Chế tạo, nghiên cứu tính chất quang và định hướng ứng dụng trong tán xạ raman tăng cường bề mặt của các hệ dây nanô silic xếp thẳng hàng

- VIỆN HÀN LÂM KHOA HỌC VÀ CÔNG NGHỆ VIỆT NAM HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ Lương Trúc Quỳnh Ngân CHẾ TẠO, NGHIÊN CỨU TÍNH CHẤT QUANG VÀ ĐỊNH HƯỚNG ỨNG DỤNG TRONG TÁN XẠ RAMAN TĂNG CƯỜNG BỀ MẶT CỦA CÁC HỆ DÂY NANÔ SILIC XẾP THẲNG HÀNG LUẬN ÁN TIẾN SĨ KHOA HỌC VẬT LIỆU Hà Nội - 2016 - VIỆN HÀN LÂM KHOA HỌC VÀ CÔNG NGHỆ VIỆT NAM HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ Lương Trúc Quỳnh Ngân CHẾ TẠO, NGHIÊN CỨU TÍNH CHẤT QUANG VÀ ĐỊNH HƯỚNG ỨNG DỤNG TRONG TÁN XẠ RAMAN TĂNG CƯỜNG BỀ MẶT CỦA CÁC HỆ DÂY NANÔ SILIC XẾP THẲNG HÀNG Chuyên ngành: Vật liệu điện tử Mã số: 62 44 01 23 LUẬN ÁN TIẾN SĨ KHOA HỌC VẬT LIỆU NGƯỜI HƯỚNG DẪN KHOA HỌC: GS TS ĐÀO TRẦN CAO Hà Nội - 2016 i LỜI CAM ĐOAN Tôi xin cam đoan cơng trình nghiên cứu tơi thực hướng dẫn GS.TS Đào Trần Cao cộng tác đồng nghiệp Các kết nghiên cứu thực Viện khoa học Vật liệu - Viện Hàn lâm Khoa học Công nghệ Việt Nam Các số liệu kết luận án hoàn toàn trung thực chưa công bố luận án khác Tác giả luận án Lương Trúc Quỳnh Ngân ii LỜI CẢM ƠN Lời đầu tiên, em xin bày tỏ lòng biết ơn sâu sắc tới GS.TS Đào Trần Cao người thầy tận tình hướng dẫn, bảo em suốt trình học tập thực nội dung nghiên cứu luận án này, người cho em lời khuyên bổ ích, lời động viên lúc em gặp khó khăn truyền cho em lịng say mê khoa học Tơi xin chân thành cảm ơn cô, bạn đồng nghiệp thuộc Phòng Phát triển thiết bị Phương pháp phân tích - Viện Khoa học Vật liệu luôn động viên, giúp đỡ cho ý kiến quý báu công việc sống Tôi xin gửi lời cảm ơn tới TS Cao Tuấn Anh, giảng viên trường Đại học Tân Trào giúp đỡ nhiều việc thực đề tài Tôi xin gửi lời cảm ơn tới PGS.TS Lê Văn Vũ, Giám đốc trung tâm Khoa học Vật liệu, thuộc khoa Vật lý, trường Đại học Khoa học tự nhiên giúp đỡ thực số phép đo đạc, khảo sát mẫu Tôi xin chân thành cảm ơn Viện Khoa học Vật liệu, Viện Hàn lâm Khoa học Công nghệ Việt Nam tạo điều kiện, hỗ trợ tơi kinh phí thời gian để thực tốt đề tài nghiên cứu Cuối tơi xin trân trọng gửi lời cảm ơn tới gia đình bạn bè, người bên chia sẻ, giúp đỡ động viên tơi suốt q trình học tập thực luận án Tác giả luận án Lương Trúc Quỳnh Ngân iii MỤC LỤC LỜI CAM ĐOAN LỜI CẢM ƠN Trang i ii MỤC LỤC iii DANH MỤC CÁC CHỮ VIẾT TẮT viii DANH MỤC CÁC KÝ HIỆU ix DANH MỤC CÁC BẢNG BIỂU VÀ HÌNH VẼ x MỞ ĐẦU Chương Tổng quan vật liệu dây nanô silic 1.1 Sơ lược vật liệu silic khối 1.2 Các phương pháp chế tạo vật liệu dây nanô Si 1.2.1 Cách tiếp cận “từ lên” 1.2.1.1 Cơ chế – lòng – rắn 1.2.1.2 Mọc với hỗ trợ ơxít 1.2.1.3 Tổng hợp sở dung dịch 10 12 13 1.2.2 Cách tiếp cận “từ xuống” 1.2.2.1 Phương pháp ăn mịn hóa học có trợ giúp kim loại 13 14 1.2.2.2 Phương pháp ăn mòn điện hóa có trợ giúp kim loại 15 1.3 Các tính chất vật liệu dây nanơ Si 1.3.1 Tính chất điện 1.3.2 Huỳnh quang vật liệu dây nanơ Si 1.3.3 Tính chất nhiệt 1.4 Ứng dụng vật liệu dây nanô Si 1.4.1 Các pin ion Li 1.4.2 Pin mặt trời 1.4.3 Các ứng dụng sinh học 1.4.3.1 Xét nghiệm tế bào 1.4.3.2 Sự chuyển gen 1.4.3.3 Dẫn thuốc 16 16 18 21 22 22 22 23 23 24 25 iv 1.4.4 Các cảm biến 1.4.4.1 Tán xạ Raman tăng cường bề mặt 1.4.4.2 Điện hóa học 1.4.4.3 Tranzito hiệu ứng trường 25 26 27 27 1.5 Các phương pháp khảo sát cấu trúc, tính chất ứng dụng 28 hệ dây nanô Si 1.5.1.Các phương pháp khảo sát hình thái, thành phần cấu trúc 28 hệ SiNW 1.5.1.1 Khảo sát hình thái hệ SiNW kính hiển vi 28 điện tử qt 1.5.1.2 Khảo sát hình dáng kích thước SiNW kính hiển vi điện tử truyền qua 30 1.5.1.3 Phân tích thành phần nguyên tố phổ tán sắc 31 lượng tia X 1.5.2 Phương pháp ghi phổ huỳnh quang 1.5.3 Phương pháp Raman khảo sát ứng dụng vật liệu SiNW 1.6 Kết luận Chương Chương Nghiên cứu chế tạo hệ ASiNW phương pháp ăn mịn hóa học ăn mịn điện hóa có trợ giúp kim loại 2.1 Giới thiệu chung phương pháp ăn mòn 2.1.1 Phương pháp ăn mịn khơ 2.1.2 Phương pháp ăn mịn ướt 2.2 Nghiên cứu chế tạo hệ ASiNW phương pháp MACE 2.2.1 Cơ chế ăn mòn 2.2.1.1 Các phản ứng 32 33 35 36 36 36 37 40 41 41 2.2.1.2 Sự phun lỗ trống vai trò kim loại 43 2.2.1.3 Sự chuyển khối lượng 2.2.1.3 Sự chuyển khối lượng 45 46 2.2.2 Công nghệ ăn mòn MACE áp dụng để chế tạo hệ ASiNW đế Si luận án 2.2.2.1 Vật liệu ban đầu 2.2.2.2 Dung dịch lắng đọng kim loại dung dịch ăn mòn 47 47 47 v 2.2.2.3 Quy trình chế tạo hệ ASiNW đế Si phương pháp MACE 48 2.2.3 Chế tạo hệ ASiNW đế Si phương pháp MACE 49 2.2.4 Ảnh hưởng điều kiện chế tạo vật liệu ban đầu lên 50 cấu trúc hệ ASiNW đế Si chế tạo phương pháp MACE 2.2.4.1 Ảnh hưởng nồng độ AgNO3 dung dịch lắng 50 đọng Ag lên cấu trúc hệ ASiNW 2.2.4.2 Ảnh hưởng vật liệu ban đầu lên cấu trúc hệ ASiNW 2.2.4.3 Ảnh hưởng thời gian ăn mòn lên cấu trúc hệ ASiNW 2.2.4.4 Ảnh hưởng dung dịch ăn mòn lên cấu trúc hệ ASiNW 2.3 Nghiên cứu chế tạo hệ ASiNW phương pháp MAECE 2.3.1 Cơ chế ăn mòn 2.3.1.1 Sự phun lỗ trống ăn mòn anốt 2.3.1.2 Cơ chế ăn mòn trực tiếp ăn mịn gián tiếp 2.3.2 Cơng nghệ ăn mịn MAECE áp dụng để chế tạo hệ ASiNW đế Si luận án 2.3.2.1 Vật liệu ban đầu, dung dịch lắng đọng dung dịch ăn mòn 2.3.2.2 Hệ điện hóa sử dụng để chế tạo hệ ASiNW 2.2.2.3 Quy trình chế tạo hệ ASiNW đế Si phương pháp MACE 