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A new low-voltage contrast mechanism due to electron-hole pairs generated in the oxide by an electron beam was observed at electric fields lower than 3.5 MV/cm. This is in addition to the tunneling current microscopy (TCM) contrast mechanism observed at electric fields higher than 3.5 MV/cm. The new contrast mechanism is opposite in sign to the TCM contrast mechanism such that the image of a local thinning defect in the oxide is dark at low bias voltage and bright at higher bias voltage. Good contrast can be obtained at electric field as low as 2.4 MV/cm. Applications include large area imaging of oxide defects and quantitative mapping of small oxide thickness variations.

A new low-voltage contrast mechanism due to electron hole pairs generated in the oxide by an electron beam was observed at an electric field lower than 3.5 MV/cm in addition to the tunneling current microscopy (TCM) contrast mechanism at electric fields higher than 3.5 MV/cm. The new contrast mechanism is opposite in sign to the TCM contrast mechanism. Good contrast can be obtained at an electric field as low as 2.4 MV/cm, which is two to three times smaller than that needed for TCM contrast. Potential applications include large area imaging and quantitative imaging of oxide defects.

Thin film gas sensors based on tin oxide are fabricated and its characteristics are examined. Target gases are dimethyl methylphosphonate(C3HgO3P, DMMP) as a simulant gas for nerve gas GA (Tabun) and acetonitrile (CH,CN) as a simulant gas for blood gas. Sensing materiais are Pt/Sn02, where Pt layer (30 A) is deposited on tin oxide film grown on alumina substrate, ( Sn,In)02/Pt and SnO,/Pt, where (Sn,In)02 and tin oxide films are deposited on Pt layer (30 A) grown on aluminasubstrate, respectively. In the latter two sample have a nano-wire structurc growl1 over thin film. The thickness of nano-wire is -60 nm. Nano-wire sensors grown on thin film show high sensitivity and stability to DMMP and CH3CN. We display the results compared that of nano-wire with ordinary tin oxide sample.

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