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Effect of ion beam implantation on density of DLC prepared by plasma-based ion implantation and deposition
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 242 (2006) 335–337 www.elsevier.com/locate/nimb
Effect of ion beam implantation on density of DLC prepared by plasma-based ion implantation and deposition Y. Oka
a,*
, M. Kirinuki a, T. Suzuki b, M. Yatsuzuka a, K. Yatsui
b
a
b
Graduate School of Engineering, University of Hyogo, Himeji, Japan Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Japan Available online 28 November 2005
Abstract DLC (diamond-like carbon) films were prepared by the hybrid process of plasma-based ion implantation and deposition using acetylene plasma. The hydrogen content in DLC films decreased with the increase of negative pulsed voltage. The residual stress, density and hardness of DLC films had a peak at the negative pulsed voltage of 0 to 5 kV. At 5 to 20 kV, they had a correlation each other and considerably decreased with the increase of negative pulsed voltage. Ó 2005 Published by Elsevier B.V. PACS: 52.77.Dq; 81.15.Jj; 81.15.Gh; 83.85.Rx Keywords: Diamond-like carbon; Plasma-based ion implantation and deposition; Residual stress; Density; Hydrogen content; Hardness
1. Introduction Diamond-like carbon (DLC) films are well known for many superior properties such as a low coefficient of friction, high hardness and chemical inertness [1]. However DLC films produced by the cathode arc or the sputtering deposition, which are common methods to prepare DLC films, have strong residual stress more than several GPa [2–4]. It is known that the local heating (thermal spike) of substrate by ion beam implantation relaxes the residual stress in DLC films [3,5,6]. The authors observed the remarkable reduction of the residual stress of DLC films using a hybrid process of plasma-based ion implantation and deposition [7,8]. If the reduction of the residual stress in DLC films was ascribed to the effect of thermal spike, the density of DLC films should decrease by ion implantation. In this work, we present the effect of ion beam implantation on density and hydrogen content of DLC films pre-
*
Corresponding author. E-mail address: [email protected] (Y. Oka).
0168-583X/$ - see front matter Ó 2005 Published by Elsevier B.V. doi:10.1016/j.nimb.2005.08.203
pared by plasma-based ion implantation and deposition. The hardness of DLC films is also presented. 2. Experimental DLC films were prepared on a silicon wafer by a hybrid process of plasma-based ion implantation and deposition, which has been fully described previously [7–11]. Before coating the sputter-cleaning was done using argon plasma with the negative pulsed voltage of 10 kV. DLC films were prepared using acetylene plasma with the negative pulsed voltage of 0 to 20 kV for carbon ion implantation. The duration of negative pulsed voltage was 5 ls. The peak power, pulse duration and frequency of RF pulse were 300 W, 50 ls and 13.56 MHz, respectively. The repetition rate of both pulse was 1 kHz. The gas pressure was 0.5 Pa. The thickness of DLC film was about 0.5 lm for measurement of density and hydrogen content, while about 1 lm for measurement of hardness. The residual stress of DLC films was determined from the curvature of its substrate (quartz grass plate) using StoneyÕs equation. The density of DLC films was determined from the area density measured by RBS and the film
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Y. Oka et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 335–337
thickness measured by stylus profilometer. The hydrogen content was measured by ERDA. The hardness was measured by nano-indentation tester (ENT1100, ELIONIX). 3. Results and discussion Fig. 1 shows the residual stress of DLC films as a function of negative pulsed voltage, where the deposition time was 2 h. As seen in Fig. 1, the compressive stress is about 0.46 GPa without the negative pulsed voltage. The compressive stress increases with the increase of negative pulsed voltage and reaches the maximum value of about 1.7 GPa at 1 kV. When the negative pulsed voltage exceeds 1 kV, the compressive stress considerably decreases with the increase of negative pulsed voltage and reduces to 0.16 GPa at 20 kV. Fig. 2 shows the density of DLC films as a function of negative pulsed voltage. As seen in Fig. 2, the density is about 2.0 g/cm3 without negative pulsed voltage. The density slightly increases with the increase of negative pulsed voltage and reaches the maximum value of about 2.5
Compressive stress (GPa)
2
1
0
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 1. Compressive stress of DLC films as a function of negative pulsed voltage.
