This study focused on the investigation of the edge effect of diamond films deposited by microwave plasma chemical vapor de-position.Substrate bulge height△h is a factor that affects the edge effect,and it was used t...This study focused on the investigation of the edge effect of diamond films deposited by microwave plasma chemical vapor de-position.Substrate bulge height△h is a factor that affects the edge effect,and it was used to simulate plasma and guide the diamond-film deposition experiments.Finite-element software COMSOL Multiphysics was used to construct a multiphysics(electromagnetic,plasma,and fluid heat transfer fields)coupling model based on electron collision reaction.Raman spectroscopy and scanning electron microscopy were performed to characterize the experimental growth and validate the model.The simulation results reflected the experimental trends observed.Plasma discharge at the edge of the substrate accelerated due to the increase in△h(△h=0-3 mm),and the values of electron density(n_(c)),molar concentration of H(C_(H)),and molar concentration of CH_(3)(C_(CH_(3)))doubled at the edge(for the special concave sample with△h=−1 mm,the active chemical groups exhibited a decreased molar concentration at the edge of the substrate).At=0-3 mm,a high diamond growth rate and a large diamond grain size were observed at the edge of the substrate,and their values increased with.The uniformity of film thickness decreased with.The Raman spectra of all samples revealed the first-order characteristic peak of dia-mond near 1332 cm^(−1).When△h=−1 mm,tensile stress occurred in all regions of the film.When△h=1-3 mm,all areas in the film ex-hibited compressive stress.展开更多
Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low s...Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450 ℃. The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy (SEM). The microstructure and the phase of the film have been characterized using Raman spectroscopy and X-ray diffraction (XRD). The diamond nucleation density significantly decreases with the increasing of the substrate temperature. There are only sparse nuclei when the substrate temperature is higher than 800 ℃ although the ethanol concentration in hydrogen is very high. That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450 ℃ extends into broadband indicates that the film is of nanophase. No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP3 carbon. The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.展开更多
Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results ...Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.展开更多
Nano-crystalline diamond （NCD） films were prepared on poly-crystalline diamond （PCD） thick flims by the microwave plasma enhanced chemical vapor deposition （MPCVD） method. Free standing PCD thick film （50 mm in...Nano-crystalline diamond （NCD） films were prepared on poly-crystalline diamond （PCD） thick flims by the microwave plasma enhanced chemical vapor deposition （MPCVD） method. Free standing PCD thick film （50 mm in diameter） with a thickness of 413 μm was deposited in CHn/H2 plasma. It was then abraded for 2 hours and finally cut into pieces in a size of 10×10 mm^2 by pulse laser. NCD fihns were deposited on the thick film substrates by introducing a micro-crystalline diamond （MCD） interlayer. Results showed that a higher carbon concentration （5%） and a lower substrate temperature （650℃） were feasible to obtain a highly smooth interlayer, and the appropriate addition of oxygen （2%） into the gas mixture was conducive to obtaining a smooth nano-crystalline diamond film with a tiny grain size.展开更多
Due to its unique properties such as high hardness, light transmittance, thermal conductance, chemical stability and corrosion resistance, diamond has drawn tremendous attention in last two decades. These specific pro...Due to its unique properties such as high hardness, light transmittance, thermal conductance, chemical stability and corrosion resistance, diamond has drawn tremendous attention in last two decades. These specific properties made diamond film a promising material for cutting tools, microwave windows, heat sinks for electronic devices and diamond electrodes. However, the diamond film with grain sizes at microscale usually exhibits high surface roughness and hinders its applications in the microelectro mechanical system (MEMS) and biological field because it is difficult to be polished by mechanical and