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Development of 500m-length IBAD-Gd2Zr2O7 film for Y-123 coated conductors
Accepted Manuscript Development of 500m-length IBAD-Gd2Zr2O7 film for Y-123 coated conduc‐ tors S. Hanyu, Y. Iijima, H. Fuji, K. Kakimoto, T. Saitoh PII: DOI: Reference:
S0921-4534(07)00868-4 10.1016/j.physc.2007.05.020 PHYSC 124572
To appear in:
Physica C
Please cite this article as: S. Hanyu, Y. Iijima, H. Fuji, K. Kakimoto, T. Saitoh, Development of 500m-length IBAD(2007), doi: 10.1016/j.physc.2007.05.020 Gd2Zr2O7 film for Y-123 coated conductors, Physica C
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
WTP-71 / ISS2006
Version 1.2
Development of 500m-length IBAD-Gd2Zr2O7 film for Y-123 coated conductors S. Hanyu a,*, Y. Iijima a, H. Fuji a, K. Kakimoto a , T. Saitoh a a
Fujikura Ltd., 1-5-1, Kiba, Koto-ku, Tokyo 135-8512, Japan
Keywords: Y-123 coated conductors; Ion-beam-assisted deposition (IBAD); biaxially textured film PACS CODES:
74.72.Bk;
Corresponding author. Tel.: +81 3 5606 1064; fax: +81 3 5606 1512. E-mail address: [email protected] (S. Hanyu) Abstract IBAD-Gd2Zr2O7 (GZO) film was fabricated on polycrystalline Ni-based alloy tape by the IBAD-system with 110 cm x 15 cm ion source. Using long-length faraday cup array, effects of argon gas flows on ion-current densities were investigated. As a result, lower gas flow leads to higher ion-current density at the substrate in the system. Under the condition of low gas flow, 10 m (with production speed of 5 m/h), 60 m (3 m/h) and 500 m (5 m/h)-length IBAD-GZO films were fabricated and their in-plane textures were ∆φ = 15o, 13o and 18o respectively. After that, PLD-CeO2 experiments were performed on the IBAD-GZO substrates with ∆φ = 15o and 13o, and then CeO2 films with ∆φ =
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5.5o and 5.7o were achieved with the tape-speed of 5.0 m/h and 10.0 m/h, respectively.
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1.Introduction Long-length YBa2Cu3O7-x (Y-123) tapes are necessary for practical uses such as motor, generator, and transformer etc., especially in conduction cooled operation. Ion beam assisted deposition (IBAD) buffer layer is the key technology to fabricate Y-based coated conductor on non-textured substrate [1-4], because the current density of Y-123 along the grains decreases rapidly with an increasing misorientation angle [5]. The buffer layers, we adopted, consist of layers of IBAD-Gd2Zr2O7 (GZO) and Pulsed Laser Deposition (PLD)-CeO2. With this simple architecture, we are available substrates for Y-123 with high degree of texturing [6-8]. In this paper we describe developments of the large-scale IBAD system equipped with a large size (110 cm x 15 cm) ion source. And various lengths of IBAD-GZO films (10 m, 500 m and 60 m) were fabricated at several processing-speeds. Using some of the IBAD-samples, PLD-CeO2 were fabricated at tape speed of over 5.0 m/h.
