The sample holder wae grounded (in the case8Īnd c> ungrounded (in the cases of b and d).Įach) intoa pellet.Therefore the contact resistance between The powdered sample was pressedĪ gold sheet.
(in the cases of a and b) and subsequent 10 minutes water Bi4f XPS spectra of BSCCO sample after 7 days air expo. Pressing the powders (small grains with diameter about lpm forĢ. Their room temperature resistivities 8pe usually ranging from IO-' to 10m3 ohm-cm.įurthermore, the bulk superconducting samples are prepared by High-l, superoonduotor YBCO and BSCCO show a "quasi-metallio"īehavior in reeistivity at room temperature. High-l, superconduotors than for insulating materials such asĬuO, BaO and Y203. Inhomogeneous sample charging csn be muoh more severe for the This increases their kinetio energy distribution and hence peakīroadening or splitting occurs. Photoelectrons are esoaping from areas of unequal potential. 2 have been attributed to inhomogeneous sampleĬharging which means that different areas of a sample chargesĭifferent amounts during the photoionimation process. The difference in the line shape between a and b in bothįig. 2) and one set of spin-orbit doublet for ungrounded sample Sets of Bi4f spin-orbit doublets for grounded sample (line a in Sample holder was a) grounded b) ungrounded. The powdered sample was pressed onto a gold sheet. 1 Ba3d XPS apeotra of YBCO sample after 8 months air exposure. Similar phenomena have been obsemed for snperconductor BSCCO. In thisĬase one set of spin-orbit doublet is observed. Holder was ungrounded and then the line b was recorded. Therefore, it is unlikely that theĮnergy shift in line a is from chemical shift due to existence Less than 0.5eV), and present work also shows that The Ba3d5,2īinding energies for BaO, Ba(OHj2 and BaC03 are 780.0, 780.2,Īnd 779.9eV respectively. Have been obsemred for different Ba compounds (15,161 (usually Reported in literatures, and they have been attributed to aĬoexistence of mixed valences such as Baa end Ba+2 (41, Ba+2 andīa+2+6 (51, Ba+2 and Ba+2'6 (61, or Ba+2 in lattice and Ba+2 inĬarbonate (3,7) in YBCO system. Phenomena of peak asymmetric broadening or splitting have been TheĮnergy shift between peaks 1 and 2 is about 2.5eV. Two sets of spin orbit doublets are observed. In the case of line a the sample holder was Powdered ySC0 was pressed onto a gold sheet and then mounted on 1 shows the Ba3d spectra for superconducting YBCO. The room temperature resistivities for them are ranging fromįig. The zero resistance temperatures for them are about 90K and 80K respectively. Were prepared by solid state reaction (13,141. Superconductors YBCO (YBa2Cu30_7) and BSCCO (Bi,Sr,Ca,Cu20x) Sample holder which can either be grounded or ungrounded. Of the methods, the sample was then mounted on the conducting The following sample preparation methods were usedįor XPS measurements of-high-Tc superconductors: 1. We have investigated the inhomogeneous charging problem in XPSĪn KRATOS ES300 electron spectrometer was used to record Measurements of the high-T, superconductors. Therefore it is necessary to reveal theįactors which may cause the peak broadening or splitting in XPS Superconducting Bi-Sr-Ca-Cu-0 (BSCCO) system can be found in Similarĭisagreements about the chemical states of the cations in Mainly divalent based on their XPS measurements. Reported that the valence of copper (8,9) and barium (9) is This inforis mainlyĮxtracted from the shoulders or broadened Presence of mixed valences are found for copper ions (l-3) andīarium ions (2-7) in the Y-Ba-Cu-0 (YBCO) system. Of elemental valence states in the superconducting materials Over the past two years several works on investigation Of the individual components in the high-T, superconducting That the superconductivity may be related to the mixed valences Of the high-To superconductivity, and it is smths The spectrometer or the sample is mounted on the insulatingĪt present it is of great interest to elucidate the origin
Sample charging oan be diminished when the sample is heated in Readily with atmospheric H20 and CO2 to form insulating reactants on the surface. Reaistivity at room temperature and the materials react very Superconducting materials show a quasi-metallio behavior in This has been ascribed to the reasons that the More severe for the superconducting materials than for insulating materLala. The results show that inhomogeneous sample charging can be much Superconducting Y-Ba-Cu.0 and Bi-Sr-Ca-Cu-0 has been studied. INHOMGGBNF0US CHARGING PROBLBM IN XPS MEASUREMENT OF SURFACX CGNTAMINATED HIGH-T=SUPBRCGNDUCI’INGMATERIAL Journnl of Electron Spectroscopy and Related Phmmnenu, 52 (1990) 395-404Įlsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
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