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The formation of a high quality interface between metallic and organic semiconducting thin films is critically important in achieving high-performance organic electronics devices. In this regard, the importance of understanding the multifaceted issue of structure damage incurred to organic films by the evaporated metal atoms cannot be overstated. In the present study, we have investigated the change of a structurally ordered, organic semiconducting (o.s.) thin film of 5,11-bis(triethylsilylethynyl)anthradithiophene (TESADT) effected by gold atoms by means of synchrotron-based soft X-ray spectroscopies including ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopies (XPS) with imaging capability, near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and atomic force microscopy (AFM). This work shows that gold atoms readily diffuse into the organic films and nucleate into nanometer-size clusters, damage chemical structure, destroy structural ordering of the organic fi...

Leguminous green manure is an important source of nitrogen (N) and carbon (C) in cropping systems. The fast turnover of leguminous green manure enables it to release N quickly, but limits its effectiveness in maintaining soil organic C content. Converting leguminous green manure into biochar facilitates its use as a soil amendment. In this study, we assessed how the conversion of leguminous green manure (Sesbania roxburghii) into biochar altered its chemical composition and subsequent C and N mineralization. Biomass was charred along a temperature gradient from 200 to 500 °C. Using nuclear magnetic resonance and near-edge X-ray adsorption fine structure spectroscopy, we found that both C and N became enriched in aromatic and heterocyclic aromatic structures in biochar, and this structural change led to a reduction in C and N mineralization rates. The mineralized C decreased from 32.7% of the added C of raw biomass to

The Ir(111) surface is oxidized with gas-phase oxygen atoms under vacuum condition to achieve an oxidation level beyond its saturation coverage for chemisorption. Two surface oxides, rutile IrO2 of (100) domain and corundum Ir2O3 of (001) domain, have been grown at 550 K with different oxygen exposure of 3.6 × 105 L and 7.2 × 105 L respectively. The temperature programmed desorption (TPD) experiment of rutile IrO2(100) shows its desorption curve (at 4 K s− 1) peaks at 750 K, followed by a long tail of less pronounced desorption features. On the other hand, TPD of corundum Ir2O3(001) displays a symmetric trace, peaking at 880 K. Carbon monoxide titration experiments show that adsorbed CO reduces corundum Ir2O3(001) at 400 K, but CO does not adsorb on rutile IrO2(100) and no reduction reaction occurs. Evidently, among the two surface oxides, corundum Ir2O3(001) involves in catalysis of carbon monoxide oxidation, while rutile IrO2(100) does not. The formation of two surface oxides is also compared, we conclude that the atom arrangement favors Ir2O3(001) at the oxide/metal interface.

Temperature-programmed reaction/desorption, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure in combination of calculations based on density functional theory have been employed to investigate adsorption and reaction of 1,3-C6H4I2 on Cu(100). At 100 K, the surface species after 1,3-C6H4I2 adsorption are found to be 1,3-C6H4I2, C6H4I, and 1,3-C6H4. The formation of these adsorbates is dependent on the adsorption sites of 1,3-C6H4I2. 1,3-C6H4I2 adsorbed with the ring at a hollow site and parallel to the surface is predicted to be unstable and preferentially leads to C–I bond dissociation. 1,3-C6H4, the intermediate from 1,3-C6H4I2 decomposition, has a tilted adsorption geometry with a distorted ring. H2 is the only reaction product observed after 550 K in the 1,3-C6H4I2 decomposition on Cu(100), with all of the carbon atoms left on the surface. Dimerization of 1,3-C6H4 molecules on Cu(100) has been described computationally, showing an activated an...

Solvent–vapor annealing was used to increase the field-effect mobility of soluble triethylsilylethynyl anthradithiophene spin-coated on organosilane-terminated silicon dioxide, yielding a high value of 1.2 cm 2 V −1 s −1 . The cause of improvement was investigated by atomic force microscopy, X-ray diffraction, and near-edge X-ray absorption fine structure spectroscopy. Vapor annealing exerts little effect on the molecular tilt and the crystallinity normal to the surface, but improves the film morphology significantly, yielding larger grains with perhaps better in-plane crystallinity.