g/cm3 at 5 kV. When the negative pulsed voltage exceeds 5 kV, the density decreases with the increase of negative pulsed voltage and reduces to 2.0 g/cm3 at 20 kV. These results indicate that the reduction of the compressive stress at the pulsed voltage from 5 to 20 kV is resulted from the thermal spike effect of ion beam energy. At the higher negative pulsed voltage region above 5 kV, the residual stress is correlation with the density. On the other hand, at the lower negative pulsed voltage below 5 kV, the residual stress is little dependent on the density. Fig. 3 shows the hydrogen content of DLC films as a function of negative pulsed voltage. As seen in Fig. 3, the hydrogen content is about 35 at.% without negative pulsed voltage. The hydrogen content considerably decreases with the increase of negative pulsed voltage and reduces to 18 at.% at 5 kV. At the pulsed voltage from 5 to 20 kV, the hydrogen content is about 18 at.% and little dependent on the negative pulsed voltage. The reduction of hydrogen content in DLC film at the negative pulsed voltage from 0 to 5 kV may be ascribed to the change in structure and bonding state of DLC films. Therefore, the residual stress may be little correlation with the density at the negative pulsed voltage from 0 to 5 kV. Fig. 4 shows the hardness of DLC films as a function of negative pulsed voltage, where the maximum load was 200 mg, and the maximum displacement of indenter was 1/10 or less of the thickness of DLC films. As seen in Fig. 4, the hardness is about 12.4 GPa without negative pulsed voltage. The hardness considerably increases with the increase of negative pulsed voltage and increases to about 22.1 GPa at 3 kV. When the negative pulsed voltage exceeds 3 kV, the density considerably decreases with the increase of negative pulsed voltage, reduces to 14.1 GPa at 20 kV. The increase and decrease in the hardness of DLC films is similar to one of the density, indicating that the hardness depends mainly on the density. The reduction of the observed hardness at 5 kV or less should be ascribed to the increase of the hydrogen content of DLC films. 50
3
H content (at%)
Density (g/cm3)
40
2
30
20
1 10
0 0
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 2. Density of DLC films as a function of negative pulsed voltage.
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 3. Hydrogen content of DLC films as a function of negative pulsed voltage.
Y. Oka et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 335–337
The hydrogen content decreased with the increase of negative pulsed voltage, reduced from 35 to 18 at.%. The increase and decrease of the hardness of DLC films is similar to one of the density and the hardness changed from 12.4 to 22.1 GPa.
25
20
Hardness (GPa)
337
15
Acknowledgements 10
This work was supported by the Cooperation of Innovative Technology and Advanced Research in Evolutional Area (City area) and Hyogo Science and Technology Association.
5 Maximum load: 200 mg 0
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 4. Hardness of DLC films as a function of negative pulsed voltage, where the film thickness is about 1 lm, the maximum load is 200 mg, and the maximum displacement of indenter is 1/10 or less of the thickness of DLC films.
4. Conclusion DLC films were prepared using acetylene plasma by a hybrid process of plasma-based ion implantation and deposition. The compressive stress had the maximum value at 1 kV, and considerably decreased with the increase of negative pulsed voltage and reduces to 0.16 GPa at 20 kV. The density slightly increased with the increase of negative pulsed voltage and reaches the maximum value at 5 kV and decreased with the increase of negative pulsed voltage. The observed density indicates that the reduction of the residual stress at 5 to 20 kV may be resulted from the thermal spike effect of ion beam energy.
References [1] J. Robertson, Surf. Coat. Technol. 50 (1992) 185. [2] D.R. McKenzie, D. Muller, B.A. Pailthorpe, Phys. Rev. Lett. 67 (1991) 773. [3] P.J. Fallon, V.S. Veerasamy, C.A. Davis, J. Robertson, G.A.J. Amaratunga, W.I. Milne, J. Koskinen, Phys. Rev. B 48 (1993) 4777. [4] J.W. Ager III, S. Anders, A. Anders, I.G. Brown, Appl. Phys. Lett. 66 (1995) 3444. [5] M.M.M. Bilek, D.R. McKenzie, R.N. Tarrant, S.H.N. Lim, D.G. McCulloch, Surf. Coat. Technol. 156 (2002) 136. [6] M.M.M. Bilek, R.N. Tarrant, D.R. McKenzie, S.H.N. Lim, D.G. McCulloch, IEEE Trans. Plasma Sci. 31 (2003) 939. [7] Y. Oka, M. Tao, Y. Nishimura, K. Azuma, M. Yatsuzuka, Nucl. Instr. and Meth. B 206 (2003) 700. [8] Y. Oka, M. Kirinuki, Y. Nishimura, K. Azuma, E. Fujiwara, M. Yatsuzuka, Surf. Coat. Technol. 186 (2004) 141. [9] Y. Nishimura, A. Chayahara, Y. Horino, M. Yatuzuka, Surf. Coat. Technol. 156 (2002) 50. [10] Y. Nishimura, Y. Oka, H. Akamatsu, K. Azuma, M. Yatsuzuka, Nucl. Instr. and Meth. B 206 (2003) 696. [11] Y. Oka, Y. Nishimura, M. Yatsuzuka, Vacuum 73 (2004) 541.
