Metal Assisted Synthesis of Single Crystalline Silicon Nanowires At
Total Page：16
File Type：pdf, Size：1020Kb
dicine e & N om a n n a o t N e f c o h Md Asgar et al., J Nanomed Nanotechnol 2014, 5:4 l n Journal of a o n l o r g u DOI: 10.4172/2157-7439.1000221 y o J ISSN: 2157-7439 Nanomedicine & Nanotechnology Research Article Open Access Metal Assisted Synthesis of Single Crystalline Silicon Nanowires at Room Temperature for Photovoltaic Application Md Asgar A1, Hasan M2, Md Huq F3* and Zahid H Mahmood4 1Department of Electronics and Communication Engineering, Jatiya Kabi Kazi Nazrul Islam University, Trishal, Mymensingh, Bangladesh 2Department of Electrical and Electronic Engineering, Shahjalal University of Science and Technology, Kumargaon, Sylhet-3114, Bangladesh 3Department of Nuclear Engineering, University of Dhaka, Dhaka 1000, Bangladesh 4Department of Applied Physics Electronics and Communication Engineering, University of Dhaka, Dhaka-1000, Bangladesh Abstract Synthesis of single crystalline silicon nanowires (SiNWs) array at room temperature by metal assisted chemical etching and its optical absorption measurements have been reported in this article. It has been confirmed that, SiNWs were formed uniformly on p-type silicon substrate by electroless deposition of Cu and Ag nanoparticles followed by wet chemical etching in (Hydrogen Fluoride) HF based Fe(NO3)3 solution. Synthesized SiNW structures were analyzed and investigated by Scanning Electron Microscopy (SEM) and Ultraviolet-Visible (UV-VIS) spectrophotometer. Formation of SiNWs is evident from the SEM images and morphology of the structures depends upon the concentration of chemical solution and etching time. The synthesized SiNWs have shown strong broadband optical absorption exhibited from UV- spectroscopy. More than 82% absorption of incident radiation is found for Cu treated samples and a maximum of 83% absorption of incident radiation is measured for Ag synthesized samples which is considerably enhanced than that of silicon substrate as they absorbed maximum of 43% of incoming radiation only. Keywords: Silicon nanowires; Scanning electron microscopy; light trapping and as we have shown in this paper, high absorption Carbon nanotubes; Nanostructure arrays [31,32]. Introduction Herein, we have reported the room-temperature synthesis of highly oriented SiNWs array, using simple chemical technique named Research attention in semiconducting nanostructures has been Electroless Metal Deposition (EMD) and metal-assisted Electroless decoupled after successful synthesis of Carbon Nano-Tubes (CNTs), Etching (EE) of Si wafers in an aqueous HF solution containing Fe3+ for their novel size and dimensionality dependent physical properties ions. We have employed this method because it has several advantages [1,2]. To date, the most significant semiconducting material in over many other established methods. This technique is cost effective microelectronic industries is silicon (Si), owing to their technical and functions without requiring any vacuum and high temperature compatibility with existing semiconductor technology. Though silicon requirement. Growth of SiNWs by this technique is slightly depends cannot emit visible light as being an indirect material, low dimensional on the crystallographic orientation which makes them to utilize Si nanostructures yield visible light because of quantum confinement polycrystalline substrate [33]. This chemical electrolytic process is effect [3-5]. As a result, much effort has been made to prepare various based on a galvanic displacement reaction. In this method oxidization silicon nanostructures such as Silicon nanotubes, Silicon Nano-Cones of metal ions to metallic species such as particles and films, and the (SiNCs) and Silicon Nano-Wires (SiNWs) etc [6-9]. dissolution of silicon substrate occur extemporaneously on a silicon Silicon nanowires (SiNWs) have recently been the subject of great surface. scientific and technological interest by reason of their noble electrical After successful synthesis of Silicon nanowires (SiNWs) we have [10] optoelectronic [11], mechanical [12] and chemical properties investigated the optical behaviour of synthesized structures by means [13]. Several promising application of Si nanowires array are found of Ultraviolet-Visible (UV-VIS) spectroscopy. Silicon nanowire (SiNW) in different microelectronic industries, for instance, Field-Effect arrays synthesized by wet-chemical etching process have revealed very Transistors (FETs) [14,15], Single-Electron Transistors (SETs) [16], high absorption for a particular range of wavelength of electromagnetic inverters [17], photovoltaics and photodetectors [18], nanosensors spectrum. This high broadband optical absorption of SiNWs array [19,20], Light-Emitting Diodes (LEDs) and laser [14-21], decoder [22], makes them an important contestant for photovoltaic solar cell nonvolatile memory, programmable logic [23-25] and silicon nano- applications. anodes in practical lithium batteries [26] etc. Many other applications have been verified primarily in the form of individual nanowire devices, though some devices based on arrays have *Corresponding author: Md Huq F, Department of Nuclear Engineering, also been shown [27]. One feature that has been generally overlooked is University of Dhaka, Dhaka 1000, Bangladesh, Tel: 8801913377384; E-mail: [email protected] the interaction of light of varying wavelength with nanowire assemblies on p-type Si substrate, which may have implications for future optical Received April 26, 2014; Accepted August 20, 2014; Published August 27, 2014 and optoelectronic devices such as Laser, optical sensor [28]. and nano- Citation: Md Asgar A, Hasan M, Md Huq F, Mahmood ZH (2014) Metal Assisted photovoltaic solar cell [29]. The high aspect ratio of nanowires (typically Synthesis of Single Crystalline Silicon Nanowires at Room Temperature for on the order of 100 to 1000) and sharp dielectric contrast with its Photovoltaic Application. J Nanomed Nanotechnol 5: 221. doi: 10.4172/2157- 7439.1000221 surrounding (e.g. air or glass) lead to optical anisotropy as observed in individual silicon nanowires [30]. Moreover, sub-wavelength diameters Copyright: © 2014 Md Asgar A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits and proximity, combined with micron-scale lengths, may lead to unrestricted use, distribution, and reproduction in any medium, provided the interesting optical properties such as low reflectance through better original author and source are credited. J Nanomed Nanotechnol ISSN: 2157-7439 JNMNT, an open access journal Volume 5 • Issue 4 • 1000221 Citation: Md Asgar A, Hasan M, Md Huq F, Mahmood ZH (2014) Metal Assisted Synthesis of Single Crystalline Silicon Nanowires at Room Temperature for Photovoltaic Application. J Nanomed Nanotechnol 5: 221. doi: 10.4172/2157-7439.1000221 Page 2 of 7 Experimental Details Band (VB) of silicon and are deposited in the form of metallic silver nuclei. With the deposition and growth of silver nuclei, SiO2 is formed Preparation of 1D silicon nanostructures array was conducted in simultaneously underneath the silver nanoparticles (Illustrated in Figure Teflon lined stainless steel vessel. The fabrication process comprised of 1a and b). As the SiO2 underneath the silver nanoparticles is etched three steps. The first step is cleaning of the silicon wafers with cleaning away as by HF, then pits are formed immediately at the same location solution— here we sequentially used acetone (5 min), ethanol (5 min), (Illustrated in Figure 1c), so the silver nanoparticles sink into the pits as deionized water (2-3 times), and H SO /H O (3:1 H SO (97%)/ H O 2 4 2 2 2 4 2 2 they are formed. This is consistent with our SEM observations, which (30%), 10 min), then the wafers are thoroughly rinsed with deionized confirmed that the oxidation and dissolution of the silicon substrate water (10 min) and dip into a solution of HF (1 min). The second step occur from beneath the metal deposits. In the solution of HF/Fe(NO3)3, of fabrication is electroplating the metal-nanoparticle films onto the the redox level of the Fe3+/ Fe2+ system lies well below the VB of silicon, cleaned silicon surface. A group of cleaned samples were dipped in HF/ so active kinetics are expected for the electron-capture process from AgNO solution for Silver nanoparticle deposition. Deposition time 3 the VB bonding electrons. However, in contrary to fast reduction of was varied from 60 seconds to 75 seconds. The concentration of HF and Ag+ ions, reduction of Fe3+ ions and oxidation of silicon proceed very AgNO were 5 M and 0.02 M respectively. Another group of samples 3 slowly on the silicon surface in the absence of silver nanoparticles. were dipped in HF/Cu(NO ) .H O for copper nanoparticles deposition. 3 2 2 When the silicon surface is covered with silver nanoparticles, reduction In this case, deposition time was varied from 60 seconds to 120 of Fe3+ ions and oxidation of silicon are greatly enhanced. It is generally seconds. The concentration of HF was 5 M, whereas for Cu(NO ) .H O, 3 2 2 believed that metal nanoparticles adhered on a silicon surface have a it was varied from 0.02 M to 0.05 M. All the above mentioned chemical higher electronegativity than silicon, so they could attract electrons processes performed in Teflon beaker. After deposition of silver/copper from silicon to become negatively charged. These metal nanoparticles nanoparticles, the silver/copper deposited substrate was immersed in another solution for etching of uncovered areas of the silicon substrate.