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Tuning of structural and optical properties of reactively sputtered MoOx films

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Abstract

MoOx films were deposited using reactive sputtering of Mo under varying oxygen flow in the plasma ambient. The films showed a broad X-ray diffraction peak corresponding to MoOx structure. The surface morphology has been influenced significantly with the oxygen content in the plasma during the process of film deposition. The as-deposited films were porous at lower oxygen flow rate (< 10 sccm), while it showed coarse structure at the higher flow rates (> 15 sccm). The compositional analysis revealed that the films are sub-stoichiometric and the weight ratio of O/Mo varied from 1.5 to 2 in the O2 flow range of 5–25 sccm. The sub-stoichiometric phases of MoO3 were detected from FTIR analysis. The optical characteristics showed that the films were highly transparent (> 85%) in the visible region, and exhibited direct band gap energy of 3.66 eV. The optical constants, i.e., refractive index (n) and extinction coefficient (k) evaluated from spectroscopic ellipsometry were found to be 2.03 and 0.0035, respectively at the wavelength of 600 nm, for the films deposited at the optimum conditions. The films showed a broad luminescence with a strong emission at 400 nm, which would help improve the blue response of solar cells. The Al/MoOx/Si device showed a maximum barrier height, \({\phi }_{b}\) ~0.86 eV and a minimum leakage current, Io ~ 5.81 × 10–11 A at the higher O2 flow rates (> 15 sccm), which changed significantly with the oxygen flow rate. The study demonstrates the tunability of structural and optical characteristics, which have been significantly influenced by tuning the plasma ambient during the film deposition.

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Acknowledgements

The authors are thankful to CSIR-National Physical Laboratory, New Delhi, for the experimental facilities. The author Abhishek Kumar gratefully acknowledges the support of Ministry of New and Renewable Energy (MNRE), Govt. of India for providing NREF fellowship (Ref. No. 10/2(2)2017-HRD, Dt. 30.03.2018).

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Authors and Affiliations

  1. CSIR-National Physical Laboratory, New Delhi, 110012, India

    Abhishek Kumar, Shweta Tomer, Sanjay Kumar Srivastava, S. N. Singh & Prathap Pathi

  2. Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, UP, 201002, India

    Abhishek Kumar, Shweta Tomer, Sanjay Kumar Srivastava & Prathap Pathi

  3. National Institute of Solar Energy, Gurugram, Haryana, 122003, India

    Mrinal Dutta

  4. Solid State Physics Laboratory, DRDO, Timarpur, Delhi, 110054, India

    Pritty Rao

  5. CSIR-Advanced Materials and Processes Research Institute, Bhopal, 462026, India

    Vandana

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Contributions

Abhishek Kumar: Writing—original draft, Investigation, Data curation, Conceptualization. Mrinal Dutta: Review & Editing, Data Curation. Shweta Tomer: Data Curation. Pritty Rao: Data Curation. Vandana: Review & Editing, Supervision. Sanjay Kumar Srivastava: Review & Editing. S. N. Singh: Review & Editing, Supervision. Prathap Pathi: Review & Editing, Data curation, Supervision, Resources.

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Correspondence to Prathap Pathi.

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Kumar, A., Dutta, M., Tomer, S. et al. Tuning of structural and optical properties of reactively sputtered MoOx films. J Mater Sci: Mater Electron 35, 612 (2024). https://doi.org/10.1007/s10854-024-12324-x

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