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Effects of boron contents on microstructures and microhardness in CrxAlyN films synthesized by cathodic arc method
Surface & Coatings Technology 201 (2006) 1348 – 1351 www.elsevier.com/locate/surfcoat
Effects of boron contents on microstructures and microhardness in CrxAlyN films synthesized by cathodic arc method T. Sato a , T. Yamamoto a , H. Hasegawa b,⁎, T. Suzuki a a
Center for Science of Environment, Resource and Energy, Keio University 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan b Mechanical Engineering, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530, Japan Received 2 May 2005; accepted in revised form 30 January 2006 Available online 17 April 2006
Abstract CrxAlyBzN films were synthesized by the cathodic arc method, using CrxAlyBz alloy cathode with differing z values from 0 to 0.10 and investigated with respect to crystal structures, lattice parameters and microhardness. The microhardness of CrxAlyBzN increased from 27 (z = 0) to 33 GPa (z = 0.10). The lattice parameters of CrxAlyBzN decreased from 0.413 (z = 0) to 0.410 nm (z = 0.10), keeping the cubic structure. The columnar structure of CrxAlyBzN disappeared and grain size decreased with incorporations of B atoms. In this study, CrxAlyBzN films were characterized by X-ray and electron microscopy analysis and the relationship between microstructure and microhardness was discussed as a function of B contents. © 2006 Elsevier B.V. All rights reserved. Keywords: (Cr,Al,B)N; Microhardness; Microstructure
1. Introduction It is well recognized that incorporation of Al atoms into binary nitride such as TiN and CrN leads to phase transformation from cubic to hexagonal structures at certain Al contents [1,2]. The behaviors of mechanical and chemical properties in TixAlyN at the transformation region are attractive interests with regard to applying to cutting tools and protect wear. For instance, the microhardness of TixAlyN films changed from 20 GPa to 32 GPa, while lattice parameters decreased from 0.423 down to 0.417 nm with increasing up to y = 0.6 [3]. In addition, Ikeda and Satoh [4] reported that flank wear and thermal stability of TixAlyN were improved comparing to TiN due to diffusion of Al at elevated temperature. CrxAlyN have been gained much attention for alternative to TixAlyN because maximum AlN solubility in cubic CrN is higher compared with TiN [5]. Makino et al. reported that crystal structure of CrxAlyN prepared by magnetron sputtering changed from NaCl to wurtzite structure between y = 0.7 and 0.8. CrxAlyN exhibited the maximum hardness values of 27 GPa, corresponding to shrinkage of lattice at y = 0.6 [6,7]. ⁎ Corresponding author. Tel.: +81 86 251 8067; fax: +81 86 251 8266. E-mail address: [email protected] (H. Hasegawa). 0257-8972/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2006.01.068
Moreover, oxidation resistance of Cr0.4Al0.6N was superior to Cr0.3Al0.7N between 800 and 900 °C, where similar behavior of cubic-type TixAlyN was confirmed in previous works [8,9]. On the other hand, PVD metastable films have been developed by embedding various atoms and these achievements improved original properties of transition metal nitride [10]. Recently, some researchers reported that the additions of boron into binary and ternary nitride provided advantages to enhance hardness and lubricant properties in Ti–B–N [11], Cr–B–N [12], Al–B–N [13] and Ti–Al–B–N [14]. In this paper, CrxAlyBzN films were prepared by cathodic arc method, focusing on additions of B atoms into cubic CrxAlyN with Cr/Al metal ratios around phase transformation region. The crystal structure, lattice parameters and morphology were investigated based on X-ray and electron microscopy analysis and the correlations between microhardness and microstructure were discussed as a function of B contents. 2. Experiments Cathodic arc method is a specialized technique which can realize non-thermodynamically condition and create metastable films under nitrogen plasma. CrxAlyBzN films were deposited on mirror-polished cemented carbide (WC-Co)