Deoxygenation of the IrO 2 (1 1 0) surface is investigated at 403–493 K, using the core-level spectroscopy and density functional theory (DFT) calculation. The Ir-4f 7/2 signals of 1f-cus-Ir with and without on-top oxygen (O top ) emerge as surface features of the baked-out surface, whose positive and negative shifts in binding energy are in line with the DFT computation results. Progressively increasing the reduction temperature, the 1f-cus-Ir feature quickly disappears and the signal of 2f-cus-Ir emerges at 403 K. Meanwhile the feature of 1f-cus-Ir + O top diminishes but persists when the Ir metal signal is evident. The intriguing coexistence of 1f-cus-Ir + O top and Ir metal at 433–443 K is elucidated in the theoretical pathway study. DFT calculation reveals that O 2 desorption via pairing two neighboring O top atoms is the rate-determining step of surface deoxygenation. Under the UHV conditions, O top is replenished via migration of the surface oxygen species, including the threefold coordinated oxygen (O 3f ) of a reduced surface. Hence the O top atom is an active and long-lived surface species, which does not vanish until O 3f is consumed and surface Ir begins to cluster. Under the realistic pressure conditions, O top can also be refreshed via the dissociative adsorption of gas-phase oxygen. In either pathway, O top is a critical intermediary of IrO 2 (1 1 0) oxidation catalysis.

The interaction of freshly abraded surfaces of cuprite, Cu 2 O, with neutral or mildly alkaline aqueous solutions of diethyl or di- n -butyl dithiophosphate (DTP) has been investigated by means of conventional and synchrotron X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. It was confirmed that DTP adsorbs readily on Cu atoms in the surface layer of the mineral treated with solutions of the collector at pH values near 7 and 9 in the presence of air, and renders the surface hydrophobic. When cuprite is treated with relatively high concentrations of DTP for sufficiently long periods, collector can also be adsorbed as CuDTP, but the coverage does not exceed a thin layer of CuDTP on the adsorbed DTP monolayer, unlike the situation with Cu metal or chalcocite where a thick multilayer can be formed.

The adsorption and co-adsorption of two flotation collectors (sodium 2-mercaptobenzothiazole (MBT) andpotassium di-isoamyl dithiophosphate (DTP) on gold and gold:silver alloy surfaces has been studied using synchrotron X-ray photoelectron spectroscopy. The use of synchrotron radiation (NSRRC, Taiwan) and anewly designed/built soft X-ray endstation (commissioned in Taiwan and now installed at the AustralianSynchrotron) has enabled the collection of high signal-to-noise, high resolution spectra of the sulfur 2p peakfor the adsorbed collectors. Both collectors were observed to adsorb on gold and gold:silver surfaces. MultipleS 2p doublets were observed in the photoemission spectra, in spite of the fact that the solution conditionsand exposure times ensured (sub)monolayer (rather than multilayer) adsorption. MBT is seen to have twochemisorbed geometries when adsorbed on gold and only one when adsorbed on gold:silver substrates. Thespectra also indicate that DTP may have two chemisorbed geometries (bidentate and monodentate), on bothgold and gold:silver substrates. In addition, both surfaces were shown to co-adsorb the collectors, with somevariation in the relative adsorbed amounts: MBT adsorbs more extensively than DTP from the solutionmixture onto gold; the reverse is true for the gold:silver substrate. Refereed/Peer-reviewed

In situ scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) were used to examine the electrified interface of Au(111) in 0.1 M H2SO4 containing 0.030 M aniline. In agreement with cyclic voltammogram (CV), which revealed two pairs of peaks at 0.48 and 0.62 V, in situ STM imaging yielded two highly ordered aniline adlattices, (√19 × 5) at 0.55 V and (3 × 2√3)rect at 0.85 V [vs reversible hydrogen electrode, RHE]. According to XPS results obtained with Au(111) emersed at 0.85 V from 0.1 M H2SO4 + 0.030 M aniline, bisulfate anions were coadsorbed in an amount equal to that of aniline. The (3 × 2√3)rect−aniline structure was examined carefully by STM using different imaging conditions. Results revealed that imaging with a tunneling current of 10 nA at a −300 mV bias voltage allowed molecular resolution of both aniline admolecules and bisulfate anions. These species could form acid−base pairs and mingled uniformly on the Au(111) ele...

