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Investigation of Si Substrate Surface Modification by Wet Chemical Methods

Author: LiuHongTao
Tutor: QiYang
School: Northeastern University
Course: Materials Physics and Chemistry
Keywords: Si(100) single crystal V-grooves STO film Liquid phase deposition(LPD) reverse microemulsion hydrothermal method hexagonal ZnO
CLC: O613.72
Type: Master's thesis
Year: 2010
Downloads: 21
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Abstract

This paper demonstrates thoroughly the theoretical analysis about the anisotropic wet etching property of the silicon material. Anisotropic wet etching method was used to modify the surface pattern of single Si(100) substrate and good V-groove structures were obtained. Liquid phase deposition(LPD) was adopted to obtain STO film on the Si substrates with V-grooves. The quality STO film was improved by optimizing experimental parameters. The ZnO with different special nanostructures has been successfully synthesized using a novel microemulsion hydrothermal method on the Si substrates with V-grooves. The main contents of the dissertation are as follows:1. The fabrication of V-grooves on single Si(100) substrate. The5mol/L KOH and lmol/L IPA solutions were used as echants, and the TiO2film was deposited on the Si(100) substrate as resist mask by RF-magnetron sputtering. Parallel and continuous V-grooves were formed on Si(100) substrate. The results reveal that the depth and width of V-grooves decreased gradually with the increase of etching time and Water bath temperature, and the mask was also consumed continuously. Top of the grooves were corroded and the structure were deteriorated when the mask was exhausted. V-grooves with smooth sidewalls were obtained when the etching time was30min. the water bath temperature was50℃and the thickness of TiO2mask was200nm. Meanwhile, V-grooves could also be obtained using isotropic wet etching method based on anisotropic etching method. The modified substrate with V-grooves is the excellent substrate and it is the base for the fabrication of ZnO nanostructures.2. Liquid phase deposition method. Hydrophilic time, deposition temperature and annealing temperature were studied to improve the morphology and crystallinity of STO film. The results of XRD and SEM revealed that the quality of STO film prepared via LPD depended on the wettability of substrate surface, and the wettability was desirable when the hydrophilic time was10min. In the process of mixing up precursors, boric acid should be added slowly. Smooth STO film was obtained when the deposition temperature was40℃, followed by annealing at650℃for4h, and large grains appeared while increasing the deposition temperature.3. The fabrication of ZnO nanostructure on the modified Si substrates. The microemulsion system was yielded by water, CTAB, n-butyl alcohol and cyclohexane, where the reversed micelles was used as the cores. The ZnO nanostructures were successfully fabricated by adding a little sol on the interface a. While investigating different hydrothermal treated time, reaction temperature, sintering temperature and substrates, the tubular ZnO hexagonal twinning microprisms on the modified Si substrate were obtained when the solutions were hydrothermally treated at120℃for2h and then heated at350℃for2h. With the increase of the hydrothermal treated time or the reaction temperature, the section of hollow ZnO started to close and finally, formed columnar ZnO hexagonal twinning microprisms. In the heating process, when the sintering temperature was too low, it would reside organic residuals on substrate but the very high Sintering temperature led to the collapse of the structure of hollow ZnO. The change of the substrates had little effects on the morphology and sizes of ZnO nanostructures.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Non-metallic elements and their compounds > Part Ⅳ family of non-metallic elements (carbon and silicon ) and its compounds > Si Si
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