2.Experimental IBAD-GZO experiments were performed with various gas-flows in the assisting ion source. Gas-flows experimented in this study were 28 sccm (7 sccm from 4 each nozzle) and 60 sccm (15 each). IBAD system in this study has 15 lanes at a deposition area. 15
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substrates were attached at each lane, and were moved back and forth by 180 times at each lane at a tape speed of 60 m/h. And substrates were polycrystalline Hastelloy C276 tapes with the size of 10 mm x 0.1 mm x 40 mm (width, thickness and length). Assisting Ar+ ions with energies of 200 eV, bombarded films with the ion incident angle of 55o during film-growth [7]. Secondly, ion-current densities were measured, by using a specially designed faraday-cup-array, with changing gas flows in the IBAD system. The faraday-cup-array in this study inclined by 55o to the substrate normal so as to face with the assisting ion source. The length of mounting frame of the faraday-cup-array was about 110 cm, and 21 probes were placed at equal spaces inside the frame. Probes and the mounting frame were biased at –30 V and +50 V respectively, to avoid the effects of secondary electrons etc. (fig.1). Then 10 m, 500 m and 60 m IBAD-GZO samples were fabricated by a reel-to-reel IBAD system, and CeO2 films were deposited by PLD on some of them as the second buffer layers. The laser used in the PLD process was Kr-F (λ = 248 nm) excimer laser. Crystalline in-plane textures (∆φ) were measured by XRD φ-scan of GZO (222) and CeO2 (220). And it is noted that, however gas-flows were changed, set-value of the ion current was constant at all experiments in this study.
3.Results and discussion
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Fig.2 shows the relationship between gas-flows and in-plane textures of IBAD-GZO films at each lane. In this figure, left side is the side of the assisting ion source and right side is the side of the sputtering ion source. It was showed that the films with 28 sccm have higher in-plane textures at almost all the lane, compared with IBAD-GZO films fabricated with 60 sccm. Since the set value of the ion current was constant, it was thought that the number of Ar+ ions, which reached at the substrate, were different depending on the gas-flows. In terms of the ion-current density, flux of Ar+ ion was measured by the faraday cup array. Fig.3 shows profiles of ion-current densities with changing gas-flows in the assisting ion source. It suggested that the lower Ar-gas-flow leads to the higher ion-current density. So, it is considered that Ar+ ions could got to the substrates more easily under 28sccm than under 60 sccm. And it is considered that divergence angle of the ion beam could be reduced with using low gas flows into the ion source for this system, since crystal alignments were promoted by more uniformed ion beams. So, IBAD-GZO film deposited with 28 sccm of gas flow had higher in-plane texture than the other. Lower gas flow in the assisting ion source is thought to be a better way to fabricate IBAD-GZO films. But lower gas flow needs higher RF power to keep the same ionic current. So, in case that the gas flow is too low, ion source becomes unstable. When
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making long-length IBAD films, we adopted 40-60 sccm of gas flow, because of long-time stability of the ion source. Table 1 shows the list of long-length IBAD-GZO films fabricated by the IBAD system in this study. For 10 m-sample, ∆φ = 15o at over 5.0 m/h of production speed have been achieved. Then 500 m sample was fabricated at 5.0 m/h and its in-plane texture was ∆φ=18o (ref. Fig.4). Compared with the thickness of 10 m-sample, that of 500 m-sample was thinner. The thickness is thought to be one of the reasons that in-plane texture of the film was ∆φ > 15o. Processing time was over 100 h for 500m-sample, while the time for 10m-sample including 70 m-dummy tape was about 15 h. The condition was thought to have changed gradually during long deposition time, and then film thickness of IBAD-GZO became thinner than expected. As a second buffer layer, PLD-CeO2 was performed on the short sample cut from IBAD-10 m-sample. At 5 m/h of process speed, in-plane texture of PLD-CeO2 reached ∆φ = 5.5 o with the thickness of 0.8 µm. To experiment PLD-CeO2 on the IBAD-GZO with ∆φ < 15o, IBAD-GZO was fabricated by changing speed of process from 5.0 m/h to 3.0 m/h. And we got IBAD-GZO with ∆φ = 13o, though thickness of the film was 1.4 µm. PLD-CeO2 was performed on the IBAD-GZO of ∆φ = 13o, and in-plane texture was ∆φ = 5.7o at 10m/h of processing-speed. Of course, CeO2 films with higher texture are preferable, but these in-plane textures were high enough to make 100-200 A-level
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coated conductor [9]. So in case 500 m-length IBAD-GZO film with ∆φ = 15o is achieved, CeO2 films with ∆φ = 5.0o-6.0o expected to fabricate at over 5.0 m/h of tape speed. 4.Summary IBAD-GZO films were fabricated by changing gas flow of assisting ion source. Under the condition of lower gas flow, higher in-plane texture film was obtained. Ion-current densities were measured by using faraday cup array with changing gas flow. The lower gas flows, the higher ion-current densities were detected. IBAD-GZO samples with 10 m, 500 m and 60 m-length, were fabricated at tape speeds of 5.5 m/h, 5.0 m/h and 3.0 m/h respectively. And their in-plane textures were 15.0o, 18.0o and 13.0o and thicknesses were 1.3, 1.0 and 1.4 µm. PLD-CeO2 was performed on the IBAD-GZO tape with ∆φ = 15o and ∆φ = 13o and got CeO2 films with ∆φ = 5.5o and ∆φ = 5.7o.
