Tuesday, November 6th at 16.00Aula Seminari di Fisica Teorica 2nd floor

Michal Kolar
(Department of Optics Palacky University)

“Orbital angular momentum single photon interferometry with which-path detection”

Abstract

We suggest to use linearly polarized photons with nonzero orbital angular momentum as an input of a Mach-Zehnder interferometer. By means of Dove prism and half-wave plate, we rotate the transverse field profile. Due to this rotation we observe the non-sinusoidal interferometric pattern. For certain phase differences, we have both reliable which-path information stored in the polarization state and high phase-sensitivity of the pattern. We disscus the interesting connection of our scheme to the wave-particle duality of the photon.

Mercoledì 7 novembre 2007 alle ore 15.00
Aula n. 21
Francesco Stellacci
Department of Materials Science and Engineering, Massachusetts
Institute of Technology, Cambridge, - USA

“Supramolecular Nanomaterials and Lithography”

Abstract:
It is know that specific molecules can spontaneously arrange on various surfaces forming two-dimensional poly-crystalline mono-molecular layers called self-assembled monolayers (SAMs). These organic coatings are used to impart targeted optical, electronic and biological properties to surfaces. Very often SAMs composed of more than one type of molecule (mixed-SAMs) are used to simultaneously impart multiple properties. Scanning tunneling microscopy (STM) studies have shown that, in mixed SAMs, molecules phase-separate in domains of random shape and size.
We will show that when mixed SAMs are formed on surfaces with a radius of curvature smaller than 20 nm they spontaneously phase-separate in highly ordered phases of unprecedented size. The reason for this supramolecular phenomenon is purely topological and can be rationalized through the “ha iry ball theorem”. In the specific case of mixed SAMs formed on the surface of gold nanoparticles, the molecular ligands separate into 5 Å wide phases of alternating composition that encircle or spiral around the particle metallic core. This new family of nano-structured nano-materials¹ shows new properties solely due to this novel and unique morphology. For example, the particles’ solubility starts to depend on the ratio between the dimensions of the phases and that of the solvent molecules. More importantly, due to the ordered alternation of 5 Å wide hydrophobic and hydrophilic regions, surfaces coated with these particles show the ability of suppressing protein nonspecific adsorption, outperforming poly-ethylene glycol (PEG) the golden standard in this field.
Additionally, we will show how patterned DNA SAMs can be used as masters for a novel printing technique for organic materials called Supramolecular NanoStamping (SuNs). This method, like the DNA/RNA information transfer, uses the reversible assembly of DNA double strands as a way of transferring patterns from a surface to another. One of the main advantages of SuNs is that multiple DNA strands (each encoding different information) can be printed at the same time, thus allowing for a complex chemical pattern to be formed, much like Gutenberg movable type. The parallel printing of a pattern formed by multiple DNA strands will be presented.

R. Checchetto

P. Faccioli

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Mi contatti. Per ora sono sufficienti 4-5 persone e sceglierò io in base alla disponibilità e a quanto le conosco.

Ciao Matteo

I transistor ad effetto di campo stanno emergendo come dispositivi utili per un’ efficiente generazione di luce da una varietà di materiali, inclusi i semiconduttori inorganici, i nanotubi di carbonio e i film sottili organici. I transistor organici ad effetto di campo emettitori di luce (OLET) sono una nuova classe di dispositivi elettro-ottici [1] che potrebbero consentire di comprendere più approfonditamente fenomeni di base dell’optoelettronica organica come l’iniezione di carica, la ricombinazione di carica e l’emissione di luce. Questi dispositivi possono trovare potenziali applicazioni in sistemi per la comunicazione ottica, nella tecnologia display avanzata, nell’illuminazione a stato solido, nei laser organici pompati elettricamente e nei sensori. Il meccanismo di funzionamento dei transistor emettitori di luce basati su film sottili organici verrà discusso e confrontato con quanto avviene nella ben nota architettura verticale degli OLED. Le proprietà fondamentali dei materiali quali la mobilità ad effetto di campo, l’efficienza di emissione e le condizioni di crescita determinano sia le caratteristiche che le prestazioni del dispositivo finale. I recenti avanzamenti e le prospettive future degli OLETs sono analizzate ponendo particolare enfasi sui semiconduttori organici e sul ruolo giocato dalla struttura dello strato attivo [2] e dalle proprietà dei materiali [3] nel determinare la risposta dei dispositivi.
[1] M. Muccini, A bright future for organic field-effect transistors NATURE MATERIALS 5 (2006) 605
[2] M.A. Loi, et al., Supramolecular organization in ultra-thin films of a-sexithiophene on silicon dioxide NATURE MATERIALS 4 (2005) 81
[3] E. Da Como, et al., J-Aggregation in a-sexithiophene submonolayer films on silicon dioxide
JOURNAL OF THE AMERICAL CHEMICAL SOCIETY 128 (2006) 4277

Mercoledì 31 ottobre 2007 alle ore 15.00

Aula n. 21

R. Checchetto

P. Faccioli

Friday, October 26 at 11 a.m.
Sala Conferenze Edificio Ovest
FBK-irst

Abstract
In this talk I will present our research activity in the area of nanofabrication. I will review our work in the area of semiconductor lithography, showing the design and performance of our Extreme Ultraviolet Interference Lithography and Holography (EUV-IL and HL) setup operating at _ = 13.4 nm. This activity is geared to support the development of novel photoresist materials for the 50-10 nm domain lithography nodes of the ITRS. Many aspects of image formation involving EUV are still poorly understood, and in addition to the experimental work we have also developed an extensive set of simulation tools to model the image formation from aerial image to resist developed image. In particular, we include explicitly stochastic effects to model the Line Edge Roughness that affects severely the ability of current processes to pattern reliably below 50nm. Since EUV-IL generates patterns limited to periodic structures, we have also extended the application of holography to the EUV spectral range using Computer Generated Holograms (CGH) for arbitrary image synthesis; these holograms are particularly challenging to manufacture for use in the EUV because of the poor optical quality of the materials in that photon energy range. It is a truism to say that lithographic patterning is an essential part of any form of fabrication process involving semiconductor technology. Interestingly, in recent years lithography has been extended to biological problems. A classical example is the activity at Affymetrix, where DNA microarrays are synthesized using a combinatorial sequence of exposures to yield “chips” with hundreds of thousands of pixels, each one corresponding to a unique oligomer sequence. These “Gene chips” are widely used in genomic research. The process has been further extended by our introduction of the “Maskless Array Synthesizer”, or MAS, in 2000. The MAS is commercialized today by NimbleGen-Roche for the rapid turnaround production of custom sequences of high density chips. The application of lithographic techniques to biological problem does not stop with DNA microarrays. We are developing a “gene synthesis” process whereby the oligomers synthesized on-chip are harvested from the surface, amplified and stepwise assembled in longer constructs. These “synthetic genes” can be used to encode biological functions, or to enable the use of DNA as structural material. I firmly believe that the combination of high-resolution patterning (e.g., by E-beam lithography of functionalized surfaces) with on-demand synthesis of DNA (and other molecules) is paving the way to completely new applications. Thus, in summarizing my talk, I will put in context the merger of nanolithography (as a top-down technique) with DNA and other molecular synthesis (as a bottom up technique).