Structural, Thermal, Electrical, and Negative Resistance Properties of (Se_(60)Te_(40))_xTl_((100-x)) Chalcogenide Glasses

摘要

Bulk (Se_(60)Te_(40))_xTl_((100-x)) glass (x=80, 75, 70, and 60 mol.%) is prepared bythe melt quenching technique. The density of the samples is found toincrease with increasing the Tl content in the glass. Only the sample(Se60Te40)80Tl20 is confirmed to be amorphous according to XRD results,while some nanocrystals are grown and increase with increasing the Tlcontent in the glass. Average bond energy is calculated and found todecrease with increasing the Tl content. Thermal characteristics andresponses of the glass are investigated by DSC and TGA measurements. Theelectrical measurements are carried out in the temperature range 100–300 K.The direct current (dc) conductivity is discussed in the light of the variablerange hopping (VRH) model with activation energies decreasing with theincrease of the Tl content in the glass. The alternating current (ac)conductivity is discussed and fitted for the sample (Se_(60)Te_(40))_(80)Tl_(20) on thebases of the Correlated Barrier Hopping (CBH) model with N 21019cm~(-3) eV~(-1) and the τ_o≈10~(-13) s. Different types of switching modes withthreshold voltage are obtained in the range 5–17 V. Fth is found to decreasewith increasing the average bond energy, and increase with increasing thesample thickness indicating that the mechanism of switching is ofelectrothermal origin.