Among the three main methods for the s ynthesis of carbon nanotubes(CNTs ),chemical vapor deposition(CVD)has received a great deal of attentio n since CNTs can be synthesized at sig nificantly low temperature.Plasma c...Among the three main methods for the s ynthesis of carbon nanotubes(CNTs ),chemical vapor deposition(CVD)has received a great deal of attentio n since CNTs can be synthesized at sig nificantly low temperature.Plasma chemical vapor deposition me thods can synthesize CNTs at lower te mperature than thermal CVD.But in th e usual catalytic growth of CNTs by CVD,CNTs are often tangled together and have some defects.These will limit t he property research and potential applications.How to synthesize the str aight CNTs at low temperature become s a challenging issue.In this letter,s traight carbon nanotube(CNT)films were achieved by microwave pla sma chemical vapor deposition(MWPCVD)catalyzed by round Fe-Co-Ni alloy particles on Ni substrate at 610℃.It wa s found that,in our experimental condition,the uniform growth rate along the circumference of round alloy particles plays a very important role in the gro wth of straight CNT films.And because the substrate is conducting,the straight CNT films grown at low temperature ma y have the benefit for property research and offer the possibility to use t hem in the future applications.展开更多
氮化镓(GaN)器件的自热问题是目前限制其性能的关键因素,在GaN材料上直接生长多晶金刚石改善器件的自热问题成为研究的热点,多晶金刚石距离GaN器件工作有源区近,散热效率高,但多晶金刚石和GaN材料热失配可能会导致GaN电特性衰退.本文采...氮化镓(GaN)器件的自热问题是目前限制其性能的关键因素,在GaN材料上直接生长多晶金刚石改善器件的自热问题成为研究的热点,多晶金刚石距离GaN器件工作有源区近,散热效率高,但多晶金刚石和GaN材料热失配可能会导致GaN电特性衰退.本文采用微波等离子体化学气相沉积法,在2 in (1 in=2.54 cm)Si基GaN材料上生长多晶金刚石.测试结果显示,多晶金刚石整体均匀一致,生长金刚石厚度为9—81 μm,随着多晶金刚石厚度的增大, GaN (002)衍射峰半高宽增量和电性能衰退逐渐增大.通过激光切割和酸法腐蚀,将Si基GaN材料从多晶金刚石上完整地剥离下来.测试结果表明:金刚石高温生长过程中,氢原子对氮化硅外延层缺陷位置有刻蚀作用形成孔洞区域,刻蚀深度可达本征GaN层;在降温过程,孔洞周围形成裂纹区域.剥离下来的Si基GaN材料拉曼特征峰峰位, XRD的(002)衍射峰半高宽以及电性能均恢复到本征状态,说明多晶金刚石与Si基GaN热失配产生应力,引起GaN晶格畸变,导致GaN材料电特性衰退,这种变化具有可恢复性,而非破坏性.展开更多
The synthesis of carbon nanotubes￡¨CNTs ￡(c)at low temperature has received a gre at deal of attention and be-comes a challenging issue￡(r)But few mo del which accounts for the growth of C NTs is suited for th...The synthesis of carbon nanotubes￡¨CNTs ￡(c)at low temperature has received a gre at deal of attention and be-comes a challenging issue￡(r)But few mo del which accounts for the growth of C NTs is suited for the synthesis of CNTs by microwave plasma chemical vapor deposition￡¨MWPCVD￡(c)at low temperature because most rese archers conclude that the growth mechanism is determi ned by the catalyst-supporter interaction while ignored the diffusion o f carbon in the catalyst￡(r)In this paper,under the catalytic effect of cobalt supported by SiO 2 and Al 2 O 3 ,CNTs are synthe-sized by MWPCVD at about 500℃,and tip-growth,the model which accounts fo r the catalytic growth of CNTs is outlined￡(r)It is the temperature difference between the upper and bottom o f the catalytic particle that results in the diffusion of carbon atoms from upper to the bottom,and precipitation of s aturated carbon on the bottom surface to form CNTs￡(r)展开更多
In this paper, under the catalytic effect of nickel particles electro-deposited on Ni substrate, self-aligned carbon nanotubes were synthesized by microwave plasma chemical vapor deposition with a mixture of methane a...In this paper, under the catalytic effect of nickel particles electro-deposited on Ni substrate, self-aligned carbon nanotubes were synthesized by microwave plasma chemical vapor deposition with a mixture of methane and hydrogen gases at 510 ℃. During the process of nanotubes growth, the total pressure in the chamber was kept at 3 kPa, the microwave plasma input power was 500 W, and the flow rates of H 2 and CH 4 were 50 and 1 mL/min, respectively. The aligned features and hollow structure have been verified by scanning electron and transmission electron microscopic images. As the nanotubes grow, the nickel cap remains on the tip of the carbon nanotubes. The nanotubes′diameter is about 70 nm and they have bamboo structures. Because of the strong etching ability of hydrogen plasma and the low volume ratio of H 2/CH 4, no carbonaceous particles attached to the carbon nanotubes were found. It demonstrats that MWPCVD is a very efficient process for the synthesis of the aligned carbon nanotubes at a low temperature. The aligned CNTs grown on Ni substrate at such a low temperature are suitable for device fabrication.展开更多
Under the assistant effect of sulfur, carbon nanotubes electrodes were prepared on the end of tungsten strings directly through microwave plasma chemical vapor deposition. And the electrochemical behavior of CuSO4 at ...Under the assistant effect of sulfur, carbon nanotubes electrodes were prepared on the end of tungsten strings directly through microwave plasma chemical vapor deposition. And the electrochemical behavior of CuSO4 at the carbon nanotubes electrodes was investigated. Compared to the graphite electrode, carbon nanotubes elec- trodes had better electrochemical behavior for the analysis of Cu2+. Different electrodes prepared under the same condition showed good consistency of electrochemical detection property. And because carbon nanotubes were synthesized directly on the end of tungsten strings, the results of long-term stability experiments demonstrated that the carbon nanotubes electrodes had stable response to Cu2+ solution.展开更多
文摘Among the three main methods for the s ynthesis of carbon nanotubes(CNTs ),chemical vapor deposition(CVD)has received a great deal of attentio n since CNTs can be synthesized at sig nificantly low temperature.Plasma chemical vapor deposition me thods can synthesize CNTs at lower te mperature than thermal CVD.But in th e usual catalytic growth of CNTs by CVD,CNTs are often tangled together and have some defects.These will limit t he property research and potential applications.How to synthesize the str aight CNTs at low temperature become s a challenging issue.In this letter,s traight carbon nanotube(CNT)films were achieved by microwave pla sma chemical vapor deposition(MWPCVD)catalyzed by round Fe-Co-Ni alloy particles on Ni substrate at 610℃.It wa s found that,in our experimental condition,the uniform growth rate along the circumference of round alloy particles plays a very important role in the gro wth of straight CNT films.And because the substrate is conducting,the straight CNT films grown at low temperature ma y have the benefit for property research and offer the possibility to use t hem in the future applications.
