Barium strontium titanate (BST) and magnesium oxide (MgO) are common materials for electronic applications. Because of its low permittivity MgO can be used for passivation layers. In contrast to that the high-k BST allows for building up structures with high capacitances. Bandgap and antenna applications are feasible based on periodic BST/MgO structures, which are e.g. woodpile shaped. Furthermore BST can be used for filter or phase shifter applications due to the dielectric constant of BST that can be modified by the applied electrical field. To keep the applied voltage in a low range very fine structures are required. There are reports about the attempt to realize these very fine structures by screen printing or thin film deposition of BST and MgO. In this paper inkjet printing will be presented as an alternative method for the realization of such fine structured thick films.
BST particles with a diameter of 0.5 micron are deposited by inkjet printing with the additional advantage of creating two dimensional patterns in one layer. The resulting BST structures are embedded in MgO layers, which are inkjet printed as well.
The corresponding, own developed inks are based on an organic non-polar solvent. The particles are dispersed in the solvent by triple-roll-mill process and stabilized sterically. A solvent is found which is compatible to both kinds of particles as well as to the used substrates. Hence, the ink formulation differs only in the solid phase.
The printed structures are processed in two steps. First the MgO layer with the included holes is printed, the BST columns are deposited afterwards. The realization of fine MgO and BST structures is demonstrated. Printing of large areas with holes or channels as well as printing of columns with a high aspect ratio is investigated.
Numerous designs can be realized using inkjet printing. Any common passive devices as well as periodical structures with small dimensions and high aspect ratio are feasible.
ABSTRACTConducting polypyrrole (PPy) nanowire array was electrochemically fabricated by using microphase-separated block copolymer (PEOm-b-PMA(Az)n) thin film as an electrode template. Electropolymerization proceeds selectively through the perpendiculary oriented PEO nanocylindrical microdomains on an ITO electrode coated by the above polymer film. The length of the PPy nanowires was controllable in range of 10-120 nm by the thickness of the coated template film and the amount of passed charge. A 10 nm of diameter, 27 nm of periodicity, and 12 of aspect ratio of the crystalline PPy nanowires were successfully achieved. Selective removal of the template is also achieved simply by rinsing with solubility-controlled mixed solvent.