X-ray photoelectron spectroscopy and temperature-programmed reaction/desorption have been employed to study the thermal dissociation of HSCH 2 CH 2 OH on the Cu(1 1 1) surface. An exposure of 1.5 Langmuir (L) HSCH 2 CH 2 OH renders a chemisorption monolayer at 100 K. For the exposures (1.6, 3.0 and 8.0 L) investigated, it is found that two surface intermediates of –SCH 2 CH 2 OH and –SCH 2 CH 2 O– are generated from successive dehydrogenation of HSCH 2 CH 2 OH on Cu(1 1 1) before it totally decomposes into gaseous products with (or without) carbon left on the surface at a temperature higher than ∼350 K. XPS study of 1.6 L exposure shows that both the C1s peak intensities of –SCH 2 CH 2 OH generated at ∼225 K are comparable. However, for the same intermediate prepared using 8.0 L, the C1s peak intensity of the SCH 2 moiety is only 0.58 of that of the CH 2 OH. Between ∼230–350 K, –SCH 2 CH 2 OH and –SCH 2 CH 2 O– coexist on the surface, but the reactivity for –SCH 2 CH 2 OH dehydrogenation to form –SCH 2 CH 2 O– decreases in the order of 1.6, 3.0 and 8.0 L. The surface –SCH 2 CH 2 OH and –SCH 2 CH 2 O– diminish in the temperature range 350–450 K and generate reaction products of H 2 , H 2 O, CH 4 , C 2 H 4 and CH 3 CHO. However, the evolution temperatures of these products formed at 8.0 L are higher than those formed at 1.6 L by ∼20–30 K. The observed exposure-dependent C1s peak intensities, –SCH 2 CH 2 OH dehydrogenation reactivity, and product desorption temperatures are suggested to be due to the change of –SCH 2 CH 2 OH geometry ( trans or gauche) and/or orientation (tilting angle relative to the surface) with HSCH 2 CH 2 OH exposure.

Hydrothermal treatment has been applied successfully to convert amorphous titania films to crystalline anatase at 120 °C, a temperature compatible with most polymeric substrates. The amorphous films were deposited at 80 °C using atomic layer deposition (ALD). The crystallinity of the films was monitored by x-ray absorption near edge structure (XANES), and the film composition was determined by x-ray photoelectron spectroscopy (XPS). The effect of precursor chemistry and substrate material was investigated. It was found that titania films produced from Ti isopropoxide are easier to crystallize than those from Ti tetrachloride as the Ti precursor. The amorphous to crystalline transformation can be achieved more readily with films deposited on Si than polycarbonate substrates. The effect of a “seed” layer on the amorphous to crystalline transformation was also studied. Preformed anatase crystallites between the Si substrate and the amorphous film were shown to accelerate the crystallization process. The possible mechanisms responsible for the phase transformation are discussed.

A number of freshly abraded surfaces of pentlandite have been characterised by X-ray photoelectron spectroscopy to establish whether the initial intensity of the S 2p component near 161.4 eV, previously assigned to the 25% of S atoms in fourfold coordination by metal atoms in pentlandite, was always at least 25% of the total S 2p intensity. It was found that the intensity of this S 2p component could be lower than 20% for surfaces that were not significantly oxidised. To assess whether the proposed 0.75–0.8 eV 2p binding energy difference for the two sulfur environments in pentlandite was justified, ab initio calculations of the difference in core electron binding energies and of the densities of unfilled states have been carried out. The corresponding simulated S K near-edge X-ray absorption fine structure (NEXAFS) spectra have been compared with experimental spectra. The calculated S 2p and S 1s binding energy differences were 0.45 and 0.5 eV at most, in agreement with the experimental NEXAFS spectra. It was concluded that the S 2p component near 161.4 eV arises entirely from violarite present at the pentlandite surface rather than from 4-coordinate S in pentlandite itself. Ab initio calculations of the difference in S 2p binding energies for the 2- and 3-coordinate S in stibnite have also been carried out and found to be quite small, in agreement with previously reported experimental values. Nevertheless, for both pentlandite and stibnite, calculations have confirmed that an increase in coordination number is associated with an increase in sulfur core electron binding energies, even although that increase is barely measurable for the latter sulfide.

