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Surface analysis is of critical importance to most of the Divisions of the American Vacuum Society and has been one of the most dynamic scientific and technological growth areas for the last 30 yr. The ASTM Committee E-42 on Surface Analysis was formed in 1976 to help advance the quality of surface analysis by developing appropriate standards (reference materials, reference data, and reference procedures), and by leading round robin comparisons, preparing publications, and holding symposia and workshops. A major function of the committee has been the development of standards and reference procedures. This article is a description of the organization of Committee E-42, and a summary of recent activities by this volunteer group with an emphasis on the processes used, a description of standards published, and standards that are being developed by Committee E-42 and other international organizations.

Metal overlayers deposited in vacuum onto self-assembled monolayer (SAM) systems serve as models for more complex metalized polymers. Metals (M) deposited onto SAMs with different organic functional end groups exhibit a wide range of behavior, ranging from strong chemical interactions with the end group to complete penetration of the metal through the SAM. In this work, we have characterized the interactions of Cu with the COOH of mercaptohexadecanoic acid (MHA, HOOC(CH 2 ) 15 SH) SAMs self assembled on gold films by using X-ray photoelectron spectroscopy (XPS) to examine the chemical interactions, and a combination of XPS and ion scattering spectroscopy (ISS) to deduce the growth mode and penetration rate of the deposited Cu. We found that submonolayer amounts of Cu react with HOOC, whereas the rest of the Cu remains metallic and penetrates beneath the SAM surface to the SAM ∣ Au interface. Considerable amounts of Cu (5 nm or more) will penetrate beneath the SAM layer, which is ca. 2.5 nm thick, despite the submonolayer presence of Cu at the SAM surface. The penetration rate depends strongly on the Cu deposition rate. Depositing copper onto MHA at 220 K or less, or using faster Cu deposition rates, results in slower or even completely suppressed penetration of the Cu through the SAM layer, whereas exposure to X-rays greatly enhances the penetration rate of large amounts of Cu through the SAM layer. The reacted copper is, based on the XPS 2p and LMM peaks, in the +2 oxidation state, but cannot be identified with a simple, stoichiometric oxide such as Cu 2 O, CuO, or Cu (OH) 2 .

The interaction of vacuum deposited Ni with the COOH organic functional groups of mercaptoundecanoic acid [HS(CH2)10COOH] self-assembled monolayers formed on an Au substrate has been characterized with in situ x-ray photoelectron spectroscopy. Steady loss and complete disappearance of the hydroxyl component of O 1s peak at 532.8 eV provides evidence for the formation of a Ni–O bond at the Ni/COOH interface. Further evidence for interfacial compound formation is provided by a binding energy shift in the high binding energy component of the Ni 2p3/2 peak from 854.8 to 854.4 eV for Ni coverages below ∼0.2 nm. These results are consistent with the donation of electrons from the deposited Ni to the COOH oxygens at low Ni coverages. The absence of the characteristic satellite feature in the Ni 2p peak excludes the possibility that a full electron charge is donated to each COOH organic functional group as a bidentate complex. However, the data are consistent with a two step reaction mechanism in which Ni initially reacts weakly with the oxygens in COOH below one monolayer coverage and then forms a complex above this coverage.

Prototype electrochromic windows made by several different US companies have been tested in our laboratory for their long-term durability. Samples were subjected to alternate coloring and bleaching voltage cycles while exposed to simulated 1-sun irradiance in a temperature-controlled environmental chamber with low relative humidity. The samples inside the chamber were tested under a matrix of different conditions. These conditions include: cycling at different temperatures (65, 85 and 107°C) under the irradiance, cycling versus no-cycling under the same irradiance and temperature, testing with different voltage waveforms and duty cycles with the same irradiance and temperature, cycling under various filtered irradiance intensities, and simple thermal exposure with no irradiance or cycling. The electro-optical characteristics of the samples were measured between 350 and 1,100 nm every 4,000 cycles for up to 20,000 cycles. Photographs of the samples were taken periodically with a digital camera to record cosmetic defects, the extent of residual coloration, and overall coloration and bleaching uniformity of the samples. Our results indicate that the most important cause of degradation is the combination of continuous cycling, elevated temperature and irradiance. The relative importance of these variables, when considered synergistically or separately, depends on the particular device materials and design.

