Co-adsorption processes, kinetics and quantum mechanical modelling of nanofilm semiconductor gas sensors
A quantum mechanical model of co-adsorption on semiconductor surfaces is developed and successfully adopted towards exposure to several gases. It is related to nanofilms and thus allows the application of electric fields altering the electronic surface properties of adsorption centres (electro-adsorptive effect, EAE). The model is matched against experimental data with O 2 , NO 2 and CO measurements under the hypothesis of no direct interaction among the species. However the sequence of adsorption plays an important role where the adsorption of one gas species is opening up other sites that are filled by another sort of impinging molecules. Quantum mechanical modelling of co-adsorption: (a)…
Nanofilm metal layers as vacuum quality sensors
Abstract A monitoring device for vacuum quality is realized by lowest cost single use oxygen sensors for vacuum insulation panels. They use the pressure dependence of oxide layer growth thickness on electrically measured metal nanofilms. These films were manufactured by e-beam evaporation, characterized in terms of resistance change with subsequent modeling of underlying mechanisms.
Ultrathin metal oxidation for vacuum monitoring device applications
The oxide growth on thin metal films at room temperature has been investigated in terms of resistance change during oxidation. These data have been interpreted using the extended Cabrera–Mott theory of oxidation by Boggio. The resulting oxide thickness as well as the oxidation kinetics was found to depend on pressure. According to this dependence, oxidation of ultrathin metal films can be applied for monitoring the vacuum quality inside an evacuated environment. The performance of aluminum and copper sensing layers are compared with respect to sensor lifetime and response. Furthermore, the theoretically evaluated and resistively measured oxide thicknesses are verified by TEM studies.
UV LED Photo Electron Ionisation for MS and IMS
AbstractA new MEMS ionisation source for spectrometry is presented on the basis of photo electron emission in silicon MEMS. Lanthanum hexaboride ceramic sample and thin nanolayer proved their suitability for photo electron emission in the desired photon energy range of 3.1eV to 3.9eV which correspond to industrially available UV LED. This ionisation source alternative to a Photoionisationdetector (PID) is inspected of its gas ionisation behaviour using gases with an ionisation potential over and under an energy of 10,6eV. To enable the ionisation of the gases the emitted electrons were accelerated to a well-defined energy. The results of these investigations are comparable to the UV dischar…
Nano photoelectron ioniser chip using LaB6 for ambient pressure trace gas detection
A detector including a nanoscaled ioniser chip that surmounts the limitation of conventional photo ionisation detectors is presented. Here, ionisable gaseous substances can be detected by photoelectrons accelerated to the ionisation potential of the incoming gaseous molecules. Thin lanthanum hexaboride (LaB"6) films deposited by pulsed laser technique (PLD) serve as the air stable photocathode material representing the basis of the ioniser chip of the detector. Besides the analysis of the emission behaviour of the photocathode in vacuum and at atmospheric pressure, the detection of different volatile alcohols using the detector with a low-energy UV LED instead of a PID (VUV photon source) w…