{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/31392"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/31392","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Atom-by-Atom Substitution of Transition Metals in GaAs and Visualization of Hole-Mediated Interactions","abstract":"The discovery of ferromagnetism in Mn doped InAs and GaAs has ignited interest in the development of semiconductor technologies based on the electron spin. A major hurdle remaining for realistic applications of ferromagnetic semiconductors, such as Ga(1-x)Mn(x)As, is their below room-temperature ferromagnetic transition temperature. Enhancing ferromagnetism in semiconductors requires understanding the mechanisms for interactions between magnetic dopants and identifying the circumstances that maximize ferromagnetic interactions. In this thesis, we present a novel atom-by-atom substitution technique with the scanning tunnelling microscope (STM) to controllably incorporate transition metal dopants into GaAs. We compare the electronic states of isolated single acceptors in an identical configuration - Ga sites in the top layer of a GaAs surface. The acceptor levels and anisotropic shape of the hole states for manganese, iron, cobalt; and zinc are determined with STM topography and spectroscopy. The manganese acceptor has a deeper acceptor level than the nonmagnetic zinc acceptor. The iron and cobalt acceptors have two acceptor levels that are complementary in their spatial distribution. We discuss the influence of the GaAs band structure and the p-d hybridization on the hole states. In addition, we probe the Mn acceptor in n-type and p-type GaAs to understand the role of tip-induced band bending in our experiments. We also present the first controlled atomic scale study of the interactions between isolated Mn impurities mediated by electronic states in GaAs. High-resolution STM measurements provide visualization of the GaAs electronic states that participate in Mn-Mn interactions. We quantify the interaction strengths between Mn pairs as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga(1-x)Mn(x)As structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples.","abstract_html":"The discovery of ferromagnetism in Mn doped InAs and GaAs has ignited interest in the development of semiconductor technologies based on the electron spin. A major hurdle remaining for realistic applications of ferromagnetic semiconductors, such as Ga(1-x)Mn(x)As, is their below room-temperature ferromagnetic transition temperature. Enhancing ferromagnetism in semiconductors requires understanding the mechanisms for interactions between magnetic dopants and identifying the circumstances that maximize ferromagnetic interactions. In this thesis, we present a novel atom-by-atom substitution technique with the scanning tunnelling microscope (STM) to controllably incorporate transition metal dopants into GaAs. We compare the electronic states of isolated single acceptors in an identical configuration - Ga sites in the top layer of a GaAs surface. The acceptor levels and anisotropic shape of the hole states for manganese, iron, cobalt; and zinc are determined with STM topography and spectroscopy. The manganese acceptor has a deeper acceptor level than the nonmagnetic zinc acceptor. The iron and cobalt acceptors have two acceptor levels that are complementary in their spatial distribution. We discuss the influence of the GaAs band structure and the p-d hybridization on the hole states. In addition, we probe the Mn acceptor in n-type and p-type GaAs to understand the role of tip-induced band bending in our experiments. We also present the first controlled atomic scale study of the interactions between isolated Mn impurities mediated by electronic states in GaAs. High-resolution STM measurements provide visualization of the GaAs electronic states that participate in Mn-Mn interactions. We quantify the interaction strengths between Mn pairs as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga(1-x)Mn(x)As structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples.","abstract_has_math":false,"creators":["Kitchen, Dale Spencer"],"institution":null,"degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Yazdani, Ali","Cooper, S. Lance","Martin, Richard M.","Junk, Thomas"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2006,"date_issued":"2006-11-28","date_published":"2006-11-28","updated_at":"2026-07-22T22:25:30Z","subjects":["atom-by-atom substitution","Mn doped GaAs","scanning tunnelling microscope (STM)","ferromagnetism"],"languages":["en"],"rights":["©2006 Kitchen"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["Q. 530.416 Tc6k","FILM 2006 K647"],"render_values":[{"text":"Q. 530.416 Tc6k","href":null,"code":true},{"text":"FILM 2006 K647","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/31392","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Yazdani, Ali","Cooper, S. 