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Plasma-ion beam source enhanced deposition system
Surface & Coatings Technology 193 (2005) 112 – 116 www.elsevier.com/locate/surfcoat
Plasma-ion beam source enhanced deposition system Guoqing Lia,*, Cui Liua, Jianfeng Lib, Chengwu Zhanga, Zongxin Mua, Zhenhu Longa a
State Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian, P.R. 116024, China b Tomsk Polytech University, Tomsk, Russia, 63500 Available online 10 December 2004
Abstract An advanced deposition system, plasma-ion beam source enhanced deposition system, is introduced. This equipment is composed of metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source. The metal implantation source and the gas implantation source are working with cathode arc and magnetron sputtering simultaneously. Many kinds of duplex technologies of plasma enhanced deposition can be realized in this system. The characteristics of plasma sources are described. Some duplex hard coatings are prepared, such as metal-doped diamond-like carbon (DLC) films, nitriding-TiN films and hard coatings on bearing steel at low temperature. The performances of these films were studied. The results show that the processes can be widely used in industry. D 2004 Elsevier B.V. All rights reserved. Keywords: Plasma enhanced deposition; Duplex technology; Hard coating; Performance
1. Introduction It is widely recognized that surface engineering is an important technology that will enhance strength and working life of tools and molds for industrial application. In the past decade, many technologies have been improved and widely used, such as plasma enhanced chemical vapor deposition (PECVD), plasma immersion ion implantation (PIII) and plasma source ion implantation (PSII). Duplex technology is an advanced technology. As the name implies, duplex technology involves the sequential application of two (or more) established surface technologies which are unobtainable through any individual surface technology [1]. According to the interactions between the two individual processes and their relative contributions to the combined effects of the composite layer. The typical duplex technologies are PVD coating of pre-nitrided steel, TiC (TiN) intermediate layer for DLC coatings, MoS2 lay on electroless Ni coatings. Dong et al. [2] found that the combined plasma nitriding and PVD TiN coating treatment could * Corresponding author. Tel.: +86 411 84708389; fax: +86 411 84708389. E-mail address: [email protected] (G. Li). 0257-8972/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2004.07.040
significantly improve the corrosion resistance of the duplex system. A graded intermediate layer, Ti/TiN/TiCN/TiC, between steel and DLC coatings was usually used to ensure good adhesion of the DLC coatings [3]. In this paper, we introduce a new deposition system— plasma-ion beam source enhanced deposition system. This system can realize many kinds of duplex deposition technologies. Some duplex hard films were prepared in this system, and the performances also were studied.
2. Plasma-ion beam source enhanced deposition system The equipment of plasma-ion beam source enhanced deposition is a new advanced system, which can realize the metal (gas) ion beam enhanced deposition technology and plasma source surface strength-deposition duplex technology. It is the foundation of industrialization for ion beam technology. The schematic diagram of the plasma-ion beam source enhanced deposition system is shown in Fig. 1. This equipment is composed of metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source.
G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
113
Fig. 1. Schematic diagram of plasma-ion beam source enhanced deposition system.
The main functions of the equipment are as follows: 1. 2. 3. 4.
ion implantation of metal and gas with low energy; plasma source surface strength and deposition duplex technology; ion implanted enhanced deposition technology; planar plasma source enhanced deposition technology.
2.1. Hot filament plasma source The main advantage of the hot filament plasma source is that it can be performed with multi-arc source or magnetron sputtering simultaneously at higher vacuum. The voltage of hot filament power is in the range of 0–10 V, the applied power is 2 kW. The current density of ion bombardment can get to 2 mA/cm2. The effect of ionized current on plasma density is shown in Fig. 2. The plasma density in the center of vacuum chamber can be got 8109/cm3. This plasma source can be used with bias power, multi-arc source or magnetron sputtering source simultaneously to realize the duplex technology of surface strength and plating films, especially at high vacuum (10 1 Pa).