chemical methods. With the development of the chemical vapor deposition, the nanocrystalline diamond (NCD) film has been fabricated and found new applications. The grain size of NCD film is in the range of 10 to 100 nm, which inherits the properties of the diamond and possesses the unique properties of the nanoscale materials, and the morphology of the NCD film is granular or needle-like structure. The microwave plasma chemical vapor deposition (MPCVD) has been regarded as the most promising method to deposit NCD film at low temperature. Compared to the hot filament CVD, MPCVD can grow high quality NCD film avoiding of the contamination from the filament materials. The MPCVD technique has high plasma density to activate carbonaceous compound and grow NCD film in high growth rate and low substrate temperature. The unique properties of NCD film, such as the superior electrical, mechanical and biological properties facilitate their application in various fields. The biological application, especially as a biocompatible coating, mainly includes the joint replacement implants and protective coatings and the ophthalmological prosthesis.展开更多
This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface ...This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface morphology and the structure of the fabricated films were characterized by using scanning electron microscopes and Raman spectroscopy, respectively. The stable field emission properties with a low threshold field of 5V/μm corresponding to a current density of about 1μA/cm^2 and a current density of 3.2mA/cm^2 at an electric field of 10V/μm were obtained from the carbon film deposited at CH4 concentration of 8%. The mechanism that the threshold field decreased with the increase of the CH4 concentration and the high emission current appeared at the high CH4 concentration was explained by using the Fowler-Nordheim theory.展开更多
Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition （MPCVD） in a gas mixture of hydrogen and methane. The structure of the fabricated films is invest...Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition （MPCVD） in a gas mixture of hydrogen and methane. The structure of the fabricated films is investigated by using field emission scanning electron microscope （FESEM） and Raman spectroscopy. These nano^carbon films are possessed of good field emission （FE） characteristics with a low threshold field of 2.6 V/μm and a high current density of 12.6 mA/cm^2 at an electric field of 9 V/μm. As the FE currents tend to be saturated in a high E region, no simple Fowler-Nordheim （F-N） model is applicable. A modified F N model considering statistic effects of FE tip structures and a space-charge-limited-current （SCLC） effect is applied successfully to explaining the FE data observed at low and high electric fields, respectively.展开更多
Using a low power microwave generator(W_(max)=100W) and a Surfatron discharge device, Plasma-polymerized copper phthalocyanine (PPCuPc) film was synthesised from monomer copper phthalocyanine(CuPc) by microwave plasma...Using a low power microwave generator(W_(max)=100W) and a Surfatron discharge device, Plasma-polymerized copper phthalocyanine (PPCuPc) film was synthesised from monomer copper phthalocyanine(CuPc) by microwave plasma chemical vaporization deposition(MPCVD) with Ar as incorporation gas. The film was characterized by FTIR and ESCA. The role of dissociation of chemical bond in the polymerization process and the influence of substrate temperature and material on deposition were investigated in some detail.展开更多
Hydrogenated amorphous carbon nitride (a-CNx:H) films were formed on p-Si, Al films deposited on n-Si (Al/n-Si) and glass (SiO2) (Al/glass) substrates, using pulsed rf supermagnetron plasma chemical vapor deposition (...Hydrogenated amorphous carbon nitride (a-CNx:H) films were formed on p-Si, Al films deposited on n-Si (Al/n-Si) and glass (SiO2) (Al/glass) substrates, using pulsed rf supermagnetron plasma chemical vapor deposition (CVD) with N2/i-C4H10 mixed gases. The rf powers (13.56 MHz) of both the upper and lower electrodes were modulated by a 2.5-kHz pulse at a duty ratio of 12.5%. N2 gas concentration was controlled at 70%. The optical band gap of a-CNx:H films was about 0.75 eV. The a-CNx:H films deposited on substrates of p-Si, Al/n-Si and Al/glass showed low threshold emission electric fields (ETH) of 10, 13 and 12 V/μm, respectively. The a-CNx:H film deposited on low-cost Al film (Al/glass) showed a sufficiently low ETH of 12 V/μm, eliminating the need for high-cost p-Si substrates.展开更多
