Millisecond Ordering of Block-Copolymer Films via Photo-Thermal Gradients
Majewski, P.W.; Yager, K.G. "Millisecond Ordering of Block-Copolymer Films via Photo-Thermal Gradients" ACS Nano 2015
We demonstrate a remarkable new method for ordering self-assembling thin-films of block-copolymers. Using a focused laser-line, we generate an extremely localized thermal zone. The high temperatures and sharp thermal gradients greatly enhance ordering kinetics. Simultaneously, we can align and pattern the block-copolymer morphology.
For the promise of self-assembly to be realized, processing techniques must be developed that simultaneously enable control of the nanoscale morphology, rapid assembly, and, ideally, the ability to pattern the nanostructure. Here, we demonstrate how photo-thermal gradients can be used to control the ordering of block-copolymer thin films. Highly localized laser heating leads to intense thermal gradients, which induce a thermophoretic force on morphological defects. This increases the ordering kinetics by at least 3 orders-of-magnitude, compared to conventional oven annealing. By simultaneously exploiting the thermal gradients to induce shear fields, we demonstrate uniaxial alignment of a block-copolymer film in less than a second. Finally, we provide examples of how control of the incident light-field can be used to generate prescribed configurations of block-copolymer nanoscale patterns.