voltage, in this case, the energy of ion beam also increases. The planar plasma source can be operated with magnetron sputtering source to composing plasma enhanced magnetron sputtering deposited system (PMD), which will increase the adhesion between film and substrate. 2.3. Metal and gas ion implantation source The sources are metal ion implantation source and gas ion implantation source with high current and large area for industrial applicant. It can be used for material modification and advanced material preparation. In the ion implantation sources, accelerated voltage ranges from 10 to 30 kV, pulsed current can be got to 300 mA, average beam current reaches to 20 mA and the diameter of beam spot is 280 mm. The working pressure ranges from 10 1 to 10 3 Pa. Therefore,
2.2. Planar plasma source The planar plasma source is composed of anode, cathode with narrow gap, magnet, cathode shield and two independent discharge chambers. This plasma source can be used for cleaning the work-pieces and depositing films with high adhesion between film and substrate. The different gas can be inlet into either discharge chambers. The voltage of planar plasma source has a quadratic relationship with the current. The current increases with the increasing of the
Fig. 2. Ionized current dependence of plasma density.
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Fig. 3. Raman spectra of DLC films.
structure was analyzed by Raman spectroscopy and transmission electron microscope (TEM). The Raman spectra of undoped and doped DLC films are shown in Fig. 3. A broad peak in the range 1200–1600 cm 1 is observed for both the undoped and doped DLC films. This confirms that the films are amorphous. The content of sp3 bonds decreases after metal ion is implanted into DLC films. The structures of Ti+ implanted DLC films were analyzed by TEM. The result shows TiC nanocrystals are formed in DLC film by implanted Ti+ (see Fig. 4). The formation of TiC reduces the co-ordination number of a-C networks by binding carbon atoms into carbide. A reduction of co-ordination number and a decrease of the local carbon atom density result in sp3Ysp2 relaxation of a-C network [5]. Metal implanted into DLC films promotes the graphitization of amorphous DLC matrix, and sp2 content increases in the DLC films. 3.2. Hot filament plasma with magnetic filter cathode arc
ion implantation and enhanced with arc or magnetron sputtering deposition can be performed at the same time, which can not only mix the interface between the film and the substrate, but can also improve the properties of film.
3. Duplex technology 3.1. Metal ion implantation with magnetron sputtering Diamond-like carbon film (DLC film) is a metastable form of amorphous carbon containing a significant fraction of sp3 bonds. DLC films have many properties similar to diamond. The low friction coefficient of DLC film plays a vital role for its industrial application. The nature and properties of the DLC films may be modified by controlling the incorporation of dopants, such as silicon, fluorine, nitrogen and various metals (Ti, Nb, Ta, Cr, W, Al, Cu) [3,4]. Ti-doped DLC films were obtained by Ti ion implanted DLC films synthesized by magnetron sputtering. The film is smooth and uniform, as observed via AFM. The roughness of Ti-doped DLC film is as low as 0.595 nm. The bond
Nitrided steel sufficiently supports the hard coating [6,7], because it exhibits higher hardness than those without nitriding process. The combined technology of plasma nitriding and PVD TiN coating treatment could significantly improve the corrosion resistance of the duplex system [8]. However, there are many duplex coating process carried out in two steps such as TiN coating/nitriding process. Duplex technology of nitriding and TiN coatings was carried out via the combination of hot filament plasma and magnetic filter cathode arc source at the same pressure. The hardness of the surface nitrided layer is 800 HK and the hardness of TiN coating can reach up to 2200 HK. Fig. 5 shows the hardness profile of nitriding sample. The hardness ranges from 800 to 340 HK near the substrate. It can be concluded that the depth of nitriding zone (include diffusion layer) can reach up to 70 Am. Cross-sectional morphology of nitriding and duplex process are shown in Fig. 6. Fig. 6(a) indicates the presence of a continuous white layer about 10 Am in the nitriding sample. The white layer is gN phase analyzed by XRD. Two sublayers, denoted by gN1 and gN2 [9], are formed in the white layer. Fig. 6(b) shows that the
Fig. 4. TEM image and diffraction pattern of Ti-doped DLC films.