T. Sato et al. / Surface & Coatings Technology 201 (2006) 1348–1351
(a)
35
Microhardness (GPa)
substrates, stainless steel (SUS304) substrates, and Si (100) wafers by cathodic arc method using CrxAlyBz cemented alloy cathode with x, y and z range: 0.36 ≤ x ≤ 0.40, 0.54 ≤ y ≤ 0.60 and 0 ≤ z ≤ 0.10. The substrates were cleaned and degreased by successive rinsing in ultrasonic baths of acetone and inserted into the chamber. Before deposition, the substrates were etched for 10min in argon circumstance under pressure of 6.6Pa at substrate bias of 1000V. Then, the cathodes were discharged for 3min with current 100A under a pressure of ∼ 4 × 10− 4 Pa and the substrates were biased at 700 V. The CrxAlyBzN films were deposited in a nitrogen atmosphere at a pressure of 3.3Pa with an arc current of 100 A at 20 V for 20 min. Films thickness was ∼6 μm for characterizations. The compositions of the films were measured by radiofrequency glow discharge optical emission spectroscope (rfGDOES). Microhardness was evaluated by the conventional micro-Vickers test with a load of 0.5 N. Crystal structures and lattice parameters of films were evaluated by the X-ray
1349
30 25 20 ~ ~
0
0.02
0.04
0.06
0.08
0.10
Boron contents: z Fig. 2. Changes in microhardness of CrxAlyBzN films against B contents ranging from z = 0 to 0.10. The hardness values increased from 27 to 33GPa with increasing B contents up to 0.10.
diffraction (XRD) method using Cu Kα radiation with 50kV and 100 mA. The surface and cross-sectional morphology was observed by scanning and transmission electron microscope (SEM and TEM). 3. Results and discussion 3.1. GDOES analysis
Intensity (a.u.)
Fe N Al Cr Ni
C
H 0
10
20
30
40
50
60
Fig. 1 indicates rf-GDOES qualitative depth profiles of CrxAlyBzN films on SUS304 substrates with z = 0 (a), 0.04 (b) and 0.10 (c), respectively. As can been observed in the GDOES profile, the signal intensities were constant along the depth direction. Particularly, the Boron signal gradually became intensive with increasing in z value of CrxAlyBz cathode.
Sputtering time (s)
3.2. Microhardness
(b)
Fig. 2 shows the changes in microhardness of CrxAlyBzN against B contents z from 0 to 0.10. The microhardness of Cr0.4Al0.6N (z = 0) was 27 GPa and gradually increased up to
Intensity (a.u.)
Fe N Al
c-CrXAlYBZN
Cr
0
10
20
Ni
C
B 30
40
50
60
70
(1 1 1)
80
Sputtering time (s)
(c) Intensity (a.u.)
Fe N
Boron
(2 0 0)
contents: z
X-ray intensity (a.u.)
H
c-CrXAlYBZN
0.10 0.08 0.06 0.04
Al H 0
10
Cr
C
B 20
0
Ni 30
30
40
50
60
70
80
35
40
45
50
Diffraction angle: 2θ (degrees)
Sputtering time (s) Fig. 1. The rf-GDOES depth profiles of CrxAlyBzN films with (a) z = 0, (b) z = 0.04 and (c) z = 0.10, respectively.
Fig. 3. X-ray diffraction patterns of CrxAlyBzN films. Both peaks of (111) and (200) planes shifted to higher diffraction angles in comparison with each position of Cr0.4Al0.6N films. Here, c- represents cubic structure.
1350
T. Sato et al. / Surface & Coatings Technology 201 (2006) 1348–1351
Lattice parameters (nm)
0.420
20GPa (TiN value) to 40GPa, and Rebholz et al. [16] indicated that Ti–Al–B–N films revealed 37 GPa. Hence, it was confirmed that similar improvements were obtained in CrxAly BzN films.
0.415 0.410
(a)
0.405 ~ ~
0
0.02
0.04
0.06
0.08
0.10
Boron contents: z Fig. 4. Changes in lattice parameter of CrxAlyBzN films. The lattice parameters CrxAlyBzN decreased from 0.413 to 0.413nm with addition of B contents.
