Epitaxial growth of Cu(100) and Pt(100) thin films on perovskite substrates

Pulsed laser deposition has been used to grow epitaxially oriented thin films of Cu and Pt on (100)-oriented SrTiO₃ and LaAlO₃ substrates. X-ray diffraction results illustrated that purely epitaxial Cu(100) films could be obtained at temperatures as low as 100 °C on SrTiO₃ and 300 °C on LaAlO₃. In contrast, epitaxial (100)-oriented Pt films were attained on LaAlO₃(100) only when deposited at 600 °C. Atomic force microscopy images showed that films deposited at higher temperatures consisted of 3D islands and that flat, layered films were obtained at the lowest deposition temperatures. Importantly, Cu films deposited at 100 °C on SrTiO₃(100) were both purely (100)-oriented and morphologically flat. Pt and Cu films displaying both epitaxial growth and smooth surfaces could be obtained on LaAlO₃(100) only by using a three-step deposition process. High-resolution transmission electron microscopy demonstrated an atomically sharp Cu/SrTiO₃ interface. The crystalline and morphological features of Cu and Pt films are interpreted in terms of the thermodynamic and kinetic properties of these metals.     

Removal of Cu(II) and Pb(II) by Pithophora oedogonia: sorption, desorption and repeated use of the biomass

Maximum sorption of Cu(II) and Pb(II) by dried filamentous green alga Pithophora oedogonia occurred at pH 4.5 and 5.0, respectively. Chemical pretreatment could not appreciably enhance the metal sorption ability of the biomass. HCl and EDTA desorbed 92-96% of the sorbed metal from the metal-loaded biomass. Sorption and desorption of both the test metals were very rapid attaining an equilibrium within 15 min. The time course data of both the processes fitted well to the pseudo-first and the pseudo-second-order Lagergren kinetic models with r2> or =0.979. The isotherm equilibrium of Cu(II) and Pb(II) followed the Redlich-Peterson and Sips model very well with r2> or =0.991. The sorption of Cu(II) and Pb(II) at varying biomass doses could be well defined by linear and hyperbolic decrease, respectively. The regenerated biomass of Pithophora has better reusability for Pb(II) than for Cu(II). A good mechanical strength of Pithophora biomass was apparent as only 10-15% loss of biomass occurred at the end of the fifth cycle.     

In situ observations of the real-time stress-evolution and delamination of thin Ta films on Si(100)

Polycrystalline sputtered Ta coatings on Si(100) substrates were thermally tested for 1 h at 585 °C, while their stress evolution and eventual delamination were observed in situ and in real-time using a recently developed synchrotron X-ray white beam technique. Films deposited at ‘low’ (0.26-0.67 Pa), ‘intermediate’ (0.80-0.93 Pa), and ‘high’ (1.06-2.00 Pa) Ar pressures exhibited severe, moderate, and no blistering, respectively. These results were explained by the attendant stress data, which indicated the development of high, moderate, and low maximum compressive stress in the low, intermediate, and high-pressure coatings, respectively. Additionally, the structure of the films was probed before and after thermal testing using X-ray diffraction in both grazing incidence and θ−2θ scanning geometries. It was determined that all coatings made a complete conversion to orthorhombic Ta₂O₅ after the 1 h thermal test, regardless of their deposition pressure.     

First-principles study of near surface point defects stability in Si (100) and SiGe(100)

Calculations based on Density Functional Theory are carried out to study interstitial generation close to the Si(100) surface with further consideration of effects related to the presence of substitutional Ge atoms on the surface. Defect structures, vacancy and Si interstitial, and associated energies are calculated. We observe that germanium atoms tend to increase the stability of created defects, promote the generation of interstitials through drastic structural changes and blocks the climb of Si interstitials towards the surface.     

X-ray photoelectron spectroscopy and thermal desorption spectroscopy comparative studies of L-CVD SnO2 ultra thin films

In this paper we present the results of comparative studies of the chemical stability of L-CVD SnO₂ ultra thin films (20 nm) deposited on the atomically clean Si(100) substrate after their subsequent in situ hydrogenation and oxidation, and then after air exposure. For the control of surface chemistry of these films we used in a comparative way the X-ray Photoemission Spectroscopy (XPS) combined with ion depth profiling (DP XPS) and Thermal Desorption Spectroscopy (TDS). Our XPS experiments showed that the L-CVD SnO₂ ultrathin films after subsequent in situ hydrogenation and oxidation consist of strongly nonstoichiometric layer at the top of Si dioxide substrate. After subsequent air exposure they were covered with undesired 3 monolayers of C contamination and various forms of oxygen. During the TDS procedure a two-step desorption of molecular hydrogen (H₂), water vapor (H₂O), carbon dioxide (CO₂) and atomic oxygen (O) at the temperatures of ~ 530 K and 600 K was observed, respectively. The TDS results were in a good correlation with evident decreasing of the relative concentration of C contaminations, as well as variation of nonstoichiometry of the L-CVD SnO₂ ultra thin films as determined by XPS combined with ion depth profiling.     

