- Email: [email protected]
An XPS study on oxidation of exposed-to-air Cr1−xZrxN film surfaces
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 15155–15159
www.materialstoday.com/proceedings
ICAPM0A_2017
An XPS study on oxidation of exposed-to-air Cr1−xZrxN film surfaces Chirawat Chantharangsia,*, Chutima Paksunchaia, Somyod Denchitcharoenb, Surasing Chaiyakunc,d, Pichet Limsuwanb,d a
Division of Physics, Faculty of Science and Technology, Rajamangala University of Technology Krungthep, Bangkok 10120, Thailand b Department of Physics, Faculty of Science, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand c Vacuum Technology and Thin Film Research Laboratory, Department of Physics, Faculty of Science, Burapha University, Chonburi 20131, Thailand d Thailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400, Thailand
Abstract Chromium zirconium nitride (CrZrN) thin films were prepared on Si (100) substrates with various Zr contents by using cosputtering technique. The Zr content was varied by variation of the Zr sputtering current from 0.2 to 0.8 A while the Cr current and the N2 flow rate were kept at 0.8 A and 6.0 sccm, respectively, to fix the concentration of Cr and N atoms. An oxidation caused by exposure to air of the Cr1−xZrxN thin films were studied by using X-ray photoelectron spectroscopy (XPS). Chemical composition analysis of XPS spectra revealed that oxygen detected on the film surfaces was increased with the rise in the Zr content. Deconvolutions of O 1s photoemission lines revealed bonding separately of O atoms to Cr and Zr atoms. Moreover, the fraction of the O–Cr bond was increased with the increasing Zr content. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 3rd International Conference on Applied Physics and Materials Applications. Keywords: CrZrN; XPS; Oxidation; Thin film
1. Introduction Chromium zirconium nitride (CrZrN) is one of the CrN-based ternary nitride coatings fabricated for improving protective properties that still possesses high oxidation resistance of the CrN [1–9]. The CrZrN has been reported on
* Corresponding author. Tel.: +66-02-287-9600; fax: +66-02-286-3596. E-mail address: [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 3rd International Conference on Applied Physics and Materials Applications.
15156
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
superior properties such as high hardness and low surface roughness [7]. Previous works show that the improved mechanical and tribological properties are caused by addition of Zr atoms into the CrN crystal structure, and vice versa [8,9]. However, Kim et al. [10] have found that these superior properties of CrZrN are degraded at 500 °C that contradict with the high oxidation resistance of CrN coatings. The surface oxidation is reported to be the cause of failures, and the addition of Zr to the CrN coatings deteriorates the impact resistance. Consequently, the effect of Zr addition on the surface oxidation of CrZrN coatings was investigated in this work. The CrZrN films were prepared by co-sputtering technique and were exposed to air before conducting a chemical analysis by using X-ray photoelectron spectroscopy (XPS). Deconvolutions of photoemission lines were performed to extract chemical information on the oxidation of film surfaces affected by the Zr content. 2. Experimental details Chromium zirconium nitride films with various Zr contents (Cr1−xZrxN) were deposited on Si (100) substrates by using an unbalanced DC magnetron co-sputtering technique. The Zr (99.99%) and Cr (99.99%) metals with a diameter of 3 inches and a thickness of 0.125 inches were used as the sputter targets. The working gas was a mixture of Ar (99.99%) and N2 (99.99%) that were flowed at 3.0 and 6.0 sccm, respectively. After being ultrasonically cleaned in acetone and isopropyl alcohol, the substrates were installed at the center of the chamber with the distances of 13 cm from the targets. The chamber was pumped down to a base pressure of 5.0×10−5 mbar, and then the Ar gas was flowed at 4.0 sccm to perform target