DOI: /jtasr/2015/17 REVEIW ARTICLE

Transcription

1 REVIEW ON SILICON DOPED DIAMOND LIKE CARBON FILMS AND THEIR CHARACTERIZATION Vishnukant Amdabade 1, Ramesh V 2, Desai S. M 3, Raju G. K. M 4, Shekhar S. M 5 HOW TO CITE THIS ARTICLE: Vishnukant Amdabade, Ramesh V, Desai S. M, Raju G. K. M, Shekhar S. M. Review on Silicon Doped Diamond Like Carbon Films and their Characterization. Journal of Technological Advances and Scientific Research; Volume. 1, Issue 3, July-September 2015; Page: , ABSTRACT: Diamond like carbon (DLC) coating is an amorphous form of carbon with a significant percentage of SP 3 hybridized carbon and sp 2 hybridized carbon (Graphite). The DLC has high internal compressive stress, which limits deposition of thick coatings. Incorporating metals and a few other elements into DLC coating results in the reduction of compressive internal stress and improvement of adhesion to substrates allowing deposition of thicker films. They have high hardness, low coefficient of friction, nontoxic, chemically passive and corrosion resistant. Silicon is an extremely pure semiconductor, which is used for the purpose of modulating its electrical properties. Here the deposited coatings by silicon are characterized for thickness, Chemical composition and Raman spectroscopy. They have applications in manufacturing industries including plastic moulds, extrusion dies, cutting tools, aerospace field, including ball joint components and fuel injection valves. KEYWORDS: DLC, Silicon doped DLC, XPS, and Raman Spectroscopy I. INTRODUCTION: 1.1 Diamond like Carbon (DLC) Films: Carbon is a 6th component in the periodic table with an atomic weight of 12 and belongs to the material. [1] Carbon has become a key element in the synthesis of thin coatings of diamond, diamond like carbon (DLC), carbon nitride, boron carbide and Chromium carbide and other carbide coatings. The excellent mechanical, tribological and electrical properties, these coatings offer presently utilized as engineering applications viz., control friction, wear and as hetero junction devices in microelectronics, manufacturing industries including plastic molds, extrusion dies, cutting tools, aerospace field including ball joint components and fuel injection valves. [2,3,4] Carbon presents allotropy, i.e. four different phases have been found in solid state: graphite, diamond, Fullerenes and nanotubes and amorphous carbon. They are constituted by carbon atoms bonded by sp 2, sp 3 and combinations of both hybridizations, respectively. 1.2 Properties of DLC Films: DLC films exhibit high hardness, low friction coefficient and chemically inert, non-toxic DLC films. Assemble with an abnormal state of sp2-hybridized carbon atoms act like graphite in tribological tests, while films with more sp3-hybridized carbons exhibit hard and high level tribological properties. [11] DLC Films formed from a hydrocarbon source, for example, acetylene or methane contains the presence of hydrogen. In the ternary phase diagram indicated in Fig.1.5Different DLC films are grouped into hydrogenated carbons (a-c:h), non-hydrogenated carbons (a-c) and tetrahedral carbon (ta-c) depending on hydrogen% and sp3 bonding. J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 136

