Master's Thesis

2D metal-organic frameworks from organic carbonitrile molecules on weakly interacting substrates

Final Thesis 5.8 MB

Author of thesis: Ing. Anna Kurowská

Acad. year: 2022/2023

Supervisor: Dr. Matthias Blatnik

Reviewer: dr. Bruno de la Torre

Abstract:

Molecular self-assembly is a spontaneous association of molecules into well-defined supra-molecular structures on surfaces. Organic molecules exhibiting self-assembly can act as building blocks at the nanoscale and allow for a bottom-up synthesis of atomically precise arrangements, e.g., two-dimensional (2D) nanoarrays. The incorporation of metal atoms leads to the formation of a 2D metal-organic framework (2D MOF). Therein, embedded (magnetic) metal atoms are arranged in a periodic way, linked by organic linker units. At the surface of a material, this holds powerful opportunities, e.g., to change the electronic properties of a material or enable the usage of exotic new states of matter in device technology. This thesis studies assembled structures of carbonitrile molecules and transitional metal atoms on coinage metal and topological insulator surfaces. The molecules HATCN and DCA are tested as suitable candidates for organic linker units. We present especially LEEM and STM results for molecular self-assembly on both types of surfaces and for the metal-organic structure formation on coinage metals. In particular, the DCA molecules show high potential as a linker. We successfully formed a long-range ordered MOF with Fe atoms on the Ag(111) surface and a molecular self-assembly was observed for DCA deposited on Bi2Se3.

Keywords:

Self-assembly, metal-organic frameworks (MOFs), long-range order, HATCN, DCA, Fe, Ag(111), Bi2Se3, diffraction, STM, LEEM, XPS

Date of defence

20.06.2023

Result of the defence

Defended (thesis was successfully defended)

znamkaAznamka

Grading

A

Process of defence

Po otázkách oponenta bylo dále diskutováno: Jaké "nečistoty" plánujete používat pro získání magnetických vlastností. STM měření vzorku, vznik signálu. Studentka na otázky odpověděla s přehledem.

Language of thesis

English

Faculty

Department

Study programme

Physical Engineering and Nanotechnology (N-FIN-P)

Composition of Committee

prof. RNDr. Tomáš Šikola, CSc. (předseda)
prof. RNDr. Jiří Spousta, Ph.D. (místopředseda)
prof. Mgr. Dominik Munzar, Dr. (člen)
doc. Mgr. Adam Dubroka, Ph.D. (člen)
prof. RNDr. Petr Dub, CSc. (člen)
prof. RNDr. Bohumila Lencová, CSc. (člen)
prof. RNDr. Jiří Petráček, Dr. (člen)
prof. RNDr. Radim Chmelík, Ph.D. (člen)
doc. Ing. Radek Kalousek, Ph.D. (člen)
prof. Ing. Miroslav Kolíbal, Ph.D. (člen)
doc. Ing. Stanislav Průša, Ph.D. (člen)
RNDr. Antonín Fejfar, CSc. (člen)

Supervisor’s report
Dr. Matthias Blatnik

Ms. Kurowská wrote her thesis on the topic “2D Metal-Organic Frameworks from Organic Carbonitrile Molecules on Weakly Interacting Substrates”. In her thesis, Ms. Kurowská investigates the adsorption, phase formation of molecular self-assembly of organic carbonitrile molecules, and subsequently the creation of metal-organic frameworks including these molecules first on the coinage metals Ag(111) and Au(111). She further studies the possibility of transferring the obtained recipes to the surface of the weakly interacting (0001) surface of the topological insulator Bi2Se3.
After reviewing the state-of-the-art concerning the adsorption of molecular phases of organic carbonitrile molecules and the formation of metal-organic networks including them on relevant substrates, Ms. Kurowská describes the main goals, which was the experimental investigation of the adsorption of carbonitrile molecules on low index coinage metals surfaces and formation of metal-organic frameworks. During the experimental work, she had to do pioneering adsorption and characterization studies as the chosen molecule was not previously used in our research group. These tasks Ms. Kurowská mastered in an excellent manner and even superseded them explicitly by investigating not only one but more than one candidate molecule and its incorporation into a 2D metal-organic framework and explored ways how to transfer these impressions and recipes to a weakly interacting substrate, e.g., the (0001) surface of the topological insulator Bi2Se3.
I am happy to report thus, that Ms. Kurowská has succeeded and even exceeded in all of the tasks imposed onto her even though the achieved results were very difficult to analyze and understand. Ms. Kurowská’s work in the laboratory was excellent, completely independent, professional, and extremely motivated to go to extended lengths to master her task. In addition, I can report that Ms. Kurowská mastered the task of writing about her work in a highly scientific way and on an excellent level.
Evaluation criteria Grade
Splnění požadavků a cílů zadání A
Postup a rozsah řešení, adekvátnost použitých metod A
Vlastní přínos a originalita B
Schopnost interpretovat dosažené výsledky a vyvozovat z nich závěry A
Využitelnost výsledků v praxi nebo teorii B
Logické uspořádání práce a formální náležitosti A
Grafická, stylistická úprava a pravopis A
Práce s literaturou včetně citací A
Samostatnost studenta při zpracování tématu A
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Grade proposed by supervisor: A

Reviewer’s report
dr. Bruno de la Torre

This master's thesis creates a favorable impression on the reader by employing a well-designed structure. The theory chapter provides essential information that enables comprehension of the results and discussion sections. Furthermore, it is noteworthy that the manuscript stays focused on the topic, with each part seamlessly connected in a logical sequence. Overall, the text exhibits proficient style and grammar. It is important to mention that a few typos and minor grammatical errors are present, which is common. However, considering that the student is not a native speaker, the quality of the work surpasses the average standard.

