Dissertations / Theses: 'Scanning tunneling microscopy'

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Kulawik, Maria. "Low temperature scanning tunneling microscopy." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979718848.

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Ding, Haifeng. "Spin-polarized scanning tunneling microscopy." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963217186.

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Gustafsson, Alexander. "Theoretical modeling of scanning tunneling microscopy." Doctoral thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-69012.

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The main body of this thesis describes how to calculate scanning tunneling microscopy (STM) images from first-principles methods. The theory is based on localized orbital density functional theory (DFT), whose limitations for large-vacuum STM models are resolved by propagating localized-basis wave functions close to the surface into the vacuum region in real space. A finite difference approximation is used to define the vacuum Hamiltonian, from which accurate vacuum wave functions are calculated using equations based on standard single-particle Green’s function techniques, and ultimately used to compute the conductance. By averaging over the lateral reciprocal space, the theory is compared to a series of high-quality experiments in the low- bias limit, concerning copper surfaces with adsorbed carbon monoxide (CO) species and adsorbate atoms, scanned by pure and CO-functionalized copper tips. The theory compares well to the experiments, and allows for further insights into the elastic tunneling regime. A second significant project in this thesis concerns first-principles calculations of a simple chemical reaction of a hydroxyl (oxygen-deuterium) monomer adsorbed on a copper surface. The reaction mechanism is provided by tunneling electrons that, via a finite electron-vibration coupling, trigger the deuterium atom to flip between two nearly identical configurational states along a frustrated rotational motion. The theory suggests that the reaction primarily occurs via nuclear tunneling for the deuterium atom through the estimated reaction barrier, and that over-barrier ladder climbing processes are unlikely.

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Blackham, Ian George. "Scanning tunneling microscopy of electrode surfaces." Thesis, University of Oxford, 1992. https://ora.ox.ac.uk/objects/uuid:f9d27595-1177-406f-89a2-1448ac654dd3.

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A scanning tunneling microscope (STM) suitable for the in-situ study of electrode surfaces under electrochemical control has been developed. The system consists of commercially available software and feedback electronics, with a custom-built stage and electrochemical control. The stage incorporates an automatic coarse approach mechanism for ease of operation. Gold single crystal spheres (SCS) and gold on mica thin films have been studied as surfaces potentially suitable for samples in in-situ electrochemical STM experiments. Characteristic features of each surface have been identified. High resolution in-situ STM imaging of the electro-oxidation of a gold surface in a sulphuric acid electrolyte has been achieved. Surface rearrangement at potentials positive of the double layer region has been observed and correlated with cyclic voltammetry. As yet unexplained features resulting from biasing the surface at potentials negative of the double layer region are reported. In phosphate electrolyte, bulk surface oxide formation and the surface resulting from reduction of the oxide have been imaged. Some aspects of the direct electrochemistry of cytochrome c at 4,4' dithiodipyridine (SSBPY) modified gold electrodes have been investigated. In-situ FTIR showed the potential dependent orientation of adsorbed thiopyridine species, while ex-situ and in-situ STM studies showed a novel surface pitting process to be active. It is hypothesised the STM experiment itself induces the process to take place. Features attributable to cytochrome c molecules have been observed. Rearrangement of gold on mica surfaces, on exposure to certain aqueous solutions has been observed and the process is attributed to the interaction of the solutions with the original surface structure present.

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Heben, Michael J. Lewis Nathan Saul Lewis Nathan Saul. "Scanning tunneling microscopy in electrochemical environments /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-06122007-104233.

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6

Pinheiro, Lucidalva dos Santos. "Scanning probe microscopy of adsorbates." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320589.

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7

Weeks, Brandon Lea. "Applications of high-pressure scanning tunneling microscopy." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621999.

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Salazar, Enríquez Christian David. "Scanning tunneling microscopy on low dimensional systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-211572.

