Epitaxial multilayers of alkanes on two-dimensional black phosphorus as passivating and electrically insulating nanostructures

© The Royal Society of Chemistry. Mechanically exfoliated two-dimensional (2D) black phosphorus (bP) is epitaxially terminated by monolayers and multilayers of tetracosane, a linear alkane, to form a weakly interacting van der Waals heterostructure. Atomic force microscopy (AFM) and computational modelling show that epitaxial domains of alkane chains are ordered in parallel lamellae along the principal crystalline axis of bP, and this order is extended over a few layers above the interface. Epitaxial alkane multilayers delay the oxidation of 2D bP in air by 18 hours, in comparison to 1 hour for bare 2D bP, and act as an electrical insulator, as demonstrated using electrostatic force microscopy. The presented heterostructure is a technologically relevant insulator-semiconductor model system that can open the way to the use of 2D bP in micro-and nanoelectronic, optoelectronic and photonic applications

Substrati Molecolari Autoassemblanti per Nanofabbricazione Atomica

Uno tra gli attuali obiettivi delle nanotecnologie riguarda la messa a punto di materiali e tecniche per mettere a punto substrati molecolari idonei per la produzione di nanostrutture Infatti la possibilità di realizzare dei patterns di geometria prestabilita su questi materiali potrebbe avere importanti ricadute applicative in numerosi settori tecnologici. La tecnologia attuale propone numerose tecniche per la nanostrutturazione superficiale che, però, sono state generalmente pensate per substrati di natura inorganica di uso comune in microelettronica. Trasferire queste tecniche all’ambito dei substrati molecolari è spesso difficile: ad esempio, la litografia elettronica, o con fasci di cariche, che riscuote grande successo per la definizione di strutture nanometriche su metalli e semiconduttori convenzionali, non può essere applicata direttamente a substrati “soft” a causa dell’elevata energia cinetica delle particelle impiegate, che conduce a danneggiamenti indesiderati delle superfici. In questa tesi si studiano la realizzazione, le caratteristiche e le proprietà di monostrati molecolari autoassemblati (SAM) contenenti tioli finalizzati all’impiego come substrati per la nanofabbricazione atomica (Atomic NanoFabrication - ANF). In questa tecnica un fascio di atomi neutri, opportunamente manipolato mediante radiazione laser, viene fatto interagire con un’onda elettromagnetica stazionaria quasi-risonante che ne provoca una segregazione spaziale in strutture regolari. Queste strutture possono essere depositate direttamente su un substrato, oppure usate per provocarne un danneggiamento, o modifica superficiale, che, anche grazie alla bassa energia cinetica degli atomi, ha carattere locale (risoluzione spaziale dell’ordine delle decine di nanometri). Il lavoro di tesi riguarda la messa a punto dei substrati e la loro analisi su scala nanometrica condotta mediante microscopia a scansione di sonda, in particolare STM. Si studiano inoltre i risultati della deposizione, mediante ANF, di atomi di cesio sulla loro superficie, allo scopo di individuare le caratteristiche dell’interazione atomi/molecola di SAM e di verificare fenomeni caratteristici legati alla presenza di nano strutture di cesio, come l’effetto di Coulomb blockade. Infine, parte della tesi riguarda la messa a punto di un metodo innovativo per la nanoscrittura di superfici ossidate tramite intrappolamento di carica

Direct Comparison of the Effect of Processing Conditions in Electrolyte-Gated and Bottom-Gated TIPS-Pentacene Transistors