sputter-cleaning for 10 min. After the target cleaning, the Ar was set to 3.0 sccm and N2 was led into the chamber at 6.0 sccm to deposit the Cr1−xZrxN films at the working pressure of 4.0×10−3 mbar. The Zr content was varied by applying different Zr sputtering currents (IZr) ranging from 0.2 to 0.8 A, whereas the Cr current (ICr) was fixed at 0.8 A. All the samples were deposited for 60 min. After the deposition, an oxidation process was conducted by exposing these Cr1−xZrxN samples to air at room temperature. The oxidized surfaces of the samples were studied by XPS (Kratos, AXIS Ultra DLD). Monochromatic Al Kα X-ray with photon energy of 1486.6 eV was used to excite atoms on the surfaces. Wide scanned spectra were acquired within binding energy (BE) range of 0–1200 eV with pass energy of 80 eV to obtain elemental concentrations. For chemical state analysis, high resolution XPS spectra of Cr 2p, Zr 3d, N 1s, O 1s, and C 1s core levels were acquired with the pass energy of 20 eV. The C 1s spectrum (285 eV for C–C bond) was used to be the reference for correcting BE shifts caused by charging on surfaces during the XPS analysis. After the charging correction, the high resolution spectra of O 1s, Cr 2p, Zr 3d, and N 1s were deconvoluted to extract the chemical information. 3. Results and discussion 3.1. Chemical composition Table 1. Elemental concentrations at surfaces of Cr1−xZrxN films with IZr of 0.2, 0.4, 0.6, and 0.8 A. IZr (A) 0.2 0.4 0.6 0.8
Cr 30.93 26.56 24.88 23.09
Elemental concentration (at.%) Zr N 1.90 30.65 6.06 28.93 8.22 25.46 8.56 21.71
O 36.52 38.49 41.44 46.64
Cr1−xZrxN Cr0.93Zr0.07N Cr0.81Zr0.19N Cr0.77Zr0.23N Cr0.68Zr0.32N
Table 1 lists atomic concentrations of Cr, Zr, N, and O elements obtained from the wide scanned spectra of the Cr1−xZrxN film surfaces deposited with IZr varied from 0.2 to 0.8 A. As shown in the table, the Zr concentration on surfaces increased from 1.90 to 8.56 at.% with the increasing IZr applied. The Cr and N elements had lowering tendencies in their contents due to the deposition with the fixed values of ICr and N2 flow rate for all the samples. However, the O content detected on the surfaces became higher with the increasing Zr concentration. The increase in O content could be attributed to O-affinity of the Zr metal. This is because the facility of transition metal surfaces for oxygen dissociation. Dissociative adsorption at room temperature of the oxygen on the metal surfaces can be
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
15157
possible, although the O–O bond dissociation energy is relatively high (498.40 kJ/mol). As suggested by comparing heats of oxygen adsorption, which are ~732 kJ/mol and ~1004 kJ/mol on Cr and Zr surfaces [11], respectively, the Zr addition into CrN could stimulate more the oxygen adsorption. The increase in Zr content could be the cause of deterioration in the oxidation resistance of the CrZrN coatings. For the Cr1−xZrxN formula shown in Table 1, all the samples were performed Ar sputter etching for 60 seconds to remove the oxide layer and then were re-scanned to obtain elemental concentrations for formulation at the underneath as reported in Ref. [12]. 3.2. Chemical state The core level spectra of Cr 2p, Zr 3d, N 1s, and O 1s acquired from oxidized film surfaces were deconvoluted by using CasaXPS software. Shapes of Component peaks used to extract chemical information were defined in the software as following: (1) the component peaks for O 1s and N 1s were set to GL(30) symmetric shape that is Gaussian (70%) – Lorentzian (30%) mix, (2) the component peaks for Cr 2p and Zr 3d were set to LA(1.6, 4, 7) and LA(2.6, 5, 14) asymmetric shape, respectively. As explained in Refs. [13] and [14], the first two numbers in LA line shape are the spread of the tail on either side of the Lorentzian shape, while the third is the width of the Gaussian used to convolute the Lorentzian shape. Furthermore, intensity ratios and peak separation of the components for Cr 2p and Zr 3d were restricted to 1:2 and 9.2 eV and to 2:3 and 2.43 eV, respectively.