2 Fig. 1.5: The ternary phase diagram of hydrogen and differently bonded carbon atoms. 1.3 DLC Deposition Techniques: The deposition of carbon thin films can be done by different methods. To reduce contamination of the coatings are conducted under preparation procedures require vacuum. The different techniques to deposit DLC have two attributes: a) Plasma is utilized to generate reactive species. b) In the deposition process, energetic particles (Ions and/or Neutrals) are involved. DLC Deposition is Generally Carried out by: 1. Physical vapor deposition (PVD). 2. Chemical vapor deposition (CVD). Fig Physical vapor deposition (PVD): The PVD technique involves condensation of a vapor in a high vacuum (~ Pa) on the substrate surface. Evaporation, DC, RF or ion beam sputtering and ion plating, Pulsed Laser Deposition are examples of PVD processes Chemical Vapor Deposition (CVD): Chemical vapor deposition is a high temperature thermochemical processes, wherein chemical reactions occur over the substrates kept at O C. The applications of high substrate temperature restrict the parts of high temperature materials. Due to release of heat and higher stresses, coatings are constrained to ~10μm. The CVD method produces consistent coatings with high hardness and great bond to the substrate. Plasma enhanced chemical vapor deposition (PECVD) has been developed for deposition using the chemical vapor deposition. The present review study provides details of Chemical vapor deposition methods followed for development of DLC films using different methods for different applications, we can able to know the silicon doped DLC by either TMS solution or Silicon target over the silicon wafer or stainless steel (SS) substrates are characterized for their silicon composition, thickness and their deposition rate and their bonding configuration. To know their good adhesive property and the tribological behavior over the coated samples by characterizing them. II. MATERIALS AND METHODS: The major studies have been carried out by S.C Ray et al. (2005), Mukhtar H et al. (2013), Shih-Fu Ou et al. (2013), have studied the Radio Frequency Plasma Enhanced Chemical Vapor Deposition method. Sk. F. Ahmed et al. (2012) have carried out the experiments by Direct Current-PECVD and Junjun Wang et al. (2013) have carried out experiments by J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 137

3 hollow cathode plasma immersion ion implantation. The parameters of the same are given below in Table 2.1. Author Methods Substrate RF (MHz) Bias Voltage (V) S.C Ray et al. (2005) RF-PECVD Silicon wafer V Sk. F. Ahmed et al. (2012) DC-PECVD Stainless steel Density-12.5mA 1 kv Mukhtar H et al. (2013) RF-PECVD Silicon wafer V Shih-Fu Ou et al. (2013) RF-PECVD Silicon wafer Power W 200ºc Junjun Wang et al. (2013) HCPIII Silicon and SS 5Hz -10kV Table 2.1 parameters for various experiments S.C. Ray et al. [5] (2005): Have studied about the silicon doped diamond like carbon (Si:DLC) films deposited on silicon substrate by RF (13.56MHz) by using PECVD (Dia-vac Model 320) with electrode self-bias voltage of 400 V. For samples of stainless steel and silicon wafers were placed in deposition chamber and created a vacuum of about mbar. Just before deposition, the substrates were cleaned using Argon (Ar) ions for 5 min. The surface modification was done by etching process, i.e, using 13.65MHz RF DC power supply. Pure DLC films were deposited using a gas mixture of Argon (Ar) and C 2H 2 (1:2 SCCM), whereas silicon doped DLC films (a-c:h:si) was deposited using Tetra Methyl Silane (TMS) vapor [Si(CH 3) 4]. During deposition of silicon the gas flow rates are varied from 5 and 20Sccm (Standard cubic centimeters per minute). Sk. F. Ahmed et al. [9] (2012): The PECVD chamber was designed with appropriate stainless steel (SS) vacuum couplings through which different feed-through like vacuum port, pressure gauge, gas mixture inlets, thermocouple etc. could be introduced. The plasma was produced between two parallel plate SS electrodes. The lower disc was grounded upon which the substrate was placed. A substrate heating arrangement was made with appropriate substrate heater placed on the grounded electrode. The upper disc was used as the cathode electrode. When the chamber pressure attained 10-5 mbar, then C 2H 2 gas was introduced and DLC films were deposited at a pressure of 0.4 mbar. Glass and alumina as substrates. Deposition was made at 1.0 kv DC supply and the corresponding current density was 12.5 ma cm -2 for 30 min. duration. For silicon incorporation tetraethyl orthosilicate (TEOS) dissolved in methanol solution was used. Argon gas was passed through the solution for bubble forming and then introduced into the chamber with the appropriate needle valve arrangement. Si concentration was varied in the deposited films by varying the concentration of TEOS in the methanol solution Mukhtar H et al. [6] (2013): Have studied about the diamond like carbon film coatings on substrate for creating biocompatible surfaces for medical implants. DLC and silicon doped DLC were synthesized on silicon substrates by using PECVD. DLC and Si-DLC films were deposited on silicon wafer substrate by MHz radio frequency PECVD using a Diavac model 320PA (ACM Ltd.) with a negative electrode biasing of about 400V. Before deposition of the films, the silicon wafers of size ( ) cm 2 and these wafers were ultrasonically cleaned with acetone and iso-propanol for 5mins followed by washing with distilled water and then dried using nitrogen gas. J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 138