Examples are presented of the complementary nature of conventional XPS, synchrotron XPS, ToF-SIMS and NEXAFS spectroscopy when applied to the adsorption of MBT on metals and metal sulfides. Conventional XPS could detect chemisorption via S 2p spectra, detect the onset of multilayer formation via the relevant metal Auger or core level photoelectron spectra, and determine metal thiolate stoichiometry from thick multilayers. Surface-optimised synchrotron XPS allowed precise chemisorbed MBT S 2p binding energies to be obtained. Angle-dependent N and C NEXAFS spectra revealed adsorbate orientation, even for an abraded but relatively smooth surface. Cu L3-edge spectra detected some Cu(II) and hence Cu(MBT)2 in multilayers on chalcocite. Static SIMS data confirmed the interaction of both N and exocyclic S with surface metal atoms for silver metal and chalcocite.

X-ray photoelectron spectra have been obtained under the same experimental conditions for synthetic α-NiS and natural β-NiS in order to establish any difference in S electronic environment, and to test the proposition that S core electron binding energies increase measurably with coordination number when the same metal is in different sulfide structures or lattice sites. The Ni and S electronic environments in the two NiS structures have been further probed by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and the NEXAFS spectra interpreted by reference to spectra simulated by ab initio calculations. The photoelectron and NEXAFS spectra for freshly prepared surfaces of α-NiS and β-NiS were found to be similar, with only subtle differences in electronic environment evident in the experimental and simulated NEXAFS spectra. The measured and calculated core electron binding energies did not support the previously postulated relationship between S coordination number and electron binding energies.

Temperature-programmed reaction/desorption, X-ray photoelectron spectroscopy, and reflection–absorption infrared spectroscopy have been employed to investigate the reactions of ICH2CH2OH on Cu(1 0 0) under ultrahigh-vacuum conditions. ICH2CH2OH can dissociate on Cu(1 0 0) at 100 K, forming a –CH2CH2OH surface intermediate. Density functional theory calculations predict that the –CH2CH2OH is most probably adsorbed on atop site. –CH2CH2OH on Cu(1 0 0) further decomposes to yield C2H4 below 270 K. No evidence shows the formation of –CH2CH2O– intermediate in the reactions of ICH2CH2OH on Cu(1 0 0) in contrast to the decomposition of BrCH2CH2OH on Cu(1 0 0) and ICH2CH2OH on Ag(1 1 1) and Ag(1 1 0), exhibiting the effects of carbon–halogen bonds and metal surfaces.

The growth of PbI2 precipitates on single crystal substrates from colloidal solutions has been investigated with in air scanning tunneling microscopy and synchrotron-based X-ray photoelectron spectroscopy. The PbI2 growth on Rh(1 0 0) results in nano-clusters with lateral dimensions between 30 and 60 A, consistent with earlier reports. However, the growth of PbI2 on a well-ordered iodinated Rh(1 0 0), denoted as (√2×√2)R45°-I, leads to atomically smooth PbI2 films having a hexagonal symmetry with lattice constant identical to the bulk value of 4.5 A. The heteroepitaxy is believed to be effected by the atomic iodine monolayer that helps to accommodate large lattice mismatch between PbI2 and Rh surface with short-range van der Waals interaction.

The chemisorption of 1-decanethiol on the Au(111) single crystal has been studied with synchrotron-based, high-resolution photoemission spectroscopy with molecular film prepared from both gas-phase dosing and solution immersion to vary surface coverage over a wider range. The structure of the molecular film, determined separately via low-energy electron diffraction, includes a c(23 × √3) stripe phase and c(3 × 2√3) saturated phases. Careful curve fitting of the S 2p2/3 core level reveals that there is only one sulfur species at a binding energy of 162.1 eV in the film and the spectrum of the S 2p core level does not vary with the surface coverage and existence temperature of the decanethiolate. This finding is inconsistent with the sulfur-pairing model proposed based on X-ray scattering and standing wave studies. Up to two C 1s core levels at 284.0 and 285.0 eV can be observed, depending on the surface coverage. Angle-resolved X-ray photoelectron spectroscopy measurements are utilized to provide a direct ...

The electroreduction of nitrobenzene has been studied on Au single crystals of (111), (110), (100), and (210) orientations and on Au polycrystals in dilute aqueous perchlorate solution using cyclic voltammetry. The voltammograms were found to be dependent sensitively on the surface orientation. Notably, the reduction on (110), (210), and (poly) electrodes can lead to a stably adsorbed redox intermediate, not reported before, at about 0.33 V versus SCE and the intermediate is deduced as the phenyldihydroxylamine/phenyldihydroxylamine cation redox couple. The unusual stability of the redox intermediate is found to correlate with the orientation of adsorbed water molecules that can be controlled intimately by the applied potential in relationship to the potential of zero charge on the surfaces.