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This thesis contains experimental studies on low dimensional systems by means of scanning tunneling microscopy (STM). These studies include investigations on dinickel molecular complexes and experiments on iron nanostructures used for the implementation of the spin-polarized scanning tunneling microscopy technique at the IFW-Dresden. Additionally, this work provides detailed information of the experimental technique (STM), from the theoretical background to the STM-construction, which was part of this doctoral work. Molecular anchoring and electronic properties of macrocyclic magnetic complexes on gold surfaces have been investigated by mainly scanning tunneling microscopy and complemented by X-rays photoelectron spectroscopy. Exchange–coupled macrocyclic complexes [Ni2L(Hmba)]+ were deposited via 4-mercaptobenzoate ligands on the surface of Au(111) single crystals. The results showed the success of gold surface-grafted magnetic macrocyclic complexes forming large monolayers. Based on the experimental data, a growth model containing two ionic granular structures was proposed. Spectroscopy measurements suggest a higher gap on the cationic structures than on the anionic ones. Furthermore, the film stability was probed by the STM tip with long-term measurements. This investigation contributes to a new promising direction in the anchoring of molecular magnets to metallic surfaces. Iron nanostructures of two atomic layers and iron-coated tungsten tips were used in order to implement the spin-polarized scanning tunneling microscopy technique at the IFW-Dresden. First of all, a systematic study of the iron growth, from sub-monolayers to multilayers on a W(110) crystal is presented. Subsequent to the well-understanding of the iron growth, the experiments were focused on revealing, for the first time at the IFW-Dresden, the magnetic inner structure of iron nanostructures. The results evidently showed the presence of magnetic domains of irregular shapes. Furthermore, SP-STM probed the bias voltage dependence of the magnetic contrast on the iron nanostructures. This technique opens up a new powerful research line at the IFW-Dresden which is promising for the study of quantum materials as molecular magnets and strongly correlated systems.

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DiLullo, Andrew R. "Manipulative Scanning Tunneling Microscopy and Molecular Spintronics." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1363821351.

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Kersell, Heath R. "Alternative Excitation Methods in Scanning Tunneling Microscopy." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1449074449.

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Gambrel, Grady A. "Scanning Tunneling Microscopy of Two-Dimensional Materials." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu149424786854182.

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Tomic, Aleksandra T. "Scanning tunneling microscopy of complex electronic materials." Diss., Connect to online resource - MSU authorized users, 2008.

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Thesis (Ph.D.)--Michigan State University. Dept. of Physics and Astronomy, 2008.
Title from PDF t.p. (viewed on Mar. 27, 2009) Includes bibliographical references (p. 95-102). Also issued in print.

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Henson, Tammy Deanne 1964. "Scanning tunneling microscopy of layered structure semiconductors." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276807.

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Semiconductors are characterized by atomic resolution imaging and density of states measurements (DOS) obtained through the use of a scanning tunneling microscope (STM). The DOS of the conduction and valence bands can be measured separately with a STM as opposed to an optical measurement which measures only the joint DOS. Layered-structure semiconductors are characterized both in the bulk form and in the isolated cluster form. Images of three bulk layered-structure semiconductors, MoS₂, WSe₂, and SnS₂, were obtained with both positive and negative sample-to-tip bias voltages. Curves of tunneling current as a function of bias voltage were measured, from which the DOS of the valence and conduction bands can be inferred. We obtained an atomically resolved image of an isolated fragment of a semi-conductor cluster which was deposited on a graphite surface from a colloidal suspension of BiI₃. Also imaged were clusters of MoS₂ layered-structure semiconductors.

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He, Yang. "Scanning Tunneling Microscopy Study on Strongly Correlated Materials." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718719.

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Strongly correlated electrons and spin-orbit interaction have been the two major research directions of condensed matter physics in recent years. The discovery of high temperature superconductors in 1986 not only brought excitement into the field but also challenged our theory on quantum materials. After almost three decades of extensive study, the underlying mechanism of high temperature superconductivity is still not fully understood, the reason for which is mainly a poor understanding of strongly correlated systems. The phase diagram of cuprate superconductors has become more complicated throughout the years as multiple novel electronic phases have been discovered, while few of them are fully understood. Topological insulators are a newly discovered family of materials bearing topological non-trivial quantum states as a result of spin-orbit coupling. The theoretically predicted topological Kondo insulators as strongly correlated systems with strong spin-orbital coupling make an ideal playground to test our theory of quantum materials. Scanning tunneling microscopy (STM) is a powerful technique to explore new phenomena in materials with exotic electronic states due to its high spacial resolution and high sensitivity to low energy electronic structures. Moreover, as a surface-sensitive technique, STM is an ideal tool to investigate the electronic properties of topological and non-topological surface states. In this thesis, I will describe experiments we performed on high temperature superconductors and topological Kondo insulators using STM. First, I will describe our experiments on a Bi-based high temperature superconductor $\mathrm{Bi_2Sr_2CuO_{6+\delta}}$. The quasiparticle interference technique uncovers a Fermi surface reconstruction. We also discovered the coexistence of Bogoliubov quasiparticle and pseudogap state at the antinodes. Afterwards, I will discuss our discovery of $d$-form factor density wave in the same material, showing the omnipresence of $d$ form factor density wave above and below the Fermi surface reconstruction. The relation between the $d$-form factor density wave and the pseudogap state is discussed. Second, I will describe our experiments on topological Kondo insulator $\mathrm{SmB_6}$ where spin-orbit coupling plays an important role in the strongly correlated electron system. I will present the spectroscopic evidence of Kondo hybridization based on a spectral decomposition technique. I will introduce a dimension reduction method in the fitting procedure to reduce the computation time by two order of magnitude. I will also discuss the possible quasiparticle interference patterns we discovered in $\mathrm{SmB_6}$.
Physics

