When a pentacene thin-film transistor is exposed to humidity, its saturation current decreases. This decrease was found to be reversible and can therefore be used to measure the amount of relative humidity in atmosphere. The sensitivity was found to depend on the thickness of the pentacene layer. The microscopic origin of the sensing mechanism is discussed.

Using radioactive tracer Fe‐59 and measuring rest activities after sectioning, the tracer diffusivities of Fe in almost single crystalline magnetite Fe3‐ΔO4 have been measured as a function of temperature and oxygen partial pressure. The measured curves log DFe*/log pO2 all exhibit a minimum in the temperature range between 900°C and 1400°C in the homogeneity range of the magnetite. At sufficiently high oxygen partial pressures the slope ϱ log D Fe*/log pO2 is 2/3: at sufficiently low partial pressures it is —2/3. This allows to conclude that stoichiometric Fe3O4 has a Frenkel disorder in the cationic sublattice, while at high oxygen potentials iron ion vacancies are responsible for the cation deficit. Their electrical charge is balanced by threevalent iron ions.

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