The chemistry of 2-iodoacetic acid on Cu(100) has been studied by a combination of reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reaction/desorption (TPR/D), and theoretical calculations based on density functional theory for the optimized intermediate structures. In the thermal decomposition of ICH(2)COOH on Cu(100) with a coverage less than a half monolayer, three surface intermediates, CH(2)COO, CH(3)COO, and CCOH, are generated and characterized spectroscopically. Based on their different thermal stabilities, the reaction pathways of ICH(2)COOH on Cu(100) at temperatures higher than 230 K are established to be ICH(2)COOH --CH(2)COO + H + I, CH(2)COO + H --CH(3)COO, and CH(3)COO --CCOH. Theoretical calculations suggest that the surface CH(2)COO has the skeletal plane, with delocalized pi electrons, approximately parallel to the surface. The calculated Mulliken charges agree with the detected binding energies for the two carbon atoms in CH(2)COO on Cu(100). The CCOH derived from CH(3)COO decomposition has a CC stretching frequency at 2025 cm(-1), reflecting its triple-bond character which is consistent with the calculated CCOH structure on Cu(100). Theoretically, CCOH at the bridge and hollow sites has a similar stability and is adsorbed with the molecular axis approximately perpendicular to the surface. The TPR/D study has shown the evolution of the products of H(2), CH(4), H(2)O, CO, CO(2), CH(2)CO, and CH(3)COOH from CH(3)COO decomposition between 500 and 600 K and the formation of H(2) and CO from CCOH between 600 and 700 K. However, at a coverage near one monolayer, the major species formed at 230 and 320 K are proposed to be ICH(2)COO and CH(3)COO. CH(3)COO becomes the only species present on the surface at 400 K. That is, there are two reaction pathways of ICH(2)COOH --ICH(2)COO + H and ICH(2)COO + H --CH(3)COO + I (possibly via CH(2)COO), which are different from those observed at lower coverages. Because the C-I bond dissociation of iodoethane on copper single crystal surfaces occurs at approximately 120 K and that the deprotonation of CH(3)COOH on Cu(100) occurs at approximately 220 K, the preferential COOH dehydrogenation of monolayer ICH(2)COOH is an interesting result, possibly due to electronic and/or steric effects.

A straightforward application of an electron energy analyzer equipped with an image detector to micron‐resolved electron spectroscopic studies of organic thin film devices is reported. The electron spectroscopies implemented include synchrotron‐based UPS, XPS, and Auger yield NEXAFS. Along the non‐energy‐dispersion direction of the analyzer, a spatial resolution of ∼40 μm is obtained through the employment of entrance slits, electrostatic lenses and segmented CCD detector. One significant benefit offered by the technique is that the electronic transport and electronic structure of the same micron‐sized sample can be directly examined. The example illustrated is a top‐contact organic field effect transistor (OFET) fabricated from semiconducting triethylsilylethynyl anthradithiophene and gold electrodes. It is found that an extensive out‐diffusion of gold atoms to adjacent conduction channels takes place, presumably due to the inability of soft organic materials in dissipating the excess energy with which gaseous Au atoms possess.

Decoration of nitrogen vacancies by oxygen atoms has been studied by near-edge x-ray absorption fine structure (NEXAFS) around B K-edge in several boron nitride (BN) structures, including bamboo-like and multi-walled BN nano-tubes. Breaking of B-N bonds and formation of nitrogen vacancies under low-energy ion bombardment reduces oxidation resistance of BN structures and promotes an efficient oxygen- healing mechanism, in full agreement with some recent theoretical predictions. The forma-tion of mixed O-B-N and B- O bonds is clearly identified by well resolved peaks in NEXAFS spectra of excited boron atoms.

