الفهرس 
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Abstract
Bismuth telluride and its derivative selenide compounds are
extremely interesting semiconductors due to their technological importance.
The fabrication devices with alloys of these compounds, possessing
thermoelectric generators have been an important and recent technological
development. Therefore, thin films of new compounds Bi2(SexTe1-x)3 where 0
≤ x ≤ 1, has been chosen as the subject of this work.
Stoichiometric bulk ingot materials of Bi2(SexTe1-x)3 where 0 ≤ x ≤ 1
were prepared by Bridgman technique in vacuum-sealed silica tubes. X-ray
diffractometry has revealed that the prepared ingot materials with indicated
compositions are single –phase polycrystalline materials corresponding to
the rhombohedral type structure. The elemental analysis (EDAX) of the ingot
materials indicated that they are nearly stoichiometric. The lattice parameters
were determined.
Nearly stoichiometric thin films of Bi2(SexTe1-x)3 with different
compositions were deposited on either glass or KBr discs as substrates by
thermally evaporating method. The structural properties of the as-deposited
and annealed films under vacuum at 373, 423, 473K for 2 hours were studied
by X-ray diffractometry (XRD) and transmission and scanning electron
microscopy. These studies confirmed that as-deposited and annealed films at
373K with different compositions were amorphous but for annealed films at
423, 473K were polycrystalline with rhombohedral structure as that of the
bulk material with (015) predominant reflecting plane . Moreover, the grain
size, microstrain, dislocation density and the number of crystallites were
calculated.