NanoCube: A Low-Cost, Modular, and High-Performance Embedded System for Adaptive Fabrication and Characterization of Nanogaps

This paper presents an embedded modular system, NanoCube, able to repeatedly fabricate a pair of nanometric terminal probes (nanogaps) using the electromigration-induced break junction and capable to characterize them for low-cost molecular electronic devices and biomolecular sensing. NanoCube implements a flexible control loop which predicts both temperature and current and efficiently manages the electrical stimulation applied to ad hoc PCB cartridges, including a silicon chip with gold wire probes to be electromigrated. The modular and flexible system embeds the core circuits devoted to nanogap fabrication, signal conditioning and measurement, and the microprogrammed subsystems. NanoCube runs a real-time Linux operating system, with a fully customizable electromigration algorithm which considers fabrication history to adaptively improve performance. After 250 fabrication runs the system is shown to be able to fabricate nanogaps under 3 nm with 29% yield, and with 53% yield if we consider gaps under 10 nm. To validate the system, experiments using the fabricated nanogaps with bonded oligothiophene molecules were run, verifying the theory of molecular conduction.