In this study, we investigate a new technique to fabricate DNA-CTMA films with tunable properties. MAPLE is, for the first time, explored to deposit DNA-CTMA dielectric films on top of epitaxially grown graphene on silicon carbide (SiC) substrate. Silicon dioxide (SiO<sub>2</sub>) is commonly used as a gate insulator in graphene based field effect transistors (GFETs) in a top gate configuration. The high temperature deposition of SiO<sub>2</sub> on graphene is known to cause damage to the surface of the graphene leading to poor device operation. We propose an alternative gate insulator based on a bio-organic (DNA-CTMA) material processed and deposited at room temperature (RT) using MAPLE. Hall measurements run before and after DNA-CTMA deposition showed no change in the type of conductivity as well as charge carrier mobility.
Conventional guest-host optical limiting materials utilize either a liquid solvent or solid as the matrix for nonlinear absorbing chromophore dopants. Concentration gradients of the chromophore in the matrix can improve optical limiting performance. However, low viscosity liquid solutions can not retain a concentration gradient while polymer solid matrices damage at low laser fluences. We report on a novel approach of using an elastic polymer and viscoelastic gels for guest- host optimal limiting matrices. We achieve high bulk laser damage thresholds in the hosts and maintain a concentration gradient of the chromophore. By softening the epoxy we significantly enhance its bulk laser damage threshold. We characterize this effect by measuring the damage threshold as a function of viscoelastic properties. In addition, optical limiting was demonstrated in all the hosts doped with nonlinear phthalocyanine chromophores.
We demonstrate optical limiting in a unique guest-host system which uses neither the typical liquid or solid host. Instead, we dope a gelatin gel host with a water soluble Copper (II) phthalocyaninetetrasulfonic acid, tetrasodium salt (CuPcTs). We report on the gelatin's viscoelasticity, laser damage threshold, and self healing of this damage. The viscoelastic gelatin has mechanical properties quite different than a liquid or solid. Our laser measurements demonstrate that the single shot damage threshold of the undoped gelatin host increases with decreasing gelatin concentration. The gelatin also has a much higher laser damage threshold than a stiff acrylic. Unlike brittle solids, the soft gelatin self heals from laser induced damage. Optical limiting test also show the utility of a gelatin host doped with CuPcTs. The CuPcTs/gelatin matrix is not damaged at incident laser energies 5 times the single shot damage threshold of the gelatin host. However, at this high laser energy the CuPcTs is photo bleached at the beam waist. We report photo bleached sites by annealing the CuPcTs/gelatin matrix.