  Semiconductive ZnO has shown to be a fascinating element for application in
high-performance sensors. ZnO with various thicknesses (87-500 nm) was
deposited on the surface of Co-based amorphous micro-wire
(Co68.15Fe4.35Si12.5B15) using magnetron sputtering technique and the
magnetoimpedance (MI) response was evaluated. The MI% increases monotonously up
to the 240 nm thickness of the ZnO layer. By further increase in the ZnO layer
thickness the MI% decreases. MI response and field sensitivity increased from
227% and 1.7 %/Oe for bare micro-wire up to 406% and 4.99 %/Oe for ZnO
deposited micro-wire with a thickness of 240 nm. The x-ray diffraction (XRD)
and scanning electron microscopy (SEM) were used to characterize the structural
grown ZnO layers. Vibrating sample magnetometry (VSM) was used to reveal the
role of the ZnO thin layer in the MI response. The same trend of increase and
decrease in the MI% by thickness was observed for the transverse permeability
of the samples determined by VSM. The obtained results address a simple way to
achieve high MI response and sensitivity with selective surface sensing.