The authors propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO{sub 3{minus}y}{center_dot}nH{sub 2}O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W{sup 6{minus}} and W{sup 4{minus}} states and can be represented as W{sub 1{minus}y}{sup 6+} W{sub y}{sup 4+}O{sub 3{minus}y}{center_dot}nH{sub 2}O. The proposed chromic mechanism is based on the small polars transition between the charge-induced W{sup 5+} state and the original W{sup 4+} state instead of the W{sup 5+} and W{sup 6+} states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were used to characterize octadecanethiol [ODT, HS(CH2)17CH3] and methylmercaptohexadecanoate [MMHD, HS(CH2)15COOCH3] self-assembled monolayers (SAMs) before and after depositing up to 1.0 nm Cu at ca. 10−7 Torr. Results from XPS O 1s, Cu 2p, and C 1s spectra do not indicate that a complex is formed (no chemical shifts) between Cu and the COOCH3 of MMHD or ODT organic functional groups (OFG) at 295 K. Although no direct evidence for Cu/COOCH3 interactions is evident, the initial value for ISS Cu peak intensities for 1.0 nm of Cu on COOCH3 of MMHD requires 7 h before it disappears compared with less than 150 min for Cu on CH3 of ODT. These times are also bracketed from XPS results, which are less sensitive than ISS to loss of copper from the M/SAM surface. The longer penetration time through MMHD versus ODT might be explained by weak interactions between Cu and COOCH3 of MMHD by different defect densities in the SAMs. The actual C...

We briefly summarize ethylene-vinyl acetate ( EVA ) reliability issues and report our R&D results. These results include EVA degradation effects, discoloration factors, approaches to mitigate the EVA discoloration, improved photostability of modified EVA formulations, and plans to identify the best encapsulation schemes and to develop appropriate methodologies for predicting service life of PV modules.

In the present work, x‐ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were used to characterize mercaptoundecanoic acid [MUA, HS(CH2)10 COOH] and mercaptohexadecanoic acid [MHA, HS(CH2)15COOH] self‐assembled monolayers (SAMs) before and after depositing up to 1.0 nm Ag at ∼10−7 Torr. Results from XPS O 1s, Ag 3d, and C 1s spectra do not indicate that a complex is formed (no chemical shifts) between Ag and the COOH of MUA or MHA at 295 K. Although no direct evidence for Ag/COOH interactions is evident, the initial value for ISS Ag peak intensities for 1.0 nm of Ag on COOH of MHA is unchanged after 1 h and is only reduced to 68% of the initial value after 15 h. For MUA, the ISS Ag peak intensity for 1.0 nm is constant for about 5 min and is gradually reduced until it is not detectable about 90 min after Ag deposition. These results and those we obtained earlier for Ag on octadecanethiol [ODT, HS(CH2)17CH3] might be explained by weak or no interactions between Ag and COOH and by d...

Transmissive solid-state electrochromic devices based on the structure of WO[sub 3]/lithium-polymer electrolyte/V[sub 2]O[sub 5] were optimized for potential large-area window applications. The electrochromic layer thicknesses, polymer molecular weights, lithium-containing electrolytes, preassembly lithium-ion injection amounts, and transparent conductor substrates were systematically investigated for large optical modulation and fast response of the devices. The transmittance of the optimized device at 633 nm can be switched between 74 and 12% in 1 min. The coloring and bleaching voltages were [minus]1.8 and 1.2 V, respectively.

Ion scattering spectroscopy (ISS) of vacuum deposited Ag on octadecanethiol (ODT, HS(CH2)17CH3) organized molecular assemblies (OMAs) provides a means of studying interfacial structure at metal/organic interfaces under controlled conditions. The OMAs were self‐assembled onto gold films on silicon 〈100〉 substrates. ISS compositional depth profiles of the Ag/CH3 interface were performed at a number of temperatures between 113 and 293 K. Results from these experiments show clearly that Ag penetrates rapidly through ODT above ∼200 K. The changes in ISS Ag peak intensities as a function of time and temperature provide evidence for the formation of Ag clusters at the ODT/Au interface after penetration of Ag. Changes in deposition rate between 0.003 and 0.015 nm/s yielded little difference in corresponding ISS depth profiles. Over a range of ion beam current densities from 0.06 to 2.0 μA/cm2, scaled compositional depth profiles were found to be comparable within experimental error.

