Capacitores híbridos ultracompactos para caracterização de sistemas moleculares
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Data
2018-03-02
Autores
Petrini, Paula Andreia
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Universidade Estadual Paulista (Unesp)
Resumo
Conhecido como o ramo da ciência que utiliza camadas moleculares ativas para agregar novas funcionalidades a dispositivos, a eletrônica molecular apresenta propostas promissoras para o futuro. Uma classe de pequenas moléculas semicondutoras que vem sendo explorada devido ao seu potencial na fabricação de diferentes dispositivos é a das ftalocianinas de cobre (CuPc). Entretanto, poucos trabalhos presentes na literatura relatam a relação entre a características elétricas dos filmes orgânicos e sua espessura em nanoescala. Tal fato é explicado pela dificuldade na deposição de contatos elétricos sobre as camadas moleculares, dado que os métodos atualmente empregados podem vir a danificá-las. Nesse contexto, essa dissertação apresenta a fabricação de um capacitor hibrido ultracompacto (h-Cap) constituído por metal / óxido dielétrico / camada molecular / Metal como uma plataforma para acessar as propriedades elétricas de camadas moleculares. Utilizando como a camada metálica a combinação de filmes finos de ouro, titânio e cromo, óxido de alumínio (Al2O3) para o dielétrico e filmes finos de CuPc como camadas moleculares, os h-Caps são fabricados a partir da técnica roll-up. Para a deposição dos filmes metálicos foi utilizado a técnica de evaporação térmica por feixe de elétrons, a técnica de deposição por camada atômica foi utilizada para a deposição do Al2O3 e pôr fim a técnica de deposição por evaporação por filamento resistivo para as camadas moleculares de CuPc. As características geométricas e estruturais dos h-Caps foram obtidas utilizando microscópios ópticos e eletrônico de varredura. Para a caracterização topográfica do filme de CuPc foi utilizado um microscópio de força atômica. Quanto a caracterização elétrica, foram realizadas medidas de corrente-tensão nos dispositivos, com a finalidade de obter os parâmetros de transportes. A resposta dielétrica do dispositivo foi avaliada utilizando a técnica de espectroscopia de impedância de modo a fornecer medidas de capacitância-frequência, permitindo relacionar a espessura e a constante dielétrica do filme de CuPc (kCuPc). Para os filmes de CuPc entre 5 a 20 nm foi obtido o valor de kCuPc = 4,5 ± 0,5, mostrando que a técnica proposta é uma excelente alternativa para caracterização dielétrica de camadas ultrafinas de semicondutores orgânicos.
Known as the branch of science that uses active molecular layers to add new functionality to devices, molecular electronics presents promising proposals for the future. A class of small semiconductor molecules being exploited due to its potential in the manufacture of different devices is that of copper phthalocyanines (CuPc). However, few papers in the literature report the relationship between the electrical characteristics of organic films and their thickness at the nanoscale. This fact is explained by the difficulty in the deposition of electrical contacts on the molecular layers, since the methods currently used may damage them. In this context, this dissertation presents the fabrication of an ultracompact hybrid capacitor (h-Cap) consisting of metal / dielectric oxide / molecular layer / metal as a platform to access the electrical properties of molecular layers. Used as the metallic layer is the combination of thin films of gold, titanium and chromium, aluminum oxide for the dielectric and thin films of CuPc as molecular layers, the h-Cap are formed from the roll-up technique. For the deposition of the metallic films was used the thermal evaporation technique by electron beam, the technique of deposition by atomic layer was used for the deposition of Al2O3 and finally the technique of deposition by evaporation by resistive filament for the molecular layers of CuPc . The geometric characteristics of the h-Caps were obtained using optical and scanning electron microscopes. For the topographic characterization of the CuPc film was used to an atomic force microscope. As for the electrical characterization, current-voltage measurements, the h-Caps were evaluated as a function of CuPc thickness (5 to 50 nm) in order to extract their transport parameters. The dielectric response of the device was evaluated using the impedance spectroscopy technique to provide capacitance-frequency measurements, making it possible to relate the thickness and dielectric constant of the CuPc film (kCuPc). For the CuPc films between 5 and 20 nm, the value of kCuPc = 4.5 ± 0.5 was obtained, showing that the proposed technique is an excellent alternative for the dielectric characterization of ultrafine layers of organic semiconductors.
Known as the branch of science that uses active molecular layers to add new functionality to devices, molecular electronics presents promising proposals for the future. A class of small semiconductor molecules being exploited due to its potential in the manufacture of different devices is that of copper phthalocyanines (CuPc). However, few papers in the literature report the relationship between the electrical characteristics of organic films and their thickness at the nanoscale. This fact is explained by the difficulty in the deposition of electrical contacts on the molecular layers, since the methods currently used may damage them. In this context, this dissertation presents the fabrication of an ultracompact hybrid capacitor (h-Cap) consisting of metal / dielectric oxide / molecular layer / metal as a platform to access the electrical properties of molecular layers. Used as the metallic layer is the combination of thin films of gold, titanium and chromium, aluminum oxide for the dielectric and thin films of CuPc as molecular layers, the h-Cap are formed from the roll-up technique. For the deposition of the metallic films was used the thermal evaporation technique by electron beam, the technique of deposition by atomic layer was used for the deposition of Al2O3 and finally the technique of deposition by evaporation by resistive filament for the molecular layers of CuPc . The geometric characteristics of the h-Caps were obtained using optical and scanning electron microscopes. For the topographic characterization of the CuPc film was used to an atomic force microscope. As for the electrical characterization, current-voltage measurements, the h-Caps were evaluated as a function of CuPc thickness (5 to 50 nm) in order to extract their transport parameters. The dielectric response of the device was evaluated using the impedance spectroscopy technique to provide capacitance-frequency measurements, making it possible to relate the thickness and dielectric constant of the CuPc film (kCuPc). For the CuPc films between 5 and 20 nm, the value of kCuPc = 4.5 ± 0.5 was obtained, showing that the proposed technique is an excellent alternative for the dielectric characterization of ultrafine layers of organic semiconductors.
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Palavras-chave
H-Caps, Filmes finos de CuPc, Roll-Up, Nanomembranas, CuPc thin films, Roll-Up and nanomembranes