2.3.3 Chế tạo hệ ASiNW đế Si phương pháp MAECE 2.3.4 Ảnh hưởng điều kiện chế tạo lên cấu trúc hệ ASiNW 2.3.4.1 Ảnh hưởng nồng độ AgNO3 dung dịch lắng đọng Ag 2.3.4.2 Ảnh hưởng mật độ dịng điện hóa 2.3.4.3 Ảnh hưởng thời gian ăn mòn 2.4 Kết luận Chương 57 59 61 65 65 65 66 70 70 70 71 72 73 73 76 78 80 vi Chương Nghiên cứu tính chất huỳnh quang hệ ASiNW 3.1 Lý thuyết chung phát quang vật liệu silic cấu trúc nanô 3.1.1 Hiệu ứng giam giữ lượng tử 81 81 82 3.1.2 Hiệu ứng giam giữ lượng tử thụ động hóa bề mặt 3.1.3 Hiệu ứng giam giữ lượng tử trạng thái bề mặt 87 89 3.1.4 Hiệu ứng giam giữ lượng tử sai hỏng SiO2 93 96 3.2 Áp dụng lý thuyết chung phát quang vật liệu Si cấu trúc nanơ để giải thích kết thu PL hệ ASiNW 3.2.1 Thí nghiệm 3.2.2 Các kết thảo luận PL mẫu ASiNW 3.3 Kết luận Chương Chương Ứng dụng hệ ASiNW tán xạ Raman tăng cường bề mặt 4.1 Tán xạ Raman 4.2 Tổng quan tán xạ Raman tăng cường bề mặt 4.2.1 Các chế tăng cường SERS 4.2.1.1 Cơ chế tăng cường điện từ 4.2.1.2 Cơ chế tăng cường hóa học 4.2.2 Các loại đế SERS 4.2.3 Hệ số tăng cường SERS 4.2.3.1 Hệ số tăng cường đơn phân tử 4.2.3.2 Hệ số tăng cường đế SERS 4.2.3.3 Hệ số tăng cường phân tích 4.2.3.4 Hệ số tăng cường ước tính dựa phép đo mặt cắt ngang 4.2.4 Các ứng dụng SERS 4.2.4.1 Ứng dụng cảm biến sinh học 4.2.4.2 Ứng dụng phân tích mơi trường 4.2.5 Ưu điểm nhược điểm SERS 4.3 Ứng dụng hệ ASiNW SERS 4.3.1 Quy trình chế tạo đế SERS từ hệ ASiNW đế Si 4.3.2 Sử dụng hệ ASiNW thẳng đứng có phủ AgNP (AgNPs/VASiNW) để phát phân tử MG nồng độ thấp 96 98 108 110 110 115 116 117 121 123 125 126 126 127 127 128 128 128 129 130 130 132 vii thông qua hiệu ứng SERS 4.3.3 Sử dụng hệ ASiNW xiên có phủ AgNP (AgNPs/OASiNW) để phát phân tử MG nồng độ thấp thông qua hiệu ứng SERS 4.3.4 Sử dụng hệ AgNPs/OASiNW để phát phân tử 140 144 thuốc diệt cỏ paraquat thông qua hiệu ứng SERS 4.4 Kết luận Chương 146 Kết luận DANH MỤC CÁC CƠNG TRÌNH CƠNG BỐ CỦA LUẬN ÁN TÀI LIỆU THAM KHẢO 147 149 151 viii DANH MỤC CÁC CHỮ VIẾT TẮT AgNP - hạt nanô bạc AgNPs/SiNWs - silic nanơ dây có bao phủ hạt nanô bạc ASiNW - dây nanô silic xếp thẳng hàng CVD - lắng đọng hóa học từ pha DC - nguồn điện chiều Đ.V.T.Y - đơn vị tùy ý EDX - phổ tán sắc lượng tia X EM - điện từ LSPR - cộng hưởng plasmon bề mặt định xứ MACE - ăn mịn hóa học có trợ giúp kim loại MAECE - ăn mòn điện hóa có trợ giúp kim loại MG - malachite green NW - dây nanô OAG - mọc với hỗ trợ ơxít OASiNW - dây nanơ silic xiên xếp thẳng hàng PVD - lắng đọng vật lý từ pha PL - quang huỳnh quang PQ - paraquat QCE - hiệu ứng giam giữ lượng tử QCLC - giam giữ lượng tử - tâm phát quang RIE - ăn mịn ion phản ứng SEM - kính hiển vi điện tử quét SERS - tán xạ Raman tăng cường bề mặt SiNW - dây nanô silic TEM - kính hiển vi điện tử truyền qua VASiNW - dây nanô silic thẳng đứng xếp thẳng hàng 153 Single-Crystalline Silicon Nanowire Arrays near Room Temperature, Adv Mater., Vol 20, 3811 – 3815 23 C Y Hsiao, C H Lin, C H Hung, C J Su, Y R Lo, C C Lee, H C Lin, F H Ko, T Y Huang, and Y S Yang (2009), Novel poly-silicon nanowire field effect transistor for biosensing application, Biosen.Bioelectron., Vol 24, 1223 – 1229 24 C Zhang, C Li, Z Liu, J Zheng, C Xue, Y Zuo, B Cheng, and Q Wang (2013), Enhanced photoluminescence from porous silicon nanowire arrays, Nanoscale Res Lett., Vol 8, 277.1 – 277.4 25 D A Long (2002), The Raman Effect: A Unified Treatment of the Theory of Raman Scattering by Molecules, John Wiley & Sons 26 D D Malinovska, M S Vassileva, N Tzenov, and M Kamenova (1997), Preparation of thin porous silicon layers by stain etching, Thin Solid Films, Vol 297, – 12 27 D H Murgida, and P Hildebrandt (2004), Electron-transfer processes of cytochrome C at interfaces New insights by surface-enhanced resonance Raman spectroscopy, Acc Chem Res., Vol 37, 854 – 861 28 D K Nagesha, M A Whitehead, and J L Coffer (2005), Biorelevant Calcification and Non-Cytotoxic Behavior in Silicon Nanowires, Adv Mater., Vol 17, 921 – 924 29 D Li, Y Wu, P Kim, L Shi, P Yang, and A Majumdar (2003), Thermal conductivity of individual silicon nanowires, Appl Phys Lett., Vol 83, 2934 – 2936 30 D L Jeanmaire, and R P V Duyne (1977), Surface raman spectroelectrochemistry: Part I Heterocyclic, aromatic, and aliphatic amines adsorbed on the anodized silver electrode, J Electroanal Chem., Vol 84, 1–20 31 D R Kim, C H Lee, and X L Zheng (2009), Probing Flow Velocity with Silicon Nanowire Sensors, Nano Lett., Vol 9, 1984 – 1988 32 D R Turner, On the Mechanism of Chemically Etching Germanium and Silicon (1960), J Electrochem Soc., Vol 107, 810 – 816 33 D T Cao, L T Q Ngan, T V Viet, and C T Anh (2013), Effect of AgNO3 concentration on structure of aligned silicon nanowire arrays fabricated via silver-assisted chemical etching, Int J Nanotechnology, Vol 10, 343 – 350 34 D T Cao, L T Q Ngan, and C T Anh (2013), Enhancement and stabilization of the photoluminescence from porous silicon prepared by electrochemical etching, Surf Interface Anal., Vol 45, 762 – 766 Ag-assisted 154 35 E C Garnett, and P Yang (2008), Silicon Nanowire Radial p−n Junction Solar Cells, J Am Chem Soc., Vol 130, 9224 – 9225 36 E C L Ru, and P G Etchegoin (2009), Principles of Surface-Enhanced