Multilayer Etching And Transfer Of Silicon Nanowire Arrays For SERS And Optoelectronic Application

As a typical one dimensional nano-semiconductor material, Silicon nanowirearrays (SiNWs) have tremendous potential in nano-optoelectronic devices, new energyand biological applications due to amazing physical and chemical properties. But inpractical applications SiNWs usually associated with the growth substrate as a whole.So there are lots of challenges for the photovoltic device based on SiNWs, such as howto reduce the cost and how to transfer the SiNWs from the growth substrate to flexibleone. Therefore, it remains a critical challenge to develop a general method for SiNWstransfer from the growth substrate.In this thesis, we have developed a feasible air-heating approach to achieve themultilayer etching and roll-to-roll (R2R) transfer of SiNW arrays. The main results aresummarized as follows：Firstly, we developed a feasible air-heating combined with MCEE approach formultilayer SiNWs fabrication. And then we studied the mechanism of the air heatingapproach. In order to study the universality of the method, we fabricated crackedSiNWs on different kinds of Si wafer with different orientations, doping type andconcentration. To make the full use of the Si wafer, we fabricated multilayer SiNWs onthe same substrate and transfer them several times to flexible substrates. Then wedeveloped two methods to continue the use of Si wafer, therefore achieving the purposeof reducing costs. We fabricated cracked SiNWs on a4inch wafer and achieve thewafer-scale transfer of the SiNW array by R2R transfer method.Secondly, we fabricated flexible surface enhanced Raman substrate (SERS) usingAg nanoparticles modified SiNWs. Using rhodmine6G as target molecule, we testedthe surface enhanced effect (SERS) of Ag modified SiNWs on flexible substrate as the SERS substrate which is different from the normal ones. Its excellent property providesnew possibilities for its future in bio-applications.Thirdly, we develop a novel flexible vertical aligned SiNWs electronic deviceusing transparent graphene film as top electrode on flexible substrate. The SiNWs withuniform length was fabricated by Ag assisted electroless etching method and thencoated with PDMS by spin-coating. The SiNWs/graphene heretrojuncton structure ofthe device replaced the common p-n homojuntion whose process was time-consumingand very expensive. The device shows good diode characteristic and photoresponse, andprovides new opportunity for SiNWs in the flexible thin film photovoltic device.