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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 3 — Jan. 31, 2011
  • pp: 1680–1690
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Nonlinear dependence between the surface reflectance and the duty-cycle of semiconductor nanorod array

Yi-Hao Pai, Yu-Chan Lin, Jai-Lin Tsai, and Gong-Ru Lin  »View Author Affiliations


Optics Express, Vol. 19, Issue 3, pp. 1680-1690 (2011)
http://dx.doi.org/10.1364/OE.19.001680


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Abstract

The nonlinear dependence between the duty-cycle of semiconductor nanorod array and its surface reflectance minimization is demonstrated. The duty-cycle control on thin-SiO2 covered Si nanorod array is performed by O2- plasma pre-etching the self-assembled polystyrene nanosphere array mask with area density of 4 × 108 rod/cm−2. The 120-nm high SiO2 covered Si nanorod array is obtained after subsequent CF4/O2 plasma etching for 160 sec. This results in a tunable nanorod diameter from 445 to 285 nm after etching from 30 to 80 sec, corresponding to a varying nanorod duty-cycle from 89% to 57%. The TM-mode reflection analysis shows a diminishing Brewster angle shifted from 71° to 54° with increasing nanorod duty-cycle from 57% to 89% at 532 nm. The greatly reduced small-angle reflectance reveals a nonlinear trend with enlarging duty-cycle, leading to a minimum surface reflectance at nanorod duty-cycle of 85%. Both the simulation and experiment indicate that such a surface reflectance minimum is even lower than that of a uniformly SiO2 covered Si substrate on account of its periodical nanorod array architecture with tuned duty-cycle.

© 2011 OSA

1. Introduction

During the past decades, both the roughened and ordered topographic geometries of low-k dielectric materials have been comprehensively investigated as an alternative key to manipulate the surface reflection and transmittance [1

1. G.-R. Lin, Y. H. Pai, and C. T. Lin, “Microwatt MOSLED using SiOx with buried Si nanocrystals on Si nano-pillar array,” J. Lightwave Technol. 26(11), 1486–1491 (2008). [CrossRef]

4

4. J. Xiang, W. Lu, Y.-J. Hu, Y. Wu, H. Yan, and C.-M. Lieber, “Ge/Si nanowire heterostructures as high-performance field-effect transistors,” Nature 441(7092), 489–493 (2006). [CrossRef] [PubMed]

]. In application, these low-dimensional nanostructures have been used to construct numerous optical devices such as surface roughened light-emitting diodes, high-efficiency field emitters, and photovoltaic cells, etc. Up to now, versatile low-dimensional nanostructure arrays with extremely low reflectance are extensively utilized to replace the traditional multi-layered coating with excellent anti-reflection (AR) ability for improving the performance of aforementioned devices. One of these intriguing geometries is the silicon-based nanostructure array reported by Kanamori et al. [5

5. Y. Kanamori, M. Sasaki, and K. Hane, “Broadband antireflection gratings fabricated upon silicon substrates,” Opt. Lett. 24(20), 1422–1424 (1999). [CrossRef]

,6

6. Y. Kanamori, M. Ishimori, and K. Hane, “High efficient light-emitting diodes with antireflection subwavelength gratings,” IEEE Photon. Technol. Lett. 14(8), 1064–1066 (2002). [CrossRef]

]. By utilizing the electron-beam lithography and dry-etching, the sub-wavelength Si nanorod arrays with broadband AR feature was successfully demonstrated. Not long ago, Boden et al. [7

7. S.-A. Boden and D.-M. Bagnall, “Tunable reflection minima of nanostructured antireflective surfaces,” Appl. Phys. Lett. 93(13), 133108 (2008). [CrossRef]

] has also applied the state-of-the-art e-beam lithography for obtaining a broadband AR silicon surface with sub-wavelength-scale nanopillar array based on the moth-eye principle. Most investigations focused on establishing the sub-wavelength structure on various substrates by using the same specific technique with strict parameters and complex processing steps in order to obtain optimal optical properties [7

7. S.-A. Boden and D.-M. Bagnall, “Tunable reflection minima of nanostructured antireflective surfaces,” Appl. Phys. Lett. 93(13), 133108 (2008). [CrossRef]

,8

8. C.-J. Ting, M.-C. Huang, H.-Y. Tsai, C.-P. Chou, and C.-C. Fu, “Low cost fabrication of the large-area anti-reflection films from polymer by nanoimprint/hot-embossing technology,” Nanotechnology 19(20), 205301 (2008). [CrossRef] [PubMed]

]. For mass-productive application, these procedures are impractical for broad-area fabrication due to an extremely low fabricating speed in large-scale pattering.