33 GPa at z = 0.10. It is reported that additions of B atoms to Tibased nitride films enhance their original hardness. Aouadi et al. [15] reported that the hardness of Ti–B–N increased from
(a)
200 nm
(b)
5 μm
(b)
200 nm
(c) 5 μm
(c)
5 μm Fig. 5. Cross-sectional SEM images of CrxAlyBzN films with (a) z = 0, (b) z = 0.04 and (c) z = 0.10, respectively.
200 nm Fig. 6. Plan-view TEM micrographs of CrxAlyBzN films at (a) z = 0, (b) z = 0.04 and (c) z = 0.10, respectively.
T. Sato et al. / Surface & Coatings Technology 201 (2006) 1348–1351
3.3. Crystal structures Fig. 3 shows the XRD patterns from CrxAlyBzN with z = 0, 0.04, 0.06, 0.08 and 0.10, respectively. Cr0.4Al0.6N had NaCl structure and its unit cell was smaller compared with CrN due to substitutions of Al for Cr atoms [7]. With increasing B contents z from 0 to 0.10, the (100) peak position shifted to higher diffraction angles from 37.78° to 38.00°, while the diffraction angle of (200) plane changed from 44.02° to 44.31°. It is reported that additions of B atoms resulted in phase segregation under non-equilibrium nitrogen plasma [11,14,15]. Kawate et al. [9] indicated that Cr–B–N films were comprised of some binary phase such as Cr2N CrN, Cr2B, and BN. Fig. 4 shows the changes in lattice parameters of CrxAlyBzN films. The lattice parameters decreased from 0.413 nm at z = 0 to 0.410 nm at z = 0.10 keeping the cubic structure. It is well known that lattice shrinkage or expansion in Ti-based nitride films is related with ionic and atomic radius of additional elements. For instance, incorporation of smaller atoms such as Al, Cr, and W led to decrease in lattice parameters of TiN [17]. Another example, lattice parameters of TixZryN changed from 0.423 nm to 0.458nm with increasing Zr contents [18]. It is noticed that lattice contraction of CrxAlyN was promoted by dope of boron as similar to the cases of metal element. 3.4. Morphology Fig. 5(a)–(c) show cross-sectional micrographs of CrxAly BzN with z = 0, 0.04 and 0.10, respectively. Cr0.4Al0.6N films had typical columnar structure, which gradually disappeared from z = 0.04 to z = 0.10. Holzschuh [19] reported that the morphology of TiN deposited by CVD method varied from coarse grains to micro-crystallites by incorporations of B atoms. Fig. 6(a)–(c) show TEM images of CrxAlyBzN films with z = 0, 0.04 and 0.10, respectively. Corresponding with SEM observation results, the grain sizes and shapes changed drastically as a function of B contents. The grain size of Cr0.4Al0.6N was approximately 100–200nm and grain boundaries were definite. While the grain size of CrxAlyBzN decreased down to 50 nm ranging from z = 0.04 to 0.10. 4. Summary CrxAlyBzN films with differing B contents were synthesized by the cathodic arc method and crystal structures, lattice parameters and microhardness were analyzed by X-ray and electron microscopy with respect to B contents. The obtained
1351
results are summarized as follows. The microhardness of CrxAlyBzN monotonously increased from 27 GPa (z = 0) up to 33GPa (z = 0.10), therefore higher hardness was obtained by the addition of B atoms. The XRD patterns showed that the crystal structures of CrxAlyBzN were kept the NaCl structures with all z values and the lattice parameters of CrxAlyBzN films decreased from 0.413 nm at z = 0 down to 0.410 nm at z = 0.10, according to ratios of z value. The columnar structure of CrxAlyBzN disappeared and grain size decreased in comparison with Cr0.4Al0.6N films. Acknowledgments This work was supported by Grant-in-Aid for the 21st Century COE program “KEIO Life-Conjugated Chemistry” and Japan Society for the Promotion of Science from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. References [1] U. Wahlström, L. Hultman, J.E. Sundgren, F. Adibi, I. Petrov, J.E. Greene, Thin Solid Films 235 (1993) 62. [2] A. Sugishima, H. Kajioka, Y. Makino, Surf. Coat. Technol. 