Cr 2p3/2
IZr = 0.2 A
IZr = 0.2 A
IZr = 0.2 A
Cr− Metals
Cr 2p1/2
Cr−N
N−Metals
Zr 3d5/2
Cr−N Cr−O
N 1s
Zr 3d3/2
Cr−Metals
Zr−N
Cr−O
Zr−O N−O
592
588 584 580 576 Binding Energy (eV)
572
IZr = 0.8 A
188
186 184 182 180 Binding Energy (eV)
Cr 2p1/2
404
400 396 392 Binding Energy (eV)
IZr = 0.8 A
IZr = 0.8 A Cr 2p3/2
Cr−O
178
Zr 3d5/2
N 1s
Zr 3d3/2
Cr− Metals
N−Metals Zr−N
Cr−N
Zr−O
Cr−N Cr−Metals Cr−O
N−O
592
588 584 580 576 Binding Energy (eV)
572
188
186 184 182 180 Binding Energy (eV)
178
404
400 396 392 Binding Energy (eV)
Fig. 1. Deconvolution of Cr 2p and Zr 3d of Cr1−xZrxN films with IZr = 0.2 and 0.8 A.
15158
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
From Fig. 1, the component peaks with positions from NIST database [15] were convoluted to the Cr 2p3/2 envelope, including Cr–Metals (~574.7 eV), Cr–N (~575.8 eV), and Cr–O (~577.1 and ~578.4 eV). It can be seen that the Cr–O intensities, as compared to the Cr–N, increased with the O content detected on the surface. The Zr–O component (~182.3 eV) in the Zr 3d5/2 envelope in the sample with IZr = 0.2 A revealed the relatively low intensity corresponding to the low Zr content. After IZr rose to 0.8 A, the Zr–O intensity became higher than the Zr–N. This result confirmed that the rising Zr area on film surfaces induced more oxygen to be adsorbed. The deconvolution of O 1s was shown in Fig. 2. The O 1s of as-deposited samples revealed the lower intensity of O–Cr compared to O–Zr in the samples with IZr of 0.2 and 0.4 A, although surface area of Cr metal was higher. At IZr of 0.6 and 0.8 A, the O–Cr intensity became higher. These results suggested the oxygen induction caused by the increase of Zr content. For the exposed-to-air samples, the O 1s showed the O-affinity of the Zr metal corresponding with the heats of oxygen adsorption on both metals. IZr = 0.2 A
IZr = 0.4 A
IZr = 0.6 A
IZr = 0.8 A
(as-deposited)
(as-deposited)
(as-deposited)
(as-deposited)
O 1s
O 1s O 1s O−Zr
O−Zr
O−Zr
O 1s O−Zr
O−Cr
O−Cr O−Cr
O−N
540
536 532 528 540 Binding Energy (eV)
O−Cr
O−N
536 532 528 540 Binding Energy (eV)
IZr = 0.2 A
IZr = 0.4 A
(exposed-to-air)
(exposed-to-air)
O−N
O−N
536 532 528 540 Binding Energy (eV)
IZr = 0.6 A (exposed-to-air)
536 532 528 Binding Energy (eV)
IZr = 0.8 A O 1s
(exposed-to-air)
O 1s O−Zr
O 1s O−Zr
O 1s
O−Zr O−Cr
O−Zr O−Cr O−Cr
O−N O−Cr
540
536 532 528 540 Binding Energy (eV)
O−N
O−N O−N
536 532 528 540 Binding Energy (eV)
536 532 528 540 Binding Energy (eV)
536 532 528 Binding Energy (eV)
Fig. 2. Deconvolution of O 1s of as-deposited and exposed-to-air Cr1−xZrxN films with various IZr.
4. Conclusions Sputter-deposited CrZrN thin films prepared with different Zr currents were studied the effect of Zr content on the oxidation occurring on their surfaces by X-ray photoelectron spectroscopy. The results suggested that Zr content increased with the increase of the Zr current leading to rising of Zr metal areas. Since the heat of adsorption on the Zr surface is higher, the oxygen could be absorbed more on film surfaces. This effect should be the cause of the surface oxidation that led to the deterioration in the oxidation resistance of the CrZrN coatings.
