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Fabrication and measurement of large-area sub-wavelength structures with broadband and wide-angle antireflection effect
Microelectronic Engineering 87 (2010) 1323–1327
Contents lists available at ScienceDirect
Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee
Fabrication and measurement of large-area sub-wavelength structures with broadband and wide-angle antireflection effect Yung-Pin Chen, Hsin-Chieh Chiu, Guan-Yu Chen, Chieh-Hsiu Chiang, Ching-Tung Tseng, Chih-Hsien Lee, Lon A. Wang * Photonics and Nano-Structure Lab., Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
a r t i c l e
i n f o
Article history: Received 14 October 2009 Received in revised form 13 December 2009 Accepted 14 December 2009 Available online 23 December 2009 Keywords: Antireflection Sub-wavelength structures Interference lithography Varied-angle reflectometer
a b s t r a c t In this paper, large-area two-dimensional sub-wavelength structures (SWS) on Si substrates are fabricated by combining interference lithography and reactive ion etching. The average reflectance of the SWS samples is less than 2.87% with broadband operation from 250 to 1200 nm. It also shows good uniformity over the whole patterned area by measuring 16 divided SWS areas. The reflectance variations with different incident angles are measured by our varied-angle reflectometer and the reflectance is lower than 5% for the incident angles smaller than 50° over the broadband region. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction Conventionally, a polished surface of an optical element can reduce the scattering loss effectively. However, there is still a Fresnel reflection loss at the interface between two different materials. To reduce such a loss, thin-film antireflection coating (ARC) has been used widely in a lot of optical applications such as LCD displays, solar cells. The performance of ARC is dependent on the working wavelength and incident angle, and generally the working ranges of bandwidth and angle are limited owing to the availability of desirable refractive indices. An alternative solution to the above problems limited by thin-film coating is to use sub-wavelength structures (SWS) to provide antireflection effect with broad bandwidth and wide incident angles. Two-dimensional (2D) SWS used as the antireflection layer is an attractive artificial optical element. The SWS could be applied to the surfaces of LED, solar cells and display panels to decrease the reflection and increase the light efficiency. The profiles of SWS could be controlled to make the effective refractive index changed gradually from the index of incident medium to that of substrate [1,2]. There are a lot of methods to fabricate SWS such as e-beam lithography [3,4], anodic porous alumina [5,6] and nanosphere coating [7–10]. Even the structures were replicated directly from * Corresponding author. E-mail address: [email protected] (L.A. Wang). 0167-9317/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2009.12.054
the compound eyes of a fly by atomic layer deposition [11]. Among the reported literatures, many SWS of random or quasi-random patterns were made by employing unconventional or non-industrial standard semiconductor processing on Si wafers [12–15]. Though the average reflectance could be obtained lower than 1% over a wide spectral range (300–2500 nm) and incident angles (0–60°) [13], the fabrication of duplicated patterns over a large area may potentially pose a problem. Conversely, interference lithography (IL) is a powerful method, fully compatible with the standard semiconductor industry, to offer the large-area fabrication of SWS with different dimensions and periodic arrangements in a fast and economical way. IL was reported to fabricate 2D periodic patterns, but the reflectance was not low enough for broadband applications due to the flat top surfaces and small aspect ratios of rods [16]. Recently it has reported that by using IL and with the improvement of adopting small-apex nanocones with high aspect ratio, the reflectance could reach 1% from 400 to 1000 nm in wavelength and less than 4% over the entire usable absorption range of crystalline silicon for incident angle up to 45° [17]. In this work, the large-area SWS would be defined by using twobeam IL with periodicity of 250 nm, and the patterns would be transferred to a Si substrate by utilizing dry etching. The experimental results of the SWS with smaller aspect ratios show good antireflection performance, smaller than 5% for broadband (250– 1200 nm) and wide angles (0–45°) operation.
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Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
2. Experiments The SWS patterns were defined on photoresist (PR), PFI-34A2 from Sumitomo Chemical Co., by utilizing IL. In order to eliminate the reflective light between PR and substrate, an ARC layer, XHRiC11 from Brewer Science Co., was coated on the substrate to reduce the reflectance. Since the PR and ARC could not bear the plasma etching for a long time, a SiO2 layer used as the etching mask was grown on the Si wafer by thermal oxidation to facilitate pat-
tern transfer. There were three thin-film layers, SiO2, ARC and PR, on the top of Si substrate with SiO2 the lowest layer. The 2D SWS were fabricated by utilizing two-beam IL and the substrate was rotated with 90° between two exposures. Based on the basic principle of two-beam interference, the period of patterns could be determined by the wavelength and incident angle of exposure beams. The period of gratings could be expressed as
K¼
k 2 sin h
ð1Þ
Fig. 1. SEM images of: (a) PR patterns, (b) post arrays without ARC in the valley, (c) SiO2 patterns and (d) Si post arrays.
