The Optical, Electrical, Thermal Properties Studies Of Ga-Assisted Growth One-Dimensional Nanostructures

Ga-assisted growth one-dimensional nanostructures, with many excellent physical and mechanical characteristics, have many potential application in the micro-nano technology. Ga-catalytic silicon nanostructures can be connect and match with other devices under the good performance, which opens a new field for the high-integrated intelligent devices. Meanwhile, nanothermometer and nanoswitch of Ga-filled nanotubes provide a new technology for the development of mechanical and electrical devices. Based on the above, we have studied the optical, electrical, thermal properties and new applications for the gallium-assisted growth one-dimensional nanostructures, and performed a series of innovative results, which as follows.(1) A simple one-step, controllable and large-area fabrication technique of silicon based multi-level branched nanostructures have been rationally designed. Using the gallium catalytic activity innovatively, ordered arrays of silicon multi-branch nanostructures were synthesized. We gave more analysis about the growth mechanism of multi-level branched nanostructures.(2) In comparing with the first-order optical phonon peak of crystalline silicon, the room-temperature Raman frequency of branched nanostructures, big branched nanostructures and branched nanowires are blue-shifted and its full width at half maximum broadens. The typical room-temperature PL spectra showed, for the three samples, a moderately strong photoluminescence emission was at 550 nm. Compared with the previous studies, three emission bands have blue-shifted, which may be the effect of quantum confinement and/or the defects, such as stacking faults.(3) The ordered arrays of crystallized silicon multi-branch nanostructure on the field electron emission and electric transport properties is excellent. A decent field electron emission with relatively low turn-on field of 3.16 V/μm and high field-enhancement factor of 1252 was received for the silicon nanobranches. In addition, electrical transport measurements revealed a small electrical resistance. In contrast, by improving silicon nanobranches - electrode contact, vacuum annealing dramatically reduced electrical resistance approachly 2-fold, while thermal oxidation resulted in much high resistance due to amorphous oxide coating of silicon nanobranches, both of current versus voltage curves become more linear and symmetrical, the transport stability is obviously improved.(4) Heteroshape-heteroscale structure made of silica-shelled Ga microball-nanotube is rationally fabricated. Undergoing in situ electron-beam irradiation, an abnormal Ga liquid expansion in the nanotube was firstly observed. The expansion was due to an electric-hydraulic expansion effect via a huge inner pressure, which was induced by the repelling Coulomb force of positively charged Ga ions on the surface of Ga liquid. Under the theories of Ga expansion and classical electrostatics, the Ga-ions induced huge pressure is calculated. The electric-hydraulic expansion (EHE) effect can provide new insight for application in the family of micro-nano-electric-hydraulic devices.(5) Based on the large-area fabrication of Ga-filled carbon nanotubes, we provide new ideas of the application fields for Ga-filled carbon nanotubes. By using a "Nanofactory Instruments" scanning tunneling microscope (STM)-TEM joint instrument, under the different electric field, The Gallium performed the different patterns of movement, which was elaborated innovatively. In a single-electrode electric filed, we first find out gallium in the nanotube performs periodic elastic movement, which can be called "electric field - driven nanospring". The relevant theoretical explanation has been addressed by the elastic movement model. Moreover, in a double-electrode electric filed, the high current density makes the gallium migrate at the changing transport froml.328 fg s-1 to 10.345 fg s-1, where Ga-filled carbon nanotube can be considered as "electric field-driven high-speed mass conveyor".(6) In the driving of the high current density, the separation between the gallium and the nanotube was caused, and resulting in Ga fastly moving to the anode, but the slight variation of the nanotube resistance. In contrast, gallium mass transport in the low current density influences significantly the electrical transport property of the nanotube. Our results are potential to Ga-filled carbon nanotube as "electric field - driven rheostats or nanoswitches". (7) Basis on the research of nanothermometer, the new nanothermometer with the high sensitivity, wide measuring-temperature range and steady performance has been designed, each have special performances. (a) Ga-filled MgO nanotubes is the cubic-opening nanotubes with wide measuring-temperature range and high sensitivity up to 6.13nm/℃, which is one of the highest sensitivity in the reported nanothermometer. (b) Ga-filled SiO2 nanotubes not only have the wide measuring-temperature range and high sensitivity, but also good antioxidant and structural geometrical optimization, can be fabricated with large area. (c) By changing the experimental methods, we prepared the nanothermometer of Ga-filled carbon nanotubes with the high output and sensitivity. The development of these three nanothermometers resolved two main matter, one is the high-output fabrication, the other is the modified key performance, such as the problem of sensitivity, measuring-temperature range and steady performance, it provides the most striking evidences for the practice of nanothermometers.