Synthesis And Characterization Of AIN Nano-structures

Due to unique physicochemical properties, nano materials have been widelyused in electronics, medicine, manufacturing, aerospace, aviation, defense and otherkinds of Engineering, nanotechnology has become one of the key technologies forindustrial development in the21st Century. AlN ceramics have excellent propertiesin mechanical, thermal, optical, electrical, etc, possessing a huge potential andbright prospect for Engineering application. Therefore, AlN nano-arrays andnano-urchins structure were prepared in this thesis. We tested the mechanicalproperties of AlN nano arrays and single nano-rod, and investigated the opticalproperties of AlN nano-arrays and nano-urchins structure.In this dissertation, free-standing AlN nano-arrays and AlN nano-urchinsstructure were prepared by chemical vapor deposition method using AlCl3and NH3as source withthout the catalyst. SEM images present that free-standing AlNnano-arrays consist of nano-rod with hexagonal cross-section morphology andsectional dimension of approximately60nm or nano-cone with tip size aboutseveralnm, and AlN nano-urchins covered on silicon plates was composed of nano-rod ornano-cone radiated outward from the center. X-ray diffraction (XRD) pattern revealsthat the as-synthesized AlN nano-arrays and AlN nano-urchins structure are purewurtzite structured AlN phase. A analysis with High ResolutionTransmissionElectron Microscopy (HRTEM) for AlN nano-urchins structure shows thatradicalized nano-rod grows along the [0001] orientation of hexagonal AlN.Using the nano indentation technique, we study mechanical properties of AlNnano-arrays, and obtain force-displacement curve. With the consideration ofgeometric parameters of AlN nano-arrays and nano indenter, a test method wasdesigned, by which the mechanical properties of single AlN nano-rod can betested.The result shows that Young’s modulus and Hardness of single AlN nano-rodwith a hexagonal cross-section and section size of approximately60nm is275.23GPa and5.83GPa, respectively. Photoluminescence spectrum of free-standing AlNnano-arrays consists of a shoulder ultraviolet emission peak of~359nm (3.45eV), aweak violet emission centered at~425nm (2.92eV) and a strong green emissioncentered at~520nm (2.38eV), Photoluminescence spectrum of AlN nano-urchinsstructure has a broad spectrum of400~800nm, with a broaden center, includingvisible light region of green and yellow, and a weak shoulder violet emissioncentered at~450nm (2.76eV). Combined with X-ray photoelectron spectroscopyanalysis (XPS) data, the luminescence mechanism was analyzed.