Share
خصائص اغشية (SnO2) 1 - x (ZnO) x النانوية التركيب الرقيقة وتطبيقاتها == Characterizations of Nanostructure (SnO2)1 - x(ZnO)x Thin Films and Their Applications
Author name:
زهراء عادل جواد المعموري
Supervisor name:
ناهدة بخيت حسن
General topic:
Physics
Specific topic:
Physics
Degree:
Doctorate
University:
University of Babylon - College Of Science - Physics Department
Language:
English
University location:
Babylon
First pages:
26T1640 - p.pdf
Abstract:
In this work, mixed (SnO2)1 - x(ZnO)x thin films were prepared by using ahomemade chemical spray pyrolysis technique, which was a simple, inexpensive and suitable technique for large deposition area. The Tin (II) Chloride Dihydrate SnCl2.2H2O was used as a source of tin oxide particles, and the zinc acetate dehydrate Zn(CH3COO)2.2H2O was used as a source of zinc particles. Mixed (SnO2)1 - x(ZnO)x thin films with different Vol.% of (x) [0,0.2,0.4,0.6,0.8,1] has been prepared on clean preheated glass and silicon substrate at 400 ºC with atmospheric air as the carrier gas. The crystal structures were examined by X - ray diffraction analysis. The result showed that all the prepared films were polycrystalline structure. It was observed that the granular size of the SnO2 membrane was greater than the granular size of ZnO the membrane, indicating that the ZnO membrane in the selected conditions was better crystallized. The surface morphology of the deposits films have been studied by using atomic force microscope (AFM), scanning electron microscope (SEM) and energy dispersive X - ray (EDX). The grain size of the (SnO2) nanoparticles observed at the surface depended on (x), which increase with increasing of ZnO Vol.%, also the increasing ZnO Vol.% lead to an increase in the surface roughness. (EDX) shows that all the films contain the elements (Sn, Zn and O) as expected, indicating formation of the (SnO2)1 - x(ZnO)x films with high purity. The optical properties of the films, which were prepared with thickness of (190 ± 3 nm), have been determined by using the optical transmittance measurements in the spectral region from 300 to 1100 nm. Transmittance results were upper than 95% which make these films suitable for sensor applications. Direct energy gap for (SnO2) equal 3.1 eV, it increases with increasing ZnO Vol.%. The optical constants such as refractive index, extinction coefficient and dielectric constant have been calculated for the prepared films. The electrical properties included D.C conductivity and Hall effect were studied. The results showed that the prepared films were n - type, and have two activation energies (Ea1 , Ea2). It was found that the electrical D.C conductivity increased with the increase of the ZnO Vol.%. The reverse bias capacitance for (SnO2)1 - x(ZnO)x/p - Si heterojunction was measured as a function of bias voltage at frequency 1MHz, and it was indicated that these heterojunction were abrupt. The capacitance increases with increasing the reverse bias voltage, also the capacitance increases from 185 pF to 314 pF with increase of the (x), while the depletion width decreasing with increasing (x). The value of built - in potential decreases from 0.9 to 0.3 Volt with increasing of the ZnO Vol.%. The electrical characteristics of the (SnO2)1 - x(ZnO)x/p - Si heterojunction have been studied, where current - voltage characterization under dark conditions showed that forward bias current variation approximately exponentially with voltage bias. This conforms with tunneling - recombination model, and reverse bias showed little stop and soft breakdown voltage. Also the product showed that current decreases with increasing Vol.% of (x). The efficiency and the fill factor of (SnO2)1 - x(ZnO)x/ p - Si of solar cell was measured. The calculations of the solar cell show that efficiency was the highest value when mixing where we observed a clear increase in efficiency ranging from (1.87 - 5). The fill factors of the devices for all types were in range of (0.25 - 0.454). The results showed that the efficiency of the solar cell is higher than its value at x = 0.8.From the sensing properties measurements of thin films for gas ( NO2 ) show that the films was good sensor to this gas at (25 - 200)oC. The best sensitivity of mixed thin films was 81% at x=1. The variation of the operating temperature of the films have led to a significant change in the sensitivity of the sensor with an ideal operating temperature.