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Kramar, John Adam Baldeschwieler John D. Baldeschwieler John D. "Scanning tunneling microscopy and spectroscopy of molybdenum disulphide /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-06132007-103520.

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16

Bigioni, Terry Paul. "Scanning tunneling microscopy and spectroscopy of passivated gold nanocrystals." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30537.

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Walton, John Moorcroft. "The acquisition, analysis and processing of Scanning Auger Microscopy (SAM) and Scanning Tunneling Microscopy (STM) data." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387184.

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Hackley, Jason. "A Liquid-Helium-Free High-Stability Cryogenic Scanning Tunneling Microscope for Atomic-Scale Spectroscopy." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19211.

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This dissertation provides a brief introduction into scanning tunneling microscopy, and then Chapter III reports on the design and operation of a cryogenic ultra-high vacuum scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noise level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Other performance characteristics such as thermal drift analysis and a cool-down analysis are reported. Scanning tunneling spectroscopy (STS) measurements based on the lock-in technique were also carried out and showed no detectable presence of noise from the CCC. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic-scale. A study of electron transport in single-walled carbon nanotubes (SWCNTs) was also conducted. In Chapter IV, STS is used to study the quantum-confined electronic states in SWCNTs deposited on the Au(111) surface. The STS spectra show the vibrational overtones which suggest rippling distortion and dimerization of carbon atoms on the SWCNT surface. This study experimentally connects the properties of well-defined localized electronic states to the properties of their associated vibronic states. In Chapter V, a study of PbS nanocrystals was conducted to study the effect of localized sub-bandgap states associated with surface imperfections. A correlation between their properties and the atomic-scale structure of chemical imperfections responsible for their appearance was established to understand the nature of such surface states. This dissertation includes both previously published/unpublished and co-authored material.

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余家訓 and Ka-fan Yu. "Scanning probe microscopy of porous silicon formation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31222110.

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Bergmann, Kirsten von. "Iron nanostructures studied by spin-polarised scanning tunneling microscopy." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971962464.

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21

Frey, Jeffrey T. "Quantum chemical studies of scanning tunneling microscopy and spectroscopy." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file Mb., 245 p, 2006. http://proquest.umi.com/pqdlink?did=1251856811&Fmt=7&clientId=79356&RQT=309&VName=PQD.

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Manson-Smith, Sacha Kinsey. "Investigation into scanning tunnelling luminescence microscopy." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366826.

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23

Bredekamp, Adriaan Hendrik. "New feedback control for a scanning tunneling microscope." Thesis, Cape Technikon, 1999. http://hdl.handle.net/20.500.11838/1129.

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Thesis (MTech(Electrical Engineering))--Cape Technikon, Cape Town,1999
This thesis describes the design and implementation of a new feedback controller for a scanning tunneling microscope or STM. The previous controller had several shortcomings when it came to the data throughput rate of the data acquisition system, the scan rate, and the way the data was stored and displayed. The initial investigation was done to determine the most cost effective way to implement the data acquisition system. Various approaches such as DSP systems, analogue systems and microcontroller systems were looked at. The investigation also looked at the best way to get the data from the Z directional control loop to the PC for displaying the data. The final choice was to use an ultra fast microcontroller for the control loop implementation and to change the DOS based software for Windows based software. The embedded system was divided into two parts. The first was the controller for the X and Y scan directions, and the second was for the Z scan direction. A digital PI control loop was implemented on the Z controller to control the height of the scan tip above the specimen surface. The microcontroller that was chosen for this was the Microchip PIC17c43. The data transfer to the PC was done with a PC-14 programmable digital input/output card. Two options for the implementation of the PC-14 software were considered. The first option was the software that was bundled with the card. This software proved to be very slow, so special device-driver-based software was developed to control the PC-14 card and the data transfer to and from the Pc. The PC software was implemented using Visual C++. Both the XY and the Z controllers proved to be working satisfactorily in the existing STM arrangement. It was discovered that the XY controller was overloaded with the many tasks that it has to perform, and a suitable alternative system to replace the XY controller is proposed. The selection of the PC that will be used for the data acquisition system is also discussed. It was found that this choice had a very big influence on the design of the final system because of the difference in PC bus design. Several proposals to increase the functionality of the PC software are also made.

