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

Sutapa Dey; Anusmita Chakravorty; Shashi Bhusan Mishra; Nasima Khatun; Arnab Hazra; Birabar Ranjit Kumar Nanda; Chandran Sudakar; Debdulal Kabiraj; Somnath C. Roy

doi:10.1039/D1NA00666E

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

Sutapa Dey,

^a Anusmita Chakravorty,^b Shashi Bhusan Mishra,

^c Nasima Khatun,

^a Arnab Hazra,^d Birabar Ranjit Kumar Nanda,

^c Chandran Sudakar,

^e Debdulal Kabiraj^b and Somnath C. Roy

*^a

Author affiliations

* Corresponding authors

^a Semiconducting Oxide Materials, Nanostructures and Tailored Heterojunction (SOMNaTH) Lab, Functional Oxide Research Group (FORG), Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
E-mail: somnath@iitm.ac.in

^b Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India

^c Condensed Matter Theory and Computational Lab, Department of Physics and Center for Atomistic Modelling and Materials Design (CAMMD), Indian Institute of Technology Madras, Chennai 600036, India

^d Department of Electrical & Electronics Engineering, Birla Institute of Technology & Science-Pilani, Pilani Campus, Pilani-333031, Rajasthan, India

^e Multifunctional Materials Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India

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.

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Article information

DOI: https://doi.org/10.1039/D1NA00666E
Article type: Paper
Submitted: 05 Sep 2021
Accepted: 11 Nov 2021
First published: 15 Nov 2021
This article is Open Access

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Nanoscale Adv., 2022,4, 241-249

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

S. Dey, A. Chakravorty, S. B. Mishra, N. Khatun, A. Hazra, B. R. K. Nanda, C. Sudakar, D. Kabiraj and S. C. Roy, Nanoscale Adv., 2022, 4, 241 DOI: 10.1039/D1NA00666E

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