A partially-insulated cathode for exciting plasma in a plasma chamber is provided. The partially-insulated cathode includes a conductive structure enclosing a cavity having a cavity surface and an insulating material contiguously covering a portion of the cavity surface from the cavity opening up to an insulation height that is less than a cavity height. Cross-sections of the cavity in X-Y planes have at least one respective cavity-width. A cavity opening has a diameter less than a minimum cavity-width of the at least one cavity-width.

A partially-insulated cathode for exciting plasma in a plasma chamber is provided. The partially-insulated cathode includes a conductive structure enclosing a cavity having a cavity surface and an insulating material contiguously covering a portion of the cavity surface from the cavity opening up to an insulation height that is less than a cavity height. Cross-sections of the cavity in X-Y planes have at least one respective cavity-width. A cavity opening has a diameter less than a minimum cavity-width of the at least one cavity-width.

The invention relates to a nanoplasma switch device, comprising: multiple electrically isolated electrodes; a gap separating the two electrodes; wherein the gap has a width which is dimensioned to effect the generation of a plasma by electric-field electron emission.

The invention relates to a nanoplasma switch device, comprising: multiple electrically isolated electrodes; a gap separating the two electrodes; wherein the gap has a width which is dimensioned to effect the generation of a plasma by electric-field electron emission.

A gas reactor device includes a plurality of microcavities or microchannels defined at least partially within a thick metal oxide layer consisting essentially of defect free oxide. Electrodes are arranged with respect to the microcavities or microchannels to stimulate plasma generation therein upon application of suitable voltage. One or more or all of the electrodes are encapsulated within the thick metal oxide layer. A gas inlet is configured to receive feedstock gas into the plurality of microcavities or microchannels. An outlet is configured to outlet reactor product from the plurality of microcavities or microchannels. In an example preferred device, the feedstock gas is air or O.sub.2 and is converted by the plasma into ozone (O.sub.3). In another preferred device, the feedstock gas is an unwanted gas to be decomposed into a desired form. Gas reactor devices of the invention can, for example, decompose gases such as CO.sub.2, CH.sub.4, or NO.sub.x.