Fig. 2. Schematic diagram of the homemade varied-angle reflectometer. (a) Normal incident mode with a focusing beam to scan the sample, (b) varied-angle mode to measure the reflectance with various incident angles.
Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
1325
Fig. 3. Reflectance comparison between the polished silicon wafer and the silicon wafer with SWS.
where K is the period of gratings, k is the wavelength of incident light, and h is the incident angle of two symmetrical beams. The light source of IL was an argon ion laser operating at 363.8 nm, and the period of gratings was 250 nm with the incident angle
about 46°. After the first exposure, we rotated the sample by 90° and applied the same dosage for the second exposure. Then the post or hole arrays were fabricated over 25 25 mm2 with different resultant exposure dosages. In this experiment, the post arrays were
Fig. 4. Reflectance at different positions was measured with bandwidth from 350 to 750 nm at normal incidence.
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Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
desired and the dosage was chosen 32 mJ/cm2 in each exposure. After the exposure and development processes, the PR post arrays were obtained as shown in Fig. 1a. To transfer the PR patterns into the substrate, two different etching instruments, reactive ion etch (RIE) (RIE-10N, SAMCO) and inductive couple plasma (ICP) RIE (MESC Multiplex ICP, Version 2, STS), were utilized to remove the ARC and SiO2 layers and etch the Si substrate. First, the CF4/O2 and CF4 plasmas of RIE with flow rate 25 sccm and RF-power at 150 and 70 W were used to remove the ARC and SiO2 layers which were not covered by PR patterns. Fig. 1b shows that the ARC was removed and the residual PR/ ARC post arrays still had good shape and arrangement. After removing the SiO2 layer, the residual polymers, PR and ARC, were cleaned by O2 plasma and the SiO2 post arrays could be obtained as shown in Fig. 1c. These SiO2 post arrays were used as etching mask in the following silicon etching. The Si substrate was etched by the SF6/O2 plasma and passivated by C4F8 plasma in the ICP-RIE system. The etching recipe was SF6/O2 with flow rate 60/10 sccm, coil power 600 W and plane power 3.5 W, and the passivation recipe was C4F8 with 50 sccm, coil power 600 W and no plane power. Since the SF6/O2 plasma was an isotropic etching, the passivation plasma could protect the sidewall of structures to prevent the post being thinned during etching process. By repeating 15 cycles of the etching and passivating with 7 and 7.2 s, the Si post arrays could be obtained with desired depth. After performing all etching steps, the sample was cleaned by O2 plasma to remove the deposition covered on the surface of SWS during the passivation step. Then the sample was dipped into the buffer oxide etching for 5 min to remove the residual SiO2 layer. Finally, the 2D SWS on Si were obtained as shown in Fig. 1d. The post structures were of bell-like shape which was narrow at the top and gradually broadened downward. 3. Results and discussion The reflectance of SWS was measured by two kinds of measurement apparatuses. One is a commercial spectrophotometer (U3501, Hitachi) and the other is our homemade varied-angle reflectometer as schematically shown in Fig. 2. A Xenon lamp with the bandwidth from 350 to 750 nm and a commercial spectrometer (HR4000, Ocean Optics) were used as the light source and analyzer, respectively. The normal incident mode as shown in Fig. 2a could measure the uniformity of reflectance on the full area of sample
by utilizing a focusing beam to scan the sample. When the beamsplitter (BS) was replaced by a SWS sample, which was located on the center of rotation stage, the reflectance with different incident angles could be measured by rotating the two arms as shown in Fig. 2b. Fig. 3 shows the reflectance of polished Si and SWS on Si measured by the commercial spectrophotometer at the incident angle of 5°. The average reflectance of SWS on Si from 250 to 1200 nm was less than 2.87% which is much lower than that of original polished Si. This result implies that the SWS with bell-like shape have a broadband antireflection effect since the effective refractive