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Studies on Thin Film Multilayer Coatings Deposited using Sputtering Process
Available online at www.sciencedirect.com
ScienceDirect www.materialstoday.com/proceedings Materials Today: Proceedings 5 (2018) 2994–2999
ICAMA 2016
Studies on Thin Film Multilayer Coatings Deposited using Sputtering Process Muralidhar Singh Ma, Vijaya Gb, Krupashankara M Sb, B K Sridharaa, T N Shridharab* a
Department of Mechanical Engineering, National Institute of Engineering, Mysuru - 570008, India b Department of Mechanical Engineering, R.V.College of Engineering, Bengaluru - 560059, India
Abstract Multilayer coatings have been modelled and prepared experimentally for optical and mechanical properties for solar reflector applications on ceramic substrate. Aluminium thin films are ideally suited for reflector. This value of reflection is reduced reasonably by integrating multilayer thin films based on dielectric materials, behaving as bond and protective layer, aluminium thin films in combination with alumina coatings are also suitable for solar reflector coatings, aluminium thin films were coated on ceramic substrate using DC magnetron sputtering process in argon atmosphere. The effect of thickness of bond layer and protective layers on aluminium coatings of 400nm are characterized for optical and mechanical and properties has been presented in this paper. Multilayer coatings deposited with substrate temperature at RT with coating thickness of (100nm) Al2O3 as bond layer and protective layer as lower surface roughness (Ra<6nm) compared to the coating deposited with coating thickness of (300nm) Al2O3 with aluminium as reflective layer, as a result the coating had a hardness of 7 GPa, while that of pure aluminium deposited at RT with coating thickness of (100nm) Al2O3 as bond layer and protective layer had a hardness of 4.5 GPa. The simulation and experimental responses of multilayer of aluminium thin films deposited at in the wavelength range of 250-1500 nm were similar. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016). Keywords: Thin films; Sputtering; Aluminium; Hardness; Optical Simulation
* Muralidhar Singh M. Tel.: +91-9663875393 E-mail address: [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016).
Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
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1. Introduction High reflection coatings can be applied to the outside of a component, such as a flat piece of Ceramic, polymeric and metal to produce a first surface reflector. Metallic coatings are used primarily for reflectors and they do not relay on the principals of optical interference, but rather on the physical and optical properties of the coating material. However, metallic coatings are often coated with thin ceramic films to increase reflectance over a desired range of wavelengths, these types of coatings called as enhanced metallic coatings [1]. Over coating metallic coatings with a hard, single, ceramic layer of half-wave optical thickness improves abrasion and tarnish resistance but marginally affects optical properties. Depending on ceramic material used, such over coated metals are referred to as durable, protected, or hard- coated metallic reflectors. Metal oxides are the preferred materials for fabrication of many optical coatings for the UV, visible and near infrared. Optical interference occurs in thins films with thicknesses of the order of the wavelength of light, and such coatings form the basis as building blocks for many multilayer optical coatings. Multilayer films with individual thicknesses of only a few nanometers can exhibit interesting optical and mechanical properties, features that can be exploited in the design and manufacture of precision optical coatings [2-5]. Therefore, recommendations of ceramic layer on aluminium reflector materials to use are made here based on the simulation results. However, a reflector coated with ceramic layer on aluminium thinfilm on a ceramic substrate shows promising stability of the optical properties for cost-effective in concentrating solar energy applications. The material under development offers promise as a commercially viable for solar reflector materials. In case of solar reflector coatings, it is critical for the aluminium thin films to reflect as much of the incident solar energy as possible which implies that the reflectance should be maximum across the whole of the solar spectrum. Thin films used for such applications where heat transfer is of