A simple process to fabricate chain-like carbon nanotube （CNT） films by microwave plasma-enhanced chemical vapor deposition （MPCVD） was developed successfully. Prior to deposition, the Ti/Al2O3 substrates were gro...A simple process to fabricate chain-like carbon nanotube （CNT） films by microwave plasma-enhanced chemical vapor deposition （MPCVD） was developed successfully. Prior to deposition, the Ti/Al2O3 substrates were ground with Fe-doped SiO2 powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 V/μm are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.展开更多
Boron-doped nano-crystalline diamond （NCD） thin films have been successfully deposited on well-polished poly-crystalline diamond （PCD） thick films in a microwave plasma enhanced chemical vapor deposition （MPCVD）...Boron-doped nano-crystalline diamond （NCD） thin films have been successfully deposited on well-polished poly-crystalline diamond （PCD） thick films in a microwave plasma enhanced chemical vapor deposition （MPCVD） reactor for the first time. Different surface pretreatment techniques are carried out under different gas conditions （CH4, H2, Ar, and CH4/H2） to eliminate the effect of grain boundaries on the growth of a smooth NCD intrinsic layer. Well doped NCD films have been fabricated in CH4/H2/B2H6 plasma by varying the atomic ratio of B/C and the substrate temperature. Atomic force microscopy （AFM） results show that pretreatment in pure CH4 plasma at 1000℃ is most effective for NCD growth, while hydrogen containing plasma is harmful to the surface smoothness of NCD thin fihns. Doping research indicates that the optimum parameters for the boron-doping of high-quality NCD thin films are B/C=300 ppm （10-6） and 800℃.展开更多
On the sand-blasting-treated titanium（Ti） substrate, the boron-doped diamond（BDD） electrodes with a wide potential window were prepared by microwave plasma chemical vapor deposition（MPCVD）. The electrochemi- cal...On the sand-blasting-treated titanium（Ti） substrate, the boron-doped diamond（BDD） electrodes with a wide potential window were prepared by microwave plasma chemical vapor deposition（MPCVD）. The electrochemi- cal oxidation ratios of phenol at BDD/Ti electrodes at elevated temperatures（from 20 ℃ to 80 ℃） were examined by the chemical oxygen demand（COD） of phenol electrolyte during electrolysis. The results show that the COD removal was increased at high temperatures and the optimized temperature for enhancing the electrochemical oxidation ratio of phenol is 60 ℃. The mechanism for the temperature-dependent electrochemical oxidation ratios of phenol at the electrodes was investigated. The study would be favorable for further improving the performance of BDD/Ti elec- trodes, especially working at high temperatures.展开更多
This paper reports that the nano-sheet carbon films （NSCFs） were fabricated on Si wafer chips with hydrogen- methane gas mixture by means of quartz-tube-type microwave plasma chemical vapour deposition （MWPCVD）. I...This paper reports that the nano-sheet carbon films （NSCFs） were fabricated on Si wafer chips with hydrogen- methane gas mixture by means of quartz-tube-type microwave plasma chemical vapour deposition （MWPCVD）. In order to further improve the field emission （FE） characteristics, a 5-nm Au film was prepared on the samples by using electron beam evaporation. The FE properties were obviously improved due to depositing Au thin film on NSCFs. The FE current density at a macroscopic electric field, E, of 9 V/μm was increased from 12.4 mA/cm2 to 27.2 mA/cm2 and the threshold field was decreased from 2.6 V/μm to 2.0 V/μm for Au-coated carbon films. A modified F-N model considering statistic effects of FE tip structures in the low E region and a space-chavge-limited-current effect in the high E region were applied successfully to explain the FE data of the Au-coated NSCF.展开更多
