不同厚度四面体非晶碳薄膜的高通量制备及表征

材料基因组工程能大幅度提高材料研发速度, 降低材料研发成本, 近年来受到广泛关注。本研究采用高通量制备工艺, 结合碳等离子体束流和基片位置的调控, 利用自主设计研制的45°双弯曲磁过滤阴极真空电弧设备, 沉积了厚度为4.7~183 nm的系列四面体非晶碳(ta-C)薄膜, 使用椭偏仪、原子力显微镜、拉曼光谱仪和X射线光电子能谱仪(XPS)表征了厚度对ta-C薄膜表面粗糙度、微结构和原子键态的影响。结果表明：通过碳等离子体束流和基片位置的调控, 实现了不同厚度ta-C薄膜的高通量制备。尽管膜厚不同, 所制备的ta-C薄膜均具有几乎不变的光滑表面(R_a=(0.38±0.02) nm)和色散值(Disp(G)), 说明不同厚度ta-C薄膜的sp³含量、sp²团簇尺寸保持相对稳定。XPS结果进一步证实ta-C薄膜的sp³相对含量均维持在(55±5)%。此外, 不同厚度ta-C薄膜的光学带隙E_opt均保持在(1.02±0.08)eV。相关结果为设计制备结构和光学性能可控的不同厚度ta-C薄膜提供了一种新思路。     

超薄四面体非晶碳膜的结构和性能

使用磁过滤阴极真空电弧(FCVA)技术制备不同厚度的超薄四面体非晶碳膜(ta-C)，研究了表征和测量超薄ta-C碳膜微观结构和性能的方法以及膜厚的影响。使用X射线衍射仪验证椭圆偏振光谱仪联用分光光度计表征膜厚度的可靠性并测量了膜密度；用拉曼谱分析薄膜的内在结构，验证用椭偏联用分光光度计表征sp³ C含量的可靠性；用Stoney^，s公式计算了薄膜的残余应力。结果表明，薄膜的厚度由7.6 nm增大到33.0 nm其沉积速率变化不大，为1.7±0.1 nm/min；根据椭偏联用分光光度计的表征结果，薄膜中sp³ C的含量逐渐减少，拓扑无序度降低，与拉曼谱的表征结果一致；厚度为7.6 nm的超薄ta-C碳膜中p³ C的含量最高；随着厚度的增大薄膜中的残余压应力从14 GPa降低到5 GPa；厚度为11.0 nm的薄膜主体层密度最大，为3070 kg/m³，致密性较好；厚度对薄ta-C碳膜表面粗糙度的影响较小。用椭偏和分光光度计测量超薄ta-C碳膜的厚度和表征显微结构是可行的，X射线反射法可用于测量超薄ta-C碳膜密度和表面粗糙度，但是对薄膜的质量要求较高。     

Characterization of ion-beam-deposited diamond-like carbon films

Diamond-like carbon (DLC) films are excellent prospects for a wide range of high-technology applications but their precise structure and properties are not well understood. The purpose of the present work was to use several complementary techniques to characterize the nature, structure and microstructure of DLC films. Thin DLC films were deposited on various substrates in the presence of a Si interlayer (500 Å thick) using CH₄ ion-beam deposition at an acceleration energy of 750 eV and a current density of about 2.5 mA cm⁻². The Si interlayer was deposited by either e-beam evaporation or Si evaporation enhanced by Ar⁺ beam bombardment (1 keV). The produced DLC films were featureless, very smooth and of high hardness (2900–3300 kg mm⁻²). Auger electron spectroscopy and electron diffraction showed that the films were mainly amorphous. Their microstracture was characterized by a three-dimensional network structure with a medium-range order of about 25 nm. Fourier transform infrared and Raman spectroscopies showed that the films were mainly composed of sp³ and sp² carbon-bonded hydrogen. The sp³/sp² ratio varied from 3.2 to 4.1 and was found to depend on the nature of the Si bond layer. The results showed that the nucleation of the diamondlike structure was promoted on the Si interlayer that was deposited under Ar⁺ beam bombardment. This effect can be explained by the higher surface roughness produced in this interlayer as suggested by the reflectivity measurements. Spectroscopic ellipsometry revealed that the films had an optical band gap between 1.56–1.64 eV. The present results are consistent with previous proposals suggesting that the DLC structure is composed of small graphitelike clusters (involving fused six-fold rings) that are interconnected by sp³-bonded carbon.     