The dependence on substrate temperature of the formation of Cr(CN) complexes and Cr‐carbides when Cr overlayers are deposited onto organized molecular assemblies (OMAs) has been investigated in situ by x‐ray photoelectron spectroscopy (XPS). At Cr coverages of 6 A or less, evidence for the formation of a Cr(CN) complex with the CN end groups of the 12‐mercaptododecanenitrile OMA is found in negative binding energy shifts of the nitrile part of the C 1s line shape and of the N 1s core level. The N 1s negative binding energy shift increases from 0.1–1.2 eV for substrate temperatures from 173 to 373 K. At a Cr coverage of 6 A, Cr‐carbide was observed to form to a similar extent on the 12‐mercaptododecanenitrile and octadecanethiol OMAs. The number of carbide C atoms per OMA chain increases from 0.7 to 3 for substrate temperatures from 173 to 373 K for 6 A Cr on the 12‐mercaptododecanenitrile OMA. Greater amounts of carbide result when the Cr is deposited onto a sample at a given temperature, T, than when the deposition at a lower temperature is followed by warming to T. We interpret the increased amount of carbide to result from a contribution of the incident Cr atom kinetic energy to the activation of the Cr‐carbide reaction. Collateral effects of x‐ray exposure and substrate temperatures greater than 295 K may have affected, in part, the observed binding energy shifts and peak heights, but do not compromise the general conclusions of our interpretation.

The purposes of this paper are to provide background information about encapsulants for photovoltaic (PV) modules and to evaluate estimates of the durability of different materials used in PV modules. The authors summarize the field-deployed module degradation in performance, the established degradation mechanisms of ethylene vinyl acetate (EVA) copolymer, and potential degradation mechanisms in other module components and at materials interfaces. Most of the emphasis is on estimates for the commercially used EVA formulations A9918 and 15295. These formulations have degraded in field-deployed modules to produce acetic acid and a yellow to brown color from polyenes and the module efficiencies have been reduced by 10% to 70% in 4 to 12 years. Yet, projections were made by several different research groups in the 1980s that the EVA lifetime could range from 20 to 100 years, the production of acetic acid would only be 0.006% in 20 years, and that silver metallization would survive attack from acetic acid for 300 years at 55 C. Those authors did not use appropriate variables or specimen configurations that simulate reality, and based their projections using the generalization that chemical reaction rates double for every 10 C increase in T. The authors review the inherentmore » errors in their assumptions about the Arrhenius relation. They also show how degradation in efficiency (from current-voltage data) comparable to field experience is obtained using minimodules with a construction that simulates reality and by using appropriate variables in accelerated testing, i.e., UV, T, and RH. A test protocol is outlined that simulates reality and permits making suitable service lifetime projections.« less

Emerging advanced multilayer renewable energy devices, such as reflector materials and photovoltaic modules, are expected to exhibit significantly increased service lifetimes compared to existing devices. Such devices must be capable of 20 to 30 years of operation under harsh outdoor weathering conditions. Industrial manufacturers cannot afford to wait extended periods of time to determine whether such lifetimes are realistic. Consequently, a flexible, robust, and accurate method for predicting the service lifetime of such devices is essential. Two requirements for developing such a method are first, to correlate the accelerated lifetime test methods with anticipated life under real-world operating environments; and second, to establish statistical models for predicting service lifetimes based on environmental stress factors. The relative significance of the weathering stress factors ultraviolet light (UV), temperature (T), and relative humidity (RH) was ascertained. Optical properties of new reflector materials were measured and their loss of performance with exposure time was modelled as a function of an appropriate combination of stress factors. Then, the functional relationship between performance measurements and time in accelerated lifetime tests was investigated. The basic framework of this approach is SPt analysis because it intends to explain the bridge functions from Stresses (S) to Performance (P) and from Performance to lifetime (t) of the materials. The results show that the cumulative dosage of ultraviolet radiation between 290-320 nm (UV-B) with synergistic effects of T and RH is a very critical factor in inducing performance loss. Finally, the SPt model developed for accelerated laboratory data was verified for data obtained from outdoor sites, and excellent agreement was found.

The interaction of evaporated copper overlayers, from 0.03 to 0.4 nm thick, with specific terminal functional groups of an organized molecular assembly (OMA) of HS(CH2)11CN formed on gold has been studied by x‐ray photoelectron spectroscopy. For average copper coverages above 0.1 nm, the peak intensities show fair agreement with a model that assumes an increasing fraction of each increment of the deposited copper penetrates the OMA and resides at the OMA/Au interface. For lower coverages, a weak Cu(CN) interaction is indicated by shifts of the N 1s level and the C 1s high binding energy (HBE) shoulder to lower binding of as well as by the presence of a Cu 2p HBE shoulder.

