Poly(methylhydrosiloxane)was modified with methylmethacrylate by the hydrosilylation reaction,using Pt as the catalyst.The reaction was operated at the high temperature(about 140℃).
Different silicidation processes are employed to form NiSi,and the NiSi/Si interface corresponding to each process is studied by cross-section transmission electron microscopy （XTEM）. With the sputter deposition of ...Different silicidation processes are employed to form NiSi,and the NiSi/Si interface corresponding to each process is studied by cross-section transmission electron microscopy （XTEM）. With the sputter deposition of a nickel thin film,nickel silicidation is realized on undoped and doped （As and B） Si（001） substrates by rapid ther mal processing （RTP）. The formation of NiSi is demonstrated by X-ray diffraction and Raman scattering spectros- copy. The influence of the substrate doping and annealing process （one-step RTP and two-step RTP） on the NiSi! Si interface is investigated. The results show that for one-step RTP the silicidation on As-doped and undoped Si substrates causes a rougher NiSi/Si interface,while the two-step RTP results in a much smoother NiSi/Si interface. High resolution XTEM study shows that axiotaxy along the Si（111） direction forms in all samples, in which specific NiSi planes align with Si（111） planes in the substrate. Axiotaxy with spacing mismatch is also discussed.展开更多
Porous silicon samples are made on Si wafers with different resistivities under different anod ic-react ion conditions. Visible photoluminescent spectra of porous silicon (PS) at room temperature are measured using a ...Porous silicon samples are made on Si wafers with different resistivities under different anod ic-react ion conditions. Visible photoluminescent spectra of porous silicon (PS) at room temperature are measured using a fluorescent spectrograph where blue-violet light is observed. The decision of the resistivity of Si substrates is provided.展开更多
Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The C...Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The CoSi 2/Si Schottky contacts are measured with the current-voltage and capacitance-voltage (I-V/C-V) techniques within the range of temperature from 90K to room temperature.The measured I-V characteristics have been analyzed with a model based on the inhomogeneity in Schottky barrier height,i.e.,at high temperatures (≥～200K) or low temperatures but with a large bias,the I-V curves can be described by using the thermionic emission theory with a Gaussian distributed barrier height over the whole junction,while at low temperatures and with a small bias,the current is dominated by some small patches with low barrier height.It results in a plateau-like section in the low temperature I-V curves around 10 -7 A.At room temperature,the barrier height of polycrystalline CoSi 2/Si deduced from the I-V curve is about 0 57eV.For epitaxial CoSi 2,the barrier height depends on its final annealing temperature and increases from 0 54eV to 0 60eV with the annealing temperature increasing from 700℃ to 900℃.展开更多
Single-atom catalysis,the catalysis by single-atom catalysts(SACs),has attracted considerable attention in recent years as a new frontier in the heterogeneous catalysis field.SACs have the advantages of both homogeneo...Single-atom catalysis,the catalysis by single-atom catalysts(SACs),has attracted considerable attention in recent years as a new frontier in the heterogeneous catalysis field.SACs have the advantages of both homogeneous catalysts(isolated active sites)and heterogeneous catalysts(stable and easy to separate),and are thus predicted to be able to bridge the homo-and heterogeneous catalysis.This prediction was first experimentally demonstrated in 2016.In this mini-review,we summarize the few homogeneous catalysis progresses reported recently where SACs have exhibited promising application:a)Rh/ZnO and Rh/CoO SAC have been used successfully in hydroformylation of olefin of which the activity are comparable to the homogeneous Wilkinson’s catalyst;b)a Pt/Al2O3 SAC has shown excellent performance in hydrosilylation reaction;and c)M-N-C SACs(M=Fe,Co etc.)have been applied in the activation of C–H bonds.All of these examples suggest that fabrication of suitable SACs could provide a new avenue for the heterogenization of homogeneous catalysts.These pioneering works shed new light on the recognition of single-atom catalysis in bridging the homo-and heterogeneous catalysis.展开更多
文摘Poly(methylhydrosiloxane)was modified with methylmethacrylate by the hydrosilylation reaction,using Pt as the catalyst.The reaction was operated at the high temperature(about 140℃).
文摘Different silicidation processes are employed to form NiSi,and the NiSi/Si interface corresponding to each process is studied by cross-section transmission electron microscopy （XTEM）. With the sputter deposition of a nickel thin film,nickel silicidation is realized on undoped and doped （As and B） Si（001） substrates by rapid ther mal processing （RTP）. The formation of NiSi is demonstrated by X-ray diffraction and Raman scattering spectros- copy. The influence of the substrate doping and annealing process （one-step RTP and two-step RTP） on the NiSi! Si interface is investigated. The results show that for one-step RTP the silicidation on As-doped and undoped Si substrates causes a rougher NiSi/Si interface,while the two-step RTP results in a much smoother NiSi/Si interface. High resolution XTEM study shows that axiotaxy along the Si（111） direction forms in all samples, in which specific NiSi planes align with Si（111） planes in the substrate. Axiotaxy with spacing mismatch is also discussed.
文摘Porous silicon samples are made on Si wafers with different resistivities under different anod ic-react ion conditions. Visible photoluminescent spectra of porous silicon (PS) at room temperature are measured using a fluorescent spectrograph where blue-violet light is observed. The decision of the resistivity of Si substrates is provided.
文摘Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The CoSi 2/Si Schottky contacts are measured with the current-voltage and capacitance-voltage (I-V/C-V) techniques within the range of temperature from 90K to room temperature.The measured I-V characteristics have been analyzed with a model based on the inhomogeneity in Schottky barrier height,i.e.,at high temperatures (≥～200K) or low temperatures but with a large bias,the I-V curves can be described by using the thermionic emission theory with a Gaussian distributed barrier height over the whole junction,while at low temperatures and with a small bias,the current is dominated by some small patches with low barrier height.It results in a plateau-like section in the low temperature I-V curves around 10 -7 A.At room temperature,the barrier height of polycrystalline CoSi 2/Si deduced from the I-V curve is about 0 57eV.For epitaxial CoSi 2,the barrier height depends on its final annealing temperature and increases from 0 54eV to 0 60eV with the annealing temperature increasing from 700℃ to 900℃.
基金supported by National Natural Science Foundation of China(21606222,21776270)Postdoctoral Science Foundation(2017M621170,2016M601350)~~
文摘Single-atom catalysis,the catalysis by single-atom catalysts(SACs),has attracted considerable attention in recent years as a new frontier in the heterogeneous catalysis field.SACs have the advantages of both homogeneous catalysts(isolated active sites)and heterogeneous catalysts(stable and easy to separate),and are thus predicted to be able to bridge the homo-and heterogeneous catalysis.This prediction was first experimentally demonstrated in 2016.In this mini-review,we summarize the few homogeneous catalysis progresses reported recently where SACs have exhibited promising application:a)Rh/ZnO and Rh/CoO SAC have been used successfully in hydroformylation of olefin of which the activity are comparable to the homogeneous Wilkinson’s catalyst;b)a Pt/Al2O3 SAC has shown excellent performance in hydrosilylation reaction;and c)M-N-C SACs(M=Fe,Co etc.)have been applied in the activation of C–H bonds.All of these examples suggest that fabrication of suitable SACs could provide a new avenue for the heterogenization of homogeneous catalysts.These pioneering works shed new light on the recognition of single-atom catalysis in bridging the homo-and heterogeneous catalysis.
