Relationship Between Thermal Stability and Optical Bandgap of Fluorinated Amorphous Carbon Films

1. IntroductionWith the requirement of decreasing feature dimen-.sions and increasing device packing density for uLtralarge scale integration (ULSI) circuits, low dielec-tric materials have been often used as insulator lnyersbetween metal lines to reduce parasitic capacitance.Fluorinated amorphous carbon film (aC:F) has nowbeen one of the main candidate materials due toits good electric properties and mechanical perfor-manc e[l, 2, 3]. FOr the characterization of aC:F film,much attention h…     

Sheet Resistance and Gas-Sensing Properties of Tin Oxide ThinFilms by Plasma Enhanced Chemical Vapor Deposition＊

Tin oxide (SnO2) thin films are prepared at different temperatures by plasmaenhanced chemical vapor deposition (PECVD). The structural characterizations of the films are investigated by various analysis techniques. X-ray diffraction patterns (XRD) show that the phase of SnO2 films are different at different deposition temperatures. The sheet resistance of the films decreases with increase of deposition temperature. X-ray photoelectron spectroscopy (XPS) shows that the SnO2 thin film is non-stoichiometric. The sheet resistance increases with increase in oxygen flow. Sb-doped SnO2 thin films are more sensitive to alcohol than carbon monoxide, and its maximum sensitivity is about 220％.     

Growth of 4" diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters,and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230-380 K.The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra.Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples,respectively.TC,as high as 1950 ± 230 W m-1 K-1 at room temperature,is measured for the most perfect material.A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.     

On the use of MWCVD diamond as thermoluminescent gamma dosimeter

The thermoluminescence (TL) characterization of microwave plasma assisted chemical vapor deposition diamond (MWCVD) films of 6 and 12 μm thickness grown on (1 0 0) silicon substrates was performed. The films exhibited a single well-resolved TL peak around 580 K at doses lower than 40 Gy. As the irradiation dose increased the TL peak broaden and shifted towards the low temperature side of the glow curve. The diamond samples exposed to 0.67 Gy/min ⁶⁰Co gamma radiation displayed a linear dose behavior up to 100 Gy being non-linear for higher doses. The 12 μm film showed lower TL efficiency as compared to the 6 μm specimen. The discrepancy was attributed to the non-uniform distribution of nucleated sp³ diamond and sp² bonded carbon on the substrate as revealed by SEM micrograph and Raman spectroscopy of the samples. The integrated TL glow curve of the samples exhibited low room temperature thermal fading and 3% reproducibility. The results show that MWCVD diamond films possess promising properties for radiation dosimetry applications.     

The effect of temperature on the structure of tantalum nitride (TaN) thin films deposited by DC plasma

In this work, we report the effect of growth temperature (room temperature, 150, 200 and 250°C) during the deposition of tantalum nitride thin films by a reactive planar DC magnetron sputtering system on the steel substrates, in a constant nitrogen partial pressure of 15% has been studied. The X-ray spectrum of deposited tantalum nitride films indicated an increasing in intensity of sharp peak of hexagonal TaN and was evidence of grain growth at higher temperatures. By increasing temperature the streaks’ directions, observed from AFM micrographs, were varied.     

Optical Characterization of Diamond Synthesis Using CH3OH-H2 Gas Mixtures

Diamond films with high infrared transmittance have been successfully deposited using CH3OH-H2 gas mixtures through microwave plasma enhanced chemical vapor deposition (MWCVD). The primary purpose of this study is to determine the effect of the deposition conditions on the optical properties of MWCVD diamond films using CH3OH-H2 gas mixtures. Room temperature optical properties of freestanding diamond films were studied by Fourier transform IR spectroscopy. Experimental results indicated that under appropriate deposition temperature (620 ℃) and methanol concentration (5.7%), the refractive index of CVD diamond films (2.33) was comparable with that of natural diamond (2.417). The average infrared transmittance was above 65% in the middle infrared region (500 cm^-1 - 4000 cm^-1), approaching to the theoretical value of diamond (71.4%). The mechanism of growing high IR transmittance diamond films by utilizing CH3OH-H2 gas system is that the high methanol concentration used in this study makes the surface roughness of diamond films decreased by increasing the secondary nucleation density and the high O/C ratio in CH3OH-H2 gas system, improved the quality of diamond films and therefore decreased the absorption of non-diamond carbon in the films.     