4 The cleaned samples were placed in the deposition chamber on top of a water-cooled electrode driven by an RF power supply. The chamber was pumped down to a base vacuum of about millibar. After attaining a vacuum millibar the substrates were cleaned by passing Argon gas into the chamber. Later the surface modification of films was done by creating a plasma (60 cm 3 /min) The films were prepared using Argon and C 2H 2 with Tetra Methyl Silane (TMS) (Si(CH 3) 4 [99.8% Sigma-Aldrich]) was used as the reactant gas. The (Ar:C 2H 2) flow ratio was fixed at (10:20) standard cubic centimeter per minute (Sccm), and the deposition time was fixed for 5 min. In the case of silicon doped DLC, the various doping concentrations of silicon were achieved using TMS. Shih-Fu Ou et al. [7] (2013): Have studied the Hydrogenated diamond like carbon containing Si films were synthesized using RF-PECVD.A combination of many deposition processes such as RF magnetron sputtering and plasma enhanced chemical vapor deposition was used to deposit Si-doped thin films on silicon wafer substrates. The substrates with 1 cm diameter and 2 mm thickness was cleaned by step by step procedure like grinding with different emery papers and then cleaned with acetone by ultrasonification for 15 min, deionized water with 10 min, then with ethanol for 15 min. Further drying the samples at 80ºC for 8 h in the oven, the prepared substrates were loaded in the deposition chamber. The distance between the target and substrate was fixed at 60 mm. After evacuating the chamber and heating the substrates to 200 C, the methane argon gas mixture in a ratio of 1:1.5 was introduced and the RF plasma was triggered. Five different plasma power, 100, 150, 200, 250, and 300 W were respectively applied for 10 min to deposit different films. Junjun Wang et al. [8] (2013): Studied the Diamond-like carbon films have been extensively studied over the past decades due to their unique combination of properties. The stainless steel substrates of size (30mm 20mm 1mm) for tribological tests and Si wafers for chemical composition of film microstructures. Before deposition the substrates were cleaned ultrasonically with ethanol and acetone bath and then dried with nitrogen. The deposition process was carried out by using plane hallow cathode plasma-enhanced chemical vapor deposition (HCPIII) system. The deposition system is made of stainless steel 304L vacuum chamber with front opening door. The substrates were placed in a vacuum chamber and the system is pumped down to a base vacuum of about 5x10-6 mbar to minimize contamination. After reaching the vacuum the substrates were cleaned by passing Argon (Ar) gas into the chamber and the surface modification was done with RF plasma. The silicon ions were implanted into the substrate from the Silane (SiH 4) plasma to produce interfacial mixing layer of silicon and substrate materials. In the deposition a -10KV voltage is applied. Five coatings with varying Si concentrations were considered in this report. Argon and acetylene gases were used in the ratio of 100:100 Sccm. III. RESULTS AND DISCUSSION: S. C. Ray et al., Mukhtar H et al., Junjun Wang et al. Have discussed about the thickness of coated films. The details of the same are given as in Table Thickness Measurements: S.C. Ray et al: First sample have verified for thickness of deposit films using methane (C 2H 2) vapor precursor, the second one using Tetra Methyl Silane [TMS], and the third one using both C 2H 2 and TMS. The total thickness of the films is 150±15 mm and was controlled by the deposition time. J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 139