97 (1997) 590. [3] A. Kimura, H. Hasegawa, K. Yamada, T. Suzuki, Surf. Coat. Technol. 120–121 (1999) 439. [4] T. Ikeda, H. Satoh, Thin Solid Films 195 (1991) 99. [5] Y. Makino, ISIJ Int. 38 (1998) 925. [6] Y. Makino, K. Nogi, Surf. Coat. Technol. 98 (1998) 1008. [7] M. Kawate, A. Kimura, T. Suzuki, J. Vac. Sci. Technol., A, Vac. Surf. Films 20 (2002) 569. [8] M. Kawate, A.K. Hasimoto, T. Suzuki, Surf. Coat. Technol. 165 (2003) 163. [9] M. Kawate, H. Hasegawa, A.K. Hashimoto, T. Suzuki, Proceedings of 3rd International Conference on the Coatings in Manuf. Eng., Greece, 2002, p. 343. [10] J. Musil, Surf. Coat. Technol. 125 (2000) 322. [11] M.A. Baker, T.P. Mollart, P.N. Gibson, W. Gissler, J. Vac. Sci. Technol., A, Vac. Surf. Films 15 (1997) 284. [12] S.M. Aouadi, F. Namavar, E. Tobin, N. Finnegan, R.T. Haasch, S.L. Rohde, J. Appl. Phys. 91 (2002) 1040. [13] M. Witthaut, R. Cremer, K. Reichert, D. Neuschütz, Thin Solid Films 377–378 (2000) 478. [14] C. Rebholz, H. Ziegele, A. Leyland, A. Matthews, J. Vac. Sci. Technol., A, Vac. Surf. Films 16 (1998) 2851. [15] S.M. Aouadi, J.A. Chaldek, F. Namavar, N. Finnegan, S.L. Rohde, J. Vac. Sci. Technol., B 20 (5) (2002) 1967. [16] C. Rebholz, A. Leyland, M. Matthews, Thin Solid Films 343–344 (1999) 242. [17] H. Hasegawa, T. Suzuki, Surf. Coat. Technol. 188–189 (2004) 234. [18] H. Hasegawa, A. Kimura, T. Suzuki, Surf. Coat. Technol. 132 (2000) 76. [19] H. Holzschuh, Thin Solid Films 469–470 (2004) 92.
Effects of boron contents on microstructures and microhardness in CrxAlyN films synthesized by cathodic arc method T. Sato a , T. Yamamoto a , H. Hasegawa b,⁎, T. Suzuki a a
Center for Science of Environment, Resource and Energy, Keio University 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan b Mechanical Engineering, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530, Japan Received 2 May 2005; accepted in revised form 30 January 2006 Available online 17 April 2006
Abstract CrxAlyBzN films were synthesized by the cathodic arc method, using CrxAlyBz alloy cathode with differing z values from 0 to 0.10 and investigated with respect to crystal structures, lattice parameters and microhardness. The microhardness of CrxAlyBzN increased from 27 (z = 0) to 33 GPa (z = 0.10). The lattice parameters of CrxAlyBzN decreased from 0.413 (z = 0) to 0.410 nm (z = 0.10), keeping the cubic structure. The columnar structure of CrxAlyBzN disappeared and grain size decreased with incorporations of B atoms. In this study, CrxAlyBzN films were characterized by X-ray and electron microscopy analysis and the relationship between microstructure and microhardness was discussed as a function of B contents. © 2006 Elsevier B.V. All rights reserved. Keywords: (Cr,Al,B)N; Microhardness; Microstructure
1. Introduction It is well recognized that incorporation of Al atoms into binary nitride such as TiN and CrN leads to phase transformation from cubic to hexagonal structures at certain Al contents [1,2]. The behaviors of mechanical and chemical properties in TixAlyN at the transformation region are attractive interests with regard to applying to cutting tools and protect wear. For instance, the microhardness of TixAlyN films changed from 20 GPa to 32 GPa, while lattice parameters decreased from 0.423 down to 0.417 nm with increasing up to y = 0.6 [3]. In addition, Ikeda and Satoh [4] reported that flank wear and thermal stability of TixAlyN were improved comparing to TiN due to diffusion of Al at elevated temperature. CrxAlyN have been gained much attention for alternative to TixAlyN because maximum AlN solubility in cubic CrN is higher compared with TiN [5]. Makino et al. reported that crystal structure of CrxAlyN prepared by magnetron sputtering changed from NaCl to wurtzite structure between y = 0.7 and 0.8. CrxAlyN exhibited the maximum hardness values of 27 GPa, corresponding to shrinkage of lattice at y = 0.6 [6,7]. ⁎ Corresponding author. Tel.: +81 86 251 8067; fax: +81 86 251 8266. E-mail address: [email protected] (H. Hasegawa). 0257-8972/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2006.01.068
