REPORT: Calculation of the corrected time evolution of COVID-19 cases in the USA

In this challenging time where the novel COVID-19 pandemic is impacting the world, Dr. Dodabalapur analyzes the efficacy of the USA’s testing and reporting on the spread and impact on our country. Follow this link to read the full report: COVID Calculations Report

Abstract:
The time evolution of COVID-19 cases in the USA is highly inaccurate as a result of serious testing inefficiencies and biases, especially in the earlier stages. In this report, the corrected time evolution of such cases is reconstructed from death data, the average time between case recording and death in China, and the estimated overall death rate of COVID cases. The corrected time evolution in number of cases is compared to the officially reported case number evolution and a huge discrepancy exists between the two. The findings indicate that (i) the pandemic likely started earlier than though; (ii) the official number of cases is underreported by more than a factor of about 10; and (iii) the rate of increase in the calculated number of cases with time is slightly less compared to that of reported data.

Trapped Carrier Scattering: Cover of Annalen der Physik

Congratulations to Xiao Wang on publishing his paper “Trapped Carrier Scattering: Trapped Carrier Scattering and Charge Transport in High‐Mobility Amorphous Metal Oxide Thin‐Film Transistors” and making the cover of Annalen der Physik. In his publication, Xiao built upon the existing MTR model by including the impact of scattering and screening on extended-state transport.

Abstract
The multiple trap and release (MTR) model is extended to more completely and accurately describe charge transport in high‐mobility amorphous metal oxide thin‐film transistors (TFTs). In addition to trapping and release of charges, other scattering mechanisms that influence mobility are considered along with screening by free carriers. The mobility for each of the dominant scattering mechanisms is calculated using the Boltzmann transport equation (BTE) in the relaxation time approximation. It is found that trapped carriers very effectively scatter the charges that move in extended states. This type of scattering is unique to TFTs. Experimental data from high‐mobility amorphous metal oxide TFTs are compared with calculations with very good agreement. At high temperatures, scattering by longitudinal optical phonons and surface phonons becomes significant. This work represents the first successful combination of charge carrier scattering and the BTE with thermally activated MTR transport in a disordered semiconductor. Charge transport in amorphous metal oxide transistors is quantitatively described for the first time and the factors that influence the mobility at various temperatures and charge carrier densities are clearly described. This approach can be used for describing transport in several amorphous and polycrystalline semiconductors with significant disorder and trapping.

Enhanced Photoresponse in Metasurface-Integrated Organic Photodetectors

We are excited to highlight Xin Xu’s Nanoletters publication titled “Enhanced Photoresponse in Metasurface-Integrated Organic Photodetectors“, where he was able to demonstrate the first experimental use of phase-gradient metasurfaces to achieve relatively broadband enhancement of the efficiency of organic photodiodes.

Abstract
In this work, we experimentally demonstrate metasurface-enhanced photoresponse in organic photodetectors. We have designed and integrated a metasurface with broadband functionality into an organic photodetector, with the goal of significantly increasing the absorption of light and generated photocurrent from 560 up to 690 nm. We discuss how the metasurface can be integrated with the fabrication of an organic photodiode. Our results show large gains in responsivity from 1.5× to 2× between 560 and 690 nm.

https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b05261

APL Editor’s Choice: Polarization effects on charge transport in polymer field-effect transistors

Congratulations to Dr. Seohee Kim, whose publication titled “Polarization effects from the ambient and the gate dielectric on charge transport in polymer field-effect transistors” was selected by Applied Physics Letters (APL) as the Editor’s Choice. Using a FET device featuring high mobility polymer PDPP2T-TT-OD and a bilayer gate dielectric, Dr. Kim showed polarization induced trapping enhancement through a series of experiments that modified the conditions of the surface dielectric and introduced polar analytes to the atmosphere.

The full article can be found here: http://dx.doi.org/10.1063/1.4986439

(a) The chemical structure of PDPP2T-TT-OD and (b) the device structure of PDPP2T-TT-OD bilayer dielectric FETs.
Copyright © 2017 Author(s)

 

High-Performance Inkjet-Printed Transistors

Our recent work creating high-performance inkjet-printed carbon nanotube (CNT) transistors was summarized and highlighted by the Cockrell School of Engineering. The following is an excerpt from the article:

“We think our carbon nanontube transistor is an important step toward high-performing, low-cost printed electronics, such as smart labels, TV screens, sensors and green electronics,” said Dodabalapur, a professor in the Department of Electrical and Computer Engineering.

The team’s breakthrough is the development of a carbon nanotube transistor structure for inkjet printing with small channel lengths (by the standards of printed electronics), which allow electrons to travel along the length of the tube and conduct electricity faster. The device’s geometry, with channel lengths of 150-250 nanometers, is the shortest channel length reported thus far in which the active material is deposited by inkjet printing.

To view the full article, please click here.

Cover Feature of Small: Short Channel Field-Effect-Transistors with Inkjet-Printed Semiconducting Carbon Nanotubes

smll201570248-gra-0001-mThe cover feature of Small‘s November issue showcases high performance inkjet-printed short channel carbon nanotube field-effect-transistors (CNTFET) developed by our very own Seonpil Jang under the direction of Prof. Dodabalapur and in collaboration with fellow group members and partners in Northwestern University. The following is the abstract of the featured paper:

ABSTRACT: Short channel field-effect-transistors with inkjet-printed semiconducting carbon nanotubes are fabricated using a novel strategy to minimize material consumption, confining the inkjet droplet into the active channel area. This fabrication approach is compatible with roll-to-roll processing and enables the formation of high-performance short channel device arrays based on inkjet printing.

Read the full text for free on ResearchGate.

The selection of Seonpil’s publication as Small’s cover feature also made headlines in UT ECE’s department news. If you are interested in learning more about this and other works, please contact Seonpil (ultratft@gmail.com) or Prof. Dodabalapur (ananth@mail.utexas.edu).

Prof. Ananth Dodabalapur appointed as Editor-in-Chief of Flexible and Printed Electronics (FPE)

Featured in UT ECE department news, Prof. Dodabalapur was appointed as the Editor-in-Chief of Flexible and Printed Electronics (FPE).

FPE is the first journal dedicated to the reporting of research in all aspects of printed, plastic, flexible, stretchable, and conformable electronics and is perfectly placed to serve the needs of academic and industrial researchers alike.