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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO₂ nanorods.

ABSTRACT: Irradiation of materials by high energy (∼MeV) ions causes intense electronic excitations through inelastic transfer of energy that significantly modifies physicochemical properties. We report the effect of 100 MeV Ag ion irradiation and resultant localized (∼few nm) thermal spike on vertically oriented TiO₂ nanorods (∼100 nm width) towards tailoring their structural and electronic properties. Rapid quenching of the thermal spike induced molten state within ∼0.5 picosecond results in a distortion in the crystalline structure that increases with increasing fluences (ions per cm²). Microstructural investigations reveal ion track formation along with a corrugated surface of the nanorods. The thermal spike simulation validates the experimental observation of the ion track dimension (∼10 nm diameter) and melting of the nanorods. The optical absorption study shows direct bandgap values of 3.11 eV (pristine) and 3.23 eV (5 × 10¹² ions per cm²) and an indirect bandgap value of 3.10 eV for the highest fluence (5 × 10¹³ ions per cm²). First principles electronic structure calculations corroborate the direct-to-indirect transition that is attributed to the structural distortion at the highest fluence. This work presents a unique technique to selectively tune the properties of nanorods for versatile applications.

SUBMITTER: Dey S

PROVIDER: S-EPMC9419832 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature

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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO<sub>2</sub> nanorods.

Dey Sutapa S Chakravorty Anusmita A Mishra Shashi Bhusan SB Khatun Nasima N Hazra Arnab A Nanda Birabar Ranjit Kumar BRK Sudakar Chandran C Kabiraj Debdulal D Roy Somnath C SC

Nanoscale advances 20211115 1

Irradiation of materials by high energy (∼MeV) ions causes intense electronic excitations through inelastic transfer of energy that significantly modifies physicochemical properties. We report the effect of 100 MeV Ag ion irradiation and resultant localized (∼few nm) thermal spike on vertically oriented TiO<sub>2</sub> nanorods (∼100 nm width) towards tailoring their structural and electronic properties. Rapid quenching of the thermal spike induced molten state within ∼0.5 picosecond results in ...[more]

PMID: 36132944

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Project description:Understanding the electrical conduction properties of a single nanostructure is essential for gaining insight into the fundamental charge transport through 1D materials and also for exploring the collective behavior of an array of such nanostructures. TiO2 nanostructures, such as electrochemically grown nanotubes, have been widely studied in recent times for several applications. The electrolyte plays a vital role in deciding the morphology, which, in turn, governs the charge transport behavior. Here we present a comparative study of the charge transport through a single TiO2 nanotube grown by electrochemical anodization using ethylene glycol and dimethyl sulphoxide electrolytes. The individual nanotubes are assembled into nanodevices using photolithography without relying on complex and sophisticated process like electron beam lithography or focused ion beam deposition. The electric field dependent charge transport properties show Schottky emission at a lower field regime and Poole-Frenkel emission in the higher region. The temperature-dependent electrical conduction (110 K-410 K) is mediated by two thermal activation processes, attributed to shallow impurities in the low-temperature range (T < 230 K) and to the donors at deep intermediate levels at higher temperatures (T > 230 K). The activation energies for EG based nanotubes are found to be higher than those for DMSO nanotubes owing to the double wall morphology of the formed tubes. Also, the study of the electrical breakdown phenomena of these nanotubes reveals three distinct categories of collapse. 'Model A' type breakdown is characterized by a stepwise rise of the current up to the breakdown point and a fall to zero following a non-uniform step by step decrease, which is driven by crack formation near the electrode interface and its propagation. 'Model B' shows a transient rise and fall in current, leading to breakdown due to electromigration, whereas 'Model C' type breakdown observed in a bundle of nanotubes shows a mixed trend of 'Model A' and 'Model B'. The data and analysis provide insight into the current limit through an individual nanotube or bundle of nanotubes and will be useful for designing prototype nanodevices from titania nanostructures.

Project description:A new synthetic method to grow O-deficient rutile TiO2(s) nanorods (NRs) and nanowires (NWs) by a vapor-solid reaction growth method is developed. TiCl4(g) was employed to react with commercially supplied CaTiO3(s) (size 2-4 μm) at 973 K under atmospheric pressure to generate TiO2(s) NRs (diameters 80-120 nm, lengths 1-4 μm). The reaction employing TiCl4(g) and CaO(s) at 973 K also generated CaTiO3(s) (size 4-13 μm) as the intermediate which reacted further with TiCl4(g) to produce NWs (diameters 80-120 nm, lengths 4-15 μm). This is the first report of 1D rutile TiO2(s) nanostructure with such a high aspect ratio. Both of the NRs and the NWs, with compositions TiO1.81 and TiO1.65, respectively, were single crystals grown in the [001] direction. Their morphology was affected by the reaction temperature, the concentration of TiCl4(g), and the particle size of CaTiO3(s). The NRs and the NWs were investigated as anode materials for Li+-ion batteries. At constant current rates 1, 2, and 5 C (1 C = 170 mA g-1) for 100 cycles, the cycling (1.0-3.0 V) performance data of the NRs were 146, 123, and 104 mA h g-1, respectively. On the other hand, the cycling performance data of the NWs were 120, 80, and 52 mA h g-1, respectively. This is attributed to the high Li+ ion diffusion rate (D Li+ ) of the NRs (29.52 × 10-15 cm2 s-1), which exceeds that of the NWs (8.61 × 10-15 cm2 s-1). Although the [001] growth direction of the NR crystals would provide the fastest channels for the diffusion of Li+ ions and enhance the battery capacity, the extremely long channels in the NWs could hamper the diffusion of the Li+ ions. The O-deficiency in the structure would increase the conductivity of the electrode material and improve the stable cycling stability of the batteries also. The long-term cycling test at 2 C for the battery constructed from the NRs retained 121 mA h g-1 after 200 cycles and 99.2 mA h g-1 after 800 cycles. The device has an excellent long-term cycling stability with a loss of only 0.04% per cycle.

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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO₂ nanorods.

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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO<sub>2</sub> nanorods.

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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO2 nanorods.

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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO<sub>2</sub> nanorods.

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OmicsDI is part of the ELIXIR infrastructure

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Localized thermal spike driven morphology and electronic structure transformation in swift heavy ion irradiated TiO₂ nanorods.