Fabrication and investigation of characteristics of photonic microcavity 1d for optical sensors

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY  NGUYEN THUY VAN FABRICATION AND INVESTIGATION OF CHARACTERISTICS OF PHOTONIC MICROCAVITY 1D FOR OPTICAL SENSORS Chuyên ngành: Materials for Optics Optoelectronics and Photonics Code: 62.44.01.27 SUMMARY OF SCIENCE MATERIALS DOCTORAL THESIS Hanoi - 2018 9. The thesis was completed at Key Laboratory for Electronic Materials and Devices, Institute of Materials Science, Vietnam Academy of Science and Technology. Supervisors: 1. Assocc. Prof. Dr. Pham Van Hoi 2. Assocc. Prof. Dr. Bui Huy Reviewer 1: Reviewer 2: Reviewer 3: The dissertation will be defended at Graduate University of Science and Technology, 18 Hoang Quoc Viet street, Hanoi. Time:...........,............., 2018 The thesis could be found at: - National Library of Vietnam - Library of Graduate University of Science and Technology - Library of Institute of Science Materials LIST OF PUBLICATIONS LIST OF PUBLICATIONS USED FOR THE THESIS 1. Huy Bui, Van Hoi Pham, Van Dai Pham, Thanh Binh Pham, Thi Hong Cam Hoang, Thuy Chi Do and Thuy Van Nguyen, Development of nano-porous silicon photonic sensors for pesticide monitoring, Digest Journal of Nanomaterials and Biostructures, volume 13, No.1, January – March 2018. 2. H. Bui, V. H. Pham, V. D. Pham, T. H. C. Hoang, T. B. Pham, T. C. Do, Q. M. Ngo, and T. Van Nguyen, “Determination of low solvent concentration by nano-porous silicon photonic sensors using volatile organic compound method,” Environ. Technol., pp. 1–9, May 2018. 3. Van Hoi Pham, Huy Bui, Thuy Van Nguyen, The Anh Nguyen, Thanh Son Pham, Van Dai Pham, Thi Cham Tran, Thu Trang Hoang and Quang Minh Ngo, “Progress in the research and development of photonic structure devices”, Adv. Nat. Sci.: Nanosci. Nanotechnol. 7, 015003, 17pp, 2016. 4. Van Hoi Pham, Thuy Van Nguyen, The Anh Nguyen, Van Dai Pham and Bui Huy, “Nano porous silicon microcavity sensor for determination organic solvents and pesticide in water”, Adv. Nat. Sci.: Nanosci. Nanotechnol. 5, 045003, 9pp, 2014. 5. Bui Huy, Thuy Van Nguyen, The Anh Nguyen, Thanh Binh Pham, Quoc Trung Dang, Thuy Chi Do, Quang Minh Ngo, Roberto Coisson, and Pham Van Hoi, “A Vapor Sensor Based on a Porous Silicon Microcavity for the Determination of Solvent Solution”, Jounal of the Optical Society of Korea, Vol. 18, No. 4, pp. 301-306, 2014. 6. Van Hoi Pham, Huy Bui, Le Ha Hoang, Thuy Van Nguyen, The Anh Nguyen, Thanh Son Pham, and Quang Minh Ngo, “Nano- porous Silicon Microcavity Sensors for Determination of Organic Fuel Mixtures”, Jounal of the Optical Society of Korea, Vol. 17, No. 5, pp. 423-427, 2013. 7. Nguyen Thuy Van, Pham Van Dai, Pham Thanh Binh, Tran Thi Cham, Do Thuy Chi, Pham Van Hoi and Bui Huy, “A micro- photonic sensor based on resonant porous silicon structures for liquid enviroment monitoring”, Proc. of Advances in optics Photonics Spectroscopy & application, Ninh Binh city, Vietnam. November 6 - 10, 2016, ISBN 978-604-913-578-1, pp. 471-475, 2017. 8. Phạm Văn Hội, Bùi Huy, Nguyễn Thúy Vân, Nguyễn Thế Anh, “Thiết bị cảm biến quang tử và phương pháp để đo nồng độ dung môi hữu cơ và chất bảo vệ thực vật trong môi trường nước” sáng chế số: 16527, cấp theo quyết định số: 5424/QĐ-SHTT, ngày 24.01.2017. LIST OF PUBLICATIONS RELATED TO THE THESIS 1. Pham Van Dai, Nguyen Thuy Van, Pham Thanh Binh, Bui Ngoc Lien, Phung Thi Ha, Do Thuy Chi, Pham Van Hoi and Bui Huy, “Vapor sensor based on porous silicon microcavity for determination of methanol content in alcohol”, Proc. of Advances in optics Photonics Spectroscopy & application, Ninh Binh city, Vietnam. November 6 - 10, 2016, ISBN 978-604-913-578-1, pp. 404-408, 2017. 2. Nguyen Thuy Van, Nguyen The Anh, Pham Van Hai, Nguyen Hai Binh, Tran Dai Lam, Bui Huy and Pham Van Hoi, “Optical sensors for pesticides determaination in water using nano scale porous silicon microcavity ”, Proc. of Advances in Optics, Photonics, Spectrscopy & Applications VIII, ISSN 1859-4271, pp.603-608,2015. 3. Thuy Van Nguyen, Huy Bui, The Anh Nguyen, Hai Binh Nguyen, Dai Lam Tran, Roberto Coisson and Van Hoi Pham, “An improved nano porous silicon microcavity sensor for monitoring atrazine in water”, Proc. of The 7th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2014)- November 02-06, 2014- Ha Long City, Vietnam, ISBN: 978-604-913-301-5, pp.173-179, 2015. 