Self-organized quantum-wire lattice via step flow growth of a short-period superlattice

We develop a theoretical model for step flow growth of multilayer films, taking into account the interlayer step-step interaction induced by misfit strain. We apply the model to simulate the growth of strain-compensated short-period superlattices. Step-bunch ordering improves in successive layers, leading to self-organized growth of a lattice of quantum wires. This quantum-wire array has some similarities to the "lateral composition modulation" observed experimentally in short-period superlattices.     

X-ray fluorescence analysis of Ni–Fe–Mn/Cr systems

We have developed a procedure for x-ray fluorescence determination of the constituent composition and thickness of two-layer Ni–Fe–Mn/Cr films deposited on Polikor, an aluminum oxide ceramic. We have calculated correction coefficients taking into account interelement interference effects in this system. We have experimentally determined the density of the materials making up the composition of the films. We have established and present the metrological characteristics of the procedure developed.     

SIMS study of annealing effect on element distribution in free-standing Al/Si and Zr/ZrSi<Subscript>2</Subscript> multilayer films

The results of secondary ion mass spectrometry (SIMS) depth profile analysis of free-standing Al/Si and Zr/ZrSi₂ multilayer films by a TOF.SIMS-5 instrument are reported for the first time. A prestudy of elemental composition in Zr and ZrSi₂ single layers and Zr/ZrSi₂ multilayer films deposited on Si substrates with sublayers revealed enhanced diffusion of carbon in Zr layers. Ion sputtering and charge neutralization conditions were determined to provide fixed position of free-standing thin films during analysis. An elemental composition of 100-nm-thick Zr/ZrSi₂ multilayer structures with Mo and B₄C protective layers was measured prior and after laser annealing.     

Atomic layer deposition of titanium dioxide thin films from tetraethoxytitanium and water

The structure and chemical composition of the titanium dioxide thin films formed by atomiclayer deposition (ALD) from tetraethoxytitanium and water precursors were studied by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy. The deposited films were demonstrated to have good stoichiometry and anatase type polycrystalline structure. The growth per cycle of titanium dioxide was calculated by an ALD model taking into account the sizes and number of ligands in reactant molecules.     

The thermal noise in multilayer coating

We consider thermal fluctuations in multilayer interferometric coating taking into account light propagation inside the coating. In particular, we calculate the reflected wave phase as a function of small displacements of the boundaries between the layers using transmission line model for interferometric coating and derive formula for spectral density of reflected phase in accordance with Fluctuation-Dissipation Theorem. We apply the developed approach for calculation of the spectral density of coating Brownian noise which makes main contribution into noise budget of second generation gravitational wave detectors.     

Pulsed laser deposited ZnO/ZnO:Li multilayer for blue light emitting diodes

Thin films of ZnO, Li doped ZnO (ZLO) and multilayer of ZnO and ZLO (ZnO/ZLO) were grown on silicon and corning glass substrates by pulsed laser deposition technique. Single phase formation and the crystalline qualities of the films were analyzed by X-ray diffraction and Li composition in the film was investigated to be 15 wt% by X-ray photoelectron spectroscopy. Raman spectrum reveals the hexagonal wurtzite structure of ZnO, ZLO and ZnO/ZLO multilayer and confirms the single phase formation. Films grown on corning glass shows more than 80% transmittance in the visible region and the optical band gaps were calculated to be 3.245, 3.26 and 3.22 eV for ZnO, ZLO and ZnO/ZLO, respectively. An efficient blue emission was observed in all films which were grown on silicon (1 0 0) substrate by photoluminescence (PL). PL measurements at different temperatures reveal that the PL emission intensity of ZnO/ZLO multilayer was weakly dependent on temperature as compared to the single layers of ZnO and ZLO and the wavelength of emission was independent of temperature. Our results indicate that ZnO/ZLO multilayer can be used for the fabrication of blue light emitting diodes.     

Graphical representation of reflection from single and double coating systems on metallic substrate

In the present work a new graphical method is described to represent the resultant of the multiply reflected waves from coating systems consisting of single and double layers on metallic substrate, taking into account the optical phase properties of the films.     

Determination of growth modes via spectroscopy: new simple analytical models

Analytical models for the determination of thin film growth modes were developed on the basis of the simultaneous multilayer (SM) growth model. The models take into account up-step and down-step diffusion, enabling quick identification of the growth modes from experimentally obtained spectroscopic data. We tested the models by applying them to growth data from the literature that had been recorded via Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and low-energy ion scattering (LEIS). We discuss the applicability of the new analytical models in comparison with the diffusion-corrected simultaneous multilayer (DCSM) model.     