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Jarasch, Markus. "Interfacing a Computer to a Scanning Tunneling Microscope." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/5047.

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A program was written in 'C' to control the functions of an already existing Scanning Tunneling Microscope (STM). A DAS-1601 data acquisition card (from Keithley Data Acquisition) was installed together with its drivers for 'C' on a computer with a 486-DX motherboard. The computer was interfaced to the electronics of the STM. Images taken of HOPG (highly oriented pyrolitic graphite) were of a reasonable quality and showed atomic resolution.

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Clayton, Garrett M. "Image-based output trajectory estimation in scanning tunneling microscopes /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/7121.

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Lutz, Martin Albert. "Scanning tunneling microscopy and anatomic force microscopy studies of epitaxial Si₁₋xGex films /." Zürich, 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10905.

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27

Martín, Malpartida Gemma. "Combined Transmission Electron Microscopy and In-Situ Scanning Tunneling Microscopy Characterization of Nanomaterials." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663184.

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The main goal of this thesis has been to apply in-situ Transmission Electron Microscopy (TEM) electrical measurements using a Scanning Tunneling Microscopy (STM) tip, combined with TEM imaging and spectroscopic techniques, in order to address the characterization of relevant nanomaterials. This system has not only been used to measure electrical properties, but also to carry out in-situ experiments with Joule heating and to apply mechanical stresses. A review of the different in-situ TEM techniques, their development over the years and their impact in the scientific community has been presented. Moreover, the instrumental used in this thesis, in particular, the TEM-STM system, has been described. In addition, two techniques for the preparation of specific samples for in-situ TEM-STM experiments have been presented: for nanostructured samples (2D materials, nanowires, etc), and for localized samples (devices, thin layers, bulk samples, etc). A gridcase that allows the use of conventional TEM grids in the TEM-STM system has been designed and fabricated in the context of this thesis. The use of this homemade gridase has allowed us to improve the experiments, offering more reproducibility and versatility. Finally, the calibration of the electrical measurements of the system has been carried out. Using the TEM-STM system, different type of nanostructures have been characterized during the present thesis, from 2D nanostructures, as the elucidation of the effects of electrical current through a single graphene oxide sheet, to functional devices, as the study of the ferroelectric and piezoelectric behavior of structures based on La2WO6, the study of the anisotropic electrical conductivity of GaInP CuPtB type ordering layers used for multijunction solar cells or the study of the conductive filament (CF) formation mechanism in three different Resistive random-access memory (ReRAM) devices. In summary, in-situ microscopy expands the horizons of the characterization and study of materials and, in particular, in the context of this thesis, an in-situ TEM-STM system has been used to electrically characterize samples from nanomaterials to functional devices.
En aquesta Tesi, s'ha emprat una tècnica de Microscopia Electrònica de Transmissió (TEM, Transmission Electron Microscopy en anglès) in-situ que permet realitzar mesures elèctriques utilitzant una sonda de microscòpia d'efecte túnel (STM, Scanning Tunneling Microscopy en anglès), tot combinant-la amb imatge TEM i tècniques d'espectroscòpia. A més, aquest sistema no només s'ha utilitzat per a mesurar les propietats elèctriques, sinó també per a dur a terme experiments in-situ amb escalfament per efecte Joule o aplicant una tensió mecànica a la superfície de la mostra. D'aquesta manera s'han pogut caracteritzar nanomaterials, des de nanoestructures 2D, estudiant l’efecte del pas de corrent a través d'un sol full d'òxid de grafè, fins a dispositius completament funcionals, com la caracterització piezoelèctrica i ferroelèctrica de capes primes d'òxids funcionals lliures de plom, l'estudi de l’anisotropia en la conductivitat d’estructures ternàries III-V ordenades utilitzades en cèl·lules solars tàndem multicapa i l'estudi amb TEM de la formació de filaments conductors (CF) i del mecanisme de commutació resistiva en tres dispositius ReRAM diferents. En els diferents capítols d'aquesta tesi s'ha donat resposta a problemes de ciència de materials amb l'ajut d'una tècnica de TEM in-situ tot combinant-la amb altres tècniques d'espectroscòpia i difracció. El desenvolupament d'aquesta tècnica ha permès caracteritzar les propietats del materials a nivell nano.