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
15159
Acknowledgements The authors would like to thank for the sputtering system and facilities provided by Vacuum Technology and Thin films Research Laboratory at Burapha University. Furthermore, we really appreciate the support for our research from King Mongkut’s University of Technology Thonburi under the National Research University Project and Thailand Center of Excellence in Physics. References [1] X.T. Zeng, S. Zhang, C.Q. Sun, Y.C. Liu, Nanometric-layered CrN/TiN thin films: mechanical strength and thermal stability, Thin Solid Films 424 (2003) 99–102. [2] P. Hones, R. Sanjinés, F. Lévy, Sputter deposited chromium nitride based ternary compounds for hard coatings, Thin Solid Films 332 (1998) 240–246. [3] S.M. Aouadi, K.C. Wong, K.A.R. Mitchell, F. Namavar, E. Tobin, D.M. Mihut, S.L. Rohde, Characterization of titanium chromium nitride nanocomposite protective coatings, Appl. Surf. Sci. 229 (2004) 387–394. [4] M. Uchida, N. Nihira, A. Mitsuo, K. Toyoda, K. Kubota, T. Aizawa, Friction and wear properties of CrAlN and CrVN films deposited by cathodic arc ion plating method, Surf. Coat. Technol. 177–178 (2004) 627–630. [5] P. Hones, M. Diserens, R. Sanjinés, F. Lévy, Electronic structure and mechanical properties of hard coatings from the chromium–tungsten nitride system, J. Vac. Sci. Technol. B 18 (2000) 2851–2856. [6] E. Martinez, R. Sanjinés, A. Karimi, J. Esteve, F. Lévy, Mechanical properties of nanocomposite and multilayered Cr–Si–N sputtered thin films, Surf. Coat. Technol. 180–181 (2004) 570–574. [7] G.S. Kim, B.S. Kim, S.Y. Lee, J.H. Hahn, Structure and mechanical properties of Cr–Zr–N films synthesized by closed field unbalanced magnetron sputtering with vertical magnetron sources, Surf. Coat. Technol. 200 (2005) 1669–1675. [8] S.M. Aouadi, T. Maeruf, R.D. Twesten, D.M. Mihut, S.L. Rohde, Physical and mechanical properties of chromium zirconium nitride thin films, Surf. Coat. Technol. 200 (2006) 3411–3417. [9] Z.G. Zhang, O. Rapaud, N. Bonasso, D. Mercs, C. Dong, C. Coddet, Microstructures and corrosion behaviors of Zr modified CrN coatings deposited by DC magnetron sputtering, Vacuum 82 (2008) 1332–1336. [10] S.M. Kim, B.S. Kim, G.S. Kim, S.Y. Lee, B.Y. Lee, Evaluation of the high temperature characteristics of the CrZrN coatings, Surf. Coat. Technol. 202 (2008) 5521. [11] W. Martienssen, H. Warlimont, Handbook of Condensed Matter and Materials Data, Springer, Heidelberg, 2005. [12] C. Chantharangsi, S. Denchitcharoen, S. Chaiyakun, P. Limsuwan, Structures, morphologies, and chemical states of sputter-deposited CrZrN thin films with various Zr contents, Thin Solid Films 589 (2015) 613–619. [13] M.C. Biesinger, L.W.M. Lau, A.R. Gerson, R.St.C. Smart, Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn, Appl. Surf. Sci. 257 (2010) 887–898. [14] M.C. Biesinger, B.P. Payne, A.P. Grosvenor, L.W.M. Lau, A.R. Gerson, R.St.C. Smart, Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni, Appl. Surf. Sci. 257 (2011) 2717–2730. [15] A.V. Naumkin, A. Kraut-Vass, S.W. Gaarenstroom, C.J. Powell, NIST Standard Reference Database 20, Version 4.1 (Web Version), 2012. (http://srdata.nist.gov/xps/).