2. Experimental setup

In experiment, the duty-cycle controlled nonlinear surface reflectance minimum was investigated by taking Si nanorod array as an example. First of all, the standard RCA cleaning process (developed formerly by the company of Radio Corporation of America, RCA) is employed to clean the native oxide of a p-type (111)-oriented Si substrate. The Si substrate with an area of 6.25 cm2 was initially immersed in H2SO4 aqueous solution at 67 wt.% and then in buffered oxide etchant (BOE) to decompose the organic compounds and to remove the residual oxide layer, respectively. After pre-treatment, a new SiO2 buffer with film thickness of 45 ± 2 nm covered Si substrate was prepared by immersing the Si substrate in a mixed H2O2/NH4OH solution with equivalent weight percentage ratio at 27.5°C following with a rinse in copious deionized water. This process is employed to transfer the Si substrate turns from hydrophobicity to hydrophilicity by coating a 45-nm thick SiO2 layer, since the self-assembly of monolayer polystyrene nanosphere array usually require a hydrophilic substrate. In order to fabricate the regular nanorod arrays, the polystyrene nanospheres (manufactured by Sigma-Aldrich Co.) with a mean diameter of 500 nm in aqueous suspension with a solid concentration of 2.5 wt% were used to spin-coat the Si substrate as an etching mask for Si nanorod formation. Since the regularity of the monolayer polystyrene nanosphere array based etching mask is essential to affect the periodicity of Si nanorod, the self-alignment process were performed on SiO2 covered Si substrate with area density of 4 × 108 rod/cm−2 by decreasing the spin-coating rate to 1250 rpm. Note that the centrifugal force is required to be larger than the adhesion force to enhance the array regularity during self-alignment. Similar works have been demonstrated previously [12

12. W. Liu, W. Zhong, L. J. Qiu, L. Y. Lu, and Y. W. Du, “Fabrication and magnetic behaviour of 2D ordered Fe/SiO2 nanodots array,” Eur. Phys. J. B 51(4), 501–506 (2006). [CrossRef]

14

14. C. M. Hsu, S. T. Connor, M. X. Tang, and Y. Cui, “Wafer-scale silicon nanopillars and nanocones by Langmuir–Blodgett assembly and etching,” Appl. Phys. Lett. 93(13), 133109 (2008). [CrossRef]

]. It was found that monolayer polystyrene nanosphere array prepared with spin-coating method can hardly be obtained without high-speed rotation over 3500 rpm for 60 sec [12

12. W. Liu, W. Zhong, L. J. Qiu, L. Y. Lu, and Y. W. Du, “Fabrication and magnetic behaviour of 2D ordered Fe/SiO2 nanodots array,” Eur. Phys. J. B 51(4), 501–506 (2006). [CrossRef]

]. Such a strict parameter and time-consuming step results from strong aggregation between nanospheres. This problem has been solved in our case by improving dispersion of polystyrene nanospheres aqueous suspension to reach a relatively low spin rate. Jiang et al. also demonstrated a simple spin-coating technique for rapidly fabricating polymeric nanocomposite with wafer-scale process (4-inch wafer scale) [13

13. P. Jiang and M. J. McFarland, “Large-scale fabrication of wafer-size colloidal crystals, macroporous polymers and nanocomposites by spin-coating,” J. Am. Chem. Soc. 126(42), 13778–13786 (2004). [CrossRef] [PubMed]

