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The paper presents a study of a large-area field emitter based on a composite of vertically aligned carbon nanotubes covered with a continuous and conformal layer of nickel oxide by the atomic layer deposition method. The arrays of carbon nanotubes were grown by direct current plasma-enhanced chemical vapor deposition on a pure Si substrate using a nickel oxide catalyst which was also deposited by atomic layer deposition. The emission characteristics of an array of pure vertically oriented carbon nanotubes with a structure identical in morphology, covered with a layer of thin nickel oxide, are compared using the data from a unique computerized field emission projector. The deposition of an oxide coating favorably affected the emission current fluctuations, reducing them from 40% to 15% for a pristine carbon nanotube and carbon nanotube/nickel oxide, respectively. However, the 7.5 nm nickel oxide layer coating leads to an increase in the turn-on field from 6.2 to 9.7 V/µm. [ABSTRACT FROM AUTHOR]

The object of our current investigation is Cu-As2Se3 thin film structures. The impact of corona discharge on photoinduced modifications of the transmission spectra of both asdeposited and exposured with actinic light of the Cu-As2Se3 structures have been studied. Two cases have been investigated. First normal irradiation of the film structures without charging, and another one, when exposure was switched on, 7 kV corona charge at different polarity was applied. As a result, in the region of the weak absorption in the transmission spectra the photobleaching effect was observed and in the region of the strong absorption the photodarkening phenomena was manifested. In the region o weak absorption higher values of photobleaching was observed during exposure in the field of positive corona discharge. The obtained results are qualitatively analyzed taking into account the photodarkening of the semiconductor during it doping with Cu ions as well as transmission increases of the structure during photodiffusion of the cupper in the amorphous semiconductor. [ABSTRACT FROM AUTHOR]

Efficient perovskite solar cells can be produced by a wide variety of different methods. Previous results show that controlling the film morphology is critical to enhance the efficiency of the prepared devices. Here, grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to study the morphology and especially the orientation distribution of CH3NH3PbI3 (MAPI) perovskite films prepared by five typical methods. We find that the investigated one-step methods produce non-oriented films, while the two-step deposition methods produce varying degrees of orientation depending on the method chosen to convert the highly oriented PbI2 precursor, providing direct evidence for different perovskite conversion mechanisms. In particular, we show that the morphology and crystal orientation of MAPI films is tunable by varying the spin-coating temperature and by adding chloride to the conversion solution. By relating the precursor morphology to the resulting MAPI film morphology, we link the observed preferential orientations to specific conversion mechanisms, thereby establishing GIWAXS as an important tool toward a rational development of new synthesis methods. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption behavior of iron phthalocyanine (FePc) on the Cu(100) surface at the initial stage has been investigated by combining scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At low coverage, FePc molecules deposited on the sample surface at room temperature tend to adsorb dispersedly with their molecular planes parallel to the crystallographic directions of the substrate. Another interesting STM observation for the sub-monolayer coverage is that the molecular axes of FePc are aligned along [037] (as well as ) azimuth. At the monolayer coverage and elevated temperature, two types of ordered structures are observed. The FePc adsorption sites for the experimentally observed two distinct ordered domains have been revealed through DFT calculations. With further increasing the coverage, molecular clusters are formed particularly near the step edges. [Copyright &y& Elsevier]

Abstract: The structure and morphology of pentacene films grown on a Cu(221) vicinal surface have been studied by means of scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and atomic force microscopy (AFM). Well ordered saturated monolayer films were prepared by first depositing few nanometers pentacene at room temperature followed by brief heating above 400K in order to sublimate the multilayer excess. The chemisorbed monolayer adopts a (1×7) superstructure with a uniform alignment of the molecules along the step edges while upon further deposition this template induced ordering is not transferred to multilayer films. Instead the molecules continue to grow in an upright orientation and form pyramidal islands without any substrate related azimuthal orientation. [Copyright &y& Elsevier]

