Studies On Si-based Nanoscaled Light-emitting Materials And Structures Fabricated By Si-based Anodic Porous Alumina Film

With the developments of nano-science and nano-technology, the integrated microelectronic technique based on silicon is now being developed into integrated nano-electronics. Moreover, photon signals will be introduced into integration, which is to develop integrated nano-optoelectronics. Therefore, it is very important to fabricate silicon based light-emitting nanomaterials and nanostructures with uniform size and regular distribution. Anodic porous alumina film has been successfully transferred onto silicon substrate, thus it could be used as a template or a mask to prepare Si-based nanoscaled compounds or quantum dots array by different kinds of physical and chemical methods. These results will have great effects in the research areas of nano-electronics and nano-optoelectronics.In this dissertation, we made use of Si-based anodic porous alumina film to prepare Si-based nanoscaled light-emitting materials and structures. The combination of chemical and physical methods has been emphasized through the whole research, which includes the following sections:1. The mesoporous compound materials of C60 molecules adjacent to porous silicon or Si-based nanoporous alumina were fabricated and characterized by the photoluminescence and photoluminescence excitation spectra. It was observed that the PL spectra of porous silicon could be affected with the deposition of C60 molecules. But C60 molecules had no effect on the PL spectra of Si-based nanoporous alumina. In addition, different kinds of laser dyes were impregnated into Si-based nanoporous alumina and utilized to obtain blue, green and red emission at room temperature. The blue shift of emission spectra was also found. The results show that the interaction mechanism between the impregnated materials and the host matrices such as nanoporous alumina and porous silicon is different and the PL properties of impregnated materials are directly affected by the PL mechanism of the host matrices. It is noticeable that Si-based nanoporous alumina could be used as host matrices for a variety of luminescent media to obtain light dots in nanometer size.2. CdS nanocrystallites encapsulated in poly (ethylene oxide) polymer were prepared and the optical and microstructure properties were studied. It has been found that PEO could be used as a chemical template for providing a confined media for CdS neucleation and particle growth. Thus the size of CdS nanocrystallites could be controlled by changing the Cd2+ concentration in PEO. Optical properties of the above nanocrystallites show coherent change with the varieties of the particle dimensions, which could be explained by size quantization effects. Based on this study, a convenient method is presented to achieve regular arrangement of CdS nanocrystallites. CdS/PEO complex was deposited into the nanopores of Si-based porous alumina films. The morphology of CdS/PEO in the film was proved to be in tube shape. Si-based porous alumina film acts as a physical template to form an ordered arrangement of CdS and PEO as a chemical template is used to control the crystallite sizes. It is easier to obtain regular and size-controllable quantum dot array by the combination of chemical and physical templates technique.3. A layer of thin gold film was sandwiched between the silicon substrate and Al film to form Al/Au/Si structure. Subsequent anodization leads to formation of a Si-based anodic alumina oxide (AAO) template (AAO/Au/Si structure) with ordered nanopores. Anodic process of the Al/Au/Si structure was investigated in detail by in situ monitoring the current–time curve. This kind of templates has unique electrodeposition property and can bond well with the deposited materials. As an application example, CdS nanowires were fabricated on the silicon substrate using this kind of AAO templates. Light-emitting property from the CdS nanowires was revealed. 4. A SiO2 nanoscaled island array was fabricated on Si substrate by using anodic porous alumina as a mask. A copper nanoscaled island array was also obtained by the similar preparation route. The possible applications of the above nano-structures were proposed.5. Silicon based porous anodic aluminum oxide films were prepared by anodization in traditional H2SO4, H3PO4, and H2C2O4, respectively. It was found that PL spectra of the films prepared in various electrolytes presented different emission. Based on this result, another electrolyte, sulfosalicylic acid was used and a kind of laser dye, Rhodamine 6G was also added in advance in H2C2O4 solution to synthesize Si-based alumina. Both of them showed characteristic PL properties. According to previous theories of the PL mechanism of porous alumina, it has been suggested that luminescence center of the alumina films, which usually originate from the F+ center could be affected by the local structure related to the components incorporated in the films. These species coming from the electrolyte will be responsible for the varied emissions.6. Other work related to nanoscaled light-emitting semiconductor materials: ZnO nanoparticles were synthesized by thermal decomposition of Zn(CH3COO)2 under the inclusion effects ofβ-cyclodextrin. ZnO nanoparticles obtained by this method present highly regular size distribution and good optical properties. The possible mechanism was proposed.