بتول جبار عبيد

abstract

          In this research, Tin oxides (SnO2) thin films have been prepared on the glass substrates by the pulsed laser technique ,where was the use of Nd:YAG laser with wavelength (1064)nm and energy600mJ . These prepared films have been deposited with different concentration(10,20,30,40)% of magnesium oxide(MgO)at annealing temperature (RT,373K,423K) with thickness (400 nm).

The structures of SnO2 and MgO powder and thin films have been studied by X-ray diffraction technique. X-ray study shows that the structure is polycrystalline with tetragonal structure and with (110) preferred orientation plane and that the degree of crystallization decreases with increasing of doping ratio.

                                    

         The morphological study is performed by atomic force microscope (AFM).

The AFM images showed the films with uniform surface and without holes.

Optical properties were studied using the spectrometer transmittance of visible rays and ultraviolet results showed that the transmittance ranging between (70-90) % as the transmittance increased with increasing of doping ratio and temperature.

                                          

    By studying the nature and type of electronic transfer showed that all energy gap films had the directly electronic transition and energy gap increase with increasing of doping ratio and annealing temperature of (2.15-3.08) eV .

Also the optical constants such as reflective, absorption coefficient, extinction coefficient, refractive index, real and imaginary part of dielectric constant and it were found that optical constants decrease with increasing of annealing temperature and doping ratio .

     Finally, (Al / SnO2: MgO /n-Si / Al) heterojunction has been prepared at different concentration. The( I-V) characteristic of (Al / SnO2: MgO /n-Si / Al) heterojunction show that the forward current density at dark condition varies approximately exponentially with applied voltage and the junction is coinciding with recombination –tunneling modle .

     We also observed that the dark current density increased slightly with increasing MgO doping concentration. Under illumination, the photocurrent density increased with increasing MgO doping concentration .The( I-V) characteristic of (Al / SnO2: MgO /n-Si / Al) heterojunction show that the solar cell which is produced at X=40% by efficiency (η) =4.180%,fill factor(F.F)=0.682%.

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