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Long Term Drift Observed in ISFET Due to the Penetration of H+ Ions into the Oxide Layer

  • Chinmayee Hazarika
  • Sujan Neroula
  • Santanu SharmaEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11942)

Abstract

Ion Sensitive Field Effect Transistor (ISFET) and related biosensors when undergo prolonged hours of operation, witnesses a temporal change in threshold voltage which is termed as drift. Drift is a secondary effect which leads to instability of the device resulting into inaccuracy in both in vivo and in vitro measurements. Various types of drift have been of great interest for researchers and long term drift is one of its kinds. Long term drift is observed in different sensing layer in ISFET devices of which silicon dioxide (SiO2) gate ISFET witnesses the maximum. This paper presents the modeling and analysis of long term drift observed in ISFET due to diffusion of H+ ions into the oxide layer and the field caused by this penetration. The additional hydrogen ions left after the protonation of dangling bonds penetrate through the sensing layer which results into an electric field that influences the threshold voltage. A physical model has been designed explaining the effect of this penetration of positive ions into sensing layer and simulations of this model has been carried out. This model has been further experimentally validated using a Schottky based ISFET device with SiO2 as the sensing layer. Both the theoretical and experimental data indicates toward the existence of this drift and its prominence can be observed in lower pH values.

Keywords

Biosensors Diffusion Ion Sensitive Field Effect Transistor Long term drift Threshold voltage 

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Chinmayee Hazarika
    • 1
  • Sujan Neroula
    • 2
  • Santanu Sharma
    • 2
    Email author
  1. 1.Department of E.C.EG.I.M.TGuwahatiIndia
  2. 2.Department of E.C.ETezpur UniversityTezpurIndia

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