The discovery of graphene in 2004 opened the door on the new class of two-dimensional (2D) materials. In recent years, increasing number of scientific publications focused on the synthesis and characterization of different types of atomically and quasi-atomically thin materials, which show appealing modifications of the electronic properties with respect to the bulk counterparts. The characteristic behaviour of a material, when extremely confined along one of the three dimensions, is promising for the implementation of electronic and optoelectronic devices in the constantly evolving field of nanotechnologies. In this framework, this thesis work reports the synthesis of 2D-MoS2 and 2D-WS2 on metallic substrates, using Pulsed Laser Deposition (PLD) technique, and the growth of silicene (silicon at the 2D-limit), exploiting Molecular Beam Epitaxy (MBE) technique on Ag (111) substrate. The fine tuning of the processes parameters was fundamental to obtain high-quality and high-coverage single and few-layers nanostructures. The characterization of the synthesised materials was performed in situ to study the morphological and structural properties, through Scanning Tunneling Microscopy (STM), and ex situ to analyse the vibrational properties and the stability at ambient conditions, through Raman and X-ray photo-electron spectroscopic techniques. Finally, this work also presents preliminary results concerning the synthesis and the characterization of lateral and vertical heterostructures, obtained by PLD of 2D-WS2 followed by PLD of 2D-MoS2, exploiting a double-step deposition approach on metallic substrates.
La scoperta del grafene nel 2004 ha svelato la nuova classe dei materiali bi-dimensionali (2D). Negli ultimi anni si è registrato un crescente numero di pubblicazioni scientifiche incentrate sulla sintesi e sulla caratterizzazione di diversi materiali con uno spessore atomico o quasi atomico (2D). Questi materiali presentano proprietà elettroniche completamente diverse rispetto alle corrispettive forme bulk e che sono promettenti in vista di future applicazioni elettroniche e optoelettoniche nel campo delle nanotecnologie. Questo lavoro di tesi riporta la sintesi di nanostrutture 2D di WS2 e MoS2 su substrati metallici, tramite l'uso della tecnica di Deposizione a Laser Pulsato (PLD, Pulsed Laser Deposition) e la sintesi di silicene (la forma bidimensionale del silicio) tramite epitassia da fasci molecolari (MBE, Molecular beam epitaxy) su una superficie di Ag (111). La precisa messa a punto dei parametri di processo è stata fondamentale per ottenere nanostrutture costituite da un singolo o da pochi strati di materiale, ad alta qualità e ad alto ricoprimento. La caratterizzazione dei materiali sintetizzati è stata effettuata in situ tramite microscopia a effetto tunnel (STM, Scanning Tunneling Microscopy), per studiare le proprietà morfologiche e strutturali, ed ex situ tramite spettroscopia Raman e spettroscopia da fotoemissione a raggi X (XPS, X-ray Photoelectron Spectroscopy) per analizzare le proprietà vibrazionali e la stabilità in condizioni ambiente. Per concludere, in questo elaborato di tesi sono riportati anche i risultati preliminari degli esperimenti di sintetizzazione e caratterizzazione di eterostrutture laterali e verticali, ottenute tramite PLD prima di WS2 e poi di MoS2 su substrati metallici.
Synthesis and characterization of two-dimensional materials on metallic substrates
RUGGERI, MARINA
2018/2019
Abstract
The discovery of graphene in 2004 opened the door on the new class of two-dimensional (2D) materials. In recent years, increasing number of scientific publications focused on the synthesis and characterization of different types of atomically and quasi-atomically thin materials, which show appealing modifications of the electronic properties with respect to the bulk counterparts. The characteristic behaviour of a material, when extremely confined along one of the three dimensions, is promising for the implementation of electronic and optoelectronic devices in the constantly evolving field of nanotechnologies. In this framework, this thesis work reports the synthesis of 2D-MoS2 and 2D-WS2 on metallic substrates, using Pulsed Laser Deposition (PLD) technique, and the growth of silicene (silicon at the 2D-limit), exploiting Molecular Beam Epitaxy (MBE) technique on Ag (111) substrate. The fine tuning of the processes parameters was fundamental to obtain high-quality and high-coverage single and few-layers nanostructures. The characterization of the synthesised materials was performed in situ to study the morphological and structural properties, through Scanning Tunneling Microscopy (STM), and ex situ to analyse the vibrational properties and the stability at ambient conditions, through Raman and X-ray photo-electron spectroscopic techniques. Finally, this work also presents preliminary results concerning the synthesis and the characterization of lateral and vertical heterostructures, obtained by PLD of 2D-WS2 followed by PLD of 2D-MoS2, exploiting a double-step deposition approach on metallic substrates.| File | Dimensione | Formato | |
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2019_12_Ruggeri.pdf
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https://hdl.handle.net/10589/152105