Laser direct writing of silicon nanowires and graphene

James Mitchell, Purdue University

Abstract

Nanomaterials hold tremendous value as the future building blocks of many important applications ranging from high speed electronics and biomedical diagnostic tools to power storage and generation, and both nanowires and graphene have been touted as successors to conventional materials in many of these fields. Despite all this promise however, efficient and highly controllable ways to manufacture and synthesize these materials still remains a challenge. Here we demonstrate a laser direct writing method in combination with chemical vapor deposition to controllably synthesize and accurately place silicon nanowires with diameters as narrow as 60 nm. The λ/6.5 feature size is enabled by utilizing laser induced periodic surface structures from ultrafast short pulse laser irradiation that scatters from the silicon deposited on the substrate surface causing interference between the incident laser beam and the scattered radiation. By selecting the appropriate parameters, single, double, or triple nanowires are written simultaneously. These nanowires are then fabricated into high performance chemical sensors, field effect transistors, and diodes. Using a similar laser direct write process we also synthesize single layer graphene directly on an insulating surface from a solid carbon source. We then characterized the physical and electrical properties of this graphene and identify areas for future improvement of the process. Laser direct writing of both nanowires and graphene simplifies the synthesizing of these materials with a large variety of uses from energy generation to microelectronics, and enhances the position and placement control. By increasing the throughput of laser direct write by performing the process in parallel it can add a significant tool for the rapid prototyping of nano-electronics.

Degree

Ph.D.

Advisors

Xu, Purdue University.

Subject Area

Mechanical engineering|Nanotechnology|Optics

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