{"id":71233,"date":"2024-11-13T09:40:18","date_gmt":"2024-11-13T07:40:18","guid":{"rendered":"https:\/\/www.iemn.fr\/?p=71233"},"modified":"2024-11-15T10:23:07","modified_gmt":"2024-11-15T08:23:07","slug":"epitaxie-van-der-waals-de-wse2","status":"publish","type":"post","link":"https:\/\/www.iemn.fr\/en\/a-la-une\/epitaxie-van-der-waals-de-wse2.html","title":{"rendered":"Thesis by Niels Chapuis: \"Van der Waals epitaxy of WSe2, HfSe2 and their heterostructure on a GaP(111)B substrate with a view to tunnel devices\" 15\/11 at 10.30 a.m."},"content":{"rendered":"<div id='layer_slider_1'  class='avia-layerslider main_color avia-shadow  avia-builder-el-0  el_before_av_heading  avia-builder-el-first  container_wrap sidebar_right'  style='height: 261px;'  ><div id=\"layerslider_58_z8u19nrh1f4a\" data-ls-slug=\"homepageslider\" class=\"ls-wp-container fitvidsignore ls-selectable\" style=\"width:1140px;height:260px;margin:0 auto;margin-bottom: 0px;\"><div class=\"ls-slide\" 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0;\npadding-bottom:4px;\n}\nbody .av-special-heading.av-k5dohoxw-c06c48d83f5c401c311220874005b612 .av-special-heading-tag .heading-char{\nfont-size:25px;\n}\n.av-special-heading.av-k5dohoxw-c06c48d83f5c401c311220874005b612 .av-subheading{\nfont-size:15px;\n}\n<\/style>\n<div  class='av-special-heading av-k5dohoxw-c06c48d83f5c401c311220874005b612 av-special-heading-h4  avia-builder-el-1  el_after_av_layerslider  el_before_av_hr  avia-builder-el-first  av-linked-heading'><h4 class='av-special-heading-tag'  itemprop=\"headline\"  >Niels Chapuis thesis: \"Van der Waals epitaxy of WSe2, HfSe2 and their heterostructure on a GaP(111)B substrate with a view to tunnel devices\".<\/h4><div class=\"special-heading-border\"><div class=\"special-heading-inner-border\"><\/div><\/div><\/div>\n\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-18u73nj-dad6a947580930e400fc42ba200e80f1\">\n#top .hr.av-18u73nj-dad6a947580930e400fc42ba200e80f1{\nmargin-top:5px;\nmargin-bottom:5px;\n}\n.hr.av-18u73nj-dad6a947580930e400fc42ba200e80f1 .hr-inner{\nwidth:100%;\n}\n<\/style>\n<div  class='hr av-18u73nj-dad6a947580930e400fc42ba200e80f1 hr-custom  avia-builder-el-2  el_after_av_heading  el_before_av_textblock  hr-left hr-icon-no'><span class='hr-inner inner-border-av-border-thin'><span class=\"hr-inner-style\"><\/span><\/span><\/div>\n<section  class='av_textblock_section av-jriy64i8-fd5f2e9d63bf552d6910d12f255eb26e'   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" >\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-13ewzjw-68e036126b913e5028f77311dc66b825\">\n.av_font_icon.av-13ewzjw-68e036126b913e5028f77311dc66b825{\ncolor:#bfbfbf;\nborder-color:#bfbfbf;\n}\n.av_font_icon.av-13ewzjw-68e036126b913e5028f77311dc66b825 .av-icon-char{\nfont-size:60px;\nline-height:60px;\n}\n<\/style>\n<span  class='av_font_icon av-13ewzjw-68e036126b913e5028f77311dc66b825 avia_animate_when_visible av-icon-style- avia-icon-pos-left avia-icon-animate'><span class='av-icon-char' aria-hidden='true' data-av_icon='\ue8c9' data-av_iconfont='entypo-fontello' ><\/span><\/span>\n<p><strong>\u00a0Niels Chapuis thesis<br \/>\n<\/strong><\/p>\n<p>Defence: 15 November 10:00<strong><br \/>\n<\/strong>IEMN Amphitheatre<\/p>\n<\/div><\/section>\n\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-jtefqx33-6db969b2e204313ebd62331ed4fc69ec\">\n#top .av_textblock_section.av-jtefqx33-6db969b2e204313ebd62331ed4fc69ec .avia_textblock{\nfont-size:15px;\n}\n<\/style>\n<section  class='av_textblock_section av-jtefqx33-6db969b2e204313ebd62331ed4fc69ec'   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" ><div  class='hr av-kjh3zw-4dff888f744b728a1aca9b3a0971493a hr-default  avia-builder-el-6  avia-builder-el-no-sibling'><span class='hr-inner'><span class=\"hr-inner-style\"><\/span><\/span><\/div>\n<h5><strong><span style=\"color: #800000;\">Jury<\/span><\/strong><\/h5>\n<p>Isabelle Berbezier: Research Director, CNRS-IM2NP, <i>rapporteur<\/i><\/p>\n<p>Matthieu Jamet: Director of Research, CEA-SPINTEC, <i>rapporteur<\/i><\/p>\n<p>Adrien Michon: Research Fellow, CNRS-CRHEA, <i>examiner<\/i><\/p>\n<p>Fabrice Oehler: Research Fellow, CNRS-C2N, <i>examiner<\/i><\/p>\n<p>Pascal Roussel: Research Director, CNRS-UCCS, <i>examiner<\/i><\/p>\n<p>Xavier Wallart: Research Director, CNRS-IEMN, <i>directeur de th\u00e8se<\/i><\/p>\n<h5><strong><span style=\"color: #800000;\">\u00a0<\/span><\/strong><\/h5>\n<h5>Summary:<\/h5>\n<p align=\"justify\"><span style=\"font-size: small;\">Two-dimensional materials (2MDs) offer unique properties mainly due to their structure<br \/>\ncrystallographic, composed of loosely coupled layers made up of one or more atomic planes where the<br \/>\natoms are covalently bonded. This specific structure means that there are no dangling bonds on the surface,<br \/>\nallowing the formation of heterostructures without the need to adapt the lattice parameter. Among the 2MDs, the<br \/>\nTransition metal dichalcogenides (DMTs), of formula MX2 (M=metal, X=Se, Te or S), are particularly well suited to the production of dichloromethane.