Patterning via ópticos de saturação Transitions - Fabricação e caracterização
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
Litografia óptica é de importância fundamental na fabricação de estruturas e dispositivos em nanoescala. Aumento dos avanços nas técnicas de litografia romance tem a capacidade de ativar novas gerações de novos dispositivos. 8-11 Neste artigo, é apresentada uma revisão de uma classe de técnicas de litografia óptica que atingem resolução sub-comprimento de onda de profundidade, usando moléculas foto induzida novos. Esta abordagem é chamada Patterning via Optical-saturado Transitions (POST) 1-3.
POST é uma técnica utilizada nanofabrication que combina exclusivamente as ideias de saturação transições ópticas de moléculas fotossensíveis, especificamente (1,2-bis (5,5'-dimetil-2,2'-bitiofen-il)) perfluorocyclopent-1-eno. Coloquialmente, este composto é referido como BTE, Figura 1, tais como aqueles utilizados na emissão de depleção (STED) microscopia estimulada 12, com interferência de litografia, o que o torna uma ferramenta poderosa para large-área microusinagem paralelo de características subwavelength profundos sobre uma variedade de superfícies de extensão com potencial para 2- e 3-dimensões.
A camada fotossensível é originalmente em um estado homogêneo. Quando esta camada é exposta a uma iluminação uniforme de λ 1, que converte para o segundo estado isomérico (1c), Figura 2. Em seguida, a amostra é exposta a um nó focado no λ 2, que converte a amostra para o primeiro estado isomérico ( 1o) em todos os lugares, exceto nas proximidades do nó. Através do controlo da dose de exposição, o tamanho da região não convertido pode ser feita arbitrariamente pequena. Um passo subsequente fixação de um dos isómeros pode ser selectivamente e irreversivelmente convertidas (bloqueado) em um estado 3 rd (a preto) para bloquear o padrão. Em seguida, a camada é exposto uniformemente a λ 1, que converte a tudo com excepção da região bloqueado volta ao seu estado original. Osequência de passos podem ser repetidos com um deslocamento de amostra em relação ao sistema óptico, o que resulta em duas regiões bloqueadas cujo espaçamento é menor do que o limite de difracção de campo distante. Portanto, qualquer geometria arbitrária pode ser modelado em uma forma "dot-matrix" 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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