ISS and XPS spectra were recorded before and after forming an organized molecular assembly (OMA) of HS(CH2)10COOH, 11-mercaptoundecanoic acid (MUA) on 20 nm thick gold thin films on a silicon substrate. The MUA/OMA is attached to gold via the thiol (SH) group, and the acid group (CO2H) becomes the outer monolayer. At low current densities, l keV 3e+ ISS showed no detectable amount of gold on the surface, indicating the gold film was completely covered by the OMA. XPS signals acquired from the OMA showed carbon, oxygen, sulfur, gold, and a trace of silicon. When using ISS at higher current densities to sputter the OMA, the same elements were detected. The presence of silicon at the Au/OMA interface is attributed to silicon diffusion from the substrate through 20 nm of gold at 22°C. Some potential uses of ISS for studying well-characterized OMAs are also suggested. The primary purpose of this work is to use the surface-monolayer sensitive ISS technique on a well-characterized OMA on gold to confirm conclusions reached in prior work about the coverage of gold films by the OMA. ISS of self-assembled MUA on gold has not been previously reported, and our results have provided additional interesting information.

Using concentrated natural sunlight at the NREL High Flux Solar Furnace, we have exposed several materials to acceleration factors of up to 400 times the normal outdoor UV exposure dose. This accelerated rate allows the exposure of materials such that a year of outdoor exposure can be simulated in about 5 hours. We have studied the solarization of cerium containing glass, the degradation of ethylene vinyl acetate laminated between borosilicate glass, and the yellowing of standard polystyrene test coupons. The first two candidates are of interest to the photovoltaics (PV) program, and the last candidate material is a widely used dosimeter for ultra violet (UV) exposure in accelerated weathering chambers

Results from extensive studies of the commercial ethylene vinyl acetate (EVA) formulations show that the UV absorber and curing-generated UV-excitable, α,β-unsaturated carbonyl chromophores facilitate the EVA discoloration, which is further enhanced by curing-generated acetic acid and probably residual peroxide curing agent also. Formation and concentration of the UV-excitable chromophores are substantially promoted by the antioxidant, Naugard P. The discoloration rate is greater under higher UV light intensity and temperatures. Heating in the dark at elevated temperatures (e.g., 85 °C) in the air for ∼200 days only results in light yellowing. The discoloration reactions compete with photobleaching reactions, which destroy curing-generated chromophores and result in non-discoloring of EVA. By using better performance stabilizers to minimize the curing-generated UV-excitable chromophores, a new fast curing agent, and no UV absorber, the NREL-developed EVA formulations show a superior photothermal stability against browning to the commercial counterparts. Alternatively, the discoloration rate of the commercial EVA pottants can be considerably reduced by using UV-filtering glass superstrates that largely inhibit the UV-induced photooxidation reactions, or completely eliminated by using air-permeable polymer superstrate films that enable photobleaching reactions.

Forty-eight PV modules of four different types were instrumented and tested monthly for 3 years to measure and record the performance effects of environmental exposure. Two modules were removed from each set of 12 as a control and for “initial” characterization. As a secondary goal, the effects of mounting topology (open rack, integrated roof, conventional standoff mount) were also closely monitored. Current-voltage (I-V) curve data were archived and normalized according to accepted methods. The EVA pottant in all modules monitored was discolored to a deep yellow-to-brown color from prior exposures before the monitoring was begun. Modules showing observable performance degradation were removed from their mounts and prepared for in-depth analysis. During the 3-year monitoring period, 4 of the 10 Solarex a-Si modules stopped producing, 3 of the 10 Solarex MIT pc-Si modules lost from 5% to 10% efficiency, and 1 Mobil Ra-180 pc-Si module lost about 10% efficiency. For all of the other modules, a loss of less than 1% per year was recorded, which included all 10 of the Sovonics P-101 a-Si modules.

The purposes of this paper are to elucidate the crucial importance of predicting the service lifetime (SLP) for new photovoltaic technologies (PV) modules and to present an outline for developing a SLP methodology for encapsulated PV cells and minimodules. Specific objectives are (a) to illustrate the essential need and generic nature of SLP for several types of existing solar energy conversion or conservation devices, (b) to elucidate the complexity associated with quantifying the durability of these devices, (c) to define and explain the seven major elements that constitute a generic SLP methodology, (d) to show that implementing the SLP methodology for developing laboratory-scale PV cells and minimodules can reduce the cost of technology development, and (e) to outline an acceptable methodology for relating accelerated life testing to real time testing, using sufficient sample numbers, and applying the methodology in (c) for predicting a service lifetime. The major conclusions are that predicting the s...