5 Mukhtar H et al: Have measured the film thicknesses of DLC and Si-DLC samples have been obtained and the values were arranged from (~ ) mm, the growth rate of film deposition was around (38±6) mm min -1. Junjun Wang et al: Measurement of Cross sections of DLC and Si-DLC films were found dense and featureless. The thickness of all the films was controlled to about 3.2μm [10]. The thickness of the deposited film in their work was varied from 150 mm to 3.2μm with deposition of the coating in three steps viz., using (i) methane gas first (ii) Tetra Methyl Silane (iii) methane and TMS solution and the moderate thickness of the coated samples was about 218 mm. Table 3.1 SHOWS CHARACTERIZATION TECHNIQUE AND RESULTS: Author Methods Thickness Measurement Si Composition I D/I G ratio S.C Ray et al. (2005) RF-PECVD 150± % Sk. F. Ahmed et al. (2012) DC-PECVD % - Mukhtar H et al. (2013) RF-PECVD % - Shih-Fu Ou et al. (2013) RF-PECVD % Junjun Wang et al. (2013) HCPIII 3.2µm % Table 3.1 characterization techniques and results 3.2 Silicon Composition Analysis: S.C. Ray et al: The pure silicon composition was found to be 22.09% and the composition of silicon doped DLC was found to be 19.73% using TMS solution in both the cases. Table 3.2 shows the Silicon composition for pure silicon and silicon doped DLC [11]. Ar (sccm) C 2H 2 (sccm) TMS (sccm) Composition C (at.%) Si XPS O Table 3.2 Silicon composition for Si and Si:DLC films Mukhtar H et al: Have reported the survey scan of XPS spectra of doped and undoped DLC. The concentration of XPS spectra is as shown in Fig The Silicon percentage obtained from the experiment were about 13.30% and the carbon atom percentage in the DLC was found to be 86.70%. In the scan of XPS spectra of doped and undoped DLC the main peaks were observed at ~285.1 ev, and ~531.4eV, corresponding C1s and O1s, bands, respectively the first band was located at ev, which is relevant to sp2 hybridized carbon atoms (C=C). The second band was located at ev, which correspond to sp3 hybridized carbon atoms (C-C), and the last band was located at ev, which can be relevant to the (CO) bonds [12]. J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 140

6 Fig. 3.1: XPS Survey Scan for DLC and Si-DLC. Fig. 3.1 Shih-Fu Ou et al: Have reported the X-ray photoelectron (Bonding analysis) spectroscopy (XPS; AES- 650, monochromatic Al Kα radiation) was employed to analyze the element bonding and to quantify the composition of the deposited films. Before the XPS detection, the surface was cleaned by 3 kevar+ ion beam. For analyzing the XPS spectra, the Shirley background and mixed Gaussian/Lorentzian function were used for peak fitting via XPSPEAK 4.0 software. The XPS quantitative results indicate that the Si/a-C:H ratios of films deposited at plasma power of 100W, 150W, 200W, 250W and 300W are 0.16, 0.17, 0.21, 0.24 and 0.49, respectively. The Si/a-C:H ratio increases exponentially with the plasma power applied to silicon electrode. All films with different Si content exhibits a typical amorphous structure as conventional PECVD deposited a-c:h film in the X-ray diffraction analysis shown in Fig [13,14] Fig. 3.2: XPS C 1s spectra of the a-c:h/si films with different Si/a-C:H ratio. Fig. 3.2 Junjun Wang et al: Table 3.3 gives the Percentage of the Si, C and O at.% detected in the films by XPS analysis. As the tests shows that the carbon, Si and O are detected in the surface of Si-DLC and only C and O are present in the surface of pure DLC films. The silicon concentration almost linearly increased with the SiH 4 flow ratio during the deposition. With the SiH 4 flow rate 100 Sccm min -1, the silicon concentration increase to at.% and the carbon concentration drop to at.% [15]. J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 141

