Optical Properties of Obliquely Evaporated Manganese Films Salam A.R. Ibrahim Ra'ad Saied Al-Rawie Ibrahim R. Agool Dept. of Physics / Collage of Science / University of Al-Mustansiriyah Received in : 9 October2012,Accepted in : 5May2013 Abstract The Manganese (Mn) thin films of obliquely and normal deposited were prepared by using thermal evaporation method at pressure 10-5 torr on glass substrate at room temperature. The optical properties of normal and obliquely deposited films are studied and also the effect of deposition angle on these properties. The deposition angle has great influence on the increase of the absorbance, absorption coefficient, extinction coefficient and imaginary dielectric constant and the decrease of the transmittance, reflectance, refractive index and real dielectric constant. Keywords: thin films, oblique deposition, self shadowing effect 129 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 Introduction The oblique deposition angle is an advanced physical vapor deposition technique which is used to fabricate high functional thin films with engineerable columnar morphology [1].The morphologies resulting from this method of vapor deposition have been noted and studied for their unique anisotropic mechanical, optical and electrical properties [2]. Films produced by this method of deposition exhibit a columnar microstructure consists of network of low density material that surrounds an array of parallel rode-shaped or columnar regions of high density [3].In common oblique deposition angle system, a uniform deposition flux is obtained by evaporation techniques such as thermal evaporation, sputtering, electron –beam evaporation and laser beam ablation. The deposition flux approaches a stationary substrate at angle θ (with respect to the substrate normal) [4].This method is a sophisticated technique to fabricate engineered nanostructure thin films for next generation nanodevices [5].The oblique deposited films have various applications such as optical radiation plates, circular polarization filters, wide band antireflection coatings, broadband high reflectors, three dimensional photonic crystals, photonic and biomedical devices and micro sensors [6]. Experimental Work Pure Manganese powder (99.99%) is used .The Mn thin films were prepared by thermal evaporation method using high vacuum system (Edward Speedvac Unit E306 ), were placed into molybdenum boat and evaporated by resistive heating on glass substrate which has dimensions (1.25x1) cm2 with varying angles of deposition. The transmittance and absorbance spectra of Mn films is taken at room temperature for wavelength range (300- 900)nm by using the UV-Visible recording spectrometer (UV-1650PC) made by Philips, The thickness of the films is (90 nm) which is measured by weight method by using the following equation[7] (where the thickness is kept constant with varying deposition angle): t=(m/2πρr2) cosθ -----------------------------(1) Where: t : thickness of the film . ρ : density of the material that will be evaporate. r : distance between boat and substrate. θ : deposition angle. The absorption coefficient is calculated by using the equation [8]: α= (2.303 A) / t ---------------------(2) Where: α: is the absorption coefficient. A: is the absorbance of the film. t: is the thickness of the film. The extinction coefficient is calculated by using the equation [9]: Ko = αλ / 4π --------------------(3) The real and imaginary dielectric constant are calculated by using the following relations [10]: Ԑ1= (n2-K ̥2) --------------------(4) Ԑ2 = ( 2 n Ko) --------------------(5) 130 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 Results and Discussion Figure (1) shows the XRD of Mn thin film deposited at θ=0 ̊, the deposition rate was 15 A ̊/sec (the substrates are perpendicular to the direction of vapor beam) and thickness 90 nm, The film exhibits a polycrystalline nature having (330), (332) and (510) planes with respect to 2θβ = (43.04 ̊), (47.71 ̊) and (52.07 ̊) and this agrees with (ASTM)(file number 33-0887) as shown in table (1). Figure (2) shows the relation between transmittance and wavelength for different deposition angles. The transmittance is low for wavelength range (300-590) nm and it increases slowly for wavelength range (590-900) nm. It is noticed that the transmittance of the films is decreased with the increase of deposition angle. The formation of columns and voids in obliquely deposited films increases the ability to trap the incident rays and this will increase the absorbance and decrease the transmittance [11]. Figure (3) shows the relation between the absorbance and wavelength for different deposition angles. The absorbance is high for wavelength range (300-590) nm and it decreases slowly for wavelength range (590-900) nm, it is noticed