Analysis on Structure and Properties of Diamondlike Carbon Films from Ion Beam Deposition

Diamondlike carbon (DLC) films from a primary ion beam deposition system, were examined using nanoindentation, SEM, AES, XPS, and Raman Spectroscopy. The films have hardness values ranging from 21 to 29 GPa. The results of SEM and AES show that the films are predominantly carbon without any crystalline features, and that nitrogen is incorporated as nitrogen is used as the ion beam source. XPS, and Raman Spectroscopy confirm that the films are amorphous carbon with a combination of sp³ with sp² bonding. It is concluded that DLC films can be directly deposited on steel using a single ion beam to sputter the solid target, and the structure and properties of DLC largely depend on ion beam source.     

厚度对真空电弧制备传感器用非晶ta-C膜性能的影响

采用双弯曲磁过滤阴极真空电弧沉积方法在传感器用P型单晶硅上制备ta-C膜,并通过实验测试的手段研究厚度对其组织及性能的影响.研究结果表明:逐渐延长沉积时间后,沉积速率始终保持1.6 nm/min的稳定状态.分别运用椭偏仪和光度计测定ta-C膜的厚度结果基本一致,差值小于2 nm.随着膜厚的增加,sp3C比例发生了减小,...     

Electrical properties of reactively sputtered carbon nitride films

Carbon nitride films with β-C₃N₄ crystals of 200 nm grain size were grown on Si (1 0 0) substrates using magnetron sputtering. These films were characterized by transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Carbon nitride films had low surface roughness. Maximum N/C ratio of 0.5 was achieved in the films. Chemical bonds of sp, sp² and sp³ coexisted in the films. The fraction of each bond was related to the deposition conditions. The resistivities of the films were measured, which ranged from 1×10³ to 1×10⁷ Ω cm. The measured resistivity results indicated that the carbon nitride films had semiconductive properties. The resistivity largely depended on the sp³/sp² ratio. Effects of N₂ fraction, target current and substrate bias were investigated. All these deposition parameters had influence on the chemical bonds of the films, and on the resistivities too. High sp³/sp² ratio resulted in high resistivity.     

Low temperature internal friction of diamond-like carbon films

We have studied the internal friction of amorphous diamond-like carbon films prepared by pulsed-laser deposition from 0.4 to 300 K. The low temperature internal friction below 10 K is dominated by the atomic tunneling states for amorphous solids, which is a measure of structure disorder. We have tried to vary the content of sp³ carbon atoms versus sp² ones by changing laser fleunce, by doping with N and Ar, and by annealing at 500 °C for 20 min. Our results show that the internal friction varies about one order of magnitude from 2×10⁻⁵ to 2×10⁻⁴, and its value is higher with higher sp³ content when the film quality is generally considered superior. However, it is known that as-deposited diamond-like carbon films with high sp³ content are heavily stressed. Annealing and doping are used to release the stress. We conclude that in addition to tetrahedral bonding, low stress is also important in reducing structure disorder associated with the low energy tunneling states in amorphous solids.     

金属过渡层类型对非晶碳膜结构性能的影响

采用直流磁控溅射技术制备不同金属过渡层(Cr, Ti, W)的类石墨非晶碳膜(GLC), 研究过渡层类型对非晶碳膜微结构的影响, 并考察其在人工海水中摩擦性能的变化。研究结果表明: Cr/GLC薄膜sp²杂化键含量最高, 沿GLC表面到铬碳界面方向, sp²杂化键含量逐渐增大, Ti过渡层和W过渡层的sp²杂化键含量变化不明显。Cr/GLC薄膜较高的sp²杂化键含量有助于其在摩擦过程中产生可以充当润滑相的石墨化转化摩擦转移膜。在三种涂层中, Cr/GLC薄膜表现出最高的腐蚀电位-0.16 V和最低的腐蚀电流密度4.42×10^-9 A/cm²。因此相较于Ti, W作过渡层的GLC薄膜, Cr/GLC薄膜在海水环境下表现出优异的摩擦学特性。     