1 INTRODUCTION 1. The urgency of the thesis In recent years, photonic sensors have generated an increasing interest because of their already well-known advantages, as immunity to electromagnetic interferences, high sensitivity, no impact noise and working in harsh environment. Photonic sensors are generally classified according to the physical principle including endogenous sensors and exogenous sensors. Exogenous sensors often use the physical principle that light is altered in intensity of spread; reflex; scattering; refraction; or wavelength conversion due to interaction with the external environment. These sensors are relative easiness of fabrication, but the processing of light signals varies due to the complexity of the external environment requiring high sensitivity. The endogenous photonic sensor uses the physical principle that the optical properties of sensor structure is changed when interacting with the environment. Therefore, they have very high sensitivity, easiness of signal processing and compact device size. However, the disadvantage of endogenous photonic sensor is the ability to reuses and selectivity. Endogenous photonic sensors are being promoted in research because of their extremely high sensitivity which can be combined with many specializations in chemistry and biology. At present, the sensitivity and selectivity of endogenous photonic sensors can be enhanced and have had some very good results. In general, scientists and technologists have proposed the standard approach of quantitative analysis of components with extremely small concentrations by using gas chromatography or liquid chromatography (GC / MS, LC / MS or HPLC / MS-MS) [1]-[4], 2 liquid chromatography combined with UV-Vis [5]. These methods have played a key role in the analysis of residues of low organic dissolved organic substances in the process of controlling or controlling the environment. However, these methods suffer some drawbacks since thay require professional laboratories with specialized personel and expensive equipment. In the field of electrochemical sensors [6-7], the enzyme-linked immunosorbent assay (ELISA) has been developed for determination of residues of organic matter based on the principle of antigen - antibody. The ELISA technique has high sensitivity, easiness of manipulation and rapid analysis time, so there are many models of sensor devices using the ELISA principle. The disadvantage of the ELISA approach is the low accuracy in harsh environment, inflexible due to the dependence on the chemicals of the manufacturer. Thus, finding new analytical methods is more convenient than the goal of many sensing laboratories in the world. Endothelial photonic sensors based on the principle of changing the refractive index of the sensor environment due to the interaction with environment are being extensively studied for the development of sensors in the world. Principles of transmission, interference, scattering and refraction of light is studied and applied radically in the photonic sensor based on changing the refractive index of the environment. The most recent publish reported that the optical fiber Bragg grating is capable of detecting the refractive index change to as low as 7.2x10-6 in liquid environment [8]. which allows the determination of solution at low concentration. Endothelial photonic sensors based on the 1D – nanoporous silicon microcavity (1D- NPSMC) have high sensitivity, low cost and ability to analyse 3 substances quickly and easily [9]. In recent years, scientists have promoted research on endogenous photonic sensors for determining concentrations of solvents, biological antibodies [10], cadavers petroleum contamination norms and petroleum products [11], determination of pesticide residues in water and sludge (recorded pesticide concentration at 1 ppm) [12], determination of concentration DNA level (0.1 mol / mm2 DNA concentration) [13], chemical sensor [14]. Current trends in the development of endogenous photonic sensors in the world are enhancing the sensitivity of the sensor (down to ppm), the selectivity of close- optical properties and portable sensor devices. In addition, the nano porous silicon with different porosity have different refractive indexes, so that the multilayer porous silicon can easily form an optical resonance cavity with cost low, durable in the environment for application in photonic sensor technology. The research results show that photonic sensors based on resonant cavity have the ability to measure the concentration of solvents and pesticides in the aqueous medium at extremely low concentrations. So that PSMC devices show promise for a simple and portable instruments for measuring the level of water pollution caused by organic solvents from industrial production or agricultural protective substances. Based on the large surface area of the porous silicon, the porous silicon material has become the ideal material for liquid and vapor phase sensors. The principle of pSi-sensors is a determination of the optical spectral shift caused by refractive index change of the porous silicon layers in the device due to the interaction with liquid and/or gas. The advantages of photonic sensors are highly sensitivity, so that they are suitable for determination of organic solvents or 4 pesticides at low concentrations. Therefore, “Fabrication and investigation of characteristics of photonic microcavity 1D for optical sensors” has been selected as a research topic of the thesis. 