of stability of CuO and high absorbency in visible wavelengths. Moreover, it considered perfect detector for big number of gases as active substance in the gas sensors, cheap economic substance and nontoxic [3]. Copper oxide films have been deposited using several techniques such as oxidation of copper sheets[4], electrodeposition [5], ultrasonic spray pyrolysis [6] and reactive sputtering [7]. Aim of the present study was prepare of thin films of copper oxide material using chemical bath deposition (sequent dipping) with perfect preparing conditions to prevention the optical structures of these films. Chemical bath deposition method (sequent dipping) was adopted by many researchers [13, 15], due to ease of preparation, capable of depositing a large-area film and lack of cost with normal atmospheric conditions. As well as, thin films were prepared with high- temperature fusion, and had prepared well homogeneous films [11]. 2 Experimental works 2.1 Preparation of chemical solutions Immersion solution was prepared by using complex solution of sodium sulfate (Na2S2O3) with molar concentration (1M), whereas 25-125 ml until a colorless solution was formed according the following chemical equation: Cu2+ + 4S2O2-3 ֞ 2[Cu (S2O3)]- + [S4O6]-2

(1)

Amount of distilled water were added to form 250 ml volume of the preview solution at room temperature, then 80 ml volume of sodium hydroxide (NaoH, 1ml) was prepared. These solutions were heated to 70ஈC, and then the substrates were dipped in the solution for 20 second to formation required thin films. 2.2 Interpretation of the formation mechanism of thin films Negative Hydroxide ions (OH-) were formatted as a result of the chemical interaction in the first dipping by NaoH solution and were deposited on substrate surface, the second dipping in 100 ml of record complex solution of copper ions, whereas copper ions format according following balanced reaction:[8] Cu (S2O3)]- ļ&X+ + S2O3-2

(2)

Copper oxide was formatted by (OH-) ions which were on the substrate surface according the following reaction [8]: + (3) 2Cu + 2OH ĺ&X2O + H2O Thin film of Cu2O was formed after many times of dipping. Increasing the number of times dipping performed to

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LQFUHDVHWKHWKLFNQHVVRIILOPVYDOXHRIILOPWKLFNQHVVZHUHȝPIRU30 times of request dipping) [8], after that the slides were washed by distilled water and left to dry, the slides were annealed for one hour by using oven at different temperature (200-300-400ஈC), many samples with different thicknesses and times of dipping were prepared, the best sample was chosen with special parameters (400ஈC and 20 times of dipping) [13] . 2.3 Determine the crystalline structure of the prepared films Spectra of x-ray diffraction on prepared samples were recorded and showed a multi- gelling structure of the prepared films and monoclinic type which corresponds with previous research [8, 9] according figures (1). The results showed a good correspondence when annealed sample of copper oxide was compared with referential card (JCPDS).

Fig.1. XRD diffraction spectra on prepared samples

2.4 study of optical structure The prepared samples at 400ஈC were investigated by using Spectrophotometer, absorbance curve showed high absorbance of the prepared film at short wavelengths, while less absorbance was at large wavelengths figure (2), whereas absorbance of materials is related with thickness of film, the wavelength of the incident ray, color and structure of the material [10]. The absorption coefficient “Į´ RI &X2 ILOP ZDV PHDVXUHG E\ IROORZLQJ HTXDWLRQ Į   $W ZKHUHDV A: Absorbance and t: thickness [11]. The relation between absorption coefficient and photon energy was clearly showed in figure 2, whereas, value of the absorption coefficient is growing slowly within the domain (1.2-2) ev, and then the value of absorption coefficient begin increased rapid. Absorption edge is not sharp, but in the form of curved, that means multi- gelling

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structure of prepared films was shown.[1, 8, 12]. Attributed absorption coefficient in this region due to the impurities or transitions within the band (BAND-BAND), these transitions could happen when the wavelength had incident photon energy less than energy of Prohibited area. The high values of the absorption coefficient of the absorption edge after showed that the probability of electronic transitions be large and are classified under the direct electronic transitions [10, 13]. 5x104

4x104

D cm-1)

3x104

2x104

1x104

0 0.5

1.0

1.5

2.0

2.5

3.0

3.5

hX(eV) Fig.2. $EVRUSWLRQFRHIILFLHQW³Į´RI&X2ILOPV

Energy of optical prohibited area of prepared samples at 400ஈC was calculated by using the following equation for direct transmission of both types of permitted and prohibited [8]. ĮKȣ %Kȣ-Eg)n

(4)

Whereas, B: constant depended on material structure, Eg: Energy of prohibited area, KȣSKRWRQHQHUJ\QYDOXH depended on WUDQVLWLRQVW\SHVQ ½ IRUDOORZHGGLUHFWWUDQVPLVVLRQQ 3/2for forbidden direct transmission

direct

(DhX)2 (eV/cm)2

8.0x1010

6.0x1010

4.0x1010

2.0x1010

0.0 0.5

1.0

1.5

2.0

hX(eV)

2.5

3.0

3.5

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5x103

indirect 3

(DhX)2/3 (eV/cm)2/3

4x10

3x103

2x103

1x103

0 0.5

1.0

1.5

2.0

2.5

3.0

3.5

hX(eV) Fig.3. (a) showed the relationship between ĮKX 2 and the photon energy , prohibited area energy of the film (2 ev) as is evident by the figure that ; (b) ): the relationship between (ĮKȣ Ҁand photon energy, the value of the energy gap (1.4 ev) for forbidden direct transmission.

