A new method (named as DASF: Derivation of absorption spectrum fitting) is proposed for the determination of optical band gap and the nature of optical transitions in semiconductors; this method only requires the measurement of the absorbance spectrum of the sample, avoiding any needs to film thickness or any other parameters. In this approach, starting from absorption spectrum fitting (ASF) procedure and by the first derivation of the absorbance spectrum, the optical band gap and then the type of optical transition can be determined without any presumption about the nature of transition. DASF method was employed on (60−x)V2O5–40TeO2–xAg2O glassy systems (hereafter named as TVAgx), in order to confirm the validity of this new method. For the present glasses, the DASF results were compared with the results of ASF procedure for, confirming a very good agreement between these approaches. These glasses were prepared by using the melt quenching and blowing methods to obtain bulk and film samples, respectively. Results show that the optical band gap variation for TVAgx glasses can be divided into two regions, 0 ≤ x ≤ 20 and 20 ≤ x ≤ 40 mol%. The optical band gap has a maximum value equal to 2.72 eV for x = 40 and the minimum value equal to 2.19 eV for x = 40. Also, some physical quantities such as the width of the band tails (Urbach energy), glass density, molar volume, and optical basicity were reported for the under studied glasses.

A new method for the determination of optical band gap and the nature of optical transitions in semiconductors

Glasses with compositions (60−x) V2O5–40TeO2–xSb2O3 with 0 ⩽ x ⩽ 10 (in mol%) have been prepared using usual melt quenching method. The position of the absorption edge and hence the values of the optical band gap was found to depend on the glass composition. Using the Tauc model, the absorption spectrum fitting method (ASF) was employed to obtain the optical band gap. This method requires only the measurement of the absorbance spectrum of the sample. For each sample, the width of the band tail was determined. Also, the density and glass transition temperature values indicate that the rigidity and packing of the samples increase with increase in Sb2O3 concentration.

Band gap determination by absorption spectrum fitting method (ASF) and structural properties of different compositions of (60−x) V2O5–40TeO2–xSb2O3 glasses

Optical band gap, glass transition temperature and structural studies of (100 − 2x)TeO2–xAg2O–xWO3 glass system

Physical and structural properties of some bismuth borate glasses

Thermal characteristics, raman spectra and structural properties of new tellurite glasses within the Bi2O3-TiO2-TeO2 system

The non-linear optical performance and structure of TeO 2 –Nb 2 O 5 –ZnO glasses was investigated as a function of ZnO content. The third-order non-linear optical susceptibility ( χ (3) ) as measured by a Degenerate Four Wave Mixing (DFWM) method, initially increased with increasing ZnO content to about 8.2 × 10 −13 esu for a glass containing 2.5 wt% ZnO, and then decreased to 5.9 × 10 −13 esu as the ZnO content increased to 10 wt%. There was no noticeable change as the ZnO content increased from 10 to 15 wt%. The non-linear optical response time, which caused electron cloud deformation, was from 450 to 500 fs. The structure of these glasses as analyzed by Raman spectroscopy and FT-IR spectra, was affected by the addition of ZnO up to 5 wt%, when, it is believed, the Zn 2+ ions occupied the interstitial positions in the glass network by replacing the Nb 5+ ions. The replaced Nb 5+ ions occupied the network forming positions as the Te 4+ ions. Increasing ZnO > 5 wt% did not have any further effect on the glass structure.

Zhengrong Sun

Papers

Structure and non-linear optical performance of TeO2–Nb2O5–ZnO glasses