Spectra of optical characteristics of titanium with a binary surface layer

The solution of the inverse problem of spectral ellipsometry is obtained for titanium with a surface layer of titanium oxide that was formed as a result of thermal (450°C) oxidation of the metal substrate. Using the Drude-Zener and Cauchy dispersion models, it is shown that a rather thick (46 nm) inhomogeneous binary surface layer including about 23% of titanium and 77% of titanium oxide is present on the studied samples of pure polycrystalline titanium. A natural weakly absorbing surface layer with a thickness of 13 nm is on this layer.     

Self-cleaning characteristics on a thin-film surface with nanotube arrays of anodic titanium oxide

Self-cleaning of a surface of nanotube arrays of anodic titanium oxide (ATO) is demonstrated. The ATO was prepared in fluoride ion containing sulfate electrolytes with a structure of 0.4 μm length, 100 nm pores diameter, 120 nm interpore distance, 25 nm pore wall thickness, a 8×10⁹ pores cm⁻² pore density, and 68.2% porosity. Prepared as thin films either directly from a Ti foil or on a glass substrate, these arrays have the property that water drops spread quickly over the surface of the films without irradiation. In contrast, a flat anatase TiO₂ film requires irradiation with UV light for several minutes before the contact angle decreases to zero. The observed self-cleaning behavior of the ATO thin films is due to the capillary effect of the nanochannel structure and the superhydrophilic property of the anatase TiO₂ surface inside the tube.     

Photoreactive titanium oxide layer prepared from a titanium naphthenate

Highly transparent titanium oxide thin films were prepared on soda-lime–silica slide glass substrates from a titanium naphthenate precursor. Films prefired at 500 °C for 10 min were finally heat treated at 500 °C for 30 min in air. Crystallinity of the films was analyzed by high resolution X-ray diffraction analysis. A sharp absorption edge of the TiO₂ film was observed. The estimated energy band gap for the film is larger than that of single crystal TiO₂.     

Structural and electrical characteristics of a hyperdoped silicon surface layer with deep donor sulfur states

Inhomogeneous hyperdoping of a 100-nm-thick silicon surface layer with sulfur atoms at concentrations above 2 × 10²¹ cm^?3 was obtained via its femtosecond laser ablation in a sulfur-containing organic solvent. Infrared transmission spectroscopy reveals distinct interband absorption peaks of donor sulfur states, which are absent in the initial crystalline silicon, and a broad absorption band of free carriers with a concentration of ～10¹⁸ cm^?3. The rather low free-carrier concentration is related to equilibrium room-temperature ionization of localized donor sulfur states, preserving their nondegenerate character owing to the strong electronion binding in the donor states.     

Optical polarization characteristics for AlGaN-based light-emitting diodes with AlGaN multilayer structure as well layer

The optical properties of AlGaN-based quantum well(QW) structure with two coupled thin well layers are investigated by the six-by-six K-P method.Compared with the conventional structure,the new structure,especially the one with lower Al-content in the barrier layer,can enhance the TE-/TM-polarized total spontaneous emission rate due to the strong quantum confinement and wide recombination region.For the conventional QW structure,the reduction of well thickness can lead the degree of polarization(DOP) to decrease and the internal quantum efficiency(IQE) to increase.By using the coupled thin well layers,the DOP for the structure with high Al-content in the barrier layer can be improved,while the DOP will further decrease with low Al-content in the barrier layer.It can be attributed to the band adjustment induced by the combination of barrier height and well layer coupling.The IQE can also be further enhanced to 14.8%-20.5% for various Al-content of barrier layer at J=100 A/cm~2.In addition,the efficiency droop effect can be expected to be suppressed compared with the conventional structure.     

Formation of titanium carbide layer by laser alloying with a light-transmitting resin

The weight reduction of mechanical components is becoming increasingly important, especially in the transportation industry, as fuel efficiency continues to improve. Titanium and titanium alloys are recognized for their outstanding potential as lightweight materials with high specific strength. Yet they also have poor tribological properties that preclude their use for sliding parts. Improved tribological properties of titanium would expand the application of titanium into different fields.Laser alloying is an effective process for improving surface properties such as wear resistance. The process has numerous advantages over conventional surface modification techniques. Many researchers have reported the usefulness of laser alloying as a technique to improve the wear resistance of titanium. The process has an important flaw, however, as defects such as cracks or voids tend to appear in the laser-alloyed zone.Our group performed a novel laser-alloying process using a light-transmitting resin as a source for the carbon element. We laser alloyed a surface layer of pure titanium pre-coated with polymethyl methacrylate (PMMA) and investigated the microstructure and wear properties. A laser-alloyed zone was formed by a reaction between the molten titanium and thermal decomposition products of PMMA at the interface between the substrate and PMMA. The cracks could be eliminated from the laser-alloyed zone by optimizing the laser alloying conditions. The surface of the laser-alloyed zone was covered with a titanium carbide layer and exhibited a superior sliding property and wear resistance against WC-Co.     

