Band-Bending at Buried SiO2/Si Interface as Probed by XPS

Cataloged from PDF version of article.X-ray photoelectron spectroscopy is used to probe the photoinduced shifts in the binding energies of Si2p, O1s, and C1s of the SiO2/Si interfaces of a number of samples having oxide and/or thin organic layers on top of p- and n-Si wafers. Whereas the photoinduced shifts, in each and every peak related, vary from 0.2 to 0.5 eV for the p-type samples, the corresponding shifts are substantially smaller (<0.1 eV) for the n-type, regardless of (i) oxidation route (thermal or anodic), (ii) thickness of oxide layer, (iii) nature of organic layer, or (iv) color of three illuminating sources we have used. This leads us to conclude that these particular photoshifts reflect the charge state of the SiO2/Si interface, even in the case of a 20 nm thick oxide, where the interface is buried and cannot be probed directly by XPS

Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

Cataloged from PDF version of article.We investigated the tribological interaction between polytetrafluoroethylene (PTFE) and silicon oxide surfaces. A simple rig was designed to bring about a friction between the surfaces via sliding a piece of PTFE on a thermally oxidized silicon wafer specimen. A very mild inclination (similar to 0.5 degrees) along the sliding motion was also employed in order to monitor the tribological interaction in a gradual manner as a function of increasing contact force. Additionally, some patterns were sketched on the silicon oxide surface using the PTFE tip to investigate changes produced in the hydrophobicity of the surface, where the approximate water contact angle was 45 degrees before the transfer. The nature of the transferred materials was characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS results revealed that PTFE was faithfully transferred onto the silicon oxide surface upon even at the slightest contact and SEM images demonstrated that stable morphological changes could be imparted onto the surface. The minimum apparent contact pressure to realize the PTFE transfer is estimated as 5 kPa, much lower than reported previously. Stability of the patterns imparted towards many chemical washing processes lead us to postulate that the interaction is most likely to be chemical. Contact angle measurements, which were carried out to characterize and monitor the hydrophobicity of the silicon oxide surface, showed that upon PTFE transfer the hydrophobicity of the SiO2 surface could be significantly enhanced, which might also depend upon the pattern sketched onto the surface. Contact angle values above 100 degrees were obtained. (C) 2014 AIP Publishing LLC

Chloride Ingress of Carbonated Blast Furnace Slag Cement Mortars

In the Netherlands civil engineering structures, such as overpasses, bridges and tunnels are generally built using blast furnace slag cement (BFSC, CEM III/B) concrete, because of its high resistance against chloride penetration. Although the Dutch experience regarding durability performance of BFSC concrete has been remarkably good, its resistance to carbonation is known to be sensitive, especially when the used slag percentage is high. In a field investigation on a highway overpass damage was found in sheltered elements such as abutments and intermediate supports, which was attributed to chloride induced corrosion enhanced by carbonation that occurred prior to the chloride exposure. Many structures built using BFSC could be prone to this mechanism, i.e. carbonation enhanced chloride induced corrosion, negatively affecting their durability. Focus of the research was given on the influence of carbonation on the chloride penetration resistance of BFSC mortars with varying slag content. In light of the characteristics from the overpass case, it was assumed that first there is a period of carbonation during sheltered exposure, and subsequently joint leakage causes exposure to chlorides. In order to identify the influence of slag content on carbonation, chloride penetration resistance and their coupled effect, mortars with twelve cement blends in a range of 0-70% slag were evaluated based on chloride migration coefficient, accelerated carbonation and electrical resistivity. This study shows that carbonation of BFSC mortars increases the porosity, consequently decreasing the chloride penetration resistance. Binders with 50% or more slag were found to have a significantly lower resistance after carbonation. Consequently, the chloride penetration resistance of a given concrete cover strongly depends on the duration of carbonation and the resulting carbonation depth, hence influencing its lifespan. The service life was estimated using a simplified model for the chloride penetration time of a combined carbonated and uncarbonated layer. It was found that mortar with a slag content between 35 and 50% that was carbonated before chloride exposure show the lowest influence of carbonation on the chloride penetration resistance. © Springer International Publishing AG 2018. Bam; Cement and Beton Centrum; et al.; Rijkswaterstaat - Ministry of Infrastructure and the Environment; Van Hattum en Blankevoort; VolkerInfr

A comparison of thoracic or lumbar patient-controlled epidural analgesia methods after thoracic surgery

BACKGROUND: We aimed to compare patient-controlled thoracic or lumbar epidural analgesia methods after thoracotomy operations. METHODS: One hundred and twenty patients were prospectively randomized to receive either thoracic epidural analgesia (TEA group) or lumbar epidural analgesia (LEA group). In both groups, epidural catheters were administered. Hemodynamic measurements, visual analog scale scores at rest (VAS-R) and after coughing (VAS-C), analgesic consumption, and side effects were compared at 0, 2, 4, 8, 16, and 24 hours postoperatively. RESULTS: The VAS-R and VAS-C values were lower in the TEA group in comparison to the LEA group at 2, 4, 8, and 16 hours after surgery (for VAS-R, P = 0.001, P = 0.01, P = 0.008, and P = 0.029, respectively; and for VAS-C, P = 0.035, P = 0.023, P = 0.002, and P = 0.037, respectively). Total 24-hour analgesic consumption was different between groups (175 +/- 20 mL versus 185 +/- 31 mL; P = 0.034). The comparison of postoperative complications revealed that the incidence of hypotension (21/57, 36.8% versus 8/63, 12.7%; P = 0.002), bradycardia (9/57, 15.8% versus 2/63, 3.2%; P = 0.017), atelectasis (1/57, 1.8% versus 7/63, 11.1%; P = 0.04), and the need for intensive care unit (ICU) treatment (0/57, 0% versus 5/63, 7.9%; P = 0.03) were lower in the TEA group in comparison to the LEA group. CONCLUSIONS: TEA has beneficial hemostatic effects in comparison to LEA after thoracotomies along with more satisfactory pain relief profile

