Identification of ultra-thin molecular layers atop monolayer terraces in sub-monolayer organic films with scanning probe microscopy

Year: 2022

Authors: Chiodini S., Dinelli F., Martinez N.F., Donati S., Albonetti C.

Autors Affiliation: Consiglio Nazionale delle Ricerche – Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN) via P. Gobetti 101, 40129 Bologna, Italy Center for Nano Science and Technology, Fondazione Istituto Italiano di Tecnologia, Milan 20133, Italy Consiglio Nazionale delle Ricerche – Istituto Nazionale di Ottica (CNR-INO) via G. Moruzzi 1, 56124 Pisa, Italy ScienTec Ibyrica, Rufino Sbnchez 83, planta 2, Oficina 1, 28290 Las Rozas (Madrid), Spain

Abstract: The morphology of sub-monolayer sexithiophene films has been investigated in situ and ex situ as a function of the substrate temperature of deposition. In this thickness range, monolayer terraces formed of edge-on molecules, i.e. nearly upright, are typically nucleated. Herein, the terrace height is found to be correlated to both the film morphology and the substrate surface energy. In particular, the presence of a layer of variable thickness with molecules lying face-on or side-on can be identified atop the terraces when the deposition is carried out on inert substrates. This phenomenon can be evidenced thanks to accurate height measurements made with atomic force microscopy and further data obtained with advanced scanning probe microscopy techniques operating in different environments, viz. liquid, air and vacuum. An upward displacement of molecules from the substrate to the top of the terraces is considered to be responsible of this layer formation, whose molecules weakly interact with the underlying terraces.


Volume: 240      Pages from: 113598  to: 113598

More Information: Authors are grateful to Ricardo Garcia, Oleg Kolosov and Fabio Biscarini for the cumulative effect of their mentoring along years; it remains the basis of our education as microscopists and scientists. We are also in debt with Paolo Mei, Tiziano Bonfiglioli and Felice Carlo Simeone for their help in the implementation of OMBD systems and to the companies NuNano and Nanosensors for providing some tips. Authors also thanks Otello Maria Roscioni for Fig. 1. Data were analysed by the GNU General Public Licensed software QtiPlot, while figures are prepared with the GNU General Public Licensed software Veusz. Most of SPM images were collected in the SPM@ISMNfacility.FD and CA acknowledge support from CNR under the program ´Short Term Mobility´ in 2008 and 2009, respectively. The work was supported by EC FP7 ONE-P large-scale project n 212311 and EU-STREP ForceTool (NMP4-CT-2004-STRP 013684) projects.
KeyWords: Height measurement, Organic conjugated molecules, Organic film growth, Scanning probe microscopy, Sexithiophene, Ultrathin films
DOI: 10.1016/j.ultramic.2022.113598