Two-dimensional (2D) materials have been captivating researchers in material science due to their unique properties, distinct from their bulk counterparts, which arise from quantum confinement effects. However, balancing scalability, time efficiency, and product quality in fabricating 2D materials is still a challenging task. This dissertation explores the use of solvent-free synthesis strategies compatible with a surface science approach (i.e. on-surface synthesis and pulsed laser deposition) for the fabrication of 2D graphdiyne-like (GDY) networks, transition metal dichalcogenides (TMDs), and bismuth telluride nanostructures, grown on metallic surfaces under ultra-high vacuum conditions. These materials, as well as their combinations into heterostructures, hold significant promise for future advanced applications, such as optoelectronic and sensing devices; a fundamental understanding of the growth process and the connection between atomic structure and electronic properties is thus of great importance. Characterization techniques conducted in situ – such as scanning tunneling microscopy and spectroscopy, Raman spectroscopy, and angle-resolved photoelectron spectroscopy – were employed to investigate the growth, atomic structure, electronic and vibrational properties, and thermal evolution of metal-supported 2D materials, as well as the influence exercised by the metallic substrates. Relevant findings include the mapping of the band structure and the frontier-orbital assignment in a 2D GDY organometallic framework, the thermal transition from organometallic carbon nanowires to a 2D amorphous sp–sp2 network, the observation of the morphological evolution in 2D Bi–Te-based nanostructures, and the fabrication of 2D TMD vertical heterostructures with evidence of strong interlayer coupling.
I materiali bidimensionali (2D) affascinano i ricercatori nell'ambito della scienza dei materiali grazie alle loro proprietà uniche e distinte dalle loro controparti bulk, derivanti da effetti di confinamento quantistico. Tuttavia, bilanciare scalabilità, efficienza e qualità del prodotto rimane ancora una sfida impegnativa. In questa tesi di dottorato, si esplora l'uso di strategie di sintesi a secco compatibili con un approccio da scienza delle superfici (i.e. sintesi catalizzata da superficie e deposizione tramite laser pulsato) per la fabbricazione di network grafdiinici (GDY) e nanostrutture a base di calcogenuri di metalli di transizione (TMD) e tellururo di bismuto, cresciuti su superfici metalliche in condizioni di ultra alto vuoto. Tali materiali, così come la loro combinazione in eterostrutture, sono particolarmente promettenti in applicazioni avanzate quali dispositivi optoelettronici o sensori; di conseguenza, uno studio fondamentale del processo di crescita, nonché del rapporto tra struttura atomica e proprietà elettroniche, risulta necessario. Varie tecniche di caratterizzazione condotte in situ, tra cui microscopia e spettroscopia a effetto tunnel, spettroscopia Raman e spettroscopia di fotoemissione risolta in angolo, sono state impiegate per indagare la crescita, la struttura atomica, le proprietà elettroniche e vibrazionali, e l'evoluzione termica di tali materiali 2D, nonché la loro interazione con i substrati metallici. I risultati più rilevanti includono la mappatura della struttura a bande di un network GDY organometallico, la transizione termica da nanofili organometallici a un network di carbonio amorfo sp–sp2, l'osservazione dell'evoluzione morfologica di nanostrutture a base Bi–Te, e la fabbricazione di eterostrutture TMD con evidenza di un forte accoppiamento tra i due layer.
Synthesis and in-situ characterization of 2D materials on metals
D'AGOSTA, PAOLO
2023/2024
Abstract
Two-dimensional (2D) materials have been captivating researchers in material science due to their unique properties, distinct from their bulk counterparts, which arise from quantum confinement effects. However, balancing scalability, time efficiency, and product quality in fabricating 2D materials is still a challenging task. This dissertation explores the use of solvent-free synthesis strategies compatible with a surface science approach (i.e. on-surface synthesis and pulsed laser deposition) for the fabrication of 2D graphdiyne-like (GDY) networks, transition metal dichalcogenides (TMDs), and bismuth telluride nanostructures, grown on metallic surfaces under ultra-high vacuum conditions. These materials, as well as their combinations into heterostructures, hold significant promise for future advanced applications, such as optoelectronic and sensing devices; a fundamental understanding of the growth process and the connection between atomic structure and electronic properties is thus of great importance. Characterization techniques conducted in situ – such as scanning tunneling microscopy and spectroscopy, Raman spectroscopy, and angle-resolved photoelectron spectroscopy – were employed to investigate the growth, atomic structure, electronic and vibrational properties, and thermal evolution of metal-supported 2D materials, as well as the influence exercised by the metallic substrates. Relevant findings include the mapping of the band structure and the frontier-orbital assignment in a 2D GDY organometallic framework, the thermal transition from organometallic carbon nanowires to a 2D amorphous sp–sp2 network, the observation of the morphological evolution in 2D Bi–Te-based nanostructures, and the fabrication of 2D TMD vertical heterostructures with evidence of strong interlayer coupling.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/221733