2.5 Study of electric-optical properties Both of real and imaginary dielectric constants were calculated by following equations İ1 Q2 – k2

(5)

İ2 QN

Shown in Figure (4) real dielectric constant as a function of photon energy of prepared films values and showed that the real part of the dielectric constant values can be greater when the photon energy 1.7 ev, Then begins a downward thereafter.

7

6

5

H

4

3

2

1 0

1

2

3

4

5

6

hX(eV)

Fig.4. Real dielectric constant as a function of photon energy

7

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Shown in figure (5) the imaginary part of the dielectric constant as a function of photon energy of prepared films seems to be the imaginary part of the dielectric constant values can be greater when the photon energy 3.4 ev, Then begins a downward thereafter.

H

0.4

0.2

0.0 0

1

2

3

4

5

6

7

hX(eV)

Fig.5. the imaginary part of the dielectric constant as a function of photon energy

2.6 Study the microstructure of prepared samples The prepared samples were taken by SEM system and showed that density of the granular were in crystal balls form and very small, while the crystalline spaces were less, this lack can be attributed to changing in the crystalline case of Cu2O structure to Cu O [12, 14].whereas, the chemistry of the precursor solutions have been big effect substantially on the microstructures of the films [16].

Fig.6. SEM images of CuO film

3. Conclusion Perfect thin films of copper oxide material were prepared by using copper sulphate and solution of sodium sulphate with sodium hydroxide as the X-ray measure showed at perfect preparing conditions for a high degree of uniformity and adhesion on the substrate. The permitted and prohibited electronic transitions were directly.

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Increase value the real dielectric constant of the material leads to increase susceptibility of the material of polarization Porous structure images of samples were shown by using morphology study by electron microscope (SEM). Furthermore, the control on crystalline grains size and blanks was by changing of temperature, thus, use efficiently copper oxide for sensors gas industry. References [1] Chuhan D, S.V., Dass S, Shrivastav R, Preparation and characterization of nanostructured CuO thin films for photoelectrochemical splitting of water. Indian Academy of Sciences, 2006. 29: p. 709–716. [2] J, S., Thin zinc oxide and cuprous oxide films for photovoltaic applications. 2010, MINNESOTA. p. 5-6. [3] S, Zaman., Synthesis of ZnO, CuO and their Composite Nanostructures for Optoelectronics, Sensing and Catalytic Applications, in Science and Technology. 2012, Linköping University: LiU-Tryck, Linköping. p. 8-9. [4] Li, T.T., et al., Electrochemical Water Oxidation by In Situ-Generated Copper Oxide Film from [Cu(TEOA)(HO)][SO] Complex. Inorg Chem, 2015. [5] Gerein, N.J. and J.A. Haber, Effect of ac electrodeposition conditions on the growth of high aspect ratio copper nanowires in porous aluminum oxide templates. J Phys Chem B, 2005. 109(37): p. 17372-85. [6] Hahn, N.T., et al., Spray pyrolysis deposition and photoelectrochemical properties of n-type BiOI nanoplatelet thin films. ACS Nano, 2012. 6(9): p. 7712-22. [7] Cho, T.S., H. Choi, and J. Kim, Fabrication of porous noble metal thin-film electrode by reactive magnetron sputtering. J Nanosci Nanotechnol, 2013. 13(6): p. 4265-70. [8] Mammah SL, O.F., Omubo-Pepple VB, Ntibi JE, Ezugwu SCh, Ezema FL, Annealing effect on the optical and solid state properties of cupric oxide thin films deposited using the Aqueous Chemical Growth (ACG) method. Natural Science, 2013. 5: p. 389-399. [9] Raut, N.C., et al., Structural and morphological characterization of TiO2 thin films synthesized by spray pyrolysis technique. J Nanosci Nanotechnol, 2009. 9(9): p. 5298-302. [10] Yongliang H., Structural, Optical and Electrical Properties of Cu-In-O Thin Films Prepared by Plasma-Enhanced CVD, in Material Science. 2007, National Unversity of Singapore. p. 9-12. [11] Chen, S.H., H.W. Wang, and T.W. Chang, Absorption coefficient modeling of microcrystalline silicon thin film using Maxwell-Garnett effective medium theory. Opt Express, 2012. 20 Suppl 2: p. A197-204. [12] Zainelabdin. A, Z.S., Amin. G, Nur. O, Willander. M, Optical and current transport properties of CuO/ZnO nanocoral p-n heterostructure hydrothermally synthesized at low temperature. Materials Science & Processing, 2012. 108: p. 921-928. [13] Zhou, B., et al., Fabrication and photoelectrocatalytic properties of nanocrystalline monoclinic BiVO4 thin-film electrode. J Environ Sci (China), 2011. 23(1): p. 151-9. [14] Gondoni, P., et al., Structure-dependent optical and electrical transport properties of nanostructured Al-doped ZnO. Nanotechnology, 2012. 23(36): p. 365706. [15] Saravanakannan. V , R.T., Structural, Electrical and Optical Characterization of Cuo Thin Films Prepared by Spray Pyrolysis Technique. ChemTech Research, 2014. 6: p. 306-310. [16] $<2UD(00+$VODQF(%DúDUDQFThe preparation of copper(II) oxide thin films and the study of their microstructures and optical properties. Materials Chemistry and Physics, 2004. 83(1): p. 140–144.