Study On Low-Destructive Friction-Induced Nanofabrication On Quartz

Nanotechnology is one of the most important research topics in the21st century, which has a profound influence on the development of human society. Nanofabrication method is the foundation of the transition from nanoscience and nanotechnology to application. As the device dimension down to nanoscale, the traditional nanofabrication technologies have met serious technical challenges, such as poor resolution, complex processes and fabrication destruction etc. Researches on nanofabrication methods can not only meet the requirements of the nanotechnology, but also facilitate the great-leap-forward development of China in the violent international competition.In this doctoral thesis, low-destructive friction-induced nanofabrication methods on quartz are proposed. Firstly, hillock nano structures can be directly fabricated by scratching a diamond tip at the target area before the yield of quartz. The mechanical performance of the hillock is similar to the quartz substrate, but the chemical stability is weaker. To further reduce the fabrication destruction, friction-induced selective etching is developed by combination of the wearless scanning the quartz surface and selective etching the sample in KOH. The effects of the scan parameters and etching temperature on the fabrication are studied thoroughly. The fabrication mechanism is analyzed by transmission electron microscope observation, X-ray photoelectron spectroscope analysis and etc. Results show that the chemical etching can improve the fabrication quality. Finally, to discuss the mechanism of friction-induced selective etching and the role of chemistry in the low-destructive fabrication, the friction-induced nanofabrication is also practiced on glass and GaAs. The main contents of thesis are shown in follows.(1) Based on the clarification of the formation mechanism of friction-induced hillocks on quartz surface, the direct friction-induced nanofabrication on quartz is proposed.The protrusive nanostructures can be produced by sliding a diamond tip on quartz when the contact pressure is ranged from0.4Py to Py (Py is the critical yield pressure of quartz). The height of these nanostructures increases with the increase of the number of scratching cycles or the normal load. X-ray photoelectron spectroscopy and transmission electron microscope observation indicates that the mechanical interaction playes a dominating role during the fabrication. Various nanostructures such as nanodots, nanolines, surface mesas and nanowords can be fabricated by programming the tip traces according to the demanded patterns. Although the protrusive nanostructures exhibit a slightly lower elastic modulus than quartz substrate (decreased by1.1-11.6%), they can resist the typical contact pressure in MEMS. Such nanostructures can be selectively dissolved in20%KOH solution, which can provide an erasing technique for this method.(2) The fabrication rules and mechanism of the selective etching on scanned quartz surface are revealed, and the friction-induced selective etching on quartz surface is proposed.Nanofabrication on quartz can also be achieved by wearless scanning on a target area and post-etching in a KOH solution. The etching thickness on the wearless scan area increases with the increase of the scan load and scan cycles but decreases with the scan speed. Higher etching temperature below318K can improve the fabrication efficiency and does not change the final fabrication depth. Transmission electron microscope observation shows that the distorted lattice can not be etched by KOH. Combinning with the contradistinctive etching experiments, the fabrication mechanism could be summarized as the selective etching of friction-induced amorphous layer on fabrication surface. Chemical kinetics analysis shows that the dependence of the etching rate on the contact pressure should be mainly attributed to the variation of frequency factor and the concentration of reactants, rather than the decrease of the activation energy. The reaction pathway may be related to the preferential diffusion of solutes into the fabrication area. By optimizing the scan parameters and etching temperature, various nanostructures including line arrays, slops, hierarchical stages can be fabricated on quartz surface in a low-destruction and high efficiency way. These nanostructures have a stronger chemical stability and a better mechanical performance (the elastic modulus is only0.2-2.6%lower than the substrate). This means that the selective etching can reduce the fabrication destruction in higher level.(3) To further understand the friction-induced selective etching and the role of chemistry in the low-destructive fabrication, friction-induced nanofabrication is practiced on glass and GaAs.X-ray photoelectron spectroscopy shows that the fluorine species can preferentially diffuse into the scan area on glass and form AIF3. Such insoluble AIF3acts as a mask layer to prevent the etching of glass and then the protrusive nanostructures are formed on the fabrication area after HF etching. Therefore, the friction-induced selective etching is further verified and a maskless nanofabrication on glass is proposed. Another low-destructive method is attempted for fabricating "defect free" nanofabrication on GaAs based on the tribochemical reaction. Tribochemical reaction facilitates the removal of GaAs material when the contact pressure was only11%of the critical yield pressure of GaAs. Transmission electron microscope observation shows that there is no lattice damage beneath the fabrication area.In brief, based on the friction-induced structural and chemical modification, low-destructive nanofabrication methods are developed on quartz. The friction-induced nanofabrication of glass and GaAs deepens the understanding of the involved mechanism. The results in this thesis can not only enrich the nanotribology theory, but also encourage the application of the low-destructive friction-induced nanofabrication on quartz and other materials.