Deposition of Diamond Films on Copper Substrate

1.IntroductionThedeposltlonofdiamondfilmsoncopperhasmanyapplicationsinelectronicindustry.Coppercanbeusedasheatsinksforitshighthermalconduc-tivlty,howeverthethermalconductlvltyofdiamond(upto2Ow/cm'k)isgreatlyhigherthanthatofcopperandsodiamondisamuchbettermaterialforheatslnk.Thethermaldlffusionabilityofthecopperasheatsinkswouldbelargelyimprovedlfadiamondfilmwithathicknessofseveralmicrom-etersweredepositedonacoppersubstrate.Addl-tionally,thepropertlesofthediamondthatmakeitparticularlyattractivef…     

Growth of Free-Standing Diamond Films on Stainless Steel

Free-standing diamond films have been successfully deposited on stainless steel substrates using microwave plasma-assisted chemical vapor deposition. Although iron, which is the main element of stainless steel, is known to inhibit the nucleation of diamond and enhance the formation of graphite, we were able to grow relatively thick films （-1.2 mm）. The films were easily detachable from the substrates. The poor adhesion made it possible to obtain free-standing diamond films without chemical etching. Raman spectroscopy showed the 1332 cm^-1 characteristic Raman peak of diamond and the 1580 cm^-1, 1350 cm^-1 bands of graphite on the growth surface and backside of the films, respectively. By energy dispersive X-ray spectroscopy it was only possible to detect iron on the back of the films, but not on the surface. The role of iron in the film growth is discussed.     

Plasma-Etching Enhanced Mechanical Polishing for CVD Diamond Films

Chemically vapor deposited diamond films were etched at different parameters using oxygen plasma produced by a DC （direct current） glow discharge and then polished by a modified mechanical polishing device. Scanning electron microscope, atomic force microscope and Raman spectrometer were used to evaluate the surface states of diamond films before and after polishing. It was found that a moderate plasma etching would produce a lot of etch pits and amorphous carbon on the top surface of diamond film. As a result, the quality and the efficiency of mechanical polishing have been enhanced remarkably.     

Structural and Electrical Properties of Sulfur-Doped Diamond Thin Films

We report our observations on the higher carrier mobility and higher conductivity of sulfur-doped n-type diamond thin films synthesized by the hot filament chemical vapor deposi- tion （HFCVD）. The structural and electrical characterizations of the films are measured by X-ray diffraction （XRD）, Raman spectroscopy, scanning electron microscope （SEM）, energy dispersion X-ray spectra （EDX）, and Hall effect measurements. It is found that the sulfur atoms are in- corporated into the polycrystalline diamond films. The n-type conductivity of the films increases with the H2S concentration, and a conductivity of the films as high as 1.82 ~-l.cm-1 is achieved. The results show that the sulfur atom plays an important role in the structural and electrical properties of sulfur-doped diamond thin films.     

Influence of Microwave Power Supply on the Quality ofMWPCVD Diamond Films

1.IntroductionBecauseofitsadmirableproperties,diamondhasmanypotentialapplicatlonsinthefieldsofmechan-ics,electronlcs,optics,astronautics,etc[1,2].Withsomanyadvantagessuchasnocontaminationfromtheelectrodematerials,highadaptabilitytothesub-strateshapeandhighqualityofthedepositedfilms,themicrowaveplasmaenhancedchemicalvaporde-position(MWPCVD)methodasanoveltechnlqueforthepreparationofthinfilmhasbeenextensivelyusedforthestudyonthelowtemperature,lowpres-surechenucalvapordeposition(CVD)ofdiamondfi…     

Effects of Surface Pretreatment on Nucleation and Growth of Ultra-Nanocrystalline Diamond Films

