from the conferences organized by TANGER Ltd.
The development of micro- and nanoscale power sources for micro size electronic devices such as wireless sensors, biomedical implants, and smart cards is an important task. In this work, the processes of synthesis uniform lithium oxide, cobalt oxide, and lithium cobalt oxide thin films using atomic layer deposition (ALD) method were studied. Lithium tert-butoxide (LiOtBu) and cobaltocene (Co(Cp)2) were used as precursors. Remote oxygen plasma was used as a counter-reagent. The synthesis was carried out at 300 °C. The growth rate and uniformity of the films were controlled by adjustment the precursor's evaporation temperature, reagent pulse time, and purge times. Monocrystalline silicon and stainless steel (SS316) were used as substrates. The films were studied by spectral ellipsometry, energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD). Results showed that an increase the purge time to 10 s after the reagent pulse positively affects the uniformity of the films. The growth rates of Li-O and Co-O systems were 0.080±0.010 nm/cycle and 0.022±0.003 nm/cycle, respectively. XRD data showed the presence of the crystalline CoO phase for the Co-O and the presence of the LiCoO2 for Li-Co-O samples. The optimized synthesis parameters determined for Li-O and Co-O were subsequently used to synthesize Li-Co-O (LiCoO2-x) system. According to the growth rates of Li-O and Co-O, the ratio of Li and Co pulses was set as 1/5. XRD data showed well crystalline LiCoO2 textured in (003) direction for as-deposited Li-Co-O thin films. According to cyclic voltammetry (CV), there is a pronounced peak characterizing of the change in the oxidation state of cobalt from 3+ to 4+. Based on cyclic tests, the Li-Co-O films have high coulombic efficiency.
Keywords: Atomic layer deposition, lithium oxide, cobalt oxide, lithium cobalt oxide, lithium-ion batteries, solid-state lithium-ion batteries© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.