[en] X-ray beam damage is often observed during surface analysis of beam sensitive materials as indicated in the introduction to this issue and in a wide variety of references. While damage occurs in a wide range of materials, those that are most susceptible to damage are materials that contain low energy covalent bonds such as polymers or other organic materials. Even amongst the relatively easily damaged polymers, there is a wide range of damage rates. The data reported in this submission was collected in the interest of comparing the rates of damage produced by x-ray and electron irradiation of different materials. The focus of this submission is x-ray damage of bulk poly(vinyl chloride) PVC since it is a readily available material. The temperature of the sample holder was controlled during irradiation of the PVC in order to determine the extent to which localized sample heating affects the rate of damage. PVC degrades by photoionization, resulting in the production of HCl through H and Cl bond cleavage. Bulk PVC has previously been the focus of an x-ray damage study involving many laboratories throughout the world. For comparison to the bulk PVC data, damage rates for thin films of poly(2-chloroethyl methacrylate) (PCEMA) are also reported for the same three temperatures. Measurements of several relatively common materials on one instrument can provide a data base that allows damage rates on one instrument to be linked or compared to other damage data in the literature. In addition to the PCEMA films and bulk PVC, other data collected at the same x-ray parameters include thin films of PVC (for which damage rates are essentially identical to the bulk material) and of poly(acrylonitrile) PAN which is more stable that either PCEMA or PVC. An additional set of PVC data for a different instrument is also included in the volume. X-ray beams used for XPS produce less damage in materials than electrons used for AES analysis. This is due to both th e weaker interaction between x-rays and materials (relative to electrons) and the deeper penetration of x-rays into the material producing a lower damage density. Although the rates of damage for x-rays and electrons differ, many of the processes are similar. Both electron and x-ray damage has been collected for PVC and PAN as reported in this volume of SSS8,9,12 and summarized in the introduction. The overall damage rates for PVC and PAN differ by an order of magnitude, but the ratios of the electron and x-ray damage rates for these two materials are nearly the same

[en] AES spectra of spun-cast films of poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) were collected over a period of time to determine specimen damage during exposure to a 10kV electron beam. For the PVC, loss of chlorine was observed over a period of 203 minutes to the extent that the final chlorine concentration was only 20% of its original value. PAN exhibited a loss in nitrogen content over a period of 120 minutes, but the rate of damage to the polymer was significantly less than PVC. Figure 1 shows the atomic concentration in the PVC film as a function of dose (time). It takes a dose of approximately 7.0x10-5 Ccm-5 for the chlorine concentration to fall from its original value by 10% (one definition of critical dose). Figure 2 shows a similar drop in nitrogen concentration in the PAN film as a function of dose. For this polymer, it takes a dose of 1.3x10-3 Ccm-2 for the nitrogen concentration to fall by 10%

[en] X-ray beam damage is often observed during surface analysis of beam sensitive materials as indicated in the introduction to this issue and in a wide variety of references. While damage occurs in a wide range of materials, those that are most susceptible to damage are materials that contain low energy covalent bonds such as polymers or other organic materials. Even amongst the relatively easily damaged polymers, there is a wide range of damage rates. The focus of this submission is on poly(2-chloroethyl methylacrylate) [PCEMA] films. In order to determine the extent to which localized sample heating could influence damage rates the temperature of the substrate holding the PECMA was controlled during irradiation. PCEMA presumably degrades primarily by photo-ionization, resulting in the production of HCl through H and Cl bond cleavage. PCEMA has been recommended as a polymer for use as a reference for evaluating x-ray damage. PCEMA has been shown to be more sensitive to degradation than PVC which has also been used as a damage sensitive material useful for comparison of damage rates. Measurements of several relatively common materials on one instrument can provide a data base that allows damage rates on one instrument to be linked or compared to other damage data in the literature. Therefore for purposes of comparison, damage rates for bulk PVC at the same three different temperatures used for the PCEMA data have been collected and are also presented in this volume. Other data collected at the same x-ray parameters include thin films of PVC (for which damage rates are essentially identical to the bulk material) and of poly(acrylonitrile) PAN which is more stable that either PCEMA or PVC

