Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602371
Title: Mechanical manipulation of atoms and molecules on Si(100)
Author: Danza, Rosanna
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2013
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Abstract:
Manipulation of matter with atomic- or molecular-scale precision plays a central role in the field of nanotechnology. Given the continuous trend to miniaturization undergone by electronic devices in the last few decades, it provides the key to the bottom-up approach, a new concept of building devices for the technological applications of the future. Among the family of the scanning-probe techniques, scanning tunnelling microscope (STM) and atomic force microscope (AFM) have been widely used to image and manipulate individual atoms and molecules. For the research purposes of this thesis, STM is applied solely for imaging. Instead, the AFM technique, operated using the qPlus sensor, is mainly exploited in the framework of manipulation. The object of investigation is the Si(lOO)-2xl reconstructed surface. Although many of the properties of this type of silicon surface are well known, there exist both fundamental questions and potential applications that justify the interest around this material and the need for further research. Silicon surface is also considered an ideal substrate for molecular deposition and positioning, therefore it is used as the substrate on which to perform manipulation of C60 molecules. By using the qPlus AFM technique at cryogenic temperatures, protocols for reproducible controlled manipulation of individual silicon atoms and C60 molecules are described. Experimental results, carried out at zero applied bias, show the possibility to reversibly switch the orientation of silicon dimers through a purely mechanical mechanism based on the formation of a single covalent bond. Data also demonstrate the dependence of a flip event on both the local and non-local surface structure and that only correlated flipping takes place, since three consecutive dimers with the same buckled orientation are never observed after a single manipulation event. Regarding the imaging of C60 molecules, the variety of STM patterns highlights the fundamental role of a controlled functionalized tip in order to correctly interpret the molecular orientation, whereas constant-height AFM mode provides more detailed intramolecular features in comparison with the constant frequency-shift mode. AFM manipulation of C60 by means of a novel software tool appears viable, although a refinement of the technique would be beneficial in terms of reliable quantitative measurements. Furthermore, a novel technique for simultaneous STM (operated in the dynamic mode) and NC-AFM analysis is introduced, which appears valuable at separating geometric and electronic effects in scanning probe images.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.602371  DOI: Not available
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