Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 In this study the possibility of the fabrication of CIGS layers from stacked precursors with selenization is examined. Different sequences of precursor layers and two different selenization methods were applied, in order to establish the optimal order of Cu, In and Ga layers in the precursor layer stack. The obtained CIGS films were studied by different micro- and surface analysis methods (TEM, SEM, EDS, XRD, SNMS, XPS). Since the evaporation of a Se layer and post-annealing does not result in a homogeneous CIGS layer, the appropriate selenization must be accomplished in Se-vapour. Highlights ► The fabrication of CIGS with selenization of stacked precursors was examined. ► Different sequences of precursor layers and selenization methods were applied. ► The appropriate selenization must be completed in Se-vapour. ► The optimum sequence of the precursors is: In, Ga, Cu. ► The reason for this is the diffusion properties of the precursor materials.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 Electronic and optical properties of compensated and noncompensated (Cr, N) codoped TiO 2 have been investigated using density functional theory with plane wave basis set and pseudopotential. To investigate the formation of defect pair in the codoped models, defect pair binding energy was calculated. Compensated codoped model has two Cr atoms doped at Ti sites, one N atom at O sites along with an oxygen vacancy that gave stable configuration, better electronic and optical properties. Defect pair binding energy of this model showed that, individual defects would bind each other leading to stable configuration compared to mono-doped models. Band structure results showed that compensated (Cr, N) codoping introduced substantially broaden intermediate states in the forbidden band along with narrowed band gap. Furthermore, the Fermi level was shifted from top of the valence band to middle of the forbidden band describing half metallic character. Cr doping changed the nature of N 2p states from unoccupied to occupied which will improve electron–hole pair separation. Optical properties comparison showed that all doped models effectively shifted the absorption edge of TiO 2 towards visible light. Compensated (Cr, N) codoped TiO 2 has better optical properties and covered wide absorption band in the visible light region, attributed to the stable configuration, narrowed band gap and widely distributed states in the band gap. Our results provide reasonable explanation of the experimental findings. Highlights ► Ab-initio calculations were carried out for (Cr, N) codoped TiO 2 . ► In compensated (Cr, N) codoped models, individual defects bind each other. ► Compensated codoped model has stable structure and better optical properties. ► All doped models shifted the absorption edge of TiO 2 towards visible light.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 Due to renewed interest in hard-on-hard prosthetic joint replacements, especially metal-on-metal (MOM) and ceramic-on-metal joints (COM), concerns about debris and released metal ions from wear and mechanical-enhanced electrochemical (tribocorrosion) processes have raised. In order to reduce the metal debris quantity and the release of metal ions, a diamond like carbon (DLC) film is deposited on CoCrMo alloy by using a filtered cathodic vacuum arc technique (FCVA). The tribocorrosion behavior of DLC coated CoCrMo alloy is studied in bovine calf serum and 0.9% NaCl solution by using a linear reciprocating pin-on-plate tribometer with an integrated electrochemical cell. The open circuit potential (OCP) and the polarization test are monitored during the reciprocating pin-on-plate test. The results show that the absorbed protein layer on DLC surface play a positive role in reducing wear and metal ion release. The presence of DLC layer improves the tribocorrosion resistance of CoCrMo alloy. And The DLC film has a potential application on hard-on-hard prosthetic joint replacements and it can effectively reduce the metal debris quantity and the release of metal ions. Highlights ► The DLC film can improve the tribocorrosion resistance of CoCrMo alloy. ► The absorbed protein layer on DLC surface plays a positive role in reducing wear. ► The DLC film has a potential application on hard-on-hard prosthetic joint.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 Several methods have been used in vacuum metrology for volume determination. Volume ratios can be determined by different gas expansion methods, which were primarily developed for the precise determination of expansion ratios in static expansion systems. Measurements of the volume ratios using the gas expansion methods below 10 −2  Pa are influenced by outgassing from chamber walls. To reduce outgassing in the expansion chambers during measurements at low pressures, we have installed non-evaporable getter (NEG) pumps, which pump hydrogen and other active gases but have a negligible pumping speed for inert gases. The volume ratio of two chambers of an experimental static expansion system has thus been measured using the inert gases argon, helium and krypton. The obtained results were compared with the measurements without the use of an NEG pump. Measurements of the pressure ratios were performed with a spinning rotor gauge (SRG). Highlights ► Use of nonevaporable getter (NEG) pumps in vacuum metrology. ► Use of a spinning rotor gauge for volume ratio measurements at a very low pressure. ► The selective pumping of NEG reduces errors due to outgassing when inert gas is used for calibration. ► The NEG pump assures the amount of calibrating gas is the same before and after expansion. ► It is also important to use an NEG pump to purify the gas before expansion.