{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/389492"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/389492","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Influence of van der Waals interfaces on electrical and optical properties of two-dimensional materials","abstract":"The interactions between two-dimensional (2D) materials and surrounding surfaces are critical for electronic devices. Interfacial effects become increasingly important as electronic devices continue to shrink in size. This thesis investigates the influence of van der Waals (vdW) interfaces on electrical and optical properties of 2D materials. I began by studying the nucleation and growth of indium and gold metal films on 2D materials such as molybdenum disulfide (MoS2) and graphene. Indium and gold metal films were chosen because previous research in the group has demonstrated that indium forms vdW interfaces with 2D materials while gold forms defective non-vdW interfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that indium metal deposition on MoS2 and graphene follows a 2D growth mechanism to form large grains. The layer-dependent study of MoS2 and graphene shows that increasing the number of layers reduces the influence of SiO2 substrate roughness so that the diffusivity and diffusion length of indium atoms increase and the activation energy for indium atom diffusion decreases - as reflected in the fivefold decrease in nucleation density (~12 μm-2 ). The influence of vdW interface between graphene and ferroelectric CuInP2S6 (CIPS) was also explored. Graphene field effect transistors (FETs) with CIPS as the top gate were studied. Polarisation-induced hysteresis in CIPS-gated graphene FETs was observed – indicating the realisation of ferroelectric FETs (FeFETs). We show that interfacial remote doping influences the macroscopic polarisation and performance of CIPS-based graphene FeFETs. Finally, Raman and photoluminescence (PL) measurements on MoS2 with indium metal film of thicknesses ranging from 2 to 25 nm were performed. The results suggest that the vdW gap between indium and MoS2 leads to a strong enhancement of Raman and PL signals. Strong Raman enhancement was also observed in graphene. In the absence of vdW gap with gold film, the plasmon-mediated enhancement of Raman and PL signals was not observed.","abstract_html":"The interactions between two-dimensional (2D) materials and surrounding surfaces are critical for electronic devices. Interfacial effects become increasingly important as electronic devices continue to shrink in size. This thesis investigates the influence of van der Waals (vdW) interfaces on electrical and optical properties of 2D materials. I began by studying the nucleation and growth of indium and gold metal films on 2D materials such as molybdenum disulfide (MoS2) and graphene. Indium and gold metal films were chosen because previous research in the group has demonstrated that indium forms vdW interfaces with 2D materials while gold forms defective non-vdW interfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that indium metal deposition on MoS2 and graphene follows a 2D growth mechanism to form large grains. The layer-dependent study of MoS2 and graphene shows that increasing the number of layers reduces the influence of SiO2 substrate roughness so that the diffusivity and diffusion length of indium atoms increase and the activation energy for indium atom diffusion decreases - as reflected in the fivefold decrease in nucleation density (~12 μm-2 ). The influence of vdW interface between graphene and ferroelectric CuInP2S6 (CIPS) was also explored. Graphene field effect transistors (FETs) with CIPS as the top gate were studied. Polarisation-induced hysteresis in CIPS-gated graphene FETs was observed – indicating the realisation of ferroelectric FETs (FeFETs). We show that interfacial remote doping influences the macroscopic polarisation and performance of CIPS-based graphene FeFETs. Finally, Raman and photoluminescence (PL) measurements on MoS2 with indium metal film of thicknesses ranging from 2 to 25 nm were performed. The results suggest that the vdW gap between indium and MoS2 leads to a strong enhancement of Raman and PL signals. Strong Raman enhancement was also observed in graphene. In the absence of vdW gap with gold film, the plasmon-mediated enhancement of Raman and PL signals was not observed.","abstract_has_math":false,"creators":["Ghani, Maheera Abdul"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Chhowalla, Manish"],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-02-28","date_published":"2025-02-28","updated_at":"2026-07-22T22:24:06Z","subjects":["materials","electronic devices","Two-dimensional (2D) materials","van der Waals","Interfaces","Optical properties","Electrical properties","metal films"],"languages":["eng"],"rights":[],"rights_urls":["https://www.repository.cam.ac.uk/bitstreams/d98ab32a-14e4-45de-906d-322cad3643d1/download","http://purl.org/NET/rdflicense/allrightsreserved"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.121354","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Chhowalla, Manish"]},{"key":"dc:creator","label":"Author","values":["Ghani, Maheera Abdul"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2025-02-28"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/389492"]},{"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":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["materials","electronic devices","Two-dimensional (2D) materials","van der Waals","Interfaces","Optical properties","Electrical properties","metal