THE EFFECT OF CHANGING MASS DENSITY OF IMPURITIES ADDED TO TIO2-MEH ON CURRENT AND ENERGY GAP VALUES

TiO2-MEH thin filmhas been grown onto glass substrate at room temperatureby spin coating and doped with CaSO4, CuCO3 and La2O3. The current – voltage relation for the four samples were studied. It was found that at a certain voltage the current decreases as the density increases. This may be due to the fact that the density increasing, increases resistance and decreases current. The energy gap is also shown to be affected by the density. When the impurities were added the increase of free charge carriers causes the Fermi level to move and jump from the energy gap 2.216 to 3.721 eV. Then upon increasing the mass density to be 2.69, 4.35 and 6.51 g/cm3 the energy gap decreases to be 3.721, 3.295 and 2.15 respectively. This decreasing may be related to the fact that, according to tight binding approximation, the density increases, increases the width of energy band, which in turn decreases the energy gap