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Silicon micro-structure and ZnO nanowire hierarchical assortments for light management
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.ORCID iD: 0000-0003-1806-9148
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.ORCID iD: 0000-0002-2069-2820
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2013 (English)In: Optical Materials Express, ISSN 2159-3930, Vol. 3, no 8, 1039-1048 p.Article in journal (Refereed) Published
Abstract [en]

We present fabrication and optical characterization of Si microstructure-ZnO nanowire (NWs) hierarchical structures for light management. Random and periodic hierarchical structures constituting Si micro pillar or micro pyramid arrays with overgrown ZnO NWs have been fabricated. Inexpensive colloidal lithography in combination with dry and wet chemical etching is used to fabricate Si microstructures, and ZnO NWs are grown by hydrothermal synthesis. The periodic Si micro pyramid-ZnO NWs hierarchical structure shows broadband antireflection with average reflectance as low as 2.5% in the 300-1000 nm wavelength range. A tenfold enhancement in Raman intensity is observed in this structure compared to planar Si sample. These hierarchical structures with enriched optical properties and high surface to volume ratio are promising for photovoltaic (PV) and sensor applications.

Place, publisher, year, edition, pages
2013. Vol. 3, no 8, 1039-1048 p.
Keyword [en]
Solar-Cells, Arrays, Nanostructures, Layers, Tmah, Koh
National Category
Nano Technology Atom and Molecular Physics and Optics
URN: urn:nbn:se:kth:diva-127416DOI: 10.1364/OME.3.001039ISI: 000322630100004ScopusID: 2-s2.0-84884197449OAI: diva2:644088
Swedish Research CouncilEU, FP7, Seventh Framework Programme

QC 20130902

Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2016-04-07Bibliographically approved
In thesis
1. Deterministic Silicon Pillar Assemblies and their Photonic Applications
Open this publication in new window or tab >>Deterministic Silicon Pillar Assemblies and their Photonic Applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is of paramount importance to our society that the environment, life style, science and amusement flourish together in a balanced way. Some trends in this direction are the increased utilization of renewable energy, like solar photovoltaics; better health care products, for example advanced biosensors; high definition TV or high resolution cameras; and novel scientific tools for better understanding of scientific observations. Advancement of micro and nanotechnologies has directly and positively impacted our stance in these application domains; one example is that of vertical periodic or aperiodic nano or micro pillar assemblies which have attracted significant research and industrial interest in recent years. In particular, Si pillars are very attractive due to the versatility of silicon. There are many potential applications of Si nanopillar/nanowire assemblies ranging from light emission, solar cells, antireflection, sensing and nonlinear optical effects. Compared to bulk, Si pillars or their assemblies have several unique properties, such as high surface to volume ratios, light localization, efficient light guiding, better light absorption, selective band of light propagation etc.

     The focus of the thesis is on the fabrication of Si pillar assemblies and hierarchical ZnO nanowires on Si micro structures in top-down and bottom-up approaches and their optical properties and different applications. Here, we have investigated periodic and aperiodic Si nano and micro structure assemblies and their properties, such as light propagation, localization, and selective guiding and light-matter interaction. These properties are exploited in a few important optoelectronic/photonic applications, such as optical biosensors, broad-band anti-reflection, radial-junction solar cells, second harmonic generation and color filters.  

      We achieved a low average reflectivity of ~ 2.5 % with the periodic Si micropyramid-ZnO NWs hierarchical arrays. Tenfold enhancement in Raman intensity is also observed in these structures compared to planar Si. These Si microstructure-ZnO NW hierarchical structures can enhance the performance and versatility of photovoltaic devices and optical sensors. A convenient top-down fabrication of radial junction nanopillar solar cell using spin-on doping and rapid thermal annealing process is presented. Broad band suppressed reflection, on average 5%, in 300- 850 nm wavelength range and an un-optimized cell efficiency of 6.2 % are achieved. Our method can lead to a simple and low cost process for high efficiency radial junction nanopillar solar cell fabrication.     

      Silicon dioxide (SiO2) coated silicon nanopillar (NP) arrays are demonstrated for surface sensitive optical biosensing. Bovine serum albumin (BSA)/anti-BSA model system is used for biosensing trials by photo-spectrometry in reflection mode. Best sensitivity in terms of limit of detection of 5.2 ng/ml is determined for our nanopillar biosensor. These results are promising for surface sensitive biosensors and the technology allows integration in the CMOS platform.  

      Si pillar arrays used for surface second harmonic generation (SHG) experiments are shown to have a strong dependence of the SHG intensity on the pillar geometry. The surface SHG can be suitable for nonlinear silicon photonics, surface/interface studies and optical sensing.  

      Aperiodic Si nanopillar assemblies in PDMS matrix are demonstrated for efficient color filtering in transmission mode. These assemblies are designed using the ‘‘molecular dynamics-collision between hard sphere’’ algorithm. The designed structure is modeled in a 3D finite difference time domain (FDTD) simulation tool for optimization of color filtering properties. Transverse localization effect of light in our nanopillar color filter structures is investigated theoretically and the results are very promising to achieve image sensors with high pixel densities (~1 µm) and low crosstalk. The developed color filter is applicable as a stand-alone filter for visible color in its present form and can be adapted for displays, imaging, smart windows and aesthetic applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xiii, 72 p.
TRITA-ICT/MAP, 2016:06
nanopillar, nanowires, nanophotonics, nanofabrication, silicon, photovoltaics, second-harmonic generation, top-down approach, colloidal lithography, color filter, biosensor
National Category
Physical Sciences
Research subject
Physics; Materials Science and Engineering
urn:nbn:se:kth:diva-184709 (URN)978-91-7595-891-0 (ISBN)
Public defence
2016-04-29, 208, Electrum, Isafjordsgata 22,Kista, Sweden, Stockholm, 10:00 (English)

QC 20160407

Available from: 2016-04-07 Created: 2016-04-04 Last updated: 2016-04-07Bibliographically approved

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Dev Choudhury, BikashAbedin, AhmadDev, ApurbaSanatinia, RezaAnand, Srinivasan
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