H 1201 (OTTO) Hafnium oxide, 99.9% Cas 12055-23-1 - used in optical coatings, and as a high-κ dielectric in DRAM capacitors and in advanced metal-oxide-semiconductor devices. H 1201 (OTTO) Hafnium oxide, 99.9% Cas 12055-23-1 - used as a gate insulator in field-effect transistors due to its high dielectric constant. It plays an important role as a possible candidate for resistive-switching memories, as a refractory material in the insulation of devices such as thermocouples and as a high-κ dielectric in DRAM capacitors.