Magnetic anisotropy of multilayer [Fe/Pt]n structures

The possibility of controlling the magnetic anisotropy of multilayer [Fe/Pt]n structures grown by magnetron sputtering of Fe and Pt plates by varying number n of layers is studied. Mössbauer spectroscopy data and measured magnetic hysteresis loops demonstrate that the multilayer [Fe/Pt]n structures at n = 16 have a predominantly perpendicular magnetic anisotropy. The results of X-ray photoelectron spectroscopy and micromagnetic simulation point to the presence of intermediate layers enriched in iron ions in the structures. The magnetic anisotropy perpendicular to the surface of the [Fe/Pt]n films at n = 16 is found to be caused by the anisotropy of the intermediate layers.     

Analysis of the Auger-photoelectron coincidence spectroscopy (APECS) spectra of metallic Pd,Ag, and Sn

The M45-level photoelectron spectrum of Ag metal measured in coincidence with the M45–VV(¹G) Auger-electron line is analyzed by taking into account the possibility of the M4–M5–VV Coster–Kronig (CK)-transition preceded Auger transition. We denote the atomic shells Mx(Mxy) and Nxy (x, y = 4,5) by MX(MXY) and V, respectively. The M4–M5 CK-transition rate is very small. The M45–VV Auger-electron spectra of metallic Pd and Sn measured in coincidence with the M4 (or M5)-level photoelectron line are analyzed. The M4–M5 CK-transition rates are also very small in metallic Pd and Sn. The coincidence Auger-electron line previously interpreted as the M4–M5–VV (or M4–M5V–VVV) Auger-electron line is largely due to the inelastically scattered M5-level photoelectron background beneath the M4-level photoelectron line. The APECS spectrum of Pd metal shows the first evidence of the M5V–VVV transition of the localized M5V shakeup two-hole state. The intensity ratio of the inelastically scattered Auger-electron background to the M5–VV Auger-electron main line of Ag metal measured in coincidence with the inelastically scattered M5-level photoelectron background beneath the M4-level photoemission line increases, as compared to that measured in coincidence with the M5-level photoelectron main line. This is because when the probability of the photoelectron being inelastically scattered increases, that of the Auger electron emitted by the same ionized atom, being inelastically scattered increases. In other words the photoelectrons and the Auger electrons are originated from the deeper atomic sites (longer pathlength).     

ToF-SIMS study of growth behavior in all-nanoparticle multilayer films using a novel indicator layer

All-nanoparticle multilayer films found novel applications in the areas of photonics, catalysis, sensors, and biomaterials. The assembly of nanoparticles into conformal and uniform films with precise control over chemical and physical properties poses a significant challenge. Using time-of-flight secondary ion mass spectrometry (ToF-SIMS), we have investigated the growth behavior in all-nanoparticle multilayer films using a novel indicator layer. The all-nanoparticle multilayer films were prepared by dipping the polyester substrate with electrostatic charges alternatively into solutions containing three different types of nanoparticles (TiO₂, Al₂O₃, and SiO₂). Upon the deposition of each layer, ToF-SIMS was employed to determine the surface chemical composition of intermediate products. The intermixing extent of TiO₂ indicator layer was used to reveal the stratification of each layer. Combining with zeta-potential measurements, the solvation and deposition of the under-layer species in the aqueous environment during fresh layer formation was proposed as a plausible cause for mutilayers not stratified into well-defined layers but displaying a nonlinear growth behavior.     

Fabrication of multilayer thin film filters by hydrofluoric acid bonding

A hydrofluoric acid (HF) bonding technique for multilayer thin films was studied to fabricate dielectric multilayer interference filters. The effects of pressure, HF concentration and annealing treatment on bonding strength were studied. Bonding strength of multilayer thin films of more than 5 MPa were obtained. In addition, a new type edge filter of 47 layers (47L) and a band-pass filter of 63 layers (63L), with their films sandwiched between glass substrates, were fabricated using this method. The measured transmittance spectra agreed well with the designed ones.     

Investigation of the structure and internal stresses in transition layers of nickel-based films

The structure and internal stresses in the transition layers of Ni, Ni-Fe, and Ni-Fe-Mo electrolytic films have been investigated. The mechanism for the formation of internal stresses taking into account the effect of multiple twinning in the transition layers of the films is proposed.     

Analysis of cross-correlation of interface roughness in multilayer structures with ultrashort periods

The diffusion scattering method is used for studying a series of W/B₄C multilayer structures with ultrashort periods (d = 0.8–1.5 nm). A simple theoretical model is described; the model takes into account both the dynamic effects in the interaction of counter-propagating diffuse-scattered waves and the mixing of film materials at the boundaries of the layers. It is shown that multilayer structures with a number of bilayers up to N = 700 and values of periods up to 0.8 nm are multilayer structures, which are well-correlated along the boundaries and exhibit resonance diffuse scattering. For structures with a period d > 1.1 nm, the largest contribution to the imperfection of boundaries comes not from the roughness, but from mixing of the films. The range of minimal periods of multilayer structures, for which the continuity of the films is preserved, is determined. The effect of “smoothing” of the substrate surface is discovered in multilayer structures with intact continuity; this contradicts to a certain extent the assumption concerning complete longitudinal correlation of roughnesses, which forms the basis of the theory.     