X-ray photoelectron and absorption spectra have been obtained for natural specimens of cubanite and compared with the corresponding spectra for chalcopyrite. Synchrotron X-ray photoelectron spectra of surfaces prepared by fracture under ultra-high vacuum revealed some clear differences for the two minerals, most notably those reflecting their different structures. In particular, the concentration of the low binding energy S species formed at cubanite fracture surfaces was approximately double that produced at chalcopyrite surfaces. However, the core electron binding energies for the two S environments in cubanite were not significantly different, and were similar to the corresponding values for the single environment in chalcopyrite. High binding energy features in the S 2p and Cu 2p spectra were not related to surface species produced either by the fracture or by oxidation, and most probably arose from energy loss due to inter-band excitation. Differences relating to the Fe electronic environments were detectable, but were smaller than expected from some of the observed physical properties and Mossbauer spectroscopic parameters for the two minerals. X-ray absorption and photoelectron spectra together with the calculated densities of states for cubanite confirmed an oxidation state of CuI in the mineral. It was concluded that the best formal oxidation state representation for cubanite is CuI(Fe2)VS 3 −II .

Fracture surfaces of a natural carrollite specimen have been characterised by synchrotron and conventional X-ray photo-electron spectroscopy and near-edge X-ray absorption spectroscopy. For the synchrotron X-ray measurements, the mineralsurfaces were prepared under clean ultra high vacuum and were unoxidised. The characterisation was undertaken primarily toestablish unequivocally the oxidation state of the Cu in the mineral, but also to obtain information on the electronic environ-ments of the Co and S, and on the surface species. Experimental and simulated Cu L2,3-edge absorption spectra confirmed anoxidation state of CuI, while Co 2pphotoelectron and Co L2,3absorption spectra were largely consistent with the CoIIIestab-lished previously by nuclear magnetic resonance spectroscopy. S 2pphotoelectron spectra provided no evidence for S to bepresent in the bulk in more than one state, and were consistent with an oxidation state slightly less negative than S–II. There-fore it was concluded that carrollite can be best represented by CuICoIII2(S4)–VII. The CuIoxidation state is in agreement withthat expected for Cu tetrahedrally coordinated by S, but is in disagreement with the CuIIdeduced previously from some mag-netic, magnetic resonance and Cu L-edge X-ray absorption spectroscopic measurements. A significant concentration of S spe-cies with core electron binding energies both lower and higher than the bulk value were formed at fracture surfaces, and theseentities were assigned to monomeric and oligomeric surface S species. The density of Cudstates calculated for carrollite dif-fered from that previously reported but was consistent with the observed Cu L3X-ray absorption spectrum. The initial oxi-dation of carrollite in air under ambient conditions was confirmed to be congruent, unlike the incongruent reaction undergoneby a number of non-thiospinel sulfide minerals. Refereed/Peer-reviewed

We have achieved a growth of highly oriented crystalline pentacene thin films, with preferred a-b in-plane orientation with respect to the rubbing direction of a rubbed polymethylene surface. The polymethylene thin film, generated on a gold surface by gold-catalyzed decomposition of diazomethane, was annealed and gently rubbed in a fixed direction by a flannelette cloth to serve as an alignment layer during the deposition of pentacene molecules. Various surface analysis techniques, including reflection absorption IR spectroscopy (RAIRS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, grazing incidence X-ray diffraction (GIXD), and atomic force microscopy were used to elucidate the structural details of the polymethylene and the pentacene thin films deposited on it. Two crystalline morphologies of pentacene thin film were observed: the minor one of rod-like molecular crystals having their long axes of the crystals perpendicular to the rubbing direction, and the dominant one of platelet-like and layered crystals having the molecular axes stand near vertical to the surface. Moreover, GIXD revealed that the rubbing on polymethylene indeed induced a preferential azimuthal alignment of pentacene crystallites. The deposition of pentacene at 25 degrees C led to a twin growth of crystallites with the [110] direction predominately aligned perpendicular to the rubbing direction. In contrast, the pentacene deposition at 50 degrees C produced twinned crystallites of lower twin angle and the [120] direction aligned parallel to the rubbing direction.

The difficulty of performing a reliable carbon NEXAFS measurement for thin films and adsorbate systems has long been recognized. The difficulty is typically related to lower S/B, carbon buildup in beamline optics, dirty mesh, presence of the high‐order x‐rays, etc. To alleviate the experimental difficulty, we have constructed an intensity‐monitoring ion chamber situated between the beamline and sample chamber. The ion chamber is filled with argon up to a working pressure of 10−3 Torr and terminated with 0.1 μm thick Ti foils at both ends. Titanium foils and the filled argon gas effectively remove the high‐order x‐rays. Consequently, the data are acquired with predominant 1st‐order x‐rays and thus free of the aforementioned interference, leading to a more reliable data analysis.

