Mønster via optisk mættede Transitions - fremstilling og 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
Optisk litografi er af afgørende betydning i fremstillingen af nanoskala strukturer og enheder. Øget fremskridt i nye litografiteknikker har evnen til at gøre det muligt for nye generationer af nye enheder. 8-11 i denne artikel, en gennemgang præsenteres af en klasse af optiske litografiske teknikker, som opnår dyb sub-bølgelængde opløsning ved hjælp af nye photoswitchable molekyler. Denne tilgang kaldes mønster via optisk umættet Overgange (POST). 1-3
POST er en hidtil ukendt nanofabrikation teknik, der unikt kombinerer ideer mætte optiske overgange i fotokrome molekyler, især (1,2-bis (5,5'-dimethyl-2,2'-bithiophen-yl)) perfluorocyclopent-1-en. I daglig tale er dette stof kaldet BTE, figur 1, såsom dem, der anvendes i en stimuleret emission-depletion (STED) mikroskopi 12, med litografi interferens, hvilket gør det et stærkt værktøj til large-område parallel nanopatterning af dybe subwavelength funktioner på en række forskellige overflader med potentiel udvidelse til 2- og 3-dimensioner.
Det fotokrome lag er oprindeligt i en homogen tilstand. Når dette lag er udsat for en ensartet belysning af λ 1, den omdannes til den anden isomer tilstand (1c), figur 2. Derefter prøven udsættes for en fokuseret knudepunkt ved λ 2, som omdanner prøven i den første isomere tilstand ( 1o) overalt, undtagen i umiddelbar nærhed af knudepunktet. Ved at styre dosis eksponering kan størrelsen af den uomdannede region gøres vilkårligt lille. En efterfølgende fastsættelse trin af en af isomererne kan være selektivt og irreversibelt konverteres (låst) i en 3 rd tilstand (i sort) for at låse mønster. Dernæst laget udsættes ensartet for λ 1, som konverterer alt undtagen den låste region tilbage til den oprindelige tilstand. Densekvens af trin kan gentages med en forskydning af prøven i forhold til optikken, hvilket resulterer i to låste regioner, hvis afstand er mindre end fjernfelts diffraktion grænsen. Derfor kan enhver vilkårlig geometri være mønstret i en "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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