Transfer of a Single Layer Graphene

• Autor(a) principal: Coroa, João Monteiro Ferreira de Mira
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/34363
• topic: Graphene; direct transfer; electrochemical delamination; ion intercalation; chemical vapour deposition; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

Graphene is a truly outstanding 2D material that holds the promise of revolutionizing the world with its many applications. All this expectation requires a high-quality graphene synthetized and transferred at large scale. Unfortunately, such industrial graphene is not currently feasible due the difficulty of the transfer even though its synthesis via chemical vapour deposition is becoming viable. Graphene is synthetized on a metal substrate, rendering graphene transfer an absolute necessity for use in electronic applications. A very recent transfer method, named direct transfer, has been proposed based on the electrochemical delamination that gives some hope in the matter. However, it is a method that still needs optimization by understanding its basis and by studying new target materials. In this sudy, the intercalation of different ions/molecules during the electrochemical delamination is discussed. According to literature, during the electrochemical delamination H2 bubbles produced at the cathode are responsible for delaminating the graphene. This work contradicts it, by saying that it is not the H2 bubbles but rather charged species of the electrolyte. A cathodic and anodic study was made, where solutions with ions that would undergo electrochemical reactions in and outside the electrochemical window (EW) of water were tested. This thesis concluded that only if the cation/anion reaction is outside the EW or that the charged species will not react that the graphene would delaminate. Sodium hydroxide is the standard electrolyte used although it originates sodium contamination in graphene but now, electrolytes such as tetramethylammonium hydroxide and chloride and tetraethylammonium hydroxide can be used instead, avoiding at last sodium contamination in graphene devices. Furthermore, this work also briefly discusses graphene adhesion to the target substrate and suggests, perhaps, hydrogen silesquioxane as target substrate due its capability of being transformed partially in SiO2 after curing and avoiding the doping caused by the previous target substrate used.