Synchrotron XPS and Cu L2,3-edge NEXAFS spectroscopic data for a natural tetrahedrite surface prepared by fracture under UHV were in accord with the composition of the mineral and its expected semiconductivity. The 2p binding energy for the 6-coordinate S atoms was found to be not detectably greater than that for the 4-coordinate S atoms, and surface species were not clearly discernible in either surface-optimized S 2p or Cu 2p spectra. The Cu 2p and Cu L2,3-edge spectra indicated that all Cu in the mineral was indisputably Cu(I). The Cu L2,3-edge spectra of relatively pure natural sphalerite treated with mildly acidic aqueous cupric solution revealed the presence of Cu(II) in the outermost layer of the fracture surfaces, but it was concluded that most of the Cu near the surface of the mineral was in formal oxidation state Cu(I), albeit with higher than normal d9character. The Cu(I) absorption peak was at an energy much lower than for the tetrahedrite absorption edge, but still consistent with Cu(I) in 4-fold coordination by S. The Cu(II) was consistent with Cu bonded both to S atoms in the outermost layer of the sphalerite and to O atoms in chemisorbed water. S 2p spectra determined at different photon energies revealed high binding energy components arising from oligosulfide-like environments in the outermost layers, but not necessarily in a completely restructured lattice and not in a Cu oligosulfide only. The data indicated some loss of Zn in addition to the Zn that had been replaced by Cu in the outermost layers of the sulfide lattice. The presence of these oligosulfide-like environments precluded the detection of S with formal oxidation state greater than (-II) that might have arisen only from Cu(I) in the S lattice. No evidence was obtained for the presence of Cu(II) in a sulfide lattice, but it was not possible to exclude the possibility of a very low concentration because of the presence of the Cu(II) bonded to both S and O at the surface of the treated sphalerite.Key words: tetrahedrite, sphalerite, copper uptake, XPS, NEXAFS.

We have studied the growth of S layers adsorbed on Au(100) with low-energy electron diffraction (LEED), X-ray photoemission spectra (XPS), and scanning tunneling microscope (STM). Three phases of S/Au(100)-(2 × 2), trimer, and c(2 × 4)-are identified; the latter two are not previously reported. A dose of S2 at 300 K transformed Au(100)-(5 × 20) initially into the (2 × 2) phase and formed the c(2 × 4) phase at a saturation coverage. The STM results show that monolayer Au islands formed during the initial S dose and remained throughout the growth, resulting in a rough c(2 × 4) surface. We show that a highly ordered c(2 × 4) phase can be obtained with a flat (2 × 2) phase as an intermediate step during growth. Based on the evolution of XPS and STM images with varied S2 dose, the components of S 2p are assigned and structural models for the various S/Au(100) phases are proposed. In the (2 × 2) phase, one S atom resides on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.25 ML; in the trimer phase, three S atoms form a trimer residing on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.75 ML; in the c(2 × 4) phase, there are five S atoms in each primitive unit cell of c(2 × 4); three of them form a trimer residing on a four-fold hollow site, and the other two form a dimer located on the top of the trimer, corresponding to a nominal S coverage of 1.25 ML. With the proposed structural models, the growth of S on Au(100) at 300 K is described in detail.

The efficiency of conventional point-to-point scan is limited by overheads from mechanical system and data acquisition system. With network-friendly development interface provided by commercial software and hardware, the DAQ system, the position encoding system, the undulator, and the monochromator system can be easily controlled by synchronizing various instruments for on-the-fly scanning operation. In this work, an on-the-fly scanning method is developed for absorption spectrum measurement under the Labview's programing environment. We have tested its performance on Dragon type beamlines at NSRRC. For a given energy resolution and a S/N level our preliminary results show that the time required to obtain a spectrum of Near Edge X-ray Absorption Fine Structure (NEXAFS) and X-ray Absorption Spectroscopy (XAS) using the on-the-fly scanning system is about 10 times and 20 times shorter than those using the point-to-point scanning with bending magnet and undulator sources, respectively. The higher efficiency gained from the on-the-fly scanning system results from minimizing system communication time and mechanical system overheads. The new improved technique should significantly contribute to the study and measurement of photon dose sensitive samples.

