Vacuum deposited polymer/metal multilayer films for optical application

Vacuum-deposited polymer/silver/polymer reflectors and tantalum/polymer/aluminum Fabry-Perot interference filters were fabricated in a vacuum web coating operation on polyester substrates with a new, high-speed deposition process. Reflectivities were measured in the wavelength range from 0.3 μm to 0.8 μm. This new vacuum processing technique has been shown to be capable of deposition line speeds in excess of 500 linear m min⁻¹ (D.G. Shaw and M.G. Langlois, Proc. 7th Int. Conf. Vacuum Web Coating, November 1993, p. 268). Central to this technique is a new vacuum deposition process for the high-rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high-speed polymer film deposition process has been named the polymer multi-layer process. Also, vacuum-deposited, index-matched, polymer/CaF₂ composites were fabricated from monomer slurries that were subsequently cured with ultraviolet light. This second technique is called the liquid multi-layer process. Each of these polymer processes is compatible with each other and with conventional vacuum deposition processes such as sputtering or evaporation.     

Photoluminescence properties of dye-doped polymer multilayer films with periodic structure

We report the photoluminescence properties of polymer alternating multilayer films containing a fluorescent dye in one component. The alternating multilayer film with periodicity in both refractive indices and dye distribution showed 6 times higher intensity of amplified spontaneous emission than the multilayer film with periodicity in dye distribution only. Multilayer films that have a structure of Fabry-Perot resonator showed a lasing threshold of approximately 1.7 mJ cm^− 2.     

GZO/Ag/GZO多层薄膜制备、结构与光电特性的研究

采用射频磁控溅射和离子束溅射联合设备在玻璃衬底上制备出了具有良好附着性、低电阻率和高透过率的GZO/Ag/GZO(ZnO掺杂Ga_2O_3简称GZO)多层薄膜.X射线衍射谱表明GZO/Ag/GZO多层薄膜是多晶膜,GZO层具有ZnO的六角纤锌矿结构,最佳取向为(002)方向;Ag层是立方结构,具有(111)取向.在GZO层厚度一定的情况下,研究了Ag层厚度的变化对多层膜结构以及光电特性的影响.研究发现,当Ag层厚度为10nm时,3层膜的电阻率为9×10~(-5)Ω·cm,在可见光范围内平均透过率达到89.7%,薄膜对应的品质因子数值为3.4×10~(-2)Ω~(-1).     

Kinetic approach to the release of vinyl chloride monomer from polymer films,as related to diffusional theories

Monomer-release kinetics from polyvinyl chloride films, previously saturated by equilibration with monomer solutions in $\text{n}$-hexane, ethylene glycol monomethylether, methanol, and water, were measured by extraction with these model solvents, at 10–50 °C. Solute desorption rate data fitted a linear plot of total amount of solute released $\text{vs}$. the square root of time. Their analysis, in terms of diffusional release theory of a dissolved solute from a polymer matrix with initial solute loading given by the solubility limit, allowed one to obtain diffusivities of vinyl chloride in the polymer as a function of temperature, from which an activation energy of 11.9 ± 0.9 Kcal/mol could be calculated. Release kinetics were practically controlled by the low diffusivities, without any resistance to solute transport due to external mass transfer coefficients. The accelerating influence of solvents, relative to solvent-free experiments reported in the literature, may be compared to a plasticizing penetrant effect, which, however, does not appear to be susceptible, as to its bearing on diffusivities, to the chemical nature of the solvent used.     

Nanostructured titanium/diamond-like carbon multilayer films: deposition, characterization, and applications

Titanium/diamond-like carbon multilayer (TDML) films were deposited using a hybrid system combining radio frequency (RF)-sputtering and RF-plasma enhanced chemical vapor deposition (PECVD) techniques under a varied number of Ti/diamond-like carbon (DLC) bilayers from 1 to 4, at high base pressure of 1 × 10(-3) Torr. The multilayer approach was used to create unique structures such as nanospheres and nanorods in TDML films, which is confirmed by scanning electron microscopy (SEM) analysis and explained by a hypothetical model. Surface composition was evaluated by X-ray photoelectron spectroscopy (XPS), whereas energy dispersive X-ray analysis (EDAX) and time-of-flight secondary ion mass spectrometer (ToF-SIMS) measurements were performed to investigate the bulk composition. X-ray diffraction (XRD) was used to evaluate the phase and crystallinity of the deposited TDML films. Residual stress in these films was found to be significantly low. These TDML films were found to have excellent nanomechanical properties with maximum hardness of 41.2 GPa. In addition, various nanomechanical parameters were calculated and correlated with each other. Owing to metallic interfacial layer of Ti in multilayer films, the optical properties, electrical properties, and photoluminescence were improved significantly. Due to versatile nanomechanical properties and biocompatibility of DLC and DLC based films, these TDML films may also find applications in biomedical science.     