7 Sample Composition (at.%) XPS C Si O Table 3.3 Silicon composition by XPS Sk. F. Ahmed et al: Have conducted the XPS survey scan of the silicon-doped DLC films shown clearly the contributions from the results have C 1s (~285 ev), Si 2p (~100 ev), Si 2s (~151 ev) and O 1s (~531 ev) [6]. Typical spectra of DLC film and silicon incorporated DLC film shown in Fig Since XPS is a very surface sensitive technique, the detection of oxygen suggests various sources of surface contamination. The silicon composition was found to be 14.28%. Further Silicon doping carried out over the samples, the silicon concentration over. If the concentration exceeds larger over the coated samples, there was chance but for very high coating to be get peeled of which indicates having very poor adhesion property. Fig. 3.3: The XPS spectra of the DLC films& Si-DLC. Fig I D/I G Ratio Analysis Using Raman: S.C. Ray et al: Have measured the I D/I G ratio of the Si-doped films is comparatively lower to that of undoped, which indicates higher sp3 content in the doped films. In a-c/h/si films (Si/DLC), the I D/I G ratio is related to the size of the aromatic clusters in the films. The I D/I G ratio varies from 0.16 to 0.36 [16]. Raman spectra of Si:DLC is shown in Fig. 3.4 J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 142

8 Fig 3.4: The Raman spectra of silicon doped and undoped DLC films. Fig. 3.4 Shih-Fu Ou et al: Have used two Gaussians to analyze the Raman spectra. The area ratio of two peaks, I D/I G, of each film with different Si content was calculated and plotted as functions of Si ratio in Fig This ratio is related to the SP 3 /SP 2 bonding ratio; hence, I D/I G curve in Fig The I D/I G, value barely increases with the Si content and plasma power, which indicates that the fraction of SP 2 bonding and cluster size might increase with the silicon content and plasma power. The I D/I G ratio varies from 1.15 to 1.2 [13]. Fig. 3.5: Dependence of the Raman intensity ratio and the I D/I G ratio. Fig. 3.5 Junjun Wang et al: Have reported results for the spectra the I D/I G ratio and the silicon composition, are shown in Fig It is clear that the G peak position shift from 1566 to 1484 cm 1 and G peak FHWM increases from 128 to 194 cm 1 with an increase in Si concentration from 0 to at.%. The ratio I D/I G of the films decreased from about 1.16 for the Si-free DLC to 0.58 for the at.% Si- DLC. [15] J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 143

9 Fig. 3.6: Intensity ratio of G and D peak as a function of Si concentration. Fig. 3.6 IV.CONCLUSIONS: Silicon doped DLC coatings have been deposited by Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) with different concentrations of Silicon by varying the sputtering parameters like voltage, frequency and chamber pressure. The coated samples were characterized for thickness, elemental composition and I D/I G ratio. The conclusions can be given as The minimum thickness of the coated sample was obtained of about 150mm at 400V, 13.56MHz frequency and the maximum thickness of the coated samples was obtained of about 3.2µm at -10KV for 1 hour and deposition rate was 53.5mm/min. It is observed that deposition using higher voltage will result in good thickness and deposition rate. The minimum silicon composition was found to be 0.16% and 0.49% for 100W and 300W respectively. And the maximum silicon composition was found to be 19.73% to 22.09% using RF- PECVD. It was observed that with increase in sputtering power results in increase of silicon composition. The bonding structure with silicon was analyzed using Raman spectroscopy and the I D/I G ratio was found to be varied from 0.58 to 1.2 which indicates that area under the Diamond peak (D- Peak) is higher and shows good adhesion property. V. FUTURE SCOPE: The thickness of the samples can be increased by using the RF-PECVD method at higher voltages viz., -15KV and -20KV. The silicon composition can be increased beyond 22 at.% by carrying out the process at 450V and 500V. The I D/I G ratio can be increased by increasing the silicon composition. VI-REFERENCES: 1. Kenneth Holmberg, Helena Ronkainen, AnssiLaukkanen, Kim Wallin, Friction and wear of coated surfaces- scales, modelling and simulation of tribomechanic, Surface and Coatings Technology, V202 p1034 (2007). 2. A. Sikora. A. Berkesse O. Bourgeois J.-L. Garden, Electrical properties of boron-doped diamondlike carbon thin films deposited by femtosecond pulsed laser ablation, ApplPhysA V94 p105 (2009). J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 144

