|Tipo di tesi||Tesi di dottorato di ricerca|
|Titolo||Adsorbimento mediante auto-assemblaggio ed epitassia da fasci molecolari di molecole organiche aromatiche basate su calcogeni su superfici metalliche e dielettriche|
|Titolo in inglese||Adsorption of chalcogen-based aromatic organic molecules on metal and dielectric surfaces by self-assembly and molecular beam epitaxy|
|Settore scientifico disciplinare||FIS/01 - FISICA SPERIMENTALE|
|Corso di studi||INFORMATION AND COMMUNICATION TECHNOLOGIES (ICT)|
|Data inizio appello||2017-12-18|
|Disponibilità||Accessibile via web (tutti i file della tesi sono accessibili)|
In questo lavoro sono stati studiati diversi sistemi e interfacce interessanti per applicazioni di elettronica molecolare. In particolare sono stati studiati monostrati autoassemblati di benzeneselenolo (BSe) e selenofene (Sph) su Cu (111) preparati in soluzione, l'adsorbimento di differenti derivati di tiofene su oro, film ultrasottili di α-Sexitiofene (6T) su superfici planari di CaF2 (111) / Si (111) e su superfici corrugate di CaF2 (110) / Si (001) mediante epitassia da fasci molecolari.
This work has started with the study of self-assembled monolayers of benzeneselenol (BSe), selenophene (Sph) on Cu(111) by solution method. Then the adsorption of a series of thiophene derivatives on gold has been systematically studied. In the end we have studied the α-Sexithiophene (6T) ultrathin films grown on CaF2(111)/Si(111) planar surfaces and on CaF2(110)/Si(001) ridged surfaces by molecular beam epitaxy. These systems are interesting for molecular electronics applications. The techniques employed in this work basically include High Resolution X-ray photoelectron spectroscopy (XPS), Near Edge X-ray Absorption Fine Structure (NEXAFS) based on synchrotron radiation, Low Energy Electron Diffraction (LEED) and Atomic Force Microscopy (AFM). Density Functional Theory (DFT) calculations are presented in some cases to complement the experimental results. The fits of XPS spectra for atomic Se adsorption on Cu(111) display several components related to different adsorption configurations and annealing treatment results in the appearance of ordered structure in LEED images. XPS and NEXAFS spectra for BSe adsorptions on Cu(111) indicate the occurrence of Se-C scission leading to the creation of atomic Se. The adsorptions of Sph also demonstrate the possibility with Se-C bond cleavage. For the thiophene derivative adsorptions on Au, the S2p XPS spectra can be attributed to intact molecules on different adsorption sites and broken molecules due to the dissociation process. DFT calculations show that the S2p binding energy for intact thiophene (1T) can be the same as for the alkene and alkane thiol cases as opposed to usual assumption in the literature. α-Sexithiophene (6T) thin films on CaF2 show substantially different morphologies: large islands with flat terraces without in-plane preference on CaF2(111); narrow and elongated islands following the substrate corrugation on CaF2(110). XPS and NEXAFS indicate that the interaction between α-6T and surface is weak, and the molecules align with their long axis perpendicular to the surfaces for both cases. The obtained results indicate the complex scenario that can be obtained at interfaces of S-containing organic molecules and inorganic substrates. This has important implications as far as charge injection, band alignment and electronic transport is considered in molecular electronic devices based on these systems.