Enhanced diamond nucleation on copper substrates by graphite seeding and CO2 laser irradiation

Diamond nucleation on copper (Cu) substrates was investigated by graphite seeding and CO₂ laser irradiation at initial stages of the combustion-flame deposition. A graphite aerosol spray was used to generate a thin layer of graphite powders (less than 1 μm) on Cu substrates. The graphite-seeded Cu substrates were then heated by a continuous CO₂ laser to about 750 °C within 1 min. It was found that diamond nucleation density after this treatment was more than three times as much as that on the virgin Cu substrates. As a consequence, diamond films up to 4 μm were obtained in 5 min. The enhancement of diamond nucleation on the graphite-seeded Cu substrates was attributed to the formation of defects and edges during the etching of the seeding graphite layers by the OH radicals in the flame. The defects and edges served as nucleation sites for diamond formation. The function of the CO₂ laser was to rapidly heat the deposition areas to create a favorable temperature for diamond nucleation and growth.     

Optical and Electrical Properties Evolution of Diamond-Like Carbon Thin Films with Deposition Temperature

Optical and electrical properties of diamond-like carbon （DLC） films deposited by pulsed laser ablation of graphite target at different substrate temperatures are reported. By varying the deposition temperature from 400 to 25℃, the film optical transparency and electrical resistivity increase severely. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting the deposition temperature, which is critical to many applications. DLC films deposited at low temperatures show excellent optical transmittance and high resistivity. Over the same temperature regime an increase of the spa bonded C content is observed using visible Raman spectroscopy, which is responsible for the enhanced transparency and resistivity properties.     

193-nm laser ablation of CVD diamond and graphite in vacuum: plume analysis and film properties

The pulsed laser ablation of chemical vapor deposition (CVD) diamond and graphite samples in vacuum has been investigated by the use of an ArF excimer laser operating at 5=193 nm. The composition and propagation of both ablation plumes has been probed via wavelength and spatially and temporally resolved measurements of the plume emission and found to be very similar. Electronically excited C atoms and C⁺ and C²⁺ ions are identified among the ablated material. Plume expansion velocities are estimated from time-gated imaging of specific C and C⁺ emissions. Langmuir probe measurements provide further insight into the propagation of the charged components in both ablation plumes. Diamond-like carbon (DLC) films grown by 193-nm laser ablation of both target materials on Si substrates maintained at room temperature have been investigated by laser Raman spectroscopy (325 nm and 488 nm excitation) and by both optical and scanning electron microscopy, and their field emission characteristics investigated. Again, similarities outweigh the differences, but DLC films grown from ablation of the diamond target appear to show steeper I/V dependencies once above the threshold voltage for field emission.     

Nitrogen-Doped Chemical Vapour Deposited Diamond： a New Material for Room-Temperature Solid State Maser

Electron spin resonance （ESR） in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 10^18 cm^-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 （nitrogen impurity atom occupying C site in diamond lattice） is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.     

Short-pulse laser deposition of diamond-like carbon thin films

The high intensities present in and the non-thermal nature of ultrashort-pulse laser ablation provide a nearly ideal source for thin-film deposition. The high kinetic energies and high ion content in the ablation plume suggest that it would be useful for the creation of diamond thin films. We used a 120 fs, 3 W, 1 kHz laser to ablate a graphite target and characterized the resulting films. We were able to grow amorphous films of up to 18 7m thick and free from graphite particulates with no annealing necessary and at rates up to 25 7m/hr. The films had 40-50% sp³ bonds as measured by using EELS and had properties typical of PLD-generated diamond-like carbon films.     

