Surface-Dependent Performance of Ultrathin TiN Films as an Electrically Conducting Li Diffusion Barrier for Li-Ion-Based Devices
journal contributionposted on 18.08.2020, 19:11 by Jan Speulmanns, Alireza M. Kia, Kati Kühnel, Sascha Bönhardt, Wenke Weinreich
An in-depth understanding of lithium (Li) diffusion barriers is a crucial factor for enabling Li-ion-based devices such as three-dimensional (3D) thin-film batteries and synaptic redox transistors integrated on silicon substrates. Diffusion of Li ions into silicon can damage the surrounding components, detach the device itself, lead to battery capacity loss, and cause an uncontrolled change of the transistor channel conductance. In this study, we analyze for the first time ultrathin 10 nm titanium nitride (TiN) films as a bifunctional Li-ion diffusion barrier and current collector. Thermal atomic layer deposition (ALD) and pulsed chemical vapor deposition (pCVD) are employed for manufacturing ultrathin films. The 10 nm ALD films demonstrate excellent blocking capability with an insertion of only 0.03 Li per TiN formula unit exceeding 200 galvanostatic cycles at 3 μA/cm2 between 0.05 and 3 V versus Li/Li+. An ultralow electrical resistivity of 115 μΩ cm is obtained. In contrast, a partial barrier breakdown is observed for 10 nm pCVD films. High surface quality with low contamination is identified as a key factor for the excellent performance of ALD TiN. Conformal deposition of 10 nm ALD TiN in 3D structures with high aspect ratios of up to 20:1 is demonstrated. The measured capacities of the surface area-enhanced samples are in good agreement with the expected values. High-temperature blocking capability is proven for a typical electrode crystallization step. Ultrathin ALD TiN is an ideal candidate for an electrically conducting Li-ion diffusion barrier for Si-integrated devices.
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3 D structureselectrode crystallization stepUltrathin TiN FilmsTiN formula unitElectrically Conducting Li Diffusio...Ultrathin ALD TiNlayer depositionALD TiNHigh surface qualitymanufacturing ultrathin filmsLi-ion-based devices115 μΩ cmSurface-Dependent Performance0.03 LiLi-ion diffusion barrier3 μ10 nm pCVD filmsbarrier breakdownSi-integrated devices10 nm ALD filmssynaptic redox transistorsthin-film batteriesbifunctional Li-ion diffusion barrierLi ionsbattery capacity loss10 nm ALD TiN3 VConformal depositionLi-Ion-Based Devicestime ultrathin 10 nm titanium nitridediffusion barrierschemical vapor depositiontransistor channel conductancesilicon substratesaspect ratios200 galvanostatic cyclessurface area-enhanced samples