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Characteristics of Al doped zinc oxide (ZAO) thin films deposited by RF magnetron sputtering
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 249 (2006) 536–539 www.elsevier.com/locate/nimb
Characteristics of Al doped zinc oxide (ZAO) thin films deposited by RF magnetron sputtering Satoshi Kobayakawa a, Yoshikazu Tanaka
a,b
, Ari Ide-Ektessabi
a,c,*
a
c
Graduate School of Engineering, Kyoto University, Japan b Sanwa Kenma Ltd., Japan International Innovation Center, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan Available online 3 May 2006
Abstract ZAO and ITO thin films were prepared by RF magnetron sputtering. In this study, three of the sputtering parameters, that is, substrate temperature, oxygen flow rate and RF discharge power were varied separately to fabricate samples. The range of variation of substrate temperature was from room temperature to 623 K. The relative concentration of O2 in the ambient gas in the chamber was 0% or 25%. The sputtering rate was changed by controlling the discharge power. The minimum surface resistivity of ZAO was 2.53 · 102 X/cm2 for samples sputtered at a substrate temperature of 373 K and that of ITO was 2.37 · 101 X/cm2 sputtered under standard conditions. Visible light transmittances of these samples were 89.9% and 90.2%, respectively. From these results, it is suggested that when sputtered with optimum sputtering parameters, ZAO is a potential material for practical use for transparent conducting electrodes (TCO) for PDPs. 2006 Elsevier B.V. All rights reserved. PACS: 78.20; 89.02 Keywords: ZAO; ITO; Sputtering; Transparent conducting electrode; XRD
1. Introduction Indium tin oxide (ITO) is widely used in plasma display panels (PDPs). However, Indium resources are supposed to be exhausted in the next few decades. Recently thin films of zinc oxide have attracted attention as an alternative to ITO because ZnO films have high visible light transmittance and low surface resistivity [1,2]. Recently, Al, Ga and In doped ZnO has been studied in order to decrease the surface resistivity of ZnO [3–9]. In this study, the properties of Al doped ZnO (ZAO) films were investigated. The purpose
*
Corresponding author. Address: International Innovation Center, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan. Tel./fax: +81 75 753 5259. E-mail address: [email protected] (A. Ide-Ektessabi). 0168-583X/$ - see front matter 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.03.047
of this study was to optimize parameters of the RF magnetron sputtering process to obtain high quality ZAO thin films as transparent conducting electrodes. There are reports showing that the properties of thin films are mainly influenced by process parameters during sputtering, such as substrate temperature, discharge power, target–substrate distance and oxygen flow rate [9,10]. ZAO thin films were deposited by RF magnetron sputtering by changing substrate temperature and oxygen flow rate. Then, the visible light transmittance and the surface resistivity of these films were measured. In order to analyze the properties of ZAO thin films, the following methods were applied. Crystal orientation and composition of these films were analyzed by X-ray diffraction (XRD) analysis and Rutherford back scattering spectrometry (RBS), respectively. X-ray photoelectron spectroscopy (XPS) was used for determining the chemical state of the surface of these films.
S. Kobayakawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 249 (2006) 536–539
2. Experimental method A RF magnetron sputtering system was used in this experiment. The diameter and thickness of the sputtering targets of ZAO and ITO were 101.6 mm and 5 mm. The ZAO target contained 2 wt% Al2O3. The ITO target consisted of 90 wt% In2O3 and 10 wt% SnO2. The standard sputtering parameters in this study are presented below. The substrate temperature was room temperature. The discharge power was 3.7 W/cm2. Argon gas was used as ambient gas in the chamber. The distance between target and substrate was 215 mm. Argon gas was introduced into the chamber with flow rate of 10.4 cm and kept at a pressure 0.10 Pa. The samples fabricated under the standard condition will be referred to as ZAO-1 and ITO-1, respectively. First, only the substrate temperature was changed to 373 K, 473 K and 623 K to prepare a sample (ZAO-2, ITO2 (373 K), ZAO-3 (473 K), and ZAO-4 (623 K)). Second, samples were fabricated using Ar gas containing 25% oxygen (ZAO-5 and ITO-3). Finally, discharge power was reduced to 1.85 W/cm2 to sputter (ZAO-6). The ZAO standard sample was annealed at 673 K to investigate the influence of annealing (ZAO-7). In order to clean up the surface of the target, 10 min presputtering with a closed shutter at a discharge power of 3.7 W/cm2 was followed by 20 min deposition to fabricate thin films. Visible light transmittance was measured using a V-560 US–VS spectro photometer (JASCO). The measurement range was from 380 nm to 820 nm at an interval of 1 nm. Visible light transmittance (mean value) was converted into the value of the layers with thickness of 100 nm in order to compensate for the effect of a difference of thickness. The equipment to measure the surface resistivity was Loresta-GP (Mitsubishi Chemical) using the linear four-point probe method. To measure the thickness, the surface profilometer (Taylor Hobson, Form Taly Surf Series2) was used. For the measurement of the composition of the films, Rutherford backscattering spectrometry (RBS) was performed. A 2 MeV 4He2+ ion beam was applied for this experiment. X-ray diffraction (XRD) analysis was applied to determine the crystal structure of these films using CuKa line in the Bragg angle range from 30 to 90 with a MAC. Science M03X. The chemical bonding of the films was investigated by X-ray photoelectron spectroscopy (XPS) with a MgKa radiation source (Shimazu Axis 165S). 3. Results and discussion 3.1. Optical and electrical properties of the films Thin films were fabricated while changing the substrate temperatures (373 K, 473 K, and 623 K) in order to investigate the effect of the substrate temperature on the optical and electrical characteristics. Table 1 shows the visible light transmittance and surface resistivity of all samples which will be discussed below. In the case of ZAO, as substrate temperature increased, the resistivities became lower than
