Preparation And Optical Properties Of Hybrid Au-nanoparticle/Diamond Structure

Diamond, with many excellent characters, is one of the most important widebandgap semiconductor materials which has been widely applied in various fields.Recently, besides the growth characteristics of high quality bulk diamond and itsapplication, the investigations of diamond-related nanostructures and color center arebecoming the hot topic issues in diamond researches. Fabricaiton of structureddiamond can improve the inherent performance, or achieve some new propertiesrelated to the size and structure. Color centers in diamond are robust systems forpractical realization of various quantum information et al. applications for their highbrightness, photostability and room temperature operation. So far, there are more than500color centers, and the most investgated and applied are nitrogen-vacancy (N-V)and silicon-vacancy (Si-V) centers. In order to further improve the radiation quantumyield and luminous intensity, some researchers combined nanostructures with colorcenters in diamond, and then they have achieved important progress in both theoryand experiment. Therefore, the basic research and application field have been greatlybroaded.In this thesis, we fabricate a new diamond-realated hybrid structure of goldnanoparticle (Au NP)/diamond nanopit, which is called Au-NP/diamond-nanopit. Thefabrication process and its mechanism are studied. Moreover, the enhancedphotoluminescence (PL) of the Si-V center is realized based on this hybrid structure.The enhancement mechanism is discussed. Besides, the temperature-dependent PLcharacteristics are systemically investigated. The main content and innovation of thisthesis are listed as following:（1） A hybrid structure of a Au-NP/diamond-nanopit has been fabricated byusing a simple procedure of oxygen plasma etching of a Au-coated single crystaldiamond. The nanopit is of an inversely truncated pyramidal shaped, and is filled witha Au NP located at the bottom. The formation process is thoroughly investigated. It was found that the structure was induced by the interaction of oxygen plasma etchingand the plasma enhancement effect of Au NP. Here, the Au NPs enhanced the etchingprocess, which is completely different from the masking effect in the formation ofdiamond nanowires/rods. In addition, after the Au NPs were removed by soaking inaqua regia, the structure served as a structural template for fabricatingpyramid-structured poly(dimethylsiloxane) sheets.（2） Fabricate Au-NP/diamond-nanopit on Si-oped homoepitaxial chemicalvapor deposited (CVD) diamond films. The three-dimensional finite-differencetime-domain simulations reveal strong localized surface plasmon resonance (LSPR)scattering and enhanced electric field exhibited by this hybrid structure. Moreover, itis known that the LSPR peak at~718nm, and the electromagnetic field is enhanced atthe contact area between diamond and Au NP. Therefore, we proposed a concept of“hot ring” here. Experimentally, with excitation at633and830nm close to thecalculated LSPR wavelength, the PL intensities of the peak at738nm originatingfrom Si-V centers were significantly enhanced by factors of~100and~50,respectively, with respect to that from normal Si-doped diamond without the hybridstructure. By means of time-resolved PL measurements, the decay kineticmechanisms of the plasmon-related PL enhancement were investigated and arediscussed.（3） The emission features of zero phonon line (ZPL) of Si-V centers,obtained from the hybrid structure fabricated on Si-doped as-grown CVD diamond,were studied at temperatures from78K up to473K (200oC). In this temperatureregion, for the diamond with Au NPs, the emission intensity is significantly enhanced,and a related strong emission of Si-V center is still evident up to473K, whereasnearly no emission can be observed in the bare Si-doped diamond film asconventionally presented above room temperature. The energy of the emissionredshifts at elevated temperatures follows the T2+T4relationship. The magnitudes ofthe redshift and FWHM of the ZPL emission related to introducing Au NPs aresmaller than that for bare diamond.（4） Surface enhanced Raman scattering (SERS) performances based on theAu-NP/diamond-pit, using4-Mercaptopyridine as the probe molecule, show that the hybrid structure could realize a larger SERS enhancement factor compared to theconventional isolated Au NPs. This is attributed to the increased concentration ofincident light field on the Au NPs due to the special geometric feature, and thecoupling of LSPR from Au NPs.In this thesis, we fabricated a hybrid tructure of Au-NP/diamond-nanopit, andthouroughly investigated the fabrication process, as well as the LSPR-related PLenhancement of Si-V center and, SERS based on theory and experiment. This workbroadens the research field of diamond, and offers some meaningful foundation forthe development of diamond-related photoelectric device.