Transition metal oxide bilayers

A method of forming a plurality of layers comprising

• forming a first layer on a substrate using sputtering, wherein the first layer comprises a first compound comprising Me1wMe2xSiy, wherein Me1 and Me2 are metals, w≧0, x>0, y≧0, and at least one of w, x, and y is greater than zero;
• forming a second layer above or below the first layer using reactive sputtering in an atmosphere comprising argon and oxygen, wherein the second layer comprises a second compound comprising Me1aMe2bSicOd, where a≧0, b≧0, c≧0, and d>0, and at least one of a, b, and c is greater than zero;
• and
• annealing the first and second layers such that oxygen atoms migrate from the second layer into the first layer;
• wherein the annealed first layer has linear resistance and substoichiometric composition, and the annealed second layer has bistable resistance and near-stoichiometric composition,
• wherein the sum of the first layer thickness and the second layer thickness is between about 20 Å and about 100 Å, and
• wherein the second layer has a thickness between 25% and 75% of the total thickness.

A nonvolatile memory element comprising

• a first electrode layer,
• a second electrode layer, and
• a first oxide layer and second oxide layer disposed between the first and second electrode layers;
• wherein the first oxide layer comprises a first compound comprising Me1wMe2xSiyOz, wherein Me1 and Me2 are metals, w≧0, x≧0, y≧0, and z>0, and at least one of w, x, and y is greater than zero;
• wherein the second oxide layer comprises a second compound comprising Me1aMe2bSicOd, wherein a≧0, b≧0, c≧0, and d>0, and at least one of a, b, and c is greater than zero,
• wherein one of the oxide layers has linear resistance and substoichiometric composition, and the other oxide layer has bistable resistance and near-stoichiometric composition;
• wherein the sum of the two oxide layer thicknesses is between about 20 Å and about 100 Å;
• wherein the oxide layer with bistable resistance has a thickness between about 25% and about 75% of the total thickness;
• and
• wherein one of the metals is selected from the group consisting of tantalum, niobium, hafnium, yttrium, zirconium, lanthanum, vanadium, titanium, tungsten, nickel, aluminum, and combinations thereof.