G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
Fig. 5. Hardness as a function of distance from the surface for nitriding sample.
thickness of TiN layer is about 10 Am. The continuous white layer gN phase is decomposed to form the black layer. The black layer consisted of a phase and CrN phase by XRD. This is because the bombardment of Ti+ ion would induce a temperature rise in the sample during TiN coating deposition. As a result, gN phase decomposed to a phase and CrN phase. 3.3. Gas ion implantation with cathode arc source CrN and TiN hard coatings have been successfully applied for the improvement of the wear protection, and oxidation and corrosion resistance for machine tools and engineering components. The development of hard coatings to be deposited at low temperature (room temperature) is one of the general interests for basic research, and is of primary importance for industrial applications. Specifically, a large percentage of tools and machine parts are still made of alloyed tool steels or metal alloys. Ion implantation has been shown to improve the mechanical, optical and electrical properties of materials by surface modification. It has been known that the bombardment of penetrated ions not only can induce changes in the structure, but can also mix the interface between the film and the substrate. The purpose of the duplex process of gas ion implantation and cathode arc source is to realize low-temperature (room temperature) deposition technology for hard coatings and
115
Fig. 7. XRD patterns of CrN and TiN coatings.
achieve the structures and properties of those coatings that must be deposited at high temperature. TiN and CrN coatings were deposited on bearing steel of GCr15 in ambient temperature at about 3 Am. The hardness of bearing steel of GCr15 is 61 HRC; then after deposited coatings, the hardness of the samples becomes 61.5 HRC for CrN coating deposited and 59.5 HRC for TiN coating deposited, respectively. Comparing to the hardness of the samples before and after deposited coatings, the change of HRC is small. It is suggested that the change of temperature during deposition is very minimal, which cannot induce the change in the structure of the sample. The Knoop microhardness of the coatings ranges from 1750 to 2000 HK for both CrN and TiN coating. The XRD spectra of CrN and TiN coatings are shown in Fig. 7. Results show that CrN and TiN phases are formed in these coatings, respectively. It is concluded that CrN and TiN hard coatings are achieved via the duplex technology of gas ion implantation and cathode arc source at ambient temperature. Gas ion implantation can also be used for promoting atom diffusion and the growth of coatings.
4. Conclusions The equipment of plasma-ion beam source enhanced deposited is an advanced deposition system that combines
Fig. 6. Micrograph cross-sections of (a) nitriding and (b) TiN coating/nitriding layer.
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G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
with many advanced plasma sources such as metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source. Through this system, many duplex technologies can be realized, such as ion implantation of metal and gas with low energy, plasma source surface strength and deposition duplex technology, ion implantation enhanced multi-arc deposition technology, planar plasma source enhanced deposition technology. High-quality hard films are achieved through this system by using different duplex technologies.
Acknowledgement This work has been supported by National High-Tech. Program of China (No.2001AA883010).
References [1] T. Bell, H. Dong, Y. Sun, Tribol. Int. 31 (1998) 127. [2] H. Dong, Y. Sun, T. Bell, Surf. Coat. Technol. 90 (1997) 91. [3] Q. Wei, K. Sharma, J. Sankar, J. Narayan, Compos., Part B Eng. 30 (1999) 675. [4] M. Hakovirta, A.M. Peter, B. Taylor, M. Nastasi, He Xiaoming, J. Vac. Sci. Technol., Part A 20 (2002) 638. [5] A.A. Voevodin, M.A. Capano, S.J.P. Laube, M.S. Donley, J.S. Zabinski, Thin Solid Films 298 (1997) 107. [6] H.J. Spies, et al., Surf. Coat. Technol. 74–75 (1995) 178. [7] D.P. Berisov, I.M. Goncharenko, N.N. Koval, Physics (1994) 115. [8] Y. Sun, T. Bell, Mater. Sci. Eng. A1 40 (1991) 419. [9] D.L. Williamson, J.A. Davis, P.J. Wilbur, Surf. Coat. Technol. 103–104 (1998) 178.