Acknowledgement This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) as Collaborative Research and Development of Fundamental Technologies for Superconductivity Applications.
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References [1] Y. Iijima, N. Tanabe, Y. Ikeno, O. Kohno, Physica C 185-189 (1991) 1959. [2] Y. Iijima, N. Tanabe, O. Kohno, Y. Ikeno, Appl. Phys. Lett. 60 (1992) 769. [3] C. P. Wang, K. B. Do, M. R. Beasley, T. H. Geballe, R. H. Hammond, Appl. Phys. Lett. 71 (1997) 2955. [4] P. N. Arendt, S. R. Foltyn, MRS Bull. 29 (2004) 543. [5] D. Dimos, P. Chaudhari, J. Mannhart, Phys. Rev. B 41 (1990) 4038. [6] S. Miyata, T. Watanabe, T. Muroga, H. Iwai, Y. Yamada, Y. Shiohara, Physica C 412-414 (2004) 824. [7] Y. Iijima, N. Kaneko, S. Hanyu, Y. Sutoh, K. Kakimoto, S. Ajimura, T. Saitoh, Physica C 445-448 (2006) 509. [8] S. Miyata, A. Ibi, R. Kuriki, M. Konishi, Y. Yamada, Y. Shiohara, Physica C 445-448 (2006) 611. [9] Y. iijima, K. Kakimoto, Y. Yamada, T. Izumi, T. Saitho, Y. Shiohara, MRS Bull. 29 (2004) 564
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Figure captions Fig.1 Schematic of faraday cup array employed in this study. (a)Probes were biased at –30 V and frame was biased at +50 V. Probe normal and assisting ion source are face to face. (b)Side view of the array with 1.1 m widths. Twenty-one probes are located at regular intervals. Fig.2 In-plane texture dependence on gas flows in the assisting ion source. At almost all the lane, higher in-plane textures were achieved with lower gas-flows. Left side of the lane is near the assisting ion source. Fig.3 Ion-current density profiles for various gas flows in the assisting ion source, measured by faraday cup array. Lower gas-flow leads to higher ion-current density. Fig.4 500 m-length IBAD-GZO film fabricated in this study with the tape speed of 5.0 m/h. In-plane texture and thickness of the film were ∆φ = 18o and 1.0 µm.
ACCEPTED MANUSCRIPT Table. 1
Table 1 In-plane texture for buffer layers with various lengths and processing speeds IBAD-GZO length thickness ∆φ (m) (µm) (deg.)
Speed (m/h)
PLD-CeO2 thickness ∆φ Speed (µm) (deg.) (m/h)
10
1.3
15
5.5
0.8
5.5
5
508
1.0
18
5.0
----
----
----
60
1.4
13
3.0
0.4
5.7
10
ACCEPTED MANUSCRIPT Fig.1 Substrate
(a)
-30V
Ar+
+50V
Faraday cup array
Assisting ion source (b)
1.1m
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In-plane texture ∆φ (deg.)
