Nanoscopic Investigation of Surface Morphology of Neural Growth Cones and Indium Containing Group-III Nitrides

• Main Author: Durkaya, Göksel
• Format: Others
• Published: Digital Archive @ GSU 2009
• Subjects: InN; InGaN; Filopodium; Growth cone; Neuron; Atomic force microscopy; Astrophysics and Astronomy; Physics
• Online Access: http://digitalarchive.gsu.edu/phy_astr_diss/43; http://digitalarchive.gsu.edu/cgi/viewcontent.cgi?article=1042&context=phy_astr_diss

This research focuses on the nanoscopic investigation of the three-dimensional surface morphology of the neural growth cones from the snail Helisoma trivolvis, and InN and InGaN semiconductor material systems using Atomic Force Microscopy (AFM). In the analysis of the growth cones, the results obtained from AFM experiments have been used to construct a 3D architecture model for filopodia. The filopodia from B5 and B19 neurons have exhibited different tapering mechanisms. The volumetric analysis has been used to estimate free Ca2+ concentration in the filopodium. The Phase Contrast Microscopy (PCM) images of the growth cones have been corrected to thickness provided by AFM in order to analyze the spatial refractive index variations in the growth cone. AFM experiments have been carried out on InN and InGaN epilayers. Ternary InGaN alloys are promising for device applications tunable from ultraviolet (Eg[GaN]=3.4 eV) to near-infrared (Eg [InN]=0.7 eV). The real-time optical characteristics and ex-situ material properties of InGaN epilayers have been analyzed and compared to the surface morphological properties in order to investigate the relation between the growth conditions and overall physical properties. The effects of composition, group V/III molar ratio and temperature on the InGaN material characteristics have been studied and the growth of high quality indium-rich InGaN epilayers are demonstrated.