first_pagesettings Open AccessFeature PaperArticle Direct Comparison of the Effect of Processing Conditions in Electrolyte-Gated and Bottom-Gated TIPS-Pentacene Transistors by Nicolò Lago 1,*ORCID,Marco Buonomo 1,Federico Prescimone 2,Stefano Toffanin 2ORCID,Michele Muccini 2 andAndrea Cester 1 1 Department of Information Engineering, University of Padova, 35131 Padova, Italy 2 Institute of Nanostructured Materials (ISMN), National Research Council (CNR), 40129 Bologna, Italy * Author to whom correspondence should be addressed. Academic Editor: Horng-Long Cheng Electron. Mater. 2022, 3(4), 281-290; https://doi.org/10.3390/electronicmat3040024 (registering DOI) Received: 6 September 2022 / Revised: 21 September 2022 / Accepted: 23 September 2022 / Published: 27 September 2022 (This article belongs to the Special Issue Feature Papers of Electronic Materials (Second Volume)) Download PDF Browse Figures Citation Export Abstract Among the plethora of soluble and easy processable organic semiconductors, 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-P5) is one of the most promising materials for next-generation flexible electronics. However, based on the information reported in the literature, it is difficult to exploit in field-effect transistors the high-performance characteristics of this material. This article correlates the HMDS functionalization of the silicon substrate with the electrical characteristics of TIPS-P5-based bottom gate organic field-effect transistors (OFETs) and electrolyte-gated organic field-effect transistors (EGOFETs) fabricated over the same platform. TIPS-P5 transistors with a double-gate architecture were fabricated by simple drop-casting on Si/SiO2 substrates, and the substrates were either functionalized with hexamethyldisilazane (HMDS) or left untreated. The same devices were characterized both as standard bottom-gate transistors and as (top-gate) electrolyte-gated transistors, and the results with and without HMDS treatment were compared. It is shown that the functionalization of the silicon substrate negatively influences EGOFETs performance, while it is beneficial for bottom-gate OFETs. Different device architectures (e.g., bottom-gate vs. top-gate) require specific evaluation of the fabrication protocols starting from the effect of the HMDS functionalization to maximize the electrical characteristics of TIPS-P5-based devices

Macromolecular Dyes by Chromophore-Initiated Ring Opening Polymerization of L-Lactide

End functionalized polylactides are prepared by ring opening polymerization of L-lactide in the presence of stannous octoate (Sn(Oct)2). Three chromophores, 9H-carbazol-ethanol (CA), 9-fluorenyl-methanol (FM), and 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13, DR), are for the first time used as co-initiators in the polymerization process. The polymerization reaction is initiated by conventional thermal treatment, but in the case of FM, microwave-assisted polymerization is also carried out. CA and FM absorb and emit in the UV portion of the electromagnetic spectrum, whereas DR absorbs in the visible part. The obtained end-capped polylactides derivatives show the same photophysical properties as the initiator, so they are “macromolecular dyes” (MDs) that can be used “as synthesized” or can be blended with commercial poly(lactic acid) (PLA). The blends of PLA with MDs have ultraviolet-visible (UV-Vis) absorption and fluorescence emission features similar to that of MDs and thermal properties typical of PLA. Finally, migration tests, carried out onto the blends of PLA with MDs and PLA with free chromophores, show that MDs are less released than free chromophores both in solution and in the solid phase

3D versus 2D Electrolyte–Semiconductor Interfaces in Rylenediimide‐Based Electron‐Transporting Water‐Gated Organic Field‐Effect Transistors

AbstractWater‐gated organic field‐effect transistors (WGOFETs) are relevant devices for use in the fields of biosensors and biosystems. However, real applications require very stringent performance in terms of electrochemical stability and charge mobility to the organic semiconductor in contact with an aqueous environment. Here, a comparative study of two small‐molecule electron‐transporting perylenediimide semiconductors, which differ only in the N‐substituents named PDIF‐CN2 and PDI8‐CN2 is reported. The two materials present similar solid‐state arrangements but, while the PDI8‐CN2 shows a more 3D growth modality and electron mobility independent of the semiconductor layer thickness (≈10−4 cm2 V−1 s−1), the PDIF‐CN2 has an almost‐2D growth modality and the mobility increases with the semiconductor film thickness, reaching a maximum value of ≈5 × 10−3 cm2 V−1 s−1 at 30 nm. Above this thickness, the PDIF‐CN2 switches to a more 3D growth modality, and the mobility drops by one order of magnitude. XRR analysis indicates that a PDIF‐CN2 film can be modeled as a dense layered structure in which each layer is decoupled from the others due to the presence of fluorocarbon‐chains. The availability of additional pathways for charge transport from buried layers and the 2D versus 3D growth can explain the mobility dependence on the film thickness