2. The objectives of the thesis i) Research and fabricate the one-dimensional (1D) – nanoporous silicon microcavity (1D-NPSMC) structures by using electrochemical etching method with the selectivity of wavelength in visible range from 200 nm to 800 nm. The 1D-NPSMC structures has high reflectivity, narrow linewidth of the pass-band and homogeneous pores ii) Design the photonic sensor device based on 1D-NPSMC structure which is capable of measuring in two modes: liquid phase (used for determination pesticides) and vapor phase (used for determination organic solvents) iii) Determinate the low concentrations of pesticides and organic solvents in aqueous medium. 3. The main contents of the thesis i) Research and fabricate 1D-NPSMC structures based on porous silicon ii) Calculate and simulate optical characteristics of 1D- NPSMC structures by using Transfer Matrix Method (TMM) iii) Design the photonic sensor device based on 1D-NPSMC structure which is capable of measuring in two modes: liquid phase (used for determination pesticides) and vapor phase (used for determination organic solvents) iv) Determinate the low concentrations of pesticides and organic solvents in aqueous medium. 4. Thesis structure: This thesis consists of 148 pages: introduction, five chapters in content, conclusion. The main results were published 5 on 06 articles was published on international journal, 01 presentation at an international workshop and 01 patent. Chapter 1: OVERVIEW ABOUT PHOTONIC MICROCAVITY 1D AND POROUS SILICON: In this chapter, we introduce photonic crystals from the concept to the structure of all 1D, 2D and 3D photonic crystals. Particularly, this chapter details the structure of the 1D photonic resonator and the formation of silicon by electrochemical etching method. The advantages of silicon and its application in the field of sensing are detailed in this chapter. Chapter 2: DESIGN AND SIMULATUION OF THE 1D MICROCAVITY STRUCTURES BASED ON POROUS SILICON This chapter describes the basic physics theory of one dimensional photonic crystals and the transmission of optical waves in layered media. The Kronig-Penny model is reviewed as a rigorous model for one dimensional periodically layered dielectric media. Next, the Transfer Matrix Method (TMM) is developed and its uses in calculating the band gaps of the non-defect PhCs and the reflection properties of defects introduced PhC structures are presented. This simulation work explored the effect of the refractive indices variation, the thickness of each layer and the number of layers on the formation of band gaps and on resonant transmissions in 1-D PhC microcavities. The obtained band gap was compared with the 6 simulation result based on the Kronig-Penny model, and the structure parameters defined from the simulated reflection spectra laid the foundation for the following fabrication work. Parameters affecting the sensitivity of the optical sensor based on the 1D microcavity structure on the silicon wafer are also detailed. Chapter 3: FABRICATION OF THE 1D – MICROCAVITY BASED ON POROUS SILICON 3.1. Principle, process of fabrication of the 1D microcavity based on porous silicon 3.1.1. Fabricating principles This part introduces the principle of fabricating 1D microcavity based on porous silicon by using electrochemical etching method. 3.1.2. Process of fabricating 1D microcavity structure This section details the steps of fabrication of 1D microcavity structure. 3.2. Design and fabrication of 1D microcavity structure The microcavity structure consists of two parallel reflectors separated by a spacer layer. Usually the reflectors used are λ/4 DBR with optical thickness of the layers λ/4. The optical thickness of the spacer layer can be either λ or λ/2. Porous silicon microcavities are formed Figure 3.5. (a) Schematic illustration of microcavity structure represented by a half-wave optical thickness defect layer between two Bragg mirrors. The Bragg mirrors consist of alternating layers of high and low refractive index quarter-wave optical thickness layers. (b) Reflectance spectrum of microcavity. The defect layer introduces a narrow resonance in the middle of the high reflectance stopband. 