{"id":{"repo_id":"sheffield-hallam","oai_identifier":"oai:shura.shu.ac.uk:19373"},"canonical_url":"https://search.dev.ndltd.org/etd/sheffield-hallam/oai:shura.shu.ac.uk:19373","repository":{"repo_id":"sheffield-hallam","name":"Sheffield Hallam University","base_url":"https://shura.shu.ac.uk/cgi/oai2"},"display":{"title":"Metal-aluminium gallium nitride Schottky contacts formation.","abstract":"X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of various surface cleaning procedures on Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30. Results show that wet chemical etch in a HF solution followed by a 600°C in-situ annealing under ultra-high vacuum (UHV) is very effective in removing oxygen from the surface. Downward band bending of 0.87 eV and 0.99 eV also occurs between the solvents-treated and the annealed Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30, respectively.Increasing in-situ temperature annealing in increments of 100°C up to 600°C shows a re-ordering at the surface and subsurface with Ga and A1 moving deeper in the surface, whereas N goes to the topsurface. In addition, the Fermi level movement observed when increasing the temperature could be interpreted by the change in surface stoichiometry or by a creation of vacancies due to the ex-situ surface treatment which may, in turn, be activated/deactivated by temperature annealing. Atomic hydrogen clean (AHC) followed by 400°C in-situ UHV annealing is also found effective in removing O and C from Al[x]Ga[1]-[x]N surface (x = 0.20).The formation of Ag/Al[x]Ga[1]-[x]N (x = 0.20) and Ni/Al[x]Ga[1]-[x]N (x = 0.30) interfaces, where the substrate was subjected to HF etch followed by 600°C in-situ UHV anneal, has been studied by a combination of XPS, atomic force microscope (AFM), scanning tunneling microscope (STM) and current-voltage (I-V) measurements.XPS results suggest a layer-by-layer followed by islanding growth mode of Ag and Ni on Al[x]Ga[1]-[x]N. This is confirmed by the presence of metal islands at the metal-covered surfaces using AFM and in-situ STM. XPS investigation shows a more abrupt, well-defined Ag/Al[x]Ga[1]-[x]N interface compared to Ni/Al[x]Ga[1]-[x]N. Ag deposition on Al[x]Ga[1]-[x]N substrates causes upward band bending of 0.30 eV and 0.40 eV between the \"clean\" surface and the last metal deposition, for x = 0.20 and 0.30, respectively, while Ni induces downward band bending of 0.3 eV for x = 0.20. I-V measurements of Ag/Al[x]Ga[1]-[x]N (x = 0.30), where the substrate was cleaned using N[+] bombardment followed by 600°C annealing, yield a Schottky barrier height of 0.82 eV with ideality factor n = 1.21.XPS and I-V results on Ag/Al[x]Ga[1]-[x]N and Ni/Al[x]Ga[1]-[x]N are compared and discussed in terms of current models of Schottky barrier formation.","abstract_html":"X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of various surface cleaning procedures on Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30. Results show that wet chemical etch in a HF solution followed by a 600°C in-situ annealing under ultra-high vacuum (UHV) is very effective in removing oxygen from the surface. Downward band bending of 0.87 eV and 0.99 eV also occurs between the solvents-treated and the annealed Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30, respectively.Increasing in-situ temperature annealing in increments of 100°C up to 600°C shows a re-ordering at the surface and subsurface with Ga and A1 moving deeper in the surface, whereas N goes to the topsurface. In addition, the Fermi level movement observed when increasing the temperature could be interpreted by the change in surface stoichiometry or by a creation of vacancies due to the ex-situ surface treatment which may, in turn, be activated/deactivated by temperature annealing. Atomic hydrogen clean (AHC) followed by 400°C in-situ UHV annealing is also found effective in removing O and C from Al[x]Ga[1]-[x]N surface (x = 0.20).The formation of Ag/Al[x]Ga[1]-[x]N (x = 0.20) and Ni/Al[x]Ga[1]-[x]N (x = 0.30) interfaces, where