Xinxin Yang

Plasmonic Metasurfaces with Conjugated Polymers for Flexible Electronic Paper in Color

A flexible electronic paper in full color is realized by plasmonic metasurfaces with conjugated polymers. An ultrathin large-area electrochromic material is presented which provides high polarization-independent reflection, strong contrast, fast response time, and long-term stability. This technology opens up for new electronic readers and posters with ultralow power consumption.

A 400-GHz Graphene FET Detector

This letter presents a graphene field effect transistor (GFET) detector at 400xa0GHz, with a maximum measured optical responsivity of 74xa0V/W, and a minimum noise-equivalent power of 130xa0pW/Hz1/2. This letter shows how the detector performance degrades as a function of the residual carrier concentration in the graphene channel, which is an important material parameter that depends on the quality of the graphene sheet and contaminants introduced during the fabrication process. In this work, the exposure of the graphene channel to liquid processes is minimized resulting in a low residual carrier concentration. This is in part, an important contributing factor to achieve the record high GFET detector performance. Thus, our results show the importance to use graphene with high quality and the importance to minimize contamination during the fabrication process.

A flexible graphene terahertz detector

We present a flexible terahertz (THz) detector based on a graphene field-effect transistor fabricated on a plastic substrate. At room temperature, this detector reveals voltage responsivity above 2u2009V/W and estimated noise equivalent power (NEP) below 3 nW/Hz1/2 at 487u2009GHz. We have investigated the effects of bending strain on DC characteristics, voltage responsivity, and NEP of the detector, and the results reveal its robust performance. Our findings have shown that graphene is a promising material for the development of THz flexible technology.

Test structures for evaluating Al 2 O 3 dielectrics for graphene field effect transistors on flexible substrates

We have developed a test structure for evaluating the quality of Al2O3 gate dielectrics grown on graphene for graphene field effect transistors on flexible substrates. The test structure consists of a metal/dielectric/ graphene stack on a PET substrate and requires only one lithography step for the patterning of the topside metal electrodes. Results from measurements of leakage current, capacitance and loss tangent are presented.

Characterization of Al2O3 gate dielectric for graphene electronics on flexible substrates

To ensure the high performance of graphene-based field effect transistors (GFETs) on flexible substrates, an uniform and manufacturable dielectric film with good electrical properties is needed. Thus, electrical characterization of the dielectric film on graphene on flexible substrates is very important for the development of flexible electronics based on GFETs. Here, we have fabricated and characterized parallel-plate capacitor test structures consisting of 35 nm thick Al₂O₃ dielectric film and with graphene as bottom electrode on polyethylene terephthalate (PET). It was found that the leakage current density in the Al₂O₃ film is less than 100 μA/cm² at 5 V, which allows for applying it as a gate dielectric in GFETs on flexible substrates. The extracted dielectric constant of the Al₂O₃ film is approx. 7.6, which is close to the bulk value and confirms the good quality of the Al₂O₃ film. Analysis indicates that the measured loss tangent, which is up to 0.2, is governed mainly by the dielectric loss in the Al₂O₃ and can be associated with defects from the Al₂O₃ film and the Al₂O₃/graphene interface. Our results will be used in further development of GFETs on flexible substrates.