Raman Spectroscopy and Related Plasmonic Effects, Elsevier 37 E C L Ru, E Blackie, M Meyer, P.G Etchegoin (2007), Surface Enhanced Raman Scattering Enhancement Factors: A Comprehensive Study, J Phys Chem C, Vol 111, 13794 – 13803 38 E F Pecora, N Lawrence, P Gregg, J Trevino, P Artoni, A Irrera, F Priolo, and L D Negro (2012), Nanopatterning of silicon nanowires for enhancing visible photoluminescence, Nanosale, Vol 4, 2863 – 2866 39 E Halfon, S Galassi, R Brüggemann, and A Porvini (1996), Selection of priority properties to assess environmental hazard of pesticides, Chemosphere, Vol 33, 1543 – 1562 40 E J Ayars, H D Hallen, and C L Jahncke (2000), Electric Field Gradient Effects in Raman Spectroscopy, Phys Rev Lett., Vol 85, 4180 – 4183 41 E Peled, F Patolsky, D Golodnitsky, K Freedman, G Davidi, and D Schneier (2015), Tissue-like Silicon Nanowires-Based Three-Dimensional Anodes for High-Capacity Lithium Ion Batteries, Nano Lett., Vol 15, 3907 – 3916 42 E Prodan, P Nordlander, and N J Halas (2003), Electronic structure and optical properties of gold nanoshells, Nano Lett., Vol 3, 1411 – 1415 43 E S Kooij, K Butter, and J J Kelly (1999), Silicon Etching in  HNO 3/ HF  Solution: Charge Balance for the Oxidation Reaction, Electrochem Solid St Lett., Vol 2, 178 – 180 44 E Temur, I H Boyacı, U Tamer, H Unsal, and N Aydogan (2010), A highly 45 46 47 48 sensitive detection platform based on surface-enhanced Raman scattering for Escherichia coli enumeration, Anal Bioanal Chem., Vol 397, 1595 – 1604 F Deiss, N Sojic, D J White, and P R Stoddart, Nanostructured optical fibre arrays for high-density biochemical sensing and remote imaging, Anal Bioanal Chem., Vol 396 (2010), 53 – 71 F Koch (1993), Models and mechanisms for the luminescence of porous Si, Mater Res Soc Symp Proc., Vol 298, 319 – 329 F Koch, V Petrova-Koch (1996), Light from Si-nanoparticle systems - a comprehensive view, J Non-Cryst Solids, Vol 198-200, 840 – 846 F Patolsky, B P Timko, G H Yu, Y Fang, A B Greytak, G F Zheng, and C M Lieber (2006), Detection, stimulation, and inhibition of neuronal signals with 155 high-density nanowire transistor arrays, Science, Vol 313, 1100 – 1104 49 F Peng, Y Su, , X Ji, Y Zhong, X Wei, Y He (2014), Doxorubicin-loaded silicon nanowires for the treatment of drug-resistant cancer cells, Biomaterials, Vol 35, 5188 – 5195 50 G Belomoin, J Therrien, A Smith, S Rao, R Twesten, S Chaieb, M H Nayfeh, L Wagner and L Mitas (2002), Observation of a magic discrete family of ultrabright Si nanoparticles, Appl Phys Lett., Vol 80, 841 – 843 51 G Gautier, and P Leduc (2014), Porous silicon for electrical isolation in radio frequency devices: A review, Appl Phys Rev., Vol 1, 011101.1 – 011101.18 52 G G Qin and Y Q Jia (1993), Mechanism of the visible luminescence in porous silicon, Solid State Communications, Vol 86, 559 – 563 53 G G Qin, and Y J Li (2003), Photoluminescence mechanism model for oxidized porous silicon and nanoscale-silicon-particle-embedded silicon oxide, Phys Rev.B, Vol 68, 085309.1 – 085309.7 54 G J Zhang, A Agarwal, K D Buddharaju, N Singh, and Z Q Gao (2007), Highly sensitive sensors for alkali metal ions based on complementary-metal-oxidesemiconductor-compatible silicon nanowires, Appl Phys Lett., Vol 90, 233903.1 – 233903.3 55 G X Zhang (2005), Electrochemistry of Si and Its Oxide, Kluwer Academic Publishers 56 G X Zhang, S D Collins, and R L Smith (1989), Porous Silicon Formation and Electropolishing of Silicon by Anodic Polarization in  HF  Solution, J Electrochem Soc., Vol 136, 1561 – 1565 57 H Fang, Y Wu, J Zhao, and J Zhu (2006), Silver catalysis in the fabrication of silicon nanowire arrays, Nanotechnology, Vol 17, 3768 – 3774 58 H Foll, M Christophersen, J Carstensen, G Hasse (2002), Formation and application of porous silicon, Mater Sci Eng R, Vol 39, 93 – 141 59 H H Wang, C Y Liu, S B Wu, N W Liu, C Y Peng, T H Chan, C F Hsu, J K Wang, and Y L Wang (2006), Highly Raman-Enhancing Substrates Based on Silver Nanoparticle Arrays with Tunable Sub-10 nm Gaps, Adv Mater., Vol 18, 491 – 495 60 H Koyama (2006), Photoluminescence properties of porous silicon layers prepared by electrochemical etching in extremely dilute HF solutions, Journal of Applied Electrochemistry , Vol 36, 999 – 1003 61 H Seidel, L Csepregi, A Heuberger, and H Baumgärtel (1990), Anisotropic 156 Etching of Crystalline Silicon in Alkaline Solutions I Orientation Dependence and Behavior of Passivation Layers, J Electrochem Soc., Vol 137, 3612 – 3626 62 H Tomioka, and S Adachi (2013), Optical Absorption, Photoluminescence, and Raman Scattering Studies on Si Nanowire Arrays Formed in Ag2SO4−HF−H2O Solution, ECS J Solid State Sci Technol., Vol 2, P253 – P258 63 H Wang, X Han, X Ou, C S Lee, X Zhang, S T Lee (2013), Silicon nanowire based single-molecule SERS sensor, Nanoscale, Vol 5, 8172 – 8176 64 H Xu, J Aizpurua, M Kall, and P Apell (2000), Electromagnetic contributions to single-molecule sensitivity in surface-enhanced raman scattering, Phys Rev E, Vol 62, 4318 – 4324 65 I Ponomareva, M Menon, E Richter, and A N Andriotis (2006), Structural stability, electronic properties, and quantum conductivity of small-diameter