Abstract: Continuous crystalline MnSi ultrathin films with atomically flat surfaces, which are highly expected to find an application in Si-based spintronics, are grown on Si(111)- by solid phase epitaxy method. The interfacial reaction between Mn and Si and the formation processes of the films as well as their morphological variation with annealing temperature are investigated using scanning tunneling microscopy. The MnSi ultrathin films form in a two-dimensional (2D) fractal-like mode only at a Mn coverage above ∼2 ML and at an annealing temperature in the narrow range of ∼250–300 °C. Above ∼300 °C, the growth mode gradually transforms into Volmer–Weber mode and correspondingly, the continuous films transform into 2D compact islands. The films grow with a thickness unit of quadruple layer, which is consistent with the B20-type MnSi structure. [ABSTRACT FROM AUTHOR]

Abstract: ZrO2 and Er2O3 thin films and nanolaminates were grown by atomic layer deposition from tris(2,2,6,6-tetramethyl-3,5-heptanedionato)erbium, bis(methylcyclopentadienyl)methoxymethylzirconium and ozone as precursors at 350°C. Nanolaminates consisted of 3–8nm thick ZrO2 and Er2O3 layers alternately deposited on planar substrates and on three-dimensional substrates with aspect ratio 1:20. The erbium content was 5–15at.%. ZrO2–Er2O3 films crystallized already in as-deposited states. Upon annealing at 650°C, the films were stabilized in the form of cubic or tetragonal ZrO2 polymorph and cubic Er2O3. Dielectric properties of the nanolaminates were comparable to those of the constituent oxides. [Copyright &y& Elsevier]

Abstract: We have investigated the incident polarization dependence of the Co soft X-ray emission spectra for the single- and double-atomic height Co islands grown on the nitrogen-adsorbed Cu(001) surface. For non-resonant incident X-ray in the depolarized configuration, a shoulder structure appeared at the high-energy side of the main peak of the spectra while there is no shoulder in the polarized configuration. The shoulder is attributed to the excitation of correlation satellite originated from the periphery Co atoms of the Co nano-islands. The resonant X-ray emission spectrum in the polarized configuration with the excitation energy of the absorption peak shows a peak located at the high-energy side of the main peak. This additional peak was not observed in the depolarized configuration. [ABSTRACT FROM AUTHOR]

Abstract: We report on angle-resolved photoelectron spectroscopy results of thin dysprosium-silicide layers formed on Si(111), taken with a toroidal analyzer allowing to image the energy surfaces in k|| -space. At monolayer dysprosium coverages, where hexagonal DySi2 grows with a superstructure, electron pockets are observed at the points with highly anisotropic effective masses, and around a hole pocket at the point also an anisotropic dispersion is found. The band filling of these two bands amounts to one, indicating an even number of electrons assigned to the surface unit cell. Similar features are found for multilayer coverages, where hexagonal Dy3Si5 layers are formed with a superstructure. Here, the influence of zone folding effects due to the reconstructed layers in the bulk silicide is only weak because of the high surface sensitivity of the experiments. [Copyright &y& Elsevier]

Abstract: Density functional theory (DFT) with LDA and GGA have been employed to study the interface and thin film properties of NaCl on a Ge(001) surface. The atomic and electronic structures of thin NaCl films from one to ten monolayers were analyzed. The layer adsorption energies show that a quasi-crystalline (001) fcc NaCl film is built up via a layer-by-layer growth mode with NaCl thickness above 2ML. Simulated STM images show a well-resolved (1×1) NaCl atomic structure for sample bias voltage V s <−2.5V and the bright protrusions should be assigned to the Cl− ions of the NaCl film. The Ge substrate dimer is reserved and buckled like a clean Ge(001)-p(2×2) surface as the result of weak interface interaction between the dangling bonds coming from valence π states of the Ge substrate and the 3p states of the interfacial Cl− ion. These results are consistent with the experiments of STM, LEED and EELS. [Copyright &y& Elsevier]

Abstract: Ordering of submonolayer iron phthalocyanine (FePc) molecules deposited on Ag(111) was investigated using scanning tunneling microscopy. The room temperature deposition of FePc alone, without any annealing, results in no ordered overlayers. However, posterior annealing the substrate to 475K leads to the formation of a two-dimensional oblique lattice with the lattice constants of 16.2±0.3Å and the angle of 78±1° between them. The resulting FePc lattice is commensurate to the substrate lattice. In addition, the nearest neighbor distance in the lattice is significantly increased through a distinctive molecular orientation of the FePc molecules within the unit cell. The commensurate lattice with a large intermolecular distance is in sharp contrast to that observed from a close-packed square lattice that many other metallo-phthalocyanine molecules often self-assemble into. A possible reasoning behind this intriguing structure is discussed. [Copyright &y& Elsevier]