prime importance, the added requirements are stability at high temperature and minimizing radiation in the thermal infrared band. Thus there are complex set of requirements of strong reflection [6]. In the present work, Aluminium thin films with thickness of 400 nm were modeled and simulated with Al2O3 as bond layers and protective layers on ceramic substrate for solar reflectors application. Reflectors with thin film coated aluminium does not withstand outdoor ageing ,The initial total and specular solar reflectance of aluminium thin film is 96 %, The fast degradation of the specular reflectance of aluminium thin film will decreased unless it is protected by ceramic coatings. Simulation study was carried out to find best combination of material among adhesion layer, and each of the protective layers on aluminium reflective layer and to maximize reflection. We have carried out modeling and simulation of multilayer system with aluminum as a reflective layer by varying protective layer material and its thickness as model shown in Fig. 1. It is significant to improve the efficiency of solar reflector systems which will strongly depend on the optical properties of solar reflective materials and multi-layer structure [7-12]. Protective Layer Metal High Reflective Layer Bond Layer Ceramic Substrate Fig.1. Schematic of Multilayer Design of Reflective Coating
2. Experimental The thin film Aluminium Coatings were deposited on ceramic substrates using DC Magnetron sputtering process and Al2O3 using RF power supply as bond layer and protective layer. Desired substrates with a dimension 30mm x 30mm are used for deposition and substrates are cleaned by a solvent clean followed by de ionized water rinse, followed by mild acid clean, DI rinse and blow dry, Fig. 2 shows the schematic diagram of the sputtering chamber
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Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
All the coating processes are carried out in vacuum chamber at a base pressure of 1 x 10-5 mba using argon gas (99.999%), deposition of Aluminium (99.95%) were performed at 2000w by using DC power supply and Al2O3 at 1200w by using RF power supply. The deposition chamber was filled with pure argon gas with a flow rate of 500sccm for target cleaning; pre sputtering process was carried out with shutter positioned over the target there by shielding the flow of plasma towards the substrate for about 5 minutes. The deposition parameters maintained during the process are tabulated in Table 1. All depositions were performed at a fixed substrate to source distance of 270mm with a substrate rotation at a rate of 2rpm. modelling and simulation was carried out using CODE software Optical reflection measurements on the films were carried out using UV-VIS-NIR spectrophotometer (Model Lambda 750) with the wavelength ranging between 250-2500nm.Film thickness measurements were carried out using DEKTAK 6M surface profiler, surface topography and mechanical properties of the films were carried out using Hysitron TI 750L Nano Mechanical System.
Fig.2. Schematic of the Magnetron Sputtering Setup Table 1 Sputtering parameters for multilayer thin film deposition Process Parameters Sputtering Gas Argon flow rate (sccm) Power supply Sputtering Power (w) Temperature Substrate Multilayer (ML1) Multilayer (ML2) Multilayer (ML3) Base Pressure (torr) Targets
Values Argon 500 DC, RF 2000 &1200 RT Ceramic Al2O3 (100)+Al (400)+ Al2O3 (100) Al2O3 (200)+Al (400)+ Al2O3 (200) Al2O3 (300)+Al (400)+ Al2O3 (300) 1 x 10-5 Aluminum, Al2O3
3. Results and Discussions The simulation and experimental deposition was carried out by varying Al2O3 thickness, and percentage (%) of reflection was plotted against the wavelength is as shown in Fig. 3 (a) and solar Reflectance plotted as shown in the Fig. 3 (b). In general, metals have very high extinction coefficients, making them good reflectors, From the Fig. 3 (a) and 4(b) it clearly seen that there is a limit for the reflection of aluminum thin film that is around 96% which is called as reflectivity of the aluminum thin film and even after increase in the thickness of aluminum thin film there is no variation (in simulation it is around 100-300nm but in practical it depends on the process and microstructure of the deposited film). With respect to change in the thickness of Al2O3 that is from 100 to 300nm, the reflectance increases from 92 to 96 because of shift in the antireflection part, Table 2. Optical reflectance of aluminium films deposited on ceramic substrate.
Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
a
2997
b 100
100 90 80 70 60 50 40 30 20 10 0
90 Reflection (%)
Reflection (%)
80 70 60 50 40 30 20 10 0
250
500
250
750 1000 1250 1500 1750 2000 2250 2500 Wavelength (nm) ML1 ML2 ML3
500
750
1000 1250 1500 1750 2000 2250 2500 Wavelength (nm) ML1
ML2
Ml3
Fig.3. Shows Reflectance spectra for Multilayer coatings on ceramic substrate (a) Simulation (b) Experimental Table 2 Optical reflectance of aluminium films deposited on ceramic substrate Coatings
Sample ID
Al2O3+Al+Al2O3
ML1 ML2 ML3
Experimental Reflectance (%) UV VIS NIR 57.87 70.02 92.79 61.24 73.39 96.16 64.96 74.92 96.40
Simulation Reflectance (%) UV VIS NIR 87.01 83.61 94.89 88.12 87.51 94.35 88.12 87.51 94.35
Fig. 5 shows the AFM images of the multilayer coatings. The surface roughness increased from Ra of 6 nm to 22nm as shown in table 4. Fig. 4 shows the nano indentation plots of magnetron sputter coated multilayer thin films on ceramic substare at room temperature. The hardness of the multilayer films coated at room temperature with 100nm Al2O3 as bond layer and protective layer (ML1) is ~4.67GPa, hardness of the multilayer films coated at room temperature with 200nm Al2O3 as bond layer and protective layer (ML2) is ~5.70GPa and hardness of the multilayer films coated at room temperature with 300nm Al2O3 as bond layer and protective layer (ML3) is ~6.83GPa due to the effect of surface roughness. The stiffness and modulus values of these films are given in Table 3. The stiffness and the modulus increased by 6 to 10%. 3000
Load (uN)
2500 2000 1500 1000 500 0 0
20
40
ML1
60 80 Depth (nm) ML2
100
120
140
ML3
Fig.4. Nano indentation test Multilayer thin films on ceramic substrates at a maximum load of 3000µN
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Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
Table 3 Nano indentation mechanical property of Multilayer thin films Coatings Al2O3+Al+Al2O3
Sample ID ML1 ML2 ML3
a
S(µN/nm) 81.86562 84.90836 88.41992
Er(GPa) 90.48077 93.75 96.88694
H(GPa) 4.666091 5.700542 6.836692
b
c
Fig.5. AFM images of Multilayer thin films on ceramic substrates (a) ML1 (100nm)Al2O3+(400nm) Al+(100nm) Al2O3, (b) ML2 (200nm)Al2O3+(400nm) Al+(200nm) Al2O3 and (b) ML3 (300nm)Al2O3+(400nm) Al+(300nm) Al2O3 Table 4 Roughness of aluminium films deposited on ceramic substrate Coatings Al2O3+Al+Al2O3
Sample ID ML1 ML2 ML3
Ra 6.46 17.11 22.99
RMS(Rq) 10.15 20.55 27.82
4. Conclusions Multilayer thin films on ceramic substrate results in formation of reflective layer with combination with aluminium and Al2O3 deposition using DC and RF magnetron sputter at room temperature, even though the sputter target is 4N pure aluminium and Al2O3, the as deposited aluminium thin film on the ceramic substrate could be a combination of Al2O3 as bond layer and protective layer with thickness ranging from 100-300nm. Since Aluminium is used as a reflective layer it needs to protect using oxide layer to enhance the life of the reflector, As a result the hardness of the film can also be increased and can go up from 4 to 7GPa. The surface roughness of the multilayer coatings deposited has finer for ML1 with 100nm of bond layer and protective layer with aluminium as reflective layer with thickness of 400nm is 6nm with increase in thickness of ML3 to 300nm of Al2O3 as bond later and protective layer the roughness as increased to 22nm deposited with substrates at room temperature The UV-VIS-NIR response of the multilayer coatings as a reflection ranging from 84 to 96% in visible and near IR region while it is reduced in ultraviolet region in the wavelength range of 250 to 2500 nm. The simulation data and the experimental results are similar in the wavelength range of 250-1500 nm, and beyond this value there is a deviation between simulation and experimental results because NIR response is sensitive to surface roughness and film stress. 5. Acknowledgements The authors would like to thank the Solar Energy Research Initiative (SERI) Department of Science and Technology, New Delhi, India for funding this research work. The authors gratefully acknowledge the support from management of R.V. College of Engineering, Bangalore, The National Institute of Engineering Mysuru, and Visveswaraya Technological University, Belagavi.
Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
References [1] Correa .G, Almanza .R, Martinez, Mazari M, Cheang J. C., Solar Energy Materials and Solar Cells, 52 (1998) 231-238. [2] Moralez, A. and Duran A., Journal of Sol-gel Science and Technology, 8 (1997) 51-457. [3] Rafael Almanza, Genaro Correra, Marcos Mazari, Genaro Correa, Solar Energy, 54 (1995) 333-343. [4] Le Paven-Thivet, C. Malibert, Ph. Houdy, P.A. Albouy ,Thin Solid Films, 336 (1998) 373-376. [5] Quintana P, Oliva A I, Ceh O and Corona, J. E, Aguilar M, Superficies y Vacío, 9 (1999) 282-282. [6] Y.G. Shen , Y.W. Mai, Material Science and Engineering A, 284 (2000) 176-183. [7] C. E. Kennedy , R.V. Smilgys, D. S. Kirkpatric, J. S. Ross, Thin Solid Films, 304 (1997) 303-309. [8] Thomas Fend, Bernhard Hoffschmidt, Gary Jorgensen, Harald Kuster, Riffelmann, Solar Energy, 74 (2003) 149–155. [9] Maria Brogrena, Anna Helgesson, Bjorn Karlsson, Johan Nilsson, Arne Roos, Solar Energy Materials & Solar Cells, 82 (2004) 387–412. [10] Maria Brogren, Bjorn Karlsson, Arne Roos, Anna Werner, Solar Energy Materials & Solar Cells, 82 (2004) 491–515. [11]Cremer R, Witthaut M, Neuschutz D, Erkens G, Leyendecker Feldheg M, Surface and Coatings Technology,120 (1999) 213-218. [12] Kirill Bordo and Horst-Gunter Rubahn, Material Science, 18 (2012) 313-317. [13] S. Shawki, S. Mikhail, Materials and Manufacturing Processes, 15 (2000) 737-746. [14]K. S. Ahn, Y. C. Nah and Y. E. Sung, Journal Vacuum Science Technology A, 20 (2002)1468–1474.
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ScienceDirect www.materialstoday.com/proceedings Materials Today: Proceedings 5 (2018) 2994–2999
ICAMA 2016
Studies on Thin Film Multilayer Coatings Deposited using Sputtering Process Muralidhar Singh Ma, Vijaya Gb, Krupashankara M Sb, B K Sridharaa, T N Shridharab* a
Department of Mechanical Engineering, National Institute of Engineering, Mysuru - 570008, India b Department of Mechanical Engineering, R.V.College of Engineering, Bengaluru - 560059, India
Abstract Multilayer coatings have been modelled and prepared experimentally for optical and mechanical properties for solar reflector applications on ceramic substrate. Aluminium thin films are ideally suited for reflector. This value of reflection is reduced reasonably by integrating multilayer thin films based on dielectric materials, behaving as bond and protective layer, aluminium thin films in combination with alumina coatings are also suitable for solar reflector coatings, aluminium thin films were coated on ceramic substrate using DC magnetron sputtering process in argon atmosphere. The effect of thickness of bond layer and protective layers on aluminium coatings of 400nm are characterized for optical and mechanical and properties has been presented in this paper. Multilayer coatings deposited with substrate temperature at RT with coating thickness of (100nm) Al2O3 as bond layer and protective layer as lower surface roughness (Ra<6nm) compared to the coating deposited with coating thickness of (300nm) Al2O3 with aluminium as reflective layer, as a result the coating had a hardness of 7 GPa, while that of pure aluminium deposited at RT with coating thickness of (100nm) Al2O3 as bond layer and protective layer had a hardness of 4.5 GPa. The simulation and experimental responses of multilayer of aluminium thin films deposited at in the wavelength range of 250-1500 nm were similar. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016). Keywords: Thin films; Sputtering; Aluminium; Hardness; Optical Simulation
* Muralidhar Singh M. Tel.: +91-9663875393 E-mail address: [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Advanced Materials and Applications (ICAMA 2016).
Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
2995
1. Introduction High reflection coatings can be applied to the outside of a component, such as a flat piece of Ceramic, polymeric and metal to produce a first surface reflector. Metallic coatings are used primarily for reflectors and they do not relay on the principals of optical interference, but rather on the physical and optical properties of the coating material. However, metallic coatings are often coated with thin ceramic films to increase reflectance over a desired range of wavelengths, these types of coatings called as enhanced metallic coatings [1]. Over coating metallic coatings with a hard, single, ceramic layer of half-wave optical thickness improves abrasion and tarnish resistance but marginally affects optical properties. Depending on ceramic material used, such over coated metals are referred to as durable, protected, or hard- coated metallic reflectors. Metal oxides are the preferred materials for fabrication of many optical coatings for the UV, visible and near infrared. Optical interference occurs in thins films with thicknesses of the order of the wavelength of light, and such coatings form the basis as building blocks for many multilayer optical coatings. Multilayer films with individual thicknesses of only a few nanometers can exhibit interesting optical and mechanical properties, features that can be exploited in the design and manufacture of precision optical coatings [2-5]. Therefore, recommendations of ceramic layer on aluminium reflector materials to use are made here based on the simulation results. However, a reflector coated with ceramic layer on aluminium thinfilm on a ceramic substrate shows promising stability of the optical properties for cost-effective in concentrating solar energy applications. The material under development offers promise as a commercially viable for solar reflector materials. In case of solar reflector coatings, it is critical for the aluminium thin films to reflect as much of the incident solar energy as possible which implies that the reflectance should be maximum across the whole of the solar spectrum. Thin films used for such applications where heat transfer is of prime importance, the added requirements are stability at high temperature and minimizing radiation in the thermal infrared band. Thus there are complex set of requirements of strong reflection [6]. In the present work, Aluminium thin films with thickness of 400 nm were modeled and simulated with Al2O3 as bond layers and protective layers on ceramic substrate for solar reflectors application. Reflectors with thin film coated aluminium does not withstand outdoor ageing ,The initial total and specular solar reflectance of aluminium thin film is 96 %, The fast degradation of the specular reflectance of aluminium thin film will decreased unless it is protected by ceramic coatings. Simulation study was carried out to find best combination of material among adhesion layer, and each of the protective layers on aluminium reflective layer and to maximize reflection. We have carried out modeling and simulation of multilayer system with aluminum as a reflective layer by varying protective layer material and its thickness as model shown in Fig. 1. It is significant to improve the efficiency of solar reflector systems which will strongly depend on the optical properties of solar reflective materials and multi-layer structure [7-12]. Protective Layer Metal High Reflective Layer Bond Layer Ceramic Substrate Fig.1. Schematic of Multilayer Design of Reflective Coating
2. Experimental The thin film Aluminium Coatings were deposited on ceramic substrates using DC Magnetron sputtering process and Al2O3 using RF power supply as bond layer and protective layer. Desired substrates with a dimension 30mm x 30mm are used for deposition and substrates are cleaned by a solvent clean followed by de ionized water rinse, followed by mild acid clean, DI rinse and blow dry, Fig. 2 shows the schematic diagram of the sputtering chamber
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Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
All the coating processes are carried out in vacuum chamber at a base pressure of 1 x 10-5 mba using argon gas (99.999%), deposition of Aluminium (99.95%) were performed at 2000w by using DC power supply and Al2O3 at 1200w by using RF power supply. The deposition chamber was filled with pure argon gas with a flow rate of 500sccm for target cleaning; pre sputtering process was carried out with shutter positioned over the target there by shielding the flow of plasma towards the substrate for about 5 minutes. The deposition parameters maintained during the process are tabulated in Table 1. All depositions were performed at a fixed substrate to source distance of 270mm with a substrate rotation at a rate of 2rpm. modelling and simulation was carried out using CODE software Optical reflection measurements on the films were carried out using UV-VIS-NIR spectrophotometer (Model Lambda 750) with the wavelength ranging between 250-2500nm.Film thickness measurements were carried out using DEKTAK 6M surface profiler, surface topography and mechanical properties of the films were carried out using Hysitron TI 750L Nano Mechanical System.
