Publications by authors named "Juho Heiska"

Thin films of two ambipolar lithium-organic electrode materials, LiDHTP and LiDHTP, are grown from gaseous precursors, Li(thd) (tetramethyl heptanedione) and DHTP (dihydroxyterephthalic acid). These precursors are pulsed into the reactor in a sequential manner like in atomic/molecular layer deposition, but the reaction product, the di- or the tetra-lithium salt, is controlled by adjusting the precursor pulse lengths.

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Atomic layer deposition (ALD) is the fastest growing thin-film technology in microelectronics, but it is also recognized as a promising fabrication strategy for various alkali-metal-based thin films in emerging energy technologies, the spearhead application being the Li-ion battery. Since the pioneering work in 2009 for Li-containing thin films, the field has been rapidly growing and also widened from lithium to other alkali metals. Moreover, alkali-metal-based metal-organic thin films have been successfully grown by combining molecular layer deposition (MLD) cycles of the organic molecules with the ALD cycles of the alkali metal precursor.

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Two new atomic/molecular layer deposition processes for depositing crystalline metal-organic thin films, built from 1,4-benzenedisulfonate (BDS) as the organic linker and Cu or Li as the metal node, are reported. The processes yield in-situ crystalline but hydrated Cu-BDS and Li-BDS films; in the former case, the crystal structure is of a previously known metal-organic-framework-like structure, while in the latter case not known from previous studies. Both hydrated materials can be readily dried to obtain the crystalline unhydrated phases.

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Intercalated metal-organic framework (iMOF) type electrochemically active aromatic metal carboxylates are intriguing material candidates for various energy storage devices and microelectronics. In this work, we grow in situ crystalline thin films of such materials through atomic/molecular layer deposition (ALD/MLD); the remarkable benefit of this approach is the possibility to evaluate their electrochemical properties in a simple cell configuration without any additives. Five organic linkers are investigated in combination with lithium: terephthalic acid (TPA), 3,5-pyridinedicarboxylic acid (PDC), 2,6-naphthalenedicarboxylic acid (NDC), 4,4'-biphenyldicarboxylic acid (BPDC), and 4,4'-azobenzenedicarboxylic acid (AZO).

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When a conventional lithium-ion battery (LIB) is cycled, a solid electrolyte interphase (SEI) forms on the surface of a negative electrode, passivating it but also depleting the capacity of the battery. Most commercial LIBs utilize a carbonate-based electrolyte, which at least temporarily leads to the formation of lithium alkyl carbonates (ROCOLi) as the main organic SEI component. Here, we pioneer the use of atomic/molecular layer deposition (ALD/MLD) for the fabrication of lithium ethyl glycoxide (LiEG) and lithium ethylene carbonate (LiEGCO) thin films, to mimic the lithium alkyl carbonate component of the SEI.

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Control of the redox potential of lithium terephthalate LiTP anode material is demonstrated by functionalizing its terephthalate backbone with an electron-donating amino group; this lowers - as intended - the redox potential of LiTP by 0.14 V. The two Li-organic electrode materials, LiTP and LiTP-NH, are fabricated as crystalline thin films from gaseous precursors using the atomic/molecular layer deposition (ALD/MLD) technique.

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