文摘氮化镓(GaN)器件的自热问题是目前限制其性能的关键因素,在GaN材料上直接生长多晶金刚石改善器件的自热问题成为研究的热点,多晶金刚石距离GaN器件工作有源区近,散热效率高,但多晶金刚石和GaN材料热失配可能会导致GaN电特性衰退.本文采用微波等离子体化学气相沉积法,在2 in (1 in=2.54 cm)Si基GaN材料上生长多晶金刚石.测试结果显示,多晶金刚石整体均匀一致,生长金刚石厚度为9—81 μm,随着多晶金刚石厚度的增大, GaN (002)衍射峰半高宽增量和电性能衰退逐渐增大.通过激光切割和酸法腐蚀,将Si基GaN材料从多晶金刚石上完整地剥离下来.测试结果表明:金刚石高温生长过程中,氢原子对氮化硅外延层缺陷位置有刻蚀作用形成孔洞区域,刻蚀深度可达本征GaN层;在降温过程,孔洞周围形成裂纹区域.剥离下来的Si基GaN材料拉曼特征峰峰位, XRD的(002)衍射峰半高宽以及电性能均恢复到本征状态,说明多晶金刚石与Si基GaN热失配产生应力,引起GaN晶格畸变,导致GaN材料电特性衰退,这种变化具有可恢复性,而非破坏性.
文摘The synthesis of carbon nanotubes￡¨CNTs ￡(c)at low temperature has received a gre at deal of attention and be-comes a challenging issue￡(r)But few mo del which accounts for the growth of C NTs is suited for the synthesis of CNTs by microwave plasma chemical vapor deposition￡¨MWPCVD￡(c)at low temperature because most rese archers conclude that the growth mechanism is determi ned by the catalyst-supporter interaction while ignored the diffusion o f carbon in the catalyst￡(r)In this paper,under the catalytic effect of cobalt supported by SiO 2 and Al 2 O 3 ,CNTs are synthe-sized by MWPCVD at about 500℃,and tip-growth,the model which accounts fo r the catalytic growth of CNTs is outlined￡(r)It is the temperature difference between the upper and bottom o f the catalytic particle that results in the diffusion of carbon atoms from upper to the bottom,and precipitation of s aturated carbon on the bottom surface to form CNTs￡(r)
文摘In this paper, under the catalytic effect of nickel particles electro-deposited on Ni substrate, self-aligned carbon nanotubes were synthesized by microwave plasma chemical vapor deposition with a mixture of methane and hydrogen gases at 510 ℃. During the process of nanotubes growth, the total pressure in the chamber was kept at 3 kPa, the microwave plasma input power was 500 W, and the flow rates of H 2 and CH 4 were 50 and 1 mL/min, respectively. The aligned features and hollow structure have been verified by scanning electron and transmission electron microscopic images. As the nanotubes grow, the nickel cap remains on the tip of the carbon nanotubes. The nanotubes′diameter is about 70 nm and they have bamboo structures. Because of the strong etching ability of hydrogen plasma and the low volume ratio of H 2/CH 4, no carbonaceous particles attached to the carbon nanotubes were found. It demonstrats that MWPCVD is a very efficient process for the synthesis of the aligned carbon nanotubes at a low temperature. The aligned CNTs grown on Ni substrate at such a low temperature are suitable for device fabrication.
文摘Under the assistant effect of sulfur, carbon nanotubes electrodes were prepared on the end of tungsten strings directly through microwave plasma chemical vapor deposition. And the electrochemical behavior of CuSO4 at the carbon nanotubes electrodes was investigated. Compared to the graphite electrode, carbon nanotubes elec- trodes had better electrochemical behavior for the analysis of Cu2+. Different electrodes prepared under the same condition showed good consistency of electrochemical detection property. And because carbon nanotubes were synthesized directly on the end of tungsten strings, the results of long-term stability experiments demonstrated that the carbon nanotubes electrodes had stable response to Cu2+ solution.