ScienceDirect Materials Today: Proceedings 5 (2018) 15155–15159
www.materialstoday.com/proceedings
ICAPM0A_2017
An XPS study on oxidation of exposed-to-air Cr1−xZrxN film surfaces Chirawat Chantharangsia,*, Chutima Paksunchaia, Somyod Denchitcharoenb, Surasing Chaiyakunc,d, Pichet Limsuwanb,d a
Division of Physics, Faculty of Science and Technology, Rajamangala University of Technology Krungthep, Bangkok 10120, Thailand b Department of Physics, Faculty of Science, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand c Vacuum Technology and Thin Film Research Laboratory, Department of Physics, Faculty of Science, Burapha University, Chonburi 20131, Thailand d Thailand Center of Excellence in Physics, CHE, Ministry of Education, Bangkok 10400, Thailand
Abstract Chromium zirconium nitride (CrZrN) thin films were prepared on Si (100) substrates with various Zr contents by using cosputtering technique. The Zr content was varied by variation of the Zr sputtering current from 0.2 to 0.8 A while the Cr current and the N2 flow rate were kept at 0.8 A and 6.0 sccm, respectively, to fix the concentration of Cr and N atoms. An oxidation caused by exposure to air of the Cr1−xZrxN thin films were studied by using X-ray photoelectron spectroscopy (XPS). Chemical composition analysis of XPS spectra revealed that oxygen detected on the film surfaces was increased with the rise in the Zr content. Deconvolutions of O 1s photoemission lines revealed bonding separately of O atoms to Cr and Zr atoms. Moreover, the fraction of the O–Cr bond was increased with the increasing Zr content. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 3rd International Conference on Applied Physics and Materials Applications. Keywords: CrZrN; XPS; Oxidation; Thin film
1. Introduction Chromium zirconium nitride (CrZrN) is one of the CrN-based ternary nitride coatings fabricated for improving protective properties that still possesses high oxidation resistance of the CrN [1–9]. The CrZrN has been reported on
* Corresponding author. Tel.: +66-02-287-9600; fax: +66-02-286-3596. E-mail address: [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 3rd International Conference on Applied Physics and Materials Applications.
15156
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
superior properties such as high hardness and low surface roughness [7]. Previous works show that the improved mechanical and tribological properties are caused by addition of Zr atoms into the CrN crystal structure, and vice versa [8,9]. However, Kim et al. [10] have found that these superior properties of CrZrN are degraded at 500 °C that contradict with the high oxidation resistance of CrN coatings. The surface oxidation is reported to be the cause of failures, and the addition of Zr to the CrN coatings deteriorates the impact resistance. Consequently, the effect of Zr addition on the surface oxidation of CrZrN coatings was investigated in this work. The CrZrN films were prepared by co-sputtering technique and were exposed to air before conducting a chemical analysis by using X-ray photoelectron spectroscopy (XPS). Deconvolutions of photoemission lines were performed to extract chemical information on the oxidation of film surfaces affected by the Zr content. 2. Experimental details Chromium zirconium nitride films with various Zr contents (Cr1−xZrxN) were deposited on Si (100) substrates by using an unbalanced DC magnetron co-sputtering technique. The Zr (99.99%) and Cr (99.99%) metals with a diameter of 3 inches and a thickness of 0.125 inches were used as the sputter targets. The working gas was a mixture of Ar (99.99%) and N2 (99.99%) that were flowed at 3.0 and 6.0 sccm, respectively. After being ultrasonically cleaned in acetone and isopropyl alcohol, the substrates were installed at the center of the chamber with the distances of 13 cm from the targets. The chamber was pumped down to a base pressure of 5.0×10−5 mbar, and then the Ar gas was flowed at 4.0 sccm to perform target sputter-cleaning for 10 min. After the target