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A major hurdle remaining for realistic applications of ferromagnetic semiconductors, such as Ga(1-x)Mn(x)As, is their below room-temperature ferromagnetic transition temperature. Enhancing ferromagnetism in semiconductors requires understanding the mechanisms for interactions between magnetic dopants and identifying the circumstances that maximize ferromagnetic interactions. In this thesis, we present a novel atom-by-atom substitution technique with the scanning tunnelling microscope (STM) to controllably incorporate transition metal dopants into GaAs. We compare the electronic states of isolated single acceptors in an identical configuration - Ga sites in the top layer of a GaAs surface. The acceptor levels and anisotropic shape of the hole states for manganese, iron, cobalt; and zinc are determined with STM topography and spectroscopy. The manganese acceptor has a deeper acceptor level than the nonmagnetic zinc acceptor. The iron and cobalt acceptors have two acceptor levels that are complementary in their spatial distribution. We discuss the influence of the GaAs band structure and the p-d hybridization on the hole states. In addition, we probe the Mn acceptor in n-type and p-type GaAs to understand the role of tip-induced band bending in our experiments. We also present the first controlled atomic scale study of the interactions between isolated Mn impurities mediated by electronic states in GaAs. High-resolution STM measurements provide visualization of the GaAs electronic states that participate in Mn-Mn interactions. We quantify the interaction strengths between Mn pairs as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga(1-x)Mn(x)As structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples.","Submitted by Rachelle Ramer (rramer2@illinois.edu) on 2012-06-07T19:04:00Z No. of bitstreams: 1 2006_kitchen.pdf: 6678592 bytes, checksum: 254b92dfe353fbbbb73364699b8086c3 (MD5)","Made available in DSpace on 2012-06-07T19:04:00Z (GMT). No. of bitstreams: 1 2006_kitchen.pdf: 6678592 bytes, checksum: 254b92dfe353fbbbb73364699b8086c3 (MD5) Previous issue date: 2006-11-28","Restriction data tranferred 2014-07-01T11:34:58-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: thesis/dissertation","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Rachelle Ramer (rramer2@illinois.edu) on 2012-06-07T19:04:00Z Item is restricted indefinitely.","thesis/dissertation","U of I Only"]},{"key":"dc:title","label":"Title","values":["Atom-by-Atom Substitution of Transition Metals in GaAs and Visualization of Hole-Mediated Interactions"]}]}],"canonical_facts":{"dc:contributor":["Yazdani, Ali","Cooper, S. Lance","Martin, Richard M.","Junk, Thomas"],"dc:creator":["Kitchen, Dale Spencer"],"dc:date":["2006-11-28","2012-06-07T19:04:00Z","10000-01-01"],"dc:description":["The discovery of ferromagnetism in Mn doped InAs and GaAs has ignited interest in the development of semiconductor technologies based on the electron spin. A major hurdle remaining for realistic applications of ferromagnetic semiconductors, such as Ga(1-x)Mn(x)As, is their below room-temperature ferromagnetic transition temperature. Enhancing ferromagnetism in semiconductors requires understanding the mechanisms for interactions between magnetic dopants and identifying the circumstances that maximize ferromagnetic interactions. In this thesis, we present a novel atom-by-atom substitution technique with the scanning tunnelling microscope (STM) to controllably incorporate transition metal dopants into GaAs. We compare the electronic states of isolated single acceptors in an identical configuration - Ga sites in the top layer of a GaAs surface. The acceptor levels and anisotropic shape of the hole states for manganese, iron, cobalt; and zinc are determined with STM topography and spectroscopy. The manganese acceptor has a deeper acceptor level than the nonmagnetic zinc acceptor. The iron and cobalt acceptors have two acceptor levels that are complementary in their spatial distribution. We discuss the influence of the GaAs band structure and the p-d hybridization on the hole states. In addition, we probe the Mn acceptor in n-type and p-type GaAs to understand the role of tip-induced band bending in our experiments. We also present the first controlled atomic scale study of the interactions between isolated Mn impurities mediated by electronic states in GaAs. High-resolution STM measurements provide visualization of the GaAs electronic states that participate in Mn-Mn interactions. We quantify the interaction strengths between Mn pairs as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga(1-x)Mn(x)As structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples.","Submitted by Rachelle Ramer (rramer2@illinois.edu) on 2012-06-07T19:04:00Z No. of bitstreams: 1 2006_kitchen.pdf: 6678592 bytes, checksum: 254b92dfe353fbbbb73364699b8086c3 (MD5)","Made available in DSpace on 2012-06-07T19:04:00Z (GMT). No. of bitstreams: 1 2006_kitchen.pdf: 6678592 bytes, checksum: 254b92dfe353fbbbb73364699b8086c3 (MD5) Previous issue date: 2006-11-28","Restriction data tranferred 2014-07-01T11:34:58-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: thesis/dissertation","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Rachelle Ramer (rramer2@illinois.edu) on 2012-06-07T19:04:00Z Item is restricted indefinitely.","thesis/dissertation","U of I Only"],"dc:identifier":["Q. 530.416 Tc6k","FILM 2006 K647","http://hdl.handle.net/2142/31392"],"dc:language":["en"],"dc:rights":["©2006 Kitchen"],"dc:subject":["atom-by-atom substitution","Mn doped GaAs","scanning tunnelling microscope (STM)","ferromagnetism"],"dc:title":["Atom-by-Atom Substitution of Transition Metals in GaAs and Visualization of Hole-Mediated Interactions"],"dc:type":["Dissertation / Thesis","text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."]},"updated_at":"2026-07-22T22:25:30Z"}