Hydrogenated amorphous carbon nitride (a-CN<sub>x</sub>:H) films were formed on Al films deposited on Si or glass (SiO<sub>2</sub>) substrates, using pulsed radio frequency (PRF) supermagnetron...Hydrogenated amorphous carbon nitride (a-CN<sub>x</sub>:H) films were formed on Al films deposited on Si or glass (SiO<sub>2</sub>) substrates, using pulsed radio frequency (PRF) supermagnetron plasma (SMP) chemical vapor deposition (CVD) with N<sub>2</sub>/i-C<sub>4</sub>H<sub>10</sub> mixed gases. a-CN<sub>x</sub>:H films were grown under the upper and lower electrode RF powers (13.56 MHz) of continuous and pulsed conditions, respectively, which showed low band gap of about 0.7 eV. a-CN<sub>x</sub>:H films deposited on the Al/Si or Al/SiO<sub>2</sub> substrates showed same low threshold emission electric field (ETH) of 12 V/μm. Multiple layer of Al or ITO (anode)/50nm-SiO<sub>2</sub>/a-CN<sub>x</sub>:H/Al (cathode)/Si structures showed Fowler-Nordheim (FN) electron tunneling effect in both forward and reverse current directions. 12.5 nm a-CN<sub>x</sub>:H film on p-Si substrate showed a photoelectric conversion. Energy band structure and electron conduction models were proposed for the active states of both the field emission and FN tunneling devices and photovoltaic cells.展开更多
目的研究硅(Si)、氧(O)元素掺杂对类金刚石(Diamond like Carbon,DLC)薄膜沉积、结构、表面形貌以及阻隔性能的影响,为高效制备高阻隔硅氧共掺类金刚石(Si and O Incorporated DLC,Si/O-DLC)薄膜提供新的思路参考。方法利用微波等离子...目的研究硅(Si)、氧(O)元素掺杂对类金刚石(Diamond like Carbon,DLC)薄膜沉积、结构、表面形貌以及阻隔性能的影响,为高效制备高阻隔硅氧共掺类金刚石(Si and O Incorporated DLC,Si/O-DLC)薄膜提供新的思路参考。方法利用微波等离子体化学气相沉积(Plasma Enhanced Chemical Vapor Deposition,PECVD)技术在聚对苯二甲酸乙二醇酯(Polyethylene terephthalate,PET)基底表面沉积Si/O-DLC薄膜,具体研究反应单体中六甲基二硅氧烷(Hexaethyldisiloxane,HMDSO)含量对薄膜沉积和阻隔性能的影响。通过台阶仪、傅里叶红外光谱(FTIR)、X射线光电子能谱(XPS)、原子力显微镜(AFM)表征薄膜厚度、结构和微观形貌,并通过测试氧气透过率表征复合薄膜的阻隔性能。结果随着混合气体中HMDSO含量增加,薄膜的沉积速率提高,不同高度位置上沉积速率波动变弱,平均沉积速率最高达到310 nm·min^(–1),同时,薄膜中Si、O元素含量增加,相关的键合结构含量增加,薄膜表面致密性变差,氧气阻隔性能变弱;当HMDSO流量控制在1 mL·min^(–1)时,PET薄膜的氧气透过率可从未涂覆时的132mL·m^(2)·d^(–1)降低至2mL·m^(2)·d^(-1),阻隔性能明显改善。结论在一定工艺条件下,通过微波PECVD技术在PET薄膜表面涂覆Si/O-DLC薄膜,可明显改善其阻隔性能。展开更多
A large diamond crystal up to 500 μm in diameter with a smooth （100） facet at its top has been synthesized on Mo substrate through microwave plasma chemical vapor deposition （MPCVD）. Its morphology and quality we...A large diamond crystal up to 500 μm in diameter with a smooth （100） facet at its top has been synthesized on Mo substrate through microwave plasma chemical vapor deposition （MPCVD）. Its morphology and quality were characterized by scanning electron microscopy （SEM）, and the growth mechanism was roughly illustrated from both macroscopic and microscopic viewpoints. It was found that morphological instabilities are a major factor resulting in synthesis of large diamond crystals, moreover, high microwave power density （MPD）, high CH4 concentrations, high pressure, high substrate surface temperature and the addition of a small amount of O2 were also necessary for the synthesis of large diamond crystals.展开更多
基金supported by the National Key Research and Development Program(No.2019YFE03100200)the State Key Lab for Advanced Metals and Materials,the Fund of National Key Laboratory of Solid-State Microwave Devices and Circuits,the National Natural Science Foundation of China(No.52102034)the Or-ganized Research Fund of North China University of Tech-nology(No.2023YZZKY12).The authors are very grateful for the financial support of these institutions.
文摘This study focused on the investigation of the edge effect of diamond films deposited by microwave plasma chemical vapor de-position.Substrate bulge height△h is a factor that affects the edge effect,and it was used to simulate plasma and guide the diamond-film deposition experiments.Finite-element software COMSOL Multiphysics was used to construct a multiphysics(electromagnetic,plasma,and fluid heat transfer fields)coupling model based on electron collision reaction.Raman spectroscopy and scanning electron microscopy were performed to characterize the experimental growth and validate the model.The simulation results reflected the experimental trends observed.Plasma discharge at the edge of the substrate accelerated due to the increase in△h(△h=0-3 mm),and the values of electron density(n_(c)),molar concentration of H(C_(H)),and molar concentration of CH_(3)(C_(CH_(3)))doubled at the edge(for the special concave sample with△h=−1 mm,the active chemical groups exhibited a decreased molar concentration at the edge of the substrate).At=0-3 mm,a high diamond growth rate and a large diamond grain size were observed at the edge of the substrate,and their values increased with.The uniformity of film thickness decreased with.The Raman spectra of all samples revealed the first-order characteristic peak of dia-mond near 1332 cm^(−1).When△h=−1 mm,tensile stress occurred in all regions of the film.When△h=1-3 mm,all areas in the film ex-hibited compressive stress.
