Silicon-Based Ink Looks Good On Paper

Semiconducting inks are helping researchers print electronic devices on a growing range of low-cost substrates, including paper and plastic. Most of these inks rely on organic or metal oxide materials whose electronic properties are lacking in comparison with the grand pooh-bah of semiconductors—silicon. Scientists have previously developed silicon inks based on cyclopentasilane rings that can be converted to polysilane chains with ultraviolet light. Researchers can then bake those chains to form amorphous silicon at temperatures upward of 350 °C, but those temperatures can damage many inexpensive substrates. A team working at the Japan Advanced Institute of Science & Technology and Delft University of Technology, in the Netherlands, has now transformed cyclopentasilane inks into polycrystalline silicon at lower temperatures by using lasers (Appl. Phys. Lett. 2015, DOI: 10.1063/1.4916998). The team spread its ink on paper, irradiated it with UV light, and then hit it with pulsed laser light. The 28-nanosecond laser pulse contains enough energy to drive silicon crystallization but is brief enough to avoid damaging the paper. Although the team has not yet printed functional devices, the researchers believe the process could help create flexible, inexpensive sensors and radio-frequency communicators.