Tunable near-infrared epsilon-near-zero and plasmonic properties of Ag-ITO co-sputtered composite films

Figures & data

Figure 1. Surface and cross-sectional morphologies of as-deposited Ag-ITO films with different silver contents, obtained from (a)–(c): Cross-sectional SEM (insets: schematic of the distributions for Ag and ITO particles and different growth stages); (f)–(h): Surface SEM (insets: AFM images) and (d)–(e): TEM.

Notes: Films with 0.15, 0.95, and 2.74 at.% Ag were selected for analysis and labeled as sample 1(S1), sample 2(S2), and sample 3(S3), respectively (the same below). Parts of (a)–(c) and (f)–(h) are reproduced from [55].

Figure 2. XRD patterns of Ag-ITO films with different silver contents compared with pure ITO films under identical fabrication conditions (see labels for details).

Notes: The patterns for sample 1–3 and ITO are depicted in black, red, blue, and purple curves, respectively. The peak positions of In₂O₃ are represented as circles (●).

Figure 3. Wide range of λ _c and ENZ tuning can be achieved by optimizing the silver content and post-annealing parameters: (a) Real permittivity for Ag-ITO films (inset: real permittivity for pure ITO films); (b) Imaginary permittivity; (c) Hall measurements for the annealed films (inset: as-deposited films); (d) Experimental data and linear fitting of λ _c vs. square root of carrier concentration.

Notes: Parts of (a) and (b) are reproduced with permission from [55].

Figure 4. ENZ region for Ag-ITO films with different silver contents: (a) Experimental data of as-deposited Ag-ITO films; (b) Experimental data of annealed Ag-ITO films; (c) Effective medium approximation based on extended Maxwell-Garnett model which takes silver and ITO as constituents and air as host.

Notes: Data for pure ITO films without Ag are also plotted in (a) and (c) for comparisons. In (b) the pure ITO curves are outside the wavelength range and not displayed.

Figure 5. Reflectance curves for annealed Ag-ITO films vs. incident angle at the wavelength of 1550 nm: (a) Schematic of the prism-coupling configuration; (b)–(d) Experimental results by prism-coupling; and simulation by transfer-matrix method for sample 1, 2, and 3, respectively.

Chen C , Ye H . Fabrication and optimization of ITO-Ag co-sputtered nanocomposite films as plasmonic materials in the near-infrared region. Proc of SPIE. 2017;10112:101121I. DOI:10.1117/12.2251255

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