Plasma-ion beam source enhanced deposition system Guoqing Lia,*, Cui Liua, Jianfeng Lib, Chengwu Zhanga, Zongxin Mua, Zhenhu Longa a
State Key Laboratory for Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian, P.R. 116024, China b Tomsk Polytech University, Tomsk, Russia, 63500 Available online 10 December 2004
Abstract An advanced deposition system, plasma-ion beam source enhanced deposition system, is introduced. This equipment is composed of metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source. The metal implantation source and the gas implantation source are working with cathode arc and magnetron sputtering simultaneously. Many kinds of duplex technologies of plasma enhanced deposition can be realized in this system. The characteristics of plasma sources are described. Some duplex hard coatings are prepared, such as metal-doped diamond-like carbon (DLC) films, nitriding-TiN films and hard coatings on bearing steel at low temperature. The performances of these films were studied. The results show that the processes can be widely used in industry. D 2004 Elsevier B.V. All rights reserved. Keywords: Plasma enhanced deposition; Duplex technology; Hard coating; Performance
1. Introduction It is widely recognized that surface engineering is an important technology that will enhance strength and working life of tools and molds for industrial application. In the past decade, many technologies have been improved and widely used, such as plasma enhanced chemical vapor deposition (PECVD), plasma immersion ion implantation (PIII) and plasma source ion implantation (PSII). Duplex technology is an advanced technology. As the name implies, duplex technology involves the sequential application of two (or more) established surface technologies which are unobtainable through any individual surface technology [1]. According to the interactions between the two individual processes and their relative contributions to the combined effects of the composite layer. The typical duplex technologies are PVD coating of pre-nitrided steel, TiC (TiN) intermediate layer for DLC coatings, MoS2 lay on electroless Ni coatings. Dong et al. [2] found that the combined plasma nitriding and PVD TiN coating treatment could * Corresponding author. Tel.: +86 411 84708389; fax: +86 411 84708389. E-mail address: [email protected] (G. Li). 0257-8972/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2004.07.040
significantly improve the corrosion resistance of the duplex system. A graded intermediate layer, Ti/TiN/TiCN/TiC, between steel and DLC coatings was usually used to ensure good adhesion of the DLC coatings [3]. In this paper, we introduce a new deposition system— plasma-ion beam source enhanced deposition system. This system can realize many kinds of duplex deposition technologies. Some duplex hard films were prepared in this system, and the performances also were studied.
2. Plasma-ion beam source enhanced deposition system The equipment of plasma-ion beam source enhanced deposition is a new advanced system, which can realize the metal (gas) ion beam enhanced deposition technology and plasma source surface strength-deposition duplex technology. It is the foundation of industrialization for ion beam technology. The schematic diagram of the plasma-ion beam source enhanced deposition system is shown in Fig. 1. This equipment is composed of metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source.
G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
113
Fig. 1. Schematic diagram of plasma-ion beam source enhanced deposition system.
The main functions of the equipment are as follows: 1. 2. 3. 4.
ion implantation of metal and gas with low energy; plasma source surface strength and deposition duplex technology; ion implanted enhanced deposition technology; planar plasma source enhanced deposition technology.
2.1. Hot filament plasma source The main advantage of the hot filament plasma source is that it can be performed with multi-arc source or magnetron sputtering simultaneously at higher vacuum. The voltage of hot filament power is in the range of 0–10 V, the applied power is 2 kW. The current density of ion bombardment can get to 2 mA/cm2. The effect of ionized current on plasma density is shown in Fig. 2. The plasma density in the center of vacuum chamber can be got 8109/cm3. This plasma source can be used with bias power, multi-arc source or magnetron sputtering source simultaneously to realize the duplex technology of surface strength and plating films, especially at high vacuum (10 1 Pa).
