Substrate dependence on the optical properties of Al2O3 films grown by atomic layer deposition

The atomic layer deposition technique has been applied to the growth of ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ thin films on the substrates of Si(100), 100-nm-thick ${\mathrm{SiO}}_{\mathrm{2}}$ covered Si(100) $[{\mathrm{SiO}}_{\mathrm{2}}\mathrm{/Si(100)}\mathrm{],}$ and 90-nm-thick TiN covered ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/Si(100)}.$ The growth rate of ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ films was 0.19 nm/cycle and identical for all substrates employed under the surface controlled process. However, the optical properties of ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ films were significantly affected by different substrates. The average interband-oscillator energy and refractive index parameter were determined to be 3.330 eV and ${\text{2.992×10}}^{\text{−14}}\hspace{0.17em}{\mathrm{eV\hspace{0.17em}m}}^{\mathrm{2}}$ for ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ film grown on Si(100), while those for the film grown on ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/Si(100)}$ were 4.492 eV and $\text{2.074}$ ${\text{×10}}^{\text{−14}}\hspace{0.17em}{\mathrm{eV\hspace{0.17em}m}}^{\mathrm{2}},$ respectively.