RBS investigations of buffer layers between YBa2Cu3O7−x and silicon

The deposition of high-quality high-T_c superconducting films on silicon wafers for future hybrid electronic devices is strongly hampered by the interdiffusion between films and substrate. This effect degrades the superconducting properties seriously and is a strong function of temperature. Since high processing temperatures are inevitable for good films, suitable buffer layers are needed to reduce the interdiffusion. We have investigated the combinations ZrO₂/Si(100), BaF₂/Si(100), and noble-metal/TiN/Si(100) at temperatures up to 780°C in oxidizing ambient. YBa₂Cu₃O_7−x films have been deposited onto the buffer layers by laser ablation. Thereafter the interfaces have been analyzed by Rutherford backscattering. So far only ZrO₂ has demonstrated sufficient stability to serve as a buffer layer for the laser-ablated YBa₂Cu₃O_7−x films. All other combinations suffer from interdiffusion or oxidation.     

Mechanism of high growth rate for diamond-like carbon films synthesized by helicon wave plasma chemical vapor deposition

A high growth rate fabrication of diamond-like carbon(DLC)films at room temperature was achieved by helicon wave plasma chemical vapor deposition(HWP-CVD)using Ar/CH_4gas mixtures.The microstructure and morphology of the films were characterized by Raman spectroscopy and scanning electron microscopy.The diagnosis of plasma excited by a helicon wave was measured by optical emission spectroscopy and a Langmuir probe.The mechanism of high growth rate fabrication for DLC films by HWP-CVD has been discussed.The growth rate of the DLC films reaches a maximum value of 54μm h~(-1)at the CH_4flow rate of 85 sccm,which is attributed to the higher plasma density during the helicon wave plasma discharge.The CH and H_αradicals play an important role in the growth of DLC films.The results show that the H_αradicals are beneficial to the formation and stabilization of C=C bond from sp~2to sp~3.     

Characterization and dielectric properties of GeOx thin films prepared by radio frequency (RF) reactive sputtering

Dielectric properties of germanium oxide have not been investigated in detail. But, it has been investigated from an optical viewpoint as light waveguide materials. Its electrical properties have rarely been studied for electronic device applications.We have examined the previous investigations on Ge-O films deposited by radio frequency (RF) reactive sputtering. The dissipation factor tan δ, the capacitance per area, the breakdown field of GeO_x films were studied as well as its composition by RBS analysis. Aiming at obtaining the higher value of the dielectric constant or capacitance per area, we have attempted to fabricate Ge-Pb-O films by the same deposition method. An optimization of the dielectric properties of these materials has been done, using the best conditions of sputtering for each oxide, the alternated pile layers as dielectric multilayer capacitors and thermal treatments.These dielectric properties have been improved by thermal treatments, and the dielectric multilayer made with alternated GeO₂ and Ge-Pb-O films capacitors has a breakdown field superior to that of each simple layer.     

基于单一气源的PECVD方法制备SiC薄膜及其微观结构研究

为制备出满足惯性约束聚变（ICF）实验要求的SiC薄膜,本文采用等离子体增强化学气相沉积（PECVD）法,以四甲基硅（TMS）作为唯一反应气源,在不同工作压强下制备SiC薄膜。利用扫描电子显微镜、表面轮廓仪、原子力显微镜、精密电子天平、X射线光电子能谱、傅里叶变换红外光谱对薄膜进行表征与分析。结果表明：SiC薄膜的成分与工作压强密切相关,随着工作压强的增加,薄膜中Si含量整体呈下降趋势;随着工作压强的增加,薄膜沉积速率先增大后减少,密度先减小后增大;与其他制备工艺相比,采用单一气源制备SiC薄膜,其表面粗糙度极低（1.25～1.85 nm）,薄膜粗糙度随工作压强的增加呈先增大后减小的趋势。     

Atomic layer deposition of copper thin film and feasibility of deposition on inner walls of waveguides