The effects of different surface pretreatment methods on the nucleation and growth of ultra-nanocrystalline diamond(UNCD) films grown from focused microwave Ar/CH_4/H_2(argonrich) plasma were systematically studied.The surface roughness,nucleation density,microstructure,and crystallinity of the obtained UNCD films were characterized by atomic force microscope(AFM),scanning electron microscopy(SEM),X-ray diffraction(XRD),and Raman spectroscopy.The results indicate that the nucleation enhancement was found to be sensitive to the different surface pretreatment methods,and a higher initial nucleation density leads to highly smooth UNCD films.When the silicon substrate was pretreated by a two-step method,i.e.,plasma treatment followed by ultrasonic vibration with diamond nanopowder,the grain size of the UNCD films was greatly decreased:about 7.5 nm can be achieved.In addition,the grain size of UNCD films depends on the substrate pretreatment methods and roughness,which indicates that the surface of substrate profile has a "genetic characteristic".     

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.     

氢气流量对类金刚石薄膜结构与性能的影响

采用直流/射频耦合反应磁控溅射法在Si（100）衬底上成功制备出类金刚石（DLC）薄膜。利用表面轮廓仪、Raman光谱仪、X射线光电子能谱仪表征所制备薄膜在不同氢气流量下的沉积速率和化学结构,讨论了氢气流量对薄膜沉积速率和化学结构的影响;利用纳米压痕技术及曲率弯曲法表征薄膜的力学性能;利用扫描电镜和原子力显微镜表征薄膜的表面形貌与粗糙度。研究表明：随着氢气流量的增加,所制备薄膜的沉积速率逐渐减小,而薄膜中sp³键的含量逐渐增大。当氢气流量为25 mL/min时,薄膜中sp³键的含量为36.3%,薄膜的硬度和体弹性模量分别达到最大值17.5 GPa和137 GPa。同时,所制备薄膜的内应力均低于0.5 GPa,有望成功制备出低内应力的高质量DLC厚膜。随着氢气流量的增加,DLC薄膜的表面变得更致密光滑,且表面均方根粗糙度由5.40 nm降为1.46 nm。     

Characterization of Diamond: Like Carbon Films Synthesized by DC-Plasma Enhanced Chemical Vapor Deposition

In this paper, diamond-like carbons were produced on tungsten and aluminum substrates by DC plasma enhanced chemical vapor deposition (DC-PECVD) system in a C₂H₂/H₂ gas mixture using C₂H₂ as source hydrocarbon and H₂ as etching and diluting gas. The operation pressure during the growth and substrates temperature were 15 Torr and 180°C, respectively. Characterization of the DLCs deposited on tungsten and aluminum substrates were carried out by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Raman spectroscopy and Atomic force microscopy (AFM). AFM analysis displayed that the DLCs grown on W substrate has lower roughness than the DLCs deposited on Al substrate and it was smoother. FTIR analysis indicates the existence of C–H vibration mode in the DLCs grown on both of substrates. The Raman spectroscopy shows G peak position and I(D)/I (G) ratio decreased for the DLCs grown on W substrate. The SEM images show diffuse and dense distribution of DLCs in Al and W substrate, respectively. These results shows that the optimum conditions were obtained on W substrate.     

Microwave Plasma Chemical Vapor Deposition of Diamond Films on Silicon From Ethanol and Hydrogen

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 broadban indicates that the film is of nanophase.No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP^3 carbon.The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.     

Effect of Argon Addition on Morphology and Structure of Diamond Films(from Microcrystalline to Nanocrystalline)

Micro-/nanocrystalline diamond films deposited in Ar/H_2/CE_4 microwave plasmas have been studied,with argon flow rates in the range of 70-100 seem.The effects of argon addition on morphology,surface roughness,quality and structure were investigated by scanning electron microscopy,surface profiler,Raman spectrometer and X-ray diffraction(XRD).It is demonstrated that when the argon flow rate is 70 sccm or 75 sccm,well-faceted polycrystalline diamond films can be grown at a low substrate temperature less than 610 ℃.With the increase in the argon flow rate,the smooth crystallographic planes disappear gradually.Instead,rough crystallographic planes made up of small aggregates begin to take shape,resulting from the increase in the secondary nucleation rate.Nanocrystalline diamond films were obtained at a flow rate of 100 sccm,and all of the prepared diamond films were smooth,with a surface roughness(Ra) less than 20 nm.Raman analyses reveal that the amount of amorphous carbon increases significantly with the increase in argon flow.The results of XRD show that crystalline size and preferential orientation of diamond films depend on the argon content in the plasmas.     

