Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array

With the challenge of obtaining high resolution three-dimensional images of nanostructures over large areas as well as fabricating these nanostructures in a low-cost manner, developing cost-effective strategies which enable high-resolution, large-area nanostructures imaging as well as fabri...

Full description

Saved in:
Bibliographic Details
Main Author: Wu, Jin
Other Authors: Huo Fengwei
Format: Theses and Dissertations
Language:English
Published: 2015
Subjects:
Online Access:http://hdl.handle.net/10356/65295
Tags: Add Tag
No Tags, Be the first to tag this record!
Institution: Nanyang Technological University
Language: English
id sg-ntu-dr.10356-65295
record_format dspace
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Materials
spellingShingle DRNTU::Engineering::Materials
Wu, Jin
Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array
description With the challenge of obtaining high resolution three-dimensional images of nanostructures over large areas as well as fabricating these nanostructures in a low-cost manner, developing cost-effective strategies which enable high-resolution, large-area nanostructures imaging as well as fabrication is a long standing goal in nanotechnology community. In this thesis, a pristine or modified polydimethylsiloxane (PDMS) tip array consisting of thousands of nanotips was utilized to address the above challenge. The first part of the dissertation explored a new optical microscopy which enables the measurement of topography and chemical properties of sample surfaces by taking advantage of the interaction between a transparent and elastomeric tip array and underlying surfaces. Since the reflected light intensity at the apexes of nanotips changed significantly when the soft probes contact and separate with underlying sample surfaces, the exact contact and separation positions in the vertical direction can be precisely determined and therefore used for measuring the feature height. This imaging method has never been reported before. One remarkable advantage of parallel scanning optical microscopy (PSOM) is the multiple tip nature. As hundreds of nanotips scan at different places on the underlying surface simultaneously, the image covering the areas of square millimeter scale could be obtained in just one run with sub-diffraction vertical resolution. Currently, the feature height down to 35 nm can be measured by PSOM, which has broken the diffraction limit in the vertical direction. Three-dimensional topographical image covering the surface area of 0.15 mm? was acquired by using 91 tips parallel scanning. The adhesive force between tips and chemically modified surfaces during the separation process can be detected. Based on this, the hydrophilic and hydrophobic surfaces can be differentiated by this tip array. This potentially enables the probes to map the spatial distribution of different functional groups on the surfaces. The application of low-cost PDMS tips as the scanning probes and utilization of white light intensity change as the feedback impart the cost-effective and simple characteristics toPSOM. The second part of the thesis explored near-field photolithography approaches allowing for nanoscale sub-diffraction nanostructure fabrication over large areas on surfaces in a low-cost manner. In this work, pristine and metal-coated PDMS nanostructures were used as the photomasks to produce wafer-scale sub-diffraction nanostructures via near-field photolithography. The PDMS based photomasks gain the merits of low-cost, easy fabrication, ease-of-use, repeatedly usage. Since the elastomeric PDMS nanostructures can contact with underlying surfaces intimately, which enables the incident light to expose underlying photoresist in the optical near-field, the diffraction limit has been circumvented and therefore sub-diffraction nanostructures can be produced. The following three types of near-field photolithography strategies were developed in this work. Firstly, wafer-scale sub-IOO nm near-field photolithography strategy with metal-coated elastomeric masks was developed. The incident light was strictly allowed to pass from the nanoscopic apertures at the apexes of tips to expose underlying photoresist, producing sub-IOO nm features over wafer-scale areas based on common mask aligner patterning platform. Secondly, a centimeter-scale sub-IOO nm near-field photolithography strategy with light leaking photomasks was developed. By using electron-beam evaporation to evaporate metals towards the PDMS relief nanostructures of vertical side walls with controlled evaporation direction, two-side or one-side nanoscopic apertures at the side walls were produced straightforwardly. Through the apertures, the incident passed to expose underlying photoresist at nanoscale areas. This facile near-field photolithography strategy bypassed the complicated procedures of creating nanoscopic apertures after metal-coating, while possessed the capability of producing sub-lOf nm features with arbitrary shapes. Thirdly, wafer-scale sub-LOu nm near-field photolithography by usmg V-shape transparent and elastomeric nanotip array as photomasks was developed. Rather than utilize opaque metal layer coating to fabricate the photomasks, herein, the V-shape total reflective PDMS nanostructures were used as the light intensity modulator. Only the photoresist at the nanoscale contact areas between the apexes of tips and surfaces was allowed to be exposed completely, generating sub-l Of nm nanopattems over wafer-scale areas. At last, a facile method was developed to synthesize large-area single sub-la nm nanoparticle array in-situ by polymer pen lithography (PPL). Herein, small molecules such as ethylene glycol (EG) or glycerol were utilized to facilitate the delivery of nanoparticle precursors to the substrates in polymer pen lithography. Subsequently, large-area ordered single nanoparticle arrays including sub-la nm Ag nanoparticle, 30 nm Au nanoparticle and 80 nm Fe203 nanoparticle have been synthesized in-situ with controllable size and pitches.
author2 Huo Fengwei
author_facet Huo Fengwei
Wu, Jin
