Influence of thin platinum layer on the magnetic properties of multiple layers of CVD cobalt thin films

This paper presents the results obtained on the multiple layers of cobalt (Co)/platinum (Pt) and cobalt (Co)/platinum (Pt)/cobalt (Co) on the oxidised silicon substrate. The cobalt layers were deposited by metal-organic chemical vapour deposition on oxidised-silicon substrates at 450?°C, in H₂ ambient with 2-torr processing pressure. The platinum layers were deposited by E-beam evaporation in a separate vacuum system. The magnetic properties of Co/Pt/Co and Co/Pt multilayer were compared with the single cobalt layers of similar thicknesses on the oxidised silicon substrate. From the hysteresis loops it was observed that thin cobalt layers on oxidised-silicon substrate shows hard magnetic property with coercivity H _c values of 360 Oe and 500 Oe respectively for the 30- and 15-nm cobalt layers. The multiple layers of Co/Pt/Co and Co/Pt of cobalt thickness 15- and 30-nm with platinum 1.5-nm spacer-layer show significant change in magnetic properties (i.e. coercivity H _c and magnetisation M _s ) and, gave soft magnetic properties with H _c values 51 and 49 Oe respectively, which are significantly less than the H _c values of single cobalt layers on oxidised silicon. Also, single and multiple layers cobalt with platinum were annealed and compared with the as-deposited layer structures. From the microstructure analysis by SEM, and AFM it was found that the single and multilayer had similar roughness. Magnetic images were observed by MFM and analyzed in terms of domain structure.     

Optical properties of porous helical thin films

Porous dielectric thin films, composed of isolated helical columns, are fabricated by the glancing angle deposition technique. The selective reflection of circularly polarized light and the optical rotation of linearly polarized light are investigated as a function of film material and helical morphology. The strongest chiral optical response is observed for titanium-dioxide films because of its large refractive index. Optical rotatory powers as high as 4.5 degrees are observed in 830-nm-thick helical films. By tailoring the pitch of the helical columns, the wavelength dependence of the circular reflection band is tuned to preferentially reflect red, green, or blue light, a promising quality for display applications.     

Modulations in effective work function of platinum gate electrode in metal-oxide-semiconductor devices

Reduction in the accumulation capacitance value was more in Si metal-oxide-semiconductor devices than that of Ge metal-oxide-semiconductor devices after a thermal treatment irrespective of the annealing environment. Relatively, thermal treatment in oxygen environment improves the interface quality of HfO₂/Ge stacks considerably, when compared with HfO₂/Si stacks. Whereas, the forming gas annealing at a temperature of 400 °C was not so effective in improving the interface quality at HfO₂/Si stack. The presence of induced negatively charged hydrogen atom in Ge lessens the Fermi level pinning at HfO₂ and Ge interface.     

Effect of platinum distribution on the hydrogen gas sensor properties in tin oxide thin films

Tin oxide and platinum layers were deposited on oxidized silicon wafers by ion-beam sputtering. The hydrogen gas sensing properties of undoped films and platinum-doped films were examined at 300°C for films annealed at 500°C. It was observed that the surface platinum when annealed together with the tin oxide film increased the sensitivity and reduced the response time compared with those of undoped films. Longer annealing tended to shift the optimum sensor thickness to a thicker side; the optimum thickness changed from 17 to 37 nm as the annealing time increased from 2 to 50 h. The interdiffusivity between the platinum and the tin atoms in the bulk was negligibly small at 300°C.     

Dielectric properties of KDP filled porous alumina nanocomposite thin films

A new concept of a composite dielectric thin film fabrication is presented. The fabrication process consists of two stages. The first stage is anodizing a thin aluminum film to produce a porous alumina film that contains an array of nanometer sized parallel pores. The second stage is filling the pores with a saturated KDP (KH2PO4) liquid solution due to capillary forces. After drying KDP nanocrystals are formed inside the pores. This process results in a formation of a composite dielectric thin film composed of the alumina pores walls as one dielectric material and the KDP nanocrystals inside the pores as another dielectric material. The dielectric permittivity of this composite film is higher than that of the porous alumina film at all applied frequencies. The dielectric enhancement is more pronounced at low frequencies due to an interface polarization mechanism. This fabrication process enables controlling the size, composition, and microstructure of the composite dielectric film constituents and thus changing its dielectric properties over a wide range of values.     

Electrical conductivity in thin and very thin platinum films

The two-photon transition probability between electron energy bands in a semiconductor film is discussed, taking quantum size effects into account. An expression for the absorption rate of one of the two photons is given as a function of the frequency corresponding to all the types of critical points. The anisotropy of non-cubic materials is taken into account. The numerical calculation of the absorption coefficient is performed for the case of ZnS near the extremal point.     

