Recent interest in novel physical properties of reduced dimensional systems is spurred by the advance of investigation methods at the nanoscale. Understanding bottom-up techniques for the growth of nanomaterials with novel physical, chemical, and mechanical properties require specialized investigation tools.
I am presenting a novel design and performance of an ultra high vacuum scanning tunneling microscope (STM) that allows for large scale (8 mum x 8 mum), fast scanning (3 s for a 100 A x 100 A frame), and atomically resolved studies of reduced dimensional systems on metallic surfaces. The STM proved excellent performance, allowing for variable temperature (100 K to 700 K) and high resolution (< 2 pm at 300 K) structural and dynamical studies on surfaces, as shown by the STM study of the general types of self-assembly processes on strained metallic interfaces.
With this new instrument, I performed a complete experimental investigation of the misfit dislocation network of one atom thick Ag films on Ru(0001) and of the restructuring induced by molecular sulfur adsorption when S filled Ag vacancy island are formed. The experiments suggest that the mechanism through which hundreds of Ag atoms are rear-ranging themselves following S deposition is driven by a process of threading dislocation pair annihilation and glide. The experimental observations are explained via an atomistic model, which is based on first-principles interaction parameters. I have found that the self-assembly process is driven by stress relaxation in the Ag film.
While the first part of my thesis is focused on the structural properties of low-dimensional metallic systems and instrumentation methods needed to access the nano-scale, in the secand part I investigated a novel low-energy electronic excitation of a metallic surface. I am presenting the first experimental measurement of an acoustic surface plasmon on metal surfaces. The experiment was performed using electron energy loss spectroscopy on Be(0001). This new mode is a collective excitation of the surface electrons. This discovery goes against the traditional wisdom that on metal surfaces only regular (optical) surface plasmons can exist. First-principles calculations show that this mode is caused by the coexistence of a partially occupied surface state band with the underlying bulk electrons.
","abstract_html":"<p>Recent interest in novel physical properties of reduced dimensional systems is spurred by the advance of investigation methods at the nanoscale. Understanding bottom-up techniques for the growth of nanomaterials with novel physical, chemical, and mechanical properties require specialized investigation tools.</p><p>I am presenting a novel design and performance of an ultra high vacuum scanning tunneling microscope (STM) that allows for large scale (8 mum x 8 mum), fast scanning (3 s for a 100 A x 100 A frame), and atomically resolved studies of reduced dimensional systems on metallic surfaces. The STM proved excellent performance, allowing for variable temperature (100 K to 700 K) and high resolution (< 2 pm at 300 K) structural and dynamical studies on surfaces, as shown by the STM study of the general types of self-assembly processes on strained metallic interfaces.</p><p>With this new instrument, I performed a complete experimental investigation of the misfit dislocation network of one atom thick Ag films on Ru(0001) and of the restructuring induced by molecular sulfur adsorption when S filled Ag vacancy island are formed. The experiments suggest that the mechanism through which hundreds of Ag atoms are rear-ranging themselves following S deposition is driven by a process of threading dislocation pair annihilation and glide. The experimental observations are explained via an atomistic model, which is based on first-principles interaction parameters. I have found that the self-assembly process is driven by stress relaxation in the Ag film.</p><p>While the first part of my thesis is focused on the structural properties of low-dimensional metallic systems and instrumentation methods needed to access the nano-scale, in the secand part I investigated a novel low-energy electronic excitation of a metallic surface. I am presenting the first experimental measurement of an acoustic surface plasmon on metal surfaces. The experiment was performed using electron energy loss spectroscopy on Be(0001). This new mode is a collective excitation of the surface electrons. This discovery goes against the traditional wisdom that on metal surfaces only regular (optical) surface plasmons can exist. First-principles calculations show that this mode is caused by the coexistence of a partially occupied surface state band with the underlying bulk electrons.</p>","abstract_has_math":false,"creators":["Diaconescu, Bogdan"],"institution":null,"degree_name":"Doctor of Philosophy","degree_level":"Dissertation","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Karsten Pohl"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2007,"date_issued":"2007-01-01T08:00:00Z","date_published":"2007-01-01T08:00:00Z","updated_at":"2026-07-24T05:22:19Z","subjects":["Physics","Condensed Matter"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholars.unh.edu/dissertation/369","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Karsten Pohl"]},{"key":"dc:creator","label":"Author","values":["Diaconescu, Bogdan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics","Condensed Matter"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholars.unh.edu/dissertation/369"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Recent interest in novel physical properties of reduced dimensional systems is spurred by the advance of investigation methods at the nanoscale. Understanding bottom-up techniques for the growth of nanomaterials with novel physical, chemical, and mechanical properties require specialized investigation tools.
