Large-area nanometer-thin β-Ga2O3 films synthesized via oxide printing of liquid metal gallium

Jacqueline Cooke; Leila Ghadbeigi; Rujun Sun; Arkka Bhattacharyya; Yunshan Wang; Michael A. Scarpulla; Sriram Krishnamoorthy; Berardi Sensale-Rodriguez

doi:10.1117/12.2568170

21 August 2020 Large-area nanometer-thin β-Ga₂O₃ films synthesized via oxide printing of liquid metal gallium

Jacqueline Cooke, Leila Ghadbeigi, Rujun Sun, Arkka Bhattacharyya, Yunshan Wang, Michael A. Scarpulla, Sriram Krishnamoorthy, Berardi Sensale-Rodriguez

Author Affiliations +

Proceedings Volume 11466, UV and Higher Energy Photonics: From Materials to Applications 2020; 1146606 (2020) https://doi.org/10.1117/12.2568170
Event: SPIE Nanoscience + Engineering, 2020, Online Only

Abstract

Exfoliated gallium oxide (Ga₂O₃) has been reported as an ultrathin channel material in field-effect transistors. Unlike in 2D materials with van der Waals forces between stacked layers, weak bonding in β-Ga₂O₃ along the (100) direction enables mechanical exfoliation. The thickness of these exfoliated films has been limited to tens to hundreds of nanometers. Here we summarize our latest work, which followed the process developed by Carey et al., enabling us to attain ~2 nm thick Ga₂O₃ films over a large surface area (< 1 mm²). The films are characterized using optical microscopy, AFM, XPS, Raman spectroscopy, photoluminescence (PL), and TEM. Optical microscope images showed color changes to the film upon annealing. AFM revealed the film thickness to be as thin as 2 nm over areas << 1 mm². XPS and Raman spectra revealed characteristic signatures of β-phase Ga₂O₃. Characteristic PL of Ga₂O₃ was seen in all samples with overall intensity of luminescence increasing after annealing, attributed to increased crystallinity and grain size. Changes in PL after annealing are associated with an increase in oxygen interstitials and a decrease in oxygen vacancies. Lastly, TEM analysis revealed the film as β-phase Ga₂O₃ polycrystalline. Overall, our results demonstrate that annealing of thin films obtained from oxide printing of liquid metal Ga is a non-expensive and straightforward process that can lead to β-Ga₂O₃ films that are nanometer-thin over wafer-scale areas.

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Jacqueline Cooke, Leila Ghadbeigi, Rujun Sun, Arkka Bhattacharyya, Yunshan Wang, Michael A. Scarpulla, Sriram Krishnamoorthy, and Berardi Sensale-Rodriguez "Large-area nanometer-thin β-Ga₂O₃ films synthesized via oxide printing of liquid metal gallium", Proc. SPIE 11466, UV and Higher Energy Photonics: From Materials to Applications 2020, 1146606 (21 August 2020); https://doi.org/10.1117/12.2568170

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