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A close to unity and all-solar-spectrum absorption by ion-sputtering induced Si nanocone arrays

Ying Qiu

Abstract:

Si nanocone arrays are formed on Si(100) by Ar⁺ ion sputtering combined with metal ion co-deposition. In this work, we report to tune the cone size and composition of Si nanocone arrays by adjusting ion-sputtering parameters. It is found that the aspect ratio and height of the nanocone, the surface composition, as well as the reflectance, transmittance and absorbance of the textured Si (or TS) can be well tuned by merely changing the sample temperature and ion dose.

The aspect ratio of Si cone is found to increase steadily with increasing sample temperature, but decreases slowly with increasing ion dose. Furthermore, the height and base diameter of Si cone increase monotonously with increasing dose at a constant temperature. The absorptivity increases in general with increasing aspect ratio and height. With this flexible tuning approach, a close to unity and all-solar-spectrum absorption is achieved, with the maximal absorbance for l = 350 to 1100 nm being higher than 96%, and that for l = 1100 to 2000 nm higher than 92%. Combining the results, it is suggested that the ion-sputtering induced TS can be a promising material for Si solar cell and sensitive and broadband photo-detector.

References：

1.   T. H. Her, R. J. Finlay, C. Wu, S. Deliwala, and E. Mazur, “Microstructuring of silicon with femtosecond laser pulses,” Appl. Phys. Lett. 73(12), 1673-1675(1998).

2.   C. Wu, C. H. Crouch, L. Zhao, J. E. Carey, R. Younkin, J. A. Levinson, E. Mazur, R. M. Farrell, P. Gothoskar, and A. Karger, “Near-unity below-band-gap absorption by microstructured silicon,” Appl. Phys. Lett. 78(13), 1850-1852(2001).

3.   T. G. Kim, J. M. Warrender, and M. J. Aziz, “Strong sub-band-gap infrared absorption in silicon supersaturated with sulfur,” Appl. Phys. Lett. 88(24), 241902(2006).

4.   K. Peng, X. Wang, and S. T. Lee, “Silicon nanowire array photoelectrochemical solar cells,” Appl. Phys. Lett. 92(16), 163103(2008).

5.   M. Tabbal, T. Kim, D. N. Woolf, B. Shin, and M. J. Aziz, “Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing,” Appl. Phys. A. 98(3), 589-594(2010).

6.   F. J. Tsai, J. Y. Wang, J. J. Huang, Y. W. Kiang, and C. C. Yang, “Absorption enhancement of an amorphous Si solar cell through surface plasmon-induced scattering with metal nanoparticles,” Opt. Express 18(13), 207-220(2010).

7.  Y. Liu, S. H. Sun, J. Xu, L. Zhao, H. C. Sun, J. Li, W. W. Mu, L. Xu, and K. J. Chen, “Broadband antireflection and absorption enhancement by forming nano-patterned Si structures for solar cells,” Opt. Express 19(19), 1051-1056(2011).

8.  E. Garnett and P. Yang, “Light Trapping in Silicon Nanowire Solar Cells,” Nano Lett. 10(3), 1082-1087(2010).

9.  J. Zhu, Z. Yu, G. F. Burkhard, C. M. Hsu, S. T. Connor, Y. Xu, Q. Wang, M. McGehee, S. Fan, and Y. Cui, “Optical Absorption Enhancement in Amorphous Silicon Nanowire and Nanocone Arrays,” Nano Lett. 9(1), 279-282(2009).

10.  L. Hu and G. Chen, “Analysis of Optical Absorption in Silicon Nanowire Arrays for Photovoltaic Applications,” Nano Lett. 7(11), 3249-3252(2007).

11.  O. L. Muskens, J. G. Rivas, R. E. Algra, E. P. A. M. Bakkers, and A. Lagendijk, “Design of Light Scattering in Nanowire Materials for Photovoltaic Applications,” Nano Lett. 8(9), 2638-2642(2008).

12.  J. Zhou, M. Hildebrandt, and M. Lu, “Self-organized antireflecting nano-cone arrays on Si (100) induced by ion bombardment,” J. Appl. Phys. 109, 053513(2011).

13.  P. Spinelli, M. A. Verschuuren, and A. Polman, “Broadband omnidirectional antireflection coating based on subwavelength surface Mie resonators,” Nat Commun. 3, 692(2012).

14.  H. S. Seo , X. P. Li , H. D. Um , B. Y. Yoo , J. H. Kim , K. P. Kim ,Y. W. Cho , and J. H. Lee, “Fabrication of precisely controlled silicon wire and cone arrays by electrochemical etching,” Materials Letters 63(29), 2567–2569(2009).