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 We have demonstrated an evaporation method to obtain a uniform organic thin-films with designed evaporation source which have array of two dimensional apertures of different sizes above an evaporation source optimized the distance between evaporation source and substrate, a uniform film was formed. Experimental results varying with position of the substrate are fitted to the theory of evaporation and the simulation of film uniformity using the uniform evaporation method was examined. In the simulation, different diameters of each apertures and distance between the evaporation source and the substrate were investigated. When the distance between the evaporation source and the substrate was 7 mm, adjusting the diameters of each apertures, the simulation uniform of film thickness of ±3.9 and ±1.0% at array of 3 × 3 and 9 × 9 apertures of different sizes was achieved in simulation, respectively. Moreover, in the evaporation experiment using array of 3 × 3 apertures, the uniformity of ±6.5% was obtained by photoluminescence measurement. Highlights ► We examine array of two dimensional apertures of different sizes above evaporation source optimized the distance between evaporation source and substrate. ► We demonstrate uniform deposition of organic thin film using compact equipment and larger material utilization yield. ► We achieve uniformity of film for simulation and experimental results. ► Optimum distance between evaporation source and substrate is very close.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 CuIn(S,Se) 2 (CISSe) thin films have been prepared onto soda-lime-glass (SLG) substrates by selenization and sulfurization of magnetron sputtered Cu–In precursors. The results indicate that the properties of the CISSe films are strongly dependent on the post-annealing treatment. After annealing at 400 °C for 20 min, the CISSe films have formed tetragonal (chalcopyrite) crystal structure and the diffraction peaks of the films shift systematically to the left with the temperature varying from 400 °C to 500 °C. EDAX study reveals that the compositions of CISSe films are Cu 0.83 In 1.17 S 1.67 Se 0.3 , Cu 0.86 In 1.13 S 1.61 Se 0.4 and Cu 0.82 In 1.15 S 1.54 Se 0.49 after annealing at 400 °C, 450 °C and 500 °C, respectively. The direct optical band gaps of the films slightly decrease from 1.44 ev to 1.32 ev with the increase of the temperature from 400 °C to 500 °C, and the optical absorption coefficient is over 10 5  cm −1 . The films annealed at 400 °C–500 °C are all found to be p-type and the resistivity is almost 10 −2 –10 −3  Ω cm. The carrier mobility of the film at 500 °C is almost as high as 1.701 cm 2 /V S. Highlights ► CuIn(S,Se) 2 is prepared by four-layered sputtering and selenizing processes. ► The preparation process can effectively prevent the indium loss and toxicity of H 2 Se. ► The high quality CuIn(S,Se) 2 thin films have been obtained by the process. ► The band gap of the deposited CuIn(S,Se) 2 films can be adjusted by heat treatment.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 Poly (p–phenylene-2, 6-benzobisoxazole) (or PBO) fibers were modified by air dielectric barrier discharge plasma (air-DBD) with different treatment time. The wettability of the PBO fibers were enhanced evidently, which was proved by dynamic contact angle analysis (DCAA), the contact angle in water of the fibers treated by air-DBD plasma decreased from 77.52° to 34.05°, while the surface free energy increased from 44.73 mJ/m 2 to 64.04 mJ/m 2 . The surface morphology changes and variations of chemical components of PBO fibers were detected by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the fiber surface morphology became rougher and some newly polar groups were introduced onto the fiber surfaces. They contributed to the enhancement of the wettability. Furthermore, the interfacial adhesion between PBO fibers and bismaleimide (BMI) resin was improved obviously, which revealed by the increased ILSS of the PBO/BMI composites. Nevertheless, the ILSS of PBO/BMI composites decreased to 47.0 MPa after PBO fibers were stored in air for 7 days and there were little changes for 7–30 days. Highlights ► The wettability of PBO fibers was improved evidently after treated by air-DBD plasma. ► Surface polarity was enhanced by air-DBD plasma. ► Air-DBD plasma roughened the PBO fiber morphology. ► Adhesion of PBO/BMI composites was strengthened obviously by short-time plasma treatment. ► Aging behaviors of PBO/BMI composites were observed in first 7 days, and no obvious changes for 7–30 days.

