Patrones través ópticos saturable Transiciones - Fabricación y Caracterización
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
Litografía óptica es de importancia clave en la fabricación de estructuras a nanoescala y dispositivos. El aumento de los avances en las técnicas de litografía novela tiene la posibilidad de habilitar nuevas generaciones de dispositivos novedosos. 8-11 En este artículo, se presenta una revisión de una clase de técnicas litográficas ópticos que logran profundo resolución sub-banda de frecuencia con nuevas moléculas photoswitchable. Este enfoque se denomina Patterning vía óptica saturable Transitions (POST). 1-3
POST es una técnica novedosa nanofabricación que combina de forma única las ideas de la saturación de las transiciones ópticas de moléculas fotocrómicas, específicamente (1,2-bis (5,5'-dimetil-2,2'-bithiophen-il)) perfluorocyclopent-1-eno. Coloquialmente, este compuesto se conoce como BTE, la Figura 1, tales como los utilizados en la emisión-agotamiento (STED) microscopía estimulada 12, con litografía de interferencia, que hace que sea una herramienta poderosa para large-área nanoestampación paralelo de características de sublongitud de onda profundos sobre una variedad de superficies con extensión potencial de 2 y 3 dimensiones.
La capa fotocrómico es originalmente en un estado homogéneo. Cuando esta capa se expone a una iluminación uniforme de λ 1, se convierte en el segundo estado isomérico (1c), la Figura 2. A continuación, la muestra se expone a un nodo centrado en λ 2, que convierte la muestra en el primer estado isomérico ( 1o) en todas partes excepto en las inmediaciones del nodo. Mediante el control de la dosis de exposición, el tamaño de la región no convertida se puede hacer arbitrariamente pequeña. Una etapa de fijación posterior de uno de los isómeros se puede convertir selectiva e irreversible (bloqueado) en un estado 3 rd (en negro) para bloquear el patrón. A continuación, la capa se expone de manera uniforme a λ 1, que convierte todo excepto la región bloqueada de nuevo a su estado original. Lasecuencia de pasos se puede repetir con un desplazamiento de la muestra relativa a la óptica, resultando en dos regiones bloqueadas cuya distancia es menor que el límite de difracción de campo lejano. Por lo tanto, cualquier geometría arbitraria puede ser modelada de una manera "de matriz de puntos". 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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