silicon nanowires, Phys Rev B, Vol 74, 125311.1 – 125311.5 66 I Ponomareva, D Srivastava, and M Menon (2007), Thermal Conductivity in Thin Silicon Nanowires: Phonon Confinement Effect, Nano Lett., Vol 7, 1155 – 1159 67 J A Creighton, C G Blatchford, and M G Albrecht, Plasma resonance enhancement of Raman scattering by pyridine adsorbed on silver or gold sol particles of size comparable to the excitation wavelength, J Chem Soc., Faraday Trans 2, Vol 75 (1979), 790 – 798 68 J A Dieringer, A D McFarland, N C Shah, D A Stuart, A V Whitney, C R Yonzon, M A Young, X Zhang, and R P Van Duyne (2006), Introductory Lecture: Surface enhanced Raman spectroscopy: new materials, concepts, characterization tools, and applications, Faraday Discuss., Vol 132, – 26 69 J A Rodríguez, M A Vásquez-Agustín, A Morales-Sánchez, and M AcevesMijares (2014), Emission Mechanisms of Si Nanocrystals and Defects in SiO2 Materials, J Nanomater., Vol 2014, 409482.1 – 409482.17 70 J A Yan, L Yang, and M Y Chou (2007), Size and orientation dependence in the electronic properties of silicon nanowires, Phys Rev B, Vol 76, 115319.1 – 115319.6 71 J E Allen, E R Hemesath, D E Perea, J L Lenscch-Falk, Z Y Li, F Yin, M H Gass, P Wang, A L Bleloch, R E Palmer, and L J Lauhon (2008), Highresolution detection of Au catalyst atoms in Si nanowires, Nat Nanotechnol., Vol 3, 168 – 173 72 J Jiang, K Bosnick, M Maillard, and L Brus (2003), Single Molecule Raman 157 Spectroscopy at the Junctions of Large Ag Nanocrystals, J Phys Chem B, Vol 107, 9964 – 9972 73 J K Sass, H Neff, M Moskovits, and S Holloway (1981), Electric field gradient effects on the spectroscopy of adsorbed molecules, J Phys Chem., Vol 85 , 621 – 623 74 J P Wilcoxon, G A Samara, and P N Provencio (1999), Optical and electronic properties of Si nanoclusters synthesized in inverse micelles, Phys Rev.B: Condens Matter Mater Phys., Vol 60, 2704 – 2714 75 J R Maiolo, B M Kayes, M A Filler, M C Putnam, M D Kelzenberg, H A Atwater, and N S Lewis (2007), High Aspect Ratio Silicon Wire Array Photoelectrochemical Cells, J Am Chem Soc., Vol 129, 12346 – 12347 76 J Wang, and J.S Wang (2007), Dimensional crossover of thermal conductance in nanowires, Appl Phys Lett., Vol 90 , 241908.1 – 241908.3 77 J Zhu, and Y Cui (2010), Photovoltaics: More solar cells for less, Nature Mater., Vol 9, 183 – 184 78 K A Willets, and R P Van Duyne (2007), Localized Surface Plasmon Resonance Spectroscopy and Sensing, Annu Rev Phys Chem., Vol 58, 267-297 79 K D Sattler (2011), Handbook of nanophysics: Nanoelectronics and nanophotonics, Taylor and Francis Group 80 K E Shafer-Peltier, C L Haynes, M R Glucksberg, and R P Van Duyne (2003), Toward a glucose biosensor based on surface-enhanced Raman scattering, J Am Chem Soc., Vol 125, 588 – 593 81 K Kneipp, H Kneipp, V B Kartha, R Manoharan, G Deinum, I Itzkan, R R Dasari, and M S Feld (1998), Detection and identification of a single DNA base molecule using surface-enhanced Raman scattering (SERS), Phys.Rev E, Vol 57, R6281 – R6284 82 K Kneipp, H Kneipp, I Itzkan, R R Dasari, and M S Feld (2002), Surfaceenhanced Raman scattering and biophysics, J Phys.: Condens Matter, Vol 14, R597 – R624 83 K Kneipp, Y Wang, H Kneipp, L T Perelman, I Itzkan, R R Dasari, and M.S Feld (1997), Single Molecule Detection Using Surface-Enhanced Raman Scattering (SERS), Phys Rev Lett., Vol 78, 1667 – 1670 84 K Niki, Y Kawasaki, Y Kimura, Y Higuchi, and N Yasuoka (1987), Surfaceenhanced Raman scattering of cytochromes c3 adsorbed on silver electrode and their redox behavior, Langmuir, Vol , 982 – 986 158 85 K Omar, Y Al-Douri, A.Ramizy, and Z Hassan (2011), Stiffness properties of porous silicon nanowires fabricated by electrochemical and laser-induced etching, Superlattice Microst., Vol 50, 119 – 127 86 K Q Peng, A Lu, R Zhang, and S T Lee (2008), Motility of Metal Nanoparticles in Silicon and Induced Anisotropic Silicon Etching, Adv Funct Mater., Vol 18, 3026 – 3035 87 K Q Peng, and J Zhu (2003), Simultaneous gold deposition and formation of silicon nanowire arrays, J Electroanal Chem., Vol 558, 35 – 39 88 K Q Peng, and J Zhu (2004), Morphological selection of electroless metal deposits on silicon in aqueous fluoride solution, Electrochim Acta, Vol 49, 2563 – 2568 89 K Q Peng, H Fang, J Hu, Y Wu, J Zhu, Y Yan, and S T Lee (2006), MetalParticle-Induced, Highly Localized Site-Specific Etching of Si and Formation of Single-Crystalline Si Nanowires in Aqueous Fluoride Solution, Chem Eur J., Vol 12, 7942 – 7947 90 K Q Peng, J J Hu, Y J Yan, Y Wu, H Fang, Y Xu, S T Lee, and J Zhu (2006), Fabrication of Single‐Crystalline Silicon Nanowires by Scratching a Silicon Surface with Catalytic Metal Particles, Adv Funct Mater., Vol 16, 387 – 394 91 K Q Peng, J S Jie, W J Zhang, and S T Lee (2008), Silicon nanowires for rechargeable lithium-ion battery anodes, Appl Phys Lett., Vol 93, 033105 – 033107 92 K Q Peng, M L Zhang, A J Lu, N B Wong, R Q Zhang, and S T Lee (2007), Ordered silicon nanowire arrays via nanosphere lithography and metal-induced etching, Appl Phys Lett., Vol 90, 163123-1 – 163123-3 93 K Q Peng, Y Xu, Y Wu, Y Yan, S T Lee, and J Zhu (2005), Aligned SingleCrystalline