Photo-electric measurement of the work function of metals and its alteration after gas adsorption

Jaeckel, Rudolf; Wagner, Brian D.

doi:10.1016/0042-207x(63)90537-2

Cited by 21 publications

(5 citation statements)

References 8 publications

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“…The secondary electron energy distribution curve from a tantalum substrate is shown in Figure . For fast secondary electrons (SEs, E k ≥ 10 eV), the relative energy distribution was measured using an analytical X-ray photoelectron spectrometer (XPS, Perkin-Elmer) under UHV conditions; for slow SEs ( E k ≤ 10 eV), it was obtained from eq 1: normalη false( E normalk false) = normalη normals E normalk / false( E normalk + W false) 4 where η( E k ) is the yield of SEs having kinetic energy of E k , η s is the yield normalization coefficient, and W is the work function of tantalum (i.e., 4.3 ± 0.1 eV for a vacuum deposited film of tantalum and 4.22 ± 0.02 eV for the bulk substrate of tantalum). The electron energy distribution peaks at 1.4 eV, and the average energy is 5.85 eV.…”

Section: Experimental Methodsmentioning

confidence: 99%

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N₂ and O₂ Atmospheres

et al. 2011

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DNA damage induced by low energy electrons (LEEs) and soft X-rays is measured under dry nitrogen and oxygen at atmospheric pressure and temperature. Five-monolayer plasmid DNA films deposited on tantalum and glass substrates are exposed to Al K α X-rays of 1.5 keV in the two different environments. From the damage yields for DNA, G-values are extracted for X-rays and LEEs. The G values for LEEs are 3.5 and 3.4 higher than those for X-ray photons under N 2 and O 2 atmospheres, respectively. Since most of the measured damage is in the form of single strand breaks (SSB), this result indicates a much higher effectiveness for LEEs relative to X-rays in causing SSB in both environments. The results indicate that the oxygen fixation mechanism, which is highly effective in increasing radiobiological effectiveness, under aerobic conditions, is operative on the type of damage created at the early stage of DNA radiolysis by LEEs.

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Section: Experimental Methodsmentioning

confidence: 99%

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N₂ and O₂ Atmospheres

et al. 2011

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“…This effect corresponded to the mechanism of electronic sensitization. The electron work function φ for reduced palladium surface was smaller than in the case of PdO x and is φ = 4.8 eV [ 73 ], which was close to the work function for SnO 2 ( φ = 4.9 eV, [ 74 ]). Thus, as a result of the reduction of PdO x clusters, a barrier was removed at the Pd/SnO 2 interface, which led to a decrease in material resistance and the sensor response appearance.…”

Section: Resultsmentioning

confidence: 75%

Influence of Mono- and Bimetallic PtOx, PdOx, PtPdOx Clusters on CO Sensing by SnO2 Based Gas Sensors

et al. 2018

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To obtain a nanocrystalline SnO2 matrix and mono- and bimetallic nanocomposites SnO2/Pd, SnO2/Pt, and SnO2/PtPd, a flame spray pyrolysis with subsequent impregnation was used. The materials were characterized using X-ray diffraction (XRD), a single-point BET method, transmission electron microscopy (TEM), and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with energy dispersive X-ray (EDX) mapping. The electronic state of the metals in mono- and bimetallic clusters was determined using X-ray photoelectron spectroscopy (XPS). The active surface sites were investigated using the Fourier Transform infrared spectroscopy (FTIR) and thermo-programmed reduction with hydrogen (TPR-H2) methods. The sensor response of blank SnO2 and nanocomposites had a carbon monoxide (CO) level of 6.7 ppm and was determined in the temperature range 60–300 °C in dry (Relative Humidity (RH) = 0%) and humid (RH = 20%) air. The sensor properties of the mono- and bimetallic nanocomposites were analyzed on the basis of information on the electronic state, the distribution of modifiers in SnO2 matrix, and active surface centers. For SnO2/PtPd, the combined effect of the modifiers on the electrophysical properties of SnO2 explained the inversion of sensor response from n- to p-types observed in dry conditions.

