Morphology of Polythiophene and Polyphenyl Films Produced via Surface Polymerization by Ion-Assisted Deposition

Abstract

Conducting polymer films are grown by either mass-selected or non-mass-selected, hyperthermal thiophene ions coincident on a surface with a thermal beam of organic monomers of either alpha-terthiophene (3T) or p-terphenyl (3P) neutrals. Previous experiments verified polymerization of both 3T and 3P by 200 eV C(4)H(4)S(+) during surface polymerization by ion-assisted deposition (SPIAD). A wide variety of structures are observed by scanning electron microscopy to form in the SPIAD polythiophene and polyphenyl films. These structures include microscale islands, lamellar structures, fractal-like growth patterns, and nanoscale crystallites. Some of the deposited films diffract X-rays while others show electron micrographs of crystallites. The variation of these patterns with deposition conditions clearly indicate that ion-induced polymerization mediates film morphology through control of ion energy and ion/neutral ratio. Furthermore, these ion-assisted events mediate important thermal processes such as sublimation.

A Low Band Gap Conjugated Polymer for Supercapacitor Devices

“…Despite the two different substrates, the material always exhibits a highly porous open structure having a nonuniform polymer grain size in the micrometer and submicrometer range that provides a large and effective electrolyte-accessible surface area helping the fast charge/discharge dynamics. The polymer synthesized on Pt grid shows the presence of a few fibril-like structures, also observed in other organic polymers. ,, However, the materials exhibits mostly a grapelike structure.

8 SEM pictures of the electrosynthesized polymer on (a) ITO coated slide, (b) Pt grid.

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Mechanistic Studies of Surface Polymerization by Ion-Assisted Deposition

“…Figure illustrates that the optimal ion/neutral ratios are 1/100 for ion energies of 100 eV, 1/75 for 50 eV, and 1/50 for 25 eV. This is likely due to the reduced ion-induced desorption of 3T oligomers at lower ion energies, which requires less 3T deposition . All SPIAD films are stable in vacuum for over 4 h, a period during which pure 3T films are observed to completely sublime.…”

“…This is likely due to the reduced ioninduced desorption of 3T oligomers at lower ion energies, which requires less 3T deposition. 10 All SPIAD films are stable in vacuum for over 4 h, a period during which pure 3T films are observed to completely sublime. The C/S ratio is around four for all SPIAD and direct ion deposited films (data not shown), which is consistent with thiophene-containing species.…”

“…3,4 One method that has been developed to achieve this result is surface polymerization by ion-assisted deposition (SPIAD) in which conducting polymer thin films are grown on substrates by the simultaneous deposition of hyperthermal polyatomic ions and thermal neutrals in vacuum. [5][6][7][8][9][10] In this study, the deposition of mass-selected beams of thiophene ions on thin films of R-terthiophene (3T) oligomers on a silicon substrate are carried out in experiments and density functional theory-molecular dynamics (DFT-MD) simulations to determine the dominant mechanisms responsible for the SPIAD process and assess their relative importance. Both neutral and positively charged systems are considered in the simulations in order to quantify the effect of charge on the results.…”

“…Polymers such as polythiophene have generated considerable interest in recent years because of their combination of electrical conductivity, low cost, low weight, and high processability. This combination of properties has led to a wide range of applications in electronic and optical devices including light-emitting diodes, field-effect transistors, photovoltaics, sensor films, recording materials, and rechargeable batteries. , To optimize the performance of these devices, it is necessary to develop processing methods that can control thin-film chemistry and morphology on the nanoscale. , One method that has been developed to achieve this result is surface polymerization by ion-assisted deposition (SPIAD) in which conducting polymer thin films are grown on substrates by the simultaneous deposition of hyperthermal polyatomic ions and thermal neutrals in vacuum. − In this study, the deposition of mass-selected beams of thiophene ions on thin films of α-terthiophene (3T) oligomers on a silicon substrate are carried out in experiments and density functional theory−molecular dynamics (DFT−MD) simulations to determine the dominant mechanisms responsible for the SPIAD process and assess their relative importance. Both neutral and positively charged systems are considered in the simulations in order to quantify the effect of charge on the results.…”