Abstract
Low dimensional oxide/nitride nanocrystals were synthesized by thermal chemical vapor deposition, e.g. gallium, titanium, nitrogen atoms doped into the nanocrystals in this study. Four particular optoelectronic nanomaterials were studied, they are: Ga-doped ZnO nanowires fabricated by two-step co-evaporation methods; ZnO nanowires implanted with Ti ions by using a vapor vacuum arc (MEVVA) ion implanter; N-doped β-Ga2O3 nanowires synthesized via nitrogen plasma and nitrogen mixed method, and zigzag Ga2O3/GaN fabricated by controlling a switch (on/off = 10 min per each) of ammonia (NH3) gas process. Transformation of microstructure before and after doping, promoting electronic property, and modulation of optical property were then investigated. The self-aligned high density Ga-doped ZnO nanowires can be applied in electron field emission properties by using a two-step co-evaporation method to obtain a turn-on field of 3.4 V/um at a current density of 10 μA/cm2, a threshold field of 5.4 V/um at a current density of 1 mA/cm2, and a field-enhancement factor β of 5945 which is far better than the metallic emitter. The optoelectronic performance from the Ti-doped ZnO nanowires showed that the cathodoluminescence (CL) spectra display a blue-shift in the spectrum with increasing the dopant (Ti) concentration. Furthermore, the energy of the bandgap increases with the electron carrier density increase via the effect of Burstein-Moss. In addition, the electrical transport properties of a single Ti-doped ZnO nanowire were evaluated in a four-probe FE-SEM system and found that the resistivity decreases with increasing Ti content. More importantly the conductance of the Ti-doped ZnO nanowires was made to be dropped significantly with the increasing of mechanical bending, that is to exhibit a piezoelectronic character. The relevant electron concentration, resistivity, and electron mobility of a single Ti-doped ZnO nanowire are respectively 2.7 × 10 18 cm-3, 84.1 Ω cm, and 2.75 × 10-2 cm2V-1s-1 with the M-S-M model. The β-Ga2O3 nanowires can be doped with nitrogen atoms effectively by nitrogen plasma treatment and controlling a switch of (NH3) gas process to observe the modulation of light emission via CL measurement at low temperature. The defects like vacancies could result in a shift of the bandgap at the CL spectra with increasing the nitrogen dopant, thereby affecting the variation of the modulation of the excitation characteristics significantly. Finally, the design pattern for nanowires in the devices have been successfully fabricated, for instance, the p-n nanowire junctions and nitric oxide gas sensors to accommodate the low dimensional oxide/nitride nanocrystals on the development and application of semiconductor industry in the future.