Moreover, oxidation resistance of Cr0.4Al0.6N was superior to Cr0.3Al0.7N between 800 and 900 °C, where similar behavior of cubic-type TixAlyN was confirmed in previous works [8,9]. On the other hand, PVD metastable films have been developed by embedding various atoms and these achievements improved original properties of transition metal nitride [10]. Recently, some researchers reported that the additions of boron into binary and ternary nitride provided advantages to enhance hardness and lubricant properties in Ti–B–N [11], Cr–B–N [12], Al–B–N [13] and Ti–Al–B–N [14]. In this paper, CrxAlyBzN films were prepared by cathodic arc method, focusing on additions of B atoms into cubic CrxAlyN with Cr/Al metal ratios around phase transformation region. The crystal structure, lattice parameters and morphology were investigated based on X-ray and electron microscopy analysis and the correlations between microhardness and microstructure were discussed as a function of B contents. 2. Experiments Cathodic arc method is a specialized technique which can realize non-thermodynamically condition and create metastable films under nitrogen plasma. CrxAlyBzN films were deposited on mirror-polished cemented carbide (WC-Co)
T. Sato et al. / Surface & Coatings Technology 201 (2006) 1348–1351
(a)
35
Microhardness (GPa)
substrates, stainless steel (SUS304) substrates, and Si (100) wafers by cathodic arc method using CrxAlyBz cemented alloy cathode with x, y and z range: 0.36 ≤ x ≤ 0.40, 0.54 ≤ y ≤ 0.60 and 0 ≤ z ≤ 0.10. The substrates were cleaned and degreased by successive rinsing in ultrasonic baths of acetone and inserted into the chamber. Before deposition, the substrates were etched for 10min in argon circumstance under pressure of 6.6Pa at substrate bias of 1000V. Then, the cathodes were discharged for 3min with current 100A under a pressure of ∼ 4 × 10− 4 Pa and the substrates were biased at 700 V. The CrxAlyBzN films were deposited in a nitrogen atmosphere at a pressure of 3.3Pa with an arc current of 100 A at 20 V for 20 min. Films thickness was ∼6 μm for characterizations. The compositions of the films were measured by radiofrequency glow discharge optical emission spectroscope (rfGDOES). Microhardness was evaluated by the conventional micro-Vickers test with a load of 0.5 N. Crystal structures and lattice parameters of films were evaluated by the X-ray
1349
30 25 20 ~ ~
0
0.02
0.04
0.06
0.08
0.10
Boron contents: z Fig. 2. Changes in microhardness of CrxAlyBzN films against B contents ranging from z = 0 to 0.10. The hardness values increased from 27 to 33GPa with increasing B contents up to 0.10.
diffraction (XRD) method using Cu Kα radiation with 50kV and 100 mA. The surface and cross-sectional morphology was observed by scanning and transmission electron microscope (SEM and TEM). 3. Results and discussion 3.1. GDOES analysis
Intensity (a.u.)
Fe N Al Cr Ni
C
H 0
10
20
30
40
50
60
Fig. 1 indicates rf-GDOES qualitative depth profiles of CrxAlyBzN films on SUS304 substrates with z = 0 (a), 0.04 (b) and 0.10 (c), respectively. As can been observed in the GDOES profile, the signal intensities were constant along the depth direction. Particularly, the Boron signal gradually became intensive with increasing in z value of CrxAlyBz cathode.
Sputtering time (s)
3.2. Microhardness
(b)
Fig. 2 shows the changes in microhardness of CrxAlyBzN against B contents z from 0 to 0.10. The microhardness of Cr0.4Al0.6N (z = 0) was 27 GPa and gradually increased up to
Intensity (a.u.)
