Volume 95 Issue 31 | p. 10 | Concentrates
Issue Date: July 31, 2017

Photolithography method creates complex patterns using inorganic nanocrystals as colorful inks

Procedure leads to patterned thin films of metals, semiconductors, and oxides without the need for organic photoresists
Department: Science & Technology
News Channels: Materials SCENE, Nano SCENE
Keywords: nanomaterials, inorganic chemistry, lithography, photolithography
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This true-color image of a parrot was created photolithographically from three types of quantum dots capped with light-sensitive ligands.
Credit: Science
This picture of a bird was drawn via a lithography process using light-sensitive inorganic nanocrystals as colorful inks.
 
This true-color image of a parrot was created photolithographically from three types of quantum dots capped with light-sensitive ligands.
Credit: Science

Controlling the surface chemistry of inorganic nanocrystals, also known as quantum dots, has enabled researchers to devise a photolithography process for making all-inorganic patterned thin films. Unlike conventional lithography, the new technique requires no polymeric photoresists. The method, which requires fewer steps and could reduce fabrication costs for electronics, has been applied to metal, semiconductor, magnetic, and oxide nanocrystals (Science 2017, DOI: 10.1126/science.aan2958). Conventional lithography provides electronics manufacturers with a procedure for patterning semiconductors such as silicon wafers, forming millions of circuit elements simultaneously. The patterning relies on a stencil-like photoresist that masks the semiconductor and responds to light, becoming either soluble or insoluble in a given solvent, depending on the specifics of the process. A team led by the University of Chicago’s Dmitri V. Talapin has built that photosensitivity directly into quantum dots by functionalizing them with light-sensitive capping ligands. The researchers apply colloidal quantum dot solutions as colorful inks to various substrates, then expose select regions of the films to UV light, making those regions insoluble in a chosen solvent. Then they wash away the unexposed, soluble regions. For example, the team has drawn complex patterns from solutions of red CdSe/ZnS, green InP/ZnS, and blue ZnSe/ZnS quantum dots all capped with NH4CS2N3 ligands, which decompose under UV light.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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