Direct Laser Writing of Metal and Metal Oxide Patterns for Flexible and Memristive Electronic Components

Abstract

Growing interest in the fields of flexible electronics and AI are leading the development of new manufacturing techniques able to make computer hardware devices that can suite their unique needs. Research into these areas is stalled by the high cost of manufacturing putting rapid and low-cost manufacturing methods in high demand. Direct Laser Writing, as a novel manufacturing technique, has been shown to be able to produce flexible electronic devices rapidly and with the use of inexpensive raw materials. It works by treating a substrate coated in a metal ion precursor with focused laser irradiation. Where the laser interacts with the precursor organic reduction agents within the precursor are able to reduce the metal ions which then form nanoparticles that are then sintered to form interconnected nanoparticle networks. In this work direct laser writing is utilized to develop a manufacturing technique of novel flexible electronics for neuromorphic computing hardware. Direct laser writing of copper and copper patterns is used to study the relationship between applied laser energy and electrical properties of deposited patterns. Other metals are also studied. Anodic metals are not able to be fully reduced and are deposited as metal oxides. Cathodic metals are easily reduced and deposited as metals. Metals with intermediate reduction potentials can selectively be deposited as either metals or metal oxides. Deposition of metal alloys with homogenous composition is also demonstrated through the deposition of copper-nickel alloys. Memristor devices fabricated from Cu/Cu2O/Cu patterns are produced using direct laser writing. Planar patterns are fabricated and shown to have a high sensitivity to changing laser settings used to print the oxide region. Bipolar resistive switching is observed with setting and resetting occurring near +/- 0.7V, and ratios between the high and low resistance states being as high as 102 are achieved. Fabricated devices are shown to flexible and stable over long periods of time. Memristor based logic structures Including Boolean “And” and “Or” gates are fabricated in planar patterns from memristor pairs. Logic gates show signal processing in times as short as 300ns. Moderate signal degradation from the logic gates are noted at 9% and 21% in the “Or” gate and “And” gate respectively. Memristor crossbar arrays are also fabricated from Cu/Cu2O/Cu and Ag/Cu2O/Cu patterns. Their multiple resistance states are programmed and performances are compared. In summary Direct laser writing is demonstrated as a process that has promise as a method for producing flexible novel computer hardware. Further work is recommended to focus on identifying combinations of materials and laser settings that can further improve the consistency and performance of the direct laser writing fabricated memristor devices.