Location and Visualization of Working p-n and/or n-p Junctions by XPS

X-ray photoelectron spectroscopy (XPS) is used to follow some of the electrical properties of a segmented silicon photodetector, fabricated in a p-n-p configuration, during operation under various biasing configurations. Mapping of the binding energy position of Si2p reveals the shift in the position of the junctions with respect to the polarity of the DC bias applied. Use of squared and triangular shaped wave excitations, while recording XPS data, allows tapping different electrical properties of the device under normal operational conditions, as well as after exposing parts of it to harsh physical and chemical treatments. Unique and chemically specific electrical information can be gained with this noninvasive approach which can be useful especially for localized device characterization and failure analyses

Gate-tunable photoemission from graphene transistors

In this Letter, we report gate-tunable X-ray photoelectron emission from back-gated graphene transistors. The back-gated transistor geometry allows us to study photoemission from graphene layer and the dielectric substrate at various gate voltages. Application of gate voltage electrostatically dopes graphene and shifts the binding energy of photoelectrons in various ways depending on the origin and the generation mechanism(s) of the emitted electrons. The gate-induced shift of the Fermi energy of graphene alters the binding energy of the C 1s electrons, whereas the electric field of the gate electrodes shift the binding energy of core electrons emitted from the gate dielectric underneath the graphene layer. The gradual change of the local potential through depths of the gate dielectric provides quantitative electrical information about buried interfaces. Our results suggest that gate-tunable photoemission spectra with chemically specific information linked with local electrical properties opens new routes to elucidating operation of devices based especially on layered materials. © 2014 American Chemical Society

THE EFFICIENCY OF SUCTION DRAIN USAGE IN ARTHROSCOPIC KNEE SURGERY

Aim:The study was designed to investigate the efficiency of suction drain after arthroscopic knee surgery. It is hypothesized that suction drain decreases postoperative hemarthrosis after arthroscopic knee surgery. Methods: Patients were randomized into two groups. Suction drain was used in Group I and no drain was used in Group II. The groups were compared in terms of rest and activity pain, range of motion, Lysholm and International Knee Documentation Committee (IKDC) scores, patellar shock, need for postoperative knee puncture, amount of drainage, time of hospitalization, and loss of labor. Arthroscopic interventions like meniscectomy, synovectomy, meniscus repair and microfracture were also compared for the amount of patellar shock, need for postoperative knee puncture and amount of drainage. Results: The difference for activity pain and range of motion between the two groups was statistically nonsignificant. Rest pain improved faster in control group. Lysholm and IKDC scores were improved in both groups but the amount of increase was statistically nonsignificant. The amount of patellar shock was also statistically nonsignificant between the two groups. The amount of patellar shock, need for postoperative knee puncture and amount of drainage were also statistically nonsignifiant for arthroscopic interventions like meniscectomy and synovectomy. Conclusions: Suction drain application was unnecessary in many situations after arthroscopic knee surgery in this study. Although suction drain usage delayed the recovery from postoperative pain in this study, other parameters of pain were not affected from suction drain usage. Routine usage of a suction drain after arthroscopic knee surgery was not recommended

Microscopy techniques for determining water-cement (w/c) ratio in hardened concrete: A round-robin assessment

Water to cement (w/c) ratio is usually the most important parameter specified in concrete design and is sometimes the subject of dispute when a shortfall in concrete strength or durability is an issue. However, determination of w/c ratio in hardened concrete by testing is very difficult once the concrete has set. This paper presents the results from an inter-laboratory round-robin study organised by the Applied Petrography Group to evaluate and compare microscopy methods for measuring w/c ratio in hardened concrete. Five concrete prisms with w/c ratios ranging from 0.35 to 0.55, but otherwise identical in mix design were prepared independently and distributed to 11 participating petrographic laboratories across Europe. Participants used a range of methods routine to their laboratory and these are broadly divided into visual assessment, measurement of fluorescent intensity and quantitative backscattered electron microscopy. Some participants determined w/c ratio using more than one method or operator. Consequently, 100 individual w/c ratio determinations were collected, representing the largest study of its type ever undertaken. The majority (81%) of the results are accurate to within ± 0.1 of the target mix w/c ratios, 58% come to within ± 0.05 and 37% are within ± 0.025. The study shows that microscopy-based methods are more accurate and reliable compared to the BS 1881-124 physicochemical method for determining w/c ratio. The practical significance, potential sources of errors and limitations are discussed with the view to inform future applications