A STUDY ON TUNNELING-SPECTROSCOPIC DEVICES WITH NANO-GAP STRUCTURE USING ULTRATHIN SILICON DIOXIDE FILM AS A SPACER

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Sensing devices with a silicon/nano-gap/silicon structure using a silicon dioxide film as a spacer have been fabricated, and ultrapure water introduced into the nano-gap of the sensing device has been found to be detected by the change of capacitance and conductance for the sensing device. The frequency dependence of capacitance and conductance changes by introducing ultrapure water into the nano-gap has been demonstrated. Scanning electron microscope observation of the cross section of the device structure has shown that a nano-gap structure with a silicon dioxide film as a spacer was fabricated. Fourier transform infrared absorption measurements for the device structure have shown that ultrapure water penetrates into the nano-gap. Near-infrared ray transmission measurements for the device structure have shown that ultrapure water penetrates through the nano-gap and that the nano-gap structure was fabricated as designed, because silicon is transparent to near-infrared ray. It has confirmed that ultrapure water penetrates into the nano-gap because sensing surface is hydrophobic. The effect of silicon dioxide of sensing surface on sensing ultrapure water in the nano-gap has been examined and the condition of high sensitively has been found. We have proposed a sensing model of electron response through states of water.