]. The maximum achievable uniform scale for such kind of mask is greater than present work; however, the proposed recipe is unusual and difficult for reproduction. After dispersion the polystyrene nanospheres via a nonionic detergent in our case, the monolayer colloidal nanosphere alignment procedure is easily achieved at extremely low spin rate. Although the maximum achievable uniform size (6.25 cm2) of the mask reported in this work is slightly smaller than that reported in literature (4-inch wafer scale) [14

14. C. M. Hsu, S. T. Connor, M. X. Tang, and Y. Cui, “Wafer-scale silicon nanopillars and nanocones by Langmuir–Blodgett assembly and etching,” Appl. Phys. Lett. 93(13), 133109 (2008). [CrossRef]

], the tightly assembled polystyrene nanosphere array is formatted at 1250 rpm for 17 sec with an area density of 4 × 108 rod/cm−2. The schematics of the preferential etching procedure for the polystyrene nanosphere array masked SiO2/Si substrate are shown in Fig. 1
Fig. 1 Schematic illustration of SiO2 covered Si nanorod array fabrication.
.

3. Results and Discussion

3.1 Duty-cycle and composition analyses of tunable nanorods

Figure 2
Fig. 2 The size of nanosphere and distance between the nanorods as a function of etching time.
shows the size and distance of nanosphere array as a function of etching time. The original size of the polystyrene spheres prior to the pure O2- plasma etching is 500 nm. The SEM images clearly reveals that each Si nanorod array sample dry-etched under different recipe exhibits uniform size and spacing.

To further investigate the invasive effect during the CF4/O2 plasma etching process, the sample was in situ cut by using a dual-beam focused-ion-beam system (FEI DualBeam-1255) for TEM-XEDS diagnosis. The cross-sectional TEM image presents the a bi-layer structure for a single cylindrical-like SiO2/Si nanorod with a reducing side-wall slope due to the slightly anisotropic plasma etching process, as shown in Fig. 3(d). The top and bottom layers clearly reveal the image of amorphous SiO2 and Si with significant contrast, where the TEM-XEDS scanning mapping also provides the deviated depth profiles of O and Si composition, as shown in Fig. 3(e). As evidence, the O/Si ratio of XEDS data at nanorod surface region approaches nearly 2 to corroborate the SiO2 as a principal component in the top-amorphous layer, whereas the O content greatly attenuates to reflect the existence of pure Si nanorod structure at a depth beyond 50 nm. In addition, some fluorine atoms with composition ratio of 7% are incorporated into our SiO2 covered Si nanorod array samples. These results elucidate that utilizing the CF4/O2 plasma for dry-etching the thin-SiO2 covered Si substrate could form a fluorinated SiO2 structure.

3.2 Duty-cycle dependent reflectance and Brewster angle of SiO2/Si nanorod array

3.3 Nonlinear trend of surface reflectance versus duty-cycle of SiO2/Si nanorod array

To elucidate the deviation on duty-cycles-dependent reflectance of nanorod array with varying diameter, we employ an effective refractive index for the nanorod/substrate mixed surface structure. The effective refractive index of nanorod/substrate mixed periodical structure with diameter/spacing of A/B is assumed as ((n2 rod) × (A/period)2 + (n2 substrate) × (B/period)2)0.5 at low incident angles, and the shrinkage on duty-cycle oppositely increases the nanorod spacing under constant period (or lattice constant), the effective refractive index for the Si nanorod array is described as
neff=[(nrod2)(π4S2P2)2+(nsubstrate2)(1π4S2P2)2],
(1)
where S denotes the nano diameter and P the array period (rod-to-rod distance). That is, our experiments start with tuning nanorod diameter at same lattice constant, since the polystyrene nanosphere with same diameter is used for all samples. Otherwise, the variation of nanosphere size as well as the lattice constant concurrently changes the area density of the nanorods, which inevitably results in two geometrical parameters at same time. In our case, the refractive index of the SiO2 covered Si nanorod substrate mixed structure at Brewster angle incidence is estimated through the relation of tan−1 n = θ Brewster angle at 532 nm, which is found to reduce from 2.35 to 1.32 by increasing the duty-cycle of the SiO2/Si nanorod from 57% to 85%, as shown in Fig. 5
Fig. 5 Experimental and simulated refractive indices of nanorod arrays as a function of duty-cycle.
(square dotted). The nonlinear trend of the Si nanorod surface reflectance with enlarging duty-cycle leads to a minimum at nanorod duty-cycle of 85%. The simulation curve using Eq. (1) for duty-cycle ranging from 57% to 85% shown in Fig. 6
Fig. 6 Simulation results of nanorod array with (a) different mixed structure and (b) different duty-cycle in linear scale by Rsoft Diffraction Mode.
with nsubstrate/nrod = 3.56 at 532 nm also indicates a good agreement with the experimental data. The simulation clarifies that the gradually decreasing refractive index formed via increasing duty-cycle is not attributed to a material response but to an effective refractive index of the SiO2/Si nanorod/substrate mixed morphology. Subsequently, we wish to obtain the simulated broadband reflectance spectra of the SiO2 covered Si nanorod array. Instead of using effective refractive method, we simulate the reflectance spectrum with a full-field RCWA (using the diffraction mode calculation package from R-Soft software). The effective refractive index was not taken into the RCWA simulation.