Here, we have combined the understanding of density functional theory in relation with lattice strain-to-activity correlation to design a Rucore–Ptshell structured electrocatalyst in a dye-sensitized solar cell (DSC) cathode. This electrocatalyst possesses a compressive lattice strain in the shell region which translocates the Pt valence charge to neighboring atoms to decrease the Pt valence band density of states and thus lower the Pt d-band levels. Consequently, compared with DSCs using Pt nanoparticles (NPs) cathode, the Rucore–Ptshell NPs improves the triiodide to iodide redox reduction activity by 2.11-fold and thus boosts the photovoltaic efficiency of DSCs by ∼30.4%. These results provide mechanistic information for the development of DSCs with reduced Pt utilization and programmable electrochemical performance.

Fluorine-substituted ethyl groups on Cu(111) were generated by thermal scission of the C-I bond in the adsorbed C2F5I. Temperature-programmed reaction spectrometry observed a novel pathway resulting in the evolution of C4F6 above 400 K. Among the various isomers, this product was identified as hexafluro-2-butyne. Although abstraction of two fluorine atoms from the starting Cu-CF2CF3 was required, Cu-CCF3 (trifluoroethylidyne) was favored over Cu-CF=CF2 (trifluorovinyl) as the intermediate because this ethyl-ethylidyne-butyne pathway was suppressed on a Cu(100) surface devoid of the key threefold hollow binding sites for ethylidyne. Once formed, perfluoroethylidyne readily coupled to afford a tightly surface-bound hexafluoro-2-butyne up to 400 K. Therefore, the C-F bonds adjacent to the metal were found to be more susceptible to the bond activation, leading the chemisorbed perfluoroethyl to eliminate two F atoms successively from the alpha-carbon. This preference for alpha-elimination rather than beta-elimination (the most favorable route in hydrocarbons) may be quite general for metal surface-mediated reactions involving fluorinated alkyl groups.

The effect on abraded surfaces of chalcocite, covellite and chalcopyrite of their immersion in ethanol, propan-2-ol or acetone has been determined by synchrotron X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. It was confirmed that the extent of surface oxidation while immersed in these organic solvents can be greater than that from air exposure alone, possibly because of carboxylic acid formation at the solid/liquid interface. In all cases investigated, the surface layer was chemically altered following the immersion, even when primary oxidation products were removed by dissolution in the organic liquid. It is clear that the use of alcohols or ketones should be avoided in the preparation of sulfide surfaces for ex situ chemical characterisation in minerals processing research.

Enhanced and anisotropic field-effect mobility of thin-film transistors based on pentacene was obtained on a substrate covered with a prerubbed, self-assembled monolayer (SAM) of n-alkyltrichlorosilane. The field-effect mobility along the rubbing direction increased by a factor of ∼15 on rubbed n-nonyltrichlorosilane-modified surface, whereas on n-octadecyltrichlorosilane-modified surface, an increase by a factor of 2–4 was observed. The structures of pentacene films deposited on the SAM/rubbed SAM were characterized by powder x-ray diffraction, atomic force microscopy, and carbon K-edge near edge x-ray fine structure spectroscopy. An in-plane alignment effect on the pentacene packing and film morphology is proposed.

Surfaces of mineral cuprite prepared by fracture under UHV have been characterised by synchrotron XPS and near-edge X-ray absorption spectroscopy before and after exposure to ambient air. Before exposure of the cuprite, the Cu 2 p photoelectron and Cu L 2,3 -edge absorption spectra were consistent with Cu I with very little d 9 character. Surface-enhanced O 1 s spectra from the unexposed mineral revealed a surface species, with binding energy 0.95 ± 0.05 eV below the principal cuprous oxide peak, assigned to under-coordinated oxygen. A second surface species, with binding energy about 1 eV higher than the principal peak, was assigned to either hydroxyl derived from chemisorbed water vapour or surface oxygen dimers produced by restructuring of the cuprite fracture surface. The width of the principal O 1 s peak was 0.66 ± 0.02 eV. The observed Cu L 3 - and O K-edge absorption spectra were in good agreement with those simulated for the cuprite structure. After exposure of the fracture surface to ambient air, the low binding energy O 1 s surface species was barely discernible, the original high binding energy O 1 s surface species remained of comparable intensity, new intensity appeared at an even higher (∼1.9 eV) binding energy, and the Cu L 2,3 -edge spectrum indicated the presence of Cu II , consistent with the formation of a thin surface layer of Cu(OH) 2 .