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INVESTIGATION OF NbNx THIN FILMS AND NANOPARTICLES GROWN BY PULSED LASER DEPOSITION AND THERMAL DIFFUSION Ashraf Hassan F arha Old Dominion University, 2013 Director: Dr. Hani Elsayed-Ali Niobium nitride films (NbNx) were grown on Nb and Si (100) substrates using pulsed laser deposition (PLD), laser heating, and thermal diffusion methods. Niobium nitride films were deposited on Nb substrates using PLD with a Q-switched Nd: YAG laser (X = 1064 nm, 40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, different nitrogen background pressures and deposition temperatures. The effect of changing PLD parameters for films done by PLD was studied. The seen observations establish guidelines for adjusting the laser parameters to achieve the desired morphology and phase o f the grown NbNx films. When the fabrication parameters are fixed, except for laser fluence, surface roughness, deposition rate, nitrogen content, and grain size increases with increasing laser fluence. Increasing nitrogen background pressure leads to change in the phase structure of the NbNx films from mixed -Nb2N and cubic 5-NbN phases to single hexagonal PNb2N. A change in substrate temperature led to a pronounced change in the preferred orientation o f the crystal structure, the phase transformation, surface roughness, and composition o f the films. The structural, electronic, and nanomechanical properties o f niobium nitride PLD deposited at different nitrogen pressures (26.7-66.7 Pa) on Si(100) were investigated. The NbNx films exhibited a cubic 8-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The highly-textured 8 -NbN films have a Tc up to 15.07 K. The film was deposited at a nitrogen background pressure o f 66.7 Pa exhibited improved superconducting properties and showed higher hardness values as compared to films deposited at lower nitrogen pressures. NbN nanoclusters that were deposited on carbon coated Cu-grids using PLD at laser fluence o f 8 J/cm2 were observed. Niobium nitride is prepared by heating o f Nb sample in a reactive nitrogen atmosphere (133 Pa) at a temperature o f 900 °C. The results suggest that the niobium nitride was crystalline in the single phase o f hexagonal /?-Nb2N. As heating time increased, film growth continued with improvement in hardness and modulus. The XRD o f samples prepared by a thermal diffusion method at low nitrogen pressure and high temperatures were reported. The samples were prepared at temperatures ranging from 1250-1500 °C. 2D-XRD images of samples, processed at temperature range from 1250 -1500 °C at pressure o f 1.3x1 O'3 Pa, showed the formation of an a phase. As pressure increased to 0.13 Pa, an a-NbN phase mixed with P-Nb2N phase appeared. Niobium nitride samples were prepared by laser nitridation using a Q-switched Nd: YAG nanosecond laser and Ti: sapphire femtosecond lasers. The effects o f laser fluence on the formed phase, surface morphology, and electronic properties o f the NbNx were investigated. Samples were prepared using Nd: YAG laser are o f NbNx in the cubic 8-NbN phase. The femtosecond laser-nitrided samples were prepared by different laser fluences o f 0.1-1.3 mJ/cm2 at 4.0><104 Pa nitrogen pressure. NbNx samples with mixeda, (3 and 8 phases were observed. The cubic 8-NbN structure is dominated over the other

Investigation of NbNx Thin Films and Nanoparticles Grown by Pulsed Laser Deposition and Thermal Diffusion

Investigation of NbN_x Thin Films and Nanoparticles Grown by Pulsed Laser Deposition and Thermal Diffusion