Microsoft Word - 31-40 Physics | 31 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Effect Gamma Radiation of CdTe Thin Films Deposited by Thermal Evaporation Enase Y.Abid Dept. of Physics/College of Education For Pure Science(Ibn Al- Haitham)/University of Baghdad Received in :11/November/2015,Accepted in :1/March/2016 Abstract The effect of 0.66 µeV gamma radiation on the structural and optical properties of the CdTe thin films prepared by thermal evaporation at thickness 350nm, The samples were irradiated with time (50 h and 79h) at room temperature. The absorption spectra for all the samples were recorded using UV-VIS spectrometer in order to calculate the energy gap, refractive index and others parameter . The optical energy gap was found decrease from (1.9 to 1.67) eV. Key word: optical properties, gamma radiation, thin films, structural properties. Physics | 32 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Introduction Cadmium Telluride (CdTe) is a semiconductors, and Its II – VI group. CdTe band gap ≅ 1.54 eV for direct and high absorption coefficient (> 104 ), that means a direct band gap [1,2,3]. CdTe is more applicable such as solar cell material, electro – optical devices, radiation diodes (LEDs) and infrared optical window [2 -4]. Several deposition methods such as spray pyrolysis, electro deposition, sputtering and metal organic chemical vapor deposition[4-6]. The effect of irradiation on thin films improves the behavior of films, saluting the radiation incident the films represents a linear energy transmitted rat commensurate directly proportional to the square of the consignment and inversely with the square velocity [7]. Considered CdTe one of the most affected by the radiation, especially gamma ray at room temperature as its high averge atomic number, high resistivity, large band gap energy and good charge transport [3]. The aim of the paper is to study effect of different times of gamma ray on the optical and structural properties of the CdTe films. Experimental Thermal evaporation method was used to prepare the CdTe thin films Which deposited on the glass substrate, after cleaned with distilled water. Put powder CdTe in boot molybdenum on the distance 12 cm from the substrate at room temperature under pressure 3*10 -5 mbar . the films thickness was determined by using weight method from the equation: [3] ∆   ……………………..(1)  Where t is thickness, ∆ is different between the weight and the weight substrate before and after the film deposition, is density of the material deposition (gm/cm3) and A is substrate area film (cm2). All films had nearly (350 5) nm. A 137Cs radionuclide with activity 0.5 µm Ci was used for exposing the samples to gamma radiation (0.66 µeV) at room temperature. A set of irradiation doses was achieved by changing the exposure time (50 hour and 79 hour). CdTe crystalline structure pattern XRD was examined using SHMADZU XRD -6000 diffractometer. The absorption measurement was recorded using (UV-Visible 1800 spectra photometer) in the range of wave length (300 -1100) nm. Results and Discussion X-ray pattern of CdTe thin films exhibits polycrystalline nature and a major diffraction peak corresponds to (111) orientation, that the peak intensity increase with the increase in the film radiation time. The intensity of the (220) peak is extremely low  in comparison with the (111) peak, it is possible to think that, the gamma energy and time used are high enough to displace which transport atom in lattice[8]. Also this fig. (1) shows the increase in intensity with increase radiation time may be resulting from grain growth. The relation √ can used to clouted lattice parameter (a), where (d) is the atomic spacing value and , are the miller indices [9]. The grain size (F) for CdTe thin films is calculated using Scherrer,s formula [10, 11]: Ѳ …………………………….(2) Where the constant C is the constant ( 0.94), λ is the wavelength of X-ray (1.5406 A˚ for Cu Kα ), Ѳ is the Bragg,s angle and is the full width at half maximum. The dislocation density (δ) has been evaluated from Williamson and Smallmans formula [12]: ……………………………(3) Physics | 33 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 All these parameters given in table (1), where observed the grain size and dislocation density increase after radiation (at 50 h), but they decrease (at 75 h), due to the released defect in the lattice. The spectra of optical transmittance, as shown in figure (2) where the transmition is observed as a function of wave length within the range (400-1100)nm, decrease with increasing radiation time. That means increase of the crystalline of films. The optical band gap of samples could be described by equation [12, 15]: …………………………..