cleaning, the Ar was set to 3.0 sccm and N2 was led into the chamber at 6.0 sccm to deposit the Cr1−xZrxN films at the working pressure of 4.0×10−3 mbar. The Zr content was varied by applying different Zr sputtering currents (IZr) ranging from 0.2 to 0.8 A, whereas the Cr current (ICr) was fixed at 0.8 A. All the samples were deposited for 60 min. After the deposition, an oxidation process was conducted by exposing these Cr1−xZrxN samples to air at room temperature. The oxidized surfaces of the samples were studied by XPS (Kratos, AXIS Ultra DLD). Monochromatic Al Kα X-ray with photon energy of 1486.6 eV was used to excite atoms on the surfaces. Wide scanned spectra were acquired within binding energy (BE) range of 0–1200 eV with pass energy of 80 eV to obtain elemental concentrations. For chemical state analysis, high resolution XPS spectra of Cr 2p, Zr 3d, N 1s, O 1s, and C 1s core levels were acquired with the pass energy of 20 eV. The C 1s spectrum (285 eV for C–C bond) was used to be the reference for correcting BE shifts caused by charging on surfaces during the XPS analysis. After the charging correction, the high resolution spectra of O 1s, Cr 2p, Zr 3d, and N 1s were deconvoluted to extract the chemical information. 3. Results and discussion 3.1. Chemical composition Table 1. Elemental concentrations at surfaces of Cr1−xZrxN films with IZr of 0.2, 0.4, 0.6, and 0.8 A. IZr (A) 0.2 0.4 0.6 0.8
Cr 30.93 26.56 24.88 23.09
Elemental concentration (at.%) Zr N 1.90 30.65 6.06 28.93 8.22 25.46 8.56 21.71
O 36.52 38.49 41.44 46.64
Cr1−xZrxN Cr0.93Zr0.07N Cr0.81Zr0.19N Cr0.77Zr0.23N Cr0.68Zr0.32N
Table 1 lists atomic concentrations of Cr, Zr, N, and O elements obtained from the wide scanned spectra of the Cr1−xZrxN film surfaces deposited with IZr varied from 0.2 to 0.8 A. As shown in the table, the Zr concentration on surfaces increased from 1.90 to 8.56 at.% with the increasing IZr applied. The Cr and N elements had lowering tendencies in their contents due to the deposition with the fixed values of ICr and N2 flow rate for all the samples. However, the O content detected on the surfaces became higher with the increasing Zr concentration. The increase in O content could be attributed to O-affinity of the Zr metal. This is because the facility of transition metal surfaces for oxygen dissociation. Dissociative adsorption at room temperature of the oxygen on the metal surfaces can be
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
15157
possible, although the O–O bond dissociation energy is relatively high (498.40 kJ/mol). As suggested by comparing heats of oxygen adsorption, which are ~732 kJ/mol and ~1004 kJ/mol on Cr and Zr surfaces [11], respectively, the Zr addition into CrN could stimulate more the oxygen adsorption. The increase in Zr content could be the cause of deterioration in the oxidation resistance of the CrZrN coatings. For the Cr1−xZrxN formula shown in Table 1, all the samples were performed Ar sputter etching for 60 seconds to remove the oxide layer and then were re-scanned to obtain elemental concentrations for formulation at the underneath as reported in Ref. [12]. 3.2. Chemical state The core level spectra of Cr 2p, Zr 3d, N 1s, and O 1s acquired from oxidized film surfaces were deconvoluted by using CasaXPS software. Shapes of Component peaks used to extract chemical information were defined in the software as following: (1) the component peaks for O 1s and N 1s were set to GL(30) symmetric shape that is Gaussian (70%) – Lorentzian (30%) mix, (2) the component peaks for Cr 2p and Zr 3d were set to LA(1.6, 4, 7) and LA(2.6, 5, 14) asymmetric shape, respectively. As explained in Refs. [13] and [14], the first two numbers in LA line shape are the spread of the tail on either side of the Lorentzian shape, while the third is the width of the Gaussian used to convolute the Lorentzian shape. Furthermore, intensity ratios and peak separation of the components for Cr 2p and Zr 3d were restricted to 1:2 and 9.2 eV and to 2:3 and 2.43 eV, respectively.