Surface characteristics and in vitro biocompatibility of a manganese-containing titanium oxide surface

This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating the manganese ions (Mn) obtained by hydrothermal treatment with the expectation of utilizing potent integrin-ligand binding enhancement effect of Mn for future applications as an endosseous implant surface. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, optical profilometry and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The in vitro biocompatibility of the Mn-containing Ti oxide surface was evaluated in comparison with untreated bare Ti using a mouse calvaria-derived osteoblastic cell line (MC3T3-E1). The hydrothermal treatment produced a nanostructured Mn-incorporated Ti oxide layer approximately 0.6 μm thick. ICP-AES analysis demonstrated that the Mn ions were released from the hydrothermally treated surface into the solution. Mn incorporation notably decreased cellular attachment, spreading, proliferation, alkaline phosphatase activity, and osteoblast phenotype gene expression compared with the bare Ti surface (p < 0.05). The results indicate that the Mn-incorporation into the surface Ti oxide layer has no evident beneficial effects on osteoblastic cell function, but instead, actually impaired cell behavior.     

Optical characteristics of particles produced using electroerosion dispersion of titanium in hydrogen peroxide

Titanium oxide particles are produced using electric-discharge dispersion of titanium in aqueous solution of hydrogen peroxide. Electron vacuum microscopy, X-ray diffraction, and diffuse reflection spectroscopy are used to study the morphology, composition, and optical characteristics of the erosion particles. It has been demonstrated that the particles consist of titanium and titanium oxides with different valences. The edge of the optical absorption is located in the UV spectral range. The band gap is 3.35 eV for indirect transitions and 3.87 eV for direct allowed transitions. The band gap decreases due to the relatively long heating in air at a temperature of 480–550°C, so that powder oxide compositions can be obtained, the optical characteristics of which are similar to optical characteristics of anatase. The erosion products are completely oxidized to rutile after annealing in air at a temperature of 1000°C.     

Optical bistability of a thin layer of a substance with quasiresonance polarizability components

Optical-bistability conditions for a thin (smaller than the wavelength of the acting laser radiation) surface layer of resonance atoms are calculated with allowance for the influence of the polarizing fields of transitions adjacent to the resonance one and allowed in the electrodipole approximation on the transmissivity of the medium of the layer. It is noted that the change in the threshold bistability characteristics is due to the influence of the self-modulation broadening of the line of the laser field occurring in the thin resonancepolarized layer on the effective level of its absorption. Institute of Applied Optics, National Academy of Sciences of Belarus, 11, Byalynitskii-Birulya Str., Mogilev, 212793, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 661–665, September–October, 1999.     

The effect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D(³He,p)⁴He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N₂ gas at 650°C. Deuterium loading was performed by exposure to 1 Torr of D₂ gas at 500°C. The deuterium distribution was influenced by nitrogen in the near-surface regions of all samples. Specifically, deuterium solubility was suppressed in surface regions of high (greater than 1%) nitrogen concentration. The deuterium solubility also remained low within the first few microns, well beyond the region of high nitrogen concentration. This effect is attributed to internal elastic stresses imposed by the non-deuterium absorbing nitrogen-rich layer on the Ti. These stresses prohibit the volume expansion associated with deuterium absorption. We estimate stresses on the order of 3–4 GPa are required to suppress the deuterium solubility to the values observed. The deuterium absorption kinetics were observed to depend systematically on the thickness of the nitrogen-rich layer. This is consistent with limited solubility near the surface or a surface poisoning effect influencing the overall deuterium diffusion from the gas phase into the Ti bulk.     

