NCN1 Flashcards

Question

Applications of colloidal PS spheres: colloidal lithography

Answer 1

-Eletrodos transparentes -Superficies auto limpantes -Estudo de celulas biologicas -Emprisionamento de luz

Answer 2

SAM's sao moleculas ordenadas formadas pela adsorção de um sufactante ativo numa superficie solida -Formam-se pela imersão do substrato numa solução contendo um ligante que é reativo com a superficie. -Self assembly a nivel molecular requer atração mutua entre moleculas. -Apenas possivel se afinidade quimica existe. -Formação de SAM´s é mais eficiente se ocorrer por reconhecimento molecular -A ordem é produzida por um processo quimico espontaneo de sintese à interface à medida que o sistema caminha para o equlibrio

Answer 3

Au, Ag, Cu -Não deve formar oxido à superficie que interfira com o processo de layering

Answer 4

-Tiois sulfitos e disulfitos -Deve ser capaz de ser adsorvido pela superficie do substrato

Answer 5

-Mascara de etching ou resist ultra fino -Modificação de propriedades de superficies

Answer 6

-Cabeça: afinidade com o substrato para induzir reações de adsorção, ligação muito energetica -Cauda: estrutura compacta causada por interações de van der waals -Fim ou grupo funcional: define as propriedades da monocamada(hidrofobico ou filico afinidade de ancorar com entidades biologicas)

Answer 7

-Puro self assembly apenas permite filmes finos -O processo tem de ser acompanhado por processos top-down para ter estruturas 2D ou 3D - As estruturas Top-down dão um "template" com um padrao desejado. as SAMS ficam assim confinadas a esses eespaços. * Patterns can be topographical structures (creation of physical boundaries to prevent self-assembly from spreading all over thecsurface), or areas with specific surface energy which either facilitate or prohibit the self-assembly.

Answer 8

Nanoparticulas dentro de cavidades: -Processo compicado -Uma vez na cavidade as forças eletroestaticas ou forças de vander waals vao segurar a montagem. -Poxde ser feito por dipcoating, é necessário controlar a velocidade com que se retira a amostra e a taxa de evaporação Nanoparticles trapped inside cavities:

Answer 9

-Substrato pode ser quimicamente modificado para reduzir a forca de capilaridade nomas zonas e acentuado noutras para que as particulas possam ser colocadas seletivamente.(change of surface hydrophobicity.) -SAMs podem ser usadas para alcançar alto contraste de hidrofobicidade

Answer 10

-Interação de maior alcance que self assembly quimica, surface tension ou van der waals -Base: 2 paarticulas carregadas inversamente vão se atrair. de forma semelhante uma particula vai ser atraida pelo eletrodo carregado inversamente -NP podem ser quimicamente modificadas ou cobertas para terem cargas de superficie -Processso pode combinar forças eletroestaticas ou de capilaridasde

Answer 11

* * Magnetic force is also long-ranged. * Basis: magnetic particles can be assembled onto a magnetized surface. * No need to apply and hold potential at numerous locations, no complex electrical connections. * Magnetic fields have greater selectivity than electrical fields and can permeate uninhibited through most mediums, particularly through liquids and gases. * Process mostly occurs for superparamagnetic colloidal particles (magnetization linearly related to applied magnetic field).

Answer 12

-Tem-se alumina porosa -Eletrodeposição do niquel -Dissolver a alumina -NW de Niquel!!! Exemplo de deposição eletroquímica

Answer 13

-Miniaturization, new device functionalities, on flexible substrates or on top of 3D shapes → Requires deposition techniques offering thickness control, uniformity, conformability, low temperature deposition -Uniformity -Conformable films

Answer 14

* Library of ALD materials nowadays is endless: metal oxides, nitrides, carbides, chalcogenides, metals, etc * Thin films are built up in cycles in which the surface is exposed to various vapor- or gas-phase species in alternating, separated doses. In each cycle, a submonolayer of material is deposited. * Precursor and co-reactant bring elements to the surface that lead to film growth * They react with the surface in a self-limiting way * Precursor+co-reactants react neither with themselves nor with the surface groups that they create * Purge steps remove excess precursor and/or co-reactant molecules or gaseous reaction products generated from surface reactions. Avoids reactions between precursor and co-reactant in gas phase * During each exposure step, precursor molecules react with the surface until all available surface sites are saturated. Surface saturation guarantees the self-limiting nature of ALD * Process Chemistry and conditions are chosen such that no reaction takes place once the surface is saturated. * Precursors are preferably overdosed so that process results become independent of potential slight variations in the amount of precursor supplied to the surface. * Surface chemistry governs film growth rather than a precise control of the process parameters such as precursor flow and partial pressure

Answer 15

-Regular -Multistep -Supercycle:In a supercycle, the steps of two normal ALD processes are combined where m cycles of the first process are followed by n cycles of the second process. The variables m and n can be chosen so as to obtain the desired composition and structure of the film.

Answer 16

-Saturation of both half-cycles leads to a characteristic amount of growth per cycle (GPC). I.e., a known and constant thickness is deposited per growth cycle and is represented by GPC. * In an ideal ALD process, GPC is independent of temperature

Answer 17

* It must be reactive towards the surface groups and leave reactive surface groups * It must not react with itself or with its surface-adsorbed species. * It should have a sufficiently high decomposition T (if decomposition occurs, self-limiting growth control may be lost) * Its reaction products should be volatile and neither easily adsorb to nor etch the growing film

Answer 18

Current metal sources are almost exclusively inorganic coordination complexes, i.e., a metal center surrounded by ligands.

Answer 19

--It must be reactive towards the surface groups and leave reactive surface groups --It must not react with itself or with its surface-adsorbed species. --It should have a sufficiently high decomposition T (if decomposition occurs, self-limiting growth control may be lost) --Its reaction products should be volatile and neither easily adsorb to nor etch the growing film

Answer 20

In general, co-reactants are all volatile, small molecules, such as elements, hydrides or alkyl compounds

Answer 21

Ellipsometry – refractive index as an indication of film density