index is increasing gradually from air to Si substrate. Fig. 4 shows 16 spectra with normal incidence measured from 400 to 750 nm which correspond to the marked areas as shown in the inlet figure. It shows that the reflectance of most areas was less than 5%, even less than 1% in some areas. There was a little difference at different divided areas because of the bull’s eye effect during Si etching. However, the overall reflectance was still much lower than that of original Si substrate. The reflectance at different incident angles was also measured from 10° to 75° with an increment of 5°. Fig. 5a shows the reflectance with wavelength ranging from 350 to 750 nm at different incident angles. When the incident angle was smaller than 50°, the reflectance was lower than 5% over the broadband region. The reflectance at some different incident angles is redrawn in Fig. 5b. The higher order diffraction light appearing at large incident angles was not collected by our varied-angle reflectometer. Thus the reflectance in short wavelength range was decreasing and more wavelengths would have higher order diffraction with the incident angle increasing. If the period of SWS would be smaller, the higher order diffraction could be vanished. For the transfer of patterns to flexible substrates in some practical applications, the imprint process is preferred. Therefore, the profiles of SWS on Si molds should be neither too thin nor too high to prevent the damage of mold during imprinting. Since the reflectance could also be decreased by controlling the profile of SWS without the need of nanotips [18], our bell-like SWS may provide better mechanical strength during imprinting while keeping good antireflective effect. It may also save time because very deep etching is not needed. In addition, it is expected that the performance of our current results could be improved by controlling the recipes of ICP-RIE to obtain the optimal profiles of SWS.
Fig. 5. (a) Reflectance of SWS at various incident angles and wavelengths. (b) The reflectance is lower than 5% for the incident angles smaller than 50° in wavelengths ranging from 350 to 750 nm.
Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
4. Conclusion We demonstrate a method to fabricate large-area SWS on a silicon substrate by utilizing IL and ICP-RIE. The post structures with bell-like shape were obtained by controlling the processing recipes, and the SWS on silicon showed good antireflection performance. The average reflectance was reduced from 44.34% to 2.87% between 250 and 1200 nm in wavelength. The uniformity of the SWS was good over the whole patterned area, and the reflectance was less than 5% when the incident angle smaller than 50° for wavelengths ranging from 350 to 750 nm. References [1] E.B. ScienceGrann, M.G. Moharam, D.A. Pommet, J. Opt. Soc. Am. 12 (2) (1995) 333. [2] S.A. Boden, D.M. Bagnall, Appl. Phys. Lett. 93 (2008) 133108.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]
1327
Y. Kanamori, M. Sasaki, K. Hane, Opt. Lett. 24 (20) (1999) 1422. H. Toyota, K. Takahara, M. Okano, et al., Jpn. J. Appl. Phys. 40 (7B) (2001) L747. H. Sai, H. Fujii, K. Arafune, et al., Appl. Phys. Lett. 88 (2006) 201116. T. Yanagishita, T. Kondo, K. Nishio, et al., J. Vac. Sci. Technol. B 26 (6) (2008) 1856. C.H. Sun, W.L. Min, N.C. Linn, et al., Appl. Phys. Lett. 91 (2007) 231105. H.L. Chen, S.Y. Chuang, C.H. Lin, et al., Opt. Express 15 (22) (2007) 14793. D.H. Wan, H.L. Chen, S.Y. Chuang, et al., J. Phys. Chem. C 112 (2008) 20567. Y.H. Pai, F.S. Meng, C.J. Lin, et al., Nanotechnology 20 (2009) 035303. J. Huang, X. Wang, Z.L. Wang, Nanotechnology 19 (2008) 025602. H. Sai, H. Fujii, K. Arafune, Y. Ohshita, Y. Kanamori, H. Yugami, M. Yamaguchi, Jpn. J. Appl. Phys. 46 (6A) (2007) 3333. Y.F. Huang, S. Chattopadhyay, Y.J. Jen, et al., Nat. Nanotechnol. 2 (12) (2007) 770. W.L. Min, P. Jiang, B. Jiang, Nanotechnology 19 (2008) 475604. W.L. Min, B. Jiang, P. Jiang, Adv. Mater. 20 (20) (2008) 3914. K. Hadobás, S. Kirsch, A. Carl, M. Acet, E.F. Wassermann, Nanotechnology 11 (2000) 161. Q. Chen, G. Hubbard, P.A. Shields, C. Liu, D.W.E. Allsopp, W.N. Wang, S. Abbott, Appl. Phys. Lett. 94 (2009) 263118. S.A. Bodenaand, D.M. Bagnall, Appl. Phys. Lett. 93 (2008) 133108.
