Wednesday, April 13, 2016

First Transistors Made Entirely of Nanocrystal ‘Inks’ for flexible electronics

University of Pennsylvania engineers have shown a new approach for making transistors by sequentially depositing their components in the form of liquid nanocrystal “inks.” Their technology could one day be used to develop chips for flexible and wearable applications. Here is the complete story by Penn State. Mark LaPedus at Semiconductor Engineering, puts it in the big picture with other developments for  Monolitic at CEA/Leti and Vertical Slit Transistor Based Integrated Circuits (VeSTICs) developed by Carnegie Mellon University in this article (thanks for sharing!)

A 1 nm thin Al2O3 deposited by ALD that is used to passivate the CdSe NC layer before depositing the source and drain electrodes to prevent delamination during the lithographic patterning.

Flexible transistors (Picture from Penn State)

The study by Cherrie Kagan's group at Penn State is a collaboration with research groups in South Korea at Yonsei and Korea University and has been published in Science "Exploiting the colloidal nanocrystal library to construct electronic devices", please find the abstract below.

Kagan's group at Penn State developed four nanocrystal inks that comprise the transistor, then deposited them on a flexible backing (Picture from Penn State).

Exploiting the colloidal nanocrystal library to construct electronic devices

Ji-Hyuk Choi, Han Wang, Soong Ju Oh, Taejong Paik, Pil Sung, Jo, Jinwoo Sung, Xingchen Ye, Tianshuo Zhao, Benjamin T. Diroll, Christopher B. Murray, Cherie R. Kagan

Science, vol. 352 no. 6282 205-208,

Synthetic methods produce libraries of colloidal nanocrystals with tunable physical properties by tailoring the nanocrystal size, shape, and composition. Here, we exploit colloidal nanocrystal diversity and design the materials, interfaces, and processes to construct all-nanocrystal electronic devices using solution-based processes. Metallic silver and semiconducting cadmium selenide nanocrystals are deposited to form high-conductivity and high-mobility thin-film electrodes and channel layers of field-effect transistors. Insulating aluminum oxide nanocrystals are assembled layer by layer with polyelectrolytes to form high–dielectric constant gate insulator layers for low-voltage device operation. Metallic indium nanocrystals are codispersed with silver nanocrystals to integrate an indium supply in the deposited electrodes that serves to passivate and dope the cadmium selenide nanocrystal channel layer. We fabricate all-nanocrystal field-effect transistors on flexible plastics with electron mobilities of 21.7 square centimeters per volt-second.