Structure,phase composition,and nanohardness of vacuum-annealed multilayer fullerite/aluminum films

The influence of the number of layers and thermal annealing on the structure, elemental and phase compositions, and nanohardness of multilayer fullerite/aluminum films has been studied by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray microanalysis, and nanoindentation. The results demonstrate that sequential growth of five aluminum layers and four fullerite layers, each 50 nm in thickness, on oxidized single-crystal silicon substrates leads to the formation of textured films, which retain 111 texture after vacuum annealing at 620 K (τ = 5 h). In the case of the growth of bilayer films of greater thickness, C₆₀(200 nm)/Al(300 nm), the fullerite and aluminum have a polycrystalline structure with no growth texture. Thermal annealing of the bilayer films leads to the formation of a new phase, Al_xC₆₀. The materials studied here possess enhanced nanohardness compared to pure aluminum and fullerite films.     

Surface doping of VT6 alloy with zirconium by pulsed electron-beam mixing of predeposited multilayer Zr/Ti film

We have studied characteristics of the surface doping of VT6 alloy (Ti-6Al-4V) with zirconium, which was effected in order to reduce the concentrations of Al and V at the surface. The doping was performed by liquid-phase mixing of a [Zr(20 nm)/Ti(20 nm)]₁₂ multilayer film with a total thickness of 480 nm and the substrate (VT6 alloy) under the action of low-energy (～20 keV) pulsed high-current electron beam (2.5 μs, 3.5 J/cm²). It is established that the pulsed beam-induced melting leads to the homogeneous mixing of all Ti/Zr nanolayers and the diffusion of Zr into substrate to a depth of ～0.5 μm. As a result, the surface layer with a thickness of ～0.5 μm is free of Al and V atoms and has a single-phase submicrocrystalline structure of α-Ti₇₀Zr₃₀ solid solution. Subsequent vacuum annealing leads to a decrease in the average grain size in the nearsurface layer to 90 nm and to an increase in the nanohardness of the doped layer.     

Effect of deposition temperature on morphology and magnetic properties of Co50Fe50 thin films produced by femtosecond pulsed laser deposition

Deposition temperature effect on morphological, topological and magnetic characteristics of nanoparticle-assembled Co₅₀Fe₅₀ films produced by femtosecond pulsed laser deposition (fs-PLD) on Kapton substrate was investigated. For substrate temperature T_s ≥ 550 K, a decrement of the nanoparticle's aggregates and an increment of the nanoparticle's density were observed with respect to room temperature deposition; this in association with a strong increase of the magnetoelastic anisotropy energy lead to a reduction of the remanence ratio, a significant rise of the saturation and coercive fields and an enhancement of the saturation magnetization. The results are discussed focusing on: i) the correlation between films structure and their magnetic behavior; ii) the role of the different anisotropy energies in determining the harder in-plane magnetic behavior for T_s ≥ 550 K. The thermal strain of Kapton substrate holds an important role in generating morphological and topological characteristics of the fs-PLD films and corresponding magnetic properties.     

具有优异力敏特性的纳米Fe50Ni50粉体/丁基橡胶复合材料薄膜

为开发力敏性能更为优异的复合材料薄膜,首先,通过液相还原法制备了粒径约为100 nm的纳米Fe50Ni50粉体,并通过液态混合分散工艺将纳米粉体与丁基橡胶(IIR)混合分散;然后,通过机械混炼及压制得到了粉体分布均匀、含量为65wt%的纳米Fe50Ni50粉体/IIR复合材料薄膜;最后,研究了在连续加载/卸载速度为0.10 mm/min、测试频率为1 kHz的条件下,纳米Fe50Ni50粉体/IIR复合材料薄膜的力敏特性。结果表明:液态混合分散工艺可使Fe50Ni50粉体在复合材料薄膜中达到纳米级均匀分散效果;当压应力为0.20~0.90 MPa时,薄膜越厚,其标准偏差越大,力敏稳定性越差;随压应力增大,厚度为185μm的薄膜在加载阶段的阻抗近似线性下降,力敏灵敏度稳定在40~60范围内,标准偏差约为1~2。所得结论表明在压应力为0.20~0.90 MPa时,制备的薄膜具有优异的力敏特性。      