Contents lists available at ScienceDirect
Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee
Fabrication and measurement of large-area sub-wavelength structures with broadband and wide-angle antireflection effect Yung-Pin Chen, Hsin-Chieh Chiu, Guan-Yu Chen, Chieh-Hsiu Chiang, Ching-Tung Tseng, Chih-Hsien Lee, Lon A. Wang * Photonics and Nano-Structure Lab., Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
a r t i c l e
i n f o
Article history: Received 14 October 2009 Received in revised form 13 December 2009 Accepted 14 December 2009 Available online 23 December 2009 Keywords: Antireflection Sub-wavelength structures Interference lithography Varied-angle reflectometer
a b s t r a c t In this paper, large-area two-dimensional sub-wavelength structures (SWS) on Si substrates are fabricated by combining interference lithography and reactive ion etching. The average reflectance of the SWS samples is less than 2.87% with broadband operation from 250 to 1200 nm. It also shows good uniformity over the whole patterned area by measuring 16 divided SWS areas. The reflectance variations with different incident angles are measured by our varied-angle reflectometer and the reflectance is lower than 5% for the incident angles smaller than 50° over the broadband region. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction Conventionally, a polished surface of an optical element can reduce the scattering loss effectively. However, there is still a Fresnel reflection loss at the interface between two different materials. To reduce such a loss, thin-film antireflection coating (ARC) has been used widely in a lot of optical applications such as LCD displays, solar cells. The performance of ARC is dependent on the working wavelength and incident angle, and generally the working ranges of bandwidth and angle are limited owing to the availability of desirable refractive indices. An alternative solution to the above problems limited by thin-film coating is to use sub-wavelength structures (SWS) to provide antireflection effect with broad bandwidth and wide incident angles. Two-dimensional (2D) SWS used as the antireflection layer is an attractive artificial optical element. The SWS could be applied to the surfaces of LED, solar cells and display panels to decrease the reflection and increase the light efficiency. The profiles of SWS could be controlled to make the effective refractive index changed gradually from the index of incident medium to that of substrate [1,2]. There are a lot of methods to fabricate SWS such as e-beam lithography [3,4], anodic porous alumina [5,6] and nanosphere coating [7–10]. Even the structures were replicated directly from * Corresponding author. E-mail address: [email protected] (L.A. Wang). 0167-9317/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2009.12.054
the compound eyes of a fly by atomic layer deposition [11]. Among the reported literatures, many SWS of random or quasi-random patterns were made by employing unconventional or non-industrial standard semiconductor processing on Si wafers [12–15]. Though the average reflectance could be obtained lower than 1% over a wide spectral range (300–2500 nm) and incident angles (0–60°) [13], the fabrication of duplicated patterns over a large area may potentially pose a problem. Conversely, interference lithography (IL) is a powerful method, fully compatible with the standard semiconductor industry, to offer the large-area fabrication of SWS with different dimensions and periodic arrangements in a fast and economical way. IL was reported to fabricate 2D periodic patterns, but the reflectance was not low enough for broadband applications due to the flat top surfaces and small aspect ratios of rods [16]. Recently it has reported that by using IL and with the improvement of adopting small-apex nanocones with high aspect ratio, the reflectance could reach 1% from 400 to 1000 nm in wavelength and less than 4% over the entire usable absorption range of crystalline silicon for incident angle up to 45° [17]. In this work, the large-area SWS would be defined by using twobeam IL with periodicity of 250 nm, and the patterns would be transferred to a Si substrate by utilizing dry etching. The experimental results of the SWS with smaller aspect ratios show good antireflection performance, smaller than 5% for broadband (250– 1200 nm) and wide angles (0–45°) operation.
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Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
2. Experiments The SWS patterns were defined on photoresist (PR), PFI-34A2 from Sumitomo Chemical Co., by utilizing IL. In order to eliminate the reflective light between PR and substrate, an ARC layer, XHRiC11 from Brewer Science Co., was coated on the substrate to reduce the reflectance. Since the PR and ARC could not bear the plasma etching for a long time, a SiO2 layer used as the etching mask was grown on the Si wafer by thermal oxidation to facilitate pat-
tern transfer. There were three thin-film layers, SiO2, ARC and PR, on the top of Si substrate with SiO2 the lowest layer. The 2D SWS were fabricated by utilizing two-beam IL and the substrate was rotated with 90° between two exposures. Based on the basic principle of two-beam interference, the period of patterns could be determined by the wavelength and incident angle of exposure beams. The period of gratings could be expressed as
K¼
k 2 sin h
ð1Þ
Fig. 1. SEM images of: (a) PR patterns, (b) post arrays without ARC in the valley, (c) SiO2 patterns and (d) Si post arrays.
