Temperature-programmed photoelectron emission technique for metal surface analysis

Momose, Yoshihiro; Honma, Masakazu; Kamosawa, Tokirou

doi:10.1002/1096-9918(200008)30:1<364::aid-sia759>3.0.co;2-w

Cited by 16 publications

(15 citation statements)

References 8 publications

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“…This trend was very similar to the relationship between the PE total count and the threshold obtained for one sample at successively changed temperatures in the PE measurement (TPPE method) [14]. At the metal surfaces before the PE measurement [12,13] the C1s and O1s peaks were confirmed in the same way as those before the TriboEE measurement (Figs. 4a-7a).…”

Section: Xpssupporting

confidence: 81%

“…The electron counter in the PE measurement called TPPE method described above [12] is a gas-flow Geiger counter similar to that for the TriboEE measurement. It is further provided with an optical stimulation device consisting of a UV light source (D 2 lamp, 30 W) and a monochromator.…”

Section: Surface Potential and Photoemissionmentioning

confidence: 99%

“…In the present experiment the oxygen species adsorbed at the metal surfaces mainly originates from a natural oxide layer. Judging from the two binding energies for the O1s peak it is considered that the oxygen species at the Au metal surfaces is preferentially adsorbed in the form of the hydroxyl group (-OH) and at the Ta surfaces the adsorption of the oxide group (O 2-) prevails [12,13,17]. Clearly the O1s spectra for the Fe samples (Fig.…”

Section: Xpsmentioning

confidence: 99%

“…We have recently developed two surface analysis methods using photoemission (PE) called temperature programed photoelectron emission (TPPE) [12][13][14] and tribostimulated electron emission (TriboEE) [15]. Both TPPE and TriboEE can be observed with a gas-flow Geiger counter with a counter gas called Q gas composed of a mixture of He and about 1% iso-C 4 H 10 at atmospheric pressure.…”

Section: Introductionmentioning

confidence: 99%

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Observation of Real Metal Surfaces by Tribostimulated Electron Emission and Its Relationship to the Analyses by XPS and Photoemission

2007

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The characteristics of tribostimulated electron emission (called TriboEE) have been studied for real metal surfaces subjected to rubbing with polytetrafluoroethylene (PTFE). A gas-flow Geiger counter with a counter gas called Q gas was used for observing the TriboEE. Metal samples used were as follows: Ti, Zr (group 4 in the periodic table); V, Nb, Ta (group 5); Mo, W (group 6); Fe (group 8); Co (group 9); Ni, Pd, Pt (group 10); Cu, Ag, Au (group 11); Zn (group 12); Al (group 13); and Sn (group 14). For metals in the same groups of 4, 5, 6, 10, and 11 the number of electrons ejected during rubbing time (called TriboEE total count) increased with an increase in the period for the metal. For the metals in the groups of 4, 10, and 11 the surface fluorine content originating from PTFE debris attached at the surfaces increased with an increase in the period for the metal. The TriboEE total count was almost independent of the photoelectric thresholds determined in photoemission (PE) experiment throughout the metals, while the amount of ejected electrons in the PE measurement tended to decrease with increasing threshold. The surface potential (SP) was almost unchanged before and after the TriboEE measurement. Based on the relation to XPS, PE, and SP results the TriboEE was explained as being associated with the release of electrons transported to the attached PTFE debris from the metal substrate by a surface electric field.

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Section: Xpssupporting

confidence: 81%

Section: Surface Potential and Photoemissionmentioning

confidence: 99%

Section: Xpsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observation of Real Metal Surfaces by Tribostimulated Electron Emission and Its Relationship to the Analyses by XPS and Photoemission

2007

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“…This method is called temperature-programmed photoelectron emission (TPPE). We have reported several papers on TPPE [26][27][28]. The TPPE feature for the surfaces of 17 commercial metals was correlated with their surface chemical structure measured by XPS [27,28].…”

Section: Introductionmentioning

confidence: 99%

Using Temperature-Programmed Photoelectron Emission (TPPE) to Analyze Electron Transfer on Metallic Copper and Its Relation to the Essential Role of the Surface Hydroxyl Radical

