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FIZIKA A 11 (2002) 3 , 91-102
 
INFLUENCE OF g-IRRADIATION ON OPTICAL AND
ELECTRICAL PROPERTIES OF AMORPHOUS CuInSeTe, CuInSTe AND CuInSeS THIN FILMS
LAILA I. SOLIMAN
Solid State Physics Laboratory, National Research Centre, Cairo, Egypt
Received 15 October 2001; Revised manuscript received 23 May 2002
Accepted 17 June 2002 Online 07 February 2002
Thin films of quaternary CuInSeTe, CuInSTe and CuInSeS, of thickness 180 nm, were
deposited on glass or quartz substrates at 300 K by thermal evaporation under vacuum of
0.13 MPa (10-6 Torr) with a deposition rate of about
6 nm/s. The bulk and thin films of the samples were tested by X-ray diffraction, which
revealed that the bulk samples have a polycrystalline structure whereas the thin films are
amorphous. The X-ray fluorescence analysis as well as the chemical analysis indicates very
slight variations of the film constituents after g-irradiation.
The dependence of the absorption coefficient on photon energy showed the existence of an
indirect energy gap in all quaternary films. Moreover, these optical band gaps decreased
after increasing the g-ray doses at room temperature. The
validity of the Urbach rule was investigated and the respective parameters were estimated.
Resistivity and Hall effect measurements showed that the CuInSeTe, CuInTeS and CuInSeS
thin films are p-type semiconductors. The resistivity decreased after increasing the g-ray doses. The decrease of the values of energy gaps and the
resistivity at room temperature of the films with increased g-ray
doses are interperted in terms of the variation of the density of states model of Mott and
Davis, and explained as due to the unsaturation of bonds in amorphous solid.
PACS numbers: 68.55.-a, 73.50.-h, 78.66.Jg
UDC 538.975
Keywords: thin films of CuInSeTe, CuInSTe and CuInSeS, amorphous, g-irradiation,
optical band gaps, resistivity, Hall effect, unsaturation of bonds
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