基金The project supported by the ChenGuang project of the Wuhan government (No. 20025001014)
文摘Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450 ℃. The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy (SEM). The microstructure and the phase of the film have been characterized using Raman spectroscopy and X-ray diffraction (XRD). The diamond nucleation density significantly decreases with the increasing of the substrate temperature. There are only sparse nuclei when the substrate temperature is higher than 800 ℃ although the ethanol concentration in hydrogen is very high. That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450 ℃ extends into broadband indicates that the film is of nanophase. No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP3 carbon. The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.
文摘Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.
基金supported by the Research Pund of Hubei Provincial Department of Education of China (No.Q20081505)
文摘Nano-crystalline diamond （NCD） films were prepared on poly-crystalline diamond （PCD） thick flims by the microwave plasma enhanced chemical vapor deposition （MPCVD） method. Free standing PCD thick film （50 mm in diameter） with a thickness of 413 μm was deposited in CHn/H2 plasma. It was then abraded for 2 hours and finally cut into pieces in a size of 10×10 mm^2 by pulse laser. NCD fihns were deposited on the thick film substrates by introducing a micro-crystalline diamond （MCD） interlayer. Results showed that a higher carbon concentration （5%） and a lower substrate temperature （650℃） were feasible to obtain a highly smooth interlayer, and the appropriate addition of oxygen （2%） into the gas mixture was conducive to obtaining a smooth nano-crystalline diamond film with a tiny grain size.
文摘Due to its unique properties such as high hardness, light transmittance, thermal conductance, chemical stability and corrosion resistance, diamond has drawn tremendous attention in last two decades. These specific properties made diamond film a promising material for cutting tools, microwave windows, heat sinks for electronic devices and diamond electrodes. However, the diamond film with grain sizes at microscale usually exhibits high surface roughness and hinders its applications in the microelectro mechanical system (MEMS) and biological field because it is difficult to be polished by mechanical and chemical methods. With the development of the chemical vapor deposition, the nanocrystalline diamond (NCD) film has been fabricated and found new applications. The grain size of NCD film is in the range of 10 to 100 nm, which inherits the properties of the diamond and possesses the unique properties of the nanoscale materials, and the morphology of the NCD film is granular or needle-like structure. The microwave plasma chemical vapor deposition (MPCVD) has been regarded as the most promising method to deposit NCD film at low temperature. Compared to the hot filament CVD, MPCVD can grow high quality NCD film avoiding of the contamination from the filament materials. The MPCVD technique has high plasma density to activate carbonaceous compound and grow NCD film in high growth rate and low substrate temperature. The unique properties of NCD film, such as the superior electrical, mechanical and biological properties facilitate their application in various fields. The biological application, especially as a biocompatible coating, mainly includes the joint replacement implants and protective coatings and the ophthalmological prosthesis.
文摘This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface morphology and the structure of the fabricated films were characterized by using scanning electron microscopes and Raman spectroscopy, respectively. The stable field emission properties with a low threshold field of 5V/μm corresponding to a current density of about 1μA/cm^2 and a current density of 3.2mA/cm^2 at an electric field of 10V/μm were obtained from the carbon film deposited at CH4 concentration of 8%. The mechanism that the threshold field decreased with the increase of the CH4 concentration and the high emission current appeared at the high CH4 concentration was explained by using the Fowler-Nordheim theory.
文摘Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition （MPCVD） in a gas mixture of hydrogen and methane. The structure of the fabricated films is investigated by using field emission scanning electron microscope （FESEM） and Raman spectroscopy. These nano^carbon films are possessed of good field emission （FE） characteristics with a low threshold field of 2.6 V/μm and a high current density of 12.6 mA/cm^2 at an electric field of 9 V/μm. As the FE currents tend to be saturated in a high E region, no simple Fowler-Nordheim （F-N） model is applicable. A modified F N model considering statistic effects of FE tip structures and a space-charge-limited-current （SCLC） effect is applied successfully to explaining the FE data observed at low and high electric fields, respectively.