Structural and residual stress changes in Mo/a-Si multilayer thin films with annealing

The thermal and mechanical stability of molybdenum and amorphous silicon (Mo/a-Si) optical multilayers (3 and 4 nm nominal thickness of Mo and Si) at 316 °C were studied by annealing experiments. Growth of amorphous Mo-Si interlayers with a stoichiometry of 12 was observed at the Mo/a-Si interfaces. In addition, residual stresses significantly changed in the crystalline Mo and amorphous Si layers with annealing. High resolution electron microscopy, selected area electron diffraction, and X-ray diffraction of the crystalline Mo revealed that tensile stresses increased from 2 to about 10 GPa in the lateral direction (parallel to the interface plane). The compressive strains that developed in the vertical direction (perpendicular to the interface plane) are consistent with Poisson's ratio. Laser deflectometer measurements of thicker (0.1 m) amorphous silicon layers may indicate compressive-stress relaxation in the amorphous silicon with annealing, consistent with other investigations. Overall, the residual stress in a 40-bilayer film changes from about –0.5 to about +1.5 GPa. Structural transformation after relatively short annealing times at the interfaces in the thin amorphous Mo-Si interlayers may rationalize increased tensile strains in the Mo layers.     

Structure, hardness and thermal stability of TiAlN and nanolayered TiAlN/CrN multilayer films

TiAlN films were deposited on silicon (1 1 1) substrates from a TiAl target using a reactive DC magnetron sputtering process in Ar+N₂ plasma. Films were prepared at various nitrogen flow rates and TiAl target compositions. Similarly, CrN films were prepared from the reactive sputtering of Cr target. Subsequently, nanolayered TiAlN/CrN multilayer films were deposited at various modulation wavelengths (Λ). X-ray diffraction (XRD), energy dispersive X-ray analysis, nanoindentation and atomic force microscopy were used to characterize the films. The XRD confirmed the formation of superlattice structure at low modulation wavelengths. The maximum hardness of TiAlN/CrN multilayers was 3900 kg/mm², whereas TiAlN and CrN films exhibited maximum hardnesses of 3850 and 1000 kg/mm², respectively. Thermal stability of TiAlN and TiAlN/CrN multilayer films was studied by heating the films in air in the temperature range (T_A) of 500-900 °C for 30 min. The XRD spectra revealed that TiAlN/CrN multilayers were stable up to 800 °C and got oxidized substantially at 900 °C. On the other hand, the TiAlN films were stable up to 700 °C and got completely oxidized at 800 °C. Nanoindentation measurements performed on the films after heat treatment showed that TiAlN retained a hardness of 2200 kg/mm² at T_A=700 °C and TiAlN/CrN multilayers retained hardness as high as 2600 kg/mm² upon annealing at 800° C.     

Electrodeposited multilayer films with giant magnetoresistance (GMR): Progress and problems