Nuclear Instruments and Methods in Physics Research B 242 (2006) 335–337 www.elsevier.com/locate/nimb
Effect of ion beam implantation on density of DLC prepared by plasma-based ion implantation and deposition Y. Oka
a,*
, M. Kirinuki a, T. Suzuki b, M. Yatsuzuka a, K. Yatsui
b
a
b
Graduate School of Engineering, University of Hyogo, Himeji, Japan Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Japan Available online 28 November 2005
Abstract DLC (diamond-like carbon) films were prepared by the hybrid process of plasma-based ion implantation and deposition using acetylene plasma. The hydrogen content in DLC films decreased with the increase of negative pulsed voltage. The residual stress, density and hardness of DLC films had a peak at the negative pulsed voltage of 0 to 5 kV. At 5 to 20 kV, they had a correlation each other and considerably decreased with the increase of negative pulsed voltage. Ó 2005 Published by Elsevier B.V. PACS: 52.77.Dq; 81.15.Jj; 81.15.Gh; 83.85.Rx Keywords: Diamond-like carbon; Plasma-based ion implantation and deposition; Residual stress; Density; Hydrogen content; Hardness
1. Introduction Diamond-like carbon (DLC) films are well known for many superior properties such as a low coefficient of friction, high hardness and chemical inertness [1]. However DLC films produced by the cathode arc or the sputtering deposition, which are common methods to prepare DLC films, have strong residual stress more than several GPa [2–4]. It is known that the local heating (thermal spike) of substrate by ion beam implantation relaxes the residual stress in DLC films [3,5,6]. The authors observed the remarkable reduction of the residual stress of DLC films using a hybrid process of plasma-based ion implantation and deposition [7,8]. If the reduction of the residual stress in DLC films was ascribed to the effect of thermal spike, the density of DLC films should decrease by ion implantation. In this work, we present the effect of ion beam implantation on density and hydrogen content of DLC films pre-
*
Corresponding author. E-mail address: [email protected] (Y. Oka).
0168-583X/$ - see front matter Ó 2005 Published by Elsevier B.V. doi:10.1016/j.nimb.2005.08.203
pared by plasma-based ion implantation and deposition. The hardness of DLC films is also presented. 2. Experimental DLC films were prepared on a silicon wafer by a hybrid process of plasma-based ion implantation and deposition, which has been fully described previously [7–11]. Before coating the sputter-cleaning was done using argon plasma with the negative pulsed voltage of 10 kV. DLC films were prepared using acetylene plasma with the negative pulsed voltage of 0 to 20 kV for carbon ion implantation. The duration of negative pulsed voltage was 5 ls. The peak power, pulse duration and frequency of RF pulse were 300 W, 50 ls and 13.56 MHz, respectively. The repetition rate of both pulse was 1 kHz. The gas pressure was 0.5 Pa. The thickness of DLC film was about 0.5 lm for measurement of density and hydrogen content, while about 1 lm for measurement of hardness. The residual stress of DLC films was determined from the curvature of its substrate (quartz grass plate) using StoneyÕs equation. The density of DLC films was determined from the area density measured by RBS and the film
336
Y. Oka et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 335–337
thickness measured by stylus profilometer. The hydrogen content was measured by ERDA. The hardness was measured by nano-indentation tester (ENT1100, ELIONIX). 3. Results and discussion Fig. 1 shows the residual stress of DLC films as a function of negative pulsed voltage, where the deposition time was 2 h. As seen in Fig. 1, the compressive stress is about 0.46 GPa without the negative pulsed voltage. The compressive stress increases with the increase of negative pulsed voltage and reaches the maximum value of about 1.7 GPa at 1 kV. When the negative pulsed voltage exceeds 1 kV, the compressive stress considerably decreases with the increase of negative pulsed voltage and reduces to 0.16 GPa at 20 kV. Fig. 2 shows the density of DLC films as a function of negative pulsed voltage. As seen in Fig. 2, the density is about 2.0 g/cm3 without negative pulsed voltage. The density slightly increases with the increase of negative pulsed voltage and reaches the maximum value of about 2.5
Compressive stress (GPa)
2
1
0
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 1. Compressive stress of DLC films as a function of negative pulsed voltage.
