Temperature dependence of SSW linewidth in metallic thin films

Measurements of the standing spin wave linewidth H _n at 17·6 GHz from 6 °K to 400 °K are presented for two permalloy films whose structure is either polycrystalline or epitaxial. It is shown that in both films, H _n is proportional ton ² (n is the mode number). Although H _n is little modified by temperature (20% variation maximum over the entire temperature range), we experimentally state that the slopep of H _n (n ²) is a linear function of the saturation magnetizationM which agrees with a planar inhomogeneity model.The authors wish to thank H. Pascard and F. Hoffmann who have prepared and selected the films as also E. Villain and A. Gatineau for invaluable technical assistance.     

An alternative model to the two-magnon magnetic relaxation process in permalloy films

The thickness dependence of the linewidth difference for parallel and perpendicular ferromagnetic resonance in permalloy films at x-band and room temperature is calculated for the exchange conductivity-constant damping theory and is compared with experiment. The results are in good agreement for thin (d< 800 Å) and thick (d > 1500 Å) films. The data show a somewhat greater difference than the theory for intermediate thickness. The result indicate that a previously proposed two-magnon interpretation for the observed difference may be inappropriate.     

非晶硅薄膜金属诱导晶化的实时监测系统与晶化效果测量

设计了用于测量非晶硅薄膜诱导晶化的电阻值的实验装置,通过实时电阻测量方法实现了金属诱导晶化制备多晶硅薄膜的实时监控.结果表明薄膜的电阻值在高温下随晶化时间呈指数衰减,且具有很强的温度依赖关系.采用品粒边界势垒模型解释了阻值衰减行为,分析计算了样品的阻值衰减规律.应用拉曼光谱分析检测实时电阻测量的可靠性,结果表明实时电阻测量方法可以用于金属诱导晶化动力学的研究.     

Elasto-plastic behaviour of thin metal films

By extracting the variation of the plastic strain rate from measurements of the stress–strain curves of thin films of varying thickness, the large extent of the microdeformation stage was determined for tensile deformation of free-standing thin films, as well as for films on substrates deformed by cyclic heating. The stress varies dramatically with strain during this stage. It is demonstrated that this behaviour is common to most fine-grained polycrystals, and that the extent of the microdeformation stage is much larger than the conventional 0.2% proof strain, and depends both on the material as well as on the measurement technique. Therefore a careful analysis of this stage is essential in measuring the mechanical behaviour of these materials.     

Doppler-shifted cyclotron resonance in thin metal films

The velocities of electrons contained in a thin slab are quantized because the component of momentum transverse to the slab faces is quantized. For a free electron gas the transverse velocity is given by |v_H| = l(/m) (π/d) where l = 1, 2, 3, …. If a magnetic field is applied normal to the slab, the wave number and frequency dependent conductivity consists of a series of resonant terms. The resonances occur at the Doppler-shifted cyclotron resonance frequencies |ω_c| = ω ± p(/m) (π/d)² where l = 1, 2, 3, …. It is shown that these resonances in the conductivity result in an absorption in pure thin films at low temperatures which is periodic in magnetic field. The semi-classical expression for the absorption is in substantial agreement with the corresponding quantum calculation, and has the virtue that it may be readily extended to non-spherical Fermi surfaces.     

Anomalous temperature dependence of the Casimir force for thin metal films

Within the framework of the Drude dispersive model, we predict an unusual nonmonotonic temperature dependence of the Casimir force for thin metal films. For certain conditions, this force decreases with temperature due to the decrease of the metallic conductivity, whereas the force increases at high temperatures due to the increase of the thermal radiation pressure. We consider the attraction of a film to: either (i) a bulk ideal metal with a planar boundary, or (ii) a bulk metal sphere (lens). The experimental observation of the predicted decreasing temperature dependence of the Casimir force can put an end to the long-standing discussion on the role of the electron relaxation in the Casimir effect.     

Doped thin metal oxide films for catalytic gas sensors

TiO₂ and Pt doped TiO₂ thin films were grown by pulsed laser deposition on 〈0 0 1〉 SiO₂ substrates. The doped films were compared with undoped ones deposited in similar experimental conditions. An UV KrF* (λ = 248 nm, τ_FWHM ≅ 20 ns, ν = 2 Hz) excimer laser was used for the irradiation of the TiO₂ or Pt doped TiO₂ targets. The substrate temperatures were fixed during the growth of the thin films at values within the 300-500 °C range. The films’ surface morphology was investigated by atomic force microscopy and their crystalline quality by X-ray diffractometry. The corresponding transmission spectra were recorded with the aid of a double beam spectrophotometer in the spectral range of 400-1100 nm. No contaminants or Pt segregation were detected in the synthesized anatase phase TiO₂ thin films composition. Titania crystallites growth inhibition was observed with the increase of the dopant concentration. The average optical transmittance in the visible-infrared spectral range of the films is higher than 85%, which makes them suitable for sensor applications.     

Nanostructure and conductivity of thin metal films

Amorphous silver, copper, gold, and iron films of a thickness between 6 and 350 nm are grown on polymeric substrates by vacuum evaporation. The nanostructure of the films is investigated. The dependence of the conductivity on the film thickness is obtained, and a correlation between the surface morphology and the conductivity is established.     

Kinetics of the melting-dispersion process in copper thin films

The kinetics of a melting-dispersion process in copper thin films is investigated at different thicknesses of the films. It is shown that the film initially melts in local regions and then the melting front propagates over the sample. Melting of copper thin films of the same thickness can occur within different time periods depending on the temperature (from almost instantaneous melting at higher temperatures to melting proceeding over the course of a few hours at lower temperatures). The dependence of the activation energy for the melting-dispersion process on the film thickness is determined and explained in terms of hydrodynamics. The mechanism of the melting-dispersion process is considered.     

Quantum oscillations in the layer structure of thin metal films

Understanding the underlying physical principles that determine the internal structure of objects at the atomic scale is critical for the advancement of nanoscale science. We have performed synchrotron x-ray diffraction studies to determine the structural properties of smooth Pb films with varying thicknesses of 6 to 18 monolayers deposited on a Si(111) substrate at 110 K. We observe quasibilayer variations in the atomic interlayer spacings of the films consistent with charge density oscillations due to quantum confinement of conduction electrons and surface-interface interference effects. Quantum oscillations in atomic step height are also deduced.     

Hole formation in thin polymer films: a two-stage process

Thin, supported liquid films are known to rupture, creating holes throughout the film, due to defects or to van der Waals interactions. We show that the hole formation process before rupturing occurs in two stages, each characterized by distinct dynamical and morphological features. The time scale for the formation process is orders of magnitude slower than the translational (reptation) relaxation time of the individual chains. This has implications regarding the transition from the formation regime to subsequent hole growth regime on the underlying substrate.     

Optically induced transverse voltages in thin metal films

Results of experiments on laser induced voltages in metal films are summarized. The voltages are found to occur along certain directions in the plane of slant-angle vapour deposited films. A thermo-electric model based on periodic variations in the microscopic film structure, is described. The magnitude of the effect is proportional to the absorbed power/length between the contact points. Application of the films in the wavelength range 0.33–10.6μm is described and compared to more conventional detectors. A recent application, using the effect as a tool to profile non-uniformities in thin films, is also discussed.     

Temperature of phase transitions in thin two-layer metal films

It is experimentally established that the melting temperatures of Pb/Bi, Pb/Sn, Mg/Sn, Sn/Zn, and In/Zn two-layer films decrease with a decrease in their thickness.