Si Nanowire Arrays for Photovoltaic Applications, Small, Vol 1, 1062 – 1067 94 K Q Peng, Y Wu, H Fang, X Zhong, Y Xu, and J Zhu (2005), Uniform, AxialSilicon Orientation Alignment of One-Dimensional Single-Crystal Nanostructure Arrays, Angew Chem Int Ed., Vol 44, 2737 – 2742 95 K Q Peng, Y J Yan, S P Gao, and J Zhu (2003), Dendrite-Assisted Growth of Silicon Nanowires in Electroless Metal Deposition, Adv Funct Mater., Vol 13, 127 – 132 96 K S Brammer, C Choi, S Oh, C J Cobb, L S Connelly, M Loya, S D Kong, and S Jin, Antibiofouling, Sustained Antibiotic Release by Si Nanowire 159 Templates, Nano Lett., Vol (2009), 3570 – 3574 97 K Tsujino, and M Matsumura (2005), Boring Deep Cylindrical Nanoholes in Silicon Using Silver Nanoparticles as a Catalyst, Adv Mater., Vol 17, 1045 – 1047 98 L A Dick, A J Haes, and R P V Duyne, Distance and Orientation Dependence of Heterogeneous Electron Transfer:  A Surface-Enhanced Resonance Raman Scattering Study of Cytochrome c Bound to Carboxylic Acid Terminated Alkanethiols Adsorbed on Silver Electrodes, J Phys Chem B, Vol 104 (2000), 11752 – 11762 99 L B Luo, J S Jie, W F Zhang, Z B He, J X Wang, G D Yuan, W J Zhang, L C M Wu, and S T Lee (2009), Silicon nanowire sensors for Hg2+ and Cd2+ ions, Appl Phys Lett., Vol 94, 193101.1 – 193101.3 100 L H Lin, X Z Sun, R Tao, Z C Li, J Y Feng, and Z J Zhang (2011),Photoluminescence origins of the porous silicon nanowire arrays, J Appl Phys 110, 073109.1 – 073019.6 101 L Lin, X Sun, R Tao, J Feng, and Z Zhang (2011), The synthesis and photoluminescence properties of selenium-treated porous silicon nanowire arrays, Nanotechnology, Vol 22, 075203.1 – 075203.6 102 L Liu (2014), Regulation of the morphology and photoluminescence of silicon nanowires by light irradiation, J Mater Chem C, Vol 2, 9631 – 9636 103 L T Canham (1990), Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers, Appl Phys Lett., Vol 57, 1046 – 1048 104 L T Canham, M R Houlton, W Y Leong, C Pickering and J M Keen (1991), Atmospheric impregnation of porous silicon at room temperature, Journal of Applied Physics, Vol 70, pp 422-431 105 L T Q Ngan, C.T Anh, D T Cao (2013), Fabrication of aligned silicon nanowire arrays via metal-assisted electrochemical etching, Proc of IWAMSN 2012, October 30th – November 2nd 2012, Halong City, Vietnam, 104 – 107 106 L T Q Ngan, C.T Anh, D T Cao (2014), Fabrication of aligned SiNW arrays via metal-assisted chemical etching, Journal of Science and Technology, Vol 52, – 107 L T Q Ngan, C.T Anh, D T Cao (2015), Fabrication of vertical aligned silicon nanowire arrays with strong photoluminescence by metal-assisted electrochemical etching, Proc of IWNA 2015, 11 – 14 November 2015, Vung Tau, Vietnam, 352 – 355 108 L T Q Ngan, D T Cao, C T Anh, and L V.Vu (2015), Improvement of Raman 160 enhancement factor due to the use of silver nanoparticles coated obliquely aligned silicon nanowire arrays in SERS measurements, Int J Nanotechnol., Vol 12, 358 – 366 109 L X Mu, W S Shi, J C Chang, and S T Lee (2008), Silicon Nanowires-Based Fluorescence Sensor for Cu(II), Nano Lett., Vol 8, 104 – 109 110 L Zeiri, K Rechav, Z Porat, and Y Zeiri (2012), Silver nanoparticles deposited on porous silicon as a surface-enhanced Raman scattering (SERS) active substrate, Appl Spectrosc., Vol 66, 294 – 299 111 M Fan, G F.S Andrade, and A G Brolo (2011), A review on the fabrication of substrates for surface enhanced Raman spectroscopy and their applications in analytical chemistry, Anal Chim Acta, Vol 693, – 25 112 M Fleischmann, P J Hendra, and A J McQuillan (1974), Raman spectra of pyridine adsorbed at a silver electrode, Chem Phys Lett., Vol 26 , 163 – 166 113 M G Albrecht, and J A Creighton, Anomalously intense Raman spectra of pyridine at a silver electrode, J Am Chem Soc., Vol 99 (1977), 5215 – 5217 114 M J Natan (2006), Concluding Remarks Surface enhanced Raman scattering, Faraday Discuss., Vol 132, 321 – 328 115 M K Dawood, S Tripathy, S B Dolmanan, T H Ng, H Tan, and J Lam (2012), Influence of catalytic gold and silver metal nanoparticles on structural, optical, and vibrational properties of silicon nanowires synthesized by metal-assisted chemical etching, J Appl Phys., Vol 112, 073509.1 – 073509.8 116 M Khorasaninejad, M A Swillam, K Pillai, and S S Saini (2012), Silicon nanowire arrays with enhanced optical properties, Opt Lett., Vol 37, 4194 – 4196 117 M Lajvardi, H Eshghi, M E Ghazi, M Izadifard, A Goodarzi (2015), Structural and optical properties of silicon nanowires synthesized by Ag-assisted chemical etching, Materials Mater Sci Semicond Process., Vol 40, 556 – 563 118 M Lajvardi, H Eshghi, M Izadifard, M E Ghazi, and A Goodarzi (2016), Effects of silver and gold catalytic activities on the structural and optical properties of silicon nanowires, Physica E, Vol 75, 136 – 143 119 M L Zhang, C Q Yi, X Fan, K Q Peng, N B Wong, M S Yang, R Q Zhang, and S T Lee (2008), A surface-enhanced Raman spectroscopy substrate for highly sensitive label-free immunoassay, Appl Phys Lett., Vol 92, 043116.1 – 043116.3 120 M Moskovits (1985), Surface-enhanced spectroscopy, Rev Mod Phys., Vol 57, 161 783 – 826 121 M Moskovits (2006), Surface-Enhanced