During simulation, we also employ another set of fitting parameters by varying the nanorod spacing with constant nanorod diameter, which inevitably enlarge the period (or lattice constant) and dilute the area density of the nanorod array. Nevertheless, the simulated reflectance spectra of the nanorod array with varying duty-cycle and constant nanorod diameter also exhibits very similar trend on reflectance spectra and reveals a nonlinear relationship between its surface reflectance and duty-cycle. As shown in Fig. 7
Fig. 7 Experimental and simulated reflectance of nanorod arrays as a function of duty-cycle of 60% (left) and 89% (right).
, it is found that the curve of nanorod with duty cycle of 89% is well coincident with the simulated results. However, a significant deviation between the simulated and experimental spectra at short wavelength region for the nanorod sample with low duty-cycle is observed, which is mainly attributed to the anomalous dispersion contributed by the Si substrate. This originates from the lack of current simulation program, in which the dispersive substrate effect cannot be taken into consideration. Nonetheless, this work aim to emphasize the observation on the optimization of nanosphere duty-cycle for minimizing the nanorod surface reflectance. It is also found that the TM-mode surface reflectance increases when the periodic nanorod array structure disappears at higher duty-cycle >85% or approaches a purely SiO2/Si thin film. Without the periodical array, only the interference of reflections from the top and bottom of the SiO2 layer causes the maxima and minima [7

7. S.-A. Boden and D.-M. Bagnall, “Tunable reflection minima of nanostructured antireflective surfaces,” Appl. Phys. Lett. 93(13), 133108 (2008). [CrossRef]

]. In contrast, the surface reflectance of nanorod array also shows an increasing trend with decreasing duty-cycle (from 80% to 10%), indicating the diminishing influence of the nanorod array structure at smaller duty-cycles.

It is important to note that such a surface reflectance minimum is even lower than that of a uniformly SiO2 nanorods on account of its periodical nanorod array architecture. This result interprets that the nanorod surface reflectance eventually approach that of a SiO2 coated Si substrate at relatively high duty-cycles, whereas the reflectance of the low duty-cycle nanorod array is dominant by Si substrate.

4. Conclusion

Acknowledgment

This work was supported by the National Science Council of the Republic of China, Taiwan, R.O.C., under grants NSC98-2218-E-002-022 and NSC98-2623-E-002-002-ET.

References and links

1.

G.-R. Lin, Y. H. Pai, and C. T. Lin, “Microwatt MOSLED using SiOx with buried Si nanocrystals on Si nano-pillar array,” J. Lightwave Technol. 26(11), 1486–1491 (2008). [CrossRef]

2.

F.-G. Tarntair, L.-C. Chen, S.-L. Wei, W.-K. Hong, K.-H. Chen, and H.-C. Cheng, “High current density field emission from arrays of carbon nanotubes and diamond-clad Si tips,” J. Vac. Sci. Technol. 18(3), 1207–1211 (2000). [CrossRef]

3.

C. Lin and M. L. Povinelli, “Optical absorption enhancement in silicon nanowire arrays with a large lattice constant for photovoltaic applications,” Opt. Express 17(22), 19371–19381 (2009). [CrossRef] [PubMed]

4.