voltage, in this case, the energy of ion beam also increases. The planar plasma source can be operated with magnetron sputtering source to composing plasma enhanced magnetron sputtering deposited system (PMD), which will increase the adhesion between film and substrate. 2.3. Metal and gas ion implantation source The sources are metal ion implantation source and gas ion implantation source with high current and large area for industrial applicant. It can be used for material modification and advanced material preparation. In the ion implantation sources, accelerated voltage ranges from 10 to 30 kV, pulsed current can be got to 300 mA, average beam current reaches to 20 mA and the diameter of beam spot is 280 mm. The working pressure ranges from 10 1 to 10 3 Pa. Therefore,
2.2. Planar plasma source The planar plasma source is composed of anode, cathode with narrow gap, magnet, cathode shield and two independent discharge chambers. This plasma source can be used for cleaning the work-pieces and depositing films with high adhesion between film and substrate. The different gas can be inlet into either discharge chambers. The voltage of planar plasma source has a quadratic relationship with the current. The current increases with the increasing of the
Fig. 2. Ionized current dependence of plasma density.
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G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
Fig. 3. Raman spectra of DLC films.
structure was analyzed by Raman spectroscopy and transmission electron microscope (TEM). The Raman spectra of undoped and doped DLC films are shown in Fig. 3. A broad peak in the range 1200–1600 cm 1 is observed for both the undoped and doped DLC films. This confirms that the films are amorphous. The content of sp3 bonds decreases after metal ion is implanted into DLC films. The structures of Ti+ implanted DLC films were analyzed by TEM. The result shows TiC nanocrystals are formed in DLC film by implanted Ti+ (see Fig. 4). The formation of TiC reduces the co-ordination number of a-C networks by binding carbon atoms into carbide. A reduction of co-ordination number and a decrease of the local carbon atom density result in sp3Ysp2 relaxation of a-C network [5]. Metal implanted into DLC films promotes the graphitization of amorphous DLC matrix, and sp2 content increases in the DLC films. 3.2. Hot filament plasma with magnetic filter cathode arc
ion implantation and enhanced with arc or magnetron sputtering deposition can be performed at the same time, which can not only mix the interface between the film and the substrate, but can also improve the properties of film.
3. Duplex technology 3.1. Metal ion implantation with magnetron sputtering Diamond-like carbon film (DLC film) is a metastable form of amorphous carbon containing a significant fraction of sp3 bonds. DLC films have many properties similar to diamond. The low friction coefficient of DLC film plays a vital role for its industrial application. The nature and properties of the DLC films may be modified by controlling the incorporation of dopants, such as silicon, fluorine, nitrogen and various metals (Ti, Nb, Ta, Cr, W, Al, Cu) [3,4]. Ti-doped DLC films were obtained by Ti ion implanted DLC films synthesized by magnetron sputtering. The film is smooth and uniform, as observed via AFM. The roughness of Ti-doped DLC film is as low as 0.595 nm. The bond
Nitrided steel sufficiently supports the hard coating [6,7], because it exhibits higher hardness than those without nitriding process. The combined technology of plasma nitriding and PVD TiN coating treatment could significantly improve the corrosion resistance of the duplex system [8]. However, there are many duplex coating process carried out in two steps such as TiN coating/nitriding process. Duplex technology of nitriding and TiN coatings was carried out via the combination of hot filament plasma and magnetic filter cathode arc source at the same pressure. The hardness of the surface nitrided layer is 800 HK and the hardness of TiN coating can reach up to 2200 HK. Fig. 5 shows the hardness profile of nitriding sample. The hardness ranges from 800 to 340 HK near the substrate. It can be concluded that the depth of nitriding zone (include diffusion layer) can reach up to 70 Am. Cross-sectional morphology of nitriding and duplex process are shown in Fig. 6. Fig. 6(a) indicates the presence of a continuous white layer about 10 Am in the nitriding sample. The white layer is gN phase analyzed by XRD. Two sublayers, denoted by gN1 and gN2 [9], are formed in the white layer. Fig. 6(b) shows that the
Fig. 4. TEM image and diffraction pattern of Ti-doped DLC films.