Effect of P addition on the thermal stability and electrical characteristics of NiSi films

Immersion Ni-P deposition is undoubtedly one of the most important catalytic deposition process, due to its simplicity in operation and low equipment cost. In this study, immersion deposited Ni-P films were used to form Ni-silicide films. Ni-P films with a thickness of 100 nm were fabricated by immersing Si(100) substrates in an aqueous deposition solution. Ni-silicide films were then formed by annealing the samples in a furnace at temperatures ranging from 400 °C to 900 °C for 1 h in an argon ambient. Experimental results indicate that a phosphor addition in Ni films increased the transformation temperature of NiSi to NiSi₂ to 900 °C. Moreover, the feasibility of enhancing the thermal stability of NiSi by varying the interface energy at the NiSi₂/Si interface and the surface energy of a Ni-P-Si capping layer on the NiSi surface is discussed.     

Co-adsorption of CO and oxygen on W(110) surfaces

Influence of oxygen adsorption on CO chemisorption behavior over W(110) surfaces was studied using valence band spectra and thermal desorption spectroscopy (TDS). In the absence of O, CO formed a tilted and a vertical structure at 120 K on W(110). In the presence of O coadsorbate, in contrast, formation of the tilted structure of CO was suppressed. CO desorption from oxygen-covered W(110) surfaces showed indication of a strong interaction between adsorbates at ∼900 K, which was absent without O.     

气相色谱法测定空气中苯系物的热解吸和溶剂解吸比对研究

针对测定工作场所空气中苯系物的标准方法热解吸和溶剂解吸．气相色谱法在实际应用中存在的问题，分别考察和比对了这两种方法，特别对影响热解吸效率的因素进行了详细研究，发现改善热解吸方式能提高活性炭管的合格率和热解吸效率；不同温度下需要的解吸时间不同，延长热解吸时间有利于提高样品解吸率；并对标准方法GBZ／T160．42-2004提出了相应的改进措施。     

Improvement in thermal stability of B-C-N thin films fabricated by magnetron sputtering using graphite and BN co-target

Thermal stability of amorphous boron-carbon-nitride (B-C-N) films fabricated by magnetron sputtering using a graphite and BN co-target was studied by X-ray photoelectron spectroscopy, infrared absorption spectroscopy, Raman spectroscopy and scanning electron microscopy. The boron-rich B-C-N films showed the higher thermal stability. These results suggest that an incorporation of B atoms into the amorphous CN networks improves the thermal stability. This improvement can be explained in terms of the creation of boron-nitrogen bonds and/or boron-carbon bonds.     

Micro-hardness, microstructures and thermal stability of (Ti,Cr,Al,Si)N films deposited by cathodic arc method

(Ti,Cr,Al,Si)N films were deposited by cathodic arc method using TiCrAlSi alloy cathodes. It was found that the microstructures of (Ti,Cr,Al,Si)N were closely related to (Al+Si) content. The crystal structure of (Ti,Cr,Al,Si)N was NaCl-type structure up to the (Al+Si) content of 0.60, where it changed to a hexagonal structure. The maximum hardness of 33 GPa was obtained at the lowest (Al+Si) content of 0.56, still in the cubic structure. The micro-hardness decreased down to 28 GPa as the crystal structure changed from NaCl-type to wurtzite-type.To investigate the thermal stabilities of (Ti,Cr,Al,Si)N, the films were annealed in a vacuum furnace. In Ti_0.20Cr_0.20Al_0.55Si_0.05N with cubic structure, the phase segregation occurred by annealing at over 900 °C, while Ti_0.22Cr_0.22Al_0.44Si_0.12N remained in cubic phase up to 1000 °C. The micro-hardness of Ti_0.20Cr_0.20Al_0.55Si_0.05N increased and that of Ti_0.22Cr_0.22Al_0.44Si_0.12N decreased at 1000 °C. Ti_0.20Cr_0.11Al_0.58Si_0.11N with a cubic and hexagonal mixture phase held its (c,h)-mixture phase up to 1000 °C, while there was an indication of an increase both in micro-hardness and in cubic ratio after annealing.In this paper, the micro-hardness and microstructure of (Ti,Cr,Al,Si)N are discussed as a function of annealing temperature and investigated by X-ray diffraction and electron microscopy.     

