The sandwich grid diode is a new means of producing extremly high elektrical fields at a solid surface. The ability to ionize gases and to produce field electrons with such a thin film system permits an estimate of the maximal field strength. It is interesting to note, that with this diode one can produce fields higher than 5-107 V/cm in gases up to atmospheric pressure without the risk of a discharge. This fact may become of some importance for the study of field induced desorption and catalysis