The overall purposes of this paper are to elucidate the crucial importance of predicting the service lifetime (SLP) for photovoltaics (PV) modules and to present an outline for developing a SLP methodology for encapsulated PV cells and minimodules. The specific objectives are (a) to illustrate the generic nature of SLP for several types of solar energy conversion or conversion devices, (b) to summarize the major durability issues concerned with these devices, (c) to justify using SLP in the triad of cost, performance, and durability instead of only durability, (d) to define and explain the seven major elements that comprise a generic SLP methodology, (e) to provide background about implementing the SLP methodology for PV cells and minimodules including the complexity of the encapsulation problems, (f) to summarize briefly the past focus of our task for improving and/or replacing ethylene vinyl acetate (EVA) as a PV pottant, and (g) to provide an outline of our present and future studies using encapsulated PV cells and minimodules for improving the encapsulation of PV cells and predicting a service lifetime for them using the SLP methodology outlined in objective (d). By using this methodology, our major conclusion is that predicting the service lifetime of PV cells and minimodules is possible.

The goals, objectives, background, technical approach, status, and accomplishments for the PV Module Materials and Encapsulation Research Task are summarized for FY 1994 and the first half of FY 1995. The accomplishments are reported in several elements, i.e., those effects related to degradation of ethylene vinyl acetate (EVA) copolymer and to using superstrates for PV cells. The EVA results are presented under the headings, encapsulation of PV modules using an EVA pottant, recommendation to use the 15295 EVA formulation instead of A9918, modified EVA and potential EVA replacements, degradation mechanisms, efficiency losses from yellowed EVA, and factors that affect the EVA discoloration rate, experimental procedures, and equipment acquisitions. The results on superstrate materials are presented in the appropriate sections on reducing the rate of EVA degradation and promoting photobleaching reactions in EVA.

The stabilization effects of various superstrate materials against UV‐induced EVA discoloration and the effect of photocurrent enhancement by white light‐reflecting substrates are summarized. Based on the results, some alternative PV module encapsulation schemes are proposed for improved module performance, where the current or modified formulations of EVA encapsulants still can be used so that the typical processing tools and conditions need not to be changed significantly. The schemes are designed in an attempt to eliminate or minimize the EVA yellow‐browning and to increase the module power output. Four key experimental results from the studies of EVA discoloration and encapsulation are to employ: (1) UV‐absorbing (filtering) glasses as superstrates to protect EVA from UV‐induced discoloration, (2) gas‐permeable polymer films as superstrates and/or substrates to prevent EVA yellowing by permitting photobleaching reactions, (3) modified EVA formulations, and (4) internal reflection of the light by white substrates.

The purpose of research on metals (M) deposited onto self-assembled monolayers (SAMs) is to understand the interactions between the metal and eventually metal oxide overlayers on well-ordered organic substrates. Applications of M/SAM and inorganic/SAM research results to the understanding of real inorganic/organic interfaces in vacuum and under environmental conditions can potentially play a key role in the development of advanced devices with stable interfacial properties. The results of selected M/SAM studies to date are reviewed, and MISAM combinations ranked according to reactivity and penetration. Specific examples of reactive interfaces (Cu/COOH, Cr/several groups) and nonreactive interfaces with penetration (Ag/CH3, Ag/COOH) are used to illustrate the extremes.

The goals, objectives, background, technical approach, status, and accomplishments on the PV Module Reliability Research Task are summarized for FY 1993. The accomplishments are reported in two elements, ethylene vinyl acetate (EVA) degradation and stability in CdTe/CdS modules. The EVA results are presented under the headings modified EVA and potential EVA replacements, degradation mechanisms, efficiency losses from yellowed EVA, and equipment acquisitions. The results on CdTe/CdS modules are presented under subheadings of stability of the SnO2/CdS interface and degradation at the CdTe/CdS interface.

Overlayers of Cr and Ni deposited at 22 °C and at -100 °C onto self-organized molecular assemblies of HS(CH2 )11 CN on Au have been studied by X-ray photoelectron spectroscopy (XPS). For the lowest overlayer coverages, the C ls and N is core levels show evidence for a chemical interaction between the deposited metal and the CN end-group. At 22 °C and for coverages of 0.6 nm or more, Cr/CN shows a C ls low binding energy, carbide-like shoulder. The degree of metal penetration is assessed based on the attenuation of the C ls and Au 4f intensities, and on the positions of the Cr and Ni 2p levels. In general, the least penetration and the largest binding energy shifts of the C, N, and the Cr or Ni core levels are observed for Cr/CN, while and Ni/CN shows smaller shifts and greater penetration.