沉积时间对聚醚醚酮表面类金刚石薄膜的结构和性能的影响

采用直流磁控溅射技术在聚醚醚酮(PEEK)表面制备不同厚度的类金刚石(DLC)薄膜,研究了沉积时间对其表/界面结构、组分、疏水、力学和光透过性能的影响。结果表明,在平均沉积速率为5.71 nm/min的条件下,随着沉积时间的延长DLC薄膜的厚度线性增大、碳原子的致密性提高、界面互锁结构增强,而界面结合强度逐渐降低。沉积时间≤15 min时,基体结构的影响使拟合计算出的I_D/I_G值为0.23~0.25和sp²/sp³比值较小(0.58~0.74);沉积时间>15 min时基体的影响较小,I_D/I_G值突增大至0.81,sp²/sp³值也比较大(0.96~1.12)。沉积时间的延长使PEEK基体的温度逐渐升高,使膜内的sp²/sp³值逐渐增大。薄膜表面的氧含量先降低然后趋于平缓,部分C=O转化为C-O。随着沉积时间的延长,PEEK/DLC复合薄膜的硬度、弹性模量及防紫外线和阻隔红外线性能都逐渐提高,其表面粗糙度和疏水性的变化趋势是先提高后降低。沉积时间为32 min的薄膜,其表面粗糙度和水接触角达到最大值,分别为495 nm和108.29°。     

Mechanical properties of a-C:H and a-C:H/SiOx nanocomposite thin films prepared by ion-assisted plasma-enhanced chemical vapor deposition

a-C:H and a-C:H/SiO_x nanocomposite thin films were deposited on silicon, aluminum and polyimide substrates at 25 °C in an asymmetric 13.56 MHz r.f.-driven plasma reactor under heavy ion bombardment. Fourier transform infrared spectra of the films indicate that the nanocomposite filmsappears to consist of an atomic scale random network of a-C:H and SiO_x. Raman spectroscopy revealed that the sp² carbon fraction in the nanocomposite film was reduced compared with the a-C:H film. The intrinsic stress of both films increased with increasing negative bias voltage (−V_dc) at the substrate. However, the nanocomposite films exhibited lower intrinsic stress compared w with a-C:H-only films. Especially, a thin SiO_x-rich interlayer was very effective in reducing the film stress and enhancing the bonding strength at the interface. The interlayer allowed deposition of thick films of up to 5 μm. Also, the nanocomposite films were stable in 0.1 M NaOH solution and showed good microhardness.     

Photoelectron spectroscopy of ion-irradiated B-doped CVD diamond surfaces

Chemical vapour deposition (CVD) diamond films were irradiated by 1 keV argon ions at room temperature with doses ranging from 3.6 × 10¹² to 1.1 × 10¹⁶ Ar⁺ cm². The influence of sputtering on the valence band density of states of a boron-doped CVD diamond film was investigated by ultraviolet photoelectron spectroscopy and the changes in the plasmon features were observed by X-ray photoelectron spectroscopy of the carbon Is core level and its loss region. A gradual change from typical diamond features to amorphous carbon was observed after prolonged bombardment times. Above a critical dose D_crit of 5.8 × 10¹⁴ Ar⁺ cm² the damaged surface layer is characterized by a splitting of the C Is bulk peak into two components: a bulk-like diamond peak at 285.3 eV binding energy and a defect peak with 1 eV lower binding energy, which is attributed to the production of an amorphous sp²-rich carbon matrix. Moreover additional occupied states in the range of 0–4 eV binding energy, completely different to those observed on reconstructed diamond surfaces, were observed in the valence band spectra of the ion-irradiated diamond surface. These filled states can also be attributed to the amorphous carbon matrix which is formed at high doses. At very low doses (< 3 × 10¹⁴ ions cm²) only a band bending of the C Is diamond core level peak, along with the formation of some occupied states in the band structure at around 3.8 eV binding energy was observed. A comparison with annealed hydrogen-free CVD diamond surfaces shows some similarities concerning these filled states. The obtained spectra are compared with other crystalline and amorphous forms of carbon and the results are discussed in terms of an irradiation-induced change in the atomic structure of the surface. A comparison of ion bombarded and annealed diamond samples clearly shows that no graphitization takes place in the latter case.     