Optical characteristics of uniaxial polyester films with the optical axis perpendicular to the surface

The functions of the main indices of refraction n(ν) and absorption κ(ν) of uniaxial thin polyethylene terephthalate films have been calculated by the experimental spectra of frustrated total reflection of s-and p-polarized radiation in the 700–760-cm⁻¹ range. The κ_o(ν) maximum falls at the the 727-cm⁻¹ frequency and the maximum of κ_e(ν) falls at the the 724-and 732-cm^{− 1} frequencies. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 756–759, November–December, 2005.     

Surface modes of a degenerate polar pomiconductor with a surface depletion layer

Surface polariton modes of a degenerate semiconductor which has a low carrier concentration surface layer are studied in the hydrodynamic approximation. In particular, the effect of the polar phonons on the higher multipole excitats of the surface is analyzed in the long wavelength non-retarded limit.     

Memristive effect in a nanotubular layer of anodized titanium dioxide

A layer of titanium dioxide (TiO₂-NT) nanotubes 500 nm thick with average diameters of 60 nm is grown via anodizing. Memristive behavior typical of synthesized Ti/TiO₂-NT/Au structures is observed in full cycles of resistive switching, and during the multiple reading of data. Impedance in the states of low (R _LRS ≈ 3 Ohm) and high (R _HRS ≈ 180 Ohm) resistance are estimated for the obtained memristors.     

Optical control of the mobility of a MODFET with a layer of self-assembled quantum dots

We report an experimental study of GaAs/Al_0.33Ga_0.67As modulation doped field effect (MODFET) transistors, in which an InAs layer of self-assembled quantum dots is placed in one of the Al_0.33Ga_0.67As barrier layers close to the two-dimensional electron gas (2DEG). We find the source–drain resistance is bistable with the two states controlled by illumination and applied gate bias. Brief illumination induces a large, persistent drop in the resistance, which can be recovered by applying a positive gate bias. Magneto-transport measurements show that while illumination causes only a relatively small change in the 2DEG density, it can greatly enhance its mobility. We suggest this is because the 2DEG mobility is limited by percolation of the electrons through the rough electrostatic potential induced by the charged dots. Illumination reduces the negative charge trapped in the dots, thus smoothing the conduction band potential, which produces a large increase in the mobility.     

Statistical characteristics of a wave propagating through a layer with random irregularities

Statistical characteristics of a wave propagating through a layer with random irregularities are investigated by a simulation procedure. The investigation is carried out within the geometrical optics approximation in its validity range. It is shown that when the irregular layer is a long distance from the source and observer, a significant role in the formation of eikonal (phase path) fluctuations is then played by trajectory fluctuations in regions of the propagation medium, free from irregularities before and after the irregular layer. With these variations taken into account, which are neglected in conventional perturbation theory, we obtained approximate expressions for the dispersion and the correlation function of the eikonal. We investigate the behaviour of the eikonal dispersions, the angles and correlation functions of the eikonal and field for different disturbances of the medium, and for different distances of the receiver and transmitter from the layer boundaries.     

钛合金表面激光熔覆TiC_p/Ni基合金复合耐磨涂层

采用激光熔覆技术在TC4合金表面制备TiC颗粒增强的Ni基合金复合材料涂层,测试了熔覆层的硬度和滑动摩擦磨损性能,分析了熔覆层的强化机制。结果表明,熔覆层中存在颗粒强化、固溶强化和细晶强化等多种强化作用,熔覆层的显微硬度达HV900～1100,耐磨性能比TC4合金显著提高。     

Optical characteristics of subwavelength metallic grating coupled porous film surface plasmon resonance sensor with high sensitivity

A high performance sub-wavelength metallic grating coupled surface plasmon resonance (SWMGCSPR) sensor with metal and porous composite layer is proposed. Rigorous coupled-wave analysis (RCWA) is conducted to prove the design feasibility, characterize the sensor's performance and determine geometric parameters of the structure, which is also employed to compute the electromagnetic (EM) field distributions at the resonant wavelengths. Parameters of sensing platform are optimized to achieve the best performance of the SPR sensor. Obtained results reveal that the proposed structure can excite SPR with negative diffraction order of SWMG. Both wavelength and angular sensitivities are greatly enhanced because surface plasmon wave (SPW) exhibits a large penetration depth which will enlarge the distance of interactions between SP and analytes. The detection sensitivities and quality parameters are estimated to be 700 nm/RIU and 509°/RIU with full width at half maximum (FWHM) less than 2.5 nm using the same optimized structure.