Fe N Al
c-CrXAlYBZN
Cr
0
10
20
Ni
C
B 30
40
50
60
70
(1 1 1)
80
Sputtering time (s)
(c) Intensity (a.u.)
Fe N
Boron
(2 0 0)
contents: z
X-ray intensity (a.u.)
H
c-CrXAlYBZN
0.10 0.08 0.06 0.04
Al H 0
10
Cr
C
B 20
0
Ni 30
30
40
50
60
70
80
35
40
45
50
Diffraction angle: 2θ (degrees)
Sputtering time (s) Fig. 1. The rf-GDOES depth profiles of CrxAlyBzN films with (a) z = 0, (b) z = 0.04 and (c) z = 0.10, respectively.
Fig. 3. X-ray diffraction patterns of CrxAlyBzN films. Both peaks of (111) and (200) planes shifted to higher diffraction angles in comparison with each position of Cr0.4Al0.6N films. Here, c- represents cubic structure.
1350
T. Sato et al. / Surface & Coatings Technology 201 (2006) 1348–1351
Lattice parameters (nm)
0.420
20GPa (TiN value) to 40GPa, and Rebholz et al. [16] indicated that Ti–Al–B–N films revealed 37 GPa. Hence, it was confirmed that similar improvements were obtained in CrxAly BzN films.
0.415 0.410
(a)
0.405 ~ ~
0
0.02
0.04
0.06
0.08
0.10
Boron contents: z Fig. 4. Changes in lattice parameter of CrxAlyBzN films. The lattice parameters CrxAlyBzN decreased from 0.413 to 0.413nm with addition of B contents.
33 GPa at z = 0.10. It is reported that additions of B atoms to Tibased nitride films enhance their original hardness. Aouadi et al. [15] reported that the hardness of Ti–B–N increased from
(a)
200 nm
(b)
5 μm
(b)
200 nm
(c) 5 μm
(c)
5 μm Fig. 5. Cross-sectional SEM images of CrxAlyBzN films with (a) z = 0, (b) z = 0.04 and (c) z = 0.10, respectively.
200 nm Fig. 6. Plan-view TEM micrographs of CrxAlyBzN films at (a) z = 0, (b) z = 0.04 and (c) z = 0.10, respectively.
T. Sato et al. / Surface & Coatings Technology 201 (2006) 1348–1351
3.3. Crystal structures Fig. 3 shows the XRD patterns from CrxAlyBzN with z = 0, 0.04, 0.06, 0.08 and 0.10, respectively. Cr0.4Al0.6N had NaCl structure and its unit cell was smaller compared with CrN due to substitutions of Al for Cr atoms [7]. With increasing B contents z from 0 to 0.10, the (100) peak position shifted to higher diffraction angles from 37.78° to 38.00°, while the diffraction angle of (200) plane changed from 44.02° to 44.31°. It is reported that additions of B atoms resulted in phase segregation under non-equilibrium nitrogen plasma [11,14,15]. Kawate et al. [9] indicated that Cr–B–N films were comprised of some binary phase such as Cr2N CrN, Cr2B, and BN. Fig. 4 shows the changes in lattice parameters of CrxAlyBzN films. The lattice parameters decreased from 0.413 nm at z = 0 to 0.410 nm at z = 0.10 keeping the cubic structure. It is well known that lattice shrinkage or expansion in Ti-based nitride films is related with ionic and atomic radius of additional elements. For instance, incorporation of smaller atoms such as Al, Cr, and W led to decrease in lattice parameters of TiN [17]. Another example, lattice parameters of TixZryN changed from 0.423 nm to 0.458nm with increasing Zr contents [18]. It is noticed that lattice contraction of CrxAlyN was promoted by dope of boron as similar to the cases of metal element. 