NiTi合金薄膜厚度对相变温度影响的X射线光电子能谱分析

采用X射线衍射和X射线光电子能谱实验手段对不同厚度的NiTi薄膜相变温度的变化进行了分析.结果表明在相同衬底温度和退火条件下,3?μm厚度的薄膜晶化温度高于18?μm厚度的薄膜.衬底温度越高,薄膜越易晶化,退火后薄膜奥氏体相转变温度As越低.薄膜的表面有TiO₂氧化层形成,氧化层阻止了Ni原子渗出;膜与基片的界面存在Ti₂O₃和NiO.由于表面和界面氧化层的存在,不同厚度的薄膜内层的厚度也不同,因而薄膜越薄,Ni原子的含量就越高.Ni原子的含量的不同会影响薄膜的相变温度. 关键词： NiTi合金薄膜 X射线衍射 相变 X射线光电子能谱     

Spatial structures formed during high-temperature vacuum annealing of diamond-like film deposited on a silicon substrate

The process of an ultrahigh vacuum annealing of a diamond-like carbon film deposited on a silicon substrate has been studied in situ using a photoemission microscope mounted at the MAX-lab synchrotron’s radiation source. After the annealing the film was examined ex situ using an atomic force microscope. It is revealed that the graphitization of the film occurs and round formations of several microns in size with a core of ∼0.2 μm in size appear on its surface at the temperature exceeding 1000°C. Photoemission images of these formations have shown the presence of silicon on their surface. Apparently, the interaction between the carbon film and silicon substrate begins in the middle of the formation and spreads to the adjacent region at the following stage.     

Persistent droplet motion in liquid-liquid dewetting

When a nonvolatile liquid film dewets from a partly compatible liquid substrate, the advancing dewetting front leaves behind droplets formed through a Rayleigh instability mechanism at its rim. We have found that these droplets continue to move in the direction of the dewetting front for extended periods (of order one day) with an initial droplet velocity varying linearly with the droplet size, and a displacement varying logarithmically with time. We attribute this persistent motion to a transient surface tension gradient on the substrate liquid surface trailing the dewetting front.     

Stability of the viscous fluid film flow on a uniformly heated substrate

The linear stability is investigated of a viscous fluid film on a uniformly heated substrate under an arbitrary angle of inclination against the horizon. At the substrate, the heat flux is set; at the film surface, the fluid-gas heat transfer coefficient is specified. The waves are considered in the film propagating in an arbitrary direction. Within the frame of the integral model, the dispersion ratios are obtained for the wave increment and phase velocity. The analysis is performed of the dispersion ratios, and the flow instability range is determined. At the Marangoni numbers above a certain threshold, standing wave or traveling wave type disturbances take place; the waves increase in the horizontal direction. For the traveling waves, the Marangoni number threshold value is significantly lower than the same for the standing waves.     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001     

Instability-driven quantum dots

When a film is strained in two dimensions, it can relax by developing a corrugation in the third dimension. We review here the resulting morphological instability that occurs by surface diffusion, called the Asaro–Tiller–Grinfel'd instability (ATG), especially on the paradigmatic silicon/germanium system. The instability is dictated by the balance between the elastic relaxation induced by the morphological evolution, and its surface energy cost. We focus here on its development at the nanoscales in epitaxial systems when a crystal film is coherently deposited on a substrate with a different lattice parameter, thence inducing epitaxial stresses. It eventually leads to the self-organization of quantum dots whose localization is dictated by the instability long-time dynamics. In these systems, new effects, such as film/substrate wetting or crystalline anisotropy, come into play and lead to a variety of behaviors.     

Al_(0.17)Ga_(0.83)As/GaAs(001)薄膜退火过程的热力学分析

在As_4束流等效压强为1.2×10~(-3)Pa、退火60 min条件下改变退火温度,对Al_(0.17)Ga_(0.83)As/GaAs薄膜表面平坦化的条件进行了探讨.定量分析了薄膜表面坑、岛与平台的覆盖率和台阶-平台间薄膜粗糙度随退火温度变化的规律,得到最合适的退火温度为545℃(±1℃);根据退火模型发现退火温度的改变会影响参与熟化的原子的数量,熟化原子比θ正比于退火温度,即θ∝Τ.退火温度540℃条件下退火约60 min,薄膜表面达到基本平坦,推测此时0.20θ0.25;退火温度为545℃时,推测退火时间约为55-60 min.本实验得到的结论可以为生长平坦的Al_(0.17)Ga_(0.83)As/GaAs薄膜提供理论与实验指导.     

