Investigation of thermal, electric and optic properties of composite semiconductors

ABSTRACT Master Thesis INVESTIGATION OF THERMAL, ELECTRIC AND OPTIC PROPERTIES OF COMPOSITE SEMICONDUCTORS Canan AKSU CANBAY Fırat University Graduate School of Natural and Applied Sciences Department of Physics 2005, Page: 54 With the developing technology, the semiconductor composites are used in making solar cell, optoelectronic device elements, laser diodes and light emitting diodes (LED) because of having properties such as possesing different transitions, high thermal conductivity, low thermal extending coefficient, good ionic conductivity, sensitivity against the light and endurance against the heat. Besides this, the composites obtained from the transition metal oxides are started to use as humidity and gas sensors. By these properties, composites have became more important conditions due to high heat endurance, thermal stability and being economic in production stage. In this study, thermal, electrical and optical properties of semiconductor composites, which were obtained from ZnO, CuO and NiO transition metal oxides were investigated. The corruption begining temperatures of the samples and the weight losses related to these temperatures were found by making thermogravimetric analysis of the samples with TG/DTA. The surfaces of samples were investigated by scanning electron microscopy (SEM). The electrical conductivity-temperature measurements of the unheated(Z 1 -Z4) and calcined samples(ZZl-ZZ4), which were shaped like a disk, were made. Thermal cycle was applied to Z1-Z4 samples and the activation energy for each cycle was calculated. By the help of a =0"0exp(-AE/kT) equation, the activation energies of the unheated samples were found as Zl( Ea=0.45 eV Ea=0.47 eV, Ea=0.53 eV, Ea=0.52 eV ), Z2(Ea=0.42 eV, Ea=0.46 eV, Ea=0.50 eV, Ea=0.48 eV ), Z3(Ea=0.47 eV, Ea=0.45 eV, Ea=0.43 eV, Ea=0.42 eV ) ve Z4(Ea=0.44 eV, Ea=0.36 eV, Ea=0.44 eV, Ea=0.46 eV). The activation energies of the calcined samples were found as ZZ1( Ea=0.27 eV), ZZ2(Ea=0.24 eV), ZZ3(Ea=0.20 eV) ve ZZ4(En=0.21 eV).The absorbtion spectra of the samples were taken by UV+VIS spectrometer and then the forbidden band gaps were found as Zl [1.58 eV], Z2 [1.68 eV], Z3 [2.5 eV], Z4 [1.64eV]. Keywords: Composite, Transition metal oxides. Activation energy. Semiconductor. VII