FABRICATION OF DIAMOND TUBES IN BIAS-ENHANCED HOT-FILAMENT CHEMICAL VAPOR DEPOSITION SYSTEM

Deposition of diamond thin films on tungsten wire substrate with the gas mixture of ace- tone and hydrogen by using bias-enhanced hot filament chemical vapor deposition(CVD)with the tantalum wires being optimized arranged is investigated.The self-supported diamond tubes are ob- tained by etching away the tungsten substrates.The quality of the diamond film before and after the removal of substrates is observed by scanning electron microscope(SEM)and Raman spectrum.The results show that the cylindrical diamond tubes with good quality and uniform thickness are obtained on tungsten wires by using bias enhanced hot filament CVD.The compressive stress in diamond film formed during the deposition is released after the substrate etches away by mixture of H_2O_2 and NH_4 OH.There is no residual stress in diamond tube after substrate removal.     

Oxide ion/electronic polarizability,optical basicity and linear dielectric susceptibility of TeO2 – B2O3 – SiO2 glasses

A system of bio-silica borotellurite glasses was fabricated based on the chemical formula [(TeO₂)_0.7 (B₂O₃)_0.3]_1-x (SiO₂)_x with x = 0.1, 0.2, 0.3, and 0.4 using the melt-quenching technique using silica (98.548% SiO₂, from rice husk), TeO₂ (Alfar Aeser, 99.9%) and B₂O₃ (Alfar Aeser, 99.9%). Measurements and characterizations such as density and molar volume measurements, XRD analysis, FTIR, and UV–Vis spectroscopes were performed on the studied glasses. The objective was to determine the glasses’ applicability in optoelectronics, non-linear optics, and laser technologies through polarizability, linear electric susceptibility, and optical basicity study. Apart from confirming the amorphous nature of the glasses, the XRD analysis identified the presence of a crystalline phase of tellurium oxide (α-TeO₂) formed. The FTIR spectral study revealed the presence of TeO₃, BO₃, and SiO₄ structural units in the studied glasses. The refractive index (2.3026 – 2.2651), molar polarizability (8.0696 – 9.4334 Å³), oxide ion polarizability (3.2970 – 3.6202 Å³), electronic polarizability (0.2296 – 0.2335 Å³), dielectric constant (5.1307 – 5.3019), optical basicity (0.6719 – 0.7998), metallization criterion (0.410853 – 0.420714) and electric susceptibility (0.3286 – 0.3422 esu) of the glasses were presented. With the high refractive index and favourable electronic/oxide ion polarizability as well as good electric susceptibility, the glasses have shown great potential for optical fibre and laser applications. Metallization criterion value falls in the range of glasses with great potentials for non-linear optical application. The dielectric value suggests the glasses represent wideband semiconducting glasses believed to be good for application in microelectronic substrates fabrication.     

Performance enhancement of nanofiltration membranes via surface modification with a novel acylation reagent

Acyl chloride monomers have been serving as the dominant acylation reagent for preparing thin-film composite (TFC) nanofiltration (NF) membranes over the past few decades. Herein, a novel acylation reagent (trimellitic anhydride, TMA) was exploited in conjunction with trimesoyl chloride (TMC) to undergo interfacial polymerization with piperazine (PIP) on the polysulfone substrate membranes. The introduction of TMA enabled the deeper diffusion of PIP monomers into the organic phase, resulting in the creation of novel circular-shaped protuberances on the top surface of the polyamide layer and the significant increase in the effective membrane area. Besides, abundant in-situ carboxylic groups were generated in the polyamide layer, conducive to both the surface hydrophilicity and negative charge density. Consequently, with an addition of 0.03 wt% TMA, pure water flux reached up to 15.3 L m⁻² hour⁻¹ bar⁻¹, almost 2.2 times that of the pristine membrane, and high rejection of Na₂SO₄ (97.3%) was maintained, evincing the superior desalination performance of the TMA-modified membranes. The interaction mechanism between TMA, TMC, and PIP was described in detail. Furthermore, the TMA-modified membranes exhibited a stable separation performance over the long-running process.     

Photocatalytic activities of Ion doped TiO2 thin films when prepared on different substrates

Pure and ion doped TiO₂ thin films were prepared by sol-gel dip coating process on metallic and non-metallic substrates. Test metal ion concentration ranged from 0.000002 to 0.4 at.%. The resulting films were annealed in air and characterized by optical spectroscopy and X-ray diffraction. The photodegradation of methyl orange under UV irradiation by pristine and ion-doped TiO₂ films was quantified in a photocatalytic reactor developed in this study. In general, both doped and undoped TiO₂ crystals appeared in anatase phase and the photocatalytic activities of the TiO₂ thin films varied with substrates, calcination temperature, doping ions and their concentrations. The best calcination temperature for different substrates ranged from 450 to 580 °C. Films prepared on the metallic substrates resulted in higher photocatalytic activities, while ion doping lowered their efficiencies. On the contrary, for non-metallic substrates except ceramic the photocatalytic efficiencies of undoped films were much lower (< 30%), while ion doping was shown to increase the photocatalytic efficiencies remarkably in some cases, e.g., Cr³⁺ with the tile substrate. Overall, ion doping affected the photocatalytic efficiency of TiO₂ films, and an optimal doping concentration of between 0.0002 and 0.002 at.%, close to an estimate by the Debye length equation, resulted in the highest efficiency for most substrates.     

