Scanning tunneling spectroscopy results are presented on oriented monolayer films of conjugated phenylbased molecules self-assembled on gold. Three related molecules of different lengths are investigated. The molecules do not show resonances in electron transmission at least up to 1.5 V. We model the experiments successfully by the molecules acting as a potential barrier to electron transmission. The potential barrier is trapezoidal when the molecule has a permanent dipole moment ͑normal to the gold surface͒, in agreement with the asymmetric I(V) curves. For 2 V bias and larger, the film is modified by the measurement, which prevents measurements of possible resonances at higher energies.

Ultralow-power gas sensing devices need to operate without an energy consuming heater element. This requires the design of sensing devices that are so efficient that they can operate at room temperature (RT). Here, we report on the RT sensing performance of atomic layer deposition (ALD) prepared i-ZnO and Al-doped ZnO sensing devices. The sensitivity of these devices has been catalytically enhanced with ALD Pt nanoparticles (NPs). It was shown that the size distribution of the Pt NPs can be controlled by the number of Pt-ALD cycles. The Pt-enhanced sensing devices showed a reversible, proportional change in current response at RT upon exposure to O2 and CO. O2 could be detected, diluted in N2, down to 0.5%. CO could be detected, diluted in N2 in the presence of O2 and H2O, down to 20 ppm. Reference devices without Pt NPs showed no response, indicating the importance of the Pt NPs for the sensing mechanism.

A metal-insulator-semiconductor (MIS) capacitor with La2O3 dielectric is proposedin this work as a sensor for measuring CO2 in air. In this device, a 10 nm thick La2O3 dielectriclayer, which serves as a CO2 sensitive material, was atomic-layer-deposited (ALD) on p-typesilicon. Change in the at band voltage (VFB) of the MIS capacitor due to the reactionbetween CO2 and oxide layer and its interfaces, is used as the gas sensitive parameter of thesensor. The deposition temperature for the La2O3 layer has been optimized for maximizingCO2 sensitivity. The process ow including post annealing (rapid thermal annealing) has beenoptimized to allow further possibility to integrate the sensor with CMOS read-out circuitries. The sensor shows a sensitivity of 84 mV per decade to CO2 in air in a concentration rangefrom 300-5000 ppm at ambient temperature with a response time (t90) of 34 minutes.

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