15.  L. W. Yu, K. J. Chen, J. Song, J. Xu, W. Li, H. M. Li, M. Wang, X. F. Li, and X. F. Huang, “Self-Assembled Si Quantum-Ring Structures on a Si Substrate by Plasma-Enhanced Chemical Vapor Deposition Based on a Growth-Etching Competition Mechanism,” Adv. Mater. 19(12), 1577–1581(2007).

16.  N. G. Shang, X. L. Ma, C. P. Liu, I. Bello, and S. T. Lee, “Arrays of Si cones prepared by ion beams: growth mechanisms,” Phys. Status Solidi A 207(2), 309-315(2010).

17.  J. Erlebacher, M. J. Aziz, E. Chason, M. B. Sinclair, and J. A. Floro, “Spontaneous Pattern Formation on Ion Bombarded Si(001),” Phys. Rev. Lett. 82(11), 2330-2333(1999).

18.  G. Ozaydin, A. S. Ozcan, Y. Y. Wang, K. F. Ludwig, H. Zhou, R. L. Headrick, and D. P. Siddons, “Real-time x-ray studies of Mo-seeded Si nanodot formation during ion bombardment,” Appl. Phys. Lett. 87(16), 163104(2005).

19.  B. Ziberi, M. Cornejo, F. Frost, and B. Rauschenbach, “Highly ordered nanopatterns on Ge and Si surfaces by ion beam sputtering,” J. Phys.:Condens. Matter 21(22), 224003(2009).

20.  J. Zhou, S. Facsko, M. Lu, and W. Möller, “Nanopatterning of Si surfaces by normal incident ion erosion: influence of metal incorporation on surface morphology evolution,” J. Appl. Phys. 109, 104315(2011).

21.  J. Zhou and M. Lu, “Mechanism of Fe impurity motivated ion-nanopatterning of Si (100) surfaces,” Phys. Rev. B 82(12), 125404(2010).

22.  J. A. Sanchez-Garcia, L. Vazquez, R. Gago, A. Redondo-Cubero, J. M. Albella, and Z. S. Czigany, “Tuning the surface morphology in self-organized ion beam nanopatterning of Si(001) via metal incorporation: from holes to dots,”  Nanotechnology 19(35), 355306(2008).

23.  S. Macko, F. Frost, B. Ziberi, D. F. Foerster, and T. Michely, “Is keV ion-induced pattern formation on Si(001) caused by metal impurities?” Nanotechnology 21(8), 085301(2010).

24.  J. S. Lai, L. Chen, X. N. Fu, J. Sun, Z. F. Ying, J. D. Wu, and N. Xu, “Effects of the experimental conditions on the growth of crystalline ZnSe nano-needles by pulsed laser deposition,” Appl Phys A 102(2), 477–483(2011).

25.  R. M. Bradley and J. M. E. Harper, “Theory of ripple topography induced by ion bombardment,” J. Vac. Sci. Technol.A 6(4), 2390-2395(1988).

26.  M. C. Bost and J. E. Mahan, “Optical properties of semiconducting iron disilicide thin films,” J. Appl. Phys. 58(7), 2696-2703(1985).

27.  M. Oživold, V. Boháč, V. Gašparík, G. Leggieri, Š. Luby, A. Luches, E. Majková, and P. Mrafko, “The optical band gap of semiconducting iron disilicide thin films,” Thin Solid Films 263(1), 92-98(1995).

28.  H. Lange, W. Henrion, F. Fenske, T. Zettler, J. Schumann, and S. Teichert, “Optical Interband Properties of Some Semiconducting Silicides,” Phys. Status Solidi B 194(1), 231-240(1996).

29.  V. Bellani, G. Guizzetti, F. Marabelli, A. Piaggi, A. Borghesi, F. Nava, V. N. Antonov, N. Antonov, O. Jepsen, O. K. Andersen, and V. V. Nemoshkalenko, “Theory and experiment on the optical properties of CrSi_2,”  Phys. Rev. B 46(15), 9380-9389(1992).

PL Study of ZnO Films

Kun. Chen, Jing. Li, Songyou, Wang.

Department of optical science and engineering, Fudan University

Abstract:

Zinc Oxide (ZnO) is an important II-VI group compound semiconductor which has caught a lot of interests. Besides its applications in short wavelength light emitting and detecting devices it also has an adequate potential in applications of visible region. Photoluminescence (PL) is an efficient method which has been used a lot of times for studying the characteristics of ZnO. The photoluminescence (PL) spectrum of ZnO consists of a well-known near-band-edge (NBE) emission and a deep level (DL) emission in the visible region. Defects sufficiently influence the electrical and optical properties of ZnO. However, the origin and mechanism of the DL emission still remain controversial. ZnO films are sputtered onto silicon and quartz glass substrates via magnetron sputtering using an ultrapure ZnO target in a flow of Argon gas followed by post-annealing in N₂ and in air under different temperature for different time. X-ray diffraction (XRD) and atomic force microscopy (AFM) are applied to characterize the crystalline structure and morphology of prepared films. Photoluminescence spectrum is also studied to obtain the optical properties of ZnO films. Multiple emission bands involving the UV and DL band containing blue, green, orange and red emission was observed. The blue emission is due to the oxygen vacancies ( V_O ) in the films. Interstitial Zn (Zn_i) and antisite Zn_O may contribute to green and red PL spectrum.