Doping effects on the optical properties of evaporated a-Si:H films

Thin films of a-Si:H are deposited on substrates at 300°C by a conventional thermal evaporation technique. The electrical conductivity of these films is modified by the addition of antimony giving n-type films. The optical properties of the films are investigated using spectrophotometric measurements of the transmittance and reflectance in the wavelength range 200–3000 nm. Both the refractive index n and the absorption coefficient increase when the Sb content is increased. The absorption edge shifts to lower energies for doped films. The optical gap E_g is evaluated using three different plots for comparison, namely; (hν)^1/2, (/hν)^1/2 and (hν)^1/3. The value of E_g decreases with doping for the three expressions. The Urbach parameter E₀ is calculated and found to increase with doping from 74 meV for the undoped film to 183 meV for concentrations of 9.4 at.% Sb.     

Ion-activated interface adsorption of oxygen during silver deposition on silicon

The process of ion-activated oxygen adsorption on silicon has been investigated using an experimental concept with simultaneous deposition of silver films. Auger electron spectroscopy in combination with sputter depth profiling is subsequently performed to determine the amount of oxygen adsorbed at the Ag---Si interface. Noble gas ions (⁴He⁺, ²⁰Ne⁺ and ⁴⁰Ar⁺)with energies between 50 and 175 keV were used, and it was found that for substrate temperatures of 300–700 K the oxygen adsorption depends strongly on ion mass, ion energy and ion flux density. For flux densities of 5 × 10¹¹ cm⁻² s⁻¹ or less, adsorption dominates and, in particular, for light-ion bombardment the majority of adsorbed oxygen atoms form chemical bonds with the silicon surface atoms (Si---O). However, for heavy ions, physical sputtering starts to compete and limits the effective rate of adsorption. At sufficiently high ion fluxes the adsorption starts to decrease, and for all ions and energies used in this work it is found that, if the electronic energy deposition density exceeds a critical value of about 1.2 × 10²¹ eV cm⁻² s⁻¹, dissociation of the Si---O bonds prevails with a corresponding loss in the adsorbed oxygen quantity.     

离子束增强沉积制备TiB_2薄膜及其性能研究

用离子束增强沉积法（IBED）在硅及铜基体上沉积了TiB2薄膜，研究了轰击离子束能量和束流对薄膜的微结构及力学性能的影响。用俄歇电子谱（AES）分析了膜的成分及其界面状况，用X射线衍射（XRD）研究了膜的微结构，并测定了膜的硬度及进行了膜的高温氧化试验。结果指出：（1）离子束轰击使薄膜晶化，从而影响到膜的硬度及抗高温氧化性能；（2）离子束增强沉积的二硼化钛薄膜是一种耐高温氧化的高硬膜。     

Ion beam sputter deposited Permalloy thin films

Ni₈₀Fe₂₀ thin films were deposited using a wide range of process parameters in a dual source ion beam sputter deposition system. The films were characterized structurally, chemically, and magnetically. Two modes of deposition were investigated; the first permitted concurrent second source bombardment during film deposition but was limited in net deposition rate to about 300 Å/m; the second provided deposition rates in excess of 1000 Å/m, but did not allow for concurrent ion bombardment from the second ion source. Depending on specific conditions film stress varied from slightly tensile to highly compressive in both deposition modes. This, combined with small variations in magnetostriction, resulted in films with vertical anisotropy and stripe domain patterns as well as conditions where well-formed closure domain patterns were observed in yoke shaped structures. For monolithic films, easy axis coercivities <0.7 Oe, anisotropy fields ≃5Oe and hard axis coercivities of <0.5 Oe were obtained     

Modelling of boron nitride: Atomic scale simulations on thin film growth

Molecular-dynamics simulations on ion-beam deposition of boron nitride are presented. A realistic Tersoff-like potential energy functional for boron nitride, which was specially fitted to ab initio-data, has been used. The impact of energetic boron and nitrogen atoms on a c-BN target is simulated with energies ranging from 10 to 600 eV. The structural analysis of the grown films shows that a loose, dominantly sp²-bonded structure arises at high ion flux. In no case the formation of a sp³-bonded phase is observed, but the obtained films partially reveal textured basal planes as found in experiment. Two different growth regimes are identified for ion energies above and below 100 eV.     