文摘Using a low power microwave generator(W_(max)=100W) and a Surfatron discharge device, Plasma-polymerized copper phthalocyanine (PPCuPc) film was synthesised from monomer copper phthalocyanine(CuPc) by microwave plasma chemical vaporization deposition(MPCVD) with Ar as incorporation gas. The film was characterized by FTIR and ESCA. The role of dissociation of chemical bond in the polymerization process and the influence of substrate temperature and material on deposition were investigated in some detail.
文摘Hydrogenated amorphous carbon nitride (a-CNx:H) films were formed on p-Si, Al films deposited on n-Si (Al/n-Si) and glass (SiO2) (Al/glass) substrates, using pulsed rf supermagnetron plasma chemical vapor deposition (CVD) with N2/i-C4H10 mixed gases. The rf powers (13.56 MHz) of both the upper and lower electrodes were modulated by a 2.5-kHz pulse at a duty ratio of 12.5%. N2 gas concentration was controlled at 70%. The optical band gap of a-CNx:H films was about 0.75 eV. The a-CNx:H films deposited on substrates of p-Si, Al/n-Si and Al/glass showed low threshold emission electric fields (ETH) of 10, 13 and 12 V/μm, respectively. The a-CNx:H film deposited on low-cost Al film (Al/glass) showed a sufficiently low ETH of 12 V/μm, eliminating the need for high-cost p-Si substrates.
文摘A simple process to fabricate chain-like carbon nanotube （CNT） films by microwave plasma-enhanced chemical vapor deposition （MPCVD） was developed successfully. Prior to deposition, the Ti/Al2O3 substrates were ground with Fe-doped SiO2 powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 V/μm are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.
基金supported by National Natural Science Foundation of China(No.11175137)the Research Fund of Hubei Provincial Department of Education of China(No.Q20081505)the Research Fund of Wuhan Institute of Technology of China(No.11111051)
文摘Boron-doped nano-crystalline diamond （NCD） thin films have been successfully deposited on well-polished poly-crystalline diamond （PCD） thick films in a microwave plasma enhanced chemical vapor deposition （MPCVD） reactor for the first time. Different surface pretreatment techniques are carried out under different gas conditions （CH4, H2, Ar, and CH4/H2） to eliminate the effect of grain boundaries on the growth of a smooth NCD intrinsic layer. Well doped NCD films have been fabricated in CH4/H2/B2H6 plasma by varying the atomic ratio of B/C and the substrate temperature. Atomic force microscopy （AFM） results show that pretreatment in pure CH4 plasma at 1000℃ is most effective for NCD growth, while hydrogen containing plasma is harmful to the surface smoothness of NCD thin fihns. Doping research indicates that the optimum parameters for the boron-doping of high-quality NCD thin films are B/C=300 ppm （10-6） and 800℃.
基金Supported by the Project of the Development and Reform Commission in Jilin Province,China(No.2009-633)the New Century Excellent Talents in Universities of China(No.NCET-06-0303)the National Natural Science Foundation of China(No.20873051)
文摘On the sand-blasting-treated titanium（Ti） substrate, the boron-doped diamond（BDD） electrodes with a wide potential window were prepared by microwave plasma chemical vapor deposition（MPCVD）. The electrochemi- cal oxidation ratios of phenol at BDD/Ti electrodes at elevated temperatures（from 20 ℃ to 80 ℃） were examined by the chemical oxygen demand（COD） of phenol electrolyte during electrolysis. The results show that the COD removal was increased at high temperatures and the optimized temperature for enhancing the electrochemical oxidation ratio of phenol is 60 ℃. The mechanism for the temperature-dependent electrochemical oxidation ratios of phenol at the electrodes was investigated. The study would be favorable for further improving the performance of BDD/Ti elec- trodes, especially working at high temperatures.
文摘This paper reports that the nano-sheet carbon films （NSCFs） were fabricated on Si wafer chips with hydrogen- methane gas mixture by means of quartz-tube-type microwave plasma chemical vapour deposition （MWPCVD）. In order to further improve the field emission （FE） characteristics, a 5-nm Au film was prepared on the samples by using electron beam evaporation. The FE properties were obviously improved due to depositing Au thin film on NSCFs. The FE current density at a macroscopic electric field, E, of 9 V/μm was increased from 12.4 mA/cm2 to 27.2 mA/cm2 and the threshold field was decreased from 2.6 V/μm to 2.0 V/μm for Au-coated carbon films. A modified F-N model considering statistic effects of FE tip structures in the low E region and a space-chavge-limited-current effect in the high E region were applied successfully to explain the FE data of the Au-coated NSCF.