<br \/>\ninteresting because some of them have band gaps ranging from 0.5 to 2 eV and offer a wide variety of properties.<br \/>\nstrip alignments. These characteristics make them promising candidates for the development of various<br \/>\ncomponents, particularly those based on inter-band tunneling. To date, most devices have<br \/>\nhave been manufactured using exfoliated or transferred layers or flakes, introducing significant problems<br \/>\nconcerning the quality of the interfaces and the reliability of the process.<\/span><\/p>\n<p align=\"justify\"><span style=\"font-size: small;\">Molecular beam epitaxial growth (MBE) has attracted a great deal of interest over the last decade.<br \/>\nfor the development of heterostructures based on DMTs, particularly on 2D substrates such as graphene,<br \/>\nh-BN or mica due to the natural van der Waals interface between the epitaxial layer and the substrate. In parallel,<br \/>\na new generation of heterojunctions has emerged, using 3D substrates such as Al2O3(0001) or AlN(0001),<br \/>\nunderlining the crucial importance of surface preparation prior to growth. The growth of a<br \/>\nmonolayer of WSe2 or that of a MoSe2\/WSe2 heterostructure were produced on a GaAs(111)B<br \/>\npreviously passivated under selenium, sparking new interest in the use of III-V semiconductors<br \/>\nas substrates for the development of devices based on DMTs. However, Monte Carlo simulations<br \/>\nhave highlighted the need for high growth temperatures in order to improve the grain size of DMTs, making<br \/>\nmakes GaP a suitable alternative to GaAs, thanks to its much greater thermal stability.<\/span><\/p>\n<p align=\"justify\"><span style=\"font-size: small;\">In this thesis work, we explore the growth by EJM of a few layers of WSe2 and HfSe2, as well as the growth by EJM of a few layers of WSe2 and HfSe2.<br \/>\nthat of the HfSe2\/WSe2 heterostructure on a GaP(111)B substrate. Each stage of the process was studied, with a<br \/>\nparticular attention to the preparation of the substrate, the crystalline quality of the layers obtained and their preservation<br \/>\nthe integrity of the heterojunction interface. We show that the use of a combination of hydrogen<br \/>\nand cracked phosphine in a three-step sequence to produce a smooth GaP(111)B surface<br \/>\nand completely deoxidised. To encourage the formation of a van der Waals quasi-gap between the substrate and the<br \/>\nDMT layer, the GaP(111)B surface is then selenium terminated. Using a combination of<br \/>\nexperimental techniques, we demonstrate the epitaxy of WSe2 and HfSe2 on GaP(111)B-Se, highlighting<br \/>\nthe crucial role of growth temperature and annealing under Se on the formation of polytypes, the properties<br \/>\nstructural and morphological properties. The resulting layers show clear epitaxial relationships with the substrate.<br \/>\nGaP(111)B and a well-defined van der Waals interface. WSe2 has p-type doping and an alignment of<br \/>\ntype II bands with the GaP substrate, while HfSe2 reveals a type I band alignment and a<br \/>\nheavily doped n. Finally, we discuss the challenges of developing a GaP\/HfSe2\/WSe2 heterostructure in<br \/>\ndue to the formation of a (W\/Hf)Sex compound, while the GaP\/WSe2\/HfSe2 stack showed results of<br \/>\npromising with a type II alignment and a clear p-n junction.<\/span><\/p>\n<p align=\"justify\"><strong>Abstract:<\/strong><\/p>\n<p align=\"justify\">Two-dimensional materials (2MDs) offer unique properties mainly due to their<br \/>\ncrystallographic structure, consisting of loosely coupled layers of one to a few atomic planes where the atoms are<br \/>\natoms are covalently bonded. This specific structure means that there are no dangling bonds at the surface,<br \/>\nallowing the formation of heterostructures without the need to adapt the lattice parameter. Among the 2MDs, the<br \/>\ntransition metal dichalcogenides (DMTs), of formula MX2 (M=metal, X=Se, Te or S), are particularly interesting because some of them<br \/>\ninteresting because some of them have band gaps ranging from 0.5 to 2 eV and offer a wide variety of band alignments.