Raman Spectroscopy: a Brief Perspective, Topics Appl Phys., Vol 103, – 17 122 M Naddaf and H Hamadeh (2009), Visible luminescence in photoelectrochemically etched p-type porous silicon: Effect of illumination wavelength, Materials Science and Engineering C, Vol 29, 2092 – 2098 123 M Otto, M Algasinger, H Branz, B Gesemann, T Gimpel, K Füchsel, T Käsebier, S Kontermann, S Koynov, X Li, V Naumann, J Oh , A N Sprafke, J Ziegler, M Zilk, and R B Wehrspohn (2015), Black Silicon Photovoltaics, Adv Optical Mater., Vol 3, 147-164 124 M V Wolkin, J Jorne, P M Fauchet, G Allan, and C Delerue (1999), Electronic States and Luminescence in Porous Silicon Quantum Dots: The Role of Oxygen, Phys Rev Lett., Vol 82, 197 – 200 125 M W Shao, H Yao, M L Zhang, N B Wong, Y Y Shan, and S T Lee (2005), Fabrication and application of long strands of silicon nanowires as sensors for bovine serum albumin detection, Appl Phys Lett., Vol 87, 183106.1 – 183106.3 126 M W Shao, M L Zhang, N B Wong, D D D Ma, H Wang, W W Chen, and S T Lee (2008), Ag-modified silicon nanowires substrate for ultrasensitive surface-enhanced raman spectroscopy, Appl Phys Lett., Vol 93, 233118.1 – 233118.2 127 M W Shao, Y Y Shan, N B Wong, and S T Lee (2005), Silicon Nanowire Sensors for Bioanalytical Applications: Glucose and Hydrogen Peroxide Detection, Adv Funct Mater., Vol 15, 1478 – 1482 128 M Z Si, Y P Kang, R M Liu (2012), Surface-enhanced Raman scattering (SERS) spectra of three kinds of azo-dye molecules on silver nanoparticles prepared by electrolysis, Appl Surf Sci., Vol 258, 5533 – 5537 129 O Kayser, A Lemke, and N Hernandez-Trejo (2005), The impact of nanobiotechnology on the development of new drug delivery systems, Curr Pharm Biotechnol., Vol 6, – 130 P Artoni, A Irrera, F Iacona, E F Pecora, G Franzò, and F Priolo (2012), Temperature dependence and aging effects on silicon nanowires photoluminescence, Opt Express, Vol 20, 1483 – 1490 131 P C Lee, and D Meisel (1982), Adsorption and surface-enhanced Raman of dyes on silver and gold sols, Phys Chem., Vol 86 , 3391 – 3395 132 P D Kanungo, N Zakharov, J Bauer, O Breitenstein, P Werner, and U Goesele 162 (2008), Controlled in situ boron doping of short silicon nanowires grown by molecular beam epitaxy, Appl Phys Lett., Vol 92, 263107.1 – 263107.3 133 P Kumar, P Lemmens, M Ghosh, F Ludwig, and M Schilling (2009), Effect of HF Concentration on Physical and Electronic Properties of Electrochemically Formed Nanoporous Silicon, Journal of Nanomaterials, Vol 2009, – 134 P M Fauchet, E Ettedgui, A Raisanen, L J Brillson, F Seiferth, S K Kurinec, Y Gao, C Peng and L Tsybeskov (1993), Can oxidation and other treatments help us understand the nature of lightemitting porous silicon?, Materials Research Society symposia proceedings, Vol 298, 271 - 276 135 P M M C Bressers, J J Kelly, J G E Gardeniers, and M Elwenspoek (1996), Surface Morphology of p‐Type (100) Silicon Etched in Aqueous Alkaline Solution, J Electrochem Soc., Vol 143, 1744 – 1750 136 P R Bandaru, and P Pichanusakorn (2010), An outline of the synthesis and properties of silicon nanowires, Semicond Sci Technol., Vol 25, 024003.1 024003.16 137 R A Alvarez-Puebla, and L M Liz-Marzan (2010), Environmental applications of plasmon assisted Raman scattering, Energy Environ Sci., Vol 3, 1011 – 1017 138 R A Halvorson, and P J Vikesland (2010), Surface-Enhanced Raman Spectroscopy (SERS) for Environmental Analyses, Environ Sci Technol., Vol 44 , 7749 – 7755 139 R Gao, N Choi, S I Chang, S H Kang, J M Song, S I Cho, D W Lim, and J Choo (2010), Highly sensitive trace analysis of paraquat using a surfaceenhanced Raman scattering microdroplet sensor, Anal Chim Acta, Vol 681, 87 – 91 140 R J C Brown, J Wang, R Tantra, R E Yardley, and M J T Milton (2006), Electromagnetic modelling of raman enhancement from nanoscale substrates: a route to estimation of the magnitude of the chemical enhance ment mechanism in SERS, Faraday Discuss., Vol 132, 201 – 213 141 R Picorel, G Chumanov, T.M Cotton, G Montoya, S Toon, and M Seibert (1994), Surface-Enhanced Resonance Raman Scattering Spectroscopy of Photosystem II Pigment-Protein Complexes, J Phys Chem., Vol 98 , 6017 – 6022 142 R R.Sato-Berru, R Redon, A Vaquez-Olmos, and J M Saniger (2009), Silver nanoparticles synthesized by direct photoreduction of metal salts Application in surface-enhanced Raman spectroscopy, J Raman Spectrosc., Vol 40, 376 – 380 143 R Rurali (2010), Colloquium: Structural, electronic, and transport properties of 163 silicon nanowires, Rev.Mod.Phys., Vol 82, 427 – 449 144 R S Wagner, and W C Ellis (1965), The vapor-Liquid-Solid Mechanism of Crystal Growth and Its Application to Silicon, Trans Metall Soc AIME, Vol 233, 1053 145 S A Razek, M A Swillam, and N K Allam (2014), Vertically aligned crystalline silicon nanowires with controlled diameters for energy conversion applications: Experimental and theoretical insights, J Appl Phys., Vol 115, 194305.1 – 194305.8 146 S Chattopadhyay, and P W Bohn (2004), Direct-write patterning of microstructured porous silicon arrays by focused-ion-beam FPt deposition and metal-assisted electroless etching, J Appl Phys., Vol 96, 6888 – 6894 