Fig. 2. Schematic diagram of the homemade varied-angle reflectometer. (a) Normal incident mode with a focusing beam to scan the sample, (b) varied-angle mode to measure the reflectance with various incident angles.
Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
1325
Fig. 3. Reflectance comparison between the polished silicon wafer and the silicon wafer with SWS.
where K is the period of gratings, k is the wavelength of incident light, and h is the incident angle of two symmetrical beams. The light source of IL was an argon ion laser operating at 363.8 nm, and the period of gratings was 250 nm with the incident angle
about 46°. After the first exposure, we rotated the sample by 90° and applied the same dosage for the second exposure. Then the post or hole arrays were fabricated over 25 25 mm2 with different resultant exposure dosages. In this experiment, the post arrays were
Fig. 4. Reflectance at different positions was measured with bandwidth from 350 to 750 nm at normal incidence.
1326
Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
desired and the dosage was chosen 32 mJ/cm2 in each exposure. After the exposure and development processes, the PR post arrays were obtained as shown in Fig. 1a. To transfer the PR patterns into the substrate, two different etching instruments, reactive ion etch (RIE) (RIE-10N, SAMCO) and inductive couple plasma (ICP) RIE (MESC Multiplex ICP, Version 2, STS), were utilized to remove the ARC and SiO2 layers and etch the Si substrate. First, the CF4/O2 and CF4 plasmas of RIE with flow rate 25 sccm and RF-power at 150 and 70 W were used to remove the ARC and SiO2 layers which were not covered by PR patterns. Fig. 1b shows that the ARC was removed and the residual PR/ ARC post arrays still had good shape and arrangement. After removing the SiO2 layer, the residual polymers, PR and ARC, were cleaned by O2 plasma and the SiO2 post arrays could be obtained as shown in Fig. 1c. These SiO2 post arrays were used as etching mask in the following silicon etching. The Si substrate was etched by the SF6/O2 plasma and passivated by C4F8 plasma in the ICP-RIE system. The etching recipe was SF6/O2 with flow rate 60/10 sccm, coil power 600 W and plane power 3.5 W, and the passivation recipe was C4F8 with 50 sccm, coil power 600 W and no plane power. Since the SF6/O2 plasma was an isotropic etching, the passivation plasma could protect the sidewall of structures to prevent the post being thinned during etching process. By repeating 15 cycles of the etching and passivating with 7 and 7.2 s, the Si post arrays could be obtained with desired depth. After performing all etching steps, the sample was cleaned by O2 plasma to remove the deposition covered on the surface of SWS during the passivation step. Then the sample was dipped into the buffer oxide etching for 5 min to remove the residual SiO2 layer. Finally, the 2D SWS on Si were obtained as shown in Fig. 1d. The post structures were of bell-like shape which was narrow at the top and gradually broadened downward. 3. Results and discussion The reflectance of SWS was measured by two kinds of measurement apparatuses. One is a commercial spectrophotometer (U3501, Hitachi) and the other is our homemade varied-angle reflectometer as schematically shown in Fig. 2. A Xenon lamp with the bandwidth from 350 to 750 nm and a commercial spectrometer (HR4000, Ocean Optics) were used as the light source and analyzer, respectively. The normal incident mode as shown in Fig. 2a could measure the uniformity of reflectance on the full area of sample
by utilizing a focusing beam to scan the sample. When the beamsplitter (BS) was replaced by a SWS sample, which was located on the center of rotation stage, the reflectance with different incident angles could be measured by rotating the two arms as shown in Fig. 2b. Fig. 3 shows the reflectance of polished Si and SWS on Si measured by the commercial spectrophotometer at the incident angle of 5°. The average reflectance of SWS on Si from 250 to 1200 nm was less than 2.87% which is much lower than that of original polished Si. This result implies that the SWS with bell-like shape have a broadband antireflection effect since the effective refractive index is increasing gradually from air to Si substrate. Fig. 4 shows 16 spectra with normal incidence measured from 400 to 750 nm which correspond to the marked areas as shown in the inlet figure. It shows that the reflectance of most areas was less than 5%, even less than 1% in some areas. There was a little difference at different divided areas because of the bull’s eye effect during Si etching. However, the overall reflectance was still much lower than that of original Si substrate. The reflectance at different incident angles was also measured from 10° to 75° with an increment of 5°. Fig. 5a shows the reflectance with wavelength ranging from 350 to 750 nm at different incident angles. When the incident angle was smaller than 50°, the reflectance was lower than 5% over the broadband region. The reflectance at some different incident angles is redrawn in Fig. 5b. The higher order diffraction light appearing at large incident angles was not collected by our varied-angle reflectometer. Thus the reflectance in short wavelength range was decreasing and more wavelengths would have higher order diffraction with the incident angle increasing. If the period of SWS would be smaller, the higher order diffraction could be vanished. For the transfer of patterns to flexible substrates in some practical applications, the imprint process is preferred. Therefore, the profiles of SWS on Si molds should be neither too thin nor too high to prevent the damage of mold during imprinting. Since the reflectance could also be decreased by controlling the profile of SWS without the need of nanotips [18], our bell-like SWS may provide better mechanical strength during imprinting while keeping good antireflective effect. It may also save time because very deep etching is not needed. In addition, it is expected that the performance of our current results could be improved by controlling the recipes of ICP-RIE to obtain the optimal profiles of SWS.
