Growth and Atomic-Scale Characterization of Ultrathin Silica and Germania Films: The Crucial Role of the Metal Support

The present review reports on the preparation and atomic-scale characterization of the thinnest possible films of the glass-forming materials silica and germania. To this end state-of-the-art surface science techniques, in particular scanning probe microscopy, and density functional theory calculations have been employed. The investigated films range from monolayer to bilayer coverage where both, the crystalline and the amorphous films, contain characteristic XO₄ (X=Si,Ge) building blocks. A side-by-side comparison of silica and germania monolayer, zigzag phase and bilayer films supported on Mo(112), Ru(0001), Pt(111), and Au(111) leads to a more general comprehension of the network structure of glass former materials. This allows us to understand the crucial role of the metal support for the pathway from crystalline to amorphous ultrathin film growth.     

A Highly Sensitive and Selective Non-enzymatic Hydrogen Peroxide Sensor Based on Nanostructured Co3O4 Thin Films Using the Sol-gel Method

In this work we report an easy and efficient way to fabricate nanostructured cobalt oxide (Co₃O₄) thin films as a non-enzymatic sensor for H₂O₂ detection. Co₃O₄ thin films were grown on ITO glass substrates via the sol-gel method and characterized with several techniques including X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorbance. The Co₃O₄ thin films’ performance regarding hydrogen peroxide detection was studied in a 0.1 M NaOH solution using two techniques, cyclic voltammetry (CV) and amperometry. The films exhibited a high sensitivity of 1450 μA.mM⁻¹.cm⁻², a wide linear range from 0.05 μM to 1.1 mM, and a very low detection limit of 18 nM. Likewise, the Co₃O₄ thin films produced showed an exceptional stability and a high selectivity.     

Analytical analysis of anisotropic thermophoresis of a charged spheroidal colloid in aqueous media for extremely thin EDL cases

Thermophoresis of charged spheroids has been widely applied in biology and medical science. In this work, we report an analysis of the anisotropic thermophoresis of diluted spheroidal colloids in aqueous media for extremely thin EDL cases. Under the boundary layer approximation, we formulate the thermophoretic velocity, the thermophoretic force, and the thermodiffusion coefficient of a randomly dispersed spheroid. The parametric studies show that under the aforementioned conditions, the thermophoresis is anisotropic and its thermodiffusion coefficient should be considered as a vector, D _T. The thermodiffusion coefficient values and directions of D _T are strongly related to the aspect ratio and the angle θ between the externally applied temperature gradient and the particle's axis of revolution: The increasing aspect ratio enlarges the thermodiffusion coefficient value D_T of prolate (oblate) spheroids to a constant value when θ < 60° (θ > 45°), and it reduces D_T of prolate (oblate) spheroids to a constant value when θ > 60° (θ < 45°). The thermodiffusion coefficient direction of both prolate and oblate spheroids deviates slightly from −∇T_∞ for a small aspect ratio, and such deviation becomes serious for a large aspect ratio.     

The Effect of Growth Parameters on Electrophysical and Memristive Properties of Vanadium Oxide Thin Films

We have experimentally studied the influence of pulsed laser deposition parameters on the morphological and electrophysical parameters of vanadium oxide films. It is shown that an increase in the number of laser pulses from 10,000 to 60,000 and an oxygen pressure from 3 × 10⁻⁴ Torr to 3 × 10⁻² Torr makes it possible to form vanadium oxide films with a thickness from 22.3 ± 4.4 nm to 131.7 ± 14.4 nm, a surface roughness from 7.8 ± 1.1 nm to 37.1 ± 11.2 nm, electron concentration from (0.32 ± 0.07) × 10¹⁷ cm⁻³ to (42.64 ± 4.46) × 10¹⁷ cm⁻³, electron mobility from 0.25 ± 0.03 cm²/(V·s) to 7.12 ± 1.32 cm²/(V·s), and resistivity from 6.32 ± 2.21 Ω·cm to 723.74 ± 89.21 Ω·cm. The regimes at which vanadium oxide films with a thickness of 22.3 ± 4.4 nm, a roughness of 7.8 ± 1.1 nm, and a resistivity of 6.32 ± 2.21 Ω·cm are obtained for their potential use in the fabrication of ReRAM neuromorphic systems. It is shown that a 22.3 ± 4.4 nm thick vanadium oxide film has the bipolar effect of resistive switching. The resistance in the high state was (89.42 ± 32.37) × 10⁶ Ω, the resistance in the low state was equal to (6.34 ± 2.34) × 10³ Ω, and the ratio R_HRS/R_LRS was about 14,104. The results can be used in the manufacture of a new generation of micro- and nanoelectronics elements to create ReRAM of neuromorphic systems based on vanadium oxide thin films.     

