Johann Göbel

Solid-State Gas Sensors: Sensor System Challenges in the Civil Security Domain

The detection of military high explosives and illicit drugs presents problems of paramount importance in the fields of counter terrorism and criminal investigation. Effectively dealing with such threats requires hand-portable, mobile and affordable instruments. The paper shows that solid-state gas sensors can contribute to the development of such instruments provided the sensors are incorporated into integrated sensor systems, which acquire the target substances in the form of particle residue from suspect objects and which process the collected residue through a sequence of particle sampling, solid-vapor conversion, vapor detection and signal treatment steps. Considering sensor systems with metal oxide gas sensors at the backend, it is demonstrated that significant gains in sensitivity, selectivity and speed of response can be attained when the threat substances are sampled in particle as opposed to vapor form.

Spurengasdetektion mittels Laserionenmobilitätsspektrometrie

Zusammenfassung Die Ionenmobilitätsspektrometrie eignet sich zum schnellen Nachweis von Gasen unter Atmosphärendruck. Verwendet man zur Ionisation der Gasmoleküle eine radioaktive Quelle (63Ni), können sich die Signale mehrerer Substanzen überlagern, was zu schwer interpretierbaren Spektren führt. Um die Vorteile der Laserionisation zu demonstrieren, untersuchten wir die Detektion von Kohlenwasserstoffen und Aminen im Spurengasbereich mit Hilfe der Zwei-Photon-Ionisation. Abstract Ion mobility spectrometry is a convenient method for the fast detection of gases under atmospheric pressure conditions. Using 63Ni as ionization source, signals of different substances can interfere, which leads to hardly interpretable spectra. Two-photon laser ionization can overcome such problems. The advantages of this method are demonstrated by the detection of various kinds of hydrocarbons and amines in the trace gas concentration range.

Materials and Materials Issues Relating to High-Performance Gas Sensing Technologies

High-performance gas sensing technologies like photo-acoustic gas detection and ion mobility spectrometry rely on microcomponents, which require extended operation at high temperatures. In this context silicon-on-insulator wafers as well as wide-bandgap materials such as silicon carbide and metal oxide semiconductors are of interest. We show that such materials can be combined to perform a variety of mechanical, thermal, electrical and gassensing functionalities. Materials and technology development issues relating to such materials are outlined.