Fig.2. Schematic of the Magnetron Sputtering Setup Table 1 Sputtering parameters for multilayer thin film deposition Process Parameters Sputtering Gas Argon flow rate (sccm) Power supply Sputtering Power (w) Temperature Substrate Multilayer (ML1) Multilayer (ML2) Multilayer (ML3) Base Pressure (torr) Targets
Values Argon 500 DC, RF 2000 &1200 RT Ceramic Al2O3 (100)+Al (400)+ Al2O3 (100) Al2O3 (200)+Al (400)+ Al2O3 (200) Al2O3 (300)+Al (400)+ Al2O3 (300) 1 x 10-5 Aluminum, Al2O3
3. Results and Discussions The simulation and experimental deposition was carried out by varying Al2O3 thickness, and percentage (%) of reflection was plotted against the wavelength is as shown in Fig. 3 (a) and solar Reflectance plotted as shown in the Fig. 3 (b). In general, metals have very high extinction coefficients, making them good reflectors, From the Fig. 3 (a) and 4(b) it clearly seen that there is a limit for the reflection of aluminum thin film that is around 96% which is called as reflectivity of the aluminum thin film and even after increase in the thickness of aluminum thin film there is no variation (in simulation it is around 100-300nm but in practical it depends on the process and microstructure of the deposited film). With respect to change in the thickness of Al2O3 that is from 100 to 300nm, the reflectance increases from 92 to 96 because of shift in the antireflection part, Table 2. Optical reflectance of aluminium films deposited on ceramic substrate.
Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
a
2997
b 100
100 90 80 70 60 50 40 30 20 10 0
90 Reflection (%)
Reflection (%)
80 70 60 50 40 30 20 10 0
250
500
250
750 1000 1250 1500 1750 2000 2250 2500 Wavelength (nm) ML1 ML2 ML3
500
750
1000 1250 1500 1750 2000 2250 2500 Wavelength (nm) ML1
ML2
Ml3
Fig.3. Shows Reflectance spectra for Multilayer coatings on ceramic substrate (a) Simulation (b) Experimental Table 2 Optical reflectance of aluminium films deposited on ceramic substrate Coatings
Sample ID
Al2O3+Al+Al2O3
ML1 ML2 ML3
Experimental Reflectance (%) UV VIS NIR 57.87 70.02 92.79 61.24 73.39 96.16 64.96 74.92 96.40
Simulation Reflectance (%) UV VIS NIR 87.01 83.61 94.89 88.12 87.51 94.35 88.12 87.51 94.35
Fig. 5 shows the AFM images of the multilayer coatings. The surface roughness increased from Ra of 6 nm to 22nm as shown in table 4. Fig. 4 shows the nano indentation plots of magnetron sputter coated multilayer thin films on ceramic substare at room temperature. The hardness of the multilayer films coated at room temperature with 100nm Al2O3 as bond layer and protective layer (ML1) is ~4.67GPa, hardness of the multilayer films coated at room temperature with 200nm Al2O3 as bond layer and protective layer (ML2) is ~5.70GPa and hardness of the multilayer films coated at room temperature with 300nm Al2O3 as bond layer and protective layer (ML3) is ~6.83GPa due to the effect of surface roughness. The stiffness and modulus values of these films are given in Table 3. The stiffness and the modulus increased by 6 to 10%. 3000
Load (uN)
2500 2000 1500 1000 500 0 0
20
40
ML1
60 80 Depth (nm) ML2
100
120
140
ML3
Fig.4. Nano indentation test Multilayer thin films on ceramic substrates at a maximum load of 3000µN
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Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
Table 3 Nano indentation mechanical property of Multilayer thin films Coatings Al2O3+Al+Al2O3
Sample ID ML1 ML2 ML3
a
S(µN/nm) 81.86562 84.90836 88.41992
Er(GPa) 90.48077 93.75 96.88694
H(GPa) 4.666091 5.700542 6.836692
b
c