J. Xiang, W. Lu, Y.-J. Hu, Y. Wu, H. Yan, and C.-M. Lieber, “Ge/Si nanowire heterostructures as high-performance field-effect transistors,” Nature 441(7092), 489–493 (2006). [CrossRef] [PubMed]

5.

Y. Kanamori, M. Sasaki, and K. Hane, “Broadband antireflection gratings fabricated upon silicon substrates,” Opt. Lett. 24(20), 1422–1424 (1999). [CrossRef]

6.

Y. Kanamori, M. Ishimori, and K. Hane, “High efficient light-emitting diodes with antireflection subwavelength gratings,” IEEE Photon. Technol. Lett. 14(8), 1064–1066 (2002). [CrossRef]

7.

S.-A. Boden and D.-M. Bagnall, “Tunable reflection minima of nanostructured antireflective surfaces,” Appl. Phys. Lett. 93(13), 133108 (2008). [CrossRef]

8.

C.-J. Ting, M.-C. Huang, H.-Y. Tsai, C.-P. Chou, and C.-C. Fu, “Low cost fabrication of the large-area anti-reflection films from polymer by nanoimprint/hot-embossing technology,” Nanotechnology 19(20), 205301 (2008). [CrossRef] [PubMed]

9.

N. J. Trujillo, S. Baxamusa, and K. K. Gleason, “Grafted polymeric nanostructures patterned bottom-up by colloidal lithography and initiated chemical vapor deposition (iCVD),” Thin Solid Films 517(12), 3615–3618 (2009). [CrossRef]

10.

H. L. Chen, S. Y. Chuang, C. H. Lin, and Y. H. Lin, “Using colloidal lithography to fabricate and optimize sub-wavelength pyramidal and honeycomb structures in solar cells,” Opt. Express 15(22), 14793–14803 (2007). [CrossRef] [PubMed]

11.

P. Bettotti, M. Cazzanelli, L. Dal Negro, B. Danese, Z. Gaburro, C. J. Oton, G. V. Prakash, and L. Pavesi, “Silicon nanostructures for photonics,” J. Phys. Condens. Matter 14(35), 8253–8281 (2002). [CrossRef]

12.

W. Liu, W. Zhong, L. J. Qiu, L. Y. Lu, and Y. W. Du, “Fabrication and magnetic behaviour of 2D ordered Fe/SiO2 nanodots array,” Eur. Phys. J. B 51(4), 501–506 (2006). [CrossRef]

13.

P. Jiang and M. J. McFarland, “Large-scale fabrication of wafer-size colloidal crystals, macroporous polymers and nanocomposites by spin-coating,” J. Am. Chem. Soc. 126(42), 13778–13786 (2004). [CrossRef] [PubMed]

14.

C. M. Hsu, S. T. Connor, M. X. Tang, and Y. Cui, “Wafer-scale silicon nanopillars and nanocones by Langmuir–Blodgett assembly and etching,” Appl. Phys. Lett. 93(13), 133109 (2008). [CrossRef]

15.

M. Elwenspoek, and H. Jansen, “Silicon Micromachining”, Cambridge University Press: Cambridge, U.K. (1998).

16.

L. Yan, K. Wang, J. Wu, and L. Ye, “Hydrophobicity of model surfaces with loosely packed polystyrene spheres after plasma etching,” J. Phys. Chem. B 110(23), 11241–11246 (2006). [CrossRef] [PubMed]

17.

B. J.-Y. Tan, C.-H. Sow, K.-Y. Lim, F.-C. Cheong, G.-L. Chong, A. T.-S. Wee, and C.-K. Ong, “Fabrication of a two-dimensional periodic non-close-packed array of polystyrene particles,” J. Phys. Chem. B 108(48), 18575–18579 (2004). [CrossRef]

18.

A. Ruiz, A. Valsesia, G. Ceccone, D. Gilliland, P. Colpo, and F. Rossi, “Fabrication and characterization of plasma processed surfaces with tuned wettability,” Langmuir 23(26), 12984–12989 (2007). [CrossRef] [PubMed]

19.