Abstract: This study investigates ultra-thin potassium chloride (KCl) films on the Si(100)-2×1 surfaces at near room temperature. The atomic structure and growth mode of this ionic solid film on the covalent bonded semiconductor surface is examined by synchrotron radiation core level photoemission, scanning tunneling microscopy and ab initio calculations. The Si 2p, K 3p and Cl 2p core level spectra together indicate that adsorbed KCl molecules at submonolayer coverage partially dissociate and that KCl overlayers above one monolayer (ML) have similar features in the valance band density of states as those of the bulk KCl crystal. STM results reveal a novel c(4×4) structure at 1ML coverage. Ab initio calculations show that a model that comprises a periodic pyramidal geometry is consistent with experimental results. [Copyright &y& Elsevier]

Abstract: The solid-phase epitaxial growth process and surface structure of MnSi on Si(111) were investigated by coaxial impact-collision ion scattering spectroscopy (CAICISS) and atomic force microscopy (AFM). For the Si(111) sample deposited with 30 monolayers (ML) of Mn at room temperature, the intermixing of Mn and Si gradually started at 100°C and reached equilibrium at approximately 400°C. At this equilibrium state, the Mn atoms were transformed into crystalline MnSi film. Further annealing caused the desorption of Mn atoms. We identified the structure of MnSi as cubic B20 and the crystallographic orientation relationships as Si(111)//MnSi(111) and Si[]//MnSi[]. The MnSi(111) surface was found to have a dense Si terminating layer on its topmost surface. On the other hand, 3ML of Mn deposited on Si(111) reacted with Si even at room temperature and formed a pseudomorphic structure. This structure was transformed into MnSi after annealing. A filmlike morphology with protrusions was observed for the sample with 30ML of Mn, while island growth occurred for the sample with 3ML of Mn. [Copyright &y& Elsevier]

Abstract: We have investigated seven samples of radio frequency magnetron-sputtered TiO2 thin films by using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). A detailed analysis of the Ti 2p and O 1s NEXAFS edges allows determining the degree of order and the polymorphs of the investigated samples. We have found that thin films grown by using a Ti target and lower deposition rates have a rutile character, while, by using a TiO2 target and higher deposition rates, amorphous/mixed thin films are obtained. We have also found that this correlation between phase and preparation conditions is perfectly reproducible leading to films with equal characteristics for the same preparation conditions. The NEXAFS results are supported by complementary XRD results. [Copyright &y& Elsevier]

Abstract: CuO x –CeO2− δ /Si thin films were elaborated by pulsed laser deposition. At the surface of all CuO x –CeO2− δ thin films, Ce4+ and Cu+1 ions were present. Depth profiles indicated that a Cu2O rich layer, roughly 40nm thick, covered the CuO x –CeO2− δ thin films. Apart from the copper enriched surface, the copper repartition in the thin films is highly inhomogeneous and two types of copper oxides, CuO and Cu2O, in form of rounded grains 20nm were identified in the thin films. At least 10at.% Cu seems to be inserted in the ceria lattice. Pure CeO2 grains result from the deposition of tetrahedron-like nanoclusters followed by coalescence of (111) faces, and CuO x –CeO2− δ grains from the deposition of cube-like nanoclusters followed by coalescence of (110) faces. The good catalytic performances of the CuO x –CeO2− δ /Si thin films are due to active {100} ceria exposed facets covered by Cu2O nanoparticles. [Copyright &y& Elsevier]