<br \/>\nof band alignments. These characteristics make them promising candidates for the development of various<br \/>\ncomponents, particularly those based on inter-band tunnelling. Until now, most devices have been fabricated using<br \/>\nbeen fabricated using exfoliated or transferred layers or flakes, introducing significant problems<br \/>\ninterface quality and process reliability.<br \/>\nOver the last decade, molecular beam epitaxial growth (MBE) has attracted considerable interest for the development of heterostructures.<br \/>\nin the development of DMT-based heterostructures, particularly on 2D substrates such as graphene,<br \/>\nh-BN or mica because of the natural van der Waals interface between the epitaxial layer and the substrate. In parallel,<br \/>\na new generation of heterojunctions has emerged, using 3D substrates such as Al2O3(0001) or AlN(0001),<br \/>\nunderlining the crucial importance of surface preparation prior to growth. For example, the growth of a<br \/>\nWSe2 monolayer or a MoSe2\/WSe2 heterostructure were grown on a GaAs(111)B<br \/>\nsurface previously passivated under selenium, generating new interest in the use of III-V<br \/>\nsemiconductors as substrates for the development of DMT-based devices. However, Monte Carlo simulations<br \/>\nsimulations have highlighted the need for high growth temperatures in order to improve the grain size of DMTs, making GaP a suitable alternative to GaC.<br \/>\nGaP a suitable alternative to GaAs, due to its significantly higher thermal stability.<br \/>\nIn this thesis, we explore the EJM growth of a few layers of WSe2 and HfSe2, as well as that of the HfSe2 heterostructure.<br \/>\nHfSe2\/WSe2 heterostructure on a GaP(111)B substrate. Each stage of the process was studied, with particular<br \/>\npreparation of the substrate, the crystalline quality of the layers obtained and the preservation of the<br \/>\nintegrity of the heterojunction interface. We show that the use of a combination of atomic hydrogen<br \/>\nand cracked phosphine in a three-step sequence results in a smooth and fully deoxidised GaP(111)B<br \/>\nsurface. To encourage the formation of a van der Waals quasi-gap between the substrate and the<br \/>\nDMT layer, the GaP(111)B surface is then selenium terminated. Using a combination of<br \/>\nof experimental techniques, we demonstrate the epitaxy of WSe2 and HfSe2 on GaP(111)B-Se, highlighting the crucial role of the<br \/>\ngrowth temperature and annealing under Se on polytype formation, structural and morphological properties.<br \/>\nmorphological properties. The resulting layers show clear epitaxial relationships with the<br \/>\nGaP(111)B substrate and a well-defined van der Waals interface. WSe2 exhibits p-type doping and a type II band alignment with the GaP(111)B substrate.<br \/>\nband alignment with the GaP substrate, while HfSe2 reveals a type I band alignment and a highly n-doped<br \/>\nhighly n-doped character. Finally, we discuss the challenges of developing a GaP\/HfSe2\/WSe2 heterostructure due to the formation of a GaP\/HfSe2\/WSe2 compound.<br \/>\nformation of a (W\/Hf)Sex compound, while the GaP\/WSe2\/HfSe2 stack shows promising results with a type II<br \/>\npromising results with a type II alignment and a clear p-n junction.<\/p>\n<\/div><\/section>","protected":false},"excerpt":{"rendered":"","protected":false},"author":20,"featured_media":71447,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,8,319,87,65,84],"tags":[],"class_list":["post-71233","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-a-la-une","category-actualites","category-actualites2022","category-agenda-en","category-agenda","category-agenda-en-en"],"_links":{"self":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/71233","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/comments?post=71233"}],"version-history":[{"count":0,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/posts\/71233\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media\/71447"}],"wp:attachment":[{"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/media?parent=71233"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/categories?post=71233"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.iemn.fr\/en\/wp-json\/wp\/v2\/tags?post=71233"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}