Deferoxamine-B-Functionalized Silicon Nanowire Field-Effect Transistor Interfaces for Ultralow-Concentration Fe3+...

Maintaining ultralow metal-ion purity in process chemicals is crucial in semiconductor fabrication, where trace Fe3+ contamination can lead to dielectric breakdown, yield loss, and unintended doping. Inductively coupled plasma mass spectrometry (ICP-MS) provides excellent qualitative and quantitative sensitivity; however, it requires specialized infrastructure, is time-consuming and costly, and is not well suited for rapid on-site screening. Herein, we present a deferoxamine-B (DFO-B)-functionalized silicon nanowire field-effect transistor (SiNW-FET) engineered for the ultrasensitive, label-free detection of Fe3+ in semiconductor-grade chemicals. Mixed PEG self-assembled monolayers were modified with DFO-B via aldehyde-amine coupling to form a stable, high-affinity chelation interface. In aqueous Fe3+ standards, the DFO-B-functionalized SiNW-FET exhibited a linear response from 10-15 to 10-11 M, with a practical LOD of 10-15 M and an above-Nernst sensitivity of -24 mV dec-1. In chemically complex matrices, the practical analytical boundary shifted upward, with reliable Fe3+ responses observed at approximately 10-12 M in a 23-element mixed-ion matrix and ∼10-13 M in a highly diluted IPA-derived multi-element matrix. Mechanistic analysis rationalizes the above-Nernst response using an equivalent-circuit framework involving chelation-associated chemical capacitance, coordination-induced interfacial polarization, and protonation-state effects. The sensor showed preferential Fe3+ response under tested interferent conditions and remained operational in mixed-ion and highly diluted IPA-containing matrices, while also revealing matrix-dependent shifts in analytical performance. This work introduces a rapid on-site Fe3+ screening approach based on a portable and potentially in situ-compatible SiNW-FET platform that can complement ICP-MS for contamination assessment, while establishing a modular sensing interface that can be extended to other transition metals through ligand substitution. With integration into microfluidic sample handling and CMOS-compatible readout, this technology offers a portable, point-of-use Fe3+ screening through a discrete incubation-rinse-electrical readout workflow.