Patroonvorming via Optical Verzadigbare Transitions - fabricage en karakterisering
Summary
We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.
Abstract
This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.
Introduction
Optische lithografie is van essentieel belang in de fabricage van structuren op nanoschaal en apparaten. Toegenomen ontwikkelingen in de roman van lithografie technieken heeft de mogelijkheid om nieuwe generaties van nieuwe apparaten. 8-11 In dit artikel wordt een overzicht gepresenteerd van een klasse van optische lithografische technieken die diepe sub-golflengte resolutie met behulp van nieuwe photoswitchable moleculen te bereiken. Deze aanpak wordt genoemd Patterning via Optical-Verzadigbare Transitions (POST). 1-3
POST is een nieuwe nanofabricatie techniek die op unieke wijze de ideeën verzadigen optische overgangen van fotochrome moleculen, in het bijzonder (1,2-bis (5,5'-dimethyl-2,2'-bithiophen-yl)) perfluorocyclopent-1-een. Gemeenzaam, wordt deze verbinding genoemd BTE figuur 1, zoals die in gestimuleerde emissie-depletie (STED) microscopie 12, interferentie lithografie, waardoor het een krachtig hulpmiddel voor larg maakte-gebied parallel nanopatronen van diepe subwavelength functies op een verscheidenheid van oppervlakken met een mogelijke uitbreiding tot 2- en 3-dimensies.
De meekleurende laag is oorspronkelijk in een homogene toestand. Wanneer deze laag wordt blootgesteld aan een gelijkmatige verlichting van λ 1 het omzet in de tweede isomere toestand (1c), figuur 2. Vervolgens wordt het monster blootgesteld aan een gerichte knooppunt λ 2, waarbij het monster in de eerste isomere toestand (converteert 1o) overal behalve in de directe omgeving van het knooppunt. Door het regelen van de dosis belichting kan de afmeting van de omgezette gebied worden willekeurig klein. Een volgende stap bevestiging van een van de isomeren selectief en irreversibel worden omgezet (vergrendeld) in een 3e toestand (in zwart) om het patroon te vergrendelen. Vervolgens wordt de laag gelijkmatig blootgesteld aan λ 1, die alles behalve de vergrendelde regio zet terug naar de oorspronkelijke staat. Dereeks stappen kunnen worden herhaald met een verplaatsing van het monster ten opzichte van de optiek, resulterend in twee afgesloten gebieden waarvan de afstand kleiner is dan het verre veld diffractiegrens. Derhalve kan elke willekeurige geometrie worden gevormd in een "dot matrix" mode. 1-3
Protocol
Representative Results
Discussion
The fabrication, experimental setup and related operational procedures of Patterning via Optical Saturable Transitions (POST) have been described. By exploiting the linear switching properties of thermally stable photochromic molecules, POST offers new perspectives on circumventing the far-field diffraction limit.1-2,4
Previously long-term storage requirement of the samples was solved by storing the samples under N2, directly after the initial evaporation.2 How…
Disclosures
The authors have nothing to disclose.
Acknowledgements
Thanks to Michael Knutson, Paul Hamric, Greg Scott, and Chris Landes for helpful discussions and assistance related to the custom inert atmosphere sample holder and assistance in the University of Utah student machine shop. P.C. acknowledges the NSF GRFP under Grant No. 0750758. P.C. acknowledges the University of Utah Nanotechnology Training Fellowship. R.M. acknowledges a NSF CAREER Award No. 1054899 and funding from the USTAR Initiative.
Materials
| Name of Material/ Equipment | Company | Catalog Number | Comments/Description |
| Isopropanol | Fisher Scientific | P/7500/15 | CAUTION: flammable, use good ventilation and avoid all ignition sources. |
| Buffered Oxide Etch | |||
| Methanol | Ricca Chemical | 48-293-2 | CAUTION: flammable, use good ventilation and avoid all ignition sources. |
| Ethylene Glycol | Sigma-Aldrich | 324558 | CAUTION: Harmful if swallowed |
| Silicon wafer | |||
| Diamond Scribe | |||
| Glass Beakers | |||
| Tweezers | Ted Pella | 5226 | |
| Reactive Ion Etching System | Oxford | Plasma Lab 80 Plus | |
| Inert Atmosphere Sample Holder | Proprietary In-house Designed | ||
| Polarizing beamsplitter cube | Thorlabs | PBS052 | |
| HeNe Laser | Melles Griot | 25-LHP-171 | CAUTION: Wear safety glasses |
| Half-wave plates | Thorlabs | WPH05M-633 | |
| Thermal Evaporator | Proprietary In-house Designed | ||
| TMV Super | TM Vacuum Products | TMV Super | |
| Voltammograph | Bioanalytical Systems | CV-37 | |
| Shortwave UV lamp 365nm | UVP Analytik Jena Company | UVGL-25 | CAUTION: Wear UV safety glasses |
References
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