A low-temperature X-ray diffraction study of the Cu2ZnSnSe4 thin films

Low-temperature XRD measurements were performed to confirm the phase composition and structural parameters of the electrochemically deposited Cu₂ZnSnSe₄ thin films on flexible metal substrates.     

聚苯乙炔LB多层膜及其光电导性能的研究

制备了聚苯乙炔（ＰＰＡ）ＬＢ多层膜，将其作为电荷产生层首次应用于机能分离型光电导体领域．从π Ａ曲线发现，ＰＰＡ单分子膜具有表面压力的各向异性和松弛特性．ＴＥＭ照片显示，ＰＰＡ分子链在ＬＢ膜中有序排列．转移比和ＸＰＳ的研究表明，复合膜沉积均匀．与ＰＰＡ涂膜相比，以ＰＰＡ ＬＢ多层膜作为电荷产生层的光电导体表面充电电位Ｖ０＝１３４５Ｖ，光照１ｓ后的光衰百分比ΔＶ１ｓ＝６５０５％，半衰时间ｔ１／２＝０５８ｓ，具有更优异的光电导性能．     

COMPENSATION EFFECT OF POLYIMIDE THIN FILMS ON NORMALLY WHITE TWISTED NEMATIC LIQUID CRYSTAL DISPLAYS

The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin filmswere used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratiosand enlarge viewing angles was explained in this paper. A certain polyimide thin film wastaken as an example to show compensation effect on NW-TN-LCD.     

BARRIER PROPERTIES OF VINYLIDENE CHLORIDE/METHYL ACRYLATE COPOLYMER

A series of vinylidene dichloride (VDC) copolymers with methyl acrylate (MA) ascomonomer (3--12wt%), was prepared by free-radical suspension copolymerization. Thepermeability coefficients of the copolymers to oxygen and carbon dioxide were measured at1.0 MPa and at 30℃, and those to water vapor were measured at 30℃ and 100% relativehumidity All the VDC/MA copolymers studied are semicrystalline. As the MA contentincreases, the permeability coefficients of the copolymers to oxygen, carbon dioxide, andwater vapor are progressively increased, caused by decrease in crystalline fraction andincrease in free volume of VDC/MA copolymers.     

有机/无机异质结薄膜发光二极管

聚合物发光二极管（LED）自从Burrou吵es等于1990年首次报导PPV的电致发光［‘］以来，由于聚合物半导体具有热和化学性能的稳定，克眼了有机小分子材料容易晶化的优点，在平板显示领域必将占有一席之地，从而吸引了许多科学家投身到这一领域来．众所周知，要想实现LED的实用化     

Thermal diffusivity of polymer films by pulsed photothermal radiometry

We have developed a pulsed photothermal radiometry technique for determining the thermal diffusivity parallel to the surface of a polymer film that involves flashing a line-shaped laser beam on the surface of the sample at right angle to its length, and monitoring the temperature change with time at a distance from the line source using an infrared detector. Combining this with our previous laser-flash radiometry method for thermal diffusivity measurement perpendicular to the film surface, we can now measure the thermal diffusivity of a polymer film along all directions. These two techniques have been used to study uniaxially and biaxially oriented poly(ethylene terephalate) and uniaxially drawn ultrahigh molecular weight polyethylene films. For uniaxially oriented poly(ethylene terephalate), the thermal diffusivity along the draw direction is substantially higher than that in the transverse direction, which in turn, is slightly higher than that in the thickness direction. For a polyethylene film with a draw ratio of 200, the axial thermal diffusivity is extremely high, being about five times that of stainless steel. The anisotropy of the thermal diffusivity of this film exceeds 90. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1621–1631, 1997