聚碳酸亚丙酯/凹凸棒纳米复合材料制备与热稳定性研究

通过溶液共混法制备了聚碳酸亚丙酯/凹凸棒纳米复合材料。利用FT-IR、XRD和SEM表征手段研究了复合材料的结构。研究表明有机改性的凹凸棒在聚碳酸亚丙酯中分散均匀,平均粒径为70nm。利用TG研究了聚碳酸亚丙酯/凹凸棒纳米复合材料的热稳定性,结果发现纳米尺寸凹凸棒的引入能够显著提高聚碳酸亚丙酯的热稳定性,其中凹凸棒含量为0.5%的复合材料热稳定性最好,其5%、50%和最大热分解温度分别为273℃、291℃和289℃,相比PPC分别提高了63℃、53℃和52℃。     

Preparation and characterization of sulfonated poly(1,3,4-oxadiazole)/multi-walled carbon nanotube composite films with high performance in electric heating and thermal stability

For manufacturing thermally stable electric heating composite films, a sulfonated poly(1,3,4-oxadiazole) (sPOD) was synthesized and it was composited with pristine MWCNT of 0.1–10.0 wt% by an ultrasonicated solution mixing and casting. SEM images revealed that the pristine MWCNTs were dispersed well in the composite matrix via π–π interaction between the MWCNTs and the aromatic rings of sPOD backbone. The electrical resistivity of the composite films decreased considerably from ∼10⁹ Ω cm to ∼10⁰ Ω cm with the increment of the MWCNT content by forming a percolation threshold at ∼0.026 wt%. The composite films with 5.0–10.0 wt% MWCNT contents, which had sufficiently low electrical resistivity of ∼10³–10⁰ Ω cm, exhibited excellent electric heating performance by attaining high maximum temperatures as well as electric energy efficiency. Since the dominant thermal decomposition of the composite films took place at ∼500 °C, sPOD/MWCNT composite films with low electrical resistivity could be used for high performance electric heating materials for advanced applications.     

The preparation and characterization of preferred (110) orientation aluminum nitride thin films on Si (100) substrates by pulsed laser deposition

The preferred (110) oriented aluminum nitride (AlN) thin films have been prepared by pulsed laser deposition on p-Si (100) substrates. The films were characterized with X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscope (AFM). The results indicate that the AlN thin films are well-crystallized when laser energy is higher than 300 mJ/puls. The AFM images show that the surface roughness of the deposited AlN thin films gradually increases with increasing laser energy, but the surface morphologies are still very smooth. The crystallinity and morphology of the thin films are found to be strongly dependent on the laser energy.     

Effects of deposition and post-annealing conditions on electrical properties and thermal stability of TiAlN films by ion beam sputter deposition

TiAlN films were deposited by ion beam sputter deposition (IBSD) using a Ti-Al (90/10) alloy target in a nitrogen atmosphere on thermal oxidized Si wafers. Effects of ion beam voltage, substrate temperature (T_s) and post-annealing conditions on electrical properties and oxidation resistance of TiAlN films were studied. According to the experimental results, the proper kinetic energy provided good crystallinity and a dense structure of the films. Because of their better crystallinity and predomination of (200) planes, TiAlN films deposited with 900 V at low T_s (50 °C) have shown lower resistivity than those at high T_s (250 °C). They also showed better oxidation resistance. If the beam voltage was too high, it caused some damage to the film surfaces, which caused poor oxidation resistance of films. When sufficient kinetic energy was provided by the beam voltage, the mobility of adatoms was too high due to their extra thermal energy, thus reducing the crystallinity and structure density of the films. A beam voltage of 900 V and a substrate temperature of 50 °C were the optimum deposition conditions used in this research. They provided good oxidation resistance and low electrical resistivity for IBSD TiAlN films.     

Diffusion and adhesion properties of Cu films on polyimide substrates

Copper thin films were prepared on polyimide (PI) substrates by physical vapor deposition (PVD) and chemical vapor deposition (CVD). Titanium nitride (TiN) diffusion barrier layers were deposited between the copper films and the PI substrates by PVD. Auger electron spectroscopy compositional depth profile showed that TiN barrier layer was very effective in preventing copper diffusion into PI substrate even after the Cu/TiN/PI samples were annealed at 300 °C for 5 h. For the as-deposited CVD-Cu/PI, CVD-Cu/TiN/PI, and as-deposited PVD-Cu/PI samples, the residual stress in Cu films was very small. Relatively larger residual stress existed in Cu films for PVD-Cu/TiN/PI samples. For PVD-Cu/TiN/PI samples, annealing can increase the peeling strength to the level observed without a diffusion barrier. The adhesion improvement of Cu films by annealing treatment can be attributed to lowering of the residual tensile stress in Cu films.     

