Session: Research Posters

Paper Number: 114211

114211 - A Novel Fabrication Method to Manufacture Two-Dimensional Flexible Devices 

With the rise of two-dimensional (2D) materials, their excellent optical, electronic, and thermal properties different from bulk materials make them increasingly widely studied and commercialized. Since the lateral dimension of 2D materials reaches the micrometer or even nanometer level, their research and application require placement of them on substrates, and there are chemical contaminations during the conventional transfer process. For the transfer of 2D materials, there have been some mature methods, such as dry transfer and wet transfer. In this work, we have developed a method to use the flexible substrate to directly pick up 2D materials. The flexible substrate that is used is Polydimethylsiloxane (PDMS). This method allows us to manufacture 2D flexible devices to the cleanest extreme and help us to understand the essential properties of 2D materials easier.

During the experimental process, a tape mechanical exfoliation method was used to produce monolayer graphene flakes. By searching for the monolayer graphene flakes and locating them in an optical microscope, a Raman microscope can be used to verify the thickness. The peak difference between the monolayer and other-thickness graphene can be verified. The intensity ratio of 2D (~2680 cm-1) and G (~1580 cm-1) peaks can determine the thickness. Monolayer graphene has a higher 2D peak and a lower G peak. If the 2D peak is much higher than the G peak, and the 2D peak can be fitted with one single clear curve, the sample flake is a monolayer. Bilayer graphene flake has G and 2D peaks with almost similar height intensity. The 2D peak has a tail and should be fitted with 2 curves. For bulk graphite, the G peak is much higher than the 2D peak, and the 2D peak is not as distinct and intense as that in monolayer graphene.

Polydimethylsiloxane (PDMS) was made by mixing the base and agent with a 10:1 ratio in weight. When PDMS is still in liquid condition, pour it over the graphene sample. Then the sample and PDMS was placed in a vacuum desiccator to remove bubbles in PDMS, followed by baking at 65 ℃ to solidify it. Graphene could be attached to PDMS better by leaving it overnight.

A manufacturing method by wet transfer was conducted as a comparison. Poly(vinyl alcohol) (PVA, ACS,) was used to be a sacrificial layer to complete the transfer process. PVA was coated on a 1.1×1.1 cm Si wafer using a spinning coater. A Poly(methyl methacrylate) (PMMA) was coated onto the PVA surface. Graphene flakes were exfoliated onto these substrates. The graphene/PMMA/PVA/Si was floated onto the water surface, leaving graphene/PMMA eventually and then transferred onto PDMS. PMMA was removed by acetone.

The quality of flexible graphene devices made by these two methods was characterized by Photoluminescence. It has shown that the novel PDMS direct transfer method provides the cleanest surface.

Presenting Author: Elham Easy Stevens Institute of Technology

Presenting Author Biography: PhD student at Stevens Institute of Technology.

Authors:

Elham Easy Stevens Institute of Technology
Xian Zhang Stevens Institute of Technology