537
Table 1 Visible light transmittance and surface resistivity Sample
Film thickness (nm)
Resistivity (X/cm2)
Transmittance (%)
ZAO
ZAO-1 ZAO-2 ZAO-3 ZAO-4 ZAO-5 ZAO-6 ZAO-7
123.7 142.0 146.0 130.0 123.7 240.0 97.7
3.38 · 103 2.53 · 102 2.93 · 102 4.53 · 102 – 2.76 · 106 6.54 · 104
89.2 89.9 90.1 88.3 89.5 91.9 80.8
ITO
ITO-1 ITO-2 ITO-3
192.0 180.0 238.0
2.37 · 101 2.71 · 101 8.58 · 106
90.2 89.5 89.6
that of the standard sample. The lowest resistivity was 2.53 · 102 X/cm2 at 373 K. But as substrate temperature increased further, the resistivity increased. This result suggests that the optimum substrate temperature to minimize the resistivity was around 373 K. This result is in good agreement with the conclusion of the experiments conducted by Igasaki et al. [11]. The minimum value of resistivity of ITO samples was 2.37 · 101 X/cm2 at room temperature in Table 1. When the ZAO film deposited under the standard conditions was annealed at 673 K for 2 h, the resistivity became so high that the resistivity could not be measured with the Loresta-GP. This is attributed to the fact that in the case of films annealed in the air, oxygen was incorporated into films and the donorconcentration resulting from interstitial zinc atoms and oxygen vacancies decreased significantly. In the case of ITO, the same tendency was reported by Minami et al. [12]. ZAO and ITO films were deposited in an ambient of argon gas with a 25% partial pressure of oxygen. In comparison with standard samples, the resistivities of both films were considerably increased and the mean value of visible light transmittance became slightly higher. This may be due to the fact that the amount of oxygen vacancies as donors was reduced as a result of introducing oxygen into these films. The film which was deposited at 1.85 W/ cm2 showed a lower transmittance and higher resistivity than those of films fabricated at 3.7 W/cm2. From the result of RBS, the value of Al/Zn of the film deposited at 3.7 W/cm2 was 0.06 and that of the film deposited at 1.85 W/cm2 was 0.03. The proportion of Al content was reduced as the discharge power was reduced. The substitutional aluminum atoms act as donors in ZAO film so the rise of resistivity was considered to be attributable to the reduction of the Al content. 3.2. Crystal structure and the chemical states of the ZAO films XRD spectra of ZAO films (from ZAO-1 to ZAO-7) deposited on Si substrates under the various condition are shown in Fig. 1. From the XRD spectra, all ZAO films had only the (0 0 2) orientation. In the case of the samples
538
S. Kobayakawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 249 (2006) 536–539
intensity of (0 0 2) crystalline ZnO (the first peak) in the XPS Zn2p3/2 spectrum. The same tendency was reported about ITO by Park et al. [13]. 4. Conclusions
Fig. 1. XRD spectra of ZAO films deposited under various conditions.