Preparation and microwave dielectric properties of 3ZnO·B2O3 ceramics with low sintering temperature

The preparation and dielectric properties of 3ZnO·B₂O₃ ceramics were investigated. Dense 3ZnO·B₂O₃ ceramics were obtained as sintered in the temperature range from 950 to 1000 °C for 3 h. The X-ray diffraction showed that the obtained ceramics were of a monoclinic 3ZnO·B₂O₃ structure. The ceramic specimens fired at 955 °C for 1 h exhibited excellent microwave dielectric properties: ?_r ∼ 6.9, Q × f ∼ 20,647 GHz (@6.35 GHz), and τ_f ∼ −80 ppm/°C. The dependences of relative density, ?_r, and Q × f of ceramics sintered at 955 °C on sintering soaking time showed that they all reached their plateaus as the soaking time was up to 60 min. Meanwhile, 3ZnO·B₂O₃ ceramics had no reaction with silver during cofiring, indicating it is a potential candidate for low-temperature cofired ceramic (LTCC) substrate.     

Effects of annealing and interlayers on the adhesion energy of copper thin films to SiO2/Si substrates

The adhesion of sputtered copper thin films was measured with a quantitative indentation technique utilizing refractory superlayers to trigger and promote delamination. Adhesion energies of the indentation-induced delaminations were analyzed in terms of the critical strain energy release rate. Two groups of films were investigated. Group I ranged in thickness from 225 to 1000 nm in both the as-deposited and annealed condition. Adhesion energies ranged from 2 to 15 J/m², with higher adhesion for the annealed condition. Group II films had nominal thicknesses of 430 and 1100 nm, some with 7–10 nm interlayers of either titanium or chromium. Adhesion energies of these films ranged from 4 to 30 J/m², increasing by a factor from 1.3 to 7.5, as a function of the interlayer presence and type, with the increase in energy due to a chromium interlayer exceeding that of titanium. Adhesion energies increased with film thickness for all films, with interlayers and annealing producing a larger increase. These quantitative results were compared to previous semi-quantitative and quantitative results, and shown to have comparable magnitudes and trends.     

Influences of substrate type on the pH sensitivity of CuS thin films EGFET prepared by spray pyrolysis deposition

Copper sulphide (CuS) thin films were deposited by spray pyrolysis using CuCl₂·2H₂O and Na₂S₂O₃·5H₂O precursors as sources of Cu²⁺ and S^2- respectively, with deionized water as a solvent. Three types of substrates were used for films deposition; glass, tungsten and Si. X-ray measurements of the structural characteristics of the deposited films indicated single phase CuS covellite phase with orientations in the z-axis (001). The presence of oxygen suggested improved pH sensing characteristics. Morphological characterization showed differences in shape and size of CuS crystal structure, which affect the surface-to-volume ratio and surface site density of the substrates. The as-deposited films were used as extended gates of field effect transistor to measure the pH sensitivity for buffer solutions in the set of 2-to-12 step 2; the optimum pH sensitivity was 23.3 mV/pH for CuS/glass membrane. The hysteresis was measured for buffer solutions prepared at pH7-pH4-pH7-pH10-pH7 in order to find its pH response delay; the minimum value was 0.48 mV for glass substrate. Also, the repeatability, stability and reliability of the (CuS) thin films were measured in terms of coefficient of variation (C.V.) with the same setup used for measuring pH sensitivity. Repeatability values of 0.04%, 0.02% and 0.38% were recorded for glass, tungsten and Si, respectively, while stability and reliability values of 0.15%, 0.15% and 0.10% were recorded at pH4, pH7 and pH10, respectively, for glass substrate.     

H_2SO_4-H_2O_2-H_2O对GaAs晶片的择优腐蚀

为研制具有沟道衬底的单模激光器,讨论了H_2SO_4-H_2O_2-H_2O对GaAs晶片的择优腐蚀。实验证明,使用H_2SO_4∶H_2O_2∶H_2O=1∶8∶8腐蚀液,在GaAs(100)面上沿[011]和[01(?)]方向开槽分别获得燕尾槽和V型槽衬底,满足了器件设计的要求。     

栽培基质的研究进展

自20世纪70年代以来,随着世界园艺业与植物容器栽培的发展,基质市场迅速壮大,栽培基质成为重要的研究领域。本文从基质材料的开发与再利用,基质的性质,基质分析方法的标准化,及基质研究中所存在的问题及发展展望四个方面进行了述评。