Fig. 5. (a) Reflectance of SWS at various incident angles and wavelengths. (b) The reflectance is lower than 5% for the incident angles smaller than 50° in wavelengths ranging from 350 to 750 nm.
Y.-P. Chen et al. / Microelectronic Engineering 87 (2010) 1323–1327
4. Conclusion We demonstrate a method to fabricate large-area SWS on a silicon substrate by utilizing IL and ICP-RIE. The post structures with bell-like shape were obtained by controlling the processing recipes, and the SWS on silicon showed good antireflection performance. The average reflectance was reduced from 44.34% to 2.87% between 250 and 1200 nm in wavelength. The uniformity of the SWS was good over the whole patterned area, and the reflectance was less than 5% when the incident angle smaller than 50° for wavelengths ranging from 350 to 750 nm. References [1] E.B. ScienceGrann, M.G. Moharam, D.A. Pommet, J. Opt. Soc. Am. 12 (2) (1995) 333. [2] S.A. Boden, D.M. Bagnall, Appl. Phys. Lett. 93 (2008) 133108.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]
1327
Y. Kanamori, M. Sasaki, K. Hane, Opt. Lett. 24 (20) (1999) 1422. H. Toyota, K. Takahara, M. Okano, et al., Jpn. J. Appl. Phys. 40 (7B) (2001) L747. H. Sai, H. Fujii, K. Arafune, et al., Appl. Phys. Lett. 88 (2006) 201116. T. Yanagishita, T. Kondo, K. Nishio, et al., J. Vac. Sci. Technol. B 26 (6) (2008) 1856. C.H. Sun, W.L. Min, N.C. Linn, et al., Appl. Phys. Lett. 91 (2007) 231105. H.L. Chen, S.Y. Chuang, C.H. Lin, et al., Opt. Express 15 (22) (2007) 14793. D.H. Wan, H.L. Chen, S.Y. Chuang, et al., J. Phys. Chem. C 112 (2008) 20567. Y.H. Pai, F.S. Meng, C.J. Lin, et al., Nanotechnology 20 (2009) 035303. J. Huang, X. Wang, Z.L. Wang, Nanotechnology 19 (2008) 025602. H. Sai, H. Fujii, K. Arafune, Y. Ohshita, Y. Kanamori, H. Yugami, M. Yamaguchi, Jpn. J. Appl. Phys. 46 (6A) (2007) 3333. Y.F. Huang, S. Chattopadhyay, Y.J. Jen, et al., Nat. Nanotechnol. 2 (12) (2007) 770. W.L. Min, P. Jiang, B. Jiang, Nanotechnology 19 (2008) 475604. W.L. Min, B. Jiang, P. Jiang, Adv. Mater. 20 (20) (2008) 3914. K. Hadobás, S. Kirsch, A. Carl, M. Acet, E.F. Wassermann, Nanotechnology 11 (2000) 161. Q. Chen, G. Hubbard, P.A. Shields, C. Liu, D.W.E. Allsopp, W.N. Wang, S. Abbott, Appl. Phys. Lett. 94 (2009) 263118. S.A. Bodenaand, D.M. Bagnall, Appl. Phys. Lett. 93 (2008) 133108.