文摘Hydrogenated amorphous carbon nitride (a-CN<sub>x</sub>:H) films were formed on Al films deposited on Si or glass (SiO<sub>2</sub>) substrates, using pulsed radio frequency (PRF) supermagnetron plasma (SMP) chemical vapor deposition (CVD) with N<sub>2</sub>/i-C<sub>4</sub>H<sub>10</sub> mixed gases. a-CN<sub>x</sub>:H films were grown under the upper and lower electrode RF powers (13.56 MHz) of continuous and pulsed conditions, respectively, which showed low band gap of about 0.7 eV. a-CN<sub>x</sub>:H films deposited on the Al/Si or Al/SiO<sub>2</sub> substrates showed same low threshold emission electric field (ETH) of 12 V/μm. Multiple layer of Al or ITO (anode)/50nm-SiO<sub>2</sub>/a-CN<sub>x</sub>:H/Al (cathode)/Si structures showed Fowler-Nordheim (FN) electron tunneling effect in both forward and reverse current directions. 12.5 nm a-CN<sub>x</sub>:H film on p-Si substrate showed a photoelectric conversion. Energy band structure and electron conduction models were proposed for the active states of both the field emission and FN tunneling devices and photovoltaic cells.
基金National Natural Science Foundation of China(No.52161040)Major Science and Technology Research and Development Project of Jiangxi Province(No.20203ABC28W006)+1 种基金Natural Science Foundation of Jiangxi Province,China,(No.20202ACBL214011)Key Project of"Science and Technology to Promote Mongolian Development",China(No.XM2021BT03)。
文摘目的研究硅(Si)、氧(O)元素掺杂对类金刚石(Diamond like Carbon,DLC)薄膜沉积、结构、表面形貌以及阻隔性能的影响,为高效制备高阻隔硅氧共掺类金刚石(Si and O Incorporated DLC,Si/O-DLC)薄膜提供新的思路参考。方法利用微波等离子体化学气相沉积(Plasma Enhanced Chemical Vapor Deposition,PECVD)技术在聚对苯二甲酸乙二醇酯(Polyethylene terephthalate,PET)基底表面沉积Si/O-DLC薄膜,具体研究反应单体中六甲基二硅氧烷(Hexaethyldisiloxane,HMDSO)含量对薄膜沉积和阻隔性能的影响。通过台阶仪、傅里叶红外光谱(FTIR)、X射线光电子能谱(XPS)、原子力显微镜(AFM)表征薄膜厚度、结构和微观形貌,并通过测试氧气透过率表征复合薄膜的阻隔性能。结果随着混合气体中HMDSO含量增加,薄膜的沉积速率提高,不同高度位置上沉积速率波动变弱,平均沉积速率最高达到310 nm·min^(–1),同时,薄膜中Si、O元素含量增加,相关的键合结构含量增加,薄膜表面致密性变差,氧气阻隔性能变弱;当HMDSO流量控制在1 mL·min^(–1)时,PET薄膜的氧气透过率可从未涂覆时的132mL·m^(2)·d^(–1)降低至2mL·m^(2)·d^(-1),阻隔性能明显改善。结论在一定工艺条件下,通过微波PECVD技术在PET薄膜表面涂覆Si/O-DLC薄膜,可明显改善其阻隔性能。
基金supported by National Natural Science Foundation of China(No.11175137)
文摘A large diamond crystal up to 500 μm in diameter with a smooth （100） facet at its top has been synthesized on Mo substrate through microwave plasma chemical vapor deposition （MPCVD）. Its morphology and quality were characterized by scanning electron microscopy （SEM）, and the growth mechanism was roughly illustrated from both macroscopic and microscopic viewpoints. It was found that morphological instabilities are a major factor resulting in synthesis of large diamond crystals, moreover, high microwave power density （MPD）, high CH4 concentrations, high pressure, high substrate surface temperature and the addition of a small amount of O2 were also necessary for the synthesis of large diamond crystals.
