Atomic Layer Deposition (ALD) has emerged as a promising technique for fabricating thin films that enhance the performance of solid oxide fuel cells and solid oxide electrolysis cells. ALD allows for precise control over film thickness and composition at the atomic level, resulting in uniform and dense thin films. These characteristics enable the deposition of thin, homogeneous layers of various materials onto the porous electrode surfaces of solid oxide cells, thereby increasing electrochemical activity and reducing activation losses. Additionally, thin-film electrolytes produced through ALD can achieve high ionic conductivity and low ohmic losses, facilitating a reduction in the operating temperature of solid oxide cells. This review summarizes recent research trends in applying ALD technology to the fuel electrode, air electrode, and electrolyte of solid oxide cells and discusses design strategies aimed at improving efficiency and long-term stability.

In this study, Yttria-stabilized zirconia (YSZ) functional layers were applied with different thin-film fabrication process such as sputtering and atomic layer deposition (ALD) to enhance oxygen reduction reaction (ORR) for solid oxide fuel cells. We confirmed that the YSZ functional layer deposited with sputtering showed relatively low grain boundary density, while the YSZ functional layer deposited with the ALD technique clearly indicated high grain boundary density through scanning electron microscopy (SEM) and X-ray diffractometry (XRD) results. The YSZ functional layer coated with the ALD technique revealed that more ORR kinetics can occur using high grain boundary density than the functional layer deposited with sputtering. The peak power density of the SOFC deposited with ALD YSZ indicates 2-folds enhancement than the pristine SOFC.

The energy saving effect of reactant plasma in Atomic Layer Deposition (ALD) of ultrathin solid oxide fuel cell electrolyte was examined by measuring electrical current in real time. Actuating a plasma generator led to a remarkable change in electric current and therefore a Plasma Enhanced ALD (PE-ALD) Yttria-Stabilized Zirconia (YSZ) supercycle demanded ~12% higher process energy than a Thermal ALD (T-ALD) YSZ supercycle. Nonetheless, because PE-ALD YSZ electrolyte providing higher growth rate and higher gas tightness needed 2 times smaller cycle number compared to T-ALD YSZ electrolyte, applying oxygen plasma in ALD of YSZ electrolyte resultantly reduced total process energy by ~44%.

High-k dielectric thin films are widely applied in energy conversion/storage and information storage devices such as Dynamic Random access Memory (DRAM), Multilayer Ceramic Capacitor (MLCC), thermoelectric devices, etc. Among them, perovskite thin films, for instance, strontium titanate (STO) and barium titanate (BTO) are known to have extremely superior dielectric properties. Atomic layer deposition (ALD), can deposit thin films through atomic layering producing uniform and conformal high-k thin films with precise thickness control. While relatively low crystallinity of film quality due to low deposition temperatures of ALD can develop practical issues, they can be overcome by employing additional processes such as thermal annealing, plasma treatment, and seed layering. ALD, STO and BTO thin films treated with these additional processes demonstrate more improved crystallinity and electrical properties. In this paper, the processes to enhance properties of ALD high-k thin films, BTO and STO films are reviewed. Perspectives into high quality ALD high-k thin films as well as current efforts to further improve the film quality are discussed.

ZrO₂ film is widely used for high-k applications and also has good mechanical properties. This paper covers the study of the properties of ZrO₂ film deposited by atomic layer deposition (ALD) using TEMA Zr and water in the temperature range of 110 to 250^oC for potential application in flexible-device fabrication. At a low deposition temperature, ALD ZrO₂ films showed a uniform growth rate of ~1 Å per cycle, good uniformity, partial crystallinity, and smooth surface. ZrO₂ can also be deposited on the trench structure with a high aspect ratio (~1:50), but conformality needs to be improved for practical applications.