In this work,we demonstrate that ultraviolet(UV)laser photolysis of hydrocarbon species alters the flame chemistry such that it promotes the diamond growth rate and film quality.Optical emission spectroscopy and laser...In this work,we demonstrate that ultraviolet(UV)laser photolysis of hydrocarbon species alters the flame chemistry such that it promotes the diamond growth rate and film quality.Optical emission spectroscopy and laser-induced fluorescence demonstrate that direct UV laser irradiation of a diamond-forming combustion flame produces a large amount of reactive species that play critical roles in diamond growth,thereby leading to enhanced diamond growth.The diamond growth rate is more than doubled,and diamond quality is improved by 4.2%.Investigation of the diamond nucleation process suggests that the diamond nucleation time is significantly shortened and nondiamond carbon accumulation is greatly suppressed with UV laser irradiation of the combustion flame in a laser-parallel-to-substrate geometry.A narrow amorphous carbon transition zone,averaging 4 nm in thickness,is identified at the film–substrate interface area using transmission electron microscopy,confirming the suppression effect of UV laser irradiation on nondiamond carbon formation.The discovery of the advantages of UV photochemistry in diamond growth is of great significance for vastly improving the synthesis of a broad range of technically important materials.展开更多
Forsterite particles doped with europium ions（Eu^（3＋）） were synthesized via a solution combustion method. The effect of co-dopants on photoluminescence intensity was described. Different percentages of calcium（...Forsterite particles doped with europium ions（Eu^（3＋）） were synthesized via a solution combustion method. The effect of co-dopants on photoluminescence intensity was described. Different percentages of calcium（Ca^（2＋））, zinc（Zn^（2＋））, barium（Ba^（2＋）） and strontium（Sr^（2＋）） were added to the Mg2SiO4：Eu^（3＋）host.The synthesized sample was characterized by X-ray diffraction, transmission electron microscopy,scanning electron microscopy, spectrofluorometer and the FTIR spectroscopy. X-ray diffraction（XRD）results revealed that dominant phase was forsterite in all samples. Additionally, a negligible amount of periclase phase was recognized in the samples. The average size of the synthesized particles was less than 200 nm. The presence of co-dopant led to an enhancement in the photoluminescent property of the synthesized samples. The maximum increase in photoluminescence intensity was obtained by Ba^（2＋）ions as a co-dopant. Condensed films of photoluminescence particles were produced by utilizing electrophoresis technique to deposit particles. The results showed that polyvinyl pyrrolidone was the best surface modifier to raise the mass deposition of the samples on the substrate.展开更多
基金the financial support from the National Science Foundation(CMMI 1265122)the Nebraska Center for Energy Sciences Research(NCESR).
文摘In this work,we demonstrate that ultraviolet(UV)laser photolysis of hydrocarbon species alters the flame chemistry such that it promotes the diamond growth rate and film quality.Optical emission spectroscopy and laser-induced fluorescence demonstrate that direct UV laser irradiation of a diamond-forming combustion flame produces a large amount of reactive species that play critical roles in diamond growth,thereby leading to enhanced diamond growth.The diamond growth rate is more than doubled,and diamond quality is improved by 4.2%.Investigation of the diamond nucleation process suggests that the diamond nucleation time is significantly shortened and nondiamond carbon accumulation is greatly suppressed with UV laser irradiation of the combustion flame in a laser-parallel-to-substrate geometry.A narrow amorphous carbon transition zone,averaging 4 nm in thickness,is identified at the film–substrate interface area using transmission electron microscopy,confirming the suppression effect of UV laser irradiation on nondiamond carbon formation.The discovery of the advantages of UV photochemistry in diamond growth is of great significance for vastly improving the synthesis of a broad range of technically important materials.
文摘Forsterite particles doped with europium ions（Eu^（3＋）） were synthesized via a solution combustion method. The effect of co-dopants on photoluminescence intensity was described. Different percentages of calcium（Ca^（2＋））, zinc（Zn^（2＋））, barium（Ba^（2＋）） and strontium（Sr^（2＋）） were added to the Mg2SiO4：Eu^（3＋）host.The synthesized sample was characterized by X-ray diffraction, transmission electron microscopy,scanning electron microscopy, spectrofluorometer and the FTIR spectroscopy. X-ray diffraction（XRD）results revealed that dominant phase was forsterite in all samples. Additionally, a negligible amount of periclase phase was recognized in the samples. The average size of the synthesized particles was less than 200 nm. The presence of co-dopant led to an enhancement in the photoluminescent property of the synthesized samples. The maximum increase in photoluminescence intensity was obtained by Ba^（2＋）ions as a co-dopant. Condensed films of photoluminescence particles were produced by utilizing electrophoresis technique to deposit particles. The results showed that polyvinyl pyrrolidone was the best surface modifier to raise the mass deposition of the samples on the substrate.