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28

Münks, Matthias [Verfasser]. "Scanning Tunneling Microscopy and Atomic Force Microscopy Measurements on Correlated Systems / Matthias Münks." Konstanz : Bibliothek der Universität Konstanz, 2017. http://d-nb.info/1142788520/34.

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Michnowicz, Tomasz [Verfasser]. "Scanning Tunneling Microscopy and Atomic Force Microscopy Investigation of Organic Molecules / Tomasz Michnowicz." Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/1193423538/34.

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30

Derro, David Joseph. "A scanning tunneling microscopy investigation of YBa₂Cu₃O₇-[subscript x] /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.

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吳誼暉 and Yee-fai Ng. "Optimization of etching parameters for STM tips and an STM study of SiC (0001) [square root]3 x [square root]3 reconstruction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B29797834.

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Ng, Yee-fai. "Optimization of etching parameters for STM tips and an STM study of SiC (0001) [square root]3 x [square root]3 reconstruction /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20567583.

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33

Mukhopadhyay, Rupa. "Scanning probe microscopy of functionalised metal surfaces." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343521.

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34

Quesenberry, Paul Elwin. "Scanning tunneling microscopy studies of a reactive interface, Ni/GaAs." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30779.

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35

Zhang, Lei [Verfasser]. "Sub-Kelvin scanning tunneling microscopy on magnetic molecules / Lei Zhang." Karlsruhe : KIT Scientific Publishing, 2019. http://d-nb.info/1190297515/34.

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36

Tjung, Steven Jason. "Scanning Tunneling Microscopy Studies of Adsorbates on Two-Dimensional Materials." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524055802947913.

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Moore, Steven Alan. "Scanning Tunneling Microscopy and Spectroscopy Measurements of Superconductor/Ferromagnet Hybrids." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/359662.

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Physics
Ph.D.
The focus of this thesis work is the study of the nanoscale electronic properties of magnetically coupled superconductor/ferromagnet hybrid structures using low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) under ultra-high vacuum conditions. There are a number of novel effects that can occur due to the non-homogenous magnetic field from the ferromagnet, which directly influence the global and local superconducting properties. These effects include the generation of vortices/anti-vortices by the non-uniform magnetic stray field, local modulations in the critical temperature, filamentary superconductivity close to the transition temperature, and superconducting channels that can be controlled by external magnetic fields. Prior to this dissertation the subject of superconductor/ferromagnet hybrid structures has been mainly studied using global measurements (such as transport and magnetization) or scanning probe techniques that are sensitive to the magnetic field. Scanning tunneling microscopy probes the local electronic density of states with atomic resolution, and therefore is the only technique that can study the emergence of superconductivity on the length scale of the coherence length. The novel results presented in this dissertation show that magnetically coupled superconductor/ferromagnet heterostructures offer the possibility to control and tune the strength and location of superconductivity and superconducting vortices, which has potential for promising technological breakthroughs in computing and power applications.
Temple University--Theses

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Goh, Kuan Eng Johnson Physics Faculty of Science UNSW. "Encapsulation of Si:P devices fabricated by scanning tunnelling microscopy." Awarded by:University of New South Wales. School of Physics, 2006. http://handle.unsw.edu.au/1959.4/27022.