147 S Chattopadhyay, X L Li, and P W Bohn (2002), In-plane control of morphology and tunable photoluminescence in porous silicon produced by metal-assisted electroless chemical etching, J Appl Phys., Vol 91, 6134 – 6140 148 S Congli, H Hao, F Huanhuan, X Jingjing, C Yu, J Yong, J Zhifeng, S Xiaosong (2013), Synthesis of porous silicon nano-wires and the emission of red luminescence, Appl Surf Sci., Vol 282, 259 – 263 149 S Cruz, A Honig-dOrville, and J Muller (2005), Fabrication and Optimization of Porous Silicon Substrates for Diffusion Membrane Applications, J Electrochem Soc., Vol 152, C418 – C424 150 S J Oldenburg, J B Jackson, S L Westcott, and N J Halas (1999), Infrared extinction properties of gold nanoshells, Appl Phys Lett., Vol 75, 2897 – 2899 151 S K Saxena, H M Rai, R Late, P R Sagdeo, and R Kumar (2015), Origin of Photoluminescence from Silicon nanowires Prepared by Metal Induced Etching (MIE), AIP Conf Proc., Vol 1661, 080027.1 – 080027.3 152 S M Prokes (1993), Light emission in thermally oxidized porous silicon: Evidence for oxide‐related luminescence, Applied Physics Letters, Vol 64, 3244 – 3246 153 S Nie, and S R Emory (1997), Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering, Science, Vol 275 , 1102 – 1106 154 S Shanmukh, L Jones, J Driskell, Y Zhao, R Dluhy, and R A Tripp (2006), Rapid and Sensitive Detection of Respiratory Virus Molecular Signatures Using a Silver Nanorod Array SERS Substrate, Nano Lett., Vol 6, 2630 – 2636 155 S Su, Y He, M L Zhang, K Yang, S P Song, X H Zhang, C H Fan, and S T 164 Lee (2008), High-sensitivity pesticide detection via silicon nanowires-supported acetylcholinesterase-based electrochemical sensors, Appl Phys Lett., Vol 93, 023113.1 – 023113.2 156 S Veprek, and M G J Veprek-Heijman (2015), Photoluminescence from nanocrystalline silicon nc-Si, nc-Si/SiO2 nanocomposites, and nc-Si oxidized in O2 and treated in H2O, Vac Sci Technol A, Vol 33, 043001.1 - 043001.4 157 S W Chang, V P Chuang, S T Boles, C A Ross, and C V Thompson (2009), Densely Packed Arrays of Ultra-High-Aspect-Ratio Silicon Nanowires Fabricated using Block-Copolymer Lithography and Metal-Assisted Etching, Adv Funct Mater., Vol 19, 2495 – 2500 158 S Yae, Y Kawamoto, H Tanaka, N Fukumuro, and H Matsuda (2003), Formation of porous silicon by metal particle enhanced chemical etching in HF solution and its application for efficient solar cells, Electrochem Commun., Vol 5, 632 – 636 159 S.Y Chen, Y.H Huangb, H.K Lai, C Li, J.Y Wang (2007), Investigation of passivation of porous silicon at room temperature, Solid State Communications, Vol 142, pp 358–362 160 T C Dao, T Q N Luong, T A Cao, N H Nguyen, N M Kieu, T T Luong, and V V Le (2015), Trace detection of herbicides by SERS technique, using SERS- 161 162 163 164 active substrates fabricated from different silver nanostructures deposited on silicon, Adv Nat Sci.: Nanosci Nanotechnol., Vol 6, 035012.1 – 035012.6 T Hadjersi (2007), Oxidizing agent concentration effect on metal-assisted electroless etching mechanism in HF-oxidizing agent-H2O solutions, Appl Surf Sci., Vol 253, 4156 – 4160 T Kang, S M Yoo, I Yoon, S Y Lee, and B Kim (2010), Patterned Multiplex Pathogen DNA Detection by Au Particle-on-Wire SERS Sensor, Nano Lett., Vol 10 , 1189 – 1193 T Selvaraju, and R Ramaraj (2009), Electrocatalytic reduction of hydrogen peroxide at nanostructured copper modified electrode, J Appl Electrochem., Vol 39, 321 – 327 T Q N Luong, T A Cao, and T C Dao (2013), Low-concentration organic molecules detection via surface-enhanced Raman spectroscopy effect using Ag nanoparticles-coated silicon nanowire arrays, Adv Nat Sci.: Nanosci Nanotechnol., Vol 4), 015018.1 – 015018.5 165 T T Nhung, and S W Lee (2014), Green Synthesis of Asymmetrically Textured 165 Silver Meso-Flowers (AgMFs) as Highly Sensitive SERS Substrates, ACS Appl Mater Interfaces, Vol , 21335 – 21345 166 T Unagami (1980), Formation Mechanism of Porous Silicon Layer by Anodization in  HF  Solution, J Electrochem Soc., Vol 127, 476 – 483 167 T Vo-Dinh, L R Allain, and L David (2002), Cancer gene detection using surface-enhanced Raman scattering (SERS), J Raman Spectrosc., Vol 33, 511 – 516 168 T Vo-Dinh (1998), Surface-enhanced Raman spectroscopy using metallic nanostructures, Trac-Tren Anal Chem., Vol 17, 557 – 582 169 U K Sur, and J Chowdhury (2013), Surface-enhanced Raman scattering: overview of a versatile technique used in electrochemistry and nanoscience, Curr Sci., Vol 105, 923 – 939 170 V A Sivakov, F Voigt, A Berger, G Bauer, and S H Christiansen (2010), Roughness of silicon nanowire sidewalls and room temperature photoluminescence, Phys Rev B, Vol 82, 125446.1 – 125446.6 171 V Lehmann (2002), Electrochemistry of silicon: instrumentation, science, materials, and applications, Wiley-VCH 172 V Lehmann (1993), The Physics of Macropore Formation in Low Doped n-Type Silicon, J Electrochem Soc., Vol 140, 2836 – 2843 173 V Schmidt, J V Wittemann, and U Gosele (2010), Growth, Thermodynamics, and Electrical Properties of Silicon Nanowires, Chem Rev., Vol 110, 361–388 174 V Schmidt, S Senz, and U Gösele (2005), Diameter-Dependent Growth Direction of Epitaxial Silicon