Surface characterization of titanium oxide films synthesized by ion beam enhanced deposition

In this article, titanium oxide films were prepared by ion beam enhanced deposition where titanium was evaporated by electron beam and simultaneously bombarded with xenon ion beams at an energy of 40 keV in an O₂ environment. X-ray photoelectron spectroscopy and Auger electron spectroscopy were used to research the chemical state and composition of the titanium oxide films. The results show that surface of the film was fully oxidized. After the surface was removed by argon ion sputtering, the results show that Ti²⁺, Ti³⁺ and Ti⁴⁺ states exist on the sputtered surface. The atomic concentration of all the three titanium states were calculated. The chemical shift of O 1s peak was also observed on the near surface.     

Nitrogen dilution effects on structural and electrical properties of hot-wire-deposited a-SiN:H films for deep-sub-micron CMOS technologies

Hot-wire chemical vapor-deposited silicon nitride is a potential dielectric material compared to glow-discharge-deposited material due to its lower hydrogen content. In several earlier publications we have demonstrated these aspects of the HWCVD nitride. However, to replace SiO₂ with a-SiN:H as the gate dielectric, this material needs further improvement. In this paper we report the results of our efforts to achieve this through nitrogen dilution of the SiH₄+NH₃ gas mixture used for deposition. To understand the electrical behavior of these nitride films, we characterized the films by high-frequency capacitance–voltage (HFCV) and DC J–E measurements. We attempted to evolve a correlation between the breakdown strength, as determined from the J–E curves, and aspects such as the bond density, etching rate, deposition rate and refractive index. From these correlations, we infer that nitrogen dilution of the source gas mixture has a beneficial effect on the physical and electrical properties of the hot-wire a-SiN:H films. For the highest dilution, we obtained a breakdown voltage of 12 MV cm⁻¹.     

Effect of Ion Bombardment on the Structure and Properties of Polycrystalline Chromium Films

Polycrystalline chromium films were fabricated by electron beam evaporation with concurrent bombardment using argon ions from an ion gun or by sputtering with substrate bias. The microstructure and composition of the films were characterized using TEM/EDS. It was found that the grain size/shape, porosity, and argon content of the films strongly depend on the deposition parameters such as bombardment ion current density, deposition rate, argon pressure and substrate bias. Film properties including residual stress, resistivity, and reflectance were measured. A correlation of deposition, structure, and properties is discussed.     

Implantation effect of diamond-like carbon films by 110 keV nitrogen ions

Diamond-like carbon films, grown on microscope slides by a dual-ion beam sputtering system, were implanted by 110 keV N⁺ under the doses of 1 × 10¹⁵, 1 × 10¹⁶ and 1 × 10¹⁷ions cm⁻² respectively. The implantation induced changes in electrical resistivity of the films and in infrared (IR) transmittance of the specimens were investigated as a function of implantation dose. The structural changes of the films were also studied using IR spectroscopy and Raman spectroscopy. It was observed that, with the increase of implantation dose, the diamond-like carbon films display two different stages in electrical and optical behaviours. The first is the increase of both the film resistivity and the IR transmittance of specimen at the dose of 1 × 10¹⁵ ions cm⁻² which, we consider, is attributed to the implantation-induced increase sp³ C---H bonds. However, when the doses are higher than 1 × 10¹⁵ ions cm⁻², the film resistivity and the IR transmittance of specimen decrea significantly and the decrease rates at dose range of 1×10¹⁶ to 1×10¹⁷ ions cm⁻² are smaller than those between 1×10¹⁵ and 1 × 10¹⁶ ions cm⁻². We conclude that the significant reductions of the two parameters at high doses are caused by the decreases of bond-angle disorder and of sp³ C---H bonds, the increases of sp² C---C bonds dominated the crystallite size and/or number and also the sp² C---H bonds. The smaller decrease rates at a dose range of 1 × 10¹⁶ to 1 × 10¹⁷ ions cm⁻² may be caused by further recombination of some retained hydrogen atoms to carbon atoms.