热丝CVD生长金刚石薄膜喇曼散射研究

本文报道热丝化学气相沉积法（ＨＦＣＶＤ）生长金钢石薄膜的喇曼散射结果。选取多种峰型，对金钢石薄膜喇曼谱（１１０－１８００ｃｍ－１）采用最小二乘法进行非线性拟合，得到最佳拟合模型，其计算得到的拟合曲线怀实验谱图符合得较好。该模型揭示，石墨Ｄ峰（１３５５ｃｍ－１）是金刚石薄膜喇曼谱中不可缺少的一个组份，并且结合石墨Ｄ峰和金刚石喇曼的空间相关线型，可以解释金刚石喇曼区特殊峰形的物理机制，拟合参量的进一步     

Highly Strained Si Films with Ultra-low Dislocation Density Grown on Virtual Substrates of Thin Thickness

By using compositionally graded SiGe films as virtual substrates, tensile strained Si films with the strain of 1.5% and the threading dislocation density less than 1.0 × 10^5 cm-2 are successfully grown in micron size windows by molecular beam epitaxy （MBE）. The thickness of the virtual substrates was only 33Onto. On the surface of the s-Si films no cross-hatched lines resulting from misfit dislocations could be observed. We attribute these results to the edge-induced strain relaxation of the epitaxial films in windows, and the patterned virtual substrates with compositionally graded SiGe films.     

Electroless deposition of copper and fabrication of copper micropatterns on CVD diamond film surfaces

Electroless deposition of copper on as-grown and amino-modification diamond substrates was investigated. The compact and uniform copper films were successfully electrolessly deposited on as-grown and amino-modification diamond substrates after activation by Pd/Sn colloid nanoparticles. The adhesion interaction between copper films and diamond substrates was roughly estimated by the ultrasonic treatment. The results showed the higher adhesion interaction between copper films and amino-modification diamond substrates than that between the copper films and as-grown diamond substrates due to the greater attractive force between the Pd/Sn colloid nanoparticles and amino-modified diamond surface. The favorable copper micropatterns were successfully constructed on diamond film surfaces by means of the catalyst lift-off method and the copper lift-off method. Furthermore, the electrochemical behavior of copper-modified boron-doped diamond (BDD) was studied for glucose oxidation in 0.2 M sodium hydroxide solution by using cyclic voltammetry, and the result indicated that copper-modified BDD exhibited high catalytic activity to electrochemical oxidation of glucose in alkaline media.     

Comparison of diamond film adhesion on molybdenum substrates with different surface morphologies

To evaluate the effect of substrate morphology on the adhesion of diamond film, two types of substrate morphology of molybdenum (Mo) were compared. The two morphology types were formed by polishing a Mo substrate with SiC abrasive paper along one direction (anisotropic morphology) and by polishing the Mo substrate with diamond powder in a random direction (isotropic morphology).Ultrasonic cavitation tests were conducted to evaluate the adhesion of the diamond films on these Mo substrates. In the case of low surface roughness, there was very little difference between the effects of SiC abrasive paper polishing and diamond powder polishing. In the case of high surface roughness, the adhesion of the diamond film on the SiC paper polished Mo substrate was larger than that of the diamond film on the diamond powder polished Mo substrate. Detachment of the diamond film from the SiC paper polished Mo substrate progressed along the polishing direction; while detachment of the diamond film from the diamond powder polished Mo substrate progressed in a random direction. It was thought that the detachment of the diamond film from a Mo substrate having an anisotropic polishing trace was suppressed because the anisotropic grooves restricted the formation of connections between the points of detachment at right angles to the groove direction. Therefore, the anisotropic surface morphology of the Mo substrate is effective for improving the adhesion of diamond film.     

Multilayer Au/TiO2Composite Films with Ultrafast Third-Order Nonlinear Optical Properties

We report on the ultrafast third-order optical nonlinearity in multilayer Au/TiO2 composite films fabricated on quartz substrates by pulsed laser deposition technique. The linear optical properties of the films are determined and optical absorption peaks due to surface plasmon resonance of Au particles are observed at about 590hm. The third-order optical nonlinearities of the films are investigated by z-scan method using a femtosecond laser （50 fs） at the wavelength of 800 nm. The sample showed fast nonlinear optical responses with nonlinear absorption coefficient and nonlinear refractive index being -3.66 × 10^-10 m/W and -2.95 × 10^-17 m^2/W, respectively. The results also show that the nonlinear optical effects increase with the increasing Au concentration in the composite films.     

