hafniumoxide

Hafnium oxide, also known as hafnia, is an inorganic compound with the formula HfO2. It is the oxide of hafnium and typically appears as a white to off-white solid with very high thermal stability. Hafnia has a very high melting point (roughly 2750–2800°C) and a density near 9.68 g/cm³. It features a wide optical band gap of about 5.6 eV and a high dielectric constant in the range of 20–25, properties that are central to many of its applications.

Crystal structure and phase behavior are notable for hafnium oxide. At room temperature it adopts a monoclinic structure, while higher temperatures or certain dopants can promote tetragonal or cubic phases. For electronic device use, stabilizing the high-temperature phases at ambient conditions is common, often by doping with yttrium oxide or other dopants.

Production and processing typically involve treating soluble hafnium salts to form hafnium hydroxide, which is then calcined to HfO2. In industry, thin films of hafnium oxide are deposited by chemical vapor deposition or atomic layer deposition, followed by annealing to achieve the desired phase and electrical properties for device integration.

Applications are dominated by its role as a high-k gate dielectric in advanced semiconductor devices, where it replaces silicon dioxide to enable continued device scaling in CMOS transistors. It is also used as a diffusion barrier and protective coating in microelectronics and as a coating material in certain optical and protective applications due to its high refractive index and wide band gap. Hafnium oxide is chemically stable and, in powder form, of low acute toxicity, with standard safety precautions for handling oxide powders advised.