Optical properties of porous silicon thin films

Spectroellipsometrical (SE) investigations in 1.5-4.0 eV spectral range wer e one for optical characterization of porous silicon (PS) thin films. A mix ing of a crystalline silicon and amorphous silicon with voids using Effecti ve Medium Approximation [D.E. Aspnes, Phys. Rev. B 27 (1983) 985] is used t o calculated the refraction index (n) and the absorption constant (k) of th e PS layers. Measurements were done on PS obtained electrochemically on p() silicon substrates. From the dispersion spectra of the refractive index, using the Wemple DiDomenico model [S.H. Wemple, M. DiDomenico Jr., Phys. Re v. B 3 (1971) 41338], the values for optical band gap, energy oscillator an d dispersion energy for PS (model's parameters introduced by Wemple) are ev aluated. (C) 1999 Elsevier Science B.V. All rights reserved.