deposited at 373 K and 473 K, which showed the lowest resistivity, the intensity of the (0 0 2) peak decreased significantly. On the contrary, in the case of the annealed sample which showed a higher resistivity, the intensity of (0 0 2) peak were stronger than that of the standard sample. The same tendency was observed in the case of the sample deposited with discharge gas including oxygen which showed a high resistivity. From these result, it was concluded that the resistivity decreased as the crystalline structure became closer to the amorphous phase. The Zn2p3/2 XPS spectra of ZAO-3 and ZAO-6 are shown in Fig. 2. The first peaks at 1020.2 eV and 1021.3 eV correspond to (0 0 2) crystalline ZnO and the second peaks at 1020.9 eV and 1021.6 eV correspond to amorphous ZnO. The difference in binding energy of these two samples seemed to depend on charge shifts rather than chemical shifts. These facts corresponded to the result of XRD mentioned earlier. The sample sputtered with ambient gas containing 25% oxygen shows a strong (0 0 2) diffraction peak in the XRD spectrum and higher intensity of (0 0 2) crystalline ZnO (the first peak) in the XPS Zn2p3/2 spectrum. On the contrary, the sample sputtered at 473 K shows smaller (0 0 2) peak in XRD and a lower
In this study thin films of ZAO were prepared by RF magnetron sputtering by changing the substrate temperature and oxygen flow rate. The properties of these films were investigated. The optimum substrate temperature in the sputtering process was estimated to be around 373 K. Annealing in the air had negative effects on the electrical characteristics of films because oxygen was introduced into films and the concentration of vacancies as donor sites was decreased. In order to avoid introduction of oxygen into the films, the films should be annealed in vacuum. A smaller oxygen flow rate is desirable rather than 25% because the oxygen flow rate in the ambient gas is directly connected with oxygen vacancies as donor sites in the thin films. ITO as used in practice has a surface resistivity of 20 X/ cm2. This study shows that when the sputtering parameters were optimized, ZAO thin film showed good optical and electrical characteristics which are close to those of ITO. Sputtering parameters optimized, ZAO thin film is a potential material to be used for transparent conducting electrodes for PDPs. Acknowledgements The authors are grateful to Mr. Y. Tsukuda and the members at Sanwa Kenma Ltd. for their assistance in preparing the samples. We would like to appreciate Mr. T. Takaishi at Kyoto Research Park Corp. for his assistance with the XRD. The RBS measurement was performed at the Quantum Science Engineering Center, Graduate School of Engineering, Kyoto University. We also would like to thank Mr. H. Tsuchida. We would like to thank Mr. H. Tsuji at Venture Business Laboratory, Kyoto University for the XPS measurements.
Fig. 2. XPS spectra of ZAO films deposited under various conditions.
S. Kobayakawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 249 (2006) 536–539
References [1] K. Ellmer, J. Phys. D Appl. Phys. 34 (2001) 3097. [2] S. Shirakata, T. Sakemi, K. Awai, T. Yamamoto, Thin Solid Films 445 (2003) 278. [3] Y. Qu, T.A. Gessert, K. Ramanathan, R.G. Dhere, R. Noufi, T.J. Coutts, J .Vac. Sci. Technol. A 11 (4) (1993) 996. [4] K. Tominaga, N. Umezu, I. Mori, T. Ushiro, T. Moriga, I. Nakabayashi, J. Vac. Sci. Technol. A 16 (3) (1998) 1213. [5] M. Miyazaki, K. Sato, A. Mitsui, H. Nishimura, J. Non-Cryst. Solids 218 (1997) 323. [6] T. Yamamoto, T. Sakemi, K. Awai, S. Shirakata, Thin Solid Films 451–452 (2004) 439.
539
[7] K. Matsubara, P. Fons, K. Iwata, A. Yamada, S. Niki, Thin Solid Films 422 (2002) 176. [8] H. Agura, A. Suzuki, T. Matsushita, T. Aoki, M. Okuda, Thin Solid Films 445 (2003) 263. [9] Z.C. Jin, I. Hamberg, C.G. Granqvist, J. Appl. Phys. 64 (10) (1988) 5117. [10] M. Chen, Z.L. Pei, C. Sun, J. Gong, R.F. Huang, L.S. Wen, J. Mater. Sci. Eng. B 85 (8) (2001) 212. [11] Y. Igasaki, H. Saito, J. Appl. Phys. 69 (4) (1991) 2190. [12] H. Nanto, T. Minami, S. Orito, S. Takata, J. Appl. Phys. 63 (8) (1988) 2711. [13] Y.C. Park, Y.S. Kim, H.K. Seo, S.G. Ansari, H.S. Shin, Surf. Coat. Technol. 161 (2002) 62.
Nuclear Instruments and Methods in Physics Research B 249 (2006) 536–539 www.elsevier.com/locate/nimb
Characteristics of Al doped zinc oxide (ZAO) thin films deposited by RF magnetron sputtering Satoshi Kobayakawa a, Yoshikazu Tanaka
a,b
, Ari Ide-Ektessabi
a,c,*
a
c
Graduate School of Engineering, Kyoto University, Japan b Sanwa Kenma Ltd., Japan International Innovation Center, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan Available online 3 May 2006
Abstract ZAO and ITO thin films were prepared by RF magnetron sputtering. In this study, three of the sputtering parameters, that is, substrate temperature, oxygen flow rate and RF discharge power were varied separately to fabricate samples. The range of variation of substrate temperature was from room temperature to 623 K. The relative concentration of O2 in the ambient gas in the chamber was 0% or 25%. The sputtering rate was changed by controlling the discharge power. The minimum surface resistivity of ZAO was 2.53 · 102 X/cm2 for samples sputtered at a substrate temperature of 373 K and that of ITO was 2.37 · 101 X/cm2 sputtered under standard conditions. Visible light transmittances of these samples were 89.9% and 90.2%, respectively. From these results, it is suggested that when sputtered with optimum sputtering parameters, ZAO is a potential material for practical use for transparent conducting electrodes (TCO) for PDPs. 2006 Elsevier B.V. All rights reserved. PACS: 78.20; 89.02 Keywords: ZAO; ITO; Sputtering; Transparent conducting electrode; XRD
1. Introduction Indium tin oxide (ITO) is widely used in plasma display panels (PDPs). However, Indium resources are supposed to be exhausted in the next few decades. Recently thin films of zinc oxide have attracted attention as an alternative to ITO because ZnO films have high visible light transmittance and low surface resistivity [1,2]. Recently, Al, Ga and In doped ZnO has been studied in order to decrease the surface resistivity of ZnO [3–9]. In this study, the properties of Al doped ZnO (ZAO) films were investigated. The purpose
*
Corresponding author. Address: International Innovation Center, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan. Tel./fax: +81 75 753 5259. E-mail address: [email protected] (A. Ide-Ektessabi). 0168-583X/$ - see front matter 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.03.047
of this study was to optimize parameters of the RF magnetron sputtering process to obtain high quality ZAO thin films as transparent conducting electrodes. There are reports showing that the properties of thin films are mainly influenced by process parameters during sputtering, such as substrate temperature, discharge power, target–substrate distance and oxygen flow rate [9,10]. ZAO thin films were deposited by RF magnetron sputtering by changing substrate temperature and oxygen flow rate. Then, the visible light transmittance and the surface resistivity of these films were measured. In order to analyze the properties of ZAO thin films, the following methods were applied. Crystal orientation and composition of these films were analyzed by X-ray diffraction (XRD) analysis and Rutherford back scattering spectrometry (RBS), respectively. X-ray photoelectron spectroscopy (XPS) was used for determining the chemical state of the surface of these films.
S. Kobayakawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 249 (2006) 536–539
2. Experimental method A RF magnetron sputtering system was used in this experiment. The diameter and thickness of the sputtering targets of ZAO and ITO were 101.6 mm and 5 mm. The ZAO target contained 2 wt% Al2O3. The ITO target consisted of 90 wt% In2O3 and 10 wt% SnO2. The standard sputtering parameters in this study are presented below. The substrate temperature was room temperature. The discharge power was 3.7 W/cm2. Argon gas was used as ambient gas in the chamber. The distance between target and substrate was 215 mm. Argon gas was introduced into the chamber with flow rate of 10.4 cm and kept at a pressure 0.10 Pa. The samples fabricated under the standard condition will be referred to as ZAO-1 and ITO-1, respectively. First, only the substrate temperature was changed to 373 K, 473 K and 623 K to prepare a sample (ZAO-2, ITO2 (373 K), ZAO-3 (473 K), and ZAO-4 (623 K)). Second, samples were fabricated using Ar gas containing 25% oxygen (ZAO-5 and ITO-3). Finally, discharge power was reduced to 1.85 W/cm2 to sputter (ZAO-6). The ZAO standard sample was annealed at 673 K to investigate the influence of annealing (ZAO-7). In order to clean up the surface of the target, 10 min presputtering with a closed shutter at a discharge power of 3.7 W/cm2 was followed by 20 min deposition to fabricate thin films. Visible light transmittance was measured using a V-560 US–VS spectro photometer (JASCO). The measurement range was from 380 nm to 820 nm at an interval of 1 nm. Visible light transmittance (mean value) was converted into the value of the layers with thickness of 100 nm in order to compensate for the effect of a difference of thickness. The equipment to measure the surface resistivity was Loresta-GP (Mitsubishi Chemical) using the linear four-point probe method. To measure the thickness, the surface profilometer (Taylor Hobson, Form Taly Surf Series2) was used. For the measurement of the composition of the films, Rutherford backscattering spectrometry (RBS) was performed. A 2 MeV 4He2+ ion beam was applied for this experiment. X-ray diffraction (XRD) analysis was applied to determine the crystal structure of these films using CuKa line in the Bragg angle range from 30 to 90 with a MAC. Science M03X. The chemical bonding of the films was investigated by X-ray photoelectron spectroscopy (XPS) with a MgKa radiation source (Shimazu Axis 165S). 3. Results and discussion 3.1. Optical and electrical properties of the films Thin films were fabricated while changing the substrate temperatures (373 K, 473 K, and 623 K) in order to investigate the effect of the substrate temperature on the optical and electrical characteristics. Table 1 shows the visible light transmittance and surface resistivity of all samples which will be discussed below. In the case of ZAO, as substrate temperature increased, the resistivities became lower than
537
Table 1 Visible light transmittance and surface resistivity Sample
Film thickness (nm)
Resistivity (X/cm2)
Transmittance (%)
ZAO
ZAO-1 ZAO-2 ZAO-3 ZAO-4 ZAO-5 ZAO-6 ZAO-7
123.7 142.0 146.0 130.0 123.7 240.0 97.7
3.38 · 103 2.53 · 102 2.93 · 102 4.53 · 102 – 2.76 · 106 6.54 · 104
89.2 89.9 90.1 88.3 89.5 91.9 80.8
ITO
ITO-1 ITO-2 ITO-3
192.0 180.0 238.0
2.37 · 101 2.71 · 101 8.58 · 106
90.2 89.5 89.6
that of the standard sample. The lowest resistivity was 2.53 · 102 X/cm2 at 373 K. But as substrate temperature increased further, the resistivity increased. This result suggests that the optimum substrate temperature to minimize the resistivity was around 373 K. This result is in good agreement with the conclusion of the experiments conducted by Igasaki et al. [11]. The minimum value of resistivity of ITO samples was 2.37 · 101 X/cm2 at room temperature in Table 1. When the ZAO film deposited under the standard conditions was annealed at 673 K for 2 h, the resistivity became so high that the resistivity could not be measured with the Loresta-GP. This is attributed to the fact that in the case of films annealed in the air, oxygen was incorporated into films and the donorconcentration resulting from interstitial zinc atoms and oxygen vacancies decreased significantly. In the case of ITO, the same tendency was reported by Minami et al. [12]. ZAO and ITO films were deposited in an ambient of argon gas with a 25% partial pressure of oxygen. In comparison with standard samples, the resistivities of both films were considerably increased and the mean value of visible light transmittance became slightly higher. This may be due to the fact that the amount of oxygen vacancies as donors was reduced as a result of introducing oxygen into these films. The film which was deposited at 1.85 W/ cm2 showed a lower transmittance and higher resistivity than those of films fabricated at 3.7 W/cm2. From the result of RBS, the value of Al/Zn of the film deposited at 3.7 W/cm2 was 0.06 and that of the film deposited at 1.85 W/cm2 was 0.03. The proportion of Al content was reduced as the discharge power was reduced. The substitutional aluminum atoms act as donors in ZAO film so the rise of resistivity was considered to be attributable to the reduction of the Al content. 3.2. Crystal structure and the chemical states of the ZAO films XRD spectra of ZAO films (from ZAO-1 to ZAO-7) deposited on Si substrates under the various condition are shown in Fig. 1. From the XRD spectra, all ZAO films had only the (0 0 2) orientation. In the case of the samples
538
S. Kobayakawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 249 (2006) 536–539
intensity of (0 0 2) crystalline ZnO (the first peak) in the XPS Zn2p3/2 spectrum. The same tendency was reported about ITO by Park et al. [13]. 4. Conclusions
Fig. 1. XRD spectra of ZAO films deposited under various conditions.
