Non-melt selective enhancement of crystalline structure in molybdenum thin films using femtosecond laser pulses

It is challenging to crystalize a thin film of higher melting temperature when deposited on a substrate with comparatively lower melting point. Trading such disparities in thermal properties between a thin film and its substrate can significantly impede material processing. We report a novel solid-s...

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Veröffentlicht in:Journal of physics. D, Applied physics Applied physics, 2022-03, Vol.55 (11), p.115301
Hauptverfasser: Sharif, Ayesha, Farid, Nazar, Wang, Mingqing, Vijayaraghavan, Rajani K, Choy, Kwang-Leong, McNally, Patrick J, O’Connor, Gerard M
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Sprache:eng
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Zusammenfassung:It is challenging to crystalize a thin film of higher melting temperature when deposited on a substrate with comparatively lower melting point. Trading such disparities in thermal properties between a thin film and its substrate can significantly impede material processing. We report a novel solid-state crystallization process for annealing of high melting point molybdenum thin films. A systematic investigation of laser induced annealing from single pulse to high pulse overlapping is reported upon scanning at fluences lower than the threshold required for the damage/ablation of molybdenum thin films. The approach allows better control of the grain size by changing the applied laser fluence. Atomic force microscopy surface morphology and x-ray diffraction (XRD) analysis reveal significant improvements in the average polycrystalline grain size after laser annealing; the sheet resistance was reduced by 19% of the initial value measured by a Four-point probe system. XRD confirms the enlargement of the single crystal grain size. No melting was evident, although a change in the close packing, shape and size of nanoscale polycrystalline grains is observed. Ultrashort laser induced crystallinity greatly enhances the electrical properties; Hall measurements reinforced that the overall carrier concentration increases after scanning at different laser fluences. The proposed method, based on the aggregation and subsequent growth of polycrystalline and single crystal-grains, leading to enhanced crystallization, has potential to be applicable in thin film processing industry for their wide applications.
ISSN:0022-3727
1361-6463
DOI:10.1088/1361-6463/ac3e91