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Gas Sensing of NiO‐SCCNT Core–Shell Heterostructures: Optimization by Radial Modulation of the Hole‐Accumulation Layer
Author(s) -
Raza Muhammad Hamid,
Movlaee Kaveh,
Leonardi Salvatore Gianluca,
Barsan Nicolae,
Neri Giovanni,
Pinicola
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201906874
Subject(s) - non blocking i/o , materials science , heterojunction , layer (electronics) , shell (structure) , coaxial , chemisorption , nanotechnology , dielectric , chemical engineering , composite material , optoelectronics , chemistry , organic chemistry , engineering , adsorption , electrical engineering , catalysis
Hierarchical core–shell (C–S) heterostructures composed of a NiO shell deposited onto stacked‐cup carbon nanotubes (SCCNTs) are synthesized by atomic layer deposition (ALD). A film of NiO particles (0.80–21.8 nm in thickness) is uniformly deposited onto the inner and outer walls of the SCCNTs. The electrical resistance of the samples is found to increase of many orders of magnitude with the increasing of the NiO thickness. The response of NiO–SCCNT sensors toward low concentrations of acetone and ethanol at 200 °C is studied. The sensing mechanism is based on the modulation of the hole‐accumulation region in the NiO shell layer upon chemisorption of the reducing gas molecules. The electrical conduction mechanism is further studied by the incorporation of an Al 2 O 3 dielectric layer at NiO and SCCNT interfaces. The investigations on NiO–Al 2 O 3 –SCCNT, Al 2 O 3 –SCCNT, and NiO–SCCNT coaxial heterostructures reveal that the sensing mechanism is strictly related to the NiO shell layer. The remarkable performance of the NiO–SCCNT sensors toward acetone and ethanol benefits from the conformal coating by ALD, large surface area of the SCCNTs, and the optimized p‐NiO shell layer thickness followed by the radial modulation of the space‐charge region.