Optical Characterization of AsxTe100-xFilms Grown by Plasma Deposition Based on the Advanced Optimizing Envelope Method

Three As(x)Te(100-x)films with different x and dissimilar average thicknessd over bar are characterized mainly from one interference transmittance spectrumT(lambda= 300 to 3000 nm) of such film on a substrate based on the advanced optimizing envelope method (AOEM). A simple dual transformation ofT(lambda) is proposed and used for increasing the accuracy of computation of its envelopesT(+)(lambda) andT(-)(lambda) accounting for the significant glass substrate absorption especially for lambda> 2500 nm. The refractive indexn(lambda) of As(40)Te(60)and As(98)Te(2)films is determined with a relative error <0.30%. As far as we know, the As(80)Te(20)film is the only one with anomalous dispersion and the thickest, with estimatedd over bar = 1.1446 nm, ever characterized by an envelope method. It is also shown and explained why the extinction coefficientk(lambda) of any of the three As(x)Te(100-x)films is computed more accurately from the quantityT(i)(lambda) = [T+(lambda)T-(lambda)](0.5)compared to its commonly employed computation fromT(+)(lambda). The obtained results strengthen our conviction that the AOEM has a capacity for providing most accurate optical characterization of almost every dielectric or semiconductor film withd over bar > 300 nm on a substrate, compared to all the other methods for characterization of such films only fromT(lambda).