Fabrication and performance characterization of Al/Ni multilayer energetic films

Al/Ni multilayer bridge films, which were composed of alternate Al and Ni layers with bilayer thicknesses of 50, 100 and 200 nm, were prepared by RF magnetron sputtering. In each bilayer, the thickness ratio of Al to Ni was maintained at 3:2 to obtain an overall 1:1 atomic composition. The total thickness of Al/Ni multilayer films was 2 μm. XRD measurements show that the compound of AlNi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ni multilayer films with bilayer thicknesses of 50, 100 and 200 nm are 389.43, 396.69 and 409.92 J?g^?1, respectively. The temperatures of Al/Ni multilayer films were obviously higher than those of Al bridge film and Ni bridge film. Al/Ni multilayer films with modulation of 50 nm had the highest electrical explosion temperature of 7000 K. The exothermic reaction in Al/Ni multilayer films leads to a more intense electric explosion. Al/Ni multilayer bridge films with modulation period of 50 nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity.     

Investigation of hard magnetic properties in the Fe-Pt system by combinatorial deposition of thin film multilayer libraries

The magnetic properties of annealed Fe-Pt multilayer thin films with a broad composition range were investigated in order to identify the effects of composition and annealing temperature on the achievable coercive field, and to identify its maximum at low processing temperatures. Two types of multilayer systems were deposited as materials libraries to vary the composition from Fe₂₀Pt₈₀ to Fe₇₅Pt₂₅. The first type of multilayer was comprised of alternating opposing wedges, whereas the second type consisted of repeated uniform Fe and Pt layers interspersed periodically with Fe wedge layers. It was found that coercive fields μ₀H_C > 0.7 T can be achieved at an annealing temperature of about 300 °C (60 min) for both types of multilayers as long as the composition is close to 50:50. Higher annealing temperatures are needed for films, which deviate from this composition. Increasing the annealing temperature up to 700 °C leads to increased coercivity values. Multilayers with additional Fe layers showed increased remanence but reduced coercive fields.     

非均匀基底上三维薄膜生长的模拟研究

考虑原子在基底表面的扩散、沿岛周界的扩散和不同层间的扩散以及非均匀基底上表面吸附能分布的各向异性，建立起非均匀基底表面上原子扩散和三维薄膜生长的动力学蒙特卡罗模型.模拟得到在不同生长条件下出现的层状生长、岛状生长和混合生长三种生长模式和相应的多层薄膜生长形貌图.通过统计三维薄膜中原子在各层的分布，计算薄膜的表面粗糙度，得到薄膜生长模式与生长条件之间的关系. 关键词： 薄膜生长 非均匀基底 动力学蒙特卡罗模拟     

Interdiffusion in vacuum-deposited dielectric thin films

The observation of interdiffusion imperfection in vacuum-deposited optical thin films is reported. We measured the diffusion lengths of interdiffusion in dielectric thin films of typical combinations of coating materials (TiO₂–SiO₂ and TiO₂–MgF₂) by analyzing the atomic concentration data along the depth obtained with X-ray photoelectron spectroscopy technique. The resultant diffusion lengths in the deposited layers of dielectric coating materials are not small, hence the effects of interdiffusion should be taken into account in the design of optical filters.     

Transmission guided-mode resonance filters based on high reflection multilayer stacks

The transmission guided-mode resonance filters are implemented by integration of diffraction grating into classical thin films to produce high efficiency in the central wavelength and arbitrarily low sideband response over a quite large spectral range. Transmission guided-mode resonance filters require considerable fewer thin films to acquire narrow line width and high peak transmission in the central wavelength compared with classical multilayer high-reflectance coatings with a stack of quarter-wave thickness. The properties of transmission filters with single/double waveguide grating in the different layers of high refection stacks are compared each other. It is demonstrated that the narrow line width transmission filters can be abstained with only two different materials.     

High-resolution KLM Auger spectra of Ni metal excited by X-rays

KLM Auger spectra of Ni metal were measured with high energy resolution and high statistical accuracy using monochromatic synchrotron radiation. The spectra were corrected for the background from inelastically scattered electrons using partial intensity analysis where the electron trajectories were calculated by Monte Carlo simulation. Following background correction, the corrected spectra were fitted to model peaks taking into account intrinsic excitations. The measured transition energy of the most intense KL₂M₃ (¹D₂) Auger line is 7388.1 eV (0.4). The obtained relative intensities and energies of the Auger diagram lines are compared to published calculations as well as to experimental data for other 3d transition metals. In addition, the presence of Ni 3s, 3p photoelectron peaks in the spectra excited internally by Ni K X-rays is shown.