Sol-gel method has been used to coat multiwalled carbon nanotubes (MWCNTs) with zirconia at room temperature and the coated tubes were sintered at high temperature. The samples were characterised by Raman spectroscopy, x-ray diffraction, environmental scanning electron microscope, transmission electron microscopy, and energy-dispersive x-ray analyses. The performance of the coated-MWCNTs was investigated as a function of temperature. The TGA studies indicated that sintering of coated-MWCNTs has improved its oxidation resistance and this improvement is related to the proper selection of sintering temperature.
This article demonstrates a method to fabricate crystalline Ba0.5Sr0.5TiO3 (BST) thin films at a lower temperature of ≈300 °C using an excimer laser by an alternating depositing and annealing process. Firstly, a BST thin film with a thickness of ≈120 nm is deposited at 300 °C (laser energy of ≈2 J cm−2) and subsequently laser annealed (66 mJ cm−2) at 300 °C. This process is repeated five times to obtain thicker device quality films. XRD patterns, TEM, Raman, and UV–Vis–NIR spectroscopy confirm that phase formation of BST thin films has taken place. The band edge value for BST thin films is observed to decrease systematically from 4.65 eV (amorphous, 300 °C) to 3.56 eV (5‐layers, crystalline, 300 °C). A varactor device with a Circular Patch Capacitor (CPC) structure is patterned on the five‐stage laser annealed BST thin films processed at 300 °C, which shows a microwave tunability of 34% at 1 GHz compared to conventionally deposited BST films (prepared at 700 °C). This study provides a way for fabricating ferroelectric thin film based tunable devices at low temperatures, making the process compatible with low melting substrates in flexible electronics and other situations where there is a temperature constraint.
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