Copper thin films were deposited by plasma-enhanced atomic layer deposition at low temperature, using copper(I)-N,N′-di-sec-butylacetamidinate as a precursor and hydrogen as a reductive gas. The influence of temperature, plasma power, mode of plasma, and pulse time, on the deposition rate of copper thin film, the purity of the film and the step coverage were studied.The feasibility of copper film deposition on the inner wall of a carbon fibre reinforced plastic waveguide with high aspect ratio was also studied. The morphology and composition of the thin film were studied by atomic force microscopy and x-ray photoelectron spectroscopy,respectively. The square resistance of the thin film was also tested by a four-probe technique. On the basis of on-line diagnosis, a growth mechanism of copper thin film was put forward, and it was considered that surface functional group played an important role in the process of nucleation and in determining the properties of thin films. A high density of plasma and high free-radical content were helpful for the deposition of copper thin films.     

Polymer thermal protection induced by ion beam irradiation

The thermal stability of F, Ne, He, and B implanted/irradiated AZ1350-J photoresist films has been investigated via the Rutherford backscattering (RBS) technique. We find that both shallow and deep implantations raise the temperature at which the photoresist starts to decompose (from 400°C to 450°C). It is shown that radiation rather than chemical effects are responsible for the improvement in the thermal behavior of the implanted/irradiated films. In addition it is observed that the deep implantations give better results as compared with the shallow ones. In fact after a high energy Ne, B or He irradiation fluence was reached, no material loss was observed when the samples were further submitted to 450°C annealings. This is at variance with what was observed with shallow F and Ne implantations, where only partial protection was achieved.     

Determination of stoichiometry in silicon carbide materials using elastic backscattering spectrometry

Elastic backscattering spectrometry (EBS) was performed on SiC materials, using ⁴He particles at energies ranging from 2 to 4 MeV, in order to establish the energy values that lead to an accurate measurement of the Si/C ratio. Analysis of the random yield of “bulk” SiC single crystals indicates that energy values of 3.25 and 3.75 MeV are the most suitable for chemical composition determination; backscattering yield of carbon is enhanced compared to the yield measured at 2 MeV, while the excitation of strong resonances above 3.75 MeV are suppressed. Random backscattering yield measurements were then carried out at an energy of 3.25 MeV on unhydrogenated SiC thin films grown on Si(1 0 0), by pulsed laser deposition, at different substrate temperatures. The Si and C atomic concentrations in the films were determined with an uncertainty of 1% and little interference from the underlying substrate. The films were found to be stoichiometric with a Si/C ratio of 1.03 ± 0.05, independent of deposition temperature, which indicates that the films were grown under congruent ablation conditions. The analysis proved to be applicable to both amorphous and crystalline SiC layers, as confirmed by the results obtained for films deposited at 400 and 950 °C, respectively.     

铀上激光辅助化学气相沉积镍薄膜研究

为防止金属铀的腐蚀,本文采用激光辅助化学气相沉积(LACVD)方法在铀上制备了镍薄膜。采用SEM、XRD分析了薄膜的形貌、物相以及界面特性,采用黏胶拉伸测试表征了膜-基结合性能,采用电化学极化法分析了薄膜的抗腐蚀性能。结果表明:压力和温度对化学气相沉积(CVD)方法制备镍薄膜的质量有较大的影响。随着基底温度和沉积气压的降低,薄膜变得致密、平整,质量提高。在优化的工艺条件165℃、3Pa下,CVD方法所得镍薄膜非常致密。采用LACVD方法时,激光能量为200mJ时所制得的薄膜致密,300mJ时膜变得粗糙。无激光辅助时,CVD方法所制得的薄膜较易剥落,激光辅助下所得薄膜的膜-基结合力较好。LACVD方法大幅提高了薄膜的抗腐蚀性能,抗腐蚀性能的提高主要源于激光辅助使薄膜致密化,提高了薄膜与基底的结合力。     

Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

Boron-doped nanocrystalline diamond(NCD) exhibits extraordinary mechanical properties and chemical stability,making it highly suitable for biomedical applications.For implant materials,the impact of boron-doped NCD films on the character of cell growth(i.e.,adhesion,proliferation) is very important.Boron-doped NCD films with resistivity of 10~(-2)Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition(MPCVD) process with H_2 bubbled B_2O_3.The crystal structure,diamond character,surface morphology,and surface roughness of the boron-doped NCD films were analyzed using different characterization methods,such as X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and atomic force microscopy(AFM).The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope(SKFM).The cytotoxicity of films was studied by in vitro tests,including fluorescence microscopy,SEM and MTT assay.Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates.MG-63 cells adhered well and exhibited a significant growth on the surface of films,suggesting that the boron-doped NCD films were non-toxic to cells.     