Instability and reconstruction of a thin fluid film under inversion conditions

The development of mechanical instability of a neutral fluid film (liquid helium or hydrogen) under inversion conditions (it does not lie on a solid substrate but hangs from a ceiling) is discussed. Critical parameters of such an instability and the character of surface reconstruction under the action of van der Waals forces, bubble pressure, and gravitational forces are determined. The interrelation with the well-known Frenkel problem of a drop on a solid substrate is pointed out. An electrostatic mechanism is proposed for the stimulation of instability of a thin helium film. This mechanism is promising for the problem of superfluid helium leakage.     

Photoinduced heterostructure in a vanadium dioxide film

Physics of the Solid State - A photoinduced semiconductor–metal phase transition that occurs in a surface layer of vanadium dioxide film on an aluminum substrate within the time Δt...     

Annealing effects on the surface morphologies of thin PS/PMMA blend films with different film thickness

The surface morphology evolution of three thin polystyrene (PS)/polymethyl methacrylate (PMMA) blend films (<70 nm) on SiO_x substrates upon annealing were investigated by atomic force microscopy (AFM) and some interesting phenomena were observed. All the spin-coated PS/PMMA blend films were not in thermodynamic equilibrium. For the 67.1 and the 27.2 nm PS/PMMA blend films, owing to the low mobility of the PMMA-rich phase layer at substrate surfaces and interfacial stabilization caused by long-range van der Waals forces of the substrates, the long-lived metastable surface morphologies (the foam-like and the bicontinuous morphologies) were first observed. For the two-dimensional ultrathin PS/PMMA blend film (16.3 nm), the discrete domains of the PS-rich phases upon the PMMA-rich phase layer formed and the secondary phase separation occurred after a longer annealing time.     

Effects of substrate bias and nitrogen flow ratio on the surface morphology and binding state of reactively sputtered ZrNx films before and after annealing

ZrN_x films were sputtered in an Ar + N₂ atmosphere, with different substrate biases (0 to −200 V) at various nitrogen flow ratios (%N₂ = 0.5-24%). The surface morphology, resistivity, crystllinity, and bonding configuration of ZrN_x films, before and after vacuum annealing, were investigated. As compared with ZrN_x films grown without substrate bias, before and after annealing, the resistivity of 1% and 2% N₂ films decreases with increasing substrate biases. Simultaneously, if the applied bias is too high, the crystallinity of ZrN_x film will decrease. The surfaces of 1% and 2% N₂ flow films deposited without bias have small nodules, whereas the surface morphology of films deposited at −100 V of substrate bias exhibits large nodules and rugged surface. Once a −200 V of substrate bias is applied to the substrate, the surface morphology of ZrN_x films, grown at 1% and 2% nitrogen flow ratios, is smooth. Furthermore, there are two deconvoluted peaks in XPS spectra (i.e., Zr-O and Zr-N) of ZrN_x films deposited at −200 V of substrate bias before and after annealing. On the other hand, the surface morphology changes dramatically from rugged surfaces for film deposited at lower nitrogen flow ratio (%N₂ < 1%) to smoother and denser surfaces for film grown at higher nitrogen flow ratio (%N₂ ≥ 1%). The Zr-N bonding in 2% N₂ films still exist after annealing at 700 °C, while the Zr-N bonding in 0.5% and 16% N₂ flow film vanish at the same temperature. The connection between the resistivity, crystallinity, surface morphology, and bonding configuration of ZrN_x films and how they are influenced by the substrate bias and nitrogen flow ratio are discussed in this paper.     