Mo Back Contact for Flexible Polyimide Substrate Cu（In,Ga）Se2 Thin-Film Solar Cells

A dc magnetic sputtering process is applied to growth of a Mo back. contact layer onto the flexible polyimide （PI） and rigid soda-lime glass （SLC） substrates. The structural and electrical properties of the Mo layer coated on the two kinds of substrates are investigated by x-ray diffraction （XRD） and Hall effect measurements. The results show that the Mo layer on SLG indicate more better crystal quality and lower resistivity than that on the PI sheets. In contrast to the SLG substrate, the resistivity of the Mo layer on PI is increased by the vacuum annealing process at the substrate temperature of 450℃ under Se atmosphere, which is attributed to the cracked Mo layer induced by the mismatch of the coefficient of thermal expansion between PI and Mo material. The Cu（In,Ga）Se2 （CIGS） solar cells based on the PI and SLO substrates show the best conversion efficiencies of 8.16% and 10.98% （active area, 0.2cm^2）, respectively. The cell efficiency of flexible CIGS solar cells on PI is limited by its relatively lower fill factor caused by the Mo back contact.     

高能氮离子注入人造金刚石的热稳定性

 叙述了在GLZ-100E工业离子注入机上采用20~60 keV氮离子及氮分子离子注入人造金刚石晶体的实验研究。XPS分析表明，注入离子在人造金刚石颗粒表面形成了一层较为稳定的含氮混合物层。高温差热分析（DTA）的实验表明，经氮离子束处理的金刚石，其氧化起始温度T（onset）由原来的730 ℃左右提高到800 ℃以上，且随着氮注入剂量的增加而增加，氧化速度也随之变缓；差热分析还表明，随着温度的升高，金刚石首先转化为石墨（DTA曲线上表现为吸热），然后氧化燃烧生成CO₂（放热），而注入离子能量的增加，氧化温度的提高幅度略有下降。离子注入还使其高温石墨化性能显著改善。     

高温高压下纳米金刚石粉的特性研究

 研究了炸药爆轰合成的纳米金刚石粉在高温（约1 600 K）、高压（5.2 GPa）条件下的行为。将纳米金刚石粉与粉末合金（Ni₇₀Mn₂₅Co₅、100^#）混合、压制成圆片,与合金片 （Ni₇₀Mn₂₅Co₅）和人造石墨片一起交替放入高温高压合成腔体内,进行高温高压实验。实验结果表明：在高温高压条件下,纳米金刚石粉不能长大,反而石墨化了;在相同的高压和保温时间条件下,随着温度的降低,纳米金刚石粉的石墨化程度减弱,纳米金刚石粉的纳米颗粒长大,可长成0.1 mm尺寸的金刚石颗粒（温度为1 070 K左右）。而在此条件下,人造石墨不能合成金刚石,一般金刚石晶体要变成石墨相。这进一步表明,纳米金刚石颗粒表面的活性使得它可以在较低的温度下长成较大颗粒的金刚石。     

Electrical Studies on Pentacene Thin Film Transistors with Different Channel Widths

In order to conduct electrical studies on organic thin film transistors, top-contact devices are fabricated by growing polycrystalline films of freshly synthesized pentacene over Si/SiO2 substrates with two different channel widths under identical conditions. Reasonable field effect mobilities in order of 10^-2-10^-3 cm^2V^-1s^-1 are obtained in these devices. An elaborative electrical characterization of all the devices is undertaken to study the variance in output saturation current, field effect mobility, and leakage current with aging under ambient conditions. As compared to the devices with longer channel width, the devices with shorter channel width exhibit better electrical performance initially. However, the former devices sustain the moderate performance much longer than the latter ones.     

