Pattern transfer and molecular chain orientation modulation by soft template during the nanoimprint lithography

Abstract

The templates for the nanoimprinting are fabricated usually through a series of steps, such as E-beam lithography, E-beam deposition, liftoff and reactive ion etching. Any mistake during these steps would lead to the failure of the fabrication, so the template is always expensive and difficult to make. Under this circumstance, it is really important to find an effective way to build the template. In this report, the patterned photoresist layer is used as a mother set of the pattern definition of the soft template polydimethylsiloxane. The grating structure of conjugated polymer poly (9,9-dioctylfluorene) film is successfully obtained by this template in the nanoimprinting process. In addition, we also find the anisotropy of molecular chain distribution. Both the transmission electron microscope diffraction pattern and the polarized absorption spectrum are used to prove that this anisotropy is induced by the molecular chain alignment, which would be really helpful in future applications in organic emission equipment. Moreover, this result is also applicable to the poly (9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-2,1',3-thiadiazole) film system.

Confinement-induced nanocrystal alignment of conjugated polymer by the soft-stamped nanoimprint lithography

“…From the SEM morphology characterization, the PFO nanogratings are duplicated precisely from the PDMS soft stamp. [14] All of the PFO nanogratings are uniform in height and width, and the residual layer thickness should be equal.…”

“…So that the soft stamp PDMS was obtained in this way, the detailed experiment condition could be found in Ref. [14].…”

“…In order to reduce the cost of the template fabrication, it is significant to develop a simply soft-stamped NIL for the pattern transfer fidelity and the orientation modulation of nanocrystals. [13,14] In addition, the comprehensive understanding of the alignment of nanocrystals under the softstamp-defined confinement is still unknown. Herein NIL with the soft stamp polydimethylsiloxane (PDMS) directly replicated from the polymethyl methacrylate (PMMA) nanogratings is used to discuss the influencing factors of the orientation degree of PFO nanocrystals.…”