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This thesis demonstrates the effective use of low temperature molecular beam epitaxy to encapsulate planar Si:P (phosphorus-in-silicon) devices lithographically patterned by scanning tunnelling microscopy (STM) without significant redistribution of the dopants. To achieve this goal, low temperature magnetotransport is used in combination with STM, Auger electron spectroscopy and secondary ion-mass spectrometry to analyse Si:P ??-doped samples fabricated under different doping and growth conditions. An important aspect of this project is the use of large 1 ?? 1 cm2 Si(001) samples which are about five times larger than standard STM samples. The larger sample size is necessary for post-STM fabrication lithography processes in a cleanroom but presents problems for preparing atomically clean surfaces. The ability to prepare clean and atomically flat Si(001) surfaces for STM lithography on such 1 ?? 1 cm2 samples is demonstrated, and it is shown that Si:P ??-doped layers fabricated on these surfaces exhibit complete electrical activation. Two dopant sources (gaseous PH3 and solid GaP source) were investigated to assess their compatibility with STM-lithography on the H:Si(001) surface. The findings show that while the PH3 and GaP sources result in near identical electrical qualities, only PH3 molecules are compatible with H-resist based lithography for controlled nano-scale doping. For achieving complete activation of the P dopants, it is shown that an anneal to ??? 350 ???C to incorporate P atoms into the Si surface prior to encapsulation is critical. While it is known that the presence of H during growth degrades the quality of Si epitaxy, investigations in this thesis indicate that it has no significant effect on dopant activation. Systematic studies performed to assess the impact of growth temperature recommend an encapsulation temperature of 250 ???C for achieving optimal electrical qualities with minimal dopant segregation. In addition, it is shown that rapid thermal anneals (RTAs) at temperatures < 700 ???C provide only marginal improvement in the electrical quality of Si:P ??-doped samples encapsulated at 250 ???C, while RTA temperatures > 700 ???C should be avoided due to the high probability of dopant redistribution. To elucidate the nature of 2D transport in Si:P ??-doped devices, a detailed analysis of the low temperature magnetotransport for Si:P ??-doped layers with doping densities in the range ??? 0.2 ??? 2 ?? 1014 cm???2 was carried out. Using conventional 2D theories for disordered systems, both weak localisation (WL) and electron-electron interactions (EEI) are shown to contribute almost equal corrections to the 2D conductivity. In particular, it is found that EEI can introduce a significant correction in the Hall coefficient RH (hence Hall density) especially in the low density/temperature regime and the need to correct for this when using the Hall density to estimate the activated electron density is highlighted. While the electronic mean free path in such highly doped ??-layers is typically < 10 nm making ballistic transport in these devices difficult to observe, the phase coherence length can extend to almost 200 nm at about 0.3???0.5 K for doping densities of ??? 1 ??? 2 ?? 1014 cm???2. Finally, the optimised encapsulation strategy developed in this thesis is applied to a 2D square device fabricated by STM. The device exhibits Ohmic conductivity with complete dopant activation. An analysis of its low temperature magnetotransport shows that the device behaves similarly to a Si:P ??-doped layer encapsulated under similar conditions, thus highlighting that the STM patterning process had no adverse effect on device quality.

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39

Zhao, He. "Probing the Strongly Correlated Quantum Materials with Advanced Scanning Tunneling Microscopy/Spectroscopy:." Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:108971.

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Thesis advisor: Ilija Zeljkovic
We used spectroscopic-imaging scanning tunneling microscopy (SI-STM) and spin-polarized STM (SP-STM) to unveil new electronic phenomena in several different quantum systems. We explored: (1) a potential topological superconductor heterostructure Bi₂Te₃/Fe(Te, Se), (2) high-Tc superconductors − Bi₂Sr₂CaCu₂O₈₊ₓ and Fe(Te, Se), and (3) doped spin-orbit Mott insulators Sr₂IrO₄ and Sr₃Ir₂O₇. In Bi₂Te₃/Fe(Te, Se), we observed superconductivity (SC) on the surface of Bi₂Te₃ thin film, induced by the iron-based superconductor substrate. By annealing the optimally-doped cuprate superconductor Bi₂Sr₂CaCu₂O₈₊ₓ, we drastically lowered the surface hole doping concentration to detect a unidirectional charge stripe order, the first reported charge order on an insulating (defined by the spectral gap with zero conductance spanning the Fermi level) cuprates surface. In the high-Tc SC Fe(Te, Se) single crystal, we found local regions of electronic nematicity, characterized by C₂ quasiparticle interference (QPI) induced by Fermi surface anisotropy and inequivalent spectral weight of dyz and dxz orbitals near Fermi level. Interestingly, the nematic order is locally strongly anti-correlated with superconductivity. Finally, utilizing SP-STM, we observed a short-range antiferromagnetic (AF) order near the insulator-metal transition (IMT) in spin-orbital Mott insulators Sr₂IrO₄ and Sr₃Ir₂O₇. The AF order inhomogeneity is found not to be strongly correlated with the charge gap. Interestingly, the AF order in the bi-layered Sr₃Ir₂O₇ shows residual memory behavior with temperature cycling. Overall, our work revealed new phenomena in a range of today’s most intriguing materials and set the stage for using SP-STM in other complex oxides
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics

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40

Harrell, Lee E. "Investigation of gold nanocrystals by ultrahigh vacuum cryogenic scanning tunneling microscopy." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/30030.