7 by first etching a top Bragg mirror with alternating quarter wavelength optical thickness layers of low and high porosities (high and low refractivve indices, respectively), then etching a half wavelength optical thickness defect layer with the same refractive index as the high porosity mirror layers, and finally etching a bottom Bragg mirror with the same conditions as the top mirror. Detailed electrochemical etching conditions are provided in Table 3.1. The characteristics of the microcavitity structures were determined by field-emission scanning electron microscopy (FE-SEM; S-4800) and the reflectance spectra of samples were studies by a UV-VIS- NIR spectrophotometer (Varian Cary-5000) and USB 4000 spectrophotometer. 3.3. Some methods of studying the structure and optical properties of porous silicon materials The optical properties and quality of the 1D photonic resonator structure depend greatly on the size of the porous holes, the thickness of the layers. Therefore, the identification of these factors is of particular importance in understanding the relationship between the structure and optical characteristics of microcavites made of silicon. In this section, we present some of the methods used in this thesis to observe the morphology, size, structure and optical characteristics of 1D microvities such as scanning electron microscopy SEM, Metricon Prism 2010 Model, Varian Carry 5000 Spectrum Analyzer, USB 4000 3.4. The 1D microcavity structures Table 3.3. Parameters of fabrication of 1D-PCs structure in visible range with 12 periods 8 Sample Layers Periods Current Density (mA/cm2) Time (s) M03 nH 12 15 4,47 nL 50 2,3 Figure 3.18 shows FE- SEM images of the 1D-PC in the visible range with 12 periods. Figure 3.19 presents the reflection spectra of 1D-PC structure in visible range. Detailed electrochemical etching conditions of microcavity structure in visible range. are provided in Table 3.4. The porous silicon microcavities used in this thesis typically consist of 4.5/5 period upper/lower Bragg mirrors. Each period consists of one low porosity and one high porosity layer. Therefore, a half period means that there is an additional low porosity layer formed. Increasing the naumber of mirror periods enables higher Q- factor microcavities. Figure 3.18. FE-SEM images of the 1D-PC in the visible range with 12 periods Hình 3.19. The reflection spectra of 1D-PC structure in visible range at 608 nm centre wavelength. 9 Bảng 3.4. Electrochemical etching conditions for a porous silicon microcavity at 650 nm resonant wavelength Descriptionả Period Current density (mA/cm2) Etching time (s) DBR1 4 15 5,16 50 2,65 1 15 5,16 Spacer layer 1 50 5,31 DBR2 5 15 5,16 50 2,65 Figure 3.20 shows cross-section and plan- view images of the microcavity based on (HL)4.5LL(HL)5 porous silicon multilayer structure, where H and L labels correspond to Figure 3.20. (a) Cross-section and (b) SEM plan-view images of a porous silicon microcavity design in the (HL)4.5LL(HL)5. Figure 3.23. 04 samples of microcavity structure in the visible range Figure 3.23. The reflection spectrum of 1D microcavity structure at 654 nm resonant wavelength. 10 high and low refractive index layers, respectively, 4.5 and 5.0 mean four and half and five pairs of HL, because this gives a good reflectivity spectrum, possibly controlling the porosity of layers, and easily repeatable electrochemical etching method. Figure 3.23 presents images of 4 microcavity structure samples in the visible range. 3.5. Design of photonic sensor device based on 1D-porous silicon microcavity Figure 3.34 is a block diagram of a photonic sensor device used in a thesis including a liquid method (application of non-volatile analytical substance) and vapor organic compounds (application for volatile compounds). Hình 3.23. Phổ phản xạ của cấu trúc vi cộng hưởng quang tử 1D sau khi chia cho cường độ phản xạ của mẫu nền. Figure 3.26. The schematic of photonic sensor device Figure 3.27. Schematic of the pesticide concentration measurement by liquid-drop method using the porous silicon microcavity sensor. Figure 3.28. Schematic of the concentration measurement for VOC using a sensor based on the porous silicon microcavity 11 Chapter 4: DETERMINATION OF PESTICIDE RESIDUES IN AQUATIC ENVIRONMENT BASED ON POROUS SILICON MICROCAVITIES 4.1. Principle of optical sensing Principle of interferometric transduction is used, in which the molecular recognition events are converted into optical signals via the change of the refractive index. As shown in the schematic diagram (Fig. 4.1), light reflected from the top interface (air-PS) and bottom interface (PS-Si substrate) interfere with Figure 3.33. Overall drawing of equipment and sensor systems Figure 4.1. Schematic Diagram of Sensor Principle Figure 4.2. Wavelength shift in the reflectance spectra of sensor device before and after analyte substance absorption Figure 3.29. The image of photonic sensor device 12 each other and form the typical Fabry-Perot fringes i