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Capillary condensation in nanostructured surfaces
Full text linkThe subject of this thesis is the study of the capillary condensation phenomenon in
nanostructured surfaces. The main motivation behind this work was to test recent
scaling theories about the capillary filling in capped capillaries. Adsorption isotherms
of Argon were measured at a temperature slightly above its triple-point with a torsional
microbalance. A key element for this kind of experiments was the availability
of surfaces patterned with an array of very regular structures (e.g. rectangular wells
or cylindrical holes). To fabricate these substrates was fundamental to develop a new
fabrication methodology based on advanced lithographic techniques. The optimized
methodology relied on nanoimprint lithography (NIL), wet etching (Buffered Oxide
Etch solution) and plasma etching in an Inductively Coupled Plasma (ICP). With our
process we were able to pattern extended surface areas of about 1 cm2 with a regular
array of rectangular channels or hemispherical holes of nanometric size. In particular,
we realized channels of two different widths (90 and 200 nm) and characteristic depths
varying from 0.5 to 2 μm. Adsorption isotherms taken with these samples showed
sharp and reversible jumps related to the capillary condensation of liquid argon in the
channels. Their location was found to vary with the channel width, wider channels displaying
the transition closer to bulk liquid-vapor condensation. A quantitative analysis
of these positions in terms of the classical Kelvin equations yielded results which were
in good agreement with the sample morphology deduced by electron microscopy. The
precise shape of the capillary rise is currently under investigation to check whether
it confirms the scaling predictions. The fabrication of the samples has been realized
in the TASC-INFM Laboratory in Trieste under the supervising of Dr. Massimo Tormen,
whereas the measurement runs of adsorption isotherms were carried out in the
laboratory of Prof. Giampaolo Mistura in Padova.Il tema di questa tesi è lo studio dello studio dei fenomeni di condensazione capillare
in superfici nano strutturate. La motivazione principale a sostegno di questo lavoro
è la verifica di recenti teorie che descrivono il riempimento di capillari chiusi ad una
estremità. Le isoterme di assorbimento dell’argon sono state misurate a temperature
leggermente superiori al suo punto triplo con l’uso di una micro bilancia torsionale.
Un elemento chiave per questo tipo di esperimenti è la disponibilità di superfici strutturate
con una distribuzione periodica di elementi regolari (ad esempio canali rettangolari
o cavità cilindriche). Per costruire substrati di questo genere, è stato necessario
sviluppare una metodologia fabbricativa innovativa, basata su tecniche di litografia
avanzata. La metodologia ottimizzata si basa sulla cosiddetta nanoimprint lithography
(NIL), su etching in ambiente liquido (uso di soluzioni BOE per l’etching di ossido
di silicio) ed etching con uso di plasma gassosi in macchine di tipo ICP (Inductively
Coupled Plasma). Con il nostro processo siamo in grado di strutturare superfici con
area di estensione fino a 1 cm2 con distribuzione regolare di canali a sezione rettangolare
o cavità di forma emisferica, entrambi con dimensioni caratteristiche nel range
dei nanometri. In particolare abbiamo realizzato canali di due differenti larghezze (90
e 200 nm) e profondità caratteristica variabile tra 0:5 e 2 μm. Isoterme di adsorbimento
misurate con questo tipo di campioni mostrano transizioni nette e reversibili
correlabili con la condensazione capillare di argon liquido. La posizione di queste
transizioni varia col variare della larghezza dei canali: canali più larghi evidenziano
una transizione più vicina alla condensazione liquido-vapore in fase bulk. L’analisi
quantitativa di questi risultati, in termini della classica equazione di Kelvin, mostra
previsioni in buon accordo con la caratterizzazione diretta dei campioni tramite immagini
al SEM. La definizione precisa del profilo della parete del canale è ancora sotto
analisi per la conferma delle previsioni teoriche. La fabbricazione dei campioni è stata
condotta presso il laboratorio nazionale TASC-INFM in Trieste sotto la supervisione
del Dr. Massimo Tormen, mentre la misurazione delle isoterme di adsorbimento è stata
condotta nel laboratorio del Prof. Giampaolo Mistura all’Università di Padov
Sub-100 μs nanoimprint lithography at wafer scale
No full textDisplay Omitted A full 4¿ wafer is nanopatterned by an ultrafast thermal NIL process in 100μs.Stamps with integrated heater enable ultrafast cycles at very high temperature.The thermal cycle is implemented with a single short very intense current pulse.A new tool for the ultrafast NIL (or pulsed-NIL) process has been developed.The process applies to a wide range of thermoplastic materials. We present here an ultrafast thermal NIL technology, which enables the patterning of full wafers on the 100μs time-scale. This technique makes use of stamps with a heating layer integrated beneath their nanostructured surfaces. Injecting a single, short (<100μs), intense current pulse into the heating layer causes the surface temperature of the stamp to raise suddenly by hundreds of degrees¿C, resulting in the melting of the thermoplastic resist film pressed against it and the swift indentation of the nanostructures. This paper introduces the main aspects of this technology, namely the process concept, the stamp structure, and the main features of the equipment by which the process at the wafer scale was implemented
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
High resolution patterning of a sol-gel synthesized alumina-like negative photo-resist with low voltage EBL
No full textEffect of nanoimprint on the elastic modulus of PMMA: Comparison between standard and ultrafast thermal NIL
No full textThis paper is focused on the understanding of the effect of the nanoimprint lithography process on the elastic modulus of thin, thermoplastic films. In particular, we present the comparison between the standard and an ultrafast thermal NIL technology as well as the way both processes affect the top surface of poly(methyl methacrylate) (PMMA). The PeakForce QNMTM (Quantitative Nanomechanical Property Mapping) scanning probe technique was used to determine the Young’s modulus of PMMA by comparison with a polystyrene standard. We demonstrate that imprinted PMMA, regardless of the used method, shows a 9-fold increase of Young’s modulus compared to non-imprinted PMMA at least in the top 3-5 nm thick surface layer. This important finding proves that the ultrafast process with much higher temperatures, but also with much shorter process times, leads to elastic surface properties that are comparable to those of PMMA imprinted with the standard process. We have confirmed that annealing alone does not significantly influence the Young’s modulus
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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