Takin into account the level of difficulty of a technique such as STM in UHV conditions, the
results showed in the manuscript are of high quality. That implies a lot of effort from the
student’s side to achieve enough proficiency in order to obtain the images and spectroscopies
presented. After reading the whole manuscript, I find interesting the fundamental physics
behind the results. I would also like to mention the importance of collaborating with the proper
groups in order to extend the depth of understanding of the problem.

1.  Fulfilment of requirements and objectives of assignment
In particular, the thesis declares, "The primary objective of this study is to construct a 2D MOF using organic carbonitrile molecules on weakly interacting substrates." However, this objective has only been accomplished on the Ag(111) surface, which, in the field of surface science, is not regarded as a weakly interacting surface when compared to other suggested 2D materials. Although the intended goal was not fully realized, the thesis successfully encompasses several significant milestones towards the completion of this highly ambitious project.

2.  Working process, extent and suitability of applied methods
The planning and execution of the experiments are well aligned with the thesis framework. The chosen techniques are highly suitable and contribute to the successful achievement of the primary objective.

3.  Scholarly contribution and originality
While the concept of MOF formation on topological insulator surfaces and the proposed molecular systems may not be entirely original, this research has explored numerous novel phenomena in the field of molecular self-assembly. Several unanswered questions have emerged, presenting exciting research prospects. Notably, the utilization of the Bi2Se3 sample is particularly innovative.

4.  Ability to interpret achieved results and draw conclusions
The interpretation of the data presented in the manuscript is reliable and dependable. The student has made a genuine effort to extract as much information as possible from the acquired data, offering plausible analysis. The discussion follows a logical sequence that reflects the student's thought process in designing the experiment and determining the subsequent steps.

5.  Applicability of results in practice or theory
As mentioned earlier, the research delves into the fundamental comprehension of molecular processes in self-assembly on surfaces. Although there is no immediate apparent practical application of the findings, it paves the way for exploring and gaining insights into new physico-chemical phenomena occurring on significant surfaces of topological insulators. This research holds the potential to unlock further understanding in this field.

6.  Logical arrangement of thesis and its layout
As mentioned previously, the thesis exhibits a well-structured format, with the introduction and methods chapters providing essential information for understanding the results and discussion sections. However, I have a few minor remarks to share. In the theory chapter, there is a lack of theoretical content and instead, it primarily serves as an introduction to the field of surface science. While there is an extensive discussion on nucleation theory, it only covers a small portion of the experimental results and the presentation of analytical techniques. Therefore, the title "Theory" for this chapter may not be appropriate, as it mainly focuses on providing the necessary background. Additionally, there is a notable absence of crucial information concerning the Bi2Se3 sample, such as its acquisition method, which should have been included in this chapter.

7.  Graphic layout, used style and language level
The figures presented in the thesis are generally clear and informative. The use of appropriate colors and font sizes in figures and graphs aids in understanding the key findings being conveyed by the student. The image captions provide descriptive and illustrative information, effectively assisting in comprehending the results.

8.  Work with used sources including quotations
In this regard, the student has made appropriate choices regarding the citations, making it convenient to locate the relevant details when necessary.
Evaluation criteria Grade
Splnění požadavků a cílů zadání A
Postup a rozsah řešení, adekvátnost použitých metod A
Vlastní přínos a originalita A
Schopnost interpretovat dosaž. výsledky a vyvozovat z nich závěry A
Využitelnost výsledků v praxi nebo teorii A
Logické uspořádání práce a formální náležitosti A
Grafická, stylistická úprava a pravopis A
Práce s literaturou včetně citací A
Topics for thesis defence:
  1. Q1- I appreciate the student's proposal of a model for the self-assembly of HATCN molecules on Ag(111) using STM images. However, I felt the absence of more quantitative analysis. It would have been valuable to extract bonding distances from the model. Additionally, I was curious if the student could provide a quantitative comparison between the models presented in Figure 2.2 and Figure 2.7.
  2. Q-2 Were the LEIS experiments conducted within your research group? If so, to what extent were you involved in them?
  3. Q-3 How does the presence of residual Se atoms impact the process of molecular self-assembly on the Bi2Se3 sample?
  4. Q-4 It can be inferred that the ultimate objective of the project is to incorporate magnetic surface impurities into a topological insulator. I am curious if the student can provide insights on the techniques she plans to employ for further nanoscale characterization of the surface magnetization.
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Grade proposed by reviewer: A