Chemically preintercalated dopamine (DOPA) molecules were used as both reducing agent and carbon precursor to prepare δ-V2O5∙nH2O/C, H2V3O8/C, VO2(B)/C and V2O3/C nanocomposites via hydrothermal treatment or hydrothermal treatment followed by annealing under Ar flow. We found that the phase composition and morphology of the produced composites are influenced by the DOPA:V2O5 ratio used to synthesize (DOPA)xV2O5 precursors through DOPA diffusion into the interlayer region of δ-V2O5∙nH2O framework. The increase of DOPA concentration in the reaction mixture led to more pronounced reduction of vanadium and a higher fraction of carbon in the composites’ structure, as evidenced by XPS and Raman spectroscopy measurements. The electrochemical charge storage properties of the synthesized nanocomposites were evaluated in Li-ion cells with non-aqueous electrolyte. δ-V2O5∙nH2O/C, H2V3O8/C, VO2(B)/C, and V2O3/C electrodes delivered high initial capacities of 214, 252, 279, and 637 mAh·g–1, respectively. The insights provided by this investigation open up the possibility of creating new nanocomposite oxide/carbon electrodes for a variety of applications such as energy storage, sensing and electrochromic devices.
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Low-temperature synthesis of crystalline vanadium oxide films using oxygen plasmas
Vanadium oxide (VOx) compounds feature various polymorphs, including V2O5 and VO2, with attractive temperature-tunable optical and electrical properties. However, to achieve the desired material property, high-temperature post-deposition annealing of as-grown VOx films is mostly needed, limiting its use for low-temperature compatible substrates and processes. Herein, we report on the low-temperature hollow-cathode plasma-enhanced atomic layer deposition (ALD) of crystalline vanadium oxide thin films using tetrakis(ethylmethylamido)vanadium and oxygen plasma as a precursor and coreactant, respectively. To extract the impact of the type of plasma source, VOx samples were also synthesized in an inductively coupled plasma-enhanced ALD reactor. Moreover, we have incorporated in situ Ar-plasma and ex situ thermal annealing to investigate the tunability of VOx structural properties. Our findings confirm that both plasma-ALD techniques were able to synthesize as-grown polycrystalline V2O5 films at 150 °C. Postdeposition thermal annealing converted the as-grown V2O5 films into different crystalline VOx states: V2O3, V4O9, and VO2. The last one, VO2 is particularly interesting as a phase-change material, and the metal-insulator transition around 70 °C has been confirmed using temperature-dependent x-ray diffraction and resistivity measurements.
more » « less- Award ID(s):
- 2150158
- NSF-PAR ID:
- 10515106
- Publisher / Repository:
- AVS
- Date Published:
- Journal Name:
- Journal of Vacuum Science & Technology A
- Volume:
- 41
- Issue:
- 3
- ISSN:
- 0734-2101
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract New deposition techniques for amorphous oxide semiconductors compatible with silicon back end of line manufacturing are needed for 3D monolithic integration of thin‐film electronics. Here, three atomic layer deposition (ALD) processes are compared for the fabrication of amorphous zinc tin oxide (ZTO) channels in bottom‐gate, top‐contact n‐channel transistors. As‐deposited ZTO films, made by ALD at 150–200 °C, exhibit semiconducting, enhancement‐mode behavior with electron mobility as high as 13 cm2V−1s−1, due to a low density of oxygen‐related defects. ZTO deposited at 200 °C using a hybrid thermal‐plasma ALD process with an optimal tin composition of 21%, post‐annealed at 400 °C, shows excellent performance with a record high mobility of 22.1 cm2V–1s–1and a subthreshold slope of 0.29 V dec–1. Increasing the deposition temperature and performing post‐deposition anneals at 300–500 °C lead to an increased density of the X‐ray amorphous ZTO film, improving its electrical properties. By optimizing the ZTO active layer thickness and using a high‐
k gate insulator (ALD Al2O3), the transistor switching voltage is lowered, enabling electrical compatibility with silicon integrated circuits. This work opens the possibility of monolithic integration of ALD ZTO‐based thin‐film electronics with silicon integrated circuits or onto large‐area flexible substrates. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1116/6.0002383
