Atomic layer deposition of thin films containing alkali metals

This thesis presents experimental work on thin films of different compounds containing lithium, sodium or potassium has been synthesized by atomic layer deposition (ALD). The overall motivation for this work has been to develop materials and methods to improve lithium ion battery technology by using ALD. A cathode in a lithium ion battery should have a long operating life, be environmentally benign and have high capacity and power density. Vanadium oxides are popular as cathodes in lithium ion batteries due to their relative low price and potentially high capacity. Most studies of vanadium oxide cathodes shows relatively short lifetime of the cathode or relatively fast cathodes. In this work a high power thin film cathode of V2O5 for lithium ion batteries has been developed. The cathode is deposited by ALD using VO(thd)2 and ozone, which displays a rather peculiar type of ALD-growth. This peculiar growth is studied in detail, and the optical properties of these films are investigated. The films have an unusually rough surface, and it was found that a 10nm thick film deposited at 235ºC consisted of individual nano particles. The 10 nm thick cathode has been shown to endure more than 4000 dischargecycles at 120C and almost 1600 cycles while staying within 80% of the original capacity. The same cathode was also shown to sustain discharge rates of 960C which corresponds to a discharge in 3.75s. The power density obtained in this work bridges the gap between super capacitors and batteries and the combination of long lifetime and high discharge rate is not found previously for thin film batteries of V2O5. ALD of lithium containing materials has attracted widespread interest the last few years. The number of known precursors for lithium has grown, but the complete picture is still not understood. Therefore lithium hexamethyldisilazane (LiHMDS) is explored as a precursor for ALD of lithium compounds. The precursor is shown successful in deposition of Li3N, Li2CO3 and LiNbO3. The deposition of Li3N may be an important step to deposit solid electrolytes and the deposition of Li2CO3 proved to be important for proving the growth of oxides using this precursor. When comparing the growth of Li3N and Li2CO3 it was found significant difference in the surface chemistry. The LiNbO3-films were shown to be ferroelectric with an unusually high coercive field. It proved possible to deposit epitaxial LiNbO3 on single crystal substrates of LaAlO3 and Al2O3 and the orientation of