Fabrication Of Patterned Sapphire Substrate And Silicon Nanowires

LEDs are the light source which is energy conservational and environment friendly. Due to their high efficiency in the process of photovoltaic conversion, long life and small size, they are widely applied to monitors, cars and traffic lights. What’s more, after the appearance of InGaN/GaN based blue LEDs, the fabrication of white LEDs became easier, and therefore LEDs are more commonly applied to outdoor-lightening facilities.The one-dimensional materials have been widely studied since the discovery of carbon nano tube. The researchers hope that Si, which has the highest theoretical specific capacity of 4200 mAh/g, could replace the common-used graphite as a negative electrode material in the lithium battery to increase the battery capacity. However, huge volume change during lithium insertion and extraction leads to material pulverization. SiNWs as a kind of one-dimensional materials have high-aspect-ratio, large specific surface area and good mechanical property, so they may solve this problems. In addition, in the areas of low-pressure gas detection, biological sensor, ion concentration detection and nanoimprint molds, SiNWs all have the potential application values. The article mainly studies the fabrication of nano-patterned sapphire substrates and the SiNWs.Generally, people use hard nanoimprint mold to fabricate nano-patterned sapphire subsrates. Since the sapphire substrate is not flat as silicon wafer and somewhat warped, the hard nanoimprint mold may cause lots of defects. Meanwhile, the imprint molds can be easily damaged. The part one of the thesis tries to solve the two problems.The traditional methods to fabricate SiNWs include vapor-liquid-solid method ( VLS), laser ablation method, CVD, etc. These methods are expensive or require the harsh reaction conditions and SiNWs are easily polluted by the catalyst. Additionally, the fabrication process is hard to control. The part two of the thesis tries to use a new technology to solve the problems and explores the practical application.Basing on the demands of fabricating nanopatterns with wafer-scale and low-cost, we do the followed work:The fabrication of nano-patterned sapphire substrate ( NPSS) by hybrid nanoimprint soft lithography (HNSL). During the imprint process, we use the single-layer resist and double-layer resist to fabricate NPSS. We use dry and wet etching methods to fabricate NPSS with the resist as the etching mask. We compare the advantages and the disadvantages of the two methods. Finally, we find that using Ni as the etching mask can fabricate good structures with dry etching. To study the NPSS’s effect on blue LEDs, we use MOCVD to fabricate blue LEDs, and test their property. We conclude that compared to LEDs grown on flat substrate, LEDs on NPSS have an obvious promotion in PL and EL.Fabricate high aspect ratio silicon structure based on nanoimprint and sputtering techonology. We use sputtering technology to fabricate disordered gold nano-structure in large area, and based on the structure, we use gold assisted chemical etching to fabricate high aspect ratio silicon pole. Then we use nanoimprint method including spin coating, imprint, evaporation, lift off, etc. to fabricate periodic gold nano-structure and in the same way we use gold assisted chemical etching to fabricate high ratio aspect silion nanowires array. This kind of high aspect ratio silicon nano-structure has potential applications in nanoimprint molds, biological detection and the negative electrode in the li-ion battery.The article has four chapters. The first chapter introduces the nanoimprint technology. The second chapter includes the development of LED and the advantages of blue light of LED using patterned sapphire substrates. The third chapter successfully fabricates silicon nanowires and tries to use them into Lithium-ion battery. The last one is a conclusion and expectation.