Description: June 2013 Publication year: 2013 Source: Vacuum, Volume 92 A two-dimensional fluid model is established to describe the argon discharges coupled with the neutral gas flow in a capacitively coupled plasma reactor. Two different configurations are designed to investigate the influence of the gas flow direction on discharges. The radial distributions of ion density and ion flux are paid for a special attention. It is found that when the gas flow is mainly axial, the ion density and ion flux increases significantly with the increase of inlet velocity, and the radial uniformity of their distributions changes little. When the gas flow is mainly radial, there are two peaks in the ion density distributions. With the increase of velocity, the left peak is weakened and the right peak is enhanced. It is also found that with the increase of the outlet pressure, both the ion density and ion flux increase greatly, but the influence of the gas flow on discharges decreases distinctly. Moreover, it is shown that the density peak moves from side to center at high pressure when the neutral gas flow is mainly in the axial direction. Highlights ► When the gas flow is radial, there are two peaks in the ion density distribution. ► With the increase of inlet velocity, the left peak of ion density is weakened. ► With the increase of inlet velocity, the right peak of ion density is enhanced. ► With the increase of pressure the role of gas flow on discharges weakens greatly. ► The density peak moves from side to center at high pressure.

Description: May 2013 Publication year: 2013 Source: Vacuum, Volume 91 The alternating current (AC) conductivity and dielectric properties of the p -N,N dimethylaminobenzylidenemalononitrile (DBM) were investigated in the frequency range from 5 kHz to 2 MHz within the temperature range from 291 to 413 K. The temperature dependence of AC conductivity and the frequency exponent, s , is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energy (Δ E AC ), the pre-exponential factor ( σ 0 ), and the density of states at Fermi level ( N ( E F )) were determined. The dielectric constant and dielectric loss increase with temperature at low frequencies and are frequency independent at high frequencies. Highlights ► DBM compound is of the type donor-phenyl-acceptor (D-ph-A). ► Both capacitance and loss tangent are found to decrease by increasing frequency. ► Both capacitance and loss tangent are found to increase by increasing temperature. ► Single polaron hopping mechanism is the dominating conduction in DBM compound.

Description: May 2013 Publication year: 2013 Source: Vacuum, Volume 91 The morphology of tungsten tip (microsized monocrystal) adsorbed with Pt at coverages up to around 2 ML and subsequently annealed at temperatures ranging from 1000 K to 2100 K was studied using Field Emission Microscopy (FEM) technique. The sharpening of the [111] pole region was manifested by significant increase of field emission current density. This effect was observed for Pt coverages ranging from 0.1 ML to 1.1 ML and full range of examined annealing temperatures, but was most pronounced for annealing at temperatures exceeding 1300 K. Formation of the sharp apex was accompanied by growth of {112} facets for the annealing temperatures lower than 1900 K. Annealing at higher temperatures resulted in formation of sharp apex of the W tip and complete disappearance of {112} planes when the Pt coverage exceeded approximately 0.25 ML. Highlights ► W tip covered by 0.1–1.1 ML of Pt and annealed forms a sharp apex at [111] pole. ► Best sharpening is observed for annealing at 1300 K–2100 K. ► For Pt coverages exceeding 1.1 ML no sharpening effect is observed. ► Annealing at T  〉 1900 K causes disappearing of {112} facets.