Every day in our life is larded with a huge number of chemical reactions on surfaces. Some
reactions occur immediately for others an activation energy has to be supplied. Thus it
happens that though a reaction should thermodynamically run off it is kinetically hindered.
Meaning the partners react only to the thermodynamically more stable product state within a
mentionable time if the activation energy of the reaction is supplied. With the help of
catalysts the activation energy of a reaction can be lowered. Such catalytic processes on
surfaces are widely used in industry. Around 90% of chemicals are produced via a
heterogeneously catalyzed process where a reaction occurs on the surface of a catalyst. However
why is it generally possible that such reactions run off with the help of heterogeneous
catalysis meaning with lower activation energy than without presence of a catalyst? What
happens with the energy which is released during a reaction of gas particles on surfaces? How
is this energy released when some part of the energy is transferred to the reactant and some
to the chemically active surface? Which physical mechanisms play a key role in the energy
transfer? These questions are summarized in the concept of the energy dissipation. To observe
this energy dissipation phenomenon we use a new method the chemoelectronics. With this method
we try to detect the released energy induced by reactions on surfaces via thin-layered
electronic device elements. An aim of this work is to build up very sensitive chemoelectronic
sensors to measure electronic excitations released during such simple reactions of molecules as
adsorption and desorption and more complicated reactions as the water formation reaction.
Therefore a new line of chemoelectronic sensors is developed and characterized in terms of
internal photoemission and stability. Meaning the previously used aluminum (Al AlOx Ag) and
tantalum based (Ta TaOx Au) metal insulator metal sensors (MIM) are tested and new titanium
based (Ti TiOx Au) MIMs are developed. Additionally silicon based stepped metal insulator
semiconductor sensors (stepped-MIS Si SiOx Au Si SiOx Pt) are set up and characterized. For
the characterization of the chemoelectronic sensors the process of internal photoemission is
used. Both chemical- and photoexcitation release hot charge carriers (electrons and holes).
Due to the existence of excited carriers in the sensor a current can be measured without
applying a bias voltage. It will be shown that the chemo- and the photosensitivity are strongly
related to each other. As a first experiment for the chemical selectivity of the detectors a
stream of excited hydrogen molecules and hydrogen atoms is used. The excitation and radical
formation is produced by the interaction of ground state molecules with a hot tungsten surface
according to the pioneering experiments of Irving Langmuir. Additionally excited oxygen beams
are studied in this work.