Fig.2
60 sccm 28 sccm
16 14 12 10 0
5
10
Position of the lanes (N)
15
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Density of ion current (µA)
500 400 300 12sccm 20sccm 28sccm 40sccm 48sccm 60sccm
200 100
0
10 Position of the faraday cups (N)
20
ACCEPTED MANUSCRIPT Fig.4
S0921-4534(07)00868-4 10.1016/j.physc.2007.05.020 PHYSC 124572
To appear in:
Physica C
Please cite this article as: S. Hanyu, Y. Iijima, H. Fuji, K. Kakimoto, T. Saitoh, Development of 500m-length IBAD(2007), doi: 10.1016/j.physc.2007.05.020 Gd2Zr2O7 film for Y-123 coated conductors, Physica C
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
WTP-71 / ISS2006
Version 1.2
Development of 500m-length IBAD-Gd2Zr2O7 film for Y-123 coated conductors S. Hanyu a,*, Y. Iijima a, H. Fuji a, K. Kakimoto a , T. Saitoh a a
Fujikura Ltd., 1-5-1, Kiba, Koto-ku, Tokyo 135-8512, Japan
Keywords: Y-123 coated conductors; Ion-beam-assisted deposition (IBAD); biaxially textured film PACS CODES:
74.72.Bk;
Corresponding author. Tel.: +81 3 5606 1064; fax: +81 3 5606 1512. E-mail address: [email protected] (S. Hanyu) Abstract IBAD-Gd2Zr2O7 (GZO) film was fabricated on polycrystalline Ni-based alloy tape by the IBAD-system with 110 cm x 15 cm ion source. Using long-length faraday cup array, effects of argon gas flows on ion-current densities were investigated. As a result, lower gas flow leads to higher ion-current density at the substrate in the system. Under the condition of low gas flow, 10 m (with production speed of 5 m/h), 60 m (3 m/h) and 500 m (5 m/h)-length IBAD-GZO films were fabricated and their in-plane textures were ∆φ = 15o, 13o and 18o respectively. After that, PLD-CeO2 experiments were performed on the IBAD-GZO substrates with ∆φ = 15o and 13o, and then CeO2 films with ∆φ =
ACCEPTED MANUSCRIPT
5.5o and 5.7o were achieved with the tape-speed of 5.0 m/h and 10.0 m/h, respectively.
ACCEPTED MANUSCRIPT
1.Introduction Long-length YBa2Cu3O7-x (Y-123) tapes are necessary for practical uses such as motor, generator, and transformer etc., especially in conduction cooled operation. Ion beam assisted deposition (IBAD) buffer layer is the key technology to fabricate Y-based coated conductor on non-textured substrate [1-4], because the current density of Y-123 along the grains decreases rapidly with an increasing misorientation angle [5]. The buffer layers, we adopted, consist of layers of IBAD-Gd2Zr2O7 (GZO) and Pulsed Laser Deposition (PLD)-CeO2. With this simple architecture, we are available substrates for Y-123 with high degree of texturing [6-8]. In this paper we describe developments of the large-scale IBAD system equipped with a large size (110 cm x 15 cm) ion source. And various lengths of IBAD-GZO films (10 m, 500 m and 60 m) were fabricated at several processing-speeds. Using some of the IBAD-samples, PLD-CeO2 were fabricated at tape speed of over 5.0 m/h.
2.Experimental IBAD-GZO experiments were performed with various gas-flows in the assisting ion source. Gas-flows experimented in this study were 28 sccm (7 sccm from 4 each nozzle) and 60 sccm (15 each). IBAD system in this study has 15 lanes at a deposition area. 15
ACCEPTED MANUSCRIPT
substrates were attached at each lane, and were moved back and forth by 180 times at each lane at a tape speed of 60 m/h. And substrates were polycrystalline Hastelloy C276 tapes with the size of 10 mm x 0.1 mm x 40 mm (width, thickness and length). Assisting Ar+ ions with energies of 200 eV, bombarded films with the ion incident angle of 55o during film-growth [7]. Secondly, ion-current densities were measured, by using a specially designed faraday-cup-array, with changing gas flows in the IBAD system. The faraday-cup-array in this study inclined by 55o to the substrate normal so as to face with the assisting ion source. The length of mounting frame of the faraday-cup-array was about 110 cm, and 21 probes were placed at equal spaces inside the frame. Probes and the mounting frame were biased at –30 V and +50 V respectively, to avoid the effects of secondary electrons etc. (fig.1). Then 10 m, 500 m and 60 m IBAD-GZO samples were fabricated by a reel-to-reel IBAD system, and CeO2 films were deposited by PLD on some of them as the second buffer layers. The laser used in the PLD process was Kr-F (λ = 248 nm) excimer laser. Crystalline in-plane textures (∆φ) were measured by XRD φ-scan of GZO (222) and CeO2 (220). And it is noted that, however gas-flows were changed, set-value of the ion current was constant at all experiments in this study.