Abstract: We study the initial growth stages of CdS thin films deposited by an ammonia-free chemical bath deposition process. This ammonia-free process is more environmentally benign because it reduces potential ammonia release to the environment due to its high volatility. Instead of ammonia, sodium citrate was used as the complexing agent. We used atomic force microscopy (AFM), Rutherford backscattering (RBS) and X-ray photoelectron spectroscopy (XPS) to investigate the morphological and chemical modifications at the substrate surface during the first initial stages of the CdS deposition process. Additionally, X-ray diffraction (XRD) and optical transmission spectroscopy measurements were carried out to compliment the study. XPS results show that the first nucleation centers are composed by Cd(OH)2 which agglomerate in patterns of bands, as demonstrated by AFM results. It is also observed that the conversion to CdS (by anionic exchange) of the first nucleus begins before the substrate surface is completely covered by a homogenous film. [Copyright &y& Elsevier]

Abstract: The geometric and electronic structure, the stability, and CO adsorption properties of pseudomorphic Pt overlayers and PtAu surface alloys on a Au(111) substrate have been addressed on the basis of first-principles calculations. We have found that two-monolayer thick surface alloys are more stable than one-monolayer thick alloys. The CO binding energies at the top sites of two-monolayer thick surface alloys increase gradually with the Pt concentration, while the energies are almost independent of the concentration for one-monolayer thick surface alloys. This difference is caused by the lower symmetry of the two-monolayer thick surface alloys, which makes the effect of neighboring atoms in the first layer more important. [Copyright &y& Elsevier]

Abstract: Using scanning tunneling microscopy, overlayer lattice structures and thin film morphology of copper phthalocyanine (CuPc) have been investigated while varying posterior, annealing temperatures. The room temperature deposition of CuPc on Ag(111) resulted in ordered domains, which were three molecular layers high and separated with disordered regions. The ordered surface also exhibited an oblique lattice with the lattice constants of 13.3Å and 16.4Å and the angle of 74° between the two. By annealing the thin films systematically to 580K, the symmetry of overlayer lattice increased from the oblique to the square lattice, commonly observed on various substrates. Further annealing to 780K desorbed much of the CuPc molecules. However, the remaining molecules reacted and formed dendrite-like chains, in which each CuPc molecule was linked through its isoindole rings. A possible model for the formation of dendritic chains through polymerization is discussed. [Copyright &y& Elsevier]

Abstract: We report on the structural evolution at the initial growth stage of perylene thin films on Au(111) surface. Scanning tunneling microscopy and spectroscopy have been employed to investigate the structural and electronic properties at 78K. Rapid molecular diffusion was observed at low submonolayer coverage. Molecules form an ordered structure at monolayer coverage. For the second layer, impinging molecules nucleate into molecular islands with an ordered intermediate structure. [Copyright &y& Elsevier]

Abstract: For organic molecular materials the definition of the condition of epitaxial growth has been subjected to several misconceptions and a great debate, leading in any case to less restrictive requirements than for inorganic materials. Here, the deposition of oligothiophene films by molecular beam epitaxy on properly grown organic single crystals is discussed and all-organic rigorous epitaxy demonstrated for both sub-monolayer and several-monolayer thick films. The possibility of growing all-organic nanostructures directly follows from these results. [Copyright &y& Elsevier]

Abstract: The adsorption kinetics, energetics and growth of naphthalene thin films, from submonolayer to about 10 layers, on a Ag(111) surface at low temperature in a ultrahigh vacuum chamber are examined by using temperature programmed desorption spectroscopy. The first layer adsorption occurs with a desorption energy of 85±5kJ/mole and results in an interface dipole of 5±1D, from charge transfer of approximately 0.2e from naphthalene to Ag. The surface dipole induced inter-adsorbate repulsion causes the lowering of the adsorption energy within the first layer near the saturation coverage so that the second layer deposition begins before the completion of the first layer. The second layer is a metastable phase with desorption energy, 74±3kJ/mole, smaller than the multilayer desorption energy of 79±5kJ/mole. Fractional order desorption kinetics were found for both the metastable and the multilayer phases, suggesting desorption from 2-D islanding and 3-D islanding, respectively. [Copyright &y& Elsevier]

