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Schematic illustration of one reaction cycle of the ALD process, using the trimethylaluminium (TMA) -water process to make thin aluminium oxide films as (simplified) example. There, the starting surface contains hydroxyls (OH groups) as reactive sites; Step 1 is the reaction of TMA; Step 2 is a purge or evacuation step, Step 3 is the reaction ...
Also known as hafnium dioxide or hafnia, this colourless solid is one of the most common and stable compounds of hafnium. It is an electrical insulator with a band gap of 5.3~5.7 eV. [2] Hafnium dioxide is an intermediate in some processes that give hafnium metal. Hafnium(IV) oxide is quite inert.
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite , aluminium 's chief ore, through the Bayer process ) in molten cryolite and electrolyzing the molten salt bath, typically in a purpose-built cell.
The white hafnium(IV) oxide (HfO 2), also known as hafnium dioxide or hafnia, with a melting point of 2,812 °C and a boiling point of roughly 5,100 °C, is very similar to zirconia, but slightly more basic. [13] It is an electrical insulator with a band gap of 5.3~5.7 eV. [15] Hafnium(IV) oxide typically adopts the same structure as zirconia ...
Atomic layer epitaxy (ALE), [1] more generally known as atomic layer deposition (ALD), [2] is a specialized form of thin film growth that typically deposit alternating monolayers of two elements onto a substrate. The crystal lattice structure achieved is thin, uniform, and aligned with the structure of the substrate.
Atomic layer deposition (ALD) depends on very small amounts of water vapor for High-K film formation. The technique requires the proper molecule be available and not replaced by competitive species that will disrupt the lattice structure. Temperature control of both the gas and water, as well as level control, affect delivery rate.
Oxide may also be grown with impurities (alloying or "doping"). This may have two purposes. During further process steps that occur at high temperature, the impurities may diffuse from the oxide into adjacent layers (most notably silicon) and dope them. Oxides containing 5–15% impurities by mass are often used for this purpose.
Molecular-beam epitaxy takes place in high vacuum or ultra-high vacuum (10 −8 –10 −12 Torr).The most important aspect of an MBE process is the deposition rate (typically less than 3,000 nm per hour) that allows the films to grow epitaxially (in layers on top of the existing crystal).