(4) Where α is the absorption coefficient, D is constant, Eg is the energy gap and( h )is Planck ,s constant where is (1/2) allowed direct transition, and (m) is equal to 2 for allowed in direct transition. The term E in Eq. (4) represents the photon energy which can be calculated from the equation: [16] ………………………………..(5) Where h is the plank constant, ν is the incident photon frequency, and λ is the photon wavelength. Fig.(3) shows the value energy gap, where the energy gap value depends on the radiation dose where it decreases from (1.95eV) for unradiated CdTe thin flim to (1.67 eV) for irradiated film with time (79 h).،، This result may be explained on the basis of the high dose radiation to introduce energy levels in the forbidden gap which causes radical changes in the carries concentration .These new levels may be accepted at the top of the V.B or donor levels below the C. B, This in term decreases the energy required to transport the charge carrier required to transport the charge carries from the V. B to the C. B,, [2]. Fig. (4) shows the behavior of refractive index, where It was calculate by using the equation [17]: …………………………………….(6) Where R is reflectance and K is the extinction coefficient. and we can calculate ( n) of a semiconductor by using Herve – Vandamne relationship :[18] 1 ………………………………….(7) Where A and B are constants as A=13.6 eV and B= 3.4 eV. Fig. (4) shows the increasing in (n) value happened at highest radiation dose, indicated that the irradiated films become less transparent. See table (2). The extinction coefficient (K) was obtained from the relation: [19] ……………………………………………..(8) Fig.(5) shows the dependence of (K) on the wavelength with different times radiation. It is that the behavior of K increases with increasing time radiation. The real part of dialectric constant which represents the polarization (ε1) and imaginary part of dielectric constant (ε2) can be calculated from the equation: [20] …………………………………….(9) 2 ……………………………………………(10) The dependence of (ε1) and (ε2) on (λ) is shown in Figs. (6) and (7), it was concluded that the variation of (ε1) mainly depend on the value of (n2) because the smaller value of (K) compared with (n2), while the imaginary part of dielectric constant (ε2) mainly depends on (K) values which are related to the variation of (α). Physics | 34 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Conclusion CdTe thin films have been deposited by the thermal evaporation technique in the increase of the period of exposure to irradiation gamma. It was found that the optical properties were affected by the exposure to gamma radiation, such as optical energy gap values which showed an degrease as radiation dose was increased. From the result above, it can be used CdTe thin films in industrial application. Reference 1- Pattar, J.; Sanjeev, G. and Mahesh, H. M. (2013)“Effect of 100 µeV (7+) Oxygen ion irradiation on structural properties of Cadmium Telluride thin films” J. Thin film Sci. Tec., 2, 1, . (37-41). 2- Hussain, K.M.A.; Mahmood, Z.H.; Ishtiaque Syed, M.; Begum, T.; Faruqe, T. and Parvin, J. (2014) “Thermal vacuum deposition of cadmium telluride thin flims solar cell material” J. Materials Science and Application, 2, 9, (91-95) . 3-Suad, I. Issa,(2013) “Radiation Effect on optical & structural properties of CdTe:Zn thin films” J. Abn Al-Haitham Jour. Pure, 2 ,2 . 4-Nikale ,Y.M.;Shinde, S.S. and Rajpure, K.Y. (2011) “Physical properties of spray deposited CdTe thin films:PEC performance” J. Semiconductors, 32, 3, (1-7) . 5-Nowell, M.M; Paudel, N.R. and Liu, X . (2015) “Characterization of sputtered CdTe thin films Electon bactter diffraction and correlation with device performance” J. Microsc Microanal, 21, 4, (27-35) . 6- Neretina, S. and Sochnskll, N.V. (2006) “Optical and Micro structural characterization of the effects of rapid thermal annealing of CdTe thin films grown on Si (100) substrates” J. Electronic Materials, 34, 6 . 7- Laitta, S.;Sathyamoorthy, R.; Senthilamsu, S.;Subbarayan, A. and Natarajan, K. (2004) “Characterization of CdTe thin film – dependence of structural and optical properties on temperature and thickness” J. Solar energy materials & Solar cell, 82, (187-199) . 8- Rigana Bagam, M.; Madhusdhans Rao, N.; Kaleemulla, S.; Shobana, M.; Saikrishna, N. and Kuppan, M. (2013) “Effect of substrate Temperature on structural and optical properties of nanocrystalline CdTe thin films Deposited by Electron Beem Evaporation” J. Nano – and Electronic physics, 5, 3 (1-4) . 