Abstract: The breakdown in surface morphology during the growth of an 8nm thick Ga0.7In0.3N0.05As0.95 layer has been investigated by scanning tunnelling microscopy. During initial growth (<0.5nm) the alloy layer is planar but strained. Lateral composition modulation due to spinodal decomposition leads to the co-existence of tensile strained N-rich regions and compressively strained N-poor regions, creating an oscillatory strain field (OSF) across the surface. The overall strain increases with layer thickness up to ∼0.5nm, after which it is relieved by a transition from two-(2D) to three-dimensional (3D) growth, which manifests itself as an undulating, pitted layer. We propose that the region at the bottom of each pit is N-rich and that overgrowth of such regions is inhibited, thereby avoiding the strain caused by lattice mismatch. The results offer insight into the mechanisms involved in the breakdown of the 2D growth of thin dilute nitride layers at relatively high N concentrations. [Copyright &y& Elsevier]

Abstract: Molecular orientations of pentacene ultrathin films grown on SiO2 substrates were studied without the influence of the atmosphere by vacuum atomic force microscopy (V-AFM) and near edge X-ray absorption fine structure (NEXAFS). The experimental processes from deposition of pentacene to characterization of films were performed under vacuum condition without exposure to the atmosphere. V-AFM and NEXAFS measurements showed that pentacene molecules tend to grow on SiO2 surface with their molecular long axes perpendicular to the substrate surfaces (standing-mode) irrespective of preparation procedure of SiO2 substrate. [Copyright &y& Elsevier]

Abstract: SrBi2Ta2O9 (SBT) is a bismuth layered perovskite (BLP) with interesting ferroelectric properties for memories applications. The previous study on the synthesis of seeded and unseeded SBT thin films by the authors [G. González Aguilar, M.E.V. Costa, I.M. Miranda Salvado, J. Eur. Ceram. Soc. 25 (2005) 2331] has shown an increase of the crystallinity of the films and an improvement of the thin film ferroelectric properties when using SBT seeds. However, the detailed role of the seeds as an improver of the thin film properties has not been investigated so far. In the present work we study the role of the seeds, particularly with respect to the reactions between film and (bottom) underlying platinum electrode. The comparison of the results obtained by characterizing the seeded and unseeded thin films via Rutherford backscattering (RBS) and particle induced X-ray emission (PIXE) techniques reveals an effective modification of the substrate–thin film interface by the presence of the seeds. Moreover, the evaluation of the thin film ferroelectric properties by atomic force microscopy (AFM) shows an improvement of the local piezoelectric hysteresis loops by the seeds. These seeding effects as well as those observed in non-stoichiometric SBT thin films with different bismuth contents are used to discuss the barrier-like role of the SBT seeds against reactions between film and the platinum electrode and its contribution to the improvement of the thin film properties. [Copyright &y& Elsevier]

Abstract: The growth mechanisms and surface morphology of colossal magnetoresistance (CMR) La0.67Ca0.33MnO3 films deposited by rf magnetron sputtering on SrTiO3(001) substrates are investigated. The films are epitaxial, coherently strained and ferromagnetic. It is found that at early growth stages, in nanometric films, a layer-by-layer mechanism dominates, which results in step and terrace surface morphology. Upon further growth, the flat surface becomes unstable when large two-dimensional (2D) islands form. The Erlich-Schwoebel step-edge energy barrier induces an anisotropic adatom kinetics that favors 2D nucleation on top of the islands as it reduces downhill adatom current. As a result, there is an evolution with growth to mound-like structures of increasing height. Critical thickness for mound formation and average mound separation can be tuned by substrate miscut angle and growth temperature. These results provide a detailed understanding of the roughening process in manganites and are relevant for the controlled fabrication of CMR films, in particular for its use in epitaxial heterostructures. [Copyright &y& Elsevier]

Abstract: Two off-critical blends of poly(2-vinylpyridine) and polystyrene, 2:3 and 3:2 (w:w) PVP:PS, were spin-cast (with varied domain scale R) onto periodically (λ =4μm) patterned substrate. The pattern consisted of two alternating symmetric stripes: Au attracting PVP and neutral self-assembled monolayer. The resulting droplet-type morphologies were recorded with Scanning Force Microscopy and examined with integral geometry approach. PVP-rich islands of the 2:3 PVP:PS films form, for a wide R/λ range, strongly anisotropic morphologies. They show up, for R/λ ∼0.5, a weak λ/2-substructure of smaller PVP droplets in addition to the domains periodic with λ. The 3:2 blend exhibits morphologies with dominant λ-structure of PVP ribbons, which encircle PS droplets. For R/λ ∼0.5, smaller PS domains are also present but no λ/2-substructure is formed. The |χ E|-values of droplet surface density are reduced, as compared to homogeneous substrate, for the 3:2 blend (with |χ E|→0 for R ∼ λ). This effect is absent for the 2:3 mixture. [Copyright &y& Elsevier]

