M. M. Wakkad

Optical properties of Bi2Te2Se thin films

Some optical parameters of Bi2Te2Se thin films, determined from the measured absorbance and transmittance at normal incidence in the visible spectral range, were studied as functions of film thickness and annealing temperature. These parameters were found to be sensitive to both film thickness and microstructure change caused by annealing in a film. The effect of thickness and temperature of annealing on the optical gap was interpreted in terms of elimination of defects and change of disordering in the amorphous matrix.

Electrical properties of antimony telluride

AbstractWe investigate the effects of the ambient temperature (T), both temperature (Ta)and time (ta)of annealing on the electrical conductivity (σ), and the Seebeck coefficient (S) of Sb2Te3. We concluded that both holes and electrons can participate to the conduction process. The material behaves as a semimetal. Although the Seebeck coefficient possesses a plus sign, the coefficient of S vs.

THERMAL PROPERTIES OF SOME COMPOSITIONS IN THE CHALCOGENIDE SYSTEM Sb40Te60-xSex

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Sb-doping effects on optical and electrical parameters of SnO2 films

plots was negative as a degenerate semiconductor. The decrease in value of S with increasing tawas attributed to a corresponding decrease in the amount of positional disorder which acts as an electron trap center.

Annealing and thickness effects on some electrical and optical properties of Sb:SnO2 films

Chalcogenide glasses with composition Ge20Se80−xTlx (x=10, 15, 20, 25, 35%) have been prepared by the usual melt-quenching technique. Thin films of the mentioned compositions have been prepared by the electron beam evaporation. In addition, another set taken from the composition ofX=30 at % with different thicknesses (d=14.7, 30.0, 56.5, 70.0, 101.0, 180.0 nm) have been taken into consideration. The X-ray diffraction (XRD) analysis revealed the amorphous nature of the prepared films. It was found that, in contrast to the optical gap (Eop), both the extent of the band tailing (B), and the band gap (Ee) increase with increasing thallium content. In other side,Eop showed thickness independency. The refractive index (n) showed obvious dependence on both composition and thickness also on the energy of the incident radiation.

SEEBECK COEFFICIENT AND ELECTRICAL RESISTIVITY OF BI2TESE2 AND BI2TE2SE ALLOYS

The thermal diffusivities, specific heats and thermal conductivities of the binary compositions Sb40Te60 and Sb40Se60 and the ternary composition Sb40Te30Se30 were measured in the range ∼320 to 500 K. It was found that the environmental temperature, the content of Se in the composition and the conditions of measurements are decisive factors greatly influencing both the values and the behaviour ot the thermal parameters, and the mechanisms of thermal transport. Although the tested compositions exhibit semiconducting behaviour, the free charge carrier component of the thermal conductivity was so small as to be negligible. Thus, it could be concluded that the observed thermal conductivity is attributable to both photon and phonon mechanisms.ZusammenfassungIm Temperaturbereich 320–500 K wurde das Temperaturleitvermögen, die spezifische Wärme und die Wärmeleitfähigkeit der binären Kompositionen Sb40Te60 bzw. Sb40Se60 und der ternären Komposition Sb40Te30Se30 untersucht. Man fand, daß die Umgebungstemperatur, der Se-Gehalt der Kompositionen und die Meßbedingungen entscheidende Faktoren sind, welche sowohl Wert als auch Verhalten der thermischen Parameter, weiterhin den Mechanismus des Wärmetransportes beeinflussen. Obwohl die untersuchten Kompositionen Halbleiterverhalten zeigten, war die freie Ladungsträgerkomponente der Wärmeleitfähigkeit so gering, daß sie vernachlässigt werden konnte. Somit konnte darauf geschlossen werden, daß die beobachtete Wärmeleitfähigkeit sowohl Photonen- als auch Phononenmechanismen zugeschrieben werden kann.

Optical properties of Bi 2 Te 2 Se thin films

The electrical resistivity, π, and Seebeck coefficient,S, of the system Sb2Se3 were measured in the ambient temperature range 323≤T≤573 K. Both parameters were found to be affected considerably by the temperature of annealing,Ta, in the range 493≤Ta≤653 K and by the time of annealing,ta, for periods extending to 16h. Additionally, both depended strongly on the ambient temperature.The activation energy of ordering of the present system could be calculated by using the effects of isothermal annealing on the considered physical parameters.ZusammenfassungIn einem Umgebungstemperaturbereich von 323 bis 573 K wurden der elektrische Widerstand π und der Seebocksche KoeffizientS des Systemes Sb2Se3 untersucht. Für beide Größen wurde eine starke Abhängigkeitvon der TempertemperaturTa im Bereich 493≤Ta≤653°C und von der Temperdauerta bis zu 16 Stunden beobachtet. Zusätzlich sind beide auch stark abhängig von der Umgebungstemperatur.Unter Ausnutzung der Auswirkung des isothermen Temperns auf die fraglichen physikalischen Größen konnte die Aktivierungsenergie der Konditionierung berechnet werden.