Enhanced Conducting SiO2 Nanosheets Designed as Transparent Optical Windows رسالة ماجستير

Abstract

In this thesis, transparent conducting substrates suitable for optoelectronic devices have been fabricated. The conducting substrate is made of two stacked layers of SiO2 sandwiched with Au nanosheets of thicknesses of 50 nm, 100 nm, and 200 nm to form SiO2 / Au / SiO2 (SAS-xx) trilayers. SAS substrates are subjected to structural and optical analysis to explore the possible physical modifications that resulted from the participants of the Au layer in the structure of SiO2. It is observed that Au nanosheets didn’t alter the amorphous nature of the structure of SiO2 but enhanced its optical properties significantly. Particularly, it is observed that SAS-00 samples not comprising Au exhibit high transmittance and low reflectance. The thicker the Au layer, the lower the transmittance and the higher the reflectance. Thicker layers of Au also resulted in a decrease in the light absorption of SiO2. However, Au nanosheet enhanced the free carrier absorption in the infrared range of light and decreased the energy band gap of SiO2. SAS samples comprising no Au, Au nanosheet of a thickness of 50 nm exhibited non-degenerate semiconductor characteristics and showed the presence of energy tail states in the band gap. The tail states disappeared as the Au thickness was increased further. It is also observed that the Au nanosheet improves the dielectric constant value and dispersion. SAS-200 samples showed a high k-gate dielectric material feature with a relative dielectric constant value exceeding 40. In addition, it is observed that the Au nanosheet increased the optical conductivity and the free charge density in SiO2 films, making them highly conductive and semitransparent. Substrates with these characteristics are promising for use as high-k-gate electrodes and for the design of optoelectronic devices.