that the absorbance is increased with the increase of deposition angle and also there is a shift in absorbance toward long wavelengths with the increase of deposition angle. The increase in absorbance in these films can be explained on the basis of "self-shadowing effect", it is postulated that in the initial stages of film formation a random distribution of small crystallite acts as a nucleus for further growth, thus the region behind the crystallite is prevented from receiving material vapor because this region is in the shadow of the crystallite. Therefore the crystallite grows into a column, the area behind it is left vacant as far as its shadow extends[3]. Figure (4) shows the relation between absorption coefficient and photon energy with different deposition angles. We notice that the absorption coefficient increases with the increase of deposition angle. This increasing in absorption coefficient is because its value is proportional to the value of absorbance. The physical significance of (KO) is best expressed by the fact that the intensity falls to (1/e4πko) of its initial value in going the distance through the medium. The extinction coefficient (Ko) is directly related to the absorption of light, figure (5) shows the relation between extinction coefficient and wavelength with different deposition angles. We notice that the extinction coefficient value increases with the increase of deposition angle for all wave lengths and this agrees with Shishoda[12]. The extinction coefficient is related with absorption coefficient value which can be seen in equation (3). The complex dielectric constant (ε) consists of real dielectric constant (ε1) and imaginary dielectric constant (ε2) where real part (ε1) is the normal dielectric constant and imaginary part (ε2) represents the absorption associated with free carriers[13]. Figure (6) shows the relation between (ε1) and wavelength with different deposition angles, we notice that the real dielectric constant decreases with the increase of deposition angle for all wavelengths and this can be cleared from equation (4) where is the value of real dielectric constant is inversely proportional to the value of extinction coefficient. Figure (7) shows the relation between imaginary dielectric constant and wavelength with different deposition angles, the imaginary dielectric constant increases with the increase of deposition angle for all wavelengths, the increase of imaginary dielectric constant is related to the increase of extinction coefficient which increases with the increase of deposition angle. Conclusion From this work, we notice the great effect of deposition angle on the optical properties of Mn films, where the absorbance, absorption coefficient, extinction coefficient and imaginary dielectric constant are increased by the increase of the deposition angle, while the 131 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 transmittance and real dielectric constant are decreased. The increase of absorbance will help us to fabricate efficient detectors with wide spectral range of detection in the studied spectrum. By changing deposition angle, we can control the properties of the material without using other methods to control these properties such as doping or thickness changing which are economical costs us more than our method. Reference 1. Sobahan,K.M.A. and Hwangbo,C.K. (2010), Optical Properties of TiO2 Zigzag Films Prepared by Using Oblique Angle Deposition, The Korean Physics Society, 56,4,(1378). 2. Paterson,M.J and Cocks,F.H. (1979), Selenium and Tellurium Selective Absorber Coatings Produced by an Obliquely Vacuum Deposited Technique, Solar Energy,24, (249). 3. Dirks,A.G. and Leamy,H.J. (1972), Columnar Microstructure in Vapor-Deposited Thin Films, Thin Solid Films,47,219,(1977). 4. Karabacak,T.;Picu,R.C and Wang,G.C. (2005) Uniform Si Nanostructures Grown by Oblique Angle Deposition with Swing Rotation, Nanotechnology,16,9,(161717). 5. Kim,J.J. and Shin,Y.S. (2010) Nanostructured Optical Thin Films Fabricated by Oblique Deposition Angle, Advanced Natural Science: Nanoscience and Nanotechnology,1, (45005). 6. Polo,J.A. (2010), Multiple Surface-Plasmon-Polartion at a Single bi-material Interface, Journal of Nanophotonics,4,(40303). 7. Al-Rawie,R.S.A. (2002),Finding an Equation to Calculate the Thickness of Obliquely Deposited Film Prepared by Thermal Vacuum Evaporation Technique, Journal of Collage of Education, Al-Mustansiriyah University,5,(151). 8. Bass,M.; Van Stryland,E.W.; Williams,D.R. and Wolfe,W.L. (1995) Hand Book of Optics vol. 2 : Devices, Measurements and Properties, 2nd Edition, Mc.Graw-Hill, New York. 9. Sze,S.M. and .Kwong,K.Ng.(2007), Physics of semiconductor devices, 3d Edition, John Wiley and sons Inc. New Jersy. 