PET薄膜中32S离子径迹的热退火效应

采用径迹蚀刻的方法研究了热处理对聚对苯二甲酸乙二醇酯（PET）薄膜中重离子径迹的热退火效应。使用113.7 MeV的³²S离子在PET薄膜中产生垂直于表面且贯穿薄膜的离子径迹。对薄膜进行局部热处理，加热温度为70～240 ℃，时间为1～300 s。薄膜经过化学蚀刻成核孔膜后使用显微镜观测。结果表明：在相同的热处理时间下，随着热处理温度的升高，PET薄膜中离子径迹的热退火效应愈加明显；在热处理温度不变的情况下，随着热处理时间的增加，退火效应亦愈加明显。     

Fabrication and characterization of iron and iron carbide thin films by plasma enhanced pulsed chemical vapor deposition

A new pulsed chemical vapor deposition(PCVD) process has been developed to fabricate iron(Fe) and iron carbide(Fe_(1-x)C_x) thin films at low temperature range from 150 ℃ to 230 ℃.The process employs bis(1,4-di-tert-butyl-1,3-diazabutadienyl)iron(Ⅱ) as iron source and hydrogen gas or hydrogen plasma as the coreactant.The films deposited with hydrogen gas are demonstrated polycrystalline with body-centered cubic Fe.However,for the films deposited with hydrogen plasma,the amorphous phase of iron carbide is obtained.The influence of the deposition temperature on iron and iron carbide characteristics have been investigated.     

Thermal analysis of toroidal field coil in EAST at 3.7 K

The thermal performance of toroidal field (TF) coil is studied at 3.7 K in Experimental Advanced Superconducting Tokamak device (EAST) to obtain the higher stability for the higher plasma parameters operation. It is a good way to lower the operating temperature of TF coil to acquire the higher stability margin. This paper describes the structure and cooling process design of TF coil and case firstly. Based on the thermal load in the case, the thermal performance of the TF coil is performed at the plasma disruption state. The helium temperature in the cable-in-conduit conductor (CICC) and case is evaluated during the 1.5 MA plasma disruptions. Then, the experimental results of TF coil which has been cooled at 3.7 K and discharged in 10 kA are shown including the thermal loss evaluation. Finally, the thermal stability performance of TF coil is analyzed according to the 3.7 K experimental results and the stability prediction is performed at 1.5 MA plasma current operations.     

Influence of additional UV-light illumination on preparation of TiN by ion beam assisted deposition

Titanium nitride films were prepared by a newly developed photon and ion beam assisted deposition system at room temperature. Titanium was deposited on Si(111) in a controlled nitrogen environment and simultaneously bombarded with low-energy N ions or illuminated with UV-light. The influence of UV-light illumination during deposition is compared with the influence of ion bombardment on film properties like structure, topography and composition, measured by XRD, AFM and ERD, respectively. The results demonstrate that photon assisted deposition (PHAD) is also a good method to modify film characteristics like ion beam assisted deposition (IBAD).     

高温超导外延薄膜YBα_2Cu_3O_(7-x)中空位型缺陷的低能正电子寿命研究

利用脉冲低能正电子束系统测量了脉冲激光沉积法、磁控溅射法和多源共蒸法制备的高温超导外延薄膜ＹＢａ２Ｃｕ３Ｏ７－ｘ的低能正电子寿命谱。结果表明。除块材中普遍存在的正电子浅捕获中心外，还大量含有块材中缺乏的正电子探捕获中心，并且其尺度随温度的降低而长大。脉冲激光沉积法制备高温超导外延薄膜ＹＢａ２Ｃｕ３Ｏ７－ｘ的正电子寿命和沉积条件（衬底温度及空气分压）的关系研究表明，这种深捕获缺陷的种类与沉积条件无关，而缺陷浓度随衬底温度的降低及空气分压增高而增加