Momose

2024

Applied Sciences

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Surface processes such as coatings, corrosion, photocatalysis, and tribology are greatly diversified by acid–base interactions at the surface overlayer. This study focuses on the action of a metallic copper surface as an electron donor/acceptor related to the inactivation of viruses. It was found that regarding Cu2O or Cu materials, electrostatic interaction plays a major role in virus inactivation. We applied the TPPE method to clarify the mechanism of electron transfer (ET) occurring at light-irradiated copper surfaces. The TPPE characteristics were strongly influenced by the environments, which correspond to the temperature and environment dependence of the total count of emitted electrons in the incident light wavelength scan (PE total count, NT), the photothreshold, and further the activation energy (ΔE) analyzed from the Arrhenius plot of NT values obtained in the temperature increase and subsequent temperature decrease processes. In this study, we re-examined the dependence of the TPPE data from two types of Cu metal surfaces: sample A, which was mechanically abraded in alcohols, water, and air, and sample C, which was only ultrasonically cleaned in these liquids. The NT for both samples slowly increased with increasing temperature, reached a maximum (NTmax) at 250 °C (maximum temperature, Tmax), and after that, decreased. For sample A, the NTmax value decreased in the order H2O > CH3OH > C2H5OH > (CH3)2CHOH > C3H7OH, although the last alcohol gave Tmax = 100 °C, while with sample C, the NTmax value decreased in the order C3H7OH > (CH3)2CHOH > C2H5OH > CH3OH > H2O. Interestingly, both orders of the liquids were completely opposite; this means that a Cu surface can possess a two-way character. The NT intensity was found to be strongly associated with the change from the hydroxyl group (–Cu–OH) to the oxide oxygen (O2−) in the O1s spectra in the XPS measurement. The difference between the above orders was explained by the acid–base interaction mode of the –Cu–OH group with the adsorbed molecule on the surfaces. The H2O adsorbed on sample A produces the electric dipole –CuOδ−Hδ+ ⋅⋅⋅ :OH2 (⋅⋅⋅ hydrogen bond), while the C3H7OH and (CH3)2CHOH adsorbed on sample C produce RO−δHδ+ ⋅⋅⋅ :O(H)–Cu− (R = alkyl groups). Gutmann’s acceptor number (AN) representing the basicity of the liquid molecules was found to be related to the TPPE characteristics: (CH3)2CHOH (33.5), C2H5OH (37.1), CH3OH (41.3), and H2O (54.8) (the AN of C3H7OH could not be confirmed). With sample A, the values of NTmaxa and ΔEaUp1 both increased with increasing AN (Up1 means the first temperature increase process). On the other hand, with sample C, the values of NTmaxc and ΔEcUp1 both decreased with increasing AN. These findings suggest that sample A acts as an acid, while sample C functions as a base. However, in the case of both types of samples, A and C, the NTmax values were found to increase with increasing ΔEUp1. It was explained that the ΔEUp1 values, depending on the liquids, originate from the difference in the energy level of the hydroxyl group radical at the surface denoted. This is able to attract electrons in the neighborhood of the Fermi level of the base metal through tunnelling. After that, Auger emission electrons are released, contributing to the ET in the overlayer. These electrons are considered to have a strong ability of reducibility.

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Electrochemical reduction of CO₂ at copper electrodes and its relationship to the metal surface characteristics

Momose¹,

Sheng²,

Ohno³

2002

Surface & Interface Analysis

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The selectivity of H 2 , CO, CH 4 and C 2 H 4 produced during the electrolysis of CO 2 in aqueous solution at copper electrodes has been investigated in relation to surface analysis of the electrodes after electrolysis by XPS and temperature-programmed photoelectron emission (TPPE) and surface potential (SP) measurements. The electrodes were prepared as follows: (A) only ultrasonic cleaning in acetone; (B) oxidation in air; (C) exposure to argon plasma. The electrolysis time was 3 h at a given potential. With electrode A, on increasing the potential in a negative direction the amount of CH 4 increased, accompanied by a decrease in the amounts of H 2 and CO, and the SP value was positive and shifted in a more positive direction, the TPPE activity increased and in the O1s XPS spectra a peak assigned to adsorbed oxygen developed. The amount of C 2 H 4 was greater in the potential range where both metallic Cu and Cu 2 O existed. With electrode B, the main product was H 2 , the SP value was negative, the TPPE activity was much smaller and Cu 2 O existed more preferentially than metallic Cu. With electrode C, the surface underwent oxidation easily when immersed in solution. With increasing plasma treatment time the hydrocarbon products decreased, the SP value was lower and the TPPE activity was smaller. It is suggested that the adsorbed oxygen present at the electrode surfaces can lead to an increase in the number of electrons available at the surfaces and also contribute to the adsorption of CO 2 , resulting in hydrocarbon production.

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Temperature-programmed photoelectron emission technique for metal surface analysis

Cited by 16 publications

References 8 publications

Observation of Real Metal Surfaces by Tribostimulated Electron Emission and Its Relationship to the Analyses by XPS and Photoemission

Observation of Real Metal Surfaces by Tribostimulated Electron Emission and Its Relationship to the Analyses by XPS and Photoemission

Using Temperature-Programmed Photoelectron Emission (TPPE) to Analyze Electron Transfer on Metallic Copper and Its Relation to the Essential Role of the Surface Hydroxyl Radical

Electrochemical reduction of CO₂ at copper electrodes and its relationship to the metal surface characteristics

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Temperature-programmed photoelectron emission technique for metal surface analysis

Cited by 16 publications

References 8 publications

Observation of Real Metal Surfaces by Tribostimulated Electron Emission and Its Relationship to the Analyses by XPS and Photoemission

Observation of Real Metal Surfaces by Tribostimulated Electron Emission and Its Relationship to the Analyses by XPS and Photoemission

Using Temperature-Programmed Photoelectron Emission (TPPE) to Analyze Electron Transfer on Metallic Copper and Its Relation to the Essential Role of the Surface Hydroxyl Radical

Electrochemical reduction of CO2 at copper electrodes and its relationship to the metal surface characteristics

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Electrochemical reduction of CO₂ at copper electrodes and its relationship to the metal surface characteristics