10. Dressel,M. and Gruner,G. (2003), Electrodynamics of Solids: Optical Properties of Electrons in Matter, Cambridge University Press, New York . 11. Singh,M. and Vijay,Y.K.(2005) Variation of Optical Band Gap in Obliquely Deposited Selenium Films, Indian.Jour.of Pure and Appl.Phys.,43,(129). 12. Shishoda,P.P. and Mehra,R.M. (2001), Effect of Obliquely Deposition on Optical and Ellectrical Properties of As2Se3 and As2S3, Journal of Optoelectric and Advanced Materials,2,3,(319). 13. Klingshirn,C.F (1997), Semiconductor Optics, Springer Verlag, Berlin. Table No. (1): Comparison between 2θβ of XRD and 2θβ of (ASTM) (h k l) 2θβ (XRD) 2θβ (ASTM) (330) 43.04 ̊ 43.01 ̊ (332) 47.71 ̊ 47.68 ̊ (510) 52.07 ̊ 52.10 ̊ 132 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 Figure No.(1) : XRD of Mn film deposited at θ=0 ̊ Figure No.(2) Relation between transmittance and wavelength with different deposition angles Figure No.(3): Relation between Absorbance and wavelength with different deposition angles 0 2 4 6 8 10 12 14 16 18 20 0 100 200 300 400 500 600 700 800 900 1000 Tr an sm it ta nc e (T % ) wavelength (nm) θ=0 ̊ θ=40 ̊ θ=70 ̊ 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 200 300 400 500 600 700 800 900 1000 A bs or pt iv it y (A ) wavelength (nm) θ=0 ̊ θ=40 ̊ θ=70 ̊ Figure No.(4): Relation between absorption coefficient and photon energy with different deposition angles Figure No.(5) Relation between Extinction Coefficient and wavelength with Different deposition angles Figure No.(6): Relation between Real Dielectric constant and wavelength with different deposition angles 0.00E+00 4.00E+04 8.00E+04 1.20E+05 1.60E+05 2.00E+05 1.33 1.83 2.33 2.83 3.33 3.83 4.33 ab so rp ti on c oe ff ic ie nt (c m -1 ) photon energy (eV) θ=0 ̊ θ=40 ̊ θ=70 ̊ 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 100 200 300 400 500 600 700 800 900 1000 Ex ti nc ti on C oe ff ic ie nt wavelength (nm) θ=0 ̊ θ= 40 ̊ θ 70 ̊ 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 100 200 300 400 500 600 700 800 900 1000 R ea l D ie le ct ri c Co ns ta nt wavelength (nm) θ=0 ̊ θ=40 ̊ θ=70 ̊ 134 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 Figure No.(7): Relation between Imaginary Dielectric constant and wavelength with different deposition angles 0 1 2 3 4 5 6 200 300 400 500 600 700 800 900 1000 Im ag in ar y D ie le ct ri c Co ns ta nt wavelength (nm) θ=0 ̊ θ=40 ̊ θ=70 ̊ 135 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 المرسبة بشكل مائل )(Mnالمنغنیزالخصائص البصریة ألغشیة سالم عبد الرزاق ابراھیم رعد سعید الراوي ابراھیم رمضان عاكول الجامعة المستنصریة / كلیة العلوم قسم الفیزیاء/ 2013ایار 5قبل البحث في ، 2012تشرین االول 9 استلم البحث في : الخالصة في ھذا البحث حضرت أغشیة المنغنیز بشكل عمودي ومائل بطریقة التبخیر الحراري على قواعد زجاجیة وفي درجة حرارة الغرفة. وتمت دراسة الخصائص البصریة لھذه األغشیة وتأثیر زاویة الترسیب في ھذه الخصائص. ان زاویة ذ أزدادت كل من األمتصاصیة ومعامل األمتصاص ومعامل الترسیب لھا تأثیر كبیر في الخصائص البصریة لألغشیة، ا الخمود والجزء الخیالي من ثابت العزل الكھربائي مع زیادة زاویة الترسیب، في حین تقل كل من النفاذیة واألنعكاسیة ومعامل األنكسار والجزء الحقیقي من ثابت العزل الكھربائي مع زیادة زاویة الترسیب. ، تأثیر التظلیل الذاتي الترسیب المائل ، الكلمات المفتاحیة: أغشیة رقیقة 136 | Physics @a@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ÚÓ‘Ój�n€a@Î@Úœäñ€a@‚Ï‹»‹€@·rÓ:a@Âig@Ú‹©@Ü‹126@@ÖÜ»€a@I3@‚b«@H2013 Ibn Al-Haitham Jour. for Pure & Appl. Sci. Vol. 26 (3) 2013 Optical Properties of Obliquely Evaporated Manganese Films Received in : 9 October2012,Accepted in : 5May2013 Abstract Ԑ2 = ( 2 n Ko) --------------------(5) Results and Discussion Figure (1) shows the XRD of Mn thin film deposited at θ=0 ̊, the deposition rate was 15 A ̊/sec (the substrates are perpendicular to the direction of vapor beam) and thickness 90 nm, The film exhibits a polycrystalline nature having (330), (33... Figure (2) shows the relation between transmittance and wavelength for different deposition angles. The transmittance is low for wavelength range (300-590) nm and it increases slowly for wavelength range (590-900) nm. It is noticed that the trans... Figure (3) shows the relation between the absorbance and wavelength for different deposition angles. The absorbance is high for wavelength range (300-590) nm and it decreases slowly for wavelength range (590-900) nm, it is noticed that the absor... We notice that the absorption coefficient increases with the increase of deposition angle. This increasing in absorption coefficient is because its value is proportional to the value of absorbance. الخصائص البصرية لأغشية المنغنيزMn)) المرسبة بشكل مائل سلام عبد الرزاق ابراهيم رعد سعيد الراوي ابراهيم رمضان عاكول قسم الفيزياء/ كلية العلوم / الجامعة المستنصرية استلم البحث في : 9 تشرين الاول 2012 , قبل البحث في 5 ايار 2013 الكلمات المفتاحية: أغشية رقيقة ، الترسيب المائل ، تأثير التظليل الذاتي