Cr 2p3/2
IZr = 0.2 A
IZr = 0.2 A
IZr = 0.2 A
Cr− Metals
Cr 2p1/2
Cr−N
N−Metals
Zr 3d5/2
Cr−N Cr−O
N 1s
Zr 3d3/2
Cr−Metals
Zr−N
Cr−O
Zr−O N−O
592
588 584 580 576 Binding Energy (eV)
572
IZr = 0.8 A
188
186 184 182 180 Binding Energy (eV)
Cr 2p1/2
404
400 396 392 Binding Energy (eV)
IZr = 0.8 A
IZr = 0.8 A Cr 2p3/2
Cr−O
178
Zr 3d5/2
N 1s
Zr 3d3/2
Cr− Metals
N−Metals Zr−N
Cr−N
Zr−O
Cr−N Cr−Metals Cr−O
N−O
592
588 584 580 576 Binding Energy (eV)
572
188
186 184 182 180 Binding Energy (eV)
178
404
400 396 392 Binding Energy (eV)
Fig. 1. Deconvolution of Cr 2p and Zr 3d of Cr1−xZrxN films with IZr = 0.2 and 0.8 A.
15158
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
From Fig. 1, the component peaks with positions from NIST database [15] were convoluted to the Cr 2p3/2 envelope, including Cr–Metals (~574.7 eV), Cr–N (~575.8 eV), and Cr–O (~577.1 and ~578.4 eV). It can be seen that the Cr–O intensities, as compared to the Cr–N, increased with the O content detected on the surface. The Zr–O component (~182.3 eV) in the Zr 3d5/2 envelope in the sample with IZr = 0.2 A revealed the relatively low intensity corresponding to the low Zr content. After IZr rose to 0.8 A, the Zr–O intensity became higher than the Zr–N. This result confirmed that the rising Zr area on film surfaces induced more oxygen to be adsorbed. The deconvolution of O 1s was shown in Fig. 2. The O 1s of as-deposited samples revealed the lower intensity of O–Cr compared to O–Zr in the samples with IZr of 0.2 and 0.4 A, although surface area of Cr metal was higher. At IZr of 0.6 and 0.8 A, the O–Cr intensity became higher. These results suggested the oxygen induction caused by the increase of Zr content. For the exposed-to-air samples, the O 1s showed the O-affinity of the Zr metal corresponding with the heats of oxygen adsorption on both metals. IZr = 0.2 A
IZr = 0.4 A
IZr = 0.6 A
IZr = 0.8 A
(as-deposited)
(as-deposited)
(as-deposited)
(as-deposited)
O 1s
O 1s O 1s O−Zr
O−Zr
O−Zr
O 1s O−Zr
O−Cr
O−Cr O−Cr
O−N
540
536 532 528 540 Binding Energy (eV)
O−Cr
O−N
536 532 528 540 Binding Energy (eV)
IZr = 0.2 A
IZr = 0.4 A
(exposed-to-air)
(exposed-to-air)
O−N
O−N
536 532 528 540 Binding Energy (eV)
IZr = 0.6 A (exposed-to-air)
536 532 528 Binding Energy (eV)
IZr = 0.8 A O 1s
(exposed-to-air)
O 1s O−Zr
O 1s O−Zr
O 1s
O−Zr O−Cr
O−Zr O−Cr O−Cr
O−N O−Cr
540
536 532 528 540 Binding Energy (eV)
O−N
O−N O−N
536 532 528 540 Binding Energy (eV)
536 532 528 540 Binding Energy (eV)
536 532 528 Binding Energy (eV)
Fig. 2. Deconvolution of O 1s of as-deposited and exposed-to-air Cr1−xZrxN films with various IZr.
4. Conclusions Sputter-deposited CrZrN thin films prepared with different Zr currents were studied the effect of Zr content on the oxidation occurring on their surfaces by X-ray photoelectron spectroscopy. The results suggested that Zr content increased with the increase of the Zr current leading to rising of Zr metal areas. Since the heat of adsorption on the Zr surface is higher, the oxygen could be absorbed more on film surfaces. This effect should be the cause of the surface oxidation that led to the deterioration in the oxidation resistance of the CrZrN coatings.