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41

Chi, Shun. "Scanning tunneling microscopy study of superconducting pairing symmetry : application to LiFeAs." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50598.

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Identifying the pairing symmetry is a crucial step towards uncovering the superconducting mechanism. The pairing symmetry and interactions leading to pairing in the iron-based high-temperature superconductors are under debate. In this thesis work, the pairing symmetry of LiFeAs, a stoichiometric superconductor in the iron-based family, is studied by scanning tunneling microscopy. The tunneling conductance spectrum in a defect-free region shows two nodeless superconducting gaps. In addition, a dip-hump above-gap structure was observed, indicating coupling between the superconducting carriers and bosonic modes. Defect bound states were measured for iron-site defects. The bound states are pinned to the gap edge of the small superconducting gap, consistent with theoretical predictions for a sign-changing pairing symmetry. Finally, the observed Bogoliubov quasiparticle interference associated with scattering from defects provides compelling evidence for an s+- pairing symmetry in LiFeAs.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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42

Maraghechi, Pouya, and University of Lethbridge Faculty of Arts and Science. "Dissociation of molecules on silicon surfaces studied by scanning tunneling microscopy." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2007, 2007. http://hdl.handle.net/10133/634.

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Dissociation of trichloroethylene (TCE) molecules on the Si(111)-7x7 and the Si(100)-2x1 surfaces was studied using STM. Though molecular adsorption may also be observed on the Si(111)-7x7 surface, dissociation is the dominant process. From the STM images acquired, products of dissociation were identified, namely chlorine atoms and dichlorovinyl groups. Dissociation of chlorine from the TCE molecule was confirmed by studying not just appearance in STM images but also from studies of tip-induced diffusion. Different binding configurations were proposed for the vinyl group on the Si (111)-7x7 and the Si(100)-2x1 surfaces. Site preference for each product of dissociation is reported on the Si(111)-7x7 surface. Dissociation of molecules such as ammonia, dimethylamine and methyl chloride on the Si(111)-7x7 and Si(100)-2x1 surfaces is reviewed. The field emission process is explained in detail. The usefulness of making field emission measurements is in evaluating the sharpness of STM tips.
xviii, 175 leaves : ill. (some col.) ; 29 cm

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Gyamfi, Mike [Verfasser]. "Scanning Tunneling Microscopy and Spectroscopy of Adatoms on Graphene / Mike Gyamfi." München : Verlag Dr. Hut, 2012. http://d-nb.info/1025821254/34.

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44

Leigh, David. "The electronic structure of carbon nanomaterials imaged by scanning tunneling microscopy." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427631.

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Scheil, Katharina [Verfasser]. "Scanning tunneling and atomic force microscopy of molecular switches / Katharina Scheil." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1151120391/34.

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46

Le, Toan T. "A Single-Stage Passive Vibration Isolation System for Scanning Tunneling Microscopy." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2272.

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Scanning Tunneling Microscopy (STM) uses quantum tunneling effect to study the surfaces of materials on an atomic scale. Since the probe of the microscope is on the order of nanometers away from the surface, the device is prone to noises due to vibrations from the surroundings. To minimize the random noises and floor vibrations, passive vibration isolation is a commonly used technique due to its low cost and simpler design compared to active vibration isolation, especially when the entire vibration isolation system (VIS) stays inside an Ultra High Vacuum (UHV) environment. This research aims to analyze and build a single-stage passive VIS for an STM. The VIS consists of a mass-spring system staying inside an aluminum hollow tube. The mass-spring system is comprised of a circular copper stage suspended by a combination of six extension springs, and the STM stays on top of the copper stage. Magnetic damping with neodymium magnets, which induces eddy currents in the copper conductor, is the primary damping method to reduce the vibrations transferred to the mass-spring system. FEMM and MATLAB® are used to model magnetic flux density and damping coefficients from eddy current effect, which will help determine the necessary damping ratios for the VIS. Viton, which demonstrates a high compatibility with vacuum environments, will also serve as a great damping material between joints and contacts for the housing tube. Viton will be modeled as a Mooney-Rivlin hyperelastic material whose material parameters are previous studied, and Abaqus will be used as a Finite Element Analysis software to study the Viton gaskets’ natural frequencies. The natural frequencies of the aluminum hollow tube will also be investigated through Abaqus.