g/cm3 at 5 kV. When the negative pulsed voltage exceeds 5 kV, the density decreases with the increase of negative pulsed voltage and reduces to 2.0 g/cm3 at 20 kV. These results indicate that the reduction of the compressive stress at the pulsed voltage from 5 to 20 kV is resulted from the thermal spike effect of ion beam energy. At the higher negative pulsed voltage region above 5 kV, the residual stress is correlation with the density. On the other hand, at the lower negative pulsed voltage below 5 kV, the residual stress is little dependent on the density. Fig. 3 shows the hydrogen content of DLC films as a function of negative pulsed voltage. As seen in Fig. 3, the hydrogen content is about 35 at.% without negative pulsed voltage. The hydrogen content considerably decreases with the increase of negative pulsed voltage and reduces to 18 at.% at 5 kV. At the pulsed voltage from 5 to 20 kV, the hydrogen content is about 18 at.% and little dependent on the negative pulsed voltage. The reduction of hydrogen content in DLC film at the negative pulsed voltage from 0 to 5 kV may be ascribed to the change in structure and bonding state of DLC films. Therefore, the residual stress may be little correlation with the density at the negative pulsed voltage from 0 to 5 kV. Fig. 4 shows the hardness of DLC films as a function of negative pulsed voltage, where the maximum load was 200 mg, and the maximum displacement of indenter was 1/10 or less of the thickness of DLC films. As seen in Fig. 4, the hardness is about 12.4 GPa without negative pulsed voltage. The hardness considerably increases with the increase of negative pulsed voltage and increases to about 22.1 GPa at 3 kV. When the negative pulsed voltage exceeds 3 kV, the density considerably decreases with the increase of negative pulsed voltage, reduces to 14.1 GPa at 20 kV. The increase and decrease in the hardness of DLC films is similar to one of the density, indicating that the hardness depends mainly on the density. The reduction of the observed hardness at 5 kV or less should be ascribed to the increase of the hydrogen content of DLC films. 50
3
H content (at%)
Density (g/cm3)
40
2
30
20
1 10
0 0
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 2. Density of DLC films as a function of negative pulsed voltage.
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 3. Hydrogen content of DLC films as a function of negative pulsed voltage.
Y. Oka et al. / Nucl. Instr. and Meth. in Phys. Res. B 242 (2006) 335–337
The hydrogen content decreased with the increase of negative pulsed voltage, reduced from 35 to 18 at.%. The increase and decrease of the hardness of DLC films is similar to one of the density and the hardness changed from 12.4 to 22.1 GPa.
25
20
Hardness (GPa)
337
15
Acknowledgements 10
This work was supported by the Cooperation of Innovative Technology and Advanced Research in Evolutional Area (City area) and Hyogo Science and Technology Association.
5 Maximum load: 200 mg 0
0
-5
-10
-15
-20
Negative pulsed voltage (kV) Fig. 4. Hardness of DLC films as a function of negative pulsed voltage, where the film thickness is about 1 lm, the maximum load is 200 mg, and the maximum displacement of indenter is 1/10 or less of the thickness of DLC films.
4. Conclusion DLC films were prepared using acetylene plasma by a hybrid process of plasma-based ion implantation and deposition. The compressive stress had the maximum value at 1 kV, and considerably decreased with the increase of negative pulsed voltage and reduces to 0.16 GPa at 20 kV. The density slightly increased with the increase of negative pulsed voltage and reaches the maximum value at 5 kV and decreased with the increase of negative pulsed voltage. The observed density indicates that the reduction of the residual stress at 5 to 20 kV may be resulted from the thermal spike effect of ion beam energy.
References [1] J. Robertson, Surf. Coat. Technol. 50 (1992) 185. [2] D.R. McKenzie, D. Muller, B.A. Pailthorpe, Phys. Rev. Lett. 67 (1991) 773. [3] P.J. Fallon, V.S. Veerasamy, C.A. Davis, J. Robertson, G.A.J. Amaratunga, W.I. Milne, J. Koskinen, Phys. Rev. B 48 (1993) 4777. [4] J.W. Ager III, S. Anders, A. Anders, I.G. Brown, Appl. Phys. Lett. 66 (1995) 3444. [5] M.M.M. Bilek, D.R. McKenzie, R.N. Tarrant, S.H.N. Lim, D.G. McCulloch, Surf. Coat. Technol. 156 (2002) 136. [6] M.M.M. Bilek, R.N. Tarrant, D.R. McKenzie, S.H.N. Lim, D.G. McCulloch, IEEE Trans. Plasma Sci. 31 (2003) 939. [7] Y. Oka, M. Tao, Y. Nishimura, K. Azuma, M. Yatsuzuka, Nucl. Instr. and Meth. B 206 (2003) 700. [8] Y. Oka, M. Kirinuki, Y. Nishimura, K. Azuma, E. Fujiwara, M. Yatsuzuka, Surf. Coat. Technol. 186 (2004) 141. [9] Y. Nishimura, A. Chayahara, Y. Horino, M. Yatuzuka, Surf. Coat. Technol. 156 (2002) 50. [10] Y. Nishimura, Y. Oka, H. Akamatsu, K. Azuma, M. Yatsuzuka, Nucl. Instr. and Meth. B 206 (2003) 696. [11] Y. Oka, Y. Nishimura, M. Yatsuzuka, Vacuum 73 (2004) 541.