Al₂O₃/silicon nanoISFET with near ideal nernstian response

Nanoscale ISFET (ion sensitive field-effect transistor) pH sensors are presented that produce the well-known sub-Nernstian pH-response for silicon dioxide (SiO₂) surfaces and near ideal Nernstian sensitivity for alumina (Al₂O₃) surfaces. Titration experiments of SiO₂ surfaces resulted in a varying pH sensitivity ∼20 mV/pH for pH near 2 and >45 mV/pH for pH > 5. Measured pH responses from titrations of thin (15 nm) atomic layer deposited (ALD) alumina (Al₂O ₃) surfaces on the nanoISFETs resulted in near ideal Nernstian pH sensitivity of 57.8 ± 1.2 mV/pH (pH range: 2 - 10; T = 22 °C) and temperature sensitivity of 0.19 mV/pH °C (22 °C ≤ T ≤ 40 °C). A comprehensive analytical model of the nanoISFET sensor, which is based on the combined Gouy - Chapman - Stern and Site-Binding (GCS-SB) model, accompanies the experimental results and an extracted ΔpK ≈ 1.5 from the measured responses further supports the near ideal Nernstian pH sensitivity.