the substrate was subjected to HF etch followed by 600°C in-situ UHV anneal, has been studied by a combination of XPS, atomic force microscope (AFM), scanning tunneling microscope (STM) and current-voltage (I-V) measurements.XPS results suggest a layer-by-layer followed by islanding growth mode of Ag and Ni on Al[x]Ga[1]-[x]N. This is confirmed by the presence of metal islands at the metal-covered surfaces using AFM and in-situ STM. XPS investigation shows a more abrupt, well-defined Ag/Al[x]Ga[1]-[x]N interface compared to Ni/Al[x]Ga[1]-[x]N. Ag deposition on Al[x]Ga[1]-[x]N substrates causes upward band bending of 0.30 eV and 0.40 eV between the "clean" surface and the last metal deposition, for x = 0.20 and 0.30, respectively, while Ni induces downward band bending of 0.3 eV for x = 0.20. I-V measurements of Ag/Al[x]Ga[1]-[x]N (x = 0.30), where the substrate was cleaned using N[+] bombardment followed by 600°C annealing, yield a Schottky barrier height of 0.82 eV with ideality factor n = 1.21.XPS and I-V results on Ag/Al[x]Ga[1]-[x]N and Ni/Al[x]Ga[1]-[x]N are compared and discussed in terms of current models of Schottky barrier formation.","abstract_has_math":false,"creators":["Boudjelida, Boumedienne."],"institution":"Sheffield Hallam University (United Kingdom).","degree_name":"phd","degree_level":"doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Simmonds, Mike","Clark, Simon","Evans-Freeman, Jan"],"committee_chairs":[],"committee_members":[],"year":2006,"date_issued":"2006","date_published":"2006","updated_at":"2026-07-24T06:31:14Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Simmonds, Mike","Clark, Simon","Evans-Freeman, Jan"]},{"key":"dc:creator","label":"Author","values":["Boudjelida, Boumedienne."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2006"]},{"key":"dc:date.issued","label":"Date","values":["2006"]},{"key":"dc:publisher.commercial","label":"Dc Publisher Commercial","values":["Sheffield Hallam University,"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department Not Provided."]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["Sheffield Hallam University (United Kingdom)."]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://shura.shu.ac.uk/19373/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["phd"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://shura.shu.ac.uk/19373/1/10694254.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of various surface cleaning procedures on Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30. Results show that wet chemical etch in a HF solution followed by a 600°C in-situ annealing under ultra-high vacuum (UHV) is very effective in removing oxygen from the surface. Downward band bending of 0.87 eV and 0.99 eV also occurs between the solvents-treated and the annealed Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30, respectively.Increasing in-situ temperature annealing in increments of 100°C up to 600°C shows a re-ordering at the surface and subsurface with Ga and A1 moving deeper in the surface, whereas N goes to the topsurface. In addition, the Fermi level movement observed when increasing the temperature could be interpreted by the change in surface stoichiometry or by a creation of vacancies due to the ex-situ surface treatment which may, in turn, be activated/deactivated by temperature annealing. Atomic hydrogen clean (AHC) followed by 400°C in-situ UHV annealing is also found effective in removing O and C from Al[x]Ga[1]-[x]N surface (x = 0.20).The formation of Ag/Al[x]Ga[1]-[x]N (x = 0.20) and Ni/Al[x]Ga[1]-[x]N (x = 0.30) interfaces, where the substrate was subjected to HF etch followed by 600°C in-situ UHV anneal, has been studied by a combination of XPS, atomic force microscope (AFM), scanning tunneling microscope (STM) and current-voltage (I-V) measurements.XPS results suggest a layer-by-layer followed by islanding growth mode of Ag and Ni on Al[x]Ga[1]-[x]N. This is confirmed by the presence of metal islands at the metal-covered surfaces using AFM and in-situ STM. XPS investigation shows a more abrupt, well-defined Ag/Al[x]Ga[1]-[x]N interface compared to Ni/Al[x]Ga[1]-[x]N. Ag deposition on Al[x]Ga[1]-[x]N substrates causes upward band bending of 0.30 eV and 0.40 eV between the \"clean\" surface and the last metal deposition, for x = 0.20 and 0.30, respectively, while Ni induces downward band bending of 0.3 eV for x = 0.20. I-V measurements of Ag/Al[x]Ga[1]-[x]N (x = 0.30), where the substrate was cleaned using N[+] bombardment followed by 600°C annealing, yield a Schottky barrier height of 0.82 eV with ideality factor n = 1.21.XPS and I-V results on Ag/Al[x]Ga[1]-[x]N and Ni/Al[x]Ga[1]-[x]N are compared and discussed in terms of current models of Schottky barrier formation."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Metal-aluminium gallium nitride Schottky contacts formation."]}]}],"canonical_facts":{"dc:contributor.advisor":["Simmonds, Mike","Clark, Simon","Evans-Freeman, Jan"],"dc:creator":["Boudjelida, Boumedienne."],"dc:date":["2006"],"dc:date.issued":["2006"],"dc:description.abstract":["X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of various surface cleaning procedures on Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30. Results show that wet chemical etch in a HF solution followed by a 600°C in-situ annealing under ultra-high vacuum (UHV) is very effective in removing oxygen from the surface. Downward band bending of 0.87 eV and 0.99 eV also occurs between the solvents-treated and the annealed Al[x]Ga[1]-[x]N surfaces for x = 0.20 and 0.30, respectively.Increasing in-situ temperature annealing in increments of 100°C up to 600°C shows a re-ordering at the surface and subsurface with Ga and A1 moving deeper in the surface, whereas N goes to the topsurface. In addition, the Fermi level movement observed when increasing the temperature could be interpreted by the change in surface stoichiometry or by a creation of vacancies due to the ex-situ surface treatment which may, in turn, be activated/deactivated by temperature annealing. Atomic hydrogen clean (AHC) followed by 400°C in-situ UHV annealing is also found effective in removing O and C from Al[x]Ga[1]-[x]N surface (x = 0.20).The formation of Ag/Al[x]Ga[1]-[x]N (x = 0.20) and Ni/Al[x]Ga[1]-[x]N (x = 0.30) interfaces, where the substrate was subjected to HF etch followed by 600°C in-situ UHV anneal, has been studied by a combination of XPS, atomic force microscope (AFM), scanning tunneling microscope (STM) and current-voltage (I-V) measurements.XPS results suggest a layer-by-layer followed by islanding growth mode of Ag and Ni on Al[x]Ga[1]-[x]N. This is confirmed by the presence of metal islands at the metal-covered surfaces using AFM and in-situ STM. XPS investigation shows a more abrupt, well-defined Ag/Al[x]Ga[1]-[x]N interface compared to Ni/Al[x]Ga[1]-[x]N. Ag deposition on Al[x]Ga[1]-[x]N substrates causes upward band bending of 0.30 eV and 0.40 eV between the \"clean\" surface and the last metal deposition, for x = 0.20 and 0.30, respectively, while Ni induces downward band bending of 0.3 eV for x = 0.20. I-V measurements of Ag/Al[x]Ga[1]-[x]N (x = 0.30), where the substrate was cleaned using N[+] bombardment followed by 600°C annealing, yield a Schottky barrier height of 0.82 eV with ideality factor n = 1.21.XPS and I-V results on Ag/Al[x]Ga[1]-[x]N and Ni/Al[x]Ga[1]-[x]N are compared and discussed in terms of current models of Schottky barrier formation."],"dc:format":["application/pdf"],"dc:identifier.uri":["https://shura.shu.ac.uk/19373/1/10694254.pdf"],"dc:language":["en"],"dc:publisher.commercial":["Sheffield Hallam University,"],"dc:publisher.department":["Department Not Provided."],"dc:publisher.institution":["Sheffield Hallam University (United Kingdom)."],"dc:relation.isreferencedby":["https://shura.shu.ac.uk/19373/"],"dc:title":["Metal-aluminium gallium nitride Schottky contacts formation."],"dc:type":["Thesis"],"dc:type.qualificationlevel":["doctoral"],"dc:type.qualificationname":["phd"]},"updated_at":"2026-07-24T06:31:14Z"}