Formation and Characterization of (MoO3/ ZnS,InSe) Heterojunctions رسالة ماجستير

Abstract

In this thesis we have explored the structural, optical, dielectric and electrical properties of the MoO3/(ZnS, InSe) interfaces by means of X-ray diffraction, UV visible light spectroscopy and current-voltage characteristics techniques. The MoO3/(ZnS,InSe) interfaces which are prepared by the thermal evaporation technique under vaccum pressure of 10-5 mbar are observed to exhibit amorphous nature of growth. Optically, while the MoO3/ZnS exhibit conduction and valance band offsets of 2.8 and 2.65 eV, respectively, the MoO3/InSe revealed energy band offsets of 2.15, 0.75 eV, respectively. The obtained ΔEc and ΔEv values nominate the interfaces for optoelectronic applications including thin film transistor technology. To verify the applicability of these systems in optoelectronic technology, the dielectric dispersion spectrum for the MoO3/ZnS are studied and modeled in Drude-Lorentz approach for optical conduction. The study indicates that the formation of this heterojunctions enhances the drift mobility of the charge carriers to 13.1 cm2/V.s and make the Plasmon frequency range narrower. On the other hand, the Drude-Lorentz modeling for MoO3/InSe interfaces have shown that the drift mobilities for this interface could be improved more and a value of 48.7 cm2/V.s is obtained. As indicated from the electrical measurments, the MoO3/ZnS system electrically fails to behave as thin film transistors. On the other hand, The MoO3/InSe heterojunction which was electrically investigated revealed characteristics of back to back schottky devices. The analysis of the current-voltage characteristics of this device has shown that the current is dominated by thermal excitations accompanied with charge particle tunneling through barrier height of viii ~0.7 𝑒𝑉. The device also displayed resonant tunneling diode characteristics during reverse biasing conditions. The MoO3/InSe device appear to be promising for optoelectronic applications.