10 3. Yu Xiang, wangcheng-biao, liu yang, Cr-doped DLC films on three mid-frequency dual magnetron power modes, Surface and Coatings Technology, V200 p6765 (2006). 4. J. A. Colón Santana, R. Skomski, V. Singh, Negative magnetoresistance in Cr-containing diamond-like carbon-based heterostructures, Journal of ApplPhys A 98: p811 (2010). 5. Electronic structure and photoluminescence study of silicon doped diamond like carbon (Si:DLC) thin films by S.C. Ray, T.I.T. Okpalugo b, C.W. Pao c, H.M. Tsai c, J.W. Chiou c, J.C. Jan c, W.F. Pong c, P. Papakonstantinou b, J.A. McLaughlin b, W.J. Wang 482, (2005). 6. Characteristic of silicon doped diamond like carbon thin films on surface properties and human serum albumin adsorption by Mukhtar H. Ahmed, John A. Byrne, James McLaughlin, Waqar Ahmed, 4, (2013). 7. Surface properties of nano-structural silicon doped carbon films for biomedical applications by Shih-Fu Ou, Chin-Sung Chen, HosseinHosseinkhani Vol. 10, Nos. 10/11, (2013). 8. Tailoring the structure and property of silicon-doped diamond-like carbon films by controlling the silicon content by Junjun Wang, JibinPu, Guangan Zhang, Liping Wang 235, (2013). 9. Silicon incorporated Diamond like Carbon films for field emission Display by Sk. F. Ahmed, S. Das, M.K. Mitra and K. K. Chattopadhyay Vol 06, (8-12 Oct). 10. S. Neuville, A. Matthews, Thin Solid Films 515, (2007). 11. P. Papakonstantinou, J.F. Zhao, P. Lemoine, E.T. McAdams, J.A. McLaughlin, Diamond Relat. Mater. Vol 11, 1074 (2002). 12. M. Ahmed, A. J. Byrne, J. McLaughlin, A. Elhissi, D. A. Phoenix and W. Ahmed, Vibrational and AFM Studies of Adsorption of Glycine on DLC and Silicon-Doped DLC, Journal of Materials Science, Vol. 47, No. 4, pp (2012). 13. Rodil, S.E., Olivares, R., Arzate, H. and Muhl, S. Properties of carbon films and their biocompatibility using in-vitro tests, Diamond Relat. Mater., Vol. 12, pp (2003). 14. Roy, R.K., Choi, H.W., Park, S.J., Lee, K.R., Roy, R.K., Choi, H.W., Park, S.J. and Lee, K.R. Surface energy of the plasma treated Si incorporates diamond-like diamond carbon films, Diamond Relat. Mater., Vol. 16, pp (2007). 15. C. Cao, H. Zhu, H. Wang, Thin Solid Films 368, (2000). 16. S. Rodil, A.C. Ferrari, J. Robertson, W.I. Milne, J. Appl. Phys. 89, 5425 (2001). J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 145

11 AUTHORS: 1. Vishnukant Amdabade 2. Ramesh V. 3. Desai S. M. 4. Raju G. K. M. 5. Shekhar S. M. 4. Associate Professor, Department of Chemical Engineering. DayanandaSagar College of Engineering, Bangalore. 5. Professor, Department of Chemical Engineering. DayanandaSagar College of Engineering, Bangalore. PARTICULARS OF CONTRIBUTORS: 1. M-Tech. Student, Department of Chemical Engineering. DayanandaSagar College of Engineering, Bangalore. 2. M-Tech. Student, Department of Chemical Engineering. DayanandaSagar College of Engineering, Bangalore. 3. Associate Professor, Department of Chemical Engineering. DayanandaSagar College of Engineering, Bangalore. NAME ADDRESS ID OF THE CORRESPONDING AUTHOR: Vishnukant Amdabade, #5 (Old# 22), 5 th Cross, Hosakerehalli, Bangalore. vishnuamdabade@gmail.com Date of Submission: 17/08/2015. Date of Peer Review: 18/08/2015. Date of Acceptance: 20/08/2015. Date of Publishing: 24/08/2015. J of Tech Advances & Sci Research, eissn , pissn /vol. 1/Issue 3/July-Sept Page 146