films"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://www.repository.cam.ac.uk/bitstreams/d98ab32a-14e4-45de-906d-322cad3643d1/download","http://purl.org/NET/rdflicense/allrightsreserved"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.121354"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://www.repository.cam.ac.uk/bitstreams/1056a0c5-a592-46c5-a3aa-03091446b251/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The interactions between two-dimensional (2D) materials and surrounding surfaces are critical for electronic devices. Interfacial effects become increasingly important as electronic devices continue to shrink in size. This thesis investigates the influence of van der Waals (vdW) interfaces on electrical and optical properties of 2D materials. I began by studying the nucleation and growth of indium and gold metal films on 2D materials such as molybdenum disulfide (MoS2) and graphene. Indium and gold metal films were chosen because previous research in the group has demonstrated that indium forms vdW interfaces with 2D materials while gold forms defective non-vdW interfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that indium metal deposition on MoS2 and graphene follows a 2D growth mechanism to form large grains. The layer-dependent study of MoS2 and graphene shows that increasing the number of layers reduces the influence of SiO2 substrate roughness so that the diffusivity and diffusion length of indium atoms increase and the activation energy for indium atom diffusion decreases - as reflected in the fivefold decrease in nucleation density (~12 μm-2 ). The influence of vdW interface between graphene and ferroelectric CuInP2S6 (CIPS) was also explored. Graphene field effect transistors (FETs) with CIPS as the top gate were studied. Polarisation-induced hysteresis in CIPS-gated graphene FETs was observed – indicating the realisation of ferroelectric FETs (FeFETs). We show that interfacial remote doping influences the macroscopic polarisation and performance of CIPS-based graphene FeFETs. Finally, Raman and photoluminescence (PL) measurements on MoS2 with indium metal film of thicknesses ranging from 2 to 25 nm were performed. The results suggest that the vdW gap between indium and MoS2 leads to a strong enhancement of Raman and PL signals. Strong Raman enhancement was also observed in graphene. In the absence of vdW gap with gold film, the plasmon-mediated enhancement of Raman and PL signals was not observed."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["8d2b23cdf70d43644a27297252caa8a7","87eda9de84448d1f82354d60eee3eb5f"]},{"key":"dc:title","label":"Title","values":["Influence of van der Waals interfaces on electrical and optical properties of two-dimensional materials"]}]}],"canonical_facts":{"dc:contributor.advisor":["Chhowalla, Manish"],"dc:creator":["Ghani, Maheera Abdul"],"dc:date.issued":["2025-02-28"],"dc:description.abstract":["The interactions between two-dimensional (2D) materials and surrounding surfaces are critical for electronic devices. Interfacial effects become increasingly important as electronic devices continue to shrink in size. This thesis investigates the influence of van der Waals (vdW) interfaces on electrical and optical properties of 2D materials. I began by studying the nucleation and growth of indium and gold metal films on 2D materials such as molybdenum disulfide (MoS2) and graphene. Indium and gold metal films were chosen because previous research in the group has demonstrated that indium forms vdW interfaces with 2D materials while gold forms defective non-vdW interfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results show that indium metal deposition on MoS2 and graphene follows a 2D growth mechanism to form large grains. The layer-dependent study of MoS2 and graphene shows that increasing the number of layers reduces the influence of SiO2 substrate roughness so that the diffusivity and diffusion length of indium atoms increase and the activation energy for indium atom diffusion decreases - as reflected in the fivefold decrease in nucleation density (~12 μm-2 ). The influence of vdW interface between graphene and ferroelectric CuInP2S6 (CIPS) was also explored. Graphene field effect transistors (FETs) with CIPS as the top gate were studied. Polarisation-induced hysteresis in CIPS-gated graphene FETs was observed – indicating the realisation of ferroelectric FETs (FeFETs). We show that interfacial remote doping influences the macroscopic polarisation and performance of CIPS-based graphene FeFETs. Finally, Raman and photoluminescence (PL) measurements on MoS2 with indium metal film of thicknesses ranging from 2 to 25 nm were performed. The results suggest that the vdW gap between indium and MoS2 leads to a strong enhancement of Raman and PL signals. Strong Raman enhancement was also observed in graphene. In the absence of vdW gap with gold film, the plasmon-mediated enhancement of Raman and PL signals was not observed."],"dc:format.checksum.md5":["8d2b23cdf70d43644a27297252caa8a7","87eda9de84448d1f82354d60eee3eb5f"],"dc:identifier.doi":["https://doi.org/10.17863/CAM.121354"],"dc:identifier.uri":["https://www.repository.cam.ac.uk/bitstreams/1056a0c5-a592-46c5-a3aa-03091446b251/download"],"dc:language":["eng"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/389492"],"dc:rights":["https://www.repository.cam.ac.uk/bitstreams/d98ab32a-14e4-45de-906d-322cad3643d1/download","http://purl.org/NET/rdflicense/allrightsreserved"],"dc:subject":["materials","electronic devices","Two-dimensional (2D) materials","van der Waals","Interfaces","Optical properties","Electrical properties","metal films"],"dc:title":["Influence of van der Waals interfaces on electrical and optical properties of two-dimensional materials"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:06Z"}