The aim of the present work is to develop a simple technique for the deposition of self-assembled monolayers (SAM) on silicon wafer substrates. The technique relies on physical process by evaporation and ricondensation of a precursor solution at ambient pressure, differently from conventional PVD that requires vacuum. The SAM is desposited on Si in order to give hydrophobic character. Hydrophobicity is the essential requisite for the final SAM coating since the SAM-covered Si wafer is supposed to be used for the fabrication of inkjet printing nozzles. In fact, semi-durable hydrophobic coatings are required in order to avoid the well-known issue of misdirection of the ink drop that flows out of the nozzle, thus increasing the inkjet printing resolution. Two different precursors, octadecytrichlorosilane (OTS) and tridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane (FOTS), have been selected to form the hydrophobic SAMs. These precursors have been chosen because of their long alkyl hydrophobic chain, the former, and the high amount of fluorinated CF and CF3 groups. The proposed deposition technique of OTS and FOTS SAMs, is here named A-PVD. The resulting SAMs are affected by a numbers of parameters that I investigated, tring to find an overall optimization for the deposition process. Indeed, in the first part of the work AFM analyses and contact angle measurements were used to fix the main processing parameters. The obtained results are coherent with those found in literature.Then, chemical and physical degradation tests were carried out to assess the quality of the SAMs. In addition, their stability in air was detected by monitoring the CA each day. Finally, further monolayer deposition was performed on preexisting one. Hence, multilayers coatings based on the same silane or a mixing coating (FOTS layer on top of OTS layer) were created. The formed multilayers SAMs were compared to the corresponding SAM. Chemical and physical degradation were conducted also on these last samples. The characterization techniques (FTIR, AFM, LFM and CA) and degradation tests have confirmed the successful development of hydrophobic coatings: CA ≈118˚ for FOTS based SAM and CA ≈110˚ for OTS based SAM. Moreover, the treated samples have shown optimal stability in air and good resistence to temperature. Regarding the chemical degradation, it strictly depends on the surface morphology.
Questo lavoro di tesi verte sulla realizzazione di rivestimenti monostrati idrorepellenti per ugelli di stampanti ad inchiostro. Al fine di ottenere una corretta fuoriuscita delle gocce di inchiostro, e conseguentemente un prodotto di stampa omogeneo con poche o nessuna sbavatura, l’ugello viene ricoperto da monostrati organici autoassemblati a base di molecole di silano (SAM). Precisamente, molecole di ottadecil tricloro silano (OTS) e tridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane (FOTS) sono state utilizzate come precursori organici nella realizzazione di SAMs. Quest’ ultimi minimizzano la degradazione dell’ugello rendendolo idrofobico. I SAMs sono stati depositati su wafers di silicio (materiale di cui è principalmente formato l’ugello) con un nuovo processo in fase vapore regolato da vari parametri. Per tanto la prima parte del progetto è centrata sull’ ottimizzazione dei parametri di processo, la quale è stata compresa tramite analisi AFM e variazioni dell’angolo di contatto. Successivamente, un’analisi più dettagliata è stata svolta sulla degradazione fisica e chimica dei SAMs e anche la loro stabilità in aria è stata monitorata tramite misure periodiche dell’angolo di contatto (CA). Infine, si è provato a condurre ulteriori deposizioni di molecole di OTS o FOTS su monostrati precedentemente assemblati, formando così multistrati di uno stesso silano o rivestimenti composti da uno strato di OTS e uno di FOTS. Infine i campioni così trattati sono stati poi paragonati ai rispettivi monostrati, elencandone i pro e i contro. Test di degradazione fisica e chimica sono stati poi condotti anche su quest’ultimi campioni. Le analisi di caratterizzazione (IR, CA and AFM) ed i test svolti, sia su rivestimenti monostrato sia su rivestimenti multistrato, hanno rilevato che sono stati effettivamente creati rivestimenti idrofobici: CA ≈118˚ per SAM a base di FOTS e CA ≈110˚ per quelli a base OTS. Inoltre questi presentano ottima stabilità in aria e ottima resistenza termica. Mentre la degradazione chimica dipende fortemente dalla morfologia del campione.
Antiwetting silane-based coating on silicon by atmospheric pressure vapour phase deposition
GUIDONE, ALESSANDRA
2017/2018
Abstract
The aim of the present work is to develop a simple technique for the deposition of self-assembled monolayers (SAM) on silicon wafer substrates. The technique relies on physical process by evaporation and ricondensation of a precursor solution at ambient pressure, differently from conventional PVD that requires vacuum. The SAM is desposited on Si in order to give hydrophobic character. Hydrophobicity is the essential requisite for the final SAM coating since the SAM-covered Si wafer is supposed to be used for the fabrication of inkjet printing nozzles. In fact, semi-durable hydrophobic coatings are required in order to avoid the well-known issue of misdirection of the ink drop that flows out of the nozzle, thus increasing the inkjet printing resolution. Two different precursors, octadecytrichlorosilane (OTS) and tridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane (FOTS), have been selected to form the hydrophobic SAMs. These precursors have been chosen because of their long alkyl hydrophobic chain, the former, and the high amount of fluorinated CF and CF3 groups. The proposed deposition technique of OTS and FOTS SAMs, is here named A-PVD. The resulting SAMs are affected by a numbers of parameters that I investigated, tring to find an overall optimization for the deposition process. Indeed, in the first part of the work AFM analyses and contact angle measurements were used to fix the main processing parameters. The obtained results are coherent with those found in literature.Then, chemical and physical degradation tests were carried out to assess the quality of the SAMs. In addition, their stability in air was detected by monitoring the CA each day. Finally, further monolayer deposition was performed on preexisting one. Hence, multilayers coatings based on the same silane or a mixing coating (FOTS layer on top of OTS layer) were created. The formed multilayers SAMs were compared to the corresponding SAM. Chemical and physical degradation were conducted also on these last samples. The characterization techniques (FTIR, AFM, LFM and CA) and degradation tests have confirmed the successful development of hydrophobic coatings: CA ≈118˚ for FOTS based SAM and CA ≈110˚ for OTS based SAM. Moreover, the treated samples have shown optimal stability in air and good resistence to temperature. Regarding the chemical degradation, it strictly depends on the surface morphology.| File | Dimensione | Formato | |
|---|---|---|---|
|
2018_04_guidone.pdf
non accessibile
Dimensione
4.66 MB
Formato
Adobe PDF
|
4.66 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/139515