The layer charge is typically balanced by divalent calcium ( Ca 2 + ) or magnesium ( Mg 2 + ).
Thus, nontronite typically is characterised by having most ( usually greater than 60 % ) of the layer charge located in the tetrahedral sheet.
The double-layer charge forms a field in the molecular IHP layer of the solvent molecules that corresponds to the strength of the applied voltage.
The double-layer charge forms a static electric field in the molecular layer of the solvent molecules in the IHP that corresponds to the strength of the applied voltage.
Recognizing the importance of their discovery Bradley and Burroughes decided that it should be patented and together with Richard Friend filed a GB patent ( PCT / GB90.00584 ) with first claim : " An electroluminescent device comprising a semiconductor layer in the form of a thin dense polymer film comprising at least one conjugated polymer; " " a first contact layer which is selected so that on application of an electric field to said device charge carriers of a first type are injected into the semiconductor layer; " " and a second contact layer which is selected so that on application of an electric field to said device charge carriers of a second type are injected into the semiconductor layers, wherein the polymer film of the semiconductor layer has sufficiently low concentration of extrinsic charge carriers that on applying an electric field between the first and second contact layers across the semiconductor layer as to render the second contact layer positive relative to the first contact layer charge carriers of said first and second types are injected into the semiconductor layer and combine to form in the conjugated polymer charge carrier pairs which decay radiatively so that radiation is emitted from the conjugated polymer ."