Molecular dynamics investigation of deposition and annealing behaviors of Cu atoms onto Cu(0 0 1) substrate

The deposition growth and annealing behaviors of Cu atoms onto Cu(0 0 1) are investigated in atomic scale by molecular dynamics (MD) simulation. The results indicate that the film grows approximately in a layer-island mode as the incident energy is from 1 to 5 eV, while surface intermixing can be significantly observed at 10 eV. The surface roughness of the film decreases with increasing the incident energy, and the film after annealing becomes smoother and more ordered. These phenomena may be attributed to the enhanced atomic mobility for higher incident energy and thermal annealing. It also indicates that atomic mixing is more significant with increasing both the incident energy and substrate temperature. In addition, the peak-to-peak distances of radial distribution function (RDF) clearly indicate that the films before and after annealing are still fcc structure except for that at the melting temperature of 1375.6 K. After annealing, the film at the melting temperature returns to fcc structure instead of amorphous. Moreover, the residual stress and Poisson ratio of the film are remarkably affected by the thermal annealing. Furthermore, the density of thin film is obviously affected by the substrate temperature and annealing process. Therefore, one can conclude that high incident energy, substrate temperature and thermal annealing could help to enhance the surface morphology and promote the microstructure of the film.     

锰的硅化物薄膜在Si(100)-2×1表面生长的STM研究

锰的硅化物在微电子器件、自旋电子学器件等领域具有良好的应用前景, 了解锰的硅化物薄膜在硅表面的生长规律是其走向实际应用的关键步骤之一. 本文采用分子束外延方法在Si(100)-2× 1表面沉积了约4个原子层的锰薄膜, 并利用超高真空扫描隧道显微镜研究了该薄膜与硅衬底之间在250-750℃范围内的固相反应情况. 室温下沉积在硅衬底表面的锰原子与衬底不发生反应, 薄膜由无序的锰团簇构成; 当退火温度高于290℃时, 锰原子与衬底开始发生反应, 生成外形不规则的枝晶状锰硅化物和富锰的三维小岛; 325℃时, 衬底上开始形成平板状的MnSi小岛; 525℃时, 枝晶状锰硅化物完全消失, 出现平板状的MnSi_1.7大岛; 高于600℃时, 富锰的三维小岛和平板状的MnSi小岛全部消失, 仅剩下平板状的MnSi_1.7大岛. 这些结果说明退火温度决定了薄膜的形态和结构. 在大约600℃退火时岛的尺寸随着退火时间的延长而逐渐增大, 表明岛的生长遵从扩散限制的Ostwald熟化机理.     

Effects of annealing time on the structure,morphology, and stress of gold–chromium bilayer film

In this work, a 200-nm-thick gold film with a 10-nm-thick chromium layer used as an adhesive layer is fabricated on fused silica by the electron beam evaporation method. The effects of annealing time at 300℃ on the structure, morphology and stress of the film are studied. We find that chromium could diffuse to the surface of the film by formatting a solid solution with gold during annealing. Meanwhile, chromium is oxidized on the surface and diffused downward along the grain grooves in the gold film. The various operant mechanisms that change the residual stresses of gold films for different annealing times are discussed.     

退火时间对硼掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用高分辨透射电镜、紫外和可见光Raman光谱及循环伏安法研究了1000 ℃下退火不同时间的硼掺杂纳米金刚石薄膜的微结构和电化学性能. 结果表明,随退火时间的延长,薄膜中纳米金刚石晶粒尺寸逐渐减小.当退火时间为0.5 h时, 金刚石晶粒尺寸由未退火样品的约15 nm减小为约8 nm, 金刚石相含量增加;当退火时间为2.0 h时,金刚石晶粒减小为2—3 nm, 此时晶界增多,金刚石相含量减少;退火时间为2.5 h时纳米金刚石晶粒尺寸和金刚石相含量又略有上升.晶粒尺寸和金刚石相含量的变化表明薄膜在退火过程中发生了金刚石和非晶碳相的相互转变.可见光Raman光谱测试结果表明,不同退火时间下, G峰位置变化趋势与I_D/I_G值变化一致,说明薄膜内sp²碳团簇较大时, 非晶石墨相的有序化程度较高.退火0.5, 1.0, 1.5和2.0 h时, 电极表面进行准可逆电化学反应,而未退火和退火时间为2.5 h时电极表面进行不可逆电化学反应.退火有利于提高薄膜电极的传质效率, 退火0.5 h时薄膜电极的传质效率最高,催化氧化性能最好.较小的晶粒尺寸、 较高的金刚石相含量以及纳米金刚石晶粒的均匀分布有利于提高电极表面反应的可逆性和催化氧化性能.     