Effect of Gas Sources on the Deposition of Nano-Crystalline Diamond Films Prepared by Microwave Plasma Enhanced Chemical Vapor Deposition

Nano-crystalline diamond (NCD) films were deposited on silicon substrates by a microwave plasma enhanced chemical vapor deposition (MPCVD) reactor in C2H5OH/H2 and CH4/H2/O2 systems, respectively, with a constant ratio of carbon/hydrogen/oxygen. By means of atomic force microscopy (AFM) and X-ray diffraction (XRD), it was shown that the NCD films deposited in the C2H5OH/H2 system possesses more uniform surface than that deposited in the CH4/H2/O2 system. Results from micro-Raman spectroscopy revealed that the quality of the NCD films was different even though the plasmas in the two systems contain exactly the same proportion of elements. In order to explain this phenomenon, the bond energy of forming OH groups, energy distraction in plasma and the deposition process of NCD films were studied. The experimental results and discussion indicate that for a same ratio of carbon/hydrogen/oxygen, the C2H5OH/H2 plasma was beneficial to deposit high quality NCD films with smaller average grain size and lower surface roughness.     

The Effect of Pressure on the Dissociation of H2／CH4 Gas Mixture during Diamond Films Growth via Chemical Vapor Deposition

Monte Carlo simulations are adopted to study the electron motion in mixture of H2 and CH4 duruing diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD),The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation.The average energy distribution of electrons and the space distribution of effective species such as CH3,CH3^ ,CH^ and H at various gas pressures are given in this paper,and optimum experimental conditions are inferred from these results.     

用于X射线探测的CVD金刚石薄膜探测器

研制了用于X射线测量的化学气相沉积(CVD)金刚石薄膜探测器.该探测器灵敏区直径为15 mm、厚度300 μm,其暗电流在800 V偏压下小于50 pA,且暗电流-电压曲线线性较好.就CVD金刚石探测器对不同能量X射线的响应及脉冲X射线时间响应进行了理论和实验研究.结果表明:该探测器对6～22 keV X射线具有10-4～10-2A·W-1的灵敏度,假设电荷收集效率为39%时,灵敏度的理论值与实验测量值符合较好,探测器的RC时间常数约为1.5 ns;对亚纳秒脉冲X射线的响应上升时间为2～3 ns.     

CVD金刚石核探测材料与器件

金刚石膜因其优异的电学、光学等性能已成为优越的辐射探测器材料,但探测器性能强烈地依赖于薄膜质量.本工作利用热丝化学气相沉积(HFCVD)法获得了 (100)取向不同质量的金刚石薄膜,并制备了CVD金刚石辐射探测器.应用5.9 keV 55Fe X射线测试了探测器的光电流响应和脉冲高度分布.50 kV/cm外电场作用下晶粒为10 μm的CVD金刚石探测器的暗电流和光电流分别为16.3和16.8 nA.光电流随辐照时间延长而增大,尔后趋于稳定.脉冲高度峰与噪声明显分离.探测器具有较高的计数效率和信噪比.     

Carbon carbon detection: Diamond detectors and AMS

¹⁴C ions (290 keV) have been detected with chemically vapour deposited diamond. Potential benefits of diamond detectors are radiation hardness, high charge collection and very fast response time/high bandwidth.     

Electronic Transport in Insulating Films

This paper gives a brief review of various electronic transport processes in insulating films. The topics include a brief consideration of energy bands and the concepts of extended and localized states; the properties of traps with emphasis on Shockley-Reed theory; the space-charge limitation of currents for one-carrier injection; the bulk trap limitation of currents including hopping conduction, the Poole-Frenkel effect, and field emission from traps; and ionic conduction.