The objectives of this document are to present an overview of the work accomplished to date on desiccant cooling to provide assessment of the state of the art of desiccant cooling technology in the field of desiccant material dehumidifier components, desiccant systems, and models. The report also discusses the factors that affect the widespread acceptance of desiccant cooling technology. This report is organized as follows. First, a basic description and historical overview of desiccant cooling technology is provided. Then, the recent research and development (R D) program history (focusing on DOE's funded efforts) is discussed. The status of the technology elements (materials, components, systems) is discussed in detail and a preliminary study on the energy impact of desiccant technology is presented. R D needs for advancing the technology in the market are identified. The National Renewable Energy Laboratory's unique desiccant test facilities and their typical outputs are described briefly. Finally, the results of a comprehensive literature search on desiccant cooling are presented in a bibliography. The bibliography contains approximately 900 citations on desiccant cooling.

Yellow‐browning of the ethylene‐vinyl acetate (EVA) copolymer encapsulant used in PV modules has resulted in significant power losses of over 50% of the initial power output. The weathering‐degraded yellow‐brown EVA films have lost the ultraviolet (UV) absorber, Cyasorb UV 531(R), and the degree of cross‐linking (gel content) has increased. EVA degradation mechanisms identified thus far are discussed in this work. Upon exposure to UV light at 45°–85 °C, virgin EVA films that are stabilized with Cyasorb UV 531(R) and two antioxidants show an increase in the gel content, a gradual loss of Cyasorb by photooxidation, and the generation of acetic acid. The deacetylation reaction, which leads to the formation of polyenes, also occurs significantly in the films heated in the dark at 130 °C for five days. Acetic acid thermally catalyzes the EVA film discoloration at 85°–130 °C, which increases from a light yellow to a yellow‐brown color as the heating temperature increases. The factors can account for the yellow‐...

X-ray photoelectron spectroscopy (XPS) spectra were recorded after sequential deposition of sub-monolayer amounts of copper on an organized molecular assembly (OMA) of HS (CH2) 10COOH, 11-mercaptoundecanoic acid (MUA) on 80-nm-thick gold films on clean silicon single-crystal substrates. The self-assembly process results in stable monolayers with the thiol group attached to the gold film and the COOH group as the outer monolayer. Copper deposited in vacuum interacts with the surface of the MUA OMA to produce a unidentate copper complex with the singly bonded oxygen atom of the acid monolayer. The data do not support forming a bidentate copper complex or chemical interaction of the double-bonded oxygen atom of the acid group with copper. The maximum charge residing on the copper atom of the complex is +1, with one charged copper atom on the surface per MUA molecule of the OMA.

The purposes of this chapter are (1) to provide a brief overview of the role of surface compositional analysis (i.e., surface analysis) in surface characterization, (2) to provide a brief overview of the methods of surface analysis involving ion bombardment of a solid or ion detection, and (3) to discuss briefly each of the methods of surface analysis using the ion spectroscopies that are not treated by the other chapters in this volume.Comparisons and contrasts of the most widely used methods of surface analysis are discussed in Chapter 7 of this volume. Extensive literature citations are provided, so that further details about surface analysis methods can be obtained. Both the surface (i.e., the outer monolayer of atoms on a solid)and the interface (i.e., the boundary between two compositionally different solids) are included in the term “surface” as it is used in this chapter.

The purpose of this chapter is to summarize and compare available information about the six major techniques for surface compositional analysis (SIMS, SNMS, ISS, RBS, AES, and XPS) in tabular form and in brief narratives. It is assumed that the reader is familiar with the principles of these techniques. Detailed information on the ion spectroscopies (SIMS, SNMS, ISS, and RBS) is presented in earlier chapters of this volume; information on the electron spectroscopies can be found in the references given below and in a forthcoming volume of this series. Acronyms and abbreviations used in this chapter are defined in Chapter 1 of this volume.

The interdiffusion of Cu and Si was studied using ion scattering spectrometry (ISS) and x‐ray photoelectron spectroscopy (XPS). The samples were prepared in very high vacuum (VHV) by evaporating Cu onto Ar+‐cleaned and ‐annealed Si(111) surfaces. The surfaces were transferred directly from VHV to UHV and analyzed by ISS and XPS. Diffusion was studied at 295 K, and then at temperatures up to 825 K. A comparison of data taken at the Cu–Si interface was made with Cu3 Si. Copper and Si interdiffuse rapidly at 295 K and above; diffusion is completed in