I am presenting a novel design and performance of an ultra high vacuum scanning tunneling microscope (STM) that allows for large scale (8 mum x 8 mum), fast scanning (3 s for a 100 A x 100 A frame), and atomically resolved studies of reduced dimensional systems on metallic surfaces. The STM proved excellent performance, allowing for variable temperature (100 K to 700 K) and high resolution (< 2 pm at 300 K) structural and dynamical studies on surfaces, as shown by the STM study of the general types of self-assembly processes on strained metallic interfaces.
With this new instrument, I performed a complete experimental investigation of the misfit dislocation network of one atom thick Ag films on Ru(0001) and of the restructuring induced by molecular sulfur adsorption when S filled Ag vacancy island are formed. The experiments suggest that the mechanism through which hundreds of Ag atoms are rear-ranging themselves following S deposition is driven by a process of threading dislocation pair annihilation and glide. The experimental observations are explained via an atomistic model, which is based on first-principles interaction parameters. I have found that the self-assembly process is driven by stress relaxation in the Ag film.
While the first part of my thesis is focused on the structural properties of low-dimensional metallic systems and instrumentation methods needed to access the nano-scale, in the secand part I investigated a novel low-energy electronic excitation of a metallic surface. I am presenting the first experimental measurement of an acoustic surface plasmon on metal surfaces. The experiment was performed using electron energy loss spectroscopy on Be(0001). This new mode is a collective excitation of the surface electrons. This discovery goes against the traditional wisdom that on metal surfaces only regular (optical) surface plasmons can exist. First-principles calculations show that this mode is caused by the coexistence of a partially occupied surface state band with the underlying bulk electrons.
"]},{"key":"dc:title","label":"Title","values":["Self -assembly on strained metallic interfaces, and, Novel collective excitations on metal surfaces"]}]}],"canonical_facts":{"dc:contributor":["Karsten Pohl"],"dc:creator":["Diaconescu, Bogdan"],"dc:description.abstract":["Recent interest in novel physical properties of reduced dimensional systems is spurred by the advance of investigation methods at the nanoscale. Understanding bottom-up techniques for the growth of nanomaterials with novel physical, chemical, and mechanical properties require specialized investigation tools.
I am presenting a novel design and performance of an ultra high vacuum scanning tunneling microscope (STM) that allows for large scale (8 mum x 8 mum), fast scanning (3 s for a 100 A x 100 A frame), and atomically resolved studies of reduced dimensional systems on metallic surfaces. The STM proved excellent performance, allowing for variable temperature (100 K to 700 K) and high resolution (< 2 pm at 300 K) structural and dynamical studies on surfaces, as shown by the STM study of the general types of self-assembly processes on strained metallic interfaces.
With this new instrument, I performed a complete experimental investigation of the misfit dislocation network of one atom thick Ag films on Ru(0001) and of the restructuring induced by molecular sulfur adsorption when S filled Ag vacancy island are formed. The experiments suggest that the mechanism through which hundreds of Ag atoms are rear-ranging themselves following S deposition is driven by a process of threading dislocation pair annihilation and glide. The experimental observations are explained via an atomistic model, which is based on first-principles interaction parameters. I have found that the self-assembly process is driven by stress relaxation in the Ag film.
While the first part of my thesis is focused on the structural properties of low-dimensional metallic systems and instrumentation methods needed to access the nano-scale, in the secand part I investigated a novel low-energy electronic excitation of a metallic surface. I am presenting the first experimental measurement of an acoustic surface plasmon on metal surfaces. The experiment was performed using electron energy loss spectroscopy on Be(0001). This new mode is a collective excitation of the surface electrons. This discovery goes against the traditional wisdom that on metal surfaces only regular (optical) surface plasmons can exist. First-principles calculations show that this mode is caused by the coexistence of a partially occupied surface state band with the underlying bulk electrons.
"],"dc:identifier":["https://scholars.unh.edu/dissertation/369"],"dc:subject":["Physics","Condensed Matter"],"dc:title":["Self -assembly on strained metallic interfaces, and, Novel collective excitations on metal surfaces"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy"]},"updated_at":"2026-07-24T05:22:19Z"}