Effects of SiO2 coating and thermal annealing on the electro-optical properties of InSe/Ag2O heterojunctions for enhanced infrared absorption, negative conductance and capacitance, and 5G/6G band filtering

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ACCEPTED MANUSCRIPT Effects of SiO2 coating and thermal annealing on the electro-optical properties of InSe/Ag2O heterojunctions for enhanced infrared absorption, negative conductance and capacitance, and 5G/6G band filtering Sabah Algarni, A F Qasrawi and Najla M Khusayfan

Accepted Manuscript online 18 November 2025 • © 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.

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DOI 10.1088/1402-4896/ae20d3 DownloadAccepted Manuscript PDF Authors Download PDF Article metrics 2 Total downloads

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Share this article Hide article information Dates Received 26 July 2025 Revised 8 November 2025 Accepted 18 November 2025 Accepted Manuscript online 18 November 2025 Peer review information Method: Single Anonymous Revisions: 1 Screened for originality? Yes

Journal RSS Sign up for new issue notifications Abstract Herein InSe/Ag2O (IA) heterojunctions are fabricated to be utilized as multifunctional devices suiting electro-optical applications. The IA interfaces which are prepared by the thermal evaporation technique represented an amorphous/crystalline structure with enhanced crystallinity and engineered optical and electrical property achieved by the thermal annealing or SiO2 nanosheets coating. Optically, coating Ag2O onto InSe resulted in increased infrared (IR) light absorption by more than 900% and reduced energy band gap from 1.40 eV to 0.82 eV. The annealing and SiO2 coating also enhanced the IR light absorption by 369% and 671%, respectively. In addition, using the IA interfaces as planer grating waveguides allowed formation of negative conductance (NG) sources and subterahertz band filters operating in the driving frequency domain of 1.20-1.80 GHz. Coating the IA waveguides with SiO2 nanosheets suppressed the NG effect and formed negative capacitance (NC) effects. Whilst thermal annealing resulted in removal of the NG effect and forced cutoff frequency values of 96 GHz at driving frequency of 1.80 GHz. The suitability of these waveguides to the standard quad band frequency domains used in 5G/6G communication technology makes the IA waveguides attractive for electronic applications as NG and NC sources suitable for signal amplification, noise reduction, and as heterodyne and quad band filters.