deposited at 373 K and 473 K, which showed the lowest resistivity, the intensity of the (0 0 2) peak decreased significantly. On the contrary, in the case of the annealed sample which showed a higher resistivity, the intensity of (0 0 2) peak were stronger than that of the standard sample. The same tendency was observed in the case of the sample deposited with discharge gas including oxygen which showed a high resistivity. From these result, it was concluded that the resistivity decreased as the crystalline structure became closer to the amorphous phase. The Zn2p3/2 XPS spectra of ZAO-3 and ZAO-6 are shown in Fig. 2. The first peaks at 1020.2 eV and 1021.3 eV correspond to (0 0 2) crystalline ZnO and the second peaks at 1020.9 eV and 1021.6 eV correspond to amorphous ZnO. The difference in binding energy of these two samples seemed to depend on charge shifts rather than chemical shifts. These facts corresponded to the result of XRD mentioned earlier. The sample sputtered with ambient gas containing 25% oxygen shows a strong (0 0 2) diffraction peak in the XRD spectrum and higher intensity of (0 0 2) crystalline ZnO (the first peak) in the XPS Zn2p3/2 spectrum. On the contrary, the sample sputtered at 473 K shows smaller (0 0 2) peak in XRD and a lower
In this study thin films of ZAO were prepared by RF magnetron sputtering by changing the substrate temperature and oxygen flow rate. The properties of these films were investigated. The optimum substrate temperature in the sputtering process was estimated to be around 373 K. Annealing in the air had negative effects on the electrical characteristics of films because oxygen was introduced into films and the concentration of vacancies as donor sites was decreased. In order to avoid introduction of oxygen into the films, the films should be annealed in vacuum. A smaller oxygen flow rate is desirable rather than 25% because the oxygen flow rate in the ambient gas is directly connected with oxygen vacancies as donor sites in the thin films. ITO as used in practice has a surface resistivity of 20 X/ cm2. This study shows that when the sputtering parameters were optimized, ZAO thin film showed good optical and electrical characteristics which are close to those of ITO. Sputtering parameters optimized, ZAO thin film is a potential material to be used for transparent conducting electrodes for PDPs. Acknowledgements The authors are grateful to Mr. Y. Tsukuda and the members at Sanwa Kenma Ltd. for their assistance in preparing the samples. We would like to appreciate Mr. T. Takaishi at Kyoto Research Park Corp. for his assistance with the XRD. The RBS measurement was performed at the Quantum Science Engineering Center, Graduate School of Engineering, Kyoto University. We also would like to thank Mr. H. Tsuchida. We would like to thank Mr. H. Tsuji at Venture Business Laboratory, Kyoto University for the XPS measurements.
Fig. 2. XPS spectra of ZAO films deposited under various conditions.
S. Kobayakawa et al. / Nucl. Instr. and Meth. in Phys. Res. B 249 (2006) 536–539
References [1] K. Ellmer, J. Phys. D Appl. Phys. 34 (2001) 3097. [2] S. Shirakata, T. Sakemi, K. Awai, T. Yamamoto, Thin Solid Films 445 (2003) 278. [3] Y. Qu, T.A. Gessert, K. Ramanathan, R.G. Dhere, R. Noufi, T.J. Coutts, J .Vac. Sci. Technol. A 11 (4) (1993) 996. [4] K. Tominaga, N. Umezu, I. Mori, T. Ushiro, T. Moriga, I. Nakabayashi, J. Vac. Sci. Technol. A 16 (3) (1998) 1213. [5] M. Miyazaki, K. Sato, A. Mitsui, H. Nishimura, J. Non-Cryst. Solids 218 (1997) 323. [6] T. Yamamoto, T. Sakemi, K. Awai, S. Shirakata, Thin Solid Films 451–452 (2004) 439.
539
[7] K. Matsubara, P. Fons, K. Iwata, A. Yamada, S. Niki, Thin Solid Films 422 (2002) 176. [8] H. Agura, A. Suzuki, T. Matsushita, T. Aoki, M. Okuda, Thin Solid Films 445 (2003) 263. [9] Z.C. Jin, I. Hamberg, C.G. Granqvist, J. Appl. Phys. 64 (10) (1988) 5117. [10] M. Chen, Z.L. Pei, C. Sun, J. Gong, R.F. Huang, L.S. Wen, J. Mater. Sci. Eng. B 85 (8) (2001) 212. [11] Y. Igasaki, H. Saito, J. Appl. Phys. 69 (4) (1991) 2190. [12] H. Nanto, T. Minami, S. Orito, S. Takata, J. Appl. Phys. 63 (8) (1988) 2711. [13] Y.C. Park, Y.S. Kim, H.K. Seo, S.G. Ansari, H.S. Shin, Surf. Coat. Technol. 161 (2002) 62.