Delafossite CuFeO2 thin films via aerosol assisted CVD

Significance 

Over the past few years, a tremendous increase in the population and industrialization have overstrained the presently available energy sources. As such development of alternative and efficient energy sources is highly desirable. This, however, has to be in line with the set regulations that have been recently set to mitigate the environmental pollution and climate changes associated with energy consumption. To this note, several approaches for developing clean and sustainable energy sources have been initiated. In a recently published literature, solar energy has been directly converted into chemical fuels through photo-assisted water splitting. Unfortunately, they are associated with low solar spectrum absorption efficiency that limits their large-scale utilization. Alternatively, delafossite materials, specifically CuFeO2, have been used in hydrogen generation owing to its conductivity, electrical and optical properties.

Presently, several methods for CuFeO2 synthesis including electrodeposition, spin coating spray pyrolysis among others have been developed. However, efficient techniques for synthesis of CuFeO2 that will ensure proper control of the morphology, crystalline structure and composition have not been fully explored.

To this note, a group of researchers led by Dr. Mario Miki-Yoshida at CIMAV, where Ph.D. candidate Pedro Piza-Ruiz and Dr. Saenz-Trevizo investigated the optimal conditions for the synthesis of the delafossite CuFeO2 based on the aerosol-assisted CVD approach. Technically, the synthesis process was repeated several times until a molar ratio of copper to iron in the synthesized films was recorded as one by using the titanium oxide coated borosilicate glass, as a substrate. Their fascinating research work is currently published in the research journal, Ceramics International.

In brief, the research team cross-examined the feasibility of using aerosol-assisted CVD method in synthesizing ternary oxide materials. Next, they utilized a one-step method that did not require any treatment processes after deposition. The initial average atomic ratio of copper to iron was approximated using the energy dispersive x-ray spectroscopy technique, which was also later used as an indicator in the synthesis of CuFeO2. In addition, different characterization techniques such as Raman spectroscopy, atomic force microscopy and x-ray diffraction were utilized to control the composition, morphology, and microstructure for effective delafossite growth.

The authors observed that the polycrystalline CuFeO2 was formed in the rhombohedral phase. The formation of the rhombohedral phase was attributed to the suitable combination of the copper and iron precursors, which transform during the complex reaction mechanisms initiated by the aerosol-assisted CVD method into the desire phase. Consequently, the copper oxide was observed coexisting with the formed CuFeO2 even though in small amounts. Furthermore, a slight influence of titanium oxide and zinc oxide buffer layers on the deposited copper and iron, grain size and thickness were observed thus, confirming the existence of delafossite material.

In summary, CIMAV scientists successfully demonstrated the application of the synthesized CuFeO2 in light absorption. Even though the influence in the coexisting copper oxide on the applications such as water splitting have not been fully presented, the method proves suitable for the synthesis of CuFeO2. This will pave the way for developing alternative sustainable energy sources not only to meet the increasing demands but also to address the environmental concerns.

Delafossite CuFeO2 thin films via aerosol assisted CVD: Synthesis and characterization - Advances in Engineering
illustrate the simplicity of the AACVD process, which is controlled at a great extent by the reactants in the precursor droplet and temperature.

About the author

Pedro Piza-Ruiz is a Ph.D. candidate in Materials Science as part of collaboration between the Tecnológico Nacional de Mexico (TNM) campus Cancun and CIMAV. He is studying the synthesis of nanostructured metal oxide thin films for artificial photosynthesis application. Part of his work includes finding appropriate conditions for the preparation of ternary oxides, such as polycrystalline delafossite CuFeO2, under atmospheric conditions and, without the need of further thermal annealing.

He received his bachelor’s degree in Electrical Engineering at the Universidad Autónoma de Baja California (UABC) in 2005, followed by a master’s degree in Electro-Optics in 2007 from CISESE. Since 2011, he has been a Research Scientist for the National Nanotechnology Lab at CIMAV. His job includes the design and fabrication of customized Aerosol Assisted CVD chambers for the synthesis of nanoscale materials as well as their characterization using UV-Vis-NIR and Raman Spectroscopy.

About the author

Angelica Saenz-Trevizo is currently a postdoctoral scholar at the University of Southern California. She received her Ph.D. in Materials Science at CIMAV in 2016. Then, she continued to work as a Research Scientist for the National Nanotechnology Lab at CIMAV, until early 2018.

Her activities involved the characterization of materials by means of different techniques, the interpretation and analysis of the collected data, as well as the writing of scientific reports. She received her bachelor’s degree in Mechanical Engineering in 2008 and her master’s degree in Manufacturing in 2011. Part of her master job was to scale up an AACVD prototype for the synthesis of nanoscale metal oxides and later on, decided to explore the microstructural and optical properties of such nanostructures. Her Ph.D. dissertation included the synthesis, characterization and application of nanoscale materials as photocatalysts. This research was achieved using the combination of different nanostructured metal oxides in a core-shell configuration and, the use of different light sources to prove their efficiency.

In consequence, her research interests are focused in the synthesis, characterization and application of nanoscale materials for energy generation and water cleaning. Her current position involves the study of the mechanical properties of multilayered materials prepared via magnetron sputtering, which will allow for a comprehensive examination of the properties of nanostructures.

Reference

Pizá-Ruiz, P., Sáenz-Trevizo, A., Verde-Gómez, Y., Amézaga-Madrid, P., & Miki-Yoshida, M. (2019). Delafossite CuFeO2 thin films via aerosol assisted CVD: Synthesis and characterization. Ceramics International, 45(1), 1156-1162.

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