Efect  of Heat Treatment on the Electrical Properties of  

(Bi₂S₃-PbS)   Films

S. Mahmoud  and H. Omar

National Research Center

Electron Microscope and thin films Department., Physics Division

Egypt

sihamsalim@yahoo.com

Abstract

  Presently nanocrystalline materials have opend a new version in the field of electronic applications, since material  properties could be changed by changing the composition, grain size and thickness of the films. Development of such materials, whose electrical and optical proerties could be controlled, will be useful in many ways. For example optoelectronic devices, particulary solar energy conversion devices could be modified accordingly. Bismuth sulfide - lead sulfide is one of such materials whose band energy, E_g lies in the visible solar energy spectrum and could be increased to higher energy by change in compositions and reducing film thickness and/ or grain size.

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   A group of thin (Bi₂S₃)_1-x(PbS)_x films under different ratios [0.1 ?U x ?U 0.85]  were obtained on the glass substrates by the chemical method. The films have been prepared by a modified chemical deposition process by allowing the triethanolamine complex of Bi⁺³ and Pb⁺² to react  with S^-2 ions, which are released slowly by the dissociation of thiourea  solution. The electrical resistance of the sample was measured directly by using the HL5500 PC with Keithley 617 Programmable Electrometer having an input resistance of 10¹⁶ ¦¸. The electrical resistivity was determined from sheet resistance measured by employing a four-point setup following the procedure proposed by Van der Pauw during heating and cooling of the as deposited films. Sheet resistance R_s was found to decrease with the increase of the film thickness. The activation energies of the electrical conduction in all ratios have been determined in both heating and cooling cycles

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Keywords:Thin films, (Bi₂S₃)_1-x(PbS)_x , Chemical deposition, Sheet resistance R_s , grain size

Corresponding author: Prof. Dr. Siham Mahmoud Salim

National Research Center, El behoose Str.Dokki,Giza,Egypt

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Tel: (+2010) 6180341