K. Tsougeni, N. Vourdas, A. Tserepi, E. Gogolides, and C. Cardinaud, “Mechanisms of oxygen plasma nanotexturing of organic polymer surfaces: from stable super hydrophilic to super hydrophobic surfaces,” Langmuir 25(19), 11748–11759 (2009). [CrossRef] [PubMed]

20.

J.-Q. Xi, M. F. Schubert, J. K. Kim, E. F. Schubert, M. F. Chen, S. Y. Lin, W. Liu, and J. A. Smart, “Optical thin-film materials with low refractive index for broadband elimination of Fresnel reflection,” Nat. Photonics 1, 176–179 (2007).

21.

T. Homma, A. Satoh, S. Okada, M. Itoh, M. Yamaguchi, and H. Takahashi, “Optical properties of fluorinated silicon oxide films by liquid phase deposition for optical waveguides,” IEEE Trans. Instrum. Meas. 47(3), 698–702 (1998). [CrossRef]

22.

G.-R. Lin, F. S. Meng, Y. H. Pai, Y. C. Chang, and S. H. Hsu, “Manipulative depolarization and reflectance spectra of morphologically controlled nano-pillars and nano-rods,” Opt. Express 17(23), 20824–20832 (2009). [CrossRef] [PubMed]

OCIS Codes
(120.5700) Instrumentation, measurement, and metrology : Reflection
(310.1210) Thin films : Antireflection coatings
(220.4241) Optical design and fabrication : Nanostructure fabrication
(310.6628) Thin films : Subwavelength structures, nanostructures

ToC Category:
Thin Films

History
Original Manuscript: June 1, 2010
Revised Manuscript: July 10, 2010
Manuscript Accepted: August 3, 2010
Published: January 14, 2011

Citation
Yi-Hao Pai, Yu-Chan Lin, Jai-Lin Tsai, and Gong-Ru Lin, "Nonlinear dependence between the surface reflectance and the duty-cycle of semiconductor nanorod array," Opt. Express 19, 1680-1690 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-3-1680