Fig.5. AFM images of Multilayer thin films on ceramic substrates (a) ML1 (100nm)Al2O3+(400nm) Al+(100nm) Al2O3, (b) ML2 (200nm)Al2O3+(400nm) Al+(200nm) Al2O3 and (b) ML3 (300nm)Al2O3+(400nm) Al+(300nm) Al2O3 Table 4 Roughness of aluminium films deposited on ceramic substrate Coatings Al2O3+Al+Al2O3
Sample ID ML1 ML2 ML3
Ra 6.46 17.11 22.99
RMS(Rq) 10.15 20.55 27.82
4. Conclusions Multilayer thin films on ceramic substrate results in formation of reflective layer with combination with aluminium and Al2O3 deposition using DC and RF magnetron sputter at room temperature, even though the sputter target is 4N pure aluminium and Al2O3, the as deposited aluminium thin film on the ceramic substrate could be a combination of Al2O3 as bond layer and protective layer with thickness ranging from 100-300nm. Since Aluminium is used as a reflective layer it needs to protect using oxide layer to enhance the life of the reflector, As a result the hardness of the film can also be increased and can go up from 4 to 7GPa. The surface roughness of the multilayer coatings deposited has finer for ML1 with 100nm of bond layer and protective layer with aluminium as reflective layer with thickness of 400nm is 6nm with increase in thickness of ML3 to 300nm of Al2O3 as bond later and protective layer the roughness as increased to 22nm deposited with substrates at room temperature The UV-VIS-NIR response of the multilayer coatings as a reflection ranging from 84 to 96% in visible and near IR region while it is reduced in ultraviolet region in the wavelength range of 250 to 2500 nm. The simulation data and the experimental results are similar in the wavelength range of 250-1500 nm, and beyond this value there is a deviation between simulation and experimental results because NIR response is sensitive to surface roughness and film stress. 5. Acknowledgements The authors would like to thank the Solar Energy Research Initiative (SERI) Department of Science and Technology, New Delhi, India for funding this research work. The authors gratefully acknowledge the support from management of R.V. College of Engineering, Bangalore, The National Institute of Engineering Mysuru, and Visveswaraya Technological University, Belagavi.
Muralidhar singh M et al., / Materials Today: Proceedings 5 (2018) 2994–2999
References [1] Correa .G, Almanza .R, Martinez, Mazari M, Cheang J. C., Solar Energy Materials and Solar Cells, 52 (1998) 231-238. [2] Moralez, A. and Duran A., Journal of Sol-gel Science and Technology, 8 (1997) 51-457. [3] Rafael Almanza, Genaro Correra, Marcos Mazari, Genaro Correa, Solar Energy, 54 (1995) 333-343. [4] Le Paven-Thivet, C. Malibert, Ph. Houdy, P.A. Albouy ,Thin Solid Films, 336 (1998) 373-376. [5] Quintana P, Oliva A I, Ceh O and Corona, J. E, Aguilar M, Superficies y Vacío, 9 (1999) 282-282. [6] Y.G. Shen , Y.W. Mai, Material Science and Engineering A, 284 (2000) 176-183. [7] C. E. Kennedy , R.V. Smilgys, D. S. Kirkpatric, J. S. Ross, Thin Solid Films, 304 (1997) 303-309. [8] Thomas Fend, Bernhard Hoffschmidt, Gary Jorgensen, Harald Kuster, Riffelmann, Solar Energy, 74 (2003) 149–155. [9] Maria Brogrena, Anna Helgesson, Bjorn Karlsson, Johan Nilsson, Arne Roos, Solar Energy Materials & Solar Cells, 82 (2004) 387–412. [10] Maria Brogren, Bjorn Karlsson, Arne Roos, Anna Werner, Solar Energy Materials & Solar Cells, 82 (2004) 491–515. [11]Cremer R, Witthaut M, Neuschutz D, Erkens G, Leyendecker Feldheg M, Surface and Coatings Technology,120 (1999) 213-218. [12] Kirill Bordo and Horst-Gunter Rubahn, Material Science, 18 (2012) 313-317. [13] S. Shawki, S. Mikhail, Materials and Manufacturing Processes, 15 (2000) 737-746. [14]K. S. Ahn, Y. C. Nah and Y. E. Sung, Journal Vacuum Science Technology A, 20 (2002)1468–1474.
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