The giant magnetoresistance (GMR) effect was discovered in 1988 in nanoscale metallic ferromagnetic/non-magnetic (FM/NM) multilayers. By now, devices based on this phenomenon have been widely commercialized which use multilayered structures manufactured via physical deposition (PD) methods, mainly sputtering. It was shown in the early 1990s that electrodeposition (ED) is also capable of producing multilayered magnetic nanostructures exhibiting a significant GMR effect. These layered structures include multilayer films similar to those prepared by PD methods on macroscopic substrates and multilayered nanowires deposited into nanosized template pores, the latter ones being unique to the ED technique. Whereas ED multilayered nanowires can exhibit a GMR effect comparable to the values obtained on PD multilayer films, the GMR values achieved on ED multilayer films still remain inferior to them and, quite often, require high magnetic fields for saturation. Therefore, in spite of the relative simplicity and cost-effectiveness of the ED method, the GMR characteristics of ED multilayer films are still not competitive with the corresponding parameters of their PD counterparts. The main purpose of the present review is to give a summary of the progress achieved over the last one and a half decades on ED multilayer films with GMR effect and to critically evaluate the GMR results reported for various element combinations accessible to the ED technique for the preparation of FM/NM multilayer films (ED multilayered nanowires will be treated very briefly only). In order to promote an understanding of the inferior behavior of ED multilayer films, a detailed discussion of the magnetoresistance effects occurring in bulk homogeneous ferromagnets as well as in magnetic nanostructures (FM/NM multilayers and granular alloys) will be provided. Particular attention will be paid to the case of non-ideal magnetic nanostructures which contain both FM and superparamagnetic (SPM) regions. This is an essential ingredient in explaining the high saturation field of GMR commonly observed in ED multilayer films. In addition to the GMR magnitude, this is another characteristic decisively influencing the magnetic field sensitivity, a key feature concerning applications in sensor devices. The controversial results reported for the spacer layer thickness dependence of GMR in ED multilayer films will also be discussed. It is pointed out that the still inferior GMR characteristics of ED multilayer films can be to a large extent ascribed to microstructural features leading to the appearance of SPM regions, pinholes in the spacer layers and probably not sufficiently perfect interfaces between the FM and NM layers. The origin of the latter deficiency is not yet well understood although it is clearly one of the main causes of a weak interlayer coupling (if there is any coupling at all) and, thus, a small degree of antiparallel alignment leading to a reduced GMR effect. Works will also be described in which attempts were made to produce ED multilayer films with view on possible applications in GMR sensor devices. Finally, problems will be identified which should still be solved in order to make the properties of ED multilayer films attractive for GMR applications.     

Bioactive multilayer thin films of charged N,N-disubstituted hydrazine phosphorus dendrimers fabricated by layer-by-layer self-assembly

Charged N,N-disubstituted hydrazine phosphorus-containing dendrimers are deposited either as alternate all-dendrimers multilayers or alternating with linear polymers on 3-mercaptopropionic acid or 3-aminopropyldimethylethoxysilane coated surfaces via electrostatic layer-by-layer self-assembly. The behavior of the film formation is investigated by surface plasmon resonance spectroscopy and ellipsometry. Fetal cortical rat neurons were cultured on the dendrimer films in order to investigate the influence of the surface charge of the outermost layer on their adhesion and maturation. It was found that neurons attached preferentially and matured slightly faster on film surfaces terminated with positively charged dendrimers than on negatively charged surfaces.     

Studying polymer/fullerene intermixing and miscibility in laterally patterned films with X-ray spectromicroscopy

Films of the fullerene derivatives [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61) BM) and [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71) BM) are patterned on silicon nitride membranes using photolithography to study, with X-ray spectromicroscopy, the lateral, solid-state diffusion of fullerene derivatives into conjugated polymer films. After patterning of the fullerene film, a film of conjugated polymer is laminated on top and the structure is annealed in order to study lateral intermixing and facilitate measurement of fullerene miscibility. Lateral intermixing of polymer and fullerene readily occurs for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) and regiorandom poly(3-hexylthiophene) (RRa-P3HT). A 42 wt.% miscibility of PC(61) BM in PBTTT is measured, while miscibilities of 20 and 41 wt.% are measured for PC(61) BM and PC(71) BM, respectively, in RRa-P3HT, thereby demonstrating a significant difference in the miscibilities of these two fullerene derivatives. For regioregular poly(3-hexylthiophene) (RR-P3HT), incomplete lateral intermixing of fullerene and RR-P3HT is observed with PCBM crystallite formation competing with the lateral diffusion of PCBM molecules into the polymer film.     

Characterization, microstructure, and gas sensitive response behavior of PEG/lithium salt polymer electrolyte films

A composite polymer electrolyte film was prepared by dissolving polyethylene glycol (PEG) with different molecular weight in acetonitrile, and vapor-induced response behavior was investigated upon exposure to various chemical environments. The effect of lithium concentrations on ionic conductivity and response was discussed. The surface microporous structures and vapor sensitive conductivity of the films in the case of poly(vinylidene fluoride) (PVDF) were examined with the PVDF content changed. The crystalline and micro-phase isolation behavior were characterized by a differential scanning calorimeter, an environmental scanning electron microscope, a polarization microscope and a wide-angle X-ray diffraction. The experimental results indicated that PEG/Li⁺ salt composite films exhibited preferential responsive characteristics. The responsivities to ethanoic acid, chloroform, and acetone vapors were enhanced with molecular weight of PEG increased. The conductivity was increased at a higher lithium salt concentration, and also enhanced with PEG content increased, while the responsivities decreased. The formation of microporous structures on the surface of the mixed PEG/PVDF composite films enlarged their specific area and strikingly improved the responsive performances. The changes in conduction behavior were explained from the viewpoint of the swelling and free volume theories as well as a hydrogen bond interaction, combined with the structural and morphological analyses. The introduction of an ionogenic matter also has an important effect on ionic conductivity and responsiveness.     

