Silicon nanowires for network photodetectors and plasmonic applications

Mülazımoğlu, Emre
Being the key component of the semiconductor industry, silicon in nanowire form has gained increased attention. In this thesis, vertical arrays of silicon nanowires (Si NWs) have been fabricated with metal assisted etching method (MAE). MAE method is a simple, solution based and low temperature process. In this method, fabricated nanowires inherit the starting wafer characteristics, such as doping type, density and crystal orientation. In the first part, fabricated NWs in network form have been demonstrated as the active layer in metal-semiconductor-metal photodetectors. Devices showed partial transparency and fully reversible switching behavior. Moreover, fast dynamic response has been obtained with 0.43 milliseconds for the rise time and 0.58 milliseconds for the fall time. Flexible PDs were fabricated on polyethylene-terephtalate substrates and operational during bending up to a radius of 1 cm. In the second part, surface plasmon resonance properties of the silver (Ag) nanoparticle decorated Si NWs have been investigated. Si NWs were fabricated through one-step and two-step MAE method. Two-step MAE method involved the use of hydrogen peroxide. Ag nanoparticles were decorated onto Si NWs through simple evaporation and annealing processes. The hydrogen peroxide in MAE method was found to degenerate the surface of nanowires and created oxygen defects. Defects enhanced infrared absorption at higher frequencies and led to emission of light by radiative recombination. Almost 50-fold enhanced localized-surface-plasmon-resonance (LSPR) was obtained. It was attributed to the change in the dielectric constant of effective medium. LSPR wavelength could be tuned by changing Ag particle size and NW length.


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Citation Formats
E. Mülazımoğlu, “Silicon nanowires for network photodetectors and plasmonic applications,” M.S. - Master of Science, Middle East Technical University, 2013.