3.Results and discussion
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Fig.2 shows the relationship between gas-flows and in-plane textures of IBAD-GZO films at each lane. In this figure, left side is the side of the assisting ion source and right side is the side of the sputtering ion source. It was showed that the films with 28 sccm have higher in-plane textures at almost all the lane, compared with IBAD-GZO films fabricated with 60 sccm. Since the set value of the ion current was constant, it was thought that the number of Ar+ ions, which reached at the substrate, were different depending on the gas-flows. In terms of the ion-current density, flux of Ar+ ion was measured by the faraday cup array. Fig.3 shows profiles of ion-current densities with changing gas-flows in the assisting ion source. It suggested that the lower Ar-gas-flow leads to the higher ion-current density. So, it is considered that Ar+ ions could got to the substrates more easily under 28sccm than under 60 sccm. And it is considered that divergence angle of the ion beam could be reduced with using low gas flows into the ion source for this system, since crystal alignments were promoted by more uniformed ion beams. So, IBAD-GZO film deposited with 28 sccm of gas flow had higher in-plane texture than the other. Lower gas flow in the assisting ion source is thought to be a better way to fabricate IBAD-GZO films. But lower gas flow needs higher RF power to keep the same ionic current. So, in case that the gas flow is too low, ion source becomes unstable. When
ACCEPTED MANUSCRIPT
making long-length IBAD films, we adopted 40-60 sccm of gas flow, because of long-time stability of the ion source. Table 1 shows the list of long-length IBAD-GZO films fabricated by the IBAD system in this study. For 10 m-sample, ∆φ = 15o at over 5.0 m/h of production speed have been achieved. Then 500 m sample was fabricated at 5.0 m/h and its in-plane texture was ∆φ=18o (ref. Fig.4). Compared with the thickness of 10 m-sample, that of 500 m-sample was thinner. The thickness is thought to be one of the reasons that in-plane texture of the film was ∆φ > 15o. Processing time was over 100 h for 500m-sample, while the time for 10m-sample including 70 m-dummy tape was about 15 h. The condition was thought to have changed gradually during long deposition time, and then film thickness of IBAD-GZO became thinner than expected. As a second buffer layer, PLD-CeO2 was performed on the short sample cut from IBAD-10 m-sample. At 5 m/h of process speed, in-plane texture of PLD-CeO2 reached ∆φ = 5.5 o with the thickness of 0.8 µm. To experiment PLD-CeO2 on the IBAD-GZO with ∆φ < 15o, IBAD-GZO was fabricated by changing speed of process from 5.0 m/h to 3.0 m/h. And we got IBAD-GZO with ∆φ = 13o, though thickness of the film was 1.4 µm. PLD-CeO2 was performed on the IBAD-GZO of ∆φ = 13o, and in-plane texture was ∆φ = 5.7o at 10m/h of processing-speed. Of course, CeO2 films with higher texture are preferable, but these in-plane textures were high enough to make 100-200 A-level
ACCEPTED MANUSCRIPT
coated conductor [9]. So in case 500 m-length IBAD-GZO film with ∆φ = 15o is achieved, CeO2 films with ∆φ = 5.0o-6.0o expected to fabricate at over 5.0 m/h of tape speed. 4.Summary IBAD-GZO films were fabricated by changing gas flow of assisting ion source. Under the condition of lower gas flow, higher in-plane texture film was obtained. Ion-current densities were measured by using faraday cup array with changing gas flow. The lower gas flows, the higher ion-current densities were detected. IBAD-GZO samples with 10 m, 500 m and 60 m-length, were fabricated at tape speeds of 5.5 m/h, 5.0 m/h and 3.0 m/h respectively. And their in-plane textures were 15.0o, 18.0o and 13.0o and thicknesses were 1.3, 1.0 and 1.4 µm. PLD-CeO2 was performed on the IBAD-GZO tape with ∆φ = 15o and ∆φ = 13o and got CeO2 films with ∆φ = 5.5o and ∆φ = 5.7o.