C. Chantharangsi et al. / Materials Today: Proceedings 5 (2018) 15155–15159
15159
Acknowledgements The authors would like to thank for the sputtering system and facilities provided by Vacuum Technology and Thin films Research Laboratory at Burapha University. Furthermore, we really appreciate the support for our research from King Mongkut’s University of Technology Thonburi under the National Research University Project and Thailand Center of Excellence in Physics. References [1] X.T. Zeng, S. Zhang, C.Q. Sun, Y.C. Liu, Nanometric-layered CrN/TiN thin films: mechanical strength and thermal stability, Thin Solid Films 424 (2003) 99–102. [2] P. Hones, R. Sanjinés, F. Lévy, Sputter deposited chromium nitride based ternary compounds for hard coatings, Thin Solid Films 332 (1998) 240–246. [3] S.M. Aouadi, K.C. Wong, K.A.R. Mitchell, F. Namavar, E. Tobin, D.M. Mihut, S.L. Rohde, Characterization of titanium chromium nitride nanocomposite protective coatings, Appl. Surf. Sci. 229 (2004) 387–394. [4] M. Uchida, N. Nihira, A. Mitsuo, K. Toyoda, K. Kubota, T. Aizawa, Friction and wear properties of CrAlN and CrVN films deposited by cathodic arc ion plating method, Surf. Coat. Technol. 177–178 (2004) 627–630. [5] P. Hones, M. Diserens, R. Sanjinés, F. Lévy, Electronic structure and mechanical properties of hard coatings from the chromium–tungsten nitride system, J. Vac. Sci. Technol. B 18 (2000) 2851–2856. [6] E. Martinez, R. Sanjinés, A. Karimi, J. Esteve, F. Lévy, Mechanical properties of nanocomposite and multilayered Cr–Si–N sputtered thin films, Surf. Coat. Technol. 180–181 (2004) 570–574. [7] G.S. Kim, B.S. Kim, S.Y. Lee, J.H. Hahn, Structure and mechanical properties of Cr–Zr–N films synthesized by closed field unbalanced magnetron sputtering with vertical magnetron sources, Surf. Coat. Technol. 200 (2005) 1669–1675. [8] S.M. Aouadi, T. Maeruf, R.D. Twesten, D.M. Mihut, S.L. Rohde, Physical and mechanical properties of chromium zirconium nitride thin films, Surf. Coat. Technol. 200 (2006) 3411–3417. [9] Z.G. Zhang, O. Rapaud, N. Bonasso, D. Mercs, C. Dong, C. Coddet, Microstructures and corrosion behaviors of Zr modified CrN coatings deposited by DC magnetron sputtering, Vacuum 82 (2008) 1332–1336. [10] S.M. Kim, B.S. Kim, G.S. Kim, S.Y. Lee, B.Y. Lee, Evaluation of the high temperature characteristics of the CrZrN coatings, Surf. Coat. Technol. 202 (2008) 5521. [11] W. Martienssen, H. Warlimont, Handbook of Condensed Matter and Materials Data, Springer, Heidelberg, 2005. [12] C. Chantharangsi, S. Denchitcharoen, S. Chaiyakun, P. Limsuwan, Structures, morphologies, and chemical states of sputter-deposited CrZrN thin films with various Zr contents, Thin Solid Films 589 (2015) 613–619. [13] M.C. Biesinger, L.W.M. Lau, A.R. Gerson, R.St.C. Smart, Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn, Appl. Surf. Sci. 257 (2010) 887–898. [14] M.C. Biesinger, B.P. Payne, A.P. Grosvenor, L.W.M. Lau, A.R. Gerson, R.St.C. Smart, Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni, Appl. Surf. Sci. 257 (2011) 2717–2730. [15] A.V. Naumkin, A. Kraut-Vass, S.W. Gaarenstroom, C.J. Powell, NIST Standard Reference Database 20, Version 4.1 (Web Version), 2012. (http://srdata.nist.gov/xps/).