Nanowires, Nano Lett., Vol 5, 931 – 935 175 W Kim, J K Ng, M E Kunitake, B R Conklin, and P D Yang (2007), Interfacing Silicon Nanowires with Mammalian Cells, J Am Chem Soc., Vol 129, 7228 – 7229 176 W L Barnes, A Dereux, and T W Ebbesen (2003), Surface plasmon subwavelength optics, Nature, Vol 424, 824 – 830 177 W W Chen, H Yao, C H Tzang, J J Zhu, M S Yang, and S T Lee (2006), Silicon nanowires for high-sensitivity glucose detection, Appl Phys Lett., Vol 88, 213104.1 – 213104.3 178 X Li, and P W Bohn (2000), Metal-assisted chemical etching in HF/H2O2 produces porous silicon, Appl Phys Lett., Vol 77, 2572 – 2574 179 X M Qian, X H Peng, D O Ansari, Q Yin-Goen, G Z Chen, D M Shin, L Yang, A N Young, M D Wang, and S M Nie (2008), In vivo tumor targeting 166 and spectroscopic detection with surface-enhanced Raman nanoparticle tags, Nat Biotechnol., Vol 26 , 83 – 90 180 X N He, Y Gao, M Mahjouri-Samani, P N Black, J Allen, M Mitchell, W Xiong, Y S Zhou, L Jiang, and Y F Lu (2012), Surface-enhanced Raman spectroscopy using goldcoated horizontally aligned carbon nanotubes, Nanotechnology, Vol 23, 205702.1 – 20572.9 181 X Q Zheng, C.E Liu, X.M Bao, F Yan and H.C Yang (1993), Midgap localized states and light emission of porous silicon, Solid State Communication, Vol 87, 1005 – 1007 182 X T Wang, W S Shi, G W She, L X Mu, and S T Lee (2010), Highperformance surface-enhanced Raman scattering sensors based on Ag nanoparticles-coated Si nanowire arrays for quantitative detection of pesticides, Appl.Phys Lett., Vol 96, 053104.1 – 053104.3 183 X T Vu, J F Eschermann, R Stockmann, R GhoshMoulick, A Offenhausser, and S Ingebrandt (2009), Top-down processed silicon nanowire transistor arrays for biosensing, Phys Status Solidi A, Vol 206, 426 – 434 184 X Y Bi, W L Wong, W J Ji, A Agarwal, N Balasubramanian, and K L Yang (2008), Development of electrochemical calcium sensors by using silicon nanowires modified with phosphotyrosine, Biosen Bioelectron., Vol 23, 1442 – 1448 185 Y Harade, X Li, P W Bohn, and R G Nuzzo (2001), Catalytic amplification of the soft lithographic patterning of Si Nonelectrochemical orthogonal fabrication of photoluminescent porous Si pixel arrays, J Am Chem Soc., Vol 123, 8709 – 8717 186 Y He, S Su, T Xu, Y Zhong, J A Zapien, J Li, C Fan, and S T Lee (2011), Silicon nanowires-based highly-efficient SERS-active platform for ultrasensitive DNA detection, Nano Today, Vol 6, 122 – 130 187 Y Kanemitsu, H Uto, Y Masumoto, T Matsumoto, T Futagi, and H Mimura (1993), Microstructure and optical properties of freestanding porous silicon films: size dependence of absorption spectra in Si nanometer-sized crystallites, Phys Rev.B, Vol 48, 2827 – 2830 188 Y Kanemitsu, T Ogawa, K Shiraishi, and K Takeda (1993), Visible photoluminescence from oxidized Si nanometer-sized spheres: Exciton confinement on a spherical shell, Phys Rev.B, Vol 48, 4883 – 4886 189 Y Kanemitsu (1994), Luminescence properties of nanometer-sized Si 167 crystallites: core and surface states, Phys Rev.B, Vol 49, 16845 – 16848 190 Y Qu, L Liao, Y Li, H Zhang, Y Huang, and X Duan (2009), Electrically Conductive and Optically Active Porous Silicon Nanowires, Nano Lett., Vol , 4539 – 4543 191 Y Wang, K K Lew, T.T Ho, L Pan, S W Novak, E C Dickey, J M Redwing, and T S Mayer (2005), Use of Phosphine as an n-Type Dopant Source for Vapor−Liquid−Solid Growth of Silicon Nanowires, Nano Lett., Vol , 2139 – 2143 192 Y Zhao, D Li, W Sang, D Yang, and M Jiang (2007), The optical properties of porous silicon produced by metal-assisted anodic etching, J Mater Sci., Vol 42, 8496 – 8500 193 Z L Yang, J Aizpurua, and H X Xu (2009), Electromagnetic field enhancement in TERS configurations, J Raman Spectrosc., Vol 40, 1343 – 1348 194 Z P Huang, N Geyer, P Werner, J Boor, and U Gösele (2010), Metal-Assisted Chemical Etching of Silicon: A Review, Adv Mater., Vol XX, – 24 195 Z P Huang, N Geyer, L F Liu, M Y Li, and P Zhong (2010), Metal-assisted electrochemical etching of silicon, Nanotechnology, Vol 21, 465301.1 – 465301.6 196 Z P Huang, T Shimizu, S Senz, Z Zhang, N Geyer, and U Gosele (2010), Oxidation Rate Effect on the Direction of Metal-Assisted Chemical and Electrochemical Etching of Silicon, J Phys Chem C, Vol 114, 10683 – 10690 197 Z P Huang, T Shimizu, S Senz, Z Zhang, X X Zhang, W Lee, N Geyer, and U Gosele (2009), Ordered Arrays of Vertically Aligned [110] Silicon Nanowires by Suppressing the Crystallographically Preferred Etching Directions, Nano Lett., Vol , 2519 – 2525 198 Z P Huang, X Zhang, M Reiche, L Liu, W Lee, T Shimizu, S Senz, and U Gosele (2008), Extended Arrays of Vertically Aligned Sub-10 nm Diameter [100] Si Nanowires by Metal-Assisted Chemical Etching, Nano Lett., Vol 8, 3046 – 3051 199 Z Q Gao, A Agarwal, A D Trigg, N Singh, C Fang, C H Tung, Y Fan, K D Buddharaju, and J M Kong (2007), Silicon Nanowire Arrays for Label-Free Detection of DNA, Anal Chem., Vol 79, 3291 – 3297 200 Z Y Jiang, X X Jiang, S Su, X P Wei, S T Lee, and Y He (2012), Siliconbased reproducible and active surface-enhanced Raman scattering substrates for sensitive, specific, and multiplex DNA detection, Appl Phys Lett., Vol 100, 203104-1 – 203104-4