Formation of Metal Oxide Particles in Atomic Layer Deposition During the Chemisorption of Metal Chlorides: A Review

Abstract

As has been known for a decade, metal oxide particles can form in a single reaction of gaseous metal chlorides with solid oxides. This is an undesirable effect in the fabrication of thin films by atomic layer deposition (ALD). This work reviews the experimental results related to the metal oxide particle formation and the mechanisms suggested to account for it. The suggested mechanisms cannot explain the observations, but systematic analysis of the possible reaction paths delivers one reaction mechanism candidate, based on a reaction between surface chlorine groups and the hydroxyl groups of gaseous metal hydroxychloride intermediates. The consequences of the proposed mechanism are discussed.

Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

“…ZrO 2 and TiO 2 , has been reported when using chloride reactants with oxide substrates [29][30][31]. Increasing the growth temperature has been observed to enhance the particle formation [29][30][31][32]. While undesired for typical ALD applications, e.g.…”

“…The absence of iron oxide on the electrodes was confirmed with XPS by monitoring the Fe 2p intensity while moving the X-ray spot (150 μm) from the substrate onto the electrode. In ALD with a chloride precursor and oxide substrate, the chloride precursor is considered to react primarily with surface -OH groups [31]. Thus, the observed selective growth could be attributed to the obvious difference in the density of -OH groups between the SiO 2 substrate and the platinum electrode.…”

ZnO Nanostructures for Dye‐Sensitized Solar Cells

“…However, the recently developed ALD technique distinguishes itself by offering atomic-level thickness as well as large-area uniformity. [207] ALD is actually a self-limiting process of vapor-solid deposition, in which film formation takes place in a cyclic manner through a series of saturated surface reactions between the adsorbed precursor and the species left on the surface, and, moreover, multilayer adsorption is, by definition, excluded. In this method, the film thickness can be precisely controlled by adjusting the number of deposition cycles and growth rate.…”

Aluminum oxide/titanium dioxide nanolaminates grown by atomic layer deposition: Growth and mechanical properties

“…61 A dedicated review has been written about the reaction mechanisms and "agglomeration phenomenon" in this process, taking place beyond 300 °C. 66 Taking into account the widespread use of these two processes, there is surprisingly little information available on combining these two processes as ATO. ATO has been used industrially since the 1980s in electroluminescent displays 67 ; however for that, chloride reactant is used also for the Al2O3 component.…”