G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
Fig. 5. Hardness as a function of distance from the surface for nitriding sample.
thickness of TiN layer is about 10 Am. The continuous white layer gN phase is decomposed to form the black layer. The black layer consisted of a phase and CrN phase by XRD. This is because the bombardment of Ti+ ion would induce a temperature rise in the sample during TiN coating deposition. As a result, gN phase decomposed to a phase and CrN phase. 3.3. Gas ion implantation with cathode arc source CrN and TiN hard coatings have been successfully applied for the improvement of the wear protection, and oxidation and corrosion resistance for machine tools and engineering components. The development of hard coatings to be deposited at low temperature (room temperature) is one of the general interests for basic research, and is of primary importance for industrial applications. Specifically, a large percentage of tools and machine parts are still made of alloyed tool steels or metal alloys. Ion implantation has been shown to improve the mechanical, optical and electrical properties of materials by surface modification. It has been known that the bombardment of penetrated ions not only can induce changes in the structure, but can also mix the interface between the film and the substrate. The purpose of the duplex process of gas ion implantation and cathode arc source is to realize low-temperature (room temperature) deposition technology for hard coatings and
115
Fig. 7. XRD patterns of CrN and TiN coatings.
achieve the structures and properties of those coatings that must be deposited at high temperature. TiN and CrN coatings were deposited on bearing steel of GCr15 in ambient temperature at about 3 Am. The hardness of bearing steel of GCr15 is 61 HRC; then after deposited coatings, the hardness of the samples becomes 61.5 HRC for CrN coating deposited and 59.5 HRC for TiN coating deposited, respectively. Comparing to the hardness of the samples before and after deposited coatings, the change of HRC is small. It is suggested that the change of temperature during deposition is very minimal, which cannot induce the change in the structure of the sample. The Knoop microhardness of the coatings ranges from 1750 to 2000 HK for both CrN and TiN coating. The XRD spectra of CrN and TiN coatings are shown in Fig. 7. Results show that CrN and TiN phases are formed in these coatings, respectively. It is concluded that CrN and TiN hard coatings are achieved via the duplex technology of gas ion implantation and cathode arc source at ambient temperature. Gas ion implantation can also be used for promoting atom diffusion and the growth of coatings.
4. Conclusions The equipment of plasma-ion beam source enhanced deposited is an advanced deposition system that combines
Fig. 6. Micrograph cross-sections of (a) nitriding and (b) TiN coating/nitriding layer.
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G. Li et al. / Surface & Coatings Technology 193 (2005) 112–116
with many advanced plasma sources such as metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source. Through this system, many duplex technologies can be realized, such as ion implantation of metal and gas with low energy, plasma source surface strength and deposition duplex technology, ion implantation enhanced multi-arc deposition technology, planar plasma source enhanced deposition technology. High-quality hard films are achieved through this system by using different duplex technologies.
Acknowledgement This work has been supported by National High-Tech. Program of China (No.2001AA883010).
References [1] T. Bell, H. Dong, Y. Sun, Tribol. Int. 31 (1998) 127. [2] H. Dong, Y. Sun, T. Bell, Surf. Coat. Technol. 90 (1997) 91. [3] Q. Wei, K. Sharma, J. Sankar, J. Narayan, Compos., Part B Eng. 30 (1999) 675. [4] M. Hakovirta, A.M. Peter, B. Taylor, M. Nastasi, He Xiaoming, J. Vac. Sci. Technol., Part A 20 (2002) 638. [5] A.A. Voevodin, M.A. Capano, S.J.P. Laube, M.S. Donley, J.S. Zabinski, Thin Solid Films 298 (1997) 107. [6] H.J. Spies, et al., Surf. Coat. Technol. 74–75 (1995) 178. [7] D.P. Berisov, I.M. Goncharenko, N.N. Koval, Physics (1994) 115. [8] Y. Sun, T. Bell, Mater. Sci. Eng. A1 40 (1991) 419. [9] D.L. Williamson, J.A. Davis, P.J. Wilbur, Surf. Coat. Technol. 103–104 (1998) 178.