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<p>Mg-doped ZnO (Zn<sub>0.85</sub>Mg<sub>0.15</sub>O) thin films with thicknesses of 20, 50, and 100&#xa0;nm were deposited on ITO-coated glass substrates by pulsed laser deposition and integrated into Au/Zn<sub>0.85</sub>Mg<sub>0.15</sub>O/ITO metal–insulator–metal (MIM) capacitors for non-volatile memory applications. Structural analysis confirmed single-phase hexagonal wurtzite ZnO with strong c-axis orientation and improved crystallinity as the film thickness increased. Morphological and AFM studies revealed dense, uniform grains and a systematic increase in surface roughness due to grain coalescence at higher thickness. Electrical measurements showed symmetric, stable <i>I</i>–<i>V</i> characteristics with thickness-dependent leakage current, consistent with ohmic, bulk-controlled conduction dominated by thermally activated carriers. Capacitance–voltage and dielectric measurements evidenced ideal MIM-type dielectric response with clear thickness scaling, enhanced permittivity, and reduced loss tangent for thicker films. Ferroelectric-like P–V hysteresis loops, arising from defect-dipole reorientation and strain-induced local symmetry breaking associated with Mg<sup>2</sup>⁺ substitution at Zn<sup>2</sup>⁺ sites, confirmed reversible polarization switching with a systematic increase in remanent polarization and memory window from 20 to 100&#xa0;nm. Endurance tests on the 50-nm device showed that the memory window decreases only from 0.52 to 0.47&#xa0;V over 5000 bipolar cycles (≈ 9.6% fatigue), while retention measurements reveal a similar ~ 10% reduction of the memory window over 10<sup>6</sup> s, demonstrating slow, quasi-logarithmic polarization decay and stable charge storage over extended cycling and time. These findings identify thickness engineering as a key handle for optimizing charge storage, endurance, and retention in Mg-doped ZnO MIM capacitors, underscoring their potential for next-generation non-volatile memory devices.</p>

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Enhanced charge storage and ferroelectric-like switching in PLD-grown Zn0.85Mg0.15O MIM capacitors via thickness engineering for non-volatile memory devices

  • 期刊论文

  • 发表日期：

    2026年6月25日

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  • Sunena Subhash,
  • Sudheendran Kooriyattil,
  • T. S. Akhil Raman,
  • S. Shyam Shankar,
  • K. C. James Raju

摘要

Mg-doped ZnO (Zn0.85Mg0.15O) thin films with thicknesses of 20, 50, and 100 nm were deposited on ITO-coated glass substrates by pulsed laser deposition and integrated into Au/Zn0.85Mg0.15O/ITO metal–insulator–metal (MIM) capacitors for non-volatile memory applications. Structural analysis confirmed single-phase hexagonal wurtzite ZnO with strong c-axis orientation and improved crystallinity as the film thickness increased. Morphological and AFM studies revealed dense, uniform grains and a systematic increase in surface roughness due to grain coalescence at higher thickness. Electrical measurements showed symmetric, stable I–V characteristics with thickness-dependent leakage current, consistent with ohmic, bulk-controlled conduction dominated by thermally activated carriers. Capacitance–voltage and dielectric measurements evidenced ideal MIM-type dielectric response with clear thickness scaling, enhanced permittivity, and reduced loss tangent for thicker films. Ferroelectric-like P–V hysteresis loops, arising from defect-dipole reorientation and strain-induced local symmetry breaking associated with Mg2⁺ substitution at Zn2⁺ sites, confirmed reversible polarization switching with a systematic increase in remanent polarization and memory window from 20 to 100 nm. Endurance tests on the 50-nm device showed that the memory window decreases only from 0.52 to 0.47 V over 5000 bipolar cycles (≈ 9.6% fatigue), while retention measurements reveal a similar ~ 10% reduction of the memory window over 106 s, demonstrating slow, quasi-logarithmic polarization decay and stable charge storage over extended cycling and time. These findings identify thickness engineering as a key handle for optimizing charge storage, endurance, and retention in Mg-doped ZnO MIM capacitors, underscoring their potential for next-generation non-volatile memory devices.