title: High-k dielectric Al₂O₃ nanowire and nanoplate field effect sensors for improved pH sensing.
abstract: Over the last decade, field-effect transistors (FETs) with nanoscale dimensions have emerged as possible label-free biological and chemical sensors capable of highly sensitive detection of various entities and processes. While significant progress has been made towards improving their sensitivity, much is yet to be explored in the study of various critical parameters, such as the choice of a sensing dielectric, the choice of applied front and back gate biases, the design of the device dimensions, and many others. In this work, we present a process to fabricate nanowire and nanoplate FETs with Al(2)O(3) gate dielectrics and we compare these devices with FETs with SiO(2) gate dielectrics. The use of a high-k dielectric such as Al(2)O(3) allows for the physical thickness of the gate dielectric to be thicker without losing sensitivity to charge, which then reduces leakage currents and results in devices that are highly robust in fluid. This optimized process results in devices stable for up to 8 h in fluidic environments. Using pH sensing as a benchmark, we show the importance of optimizing the device bias, particularly the back gate bias which modulates the effective channel thickness. We also demonstrate that devices with Al(2)O(3) gate dielectrics exhibit superior sensitivity to pH when compared to devices with SiO(2) gate dielectrics. Finally, we show that when the effective electrical silicon channel thickness is on the order of the Debye length, device response to pH is virtually independent of device width. These silicon FET sensors could become integral components of future silicon based Lab on Chip systems.
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Bobby
authors.initials: B
authors.lastname: Reddy
authors.forename: Brian R
authors.initials: BR
authors.lastname: Dorvel
authors.forename: Jonghyun
authors.initials: J
authors.lastname: Go
authors.forename: Pradeep R
authors.initials: PR
authors.lastname: Nair
authors.forename: Oguz H
authors.initials: OH
authors.lastname: Elibol
authors.forename: Grace M
authors.initials: GM
authors.lastname: Credo
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Daniels
authors.forename: Edmond K C
authors.initials: EK
authors.lastname: Chow
authors.forename: Xing
authors.initials: X
authors.lastname: Su
authors.forename: Madoo
authors.initials: M
authors.lastname: Varma
authors.forename: Muhammad A
authors.initials: MA
authors.lastname: Alam
authors.forename: Rashid
authors.initials: R
authors.lastname: Bashir
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D017097:Electric Impedance; D006863:Hydrogen-Ion Concentration; D053770:Nanowires / Q000737:chemistry*; D015203:Reproducibility of Results; D012825:Silicon / Q000737:chemistry; D014173:Transistors, Electronic
chemical_list: D000537:Aluminum Oxide; D012825:Silicon