[en] XPS spectra of a spin-coated film poly(vinyl chloride) (PVC) were collected over a period of 243 minutes at 303 K to determine specimen damage during long exposures to monochromatic Al Ka x-rays. For this PVC film we measured the loss of chlorine as a function of time by rastering a focused 104.6 w 100 um diameter x-ray beam over a 1.4 mm x 0.2 mm area on the sample

[en] XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-δ are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-δ and TlBa2CaCu2O7-δ, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society

[en] Due to their technological importance and an increasing scientific interest, a set of data from oxide surfaces has been collected for publication in two special issues of Surface Science Spectra. This Introduction to these two special issues summarizes the data to be presented and provides short overviews of trends in both the physics and chemistry of metal-oxide surfaces and of some important aspects of the techniques used to examine these surfaces. The surface spectroscopies discussed in relation to oxides include: valence band photoemission (ultraviolet photoelectron spectroscopy and synchrotron based), core level photoemission (x-ray photoelectron spectroscopy, XPS), Auger electron spectroscopy (AES), (reflection) electron energy loss spectroscopy (R)EELS, high-resolution electron energy loss spectroscopy (HREELS), scanning probe methods, and ion scattering spectroscopy (ISS). Brief sections also discuss the nature of stoichiometric oxide surfaces, the physics and chemistry of defects on these surfaces, and adsorption on metal-oxide surfaces.copyright 1998 American Vacuum Society

[en] XPS spectra of HS(CH₂)₁₅ COOH terminated a self assembled monolayer (SAM)sample was collected over a period of 242 minutes to determine specimen damage during long exposures to monochromatic Al Ka x-rays. For this COOH terminated SAM we measured the loss of oxygen as a function of time by rastering a focused 100 W, 100 um diameter x-ray beam over a 1.4 mm x 0.2 mm area of the sample.

[en] The spin-resolved photoemission spectra were successfully obtained from La0.7Sr0.3MnO3 190 nm thick epitaxial film on SrTiO3(001). Well below Tc the results clearly manifest the half-metallic nature, i.e., for the majority spin, the photoemission spectrum clearly shows a metallic Fermi cut-off, whereas for the minority spin, it shows an insulating gap with disappearance of the spectral weight at ∼0.6 eV binding energy. On heating through Tc the spectra show no difference for different spins and the spectra weight at the Fermi level (EF disappears, indicating that the Mn 3d spins become disordered) and the system undergoes the ferromagnetic metal to paramagnetic non-metal transition. (c) 2000 American Vacuum Society

[en] The interactions between a variety of ultrathin metal overlayers and the TiO₂(110) surface have been the focus of many studies in recent years as part of an effort to understand the chemistry of metal/ceramic interfaces. Aluminum reacts strongly with the stoichiometric, nearly defect-free TiO₂ surface, and we were interested in determining if we could alter this interaction by chemically modifying the TiO₂ surface with potassium prior to Al deposition. Potassium is of interest because of its use as a promoter in oxide-supported catalysis systems. In this article, we present XPS data for the interaction of Al and K (separately) with clean stoichiometric TiO₂, as well as data for the interaction of Al with a TiO₂(110) surface covered with a monolayer of K.copyright 1998 American Vacuum Society

[en] We present high resolution (40 meV) angle-resolved photoemission data from cleaved single-crystalline surfaces of the layered colossal magnetoresistive oxide La1.2Sr1.8Mn2O7. The sample was in the low temperature ferromagnetic state at T=10 K, well below the phase transition temperature of T=126 K. Full valence bands containing Mn 3d and O 2p states are shown, as well as blowups of the near EF spectra which are made up of the eg symmetry Mn 3d-O 2p hybrid states. k-vectors span the Brillouin zone center (0,0) to the zone face (π,0). (c) 2000 American Vacuum Society