Abstract: We have studied the room-temperature growth of Cr on Ir(111) by scanning tunneling microscopy. Even in the low-coverage regime, up to a total coverage of 2 monolayers (ML), Cr does not grow in the layer-by-layer mode. Instead, we observe islands with local coverages Θ between 1ML and 5ML. While the 1st layer growth is pseudomorphic, sporadic defect lines are observed in the 2nd layer. For Θ ⩾3ML periodic one-dimensional dislocation lines appear indicating the onset of strain relief. Scanning tunneling spectroscopy reveals that islands with Θ =1ML exist in two modifications. Though their tunneling spectra are qualitatively rather similar, direct comparison shows that the main peak is shifted by about 15mV, resulting in peak positions of −0.255V and −0.270V. We interpret these two modifications as regular fcc Cr and Cr which exhibits a faulted hcp stacking on Ir(111), respectively. The assignment of fcc to areas directly attached to substrate steps together with the evolution of the ratio of the different ML-areas with coverage leads to the conclusion that hcp is the more favorable stacking. [Copyright &y& Elsevier]

Abstract: We report on scanning tunneling microscopy results of thin dysprosium-silicide layers formed on Si(111). In the submonolayer regime, both a and a 5×2 superstructure were found. Based on images taken at different tunneling conditions, a structure model could be developed for the superstructure. For one monolayer, a 1×1 superstructure based on hexagonal DySi2 was observed, while several monolayers thick films are characterized by a superstructure from Dy3Si5. [Copyright &y& Elsevier]

Abstract: (001)-Oriented tetragonal ferroelectric PbZr0.53Ti0.47O3 (PZT) thin films (90nm of thickness) have been grown on TiO x /Pt/TiO2/SiO2/Si and TiO x /Pt/MgO substrates. The existence of (100)-oriented crystallites in the c-axis matrix of the (001)-oriented films has been evidenced by using four circles X-ray diffraction. Depending on the substrate, the ratio of the lattice parameters c/a was found to be 1.02 (Si) and 1.07 (MgO) and this was correlated with the coercive field values. Local piezoelectric hysteresis loops produced by atomic force microscopy have been taken with profit to characterize the switching properties of the ferroelectric domains at the scale of individual crystallites. In each case, (100)-oriented crystallites require much higher voltage than (001)-oriented crystallites for switching. These results are explained by taking into account the strain imposed by the substrate in the film. We conclude that piezoelectric hysteresis loops produced by atomic force microscopy provide very rich information for addressing the local switching property of individual crystallites in PZT thin films. [Copyright &y& Elsevier]

Abstract: The long-range ordered p(2×2) self-assembled monolayer formed by dosing 2-mercaptobenzoxazole (MBO, C7H5NOS) on the Cu(100) surface at room temperature has been structurally characterised by means of normal incidence X-ray standing wavefield absorption (NIXSW) at both (200) and (111) reflections. The results show that the S atom, through which the adsorbed molecular thiolate species bonds to the surface, has an interlayer spacing of 1.33±0.05Å relative to the extended bulk scatterer planes (200) parallel to the surface and occupies the four-fold coordinated hollow site, with no evidence of major reconstruction. These results are entirely consistent with previous findings for a number of thiolates formed on (100) noble metal surfaces. The role of the head-group to surface potential corrugation and intermolecular interactions in determining the adsorption site and ordering of this aromatic molecular adsorbate is discussed. [Copyright &y& Elsevier]