Most commercially made mirrors, consisting of a multilayer stack of glass/Ag/Cu/paint, are made using a wet electroless process. AES, XPS and SIMS have been used for compositional analysis during profiling to reach the Ag/glass, Ag/Cu, and Cu/paint interfaces as well as to analyze for impurities present in each layer of the mirror. A five-ligand coordinated tin complex is proposed as the initial configuration of tin on the glass surface prior to silver plating. This model is consistent with data from this work as well as from the literature. Surface analysis results from studies of complete mirror stacks and of partially made mirrors prepared in our laboratory reveal that some sensitizer and Ag reducer solution components are trapped during mirror formation at the Ag/glass interface and Cu reducer solution components are trapped at the Cu/paint interface. After real-time and accelerated life testing of completed mirrors, chloride was identified in copious amounts at the Cu/paint interface, and most probably originates from the paint over-layer. Results from samples aged for six months and one year suggest that iron from the glass segregates to the Ag/glass interface, Cu penetrates into the Ag layer, and oxygen penetrates into the Cu layer from the Cu/paint interface and/or Cu/air interface. Emphasis in the discussion is placed upon the chemistry at the Ag/glass interface and possible corrosion induced by impurities trapped at the Ag/glass and Cu/paint interfaces during mirror fabrication.

Adsorption isotherms have been measured on cleaned silver powder from 178 to 339°C at oxygen pressures of 0.226 Pa to 40 kPa using a vacuum ultramicrobalance. Adsorption equilibrium was found at all temperatures and pressures studied. The surface was prepared for the reproducible chemisorption studies and cleaned before the determination of each isotherm by an established method. Seven isotherms were measured that spanned the fraction of the surface covered ϑ from 0.17 to 1.0. The isosteric heat of adsorption q was determined by application of the the Clausius–Clapeyron equation at constant values of ϑ. From ϑ of 0.17 to 0.33, q decreases from 42 to 17.7 kcal/mol; it remains constant at 18.4±0.8 kcal/mol from ϑ of 0.33 to about 0.90, and then decreases to zero at the highest coverages and temperatures. By comparing the isosteric heat data with LEED and thermal desorption studies on Ag(111) by Rovida and coworkers, it is suggested the initial drop in q results from the formation of islands of surface silver oxide. The constant value is attributed to completion of the oxide layer and molecular adsorption on and/or through the oxide. The decrease in q at the highest coverages results from repulsions in the adlayer at T?275 and absorption at T≳302.

An overview of the topical coverage of a one‐semester, three‐hour course on solid surfaces, surface processes, and the solid/gas interface is presented. The main topical areas embracing the nature of the surface phase include topography, shape, depth, composition, purity, and structure, and the methods used to elucidate these parameters. The various theoretical and experimental categories for understanding adsorbate–adsorbent interactions are considered with particular attention focused on physical and chemical adsorption, desorption, and thermal desorption. Surface processes include surface diffusion and chemisorption as a precursor to oxidation and catalysis. The general emphasis of the course is on the experimental aspects of studying surfaces and the harmonious blending of backgrounds in physics, chemistry, materials, mathematics, and engineering for applied and fundamental surface science. The course is designed for graduate students and well qualified seniors majoring in science or engineering, or t...

Depth profiles of gold overlayers deposited onto 600‐A silver films have been obtained with ion‐scattering spectrometry. The overlayers, 50, 200, 400, and 800 A thick, were deposited at ∠10−4 Pa onto freshly deposited 600‐A thick Ag films. Complete coverage of the Ag underlayer was not achieved with the 50‐ and 200‐A Au layers. Detectable signals (ϑ≡0.001) of Ag could still be obtained even with a 400‐A Au overlayer. After aging for six to seven months at room temperature, the depth profiles show evidence for some bulk diffusion at the interface and a considerably enhanced accumulation of silver over the gold. The latter is attributed to preferred diffusion paths for Ag ’’through’’ and/or on the Au overlayer; calculated values of the mean‐square displacement for the several diffusion paths are compared for the dimensions of the film. A sputtering yield of 2.0 Au atoms per Ne ion was calculated for 1800‐eV neon ions incident at 45° onto the Au films.

The outdoor lifetimes for sheets of bisphenol-A polycarbonate (BPA-PC) having different concentrations of phenolic terminal groups were predicted as a function of the average terrestrial UV irradiance spectrum measured at several latitudes. The lifetimes were based upon chain scission rates predicted to occur in a thin surface layer of unstabilized BPA-PC sheet, and were less than the outdoor lifetime reported for sheets of stabilized material. These rates were derived from chain scission quantum yields measured at 287 and 308 nm in thin solid films of BPA-PC. In general, these rates will be extremely dependent on latitudinal, seasonal, and possibly diurnal variations in the wavelength distribution of terrestrial UV irradiance, and on the concentration of phenolic end groups. Reducing the concentration of phenolic terminal groups by a factor of two in commercial BPA-PC by acetylation (capping) lowers the chain scission quantum yield, reduces terrestrial UV absorbance, and nearly doubles the predicted outdoor lifetime of the material at North latitudes of 9°, 39°, and 71°. High concentrations of terminal phenolic groups in BPA-PC induce a cross-linking reaction which competes with chain scission at 308 nm and predominates at 287 nm.

