Fine electrically-conductive patterns of silver nanoparticles ink have been laser printed using the laser-induced forward transfer (LIFT) technique. LIFT is a technique that offers the possibility of printing patterns with high spatial resolution from a wide range of materials in solid or liquid state. Influence of drying the ink film, previous to its transfer, on the printed droplet morphology is discussed. The laser pulse energy and donor-receiver substrate separation were systematically varied and their effects on the transferred droplets were analyzed. The use of an intermediate titanium dynamic release layer was also investigated and demonstrated the possibility of a better control of both the size and shape of the printed patterns. Conditions have been determined for printing flat-top droplets with sharp edges. 21 µm width silver lines with 80 nm thickness have been printed with a smooth convex profile. Electrical resistivities of the transferred patterns are only 5 times higher than the bulk silver.
Résumé. La potentialité d'une technique d'écriture directe assistée par laser est démontrée dans le cadre de la fabrication d'un composant électronique de base, le transistor à effet de champ. L'impression de pixels à partir de divers matériaux susceptibles d'intervenir dans la fabrication d'un OFET (conducteur, semi-conducteur, diélectrique...) qu'ils soient organiques ou non, a été réalisée sous l'irradiation à 355 nm d'un laser picoseconde. L'éjection et le dépôt de la matière ont été étudiés comparativement au type de matériau utilisé: métal, polymère ou oligomère sous formes solides, encre à nanoparticules métalliques sous forme liquide. Des informations sur la morphologie des pixels obtenus, sur leur résolution spatiale, sur leur épaisseur ainsi que sur leurs propriétés d'adhésion ont été déduites d'analyses par microscopie optique, électronique à balayage (MEB) et/ou à force atomique (AFM). L'utilisation d'une couche intermédiaire servant à piéger le rayonnement incident et donc à protéger le matériau à imprimer a également été abordée.
Abstract.With the goal to study complex organic thin film transistor (OTFT) architecture, thin films of semiconductors and of metallic materials have been laser printed. The n-type copper hexa deca fluoro phthalocyanine (F 16 CuPc) and p-type copper phthalocyanine (CuPc) semiconductors have been used to form the active layers. The materials have been successively transferred onto a receiver substrate by laser pulses in the picosecond regime. The latter substrate has formed the gate and the dielectric of the transistor. The three materials have been then combined in a multilayer stack prepared by the successive depositions of the materials by thermal evaporation under vacuum and then laser have been printed in a single step.
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