9- Lalitha, S. ; Kara Zhanoy, S. Zh.; Ravindran,P.; Senthilaran, S.; Sathyamoorthy, R. and Janabergenov, J. (2010) “Electronic Structural, Structural and optical properties of thermally evaporated CdTe thin films” J. Tamilnadu India, 61,(1-9) . ، 3، 15) "تاثير التعرض لجسيمات الفا لغشاء الرقيق " مجلة جامعة النهرين للعلوم، 2012اسماء ( ,احمد عزيز -10 )27 -31،( 11- Rana, M. Yas (2012) “Gamma radiation induced changes in the optical properties of CdTe thin films for dosimetric purposes” J. Iraqi of Phyices, 10, 17, (71-76) . 12- Ajeel, H.;Mohammed Hussein, Z. T.;Thajeel, K. M. and Hussein, R. Mekkilf, (2013) “Effect of gamma Radiation on Optical and Structural properties of Cadmium Telluride Thin films” J. Eng. & Tech. , 32, 4, (811-818). 13-Ubale, A. and Karni, D. (2006) “Studies of size dependent properties of cadmium telluride thin films deposited by using successive ionic layer adsorption and reaction method” J. Pure and Applied physics, 44, (254 – 259). 14- Nikale, V.M.; Shinde, S.S. ; Bhosale,C.H. and Rajpure, K.Y. (2011) “Physical properties of spray deposited CdTe thin films PEC performance” J. Semiconductor, 32, 3, (1-7) . ) "دراسة تأثير التشعيع بالليزر في 2009( احمد ,عدنان رعد مرعي, محمد عدنان و عيادة السامرائي ,عبد المجيد ، -15 ،. 2، 14بعض الخواص البصرية البصرية لغشاء الرقيق" مجلة تكريت للعلوم الصرفة، 16- Abdullal, M. H.; Jaseen, R.A. and Resan ,A. H. (2011) “Annealing effect on the optical energy gap of (CdTe) thin films” J. Pure Sciences, 7, 3, (205-213). Physics | 35 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 17- Abdulah, R.A.; Saeed, N.M.; Al Khalid, H. Kh. and Ra Zooqi, M. A. (2013) “Dispersion Parameters of Thin Cadmium Telluride films at different thicknesess” J. Scientific Research, 2, 3, (368-370) . 18- Singh, J. (2006) “Optical properties of condensed Matter and Application” Book. 19- Matt, M. H.; Chickmagalur, N.;Patel, R. and Jeetee dva Sh. (2014) “Thickness Dependent optical parameters of vacumm Evaporated Cadmium Telluride Thin films” J. Research Article, 5, (1-8). 20- Al-Douri, A.A.; Al-shakily, F. Y.; Alia, M. F and Alnajjar, A. A. (2010) “Optical properties Al and Sb Doped CdTe Thin flims” J. Advances in Condensed Matter Physics, 10, (1-5) . Table (1) Structural parameters of CdTe thin films before and after radiation. radiation time (hour) 2Ѳ degree Spacing (d) A˚ FWHM deg . hkl Lattice constant (a) A˚ Grain size (F) nm Dislocation (δ) Lines/cm2 0 39.2997 23.7695 2.29071 3.74034 0.15140 0.16800 111 220 6.47846 6.4769 50.1 52.7 3.9713 3.261 50 23.6822 39.2781 3.75393 2.29192 0.2228 0.2275 111 220 6.5019 6.4770 49.7 51.8 4.0338 3.72 79 23.7582 39.3113 3.75668 2.29422 0.18820 0.22000 111 220 6.5067 6.4890 59.4 54.5 2.833 3.36 Table (2) Optical energy gap and reactive index of CdTe thin films before and after radiation. radiation time (hour) n eq. 7 Eg (eV) 0 2.75 1.95 50 2.79 1.80 79 2.68 1.67 Physics | 36 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Figure.(1) X- ray diffraction of CdTe thin films at different radiation time. Physics | 37 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Figure.(2) Transmittance of CdTe thin films at different tradition time. Figure. (3) Energy gap of CdTe thin films at different tradition time. Physics | 38 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Figure. (4) Refractive index of CdTe thin films at different tradition time. Figure.(5) Extinction coefficient of cd te thin films at different tradition time Figure. (6) Real dielectric constant of CdTe thin films at different tradition time. Physics | 39 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 Figure. (7) Imaginary dielectric constant of CdTe thin films at different tradition time. Physics | 40 2016) عام 2(العدد 29المجلد مجلة إبن الهيثم للعلوم الصرفة و التطبيقية Ibn Al-Haitham J. for Pure & Appl. Sci. Vol.29 (2) 2016 تأثير اشعة كاما في اغشية كادميوم تالورايد المرسبة بطريقة التبخير الحراري ايناس ياسين عبد جامعة بغداد /للعلوم الصرفة (ابن الهيثم) /كلية التربية قسم الفيزياء 2016/اذار/1،قبل في :2015/تشرين الثاني/11استلم في : الخالصة   eVµتم دراسة تأثير اشعة كاما بطاقة المحضرة بطريقة التبخير الحراري CdTeفي الخواص البصرية ألغشية 0.66 ) ساعة بدرجة حرارة الغرفة. سجل طيف االمتصاصية لجميع 79، 50,شععت العينات بزمنين ( 350nmباستعمال ة ، معامل االنكسار وبعض العوامل األخرى، ووجد أن لحساب فجوة الطاقة البصري UV-VISالنماذج باستعمال مطياف . eV) 1.6إلى 1.9فجوة الطاقة البصرية تقل من ( الخواص البصرية ، أشعة كاما، األغشية الرقيقة، الخواص التركيبية. - الكلمات المفتاحية :