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Ruggiero, Charles D. "Scanning Tunneling Microscopy Studies of Cu₂N Films." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259759686.

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Tumbleson, Ryan. "Investigation of a Robust Chiral Molecular Propeller Using Scanning Tunneling Microscopy." Ohio University Honors Tutorial College / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1556275268076303.

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Lang, Hans Peter. "Scanning tunneling microscopy of layered high temperature superconductors and carbon allotropes." [S.l.] : [s.n.], 1994. http://edoc.unibas.ch/diss/DissB_3306.

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Zhan, Gaolei. "Supramolecular networks and on surface polymerization studied by scanning tunneling microscopy." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD069/document.

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Ce travail présente les études, par microscopie à effet tunnel (STM) sous ultravide, d’une part de la formation de réseaux supramoléculaires, résultant de l’auto-assemblage des précurseurs organiques sur les surfaces Cu(111), Au(111), Si(111)-B et HOPG, et d’autre part, de l’étude de réactions chimiques sur les surfaces Cu(111), Au(111) et HOPG. Le premier chapitre décrit l’état de l’art des réseaux supramoléculaires ainsi que les réactions chimiques sur les surfaces. Le deuxième chapitre présente le dispositif expérimental et les théories sous-jacentes, ainsi que les préparations des substrats, de la pointe et la méthode de déposition des molécules.Le troisième chapitre présente les réseaux supramoléculaires formés par les dépositions des molécules fonctionnalisées par des atomes de brome ou d’azote sur les surfaces Cu(111) et Si(111)-B. Dans tous les cas, le rôle de la surface est prédominant lors de la formation des réseaux. Sur Cu(111), deux réseaux linéaires sont stabilisés par des interactions organométalliques entre les adatomes de Cu et les molécules organiques. Sur Si(111)-B, les réseaux formés sont commensurables avec la reconstruction √3 × √3 de la surface. En fonction de la compétition entre les interactions intermoléculaires et molécule-surface, les réseaux peuvent être 2D ou 1D.Le quatrième chapitre présent le premier exemple de polymérisation radicalaire sur une surface. Pour ce faire, quatre molécules de type arylalkyléthers et deux molécules arylalkanes furent synthétisées et déposées sur les surfaces de Cu (111), Au (111) et HOPG. Le mécanisme proposé pour cette réaction débute par une étape d’initialisation grâce à un processus de transfert inélastique d’électron tunnel (IET), générant des radicaux libres qui peuvent ensuite polymérisés par voie radicalaire sur la surface
This work deals with the investigation, by means of scanning tunneling microscopy under ultra-high vacuum, of supramolecular networks resulting from the self-assembly of organic precursors on surfaces such as Cu(111), Au(111), Si(111)-B and HOPG, but also the investigation of on-surface reactions. The first chapter describes the state-of-the-art of supramolecular networks and on-surface reactions on surfaces. The second chapter presents the experimental setup and theoretical concepts, as well as the preparations of the substrates, the probe tip and the method of molecular deposition.The third chapter presents the supramolecular networks formed by the depositions of molecules functionalized by bromine atoms or nitrogen atoms on the Cu(111) and Si(111)-B surfaces. For both cases, the surface plays a key role in the formation of networks: on Cu(111), the two linear networks are stabilized by metal-organic interactions between the Cu adatoms and the organic molecules; on Si(111)-B, the nanoarchitectures are commensurable with the reconstruction √3 × √3 of the surface. As function of the competition between the intramolecular and intermolecular interactions, the networks could be 2D or 1D.The fourth chapter presents the first example of on-surface radical polymerization, which is developed by the tandem synthetic method. For this end, four arylalkylether molecules and two arylalkane molecules are synthetized and deposited on different types of surfaces such as Cu (111), Au (111) and HOPG. The proposed mechanism suggests that this reaction is initialized by the inelastic electron tunneling (IET) process, which provides the free and stable radicals for the further on surface radical polymerization

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Dissertations / Theses on the topic 'Scanning tunneling microscopy'

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