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References

  1. G.-R. Lin, Y. H. Pai, and C. T. Lin, “Microwatt MOSLED using SiOx with buried Si nanocrystals on Si nano-pillar array,” J. Lightwave Technol. 26(11), 1486–1491 (2008). [CrossRef]
  2. F.-G. Tarntair, L.-C. Chen, S.-L. Wei, W.-K. Hong, K.-H. Chen, and H.-C. Cheng, “High current density field emission from arrays of carbon nanotubes and diamond-clad Si tips,” J. Vac. Sci. Technol. 18(3), 1207–1211 (2000). [CrossRef]
  3. C. Lin and M. L. Povinelli, “Optical absorption enhancement in silicon nanowire arrays with a large lattice constant for photovoltaic applications,” Opt. Express 17(22), 19371–19381 (2009). [CrossRef] [PubMed]
  4. J. Xiang, W. Lu, Y.-J. Hu, Y. Wu, H. Yan, and C.-M. Lieber, “Ge/Si nanowire heterostructures as high-performance field-effect transistors,” Nature 441(7092), 489–493 (2006). [CrossRef] [PubMed]
  5. Y. Kanamori, M. Sasaki, and K. Hane, “Broadband antireflection gratings fabricated upon silicon substrates,” Opt. Lett. 24(20), 1422–1424 (1999). [CrossRef]
  6. Y. Kanamori, M. Ishimori, and K. Hane, “High efficient light-emitting diodes with antireflection subwavelength gratings,” IEEE Photon. Technol. Lett. 14(8), 1064–1066 (2002). [CrossRef]
  7. S.-A. Boden and D.-M. Bagnall, “Tunable reflection minima of nanostructured antireflective surfaces,” Appl. Phys. Lett. 93(13), 133108 (2008). [CrossRef]
  8. C.-J. Ting, M.-C. Huang, H.-Y. Tsai, C.-P. Chou, and C.-C. Fu, “Low cost fabrication of the large-area anti-reflection films from polymer by nanoimprint/hot-embossing technology,” Nanotechnology 19(20), 205301 (2008). [CrossRef] [PubMed]
  9. N. J. Trujillo, S. Baxamusa, and K. K. Gleason, “Grafted polymeric nanostructures patterned bottom-up by colloidal lithography and initiated chemical vapor deposition (iCVD),” Thin Solid Films 517(12), 3615–3618 (2009). [CrossRef]
  10. H. L. Chen, S. Y. Chuang, C. H. Lin, and Y. H. Lin, “Using colloidal lithography to fabricate and optimize sub-wavelength pyramidal and honeycomb structures in solar cells,” Opt. Express 15(22), 14793–14803 (2007). [CrossRef] [PubMed]
  11. P. Bettotti, M. Cazzanelli, L. Dal Negro, B. Danese, Z. Gaburro, C. J. Oton, G. V. Prakash, and L. Pavesi, “Silicon nanostructures for photonics,” J. Phys. Condens. Matter 14(35), 8253–8281 (2002). [CrossRef]
  12. W. Liu, W. Zhong, L. J. Qiu, L. Y. Lu, and Y. W. Du, “Fabrication and magnetic behaviour of 2D ordered Fe/SiO2 nanodots array,” Eur. Phys. J. B 51(4), 501–506 (2006). [CrossRef]
  13. P. Jiang and M. J. McFarland, “Large-scale fabrication of wafer-size colloidal crystals, macroporous polymers and nanocomposites by spin-coating,” J. Am. Chem. Soc. 126(42), 13778–13786 (2004). [CrossRef] [PubMed]
  14. C. M. Hsu, S. T. Connor, M. X. Tang, and Y. Cui, “Wafer-scale silicon nanopillars and nanocones by Langmuir–Blodgett assembly and etching,” Appl. Phys. Lett. 93(13), 133109 (2008). [CrossRef]
  15. M. Elwenspoek, and H. Jansen, “Silicon Micromachining”, Cambridge University Press: Cambridge, U.K. (1998).
  16. L. Yan, K. Wang, J. Wu, and L. Ye, “Hydrophobicity of model surfaces with loosely packed polystyrene spheres after plasma etching,” J. Phys. Chem. B 110(23), 11241–11246 (2006). [CrossRef] [PubMed]
  17. B. J.-Y. Tan, C.-H. Sow, K.-Y. Lim, F.-C. Cheong, G.-L. Chong, A. T.-S. Wee, and C.-K. Ong, “Fabrication of a two-dimensional periodic non-close-packed array of polystyrene particles,” J. Phys. Chem. B 108(48), 18575–18579 (2004). [CrossRef]
  18. A. Ruiz, A. Valsesia, G. Ceccone, D. Gilliland, P. Colpo, and F. Rossi, “Fabrication and characterization of plasma processed surfaces with tuned wettability,” Langmuir 23(26), 12984–12989 (2007). [CrossRef] [PubMed]
  19. K. Tsougeni, N. Vourdas, A. Tserepi, E. Gogolides, and C. Cardinaud, “Mechanisms of oxygen plasma nanotexturing of organic polymer surfaces: from stable super hydrophilic to super hydrophobic surfaces,” Langmuir 25(19), 11748–11759 (2009). [CrossRef] [PubMed]
  20. J.-Q. Xi, M. F. Schubert, J. K. Kim, E. F. Schubert, M. F. Chen, S. Y. Lin, W. Liu, and J. A. Smart, “Optical thin-film materials with low refractive index for broadband elimination of Fresnel reflection,” Nat. Photonics 1, 176–179 (2007).
  21. T. Homma, A. Satoh, S. Okada, M. Itoh, M. Yamaguchi, and H. Takahashi, “Optical properties of fluorinated silicon oxide films by liquid phase deposition for optical waveguides,” IEEE Trans. Instrum. Meas. 47(3), 698–702 (1998). [CrossRef]
  22. G.-R. Lin, F. S. Meng, Y. H. Pai, Y. C. Chang, and S. H. Hsu, “Manipulative depolarization and reflectance spectra of morphologically controlled nano-pillars and nano-rods,” Opt. Express 17(23), 20824–20832 (2009). [CrossRef] [PubMed]

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