Polymetallated porphyrin ultrathin films as transducing elements for molecular devices and logic gates

Meso-tetrapyridylporphyrins peripherally coordinated to four ruthenium complexes, such as [Ru(bpy)2Cl] and [Ru(5-ClPhen)2Cl] (bpy = 2,2'-bipyridine; Phen = 1,10-phenanthroline), provide a versatile class of molecular materials in which the complexes act as co-factors, inducing electronic effects and acting as electron-transfer relays and electron pools or sinks, depending upon their oxidation state. These cationic porphyrins can be assembled into thin films by conventional methods, or into organized layer-by-layer structures by combining with negatively charged tetrasulfonated porphyrins or phthalocyanines. Their electrocatalytic and photoelectrochemical properties have been successfully exploited in chemical sensors. Their usefulness in molecular logic gates are being demonstrated by using modified transparent conducting electrodes in miniaturized flow injection cells. In such designs, the chemical, electrochemical, and light inputs can be readily combined to perform the basic logic functions, such as AND, OR, and NOT, for molecular computing.     

Optical properties of porous anodic aluminum oxide thin films on quartz substrates

Porous anodic aluminum oxide (AAO) thin films on quartz substrates were fabricated via evaporation of a 100-nm thick Al, followed by anodization with different durations and pore widening and Al removal by chemical etching. The transmittance and reflectance of AAO films on quartz substrates were measured by optical spectrophotometry. The microstructure and morphology were examined by scanning electron microscopy. The pore diameter of AAO films after pore widening and Al removal is 60 ± 4 nm and the interpore distance is 88 ± 5 nm. It is found that the reflectance decreases and the transmittance increases with the increase of the anodization time and pore widening. Compared to a bare substrate, the transmittance of AAO films after pore widening and Al removal is about 3.0% higher, while the reflectance is about 3.0% lower over a wide wavelength range. Additionally, after pore widening and Al removal, when AAO films are prepared on both sides of the quartz substrate, the highest transmittance is about 99.0% in the wavelength range 570-680 nm. The optical constants and thickness of AAO films after pore widening and Al removal were retrieved from normal incidence transmittance data. Results show that the refractive index is lower than 1.25 in the visible optical region and that the porosity is about 0.70.     

Effect of platinum doping on the structural and electrical properties of SnO2 thin films

The investigation of Pt doping effect on the structural and electrical properties of SnO₂ thin films was aimed in this study. For this purpose, the polycrystalline pure and Pt-doped SnO₂ thin films were deposited onto n-type silicon substrate and the Pt sputter power was varied as 0 (un-doped), 2, 5 and 7 W by using radio frequency confocal sputtering system. The structural properties of the samples were analysed by X-ray diffraction measurements. The structural results show that the 5 W Pt-doped SnO₂ sample has better crystallinity than the other samples. The results of the electrical measurements as current–voltage, capacitance–voltage and conductance–voltage were also obtained and discussed in detail for fabricated diodes. The analysis of electrical characteristics shows that the use of different Pt doping has significant effect on electrical properties of such devices. The study also provides an improved supplemental understanding to the related technologies which use Pt-doped SnO₂ materials.     

Influence of the substrate nature on the properties of ZnO thin films

Zinc metallic films, deposited onto different substrates, were submitted to a thermal oxidation process, in air, in order to obtain ZnO thin films. X-ray diffraction patterns revealed that as-obtained ZnO thin films were polycrystalline and have a wurtzite (hexagonal) structure. The temperature dependences of the electrical conductivity during some heating/cooling cycles were studied and the conduction mechanism was interpreted in terms of Seto model. The sensitivity of ZnO thin films, at five gases, was investigated and it was established that ethanol is the test gas that produces the most significant changes in the electrical resistance of all the studied films. Some correlations between the oxidation temperature and the substrate nature and the parameters which characterize the structural and electrical properties of ZnO thin films have been established.     

Influence of surface wettability on the cathodic electroluminescence of porous silicon

It is shown that the wettability of porous silicon influences the efficiency of its cathodic electroluminescence in electrolytes. A model is proposed to explain the nature of the electroluminescence in a system consisting of porous silicon and an oxidizing electrolyte. Pis’ma Zh. Tekh. Fiz. 23, 58–63 (January 12, 1997)     

Influence of hydrogen annealing on the properties of hafnium oxide thin films

Thin films of hafnium oxide were deposited by electron beam evaporation, and were subsequently annealed in hydrogen. X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, photoluminescence, spectrophotometry, and current–voltage measurements were performed to investigate the structural, chemical, optical, and electrical properties of the films. As-deposited films were amorphous and nearly stoichiometric. Annealing led to crystallization of the films, and reduction of stoichiometry. Photoluminescence measurements revealed the presence of oxygen-related defects. Optically, the films were transparent with a wide band gap, and this was not affected by hydrogen annealing. Moreover, the films were suitable as anti-reflection coatings on silicon. The electrical resistivity of the films was significantly reduced as a result of annealing.     

