Metal organic framework thin films deposited by ALD/MLD for gas adsorption and storage

Metal Organic Frameworks (MOFs) are currently considered an important field of research. They have a wide range of potential applications including energy and gas storage, catalysis and other biological applications. The non-stop miniaturization in technology applications has shifted the huge interest in MOFs towards the fabrication of MOF thin films. MOF thin films can show tremendous potential in sensors application. In order to investigate this area further, the state-of-art ALD/MLD deposition technique to fabricate MOF thin films are used. ALD/MLD technique offers advantages in synthesizing pinhole free, high quality thin films. The method has been proven to be successful for fabrication of MOF thin films on silicon substrates. Our main purpose is to fabricate new MOF thin film structures, which can be experimented and used in the application of gas storage in the future. Our concentration was on CPO-27 MOF structures which are known on the bulk level for the storage of nitric oxide gas as well as lanthanide based MOF thin films, which can be experimented for hydrogen gas storage. In this work, CPO-27 like hybrid thin films were fabricated. Using three different metals magnesium, cobalt and nickel. The inorganic precursors were Mg(thd)2, Co(thd)2 and Ni(thd)2 (thd= 2,2,6,6,-tetramethyl-3,5-heptanedione) and 2,5-dihydroxyterephthalic acid was the organic precursor. Deposition of ytterbium, erbium and yttrium terephthalate hybrid thin films were also deposited using ALD/MLD. Yb(thd)2, (Yb(DPDMG)3) and Er(thd)2 were used as inorganic precursors and Terephthalic acid was the organic precursor. Barium terephthalate thin film was deposited as references for our current work. The films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray reflectivity (XRR) and grazing incidence X-ray diffraction (GIXRD). All of our novel processes lead to deposition of thin films, which were found to be amorphous, except the reference film of barium terephthalate. The films deposited with Mg-2,5-dihydroxyterephthalate showed stability against high relative humidity and heat treatments. Thicknesses, densities and growth per cycle values were studied for the films deposited from erbium, ytterbium and yttrium with terephthalic acid as the organic part. Through the obtained results, a linear relationship between thickness and the number of cycle was found as well as a linear relationship between growth per cycle value and number of cycles. Suggestions for further research based on the conclusions of this work was introduced