M 2000

High-quality single crystals of Sr₃(Ir_1−xMn_x)₂O₇ with x = 0, 0.09, 0.18, 0.36 were grown using a halide flux growth technique. Details of the single crystal growth were described in Ref. 22. We measured near-normal incidence reflectivity spectra R(ω) in the energy region between 5 meV and 1 eV using Fourier transform infrared spectrometer (Vertex 70v, Bruker). We employed in-situ gold overcoating technique to obtain accurate reflectivity data^{48 (link)}. Complex optical constants in the energy region between 0.74 and 5 eV were obtained using spectroscopic ellipsometer (M-2000, J. A. Woollam Co.). Optical conductivity was calculated from the R(ω) data through Kramers-Kronig transformation.

The refractive index and extinction coefficient were measured using a multiple-angle spectroscopic ellipsometer (J.A. Woollam Co. M-2000). The thickness of the Sb₂Te₃ thin film was determined through fitting the data from ellipsometer measurements. The thickness of the surface layer was 1.5 nm, and the thickness remains constant when the total thickness of the thin film increases. The reflection spectroscopy was measured using an ultraviolet–visible spectrophotometer.

Ellipsometry was employed to determine the film thickness and the refractive index modulation vs. photo-stimulation, similarly to a recent paper on a related system [17 (link)]. Measurements were performed in a darkened room at 60°, 65°, and 70° angles of incidence, using a rotating compensator instrument (M-2000, J.A. Woollam Co. Inc., Lincoln, NE, USA) equipped with a 75 W Xe lamp. The measurements covered the 245–1700 nm spectral interval. The spot size on the sample was approximately a few mm². Each sample was measured first in its open-ring form using a UV filter to prevent conversion during the procedure; the sample was then converted into closed-ring form with an UV LED at 325 nm (power density of $150\mathsf{\mu }\mathrm{W}/{\mathrm{cm}}^2$ for 10–15 min) and measured again. Dynamic measurements were collected in real-time during the conversion from the uncolored to the colored form. The data analysis exploited the manufacturer software (VASE, Lincoln, NE, USA). In this paper Ψ and Δ data have been fitted in the 800 nm < λ < 1700 nm range where both colored and uncolored forms are transparent. Cauchy and Sellmeier models were used for the wavelength dependence of the refractive index. In this spectral region, both models provide the same results.

The mode intensity profiles and effective refractive indices for the studied multilayered structures were calculated using the “1-D Waveguided Mode Solver for Dielectric Multilayer Slab Waveguides”⁵⁶ . The confinement factors were calculated as the ratio of an optical field energy confined within a specific layer to the total mode energy. The experimental values of refractive indices were obtained using a rotating-compensator ellipsometer with a diode detector array and a xenon light source (J.A. Woollam Co. M-2000).

Spectroscopic Ellipsometry measurements were performed using a rotating compensator instrument (M-2000, J.A. Woollam Co., Lincoln, NE, USA, 245–1700 nm) equipped with a 75 W Xe lamp. Spectra have been collected in situ using a commercial liquid cell (J.A. Woollam Co., 0.5 mL).
To emphasize the contribution of the ultrathin organic layer, we analyzed difference spectra, which were obtained as the difference between the spectra acquired after the film deposition and the spectra measured on the substrate just prior to molecular deposition [40 (link),47 (link),49 (link)].

To investigate the electrical transport properties, we used a physical property measurement system (Quantum Design Inc.). We used the four-point probe method, which is the most common method for measuring the resistivity³⁵ . We deposited evenly spaced Pt contacts on the middle of the film surface. We applied a small constant current through the outer two contacts and measured the voltage between the inner two contacts. We swept the temperature in the range of 10–400 K. We measured the reflectance, R(ω), spectra in a photon energy range of 0.1–1 eV via a Fourier transform-type infrared spectrometer (model VERTEX 70 v; Bruker). We employed an in situ gold overcoating technique to obtain an accurate absolute value of R(ω). We obtained the optical conductivity of the VO₂ film via a two-layer model fit of the measured R(ω) with Drude-Lorentz oscillators^{23 ,36 (link)}. We used spectroscopic ellipsometers (models V-VASE and M-2000; J. A. Woollam Co.) to obtain the complex dielectric constants, $ϵ\left(\omega \right)={ϵ}_1\left(\omega \right)+i{ϵ}_2\left(\omega \right)$ , in the energy region between 1 and 5 eV. The optical conductivity, σ₁(ω), in this energy range can be calculated by ${\sigma }_1\left(\omega \right)={ϵ}_0\omega {ϵ}_2\left(\omega \right)$ ²³ , where ${ϵ}_0$ is the vacuum permittivity.