Imaging of ferroelectric vinylidene fluoride and trifluoroethylene copolymer films by scanning tunneling microscopy

In this paper, we reported the possibility to image non-conducting P(VDF-TrFE) copolymer films by STM. The films had the thickness of ∼25.0 nm and were spin-coated onto Au or graphite substrates. For films deposited on Au substrates, STM images showed grain structures of ∼100 nm, much larger than the grains of bare Au substrate. With increased scan rate, the film surface was damaged by STM tip and extreme protrusions and holes were observed. For films deposited on graphite substrates, we only obtained an image of very flat plane and could not observe the topography of the film surface. It seemed that the tip had pierced through the uppermost P(VDF-TrFE) layers and only imaged the layers nearest to the substrate. Asymmetrical current-voltage curves were observed from copolymer films deposited on HOPG. Experimental results were discussed.     

Effect of Pretreatment of TaN Substrates on Atomic Layer Deposition Growth of Ru Thin Films

The polycrystalline ruthenium films are grown on TaN substrates by atomic layer deposition （ALD） using bis（cyclopentadienyl） ruthenium [RuCp2] and oxygen as ruthenium precursor and reactant respectively at a deposition temperature of 330℃. The low-energy Ar ion bombardment and Ru pre-deposition are performed to the underlying TaN substrates before ALD process in order to improve the Ru nucleation. X-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy are carried out to characterize the properties of ALD Ru films. The results show that the nucleation density of Ru films with Ar^＋ bombardment to the underlying TaN substrates is much higher than that of the ones without any pretreatment. The possible reasons are discussed.     

同质与异质外延掺杂CVD金刚石薄膜的结构与性能

采用化学气相沉积(CVD)技术,以高温高压(HTHP)合成的(100)金刚石和p型(100)Si为衬底制备了硫掺杂和硼-硫共掺杂金刚石薄膜,利用原子力显微镜(AFM)、扫描隧道显微镜(STM)及隧道电流谱(CITS)等手段分析同质和异质外延CVD掺杂金刚石薄膜的结构和性能.结果表明:异Si衬底上CVD金刚石的形核密度低,薄膜表面比较粗糙,粗糙度达到18.5nm;同质HTHP金刚石衬底上CVD金刚石薄膜晶粒尺寸约为10—50nm,表面平整,表面粗糙度为1.8nm.拉曼测试和电阻测量的结果显示,在HTHP金刚 关键词： 金刚石 掺杂 外延     

脉冲激光制备类金刚石薄膜及原位激光等离子体发射光谱

用ＹＡＧ脉冲激光轰击真空室内的石墨靶,可以形成包含碳素的激光等离子体,并在硅或石英衬氏上淀积形成某种类型的碳膜。用光学多道分析仪原位测量了激光等离子体的发射光谱,给出反应空间可能存在的反应基团有碳原子、碳离子、碳分子等,用拉曼光谱研究了薄膜的结构,证明所形成的薄膜为类金刚石膜,并得出碳原子和碳离子与薄膜的类金刚石结构有关。制备过程中,氢的参与有利于薄膜中金刚石成分的形成。空间分辨的原位激光等离子体发射光谱表明,在反应空间存在薄膜形成的最佳位置。     

Growth and Characterization of InN Thin Films on Sapphire by MOCVD

Indium nitride thin films are grown on sapphire substrates by metal-organic chemical vapour deposition （MOCVD） By employing three-step layer buffers, the mirror-like layers on two-inch sapphire wafers have been obtained. The structural, optical and electrical characteristics of InN are investigated by x-ray diffraction, scanning electron microscopy, atomic force microscopy, photoluminescence and infrared optical absorption. The photoluminescence and the absorption studies of the materials reveal a marked energy bandgap structure around 0.70eV at room temperature. The room-temperature Hall mobility and carrier concentration of the film are typically 939 cm^2 /Vs, and 3.9 × 1018cm^-3, respectively.     

Electroluminescence from Multilayered Diamond/CeF3/SiO2 Films

We report a thin film electroluminescent device with a three-layer structure （diamond/CeF3/SiO2 films）, which has a luminance of 1.5 cd/m^2 at dc voltage 215 V. The electroluminescence spectrum at room temperature shows that the main peaks locate at 527 and 593nm, which are attributed to isolated emission centers of Ce^3＋ ions.