zaključna naloga
Manica Perko (Author), Miha Škarabot (Mentor), Marion Van Midden (Co-mentor)

Abstract

Samourejanje molekul na površini je obetavna strategija za izdelavo velikih, z atomsko natančnostjo urejenih površin z željenimi lastnostmi. Poleg tega pa lahko na podlagi samourejenih struktur sklepamo o tem, katere medmolekularne interakcije ali interakcije s podlago igrajo ključno vlogo pri vezavi molekul na površino. V tej nalogi smo preučevali vezavo korozijskega inhibitorja 2-mercaptobenzimidazol-a na atomsko čisto površino bakra s kristalografsko orientacijo Cu(111). Za preučevanje smo uporabili vrstični tunelski mikroskop, ki temelji na tuneliranju elektronov med atomsko ostro konico in vzorcem. Tunelski tok je eksponentno odvisen od razdalje med konico in vzorcem, kar nam omogoča zelo natančno slikanje površine, ki skupaj z ostro konico omogoča meritev topografije z atomsko ločljivostjo. Zato je pomembno, da pripravimo čisto površino, na katero se vežejo molekule. Najprej smo z izmeničnim ionskim jedkanjem in žarjenjem pripravili atomsko čisto površino bakra Cu(111), nato pa smo z naparevanjem nanjo v ultra visokem vakuumu nanesli molekule. S spreminjanjem temperature vzorca med naparevanjem smo spreminjali energijo, ki jo imajo na voljo za samourejanje, s spreminjanjem hitrosti in časa naparevanja pa smo pripravili vzorec z določeno koncentracijo molekul na površini. Tako smo dobili različne samourejene strukture. Da bi lahko sklepali o vezavi molekul, smo morali na podlagi slik, posnetih s tunelskim vrstičnim mikroskopom, določiti strukturo nastale plasti. Ker mikroskop ni kemijsko ločljiv, smo si pri interpretaciji rezultatov pomagali s simuliranimi slikami, ki so bile izračunane s pomočjo teorije gostotnih funkcionalov. Ugotovili smo, da so energijske skale interakcij zelo primerljive med sabo, saj molekule tvorijo veliko različnih samourejenih struktur. Poleg tega pa so na površini že pri nizkih temperaturah zelo mobilne iz česar lahko sklepamo, da pri preprečevanju korozije ni ključna zgolj močna vezava na najbolj izpostavljena mesta na površini.

Keywords

samourejanje molekul;vrstična tunelska mikroskopija;tanke plasti;nanotehnologija;

Data

Language: Slovenian
Year of publishing:
Typology: 2.11 - Undergraduate Thesis
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [M. Perko]
UDC: 544.72
COBISS: 3348580 Link will open in a new window
Views: 717
Downloads: 184
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Other data

Secondary language: English
Secondary title: Self-assembly of the corrosion inhibitor on copper surface
Secondary abstract: Molecular self-assembly on surfaces is a promising strategy for producing large, atomically ordered structures with desired properties. On the other hand, self-assembled structures can also be used to investigate whether it is intermolecular interactions or interactions with the surface that play a key role in how the molecules arrange on the surface. This has been used to study how the corrosion inhibitor 2-mercaptobenzimidazole behaves on the atomically clean surface of copper with a crystallographic orientation of Cu(111) using scanning tunneling microscopy (STM). STM is based on tunneling of electrons between an atomically sharp tip and the sample. Since the current is exponentially dependent on the distance, this enables very accurate measurement of the surface corrugation, which, together with the sharp tip, allows us to image topography with atomic resolution. To do so it is important to prepare a clean surface. Alternating cycles of ion sputtering and annealing have been used to prepare clean copper samples. After characterization in STM, molecules were deposited on the sample in ultra high vacuum by thermal evaporation. The evaporation rate was kept approximately while the time the sample was exposed to the molecular beam was varied, which resulted in different concentrations on the surface. Varying the substrate temperature between different experiments limits the energy molecules have to self assemble, which results in different self assembled structures. To elucidate the binding the structure of the resulting layer bases on STM images of the surface had to be determined. Because STM is not directly chemically sensitive density functional theory (DFT) simulations were used to verify the proposed models. Several self assembled structures suggest that the energy scales of competing interactions must be similar. High mobility even at very low temperatures opposes the idea that strong binding to certain sites on the surface is crucial for corrosion prevention.
Secondary keywords: molecular self assembly;scanning tunneling microscopy;thin layers;nanotechnology;
Type (COBISS): Final paper
Study programme: 0
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: 38 str.
ID: 11221163