Atomic Layer Deposition of Y[sub 2]O[sub 3]∕ZrO[sub 2] Nanolaminates

Abstract

Subsequently, in order to promote thorough interdiffusion of homogeneous yttria-zirconia alloys, short-period (bilayer period < 1 nm) yttria/zirconia laminates were and annealed under the same conditions as the long-period laminates.  2-4 mol% YSZ films with thicknesses 20-35 nm  As-deposited YSZ is amorphous; annealed is polycrystalline  Annealed YSZ with 3 mol% yttria (3YSZ) is tetragonal, as expected from bulk phase diagram 6  Annealed short-period laminate exhibits columnar grain structure (~5-25 nm grain diameter) that spans entire film thickness  XRR indicates density increase from 5.78±0.29 g/cc to 6.13±0.31 g/cc (commercial bulk 3YSZ, 6.05 g/cc), likely due to removal of excess H 2 O incorporated during ALD process and film crystallization  Densification was accompanied by 2.8 (±1.7) % reduction in film thickness Detailed electrical conductivity measurements were carried out on selected as-deposited and heat treated samples using the van der Pauw technique. Electrical characterization of ultrathin (25-35 nm thick) 3YSZ films indicated a 10 times enhancement of the total electrical conductivity compared to bulk 3YSZ 6 and is about 15 times higher than that of bulk polycrystals with 2% yttria 7. It is interesting to note that the films show very high total conductivity even with very low yttria content. Further investigation of yttria-doping effects and phase transformation kinetics are needed to understand the observed increase in electrical conductivity of these yttria-zirconia alloys. 6. Fevre, M., et al, Local order and thermal conductivity in yttria-stabilized zirconia. I. Microstructural investigations using neutron diffuse scattering and atomic-scale simulations.

Diffusion phenomena in atomic layer deposition

“…This compound is used as an electrolyte in solid oxide fuel cells (SOFCs). Ginestra et al [11] have shown that after depositing multilayer structures of Y 2 O 3 and ZrO 2 and annealing up to 950 • C in an oxygen atmosphere, a mixed compound can be produced which outperforms bulk YSZ in terms of conductivity. As a reason for the good conductivity, the small grain size and the multitude of grain boundaries are proposed.…”

Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer Deposition

“…ALD also provides atomic‐level compositional control by selecting the appropriate reactants during each ALD cycle. This compositional control has been utilized to deposit a range of materials, including doped materials,14–16 mixed metal oxides,17–19 and nanolaminates 20–22. This combination of attributes makes ALD ideal for the templated synthesis of nanostructured materials, with such templating previously being demonstrated for metal oxide and metal nitride materials23–25 as well as some metals 26–29.…”

Reaction mechanisms during plasma-assisted atomic layer deposition of metal oxides: A case study for Al2O3

“…Potential application of ALD films in areas such as microsystems, solar cells, flexible electronics, energy storage, and photonics have recently been reported. [9][10][11][12][13][14][15][16][17][18][19] While the material properties and functionality of the films have already been investigated in relative detail, the reaction mechanisms leading to film growth in the O 3 and O 2 plasma based ALD processes have hardly been addressed. Very recently, however, theoretical and experimental investigations of the reaction mechanism of Al 2 O 3 ALD from Al͑CH 3 ͒ 3 ͓trimethylaluminum ͑TMA͔͒ precursor and O 3 were reported by Elliott et al 20 and Goldstein and George.…”