References:

¹     Chris G. Van de Walle,  Physica B 308-310, 899 (2001).

²     A. F. Kohan, G. Ceder, D. Morgan, and C. G. Van de Walle,  Physical Review B 61 (22), 15019 (2000).

³     T. V. Butkhuzi and T.G. Chelidze,  Physical Review B 58 (10), 692 (1998).

⁴     A. Teke, Ü Özgür, S. Doğan, X. Gu, H. Morkoç, B. Nemeth, J. Nause, and H. Everitt,  Physical Review B 70 (19) (2004).

⁵     Ü Özgür, Ya I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç,  Journal of Applied Physics 98 (4), 041301 (2005).

⁶     J. C. Moore, L. R. Covington, and R. Stansell,  Physica Status Solidi (a) 209 (4), 741 (2012).

⁷     Y. W. Heo, D. P. Norton, and S. J. Pearton,  Journal of Applied Physics 98 (7), 073502 (2005).

⁸     S. A. Studenikin, Nickolay Golego, and Michael Cocivera,  Journal of Applied Physics 84 (9), 5001 (1998).

⁹     S. A. Studenikin and Michael Cocivera,  Journal of Applied Physics 91 (8), 5060 (2002).

¹⁰    O. F. Schirmer and D. Zwingel,  Solid State Commun 18 (19), 1559 (1970).

¹¹    Bixia Lin, Zhuxi Fu, and Yunbo Jia,  Applied Physics Letters 79 (7), 943 (2001).

¹²    X. L. Wu, G. G. Siu, C. L. Fu, and H. C. Ong,  Applied Physics Letters 78 (16), 2285 (2001).

¹³    R. Vidya, P. Ravindran, H. Fjellvåg, B. Svensson, E. Monakhov, M. Ganchenkova, and R. Nieminen,  Physical Review B 83 (4) (2011).

¹⁴    Yu-Yun Peng, Tsung-Eong Hsieh, and Chia-Hung Hsu,  Applied Physics Letters 89 (21), 211909 (2006).

Study polarization properties in ferroelectric thin films by spectroscopic ellipsometry

Fan Zhang

Department of Optical Science and Engineering, Fudan University

Abstract

Ferroelectric (FE) thin films have attracted much attention due to their excellent ferroelectric, dielectric and electro-optic properties, and wide application in many fields, for instance, FE random access memory (FRAM), capacitor and electro-optic modulator. With the development of the modern techniques and the extensive application of function devices made up of FE thin films, size effects on polarization have aroused great interest due to the miniaturization and integration requirement of the microelectric industry. At present, phenomenological Landau thermodynamic theory and atomic-level first-principles calculations from the macroscopic and microcosmic views have deeply analyzed the size effects in FE thin films, and some researchers also have studied this topic in experiment by FE hysteresis loop. However, few literatures have been published on size effect in optical frequency range.

In this presentation, I will firstly give introduction of FE thin films including concept, materials and applications. Then the size effects in FE thin films will be discussed in detail from theory calculation and experimental views. At last, my recent research progress on PZT and BST FE thin films will be present.

References

1.  C. H. Ahn, K. M. Rabe, J. M. Triscone, Science 303, 488 (2004)

2.  B. Jiang, J. L. Peng, L. A. Bursill, W. L. Zhong, J. Appl. Phys. 87, 3462 (2000)

3.  W. L. Zhong, Y. G. Wang, P. L. Zhang, B. D. Qu, Phys. Rev. B 50, 698 (1994)

4.  I. Kornev, H. Fu, L. Bellaiche, Phys. Rev. Lett. 93, 196104 (2004)

5.  J. Junquera, P. Ghosez, Nature London 422, 506 (2003)

6.  N. A. Pertsev, H. Kohlstedt, Phys. Rev. Lett. 98, 257603 (2007)

7.  M. Sepliarsky, M. G. Stachiotti, R. L. Migoni, Phys. Rev. Lett. 96, 137603(2006)

8.  Y. S. Kim, D. H. Kim et al., Appl. Phys. Lett. 86, 102907 (2005)

9.  B. Wang, C. H. Woo, J. Appl. Phys. 97, 084109 (2005)

10.  Q. Y. Cai, Y. X. Zheng et al., J. Phys. D 43, 445302 (2010)

11.  D. X. Zhang, Y. X. Zheng et al., Appl. Phys. A 108, 975 (2012)

12.  Z. J. Xu, F. Zhang, R. J. Zhang et al., Appl. Phys. A (under review)