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“…In the case of a clean Pd surface, the work function increases by ca. 0.2V by hydrogen (11,12), 0.7-0.8V by carbon monoxide (13,14) and ca. 1.0V by oxygen (2,15).…”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence of the Sensitivities of Metal ‐ TiO2 Junctions to Various Reducing Gases

Yamamoto

Tonomura

Tsubomura

1982

J. Electrochem. Soc.

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The current through a Pd-TiO2 diode is sensitive to hydrogen at room temperature and becomes sensitive to other reducing gases, such as carbon monoxide, ethanol, and propylene, at high temperature. Experiments were carried out extensively for the similar junctions of TiOu with Pt, Au, A1, Ni, Cu, Mg, or Zn. The Pt-TiO2 and Au-TiO2 diodes are also sensitive to hydrogen, the sensitivity being in the order of Pd > Pt > Au. The sensitivity of the diode depends on the catalytic property of the metal to the reaction between oxygen adsorbed on the metal surface and reducing gases, resulting in a lowering of the potential barrier height at the metal-TiO2 interface.It has been shown recently that the current-potential (I-U) curve of a Pd-TiO2 diode is very sensitive to hydrogen in ambient air and its possible utilization as a hydrogen sensor has been suggested (1). The sensitivity presumably arises from catalytic reactions occurring at the metal surface. In air, oxygen is chemisorbed in the form of anions on the Pd surface, increasing the work function of the metal (2). When hydrogen exists in air, the oxygen is desorbed by reaction with it, resulting in a lowering of the potential barrier height at the Pd-TiO2 interface.Many authors have also investigated hydrogen-sensitive diodes made of Pd and semiconductors such as Si (3), CdS (4), and ZnO (5), and explained the results by the change in electrical properties arising either from the adsorption of hydrogen at the Pdsemiconductor interface (3, 5) or the formation of palladium hydride (4). Such an explanation is inconsistent with our own, as discussed in our previous paper (1).In this paper the experimental results are reported on the sensitivity of a Pd-TiO2 diode to various reducing gases such as carbon monoxide, ethanol, propylene, and isobutane together with similar experimental results on the junctions of TiO~ with other metals such as Pt, Au, Ni, A1, Cu, Mg, and Zn. ExperimentalMetal-TiO2 Schottky diodes were fabricated by depositing thin metal film, ca. 200A thick, on n-type TiOe single crystal wafers, the detail of the procedure was described in our previous paper (1). A schematic diagram of the metal-TiO2 diode is shown in Fig. 1. The current-potential (I-U) curve was measured by use of a Hokuto denko HA 101 potentiostat. Reducing gases were introduced into the measuring chamber by a syringe and stirred well with a small fan. Carbon monoxide, propylene and isobutane, guaranteed to be more than 99.9% pure, were obtained from Seite.tsu Kagaku Company. Ethanol was evaporated from 99% pure liquid.Surface potential of palladium was measured by a vibrating capacitor method using a Cu reference electrode (6). Results and DiscussionThe Pd-TiOz d~ode.--The Pd-TiO2 diode at room temperature is very sensitive to hydrogen, but insensitive to any other reducing gases studied. It, however, becomes sensitive to CO, ethanol, and propylene at higher temperature. Figure 2 shows, as an example, a change in I-U curve of the P d-TiO2 diode by introduc-* Electrochemical Society Active...

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Photo-electric measurement of the work function of metals and its alteration after gas adsorption

Cited by 21 publications

References 8 publications

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N₂ and O₂ Atmospheres

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N₂ and O₂ Atmospheres

Influence of Mono- and Bimetallic PtOx, PdOx, PtPdOx Clusters on CO Sensing by SnO2 Based Gas Sensors

Temperature Dependence of the Sensitivities of Metal ‐ TiO2 Junctions to Various Reducing Gases

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Photo-electric measurement of the work function of metals and its alteration after gas adsorption

Cited by 21 publications

References 8 publications

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N2 and O2 Atmospheres

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N2 and O2 Atmospheres

Influence of Mono- and Bimetallic PtOx, PdOx, PtPdOx Clusters on CO Sensing by SnO2 Based Gas Sensors

Temperature Dependence of the Sensitivities of Metal ‐ TiO2 Junctions to Various Reducing Gases

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Soft X-ray and Low Energy Electron-Induced Damage to DNA under N₂ and O₂ Atmospheres

Soft X-ray and Low Energy Electron-Induced Damage to DNA under N₂ and O₂ Atmospheres