format Theses and Dissertations
author Wu, Jin
author_sort Wu, Jin
title Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array
title_short Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array
title_full Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array
title_fullStr Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array
title_full_unstemmed Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array
title_sort large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (pdms) nanotip array
publishDate 2015
url http://hdl.handle.net/10356/65295
_version_ 1759852934675300352
spelling sg-ntu-dr.10356-652952023-03-04T16:33:35Z Large-area three-dimensional optical imaging and subdiffraction photolithography with polydimethylsiloxane (PDMS) nanotip array Wu, Jin Huo Fengwei School of Materials Science & Engineering DRNTU::Engineering::Materials With the challenge of obtaining high resolution three-dimensional images of nanostructures over large areas as well as fabricating these nanostructures in a low-cost manner, developing cost-effective strategies which enable high-resolution, large-area nanostructures imaging as well as fabrication is a long standing goal in nanotechnology community. In this thesis, a pristine or modified polydimethylsiloxane (PDMS) tip array consisting of thousands of nanotips was utilized to address the above challenge. The first part of the dissertation explored a new optical microscopy which enables the measurement of topography and chemical properties of sample surfaces by taking advantage of the interaction between a transparent and elastomeric tip array and underlying surfaces. Since the reflected light intensity at the apexes of nanotips changed significantly when the soft probes contact and separate with underlying sample surfaces, the exact contact and separation positions in the vertical direction can be precisely determined and therefore used for measuring the feature height. This imaging method has never been reported before. One remarkable advantage of parallel scanning optical microscopy (PSOM) is the multiple tip nature. As hundreds of nanotips scan at different places on the underlying surface simultaneously, the image covering the areas of square millimeter scale could be obtained in just one run with sub-diffraction vertical resolution. Currently, the feature height down to 35 nm can be measured by PSOM, which has broken the diffraction limit in the vertical direction. Three-dimensional topographical image covering the surface area of 0.15 mm? was acquired by using 91 tips parallel scanning. The adhesive force between tips and chemically modified surfaces during the separation process can be detected. Based on this, the hydrophilic and hydrophobic surfaces can be differentiated by this tip array. This potentially enables the probes to map the spatial distribution of different functional groups on the surfaces. The application of low-cost PDMS tips as the scanning probes and utilization of white light intensity change as the feedback impart the cost-effective and simple characteristics toPSOM. The second part of the thesis explored near-field photolithography approaches allowing for nanoscale sub-diffraction nanostructure fabrication over large areas on surfaces in a low-cost manner. In this work, pristine and metal-coated PDMS nanostructures were used as the photomasks to produce wafer-scale sub-diffraction nanostructures via near-field photolithography. The PDMS based photomasks gain the merits of low-cost, easy fabrication, ease-of-use, repeatedly usage. Since the elastomeric PDMS nanostructures can contact with underlying surfaces intimately, which enables the incident light to expose underlying photoresist in the optical near-field, the diffraction limit has been circumvented and therefore sub-diffraction nanostructures can be produced. The following three types of near-field photolithography strategies were developed in this work. Firstly, wafer-scale sub-IOO nm near-field photolithography strategy with metal-coated elastomeric masks was developed. The incident light was strictly allowed to pass from the nanoscopic apertures at the apexes of tips to expose underlying photoresist, producing sub-IOO nm features over wafer-scale areas based on common mask aligner patterning platform. Secondly, a centimeter-scale sub-IOO nm near-field photolithography strategy with light leaking photomasks was developed. By using electron-beam evaporation to evaporate metals towards the PDMS relief nanostructures of vertical side walls with controlled evaporation direction, two-side or one-side nanoscopic apertures at the side walls were produced straightforwardly. Through the apertures, the incident passed to expose underlying photoresist at nanoscale areas. This facile near-field photolithography strategy bypassed the complicated procedures of creating nanoscopic apertures after metal-coating, while possessed the capability of producing sub-lOf nm features with arbitrary shapes. Thirdly, wafer-scale sub-LOu nm near-field photolithography by usmg V-shape transparent and elastomeric nanotip array as photomasks was developed. Rather than utilize opaque metal layer coating to fabricate the photomasks, herein, the V-shape total reflective PDMS nanostructures were used as the light intensity modulator. Only the photoresist at the nanoscale contact areas between the apexes of tips and surfaces was allowed to be exposed completely, generating sub-l Of nm nanopattems over wafer-scale areas. At last, a facile method was developed to synthesize large-area single sub-la nm nanoparticle array in-situ by polymer pen lithography (PPL). Herein, small molecules such as ethylene glycol (EG) or glycerol were utilized to facilitate the delivery of nanoparticle precursors to the substrates in polymer pen lithography. Subsequently, large-area ordered single nanoparticle arrays including sub-la nm Ag nanoparticle, 30 nm Au nanoparticle and 80 nm Fe203 nanoparticle have been synthesized in-situ with controllable size and pitches. Doctor of Philosophy (MSE) 2015-07-09T02:32:49Z 2015-07-09T02:32:49Z 2014 2014 Thesis http://hdl.handle.net/10356/65295 en 199 p. application/pdf