3.4. Morphology Fig. 5(a)–(c) show cross-sectional micrographs of CrxAly BzN with z = 0, 0.04 and 0.10, respectively. Cr0.4Al0.6N films had typical columnar structure, which gradually disappeared from z = 0.04 to z = 0.10. Holzschuh [19] reported that the morphology of TiN deposited by CVD method varied from coarse grains to micro-crystallites by incorporations of B atoms. Fig. 6(a)–(c) show TEM images of CrxAlyBzN films with z = 0, 0.04 and 0.10, respectively. Corresponding with SEM observation results, the grain sizes and shapes changed drastically as a function of B contents. The grain size of Cr0.4Al0.6N was approximately 100–200nm and grain boundaries were definite. While the grain size of CrxAlyBzN decreased down to 50 nm ranging from z = 0.04 to 0.10. 4. Summary CrxAlyBzN films with differing B contents were synthesized by the cathodic arc method and crystal structures, lattice parameters and microhardness were analyzed by X-ray and electron microscopy with respect to B contents. The obtained
1351
results are summarized as follows. The microhardness of CrxAlyBzN monotonously increased from 27 GPa (z = 0) up to 33GPa (z = 0.10), therefore higher hardness was obtained by the addition of B atoms. The XRD patterns showed that the crystal structures of CrxAlyBzN were kept the NaCl structures with all z values and the lattice parameters of CrxAlyBzN films decreased from 0.413 nm at z = 0 down to 0.410 nm at z = 0.10, according to ratios of z value. The columnar structure of CrxAlyBzN disappeared and grain size decreased in comparison with Cr0.4Al0.6N films. Acknowledgments This work was supported by Grant-in-Aid for the 21st Century COE program “KEIO Life-Conjugated Chemistry” and Japan Society for the Promotion of Science from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. References [1] U. Wahlström, L. Hultman, J.E. Sundgren, F. Adibi, I. Petrov, J.E. Greene, Thin Solid Films 235 (1993) 62. [2] A. Sugishima, H. Kajioka, Y. Makino, Surf. Coat. Technol. 97 (1997) 590. [3] A. Kimura, H. Hasegawa, K. Yamada, T. Suzuki, Surf. Coat. Technol. 120–121 (1999) 439. [4] T. Ikeda, H. Satoh, Thin Solid Films 195 (1991) 99. [5] Y. Makino, ISIJ Int. 38 (1998) 925. [6] Y. Makino, K. Nogi, Surf. Coat. Technol. 98 (1998) 1008. [7] M. Kawate, A. Kimura, T. Suzuki, J. Vac. Sci. Technol., A, Vac. Surf. Films 20 (2002) 569. [8] M. Kawate, A.K. Hasimoto, T. Suzuki, Surf. Coat. Technol. 165 (2003) 163. [9] M. Kawate, H. Hasegawa, A.K. Hashimoto, T. Suzuki, Proceedings of 3rd International Conference on the Coatings in Manuf. Eng., Greece, 2002, p. 343. [10] J. Musil, Surf. Coat. Technol. 125 (2000) 322. [11] M.A. Baker, T.P. Mollart, P.N. Gibson, W. Gissler, J. Vac. Sci. Technol., A, Vac. Surf. Films 15 (1997) 284. [12] S.M. Aouadi, F. Namavar, E. Tobin, N. Finnegan, R.T. Haasch, S.L. Rohde, J. Appl. Phys. 91 (2002) 1040. [13] M. Witthaut, R. Cremer, K. Reichert, D. Neuschütz, Thin Solid Films 377–378 (2000) 478. [14] C. Rebholz, H. Ziegele, A. Leyland, A. Matthews, J. Vac. Sci. Technol., A, Vac. Surf. Films 16 (1998) 2851. [15] S.M. Aouadi, J.A. Chaldek, F. Namavar, N. Finnegan, S.L. Rohde, J. Vac. Sci. Technol., B 20 (5) (2002) 1967. [16] C. Rebholz, A. Leyland, M. Matthews, Thin Solid Films 343–344 (1999) 242. [17] H. Hasegawa, T. Suzuki, Surf. Coat. Technol. 188–189 (2004) 234. [18] H. Hasegawa, A. Kimura, T. Suzuki, Surf. Coat. Technol. 132 (2000) 76. [19] H. Holzschuh, Thin Solid Films 469–470 (2004) 92.