To explain the recently observed redeposition of sputtered Au, Ag, and Cu, it is shown here that low energy ions sputtered from a plane metallic surface by an obliquely incident ion beam can be returned to the surface by the electrostatic fields of the beam and of the image charges of the sputtered ions. Trajectories for sputtered Au ions were obtained by numerical integration of the equations of motion. The ion image force dominates the motion near the plane (

Oxidation of aluminum by carbon dioxide at room temperature is significantly enhanced by an electron beam, and oxide growth is spatially restricted to the beam impact region. The growth of the oxide on aluminum films and sheets was studied with AES, XPS, ISS, and SIMS using isotopically labelled C18O2. XPS indicates that the oxide is similar to Al2O3 and that very little carbon accumulates on the surface. Both SIMS and ISS confirm that 18O is incorporated into the Al from C18O2. Residual gases and oxygen from the substrate are eliminated as possible oxygen sources for the oxidation. Beam heating is not a factor in enhancing the oxidation. Oxide islands were grown for a range of beam voltages (0.5–10 keV), beam current densities (0.8 mA/cm2–7 A/cm2) and CO2 pressures (10−6–10−4 Pa). No CO2 adsorption or Al oxidation was detected on a clean Al sheet in the absence of an electron beam. In the presence of the beam (2 keV, 7 A/cm2), surface oxygen saturated after 5000 L (langmuir) CO2 exposures. The mechanism ...

For determining the role of the polymer/copper oxide interface in the catalyzed oxidative degradation of polypropylene, copper films were deposited onto glass substrates and oxidized partially or completely to CuO0.67 in oxygen-16 or oxygen-18. The 44-nm-thick oxide films were then overlaid with 40 to 115 nm of isotactic polypropylene (pp) by a dip-coating process. The pp/CuO0.67/glass samples were heated in oxygen-16 at temperatures of 90, 100, 110, and 120°C in the presence or absence of getters for the product gases. Ion scattering spectrometry depth profiles were obtained for deposited copper films, partially and completely oxidized films (both labeled and unlabeled) , and for undegraded and oxidatively degraded polymer/oxide sandwiches. In the presence of getters, the copper oxide film is reduced by the polypropylene but is not reoxidized, leaving the copper oxide film partially reduced to copper. The 16 O 18 O ratio in the unreduced oxide remained unchanged from the original ratio. The degraded polypropylene was more difficult to sputter and the profile showed copper was present throughout the polymer thickness. In the absence of getters, the copper oxide film is reduced but reoxidized by the ambient oxygen used during the oxidative degradation. The 16 O 18 O ratio in the oxide after degradation exhibits a marked increase in oxygen-16. Extensive oxidation of the polypropylene is evident from the 16O signal in the polymer and, again, copper ions are found distributed throughout the polypropylene. The results show that reduction of the copper oxide by the polymer is part of the mechanism by which copper catalyzes polypropylene degradation. In the case corresponding to normal environments (no getters), partial reoxidation of the copper also occurs, so a reduction—reoxidation cycle at the copper/polymer interface is suggested.

The thermal oxidation of atactic polypropylene on CuO0.67 surfaces in air was studied using Fourier transform infrared reflection–absorption spectroscopy (FT–IR–RA). Degradative losses of primary, secondary, and tertiary alkyl hydrogens were observed. Films of CuO0.67 (55 nm thick) were prepared by the thermal oxidation at 122 °C of a copper film on 50 nm of gold, which was supported by a polished fused silica substrate. Thin films (70–200 nm) of purified atactic polypropylene were cast onto the copper oxide from xylene solution at 90 °C and air dried at 22 °C. The samples were heated in situ in the FT–IR–RA apparatus in synthetic or in laboratory air and then mounted for the IR–RA measurements from 600 to 5000 cm−1. At 60 and 73 °C, carboxylic acids are the primary degradation products, while at 85 and 100 °C, copper carboxylate formation predominates, and CuO0.67 is decomposed. The distinct change in the oxidative mechanisms between 73 and 85 °C apparently is related to an irreversible thermal transitio...