Influence of iodine on the electrical properties of nickel phthalocyanines thin film devices

The electrical properties of pure Nickel Phthalocyanine (Ni Pc) thin films and iodine doped Ni Pc thin films with Gold and Aluminium electrode sandwiched devices have been investigated. The electrical properties and the various electrical parameters of the pure and iodine-doped films have been estimated and compared from the analysis of the current density characteristics. From our study we find that the iodine doping enhanced the electrical conductivity compared to pure Nickel Phthalocyanine and the conduction mechanism is much improved with the iodine doping. Interestingly these films after iodine doping showed remarkably increased electrical conductivity nearly ten times that of pure Phthalocyanine. This may be accounted for by the decrease in the metal-metal bond distance. At low voltages the film shows an ohmic conduction whereas at higher voltage levels the conduction is dominated by space charged limited conduction. Further the reverse conduction mechanisms have also been investigated for this sandwiched device. From the current limitations in the reverse condition a strong rectifying behaviour is evident.     

Influence of the substrate temperature on the properties of MoSi2 thin films

Investigations of the microcrystalline structure of sputtered MoSi₂ thin films deposited at temperatures in the range 60–500 °C are described. At low temperatures the films are amorphous, and in the higher range of temperature hexagonal MoSi₂ is detected. Annealing the films at 960 °C to form the low resistivity tetragonal MoSi₂ phase results in different grain sizes depending on the substrate temperature during deposition.     

Solid-state photochemistry of platinum(II) methylazide complexes as thin films on Si (111) surfaces: photolithography of platinum films

The solid-state photochemistry of L₂Pt(Me)(N₃) (L=PPh₃, PEt₃, dppe/2) have been investigated on Si (111) surfaces. Photolysis of an amorphous thin film of L₂Pt(Me)(N₃) results in the loss of all ligands. This occurs via a single photon process with no detectable thermally stable intermediate. The resultant films are primarily platinum metal although some phosphine-containing impurity remains. The final analysis leads to formulations of the films as Pt(dppe)_0.06, Pt(PPh₃)_0.12 and Pt(PEt₃)_0.07. The thicknesses of the platinum films ranged from 150 nm to less than 25 nm. This process was shown to be compatible with standard lithography methods by the production of 3 μm wires on Si (111) by photolithography.     

Influence of gamma radiation on the optical properties of ZnSe nanocrystalline thin films

The effect of gamma (γ) irradiation on the absorption spectra and the optical energy bandwidth of ZnSe nanocrystalline thin films have been studied. Thin films of different thicknesses from 20 to 120 nm were deposited by Inert gas condensation technique at constant temperature of 300 K and under pressure 2 × 10⁻³ Torr of Argon gas flow. The optical transmission (T) and optical reflection (R) in the wavelength range 190–2,500 nm of ZnSe nanocrystalline thin films were measure for unirradiated and irradiated films. The dependence of the absorption coefficient α on photon energy hν was determined for different γ-doses irradiated films. The ZnSe thin films show direct allowed interband transition by γ-doses. Both the absorption coefficient (α) and optical energy bandwidth were found to be γ-dose dependent. The optical energy band width has been decreased by irradiated of γ-doses. The E_gn values of irradiated thin films by 34.5 Gy of γ-doses were recovered to nearly their initial values after 100 days at 300 K.     

张应力对FeCoSiB非晶薄膜磁特性的影响

采用磁控溅射方法,在弯曲的玻璃基片上制备出受张应力作用的FeCoSiB非晶薄膜,研究了张应力大小对FeCoSiB薄膜的磁畴、矫顽力、剩磁、各向异性场等磁特性的影响.结果表明,薄膜的畴结构显著依赖于张应力,其磁畴宽度随张应力增加而增加;张应力导致FeCoSiB薄膜内形成较强的磁各向异性,其各向异性随应力的增大而增大.     

Influence of deposition temperature on the properties of sprayed CuInS2 thin films

Copper indium disulfide films were deposited by chemical spray pyrolysis technique at different deposition temperatures. Deposition temperature was explored to understand how it affects the crystallography, stoichiometry, morphology, optical and electrical properties of the deposited films. The chemical composition of the films evaluated by energy dispersive X-ray spectroscopy revealed the presence of copper, indium and sulfur elements in the films. Also it was observed that films formed at higher temperatures are copper rich and also showed deficiency of sulfur. X-ray diffraction patterns showed that the sprayed CuInS₂ films are polycrystalline with chalcopyrite structure and preferred orientation in the (112) direction. Atomic force microscope studies revealed significant variations in the surface morphology of the prepared films with different deposition temperature. An increase in the energy band gap was observed with increasing the deposition temperatures. The temperatures dependence of conductivity of CuInS₂ thin films, determined in the temperature range of 225–400?K, showed their semiconducting behavior.