Nanoscale, phonon-coupled calorimetry with sub-attojoule/Kelvin resolution

We have developed an ultrasensitive nanoscale calorimeter that enables heat capacity measurements upon minute, externally affixed (phonon-coupled) samples at low temperatures. For a 5 s measurement at 2 K, we demonstrate an unprecedented resolution of DeltaC approximately 0.5 aJ/K ( approximately 36 000 k(B)). This sensitivity is sufficient to enable heat capacity measurements upon zeptomole-scale samples or upon adsorbates with sub-monolayer coverage across the minute cross sections of these devices. We describe the fabrication and operation of these devices and demonstrate their sensitivity by measuring an adsorbed (4)He film with optimum resolution of approximately 3 x 10(-5) monolayers upon an active surface area of only approximately 1.2 x 10(-9) m(2).     

Transparent, conducting, and ferromagnetic multilayer films based on ZnO/Fe3O4 by pulsed laser deposition technique

Multilayer thin films based on zinc oxide (ZnO) and iron oxide (Fe₃O₄) are fabricated using pulsed laser deposition method. The structural, electrical, and magnetic properties of these multilayer films are studied. X-ray diffraction study shows that ZnO film is highly oriented along (002) direction, while Fe₃O₄ film has preferred orientation along (222) direction. These films are transparent, conducting, and ferromagnetic at room temperature. The temperature dependence of resistance measurement shows semiconducting nature and charge transportation in these films is due to tunneling. Negative magneto-resistance of 0.28% is observed at room temperature.     

Dielectric polymer matrix composite films of CNT coated with anatase TiO2

This study presents the fabrication method and the dielectric property of polymer matrix composite films of carbon nanotube (CNT) coated with TiO₂. The TiO₂ was coated with sol-gel method using titanium (IV) butoxide (TNBT), HO₂ and benzyl-alcohol as the surfactant. The configuration of CNT-TiO₂ hybrid was observed with the field emission scanning electron microscope images. The coated TiO₂ was thermally treated and transformed into the anatase structure to enhance the mechanical strength and get the high insulating property. The anatase structure was proved from the diffraction angles of XRD. The CNT-TiO₂ hybrid was mixed with the epoxy resin using 3-roll-mil and casted into the films using film casting method. The structure of CNT-TiO₂ hybrid was ascertained to be maintained against the high shear stress during the mixing and casting processes. The dielectric property of the composite films was measured following IPC-TM-6550. The dielectric property at 1 GHz of the composite film of 5 wt.% CNT is about 10 and the loss tangent at 1 GHz is about 0.06.     

Surface modification of titanium substrates with silver nanoparticles embedded sulfhydrylated chitosan/gelatin polyelectrolyte multilayer films for antibacterial application

To develop Ti implants with potent antibacterial activity, a novel “sandwich-type” structure of sulfhydrylated chitosan (Chi-SH)/gelatin (Gel) polyelectrolyte multilayer films embedding silver (Ag) nanoparticles was coated onto titanium substrate using a spin-assisted layer-by-layer assembly technique. Ag ions would be enriched in the polyelectrolyte multilayer films via the specific interactions between Ag ions and –HS groups in Chi-HS, thus leading to the formation of Ag nanoparticles in situ by photo-catalytic reaction (ultraviolet irradiation). Contact angle measurement and field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were employed to monitor the construction of Ag-containing multilayer on titanium surface, respectively. The functional multilayered films on titanium substrate [Ti/PEI/(Gel/Chi-SH/Ag) _n /Gel] could efficiently inhibit the growth and activity of Bacillus subtitles and Escherichia coli onto titanium surface. Moreover, studies in vitro confirmed that Ti substrates coating with functional multilayer films remained the biological functions of osteoblasts, which was reflected by cell morphology, cell viability and ALP activity measurements. This study provides a simple, versatile and generalized methodology to design functional titanium implants with good cyto-compatibility and antibacterial activity for potential clinical applications.