Study of the composition, structure, and optical properties of $a$-Si$_{1-x}$C$_x$ : H$\langle$Er$\rangle$ films erbium doped from the Er(pd)$_3$ complex compound

Rutherford backscattering, IR spectroscopy, ellipsometry, and atomic-force microscopy are used to perform an integrated study of the composition, structure and optical properties of $a$-Si$_{1-x}$C$_x$ : H$\langle$Er$\rangle$ amorphous films. The technique employed to obtain the $a$-Si$_{1-x}$C$_x$ : H$\langle$Er$\rangle$ amorphous films includes the high-frequency decomposition of a mixture of gases, (SiH$_4$)$_a$ + (CH$_4$)$_b$, and the simultaneous thermal evaporation of a complex compound, Er(pd)$_3$. It is demonstrated that raising the amount of CH$_4$ in the gas mixture results in an increase in the carbon content of the films under study and an increase in the optical gap $E^{\mathrm{opt}}_g$ from 1.75 to 2.2 eV. Changes in the composition of $a$-Si$_{1-x}$C$_x$ : H$\langle$Er$\rangle$ amorphous films, accompanied, in turn, by changes in the optical constants, are observed in the IR spectra. The ellipsometric spectra obtained are analyzed in terms of multiple-parameter models. The conclusion is made on the basis of this analysis that the experimental and calculated spectra coincide well when variation in the composition of the amorphous films with that of the gas mixture is taken into account. The existence of a thin (6–8 nm) silicon-oxide layer on the surface of the films under study and the validity of using the double-layer model in ellipsometric calculations is confirmed by the results of structural analyses by atomic-force microscopy.