Abstract: Growth modes of Co thin films on the both N-saturated and partially N-adsorbed Cu(001) surfaces are studied in detail. From results of the STM and XPS measurements, segregation of N atoms depending on the Co island size is concluded. This new type of atom segregation is explained by means of a lattice strain of the substrate due to the small Co island formation. A novel core-level shift of N1s during the Co film growth is also reported. A possible influence of the lattice strain to the electronic structure of the surfactant is discussed. [Copyright &y& Elsevier]

Abstract: Resonant photoemission was used to investigate the EuF3 ultrathin layer for the photon energies within the Eu 4d→4f excitation region. Photoemission from the valence band in resonance showed the lines which can be attributed to two Eu valence states (Eu+3 and Eu+2) whereas the off resonance spectra of EuF3 ultrathin layer do not exhibit divalent states of Eu. An explanation of that effect is proposed which is based on the charge transfer from the ligand. [Copyright &y& Elsevier]

Co-phthalocyanine molecules have wide range of optoelectronics and sensor applications. Motivated by the importance of this material, we studied the adsorption of CoPc thin to thick films on Au(111) surface by using ultraviolet photoelectron spectroscopy (UPS) coupled with angle resolved UPS (AR-UPS) and scanning tunnelling microscopy (STM). Molecular spectral emissions are found to be at 5.13, 7.94, and 10.32 eV below the Fermi level. Observed UPS and AR-UPS measurements show both changes and shifting in valence band features. The work functions of clean Au(111) surface and thick CoPc film are found circa 5.32 eV and 5.25 eV, respectively. Both the work function variation and shifting of molecular features dictate strong adsorbate-substrate interaction. AR-UPS measurements further illustrates that CoPc molecules lie flat on the Au(111) surface. Our STM results disclose that at sub-monolayer (Sub-ML, 0.4–0.8 ML) coverage and room temperature, CoPc molecules tend to adsorb in random fashions; which reveal a strong interaction at the CoPc-Au(111) interface. However, at the ML coverage and elevated temperature (~520K), long range pattern with the oblique structure is observed. Beyond ML coverage, existence of mixed phases consisting of well arranged patterns and molecular clusters have been observed. Overall, our STM results show that depending on the molecular thickness, CoPc molecules form three types of organized oblique, rectangular and square geometries which is consistent with the findings of CuPc and CoPc on Au(111) surface. Our findings may seek potential use in the organic molecular based electronic devices. • Thickness dependent electronic properties at the CoPc and Au(111) interface have been studied by means of UPS, ARUPS, and STM. • Valence level structures of CoPc molecules are found to be at 5.13, 7.94, and 10.32 eV below the Fermi level. • Work functions of the clean Au(111) surface and thick CoPc film are found to be 5.32 eV and 5.25 eV, respectively and IP of CoPc is found to be 5.89eV. • Angle resolved valence band (AR-UPS) measurements demonstrate that CoPc molecules lie flat on the adsorbate surface. • STM images reveal that CoPc molecules possess three packing arrangements, i.e. oblique, rectangular and square. [ABSTRACT FROM AUTHOR]

Abstract: Positioning nanostructures and functional molecules at surfaces and engineering their local coupling behavior is a key challenge in nanotechnology. The recently discovered BN nanomesh on the Rh(111) surface is a potential candidate to combine both properties, templating on the nanometer-scale and electronic decoupling. By means of low temperature scanning tunneling microscopy and spectroscopy experiments we demonstrate this advantageous combination for the case of Co nanoclusters, which can be ordered in a hexagonal nanoarray with a nearest neighbor distance of 3.2nm on the BN nanomesh. The detection of a Coulomb gap of ≈160meV proves the electronic decoupling of the clusters from the rhodium substrate. [Copyright &y& Elsevier]

Abstract: Valence electronic states of mono-atomic layer Co on the nitrogen adsorbed Cu(001) surface are studied by soft X-ray emission spectroscopy. The resonant X-ray emission spectrum can be divided into two components; one is that emitted from the single-layer Co islands and the other is that from more than 2ML thick Co films. The former has a narrower width and a lower binding energy than the latter. These results are in good agreement with the 3d density of states calculated by a first-principles method for single- and double-layer Co films on Cu(001), and clearly demonstrate narrowing of the 3d states in the single-layer. [Copyright &y& Elsevier]