Thickness Determination for a Two-Layered Composite of a Film and a Plate by Low-Frequency Ultrasound

We present an ultrasonic method for determining the thickness of a composite consisting of a soft thin film attached to a hard plate substrate, by resonance spectra in the low frequency region, The interrogating waves can be incident only to the two-layered composite from the substrate side. The reflection spectra are obtained by FFT analysis of the compressive pulsed echoes from the composite, and the thicknesses of the film and the substrate are simultaneously inversed by the simulated annealing method from the resonant frequencies knowing other acoustical parameters in prior. The sensitivity of the method to individual thickness, its convergence and stability against experimental noises are studied, Experiment with interrogating wavelength 4 times larger than the film thickness in a sample of a polymer film （0.054mm） on an aluminium plate （6.24mm） verifies the validity of the method. The average relative errors in the measurement of the thicknesses of the film and the substrate are found to be -4.1% and -0.62%, respectively.     

Surface characterization and microstructure of ITO thin films at different annealing temperatures

In this study, the electron beam evaporation method is used to generate an indium tin oxide (ITO) thin film on a glass substrate at room temperature. The surface characteristics of this ITO thin film are then investigated by means of an AFM (atomic force microscopy) method. The influence of postgrowth thermal annealing on the microstructure and surface morphology of ITO thin films are also examined. The results demonstrate that the film annealed at higher annealing temperature (300 °C) has higher surface roughness, which is due to the aggregation of the native grains into larger clusters upon annealing. The fractal analysis reveals that the value of fractal dimension D_f falls within the range 2.16-2.20 depending upon the annealing temperatures and is calculated by the height-height correlation function.     

Tetrahedral amorphous carbon films as a frequency-increasing interlayer of surface acoustic wave devices with a ZnO/Si configuration

Tetrahedral amorphous carbon (ta-C) films deposited using filtered cathodic vacuum arc technology have been applied to the interlayer of surface acoustic wave devices with a ZnO/Si configuration. The phase velocity in the multilayered structure was analyzed in the first instance by theoretical calculations and was then measured by means of a network analyzer. It has been shown that the ta-C interlayer between piezoelectric film and Si substrate can strikingly increase the phase velocity of the surface acoustic wave. The greater the interlayer thickness is and the higher the content of the sp³ hybridization is, the faster surface acoustic wave propagates. However, the increment of phase velocity gradually decreases with increasing interlayer thickness. It was confirmed in this paper that the measured values of the phase velocity as a function of the interlayer thickness agree with the theoretical calculations.     

Stripe instability in thin films of smectic liquid-crystal polymers

Two-dimensional nanostripes are formed in thin films of side-chain liquid-crystalline polymer films when the material enters the smectic phase. The structure is investigated using transmission electron microscopy. Electron diffraction patterns show that the chain molecules are mostly aligned in the film plane and the average molecular director is parallel to the direction of the stripes. We discuss factors affecting the stripe amplitude and periodicity, such as the film thickness and the temperature of annealing in the nematic phase, and suggest a possible mechanism for their formation. We propose that an equilibrium instability occurs due to a competition between the layer-aligning effect of the substrate and the planar director alignment, forcing smectic layers perpendicular to the film surface. The stripes decorate the overall patterns of nematic director in the polymer film and provide a means of high-resolution imaging for observation of textures and disclinations.Received: 10 June 2003, Published online: 19 August 2003PACS: 68.37.Lp Transmission electron microscopy (TEM) (including STEM, HRTEM, etc.) - 61.30.Vx Polymer liquid crystals - 61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions - 68.55.Nq Composition and phase identification