聚乙烯醇缩苯甲醛的合成与热稳定性研究

以聚乙烯醇（PVA）和苯甲醛为原料,二甲基亚砜为溶剂,对甲基苯磺酸为催化剂,采用均相工艺合成得到聚乙烯醇缩苯甲醛（PVB）。通过衰减全反射-傅里叶红外光谱（ATR-FT-IR）、紫外-可见光谱（UV-Vis）、核磁共振氢谱（1 H NMR）、核磁共振碳谱（13C NMR）等测试手段对聚乙烯醇缩苯甲醛结构进行了表征。利用差式扫描量热仪（DSC）测定了聚乙烯醇缩苯甲醛的玻璃化温度（Tg）。采用差热分析（DTA）和热重分析（TGA）对聚乙烯醇缩苯甲醛热稳定性进行了研究。DSC结果表明聚乙烯醇缩苯甲醛的玻璃化温度为106.0℃。DTA和TGA结果表明聚乙烯醇缩苯甲醛热稳定性良好,在空气中150℃仍未见分解。     

Effect of nitrogen addition on the properties and thermal stability of fluorinated amorphous carbon films

Continuous fluorinated amorphous carbon (a-C : F) films doped with nitrogen (a-C : F : N) were deposited by plasma enhanced chemical vapor deposition using CF₄ and C₂H₂ gases as precursors with the addition of N₂ gas. The surface morphologies, chemical compositions, deposition rates, thermal stability and mechanical properties of these films varied with the deposition parameters, including CF₄ and N₂ feed gas concentrations, processing pressure, plasma power and substrate temperature. With increasing N₂ feed gas concentration, the nitrogen content of the a-C : F : N films increased to about 6 at.% and contributed to higher mechanical properties. After thermal annealing, the a-C : F films with higher fluorine contents exhibited more obvious fluorine release and extensive film thickness shrinkage, whereas the a-C : F : N films with higher contents of nitrogen doping yielded less composition variations, smaller thickness shrinkages, higher mechanical properties, and conclusively better thermal stability.     

Development of a liquid extraction method and comparison with dynamic thermal stripping–thermal desorption (DTS–TD) method: sorption of D‐limonene by flexible packaging films

The sorption of D ‐limonene into polymeric structures in contact with food simulant liquids (ethanol and acetic acid solutions) was determined using two methods, liquid extraction (LE) and dynamic thermal stripping–thermal desorption (DTS–TD). The polymeric films studied were PP (polypropylene), PE/nylon/EVOH/PE (polyethylene/nylon/ethylene vinyl alcohol/polyethylene) and metPET/VA EVA/LLDPE (metallized polyethylene terephthalate/ethylenevinyl acetate/linear low density polyethylene). Our assessment showed that both LE and DTS–TD techniques are valuable procedures. LE was evaluated as an alternative method with the advantage of being a simplified process. It was possible to measure the amount of D ‐limonene in the polymers using both methods. Correlation between methods was >82% and for the single layer polymers >92%. The respective sorption values obtained by the two methods were also found to be in good agreement. LE is simple and rapid to perform and, in general, gives slightly lower results compared to DTS–TS sorption tests conducted with adequate food simulants. The results indicate that the liquid extraction method is an excellent technique for the determination of sorbate concentration in polymeric structures. Copyright © 2004 John Wiley & Sons, Ltd.     

Properties of Co on Cu(111) revealed by AES and DEPES

Auger electron (AES) and directional elastic peak electron (DEPES) spectroscopies were used to investigate the Co/Cu(111) interface. The change in the Auger Cu (M_2,3VV transition at 66 eV) peak intensity (h_Cu) recorded at room temperature shows that the Co growth mechanism is not a layer by layer type. This proves that Co does not wet the Cu substrate. The recorded DEPES profiles reveal the coexistence of fcc and hcp Co structures already at an early stage of growth (0.8 ML). The Co coverage increase leads to the reduction of intensities associated with the fcc structure and significant increase of the signal from the hcp structure. The comparison between experimental and theoretical data at large coverages (43 ML) shows a major contribution of the hcp structure within the Co layers in the recorded DEPES profiles.     

High porosity and low thermal conductivity high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C

Porous ultra-high temperature ceramics (UHTCs) are promising for ultrahigh-temperature thermal insulation applications. However, the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures. In order to overcome these obstacles, herein, porous high entropy (Zr_0.2Hf_0.2Ti_0.2Nb_0.2 Ta_0.2)C was prepared by a simple method combing in-situ reaction and partial sintering. Porous high entropy (Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1 μm, which exhibits high porosity of 80.99%, high compressive strength of 3.45 MPa, low room temperature thermal conductivity of 0.39 W·m⁻¹ K⁻¹, low thermal diffusivity of 0.74 mm²·s⁻¹ and good high temperature stability. The combination of these properties renders porous high entropy (Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)C promising as light-weight ultrahigh temperature thermal insulation materials.