Batch-Fabricated α-Si Assisted Nanogap Tunneling Junctions

• Published in: Nanomaterials (Basel, Switzerland) Vol. 9; no. 5; p. 727
• Main Authors: Banerjee, Aishwaryadev, Khan, Shakir-Ul Haque, Broadbent, Samuel, Likhite, Rugved, Looper, Ryan, Kim, Hanseup, Mastrangelo, Carlos H.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 10.05.2019; MDPI AG
• Subjects: batch fabrication; bio-sensing; gold adhesion; IOT; molecular junctions; nanogap electrodes; protein detection; quantum tunneling; α-Si; bio-sensing; gold adhesion; nanogap electrodes; quantum tunneling; molecular junctions; batch fabrication; protein detection; α-Si; IOT
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano9050727

This paper details the design, fabrication, and characterization of highly uniform batch-fabricated sidewall etched vertical nanogap tunneling junctions for bio-sensing applications. The device consists of two vertically stacked gold electrodes separated by a partially etched sacrificial spacer layer of sputtered α-Si and Atomic Layer Deposited (ALD) SiO2. A ~10 nm wide air-gap is formed along the sidewall by a controlled dry etch of the spacer. The thickness of the spacer layer can be tuned by adjusting the number of ALD cycles. The rigorous statistical characterization of the ultra-thin spacer films has also been performed. We fabricated nanogap electrodes under two design layouts with different overlap areas and spacer gaps, from ~4.0 nm to ~9.0 nm. Optical measurements reported an average non-uniformity of 0.46 nm (~8%) and 0.56 nm (~30%) in SiO2 and α-Si film thickness respectively. Direct tunneling and Fowler–Nordheim tunneling measurements were done and the barrier potential of the spacer stack was determined to be ~3.5 eV. I–V measurements showed a maximum resistance of 46 × 103 GΩ and the average dielectric breakdown field of the spacer stack was experimentally determined to be ~11 MV/cm.