Acknowledgement This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) as Collaborative Research and Development of Fundamental Technologies for Superconductivity Applications.
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References [1] Y. Iijima, N. Tanabe, Y. Ikeno, O. Kohno, Physica C 185-189 (1991) 1959. [2] Y. Iijima, N. Tanabe, O. Kohno, Y. Ikeno, Appl. Phys. Lett. 60 (1992) 769. [3] C. P. Wang, K. B. Do, M. R. Beasley, T. H. Geballe, R. H. Hammond, Appl. Phys. Lett. 71 (1997) 2955. [4] P. N. Arendt, S. R. Foltyn, MRS Bull. 29 (2004) 543. [5] D. Dimos, P. Chaudhari, J. Mannhart, Phys. Rev. B 41 (1990) 4038. [6] S. Miyata, T. Watanabe, T. Muroga, H. Iwai, Y. Yamada, Y. Shiohara, Physica C 412-414 (2004) 824. [7] Y. Iijima, N. Kaneko, S. Hanyu, Y. Sutoh, K. Kakimoto, S. Ajimura, T. Saitoh, Physica C 445-448 (2006) 509. [8] S. Miyata, A. Ibi, R. Kuriki, M. Konishi, Y. Yamada, Y. Shiohara, Physica C 445-448 (2006) 611. [9] Y. iijima, K. Kakimoto, Y. Yamada, T. Izumi, T. Saitho, Y. Shiohara, MRS Bull. 29 (2004) 564
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Figure captions Fig.1 Schematic of faraday cup array employed in this study. (a)Probes were biased at –30 V and frame was biased at +50 V. Probe normal and assisting ion source are face to face. (b)Side view of the array with 1.1 m widths. Twenty-one probes are located at regular intervals. Fig.2 In-plane texture dependence on gas flows in the assisting ion source. At almost all the lane, higher in-plane textures were achieved with lower gas-flows. Left side of the lane is near the assisting ion source. Fig.3 Ion-current density profiles for various gas flows in the assisting ion source, measured by faraday cup array. Lower gas-flow leads to higher ion-current density. Fig.4 500 m-length IBAD-GZO film fabricated in this study with the tape speed of 5.0 m/h. In-plane texture and thickness of the film were ∆φ = 18o and 1.0 µm.
ACCEPTED MANUSCRIPT Table. 1
Table 1 In-plane texture for buffer layers with various lengths and processing speeds IBAD-GZO length thickness ∆φ (m) (µm) (deg.)
Speed (m/h)
PLD-CeO2 thickness ∆φ Speed (µm) (deg.) (m/h)
10
1.3
15
5.5
0.8
5.5
5
508
1.0
18
5.0
----
----
----
60
1.4
13
3.0
0.4
5.7
10
ACCEPTED MANUSCRIPT Fig.1 Substrate
(a)
-30V
Ar+
+50V
Faraday cup array
Assisting ion source (b)
1.1m
ACCEPTED MANUSCRIPT
In-plane texture ∆φ (deg.)
Fig.2
60 sccm 28 sccm
16 14 12 10 0
5
10
Position of the lanes (N)
15
ACCEPTED MANUSCRIPT Fig.3
Density of ion current (µA)
500 400 300 12sccm 20sccm 28sccm 40sccm 48sccm 60sccm
200 100
0
10 Position of the faraday cups (N)
20
ACCEPTED MANUSCRIPT Fig.4