Milorad Milun

Institute of Physics, Zagreb · Surface science

Significance Surfaces are gates to control the transport of energy and materials between the gas phase and bulk. For the hydrogen storage, the transport of hydrogen across the surface is recognized as the bottleneck, e.g., 1 H 2 in 1,000 impinging a Pd surface penetrates the surface. Here, we demonstrate that alloying the Pd(110) surface with submo...

It is common knowledge that even a trace amount of a chemisorbed species can strongly perturb the surface electronic structure, in particular the surface states, to the point of their complete eradication. We have confirmed this behavior by adsorbing Li on the Ir(111), but surprisingly, we have discovered that in the presence of graphene Li does not...

CuxO is known as an electrochromic material with a possible applicability for solar-light modulation. The reversible transition between the two different oxidation states, CuO and Cu2O, is responsible for the visible-light switching ability. CuxO films in their as-prepared, colored and bleached states were subjected to a surface analysis in order t...

Introduction The Types of Metallic Quantum Wells Electronic Properties of Quantum Wells – Dimensional Aspects Quantum Well Potentials Modeling of Quantum Wells Concluding Remarks References

Properties of many layered materials, including copper- and iron-based superconductors, topological insulators, graphite and epitaxial graphene, can be manipulated by the inclusion of different atomic and molecular species between the layers via a process known as intercalation. For example, intercalation in graphite can lead to superconductivity a...

From the experimental studies of surface adsorption of Cs atoms and their intercalation under epitaxial graphene on Ir(111) it is known that both - adsorbed and intercalated phase of Cs atoms coexist. However, adsorbed phase is realized as a diluted superlattice adlayer of Cs atom while intercalated phase is a dense Cs layer. The preference for int...

Titanium dioxide thin films were deposited by filtered cathodic arc evaporation (FCAE) from a Ti target in an oxygen atmosphere onto (a) fluorine-doped tin oxide substrates SnO2:F (FTO) and (b) glass microscope slides. The growth rate calculated from film thickness profilometry measurements was found to be approximately 0.8 nm/s. The films were hig...

We present experimental data on the temperature dependence of photo-hole decay obtained by Angle Resolved Photoemission (ARPES) measurements from 4d derived Quantum Well States (QWS) on Ag(111) monolayer films deposited on Pd(111), Ni(111), Mo(110) and Cu(100). We have found a significant increase of the Ag 4d electron–phonon (e-ph) coupling streng...

We analyze renormalization of the pi band of n-doped epitaxial graphene on Ir(111) induced by electron-phonon coupling. Our procedure of extracting the bare band relies on recursive self-consistent refining of the functional form of the bare-band until the convergence. We demonstrate that the components of the self-energy, as well as the spectral i...

Angle-resolved photoelectron spectroscopy (ARPES) is extensively used to characterize the dependence of the electronic structure of graphene on Ir(111) on the preparation process. ARPES findings reveal that temperature-programmed growth alone or in combination with chemical vapor deposition leads to graphene displaying sharp electronic bands. The ph...

In this paper we briefly review electronic properties of quantum well states in metallic films deposited on metallic substrates. We discuss the photoemission spectroscopy from QW states by addressing the questions of their energy, in-plane dispersion, dependence on supporting structure, hybridization with substrate bands, and many-body effects with...

The initial stage of gold oxidation at the quartz crystal electrode in a near neutral solution was studied by using potentiostatic and potentiodynamic sweep methods. The underpotential deposition of OH radicals was the first stage of the nucleation and formation of the phase oxide Au2O3. The composition of the oxide was determined by the X-ray phot...

We studied the growth mode and electronic properties of ultra-thin silver films deposited on Ni(1 1 1) surface by means of scanning tunnelling microscopy (STM) and angle resolved photoemission spectroscopy (ARPES). The formation of the 4d-quantum well states (QWS) was analysed within the phase accumulation model (PAM). The electronic structure of t...

We report a study of 4d electronic states in monolayer silver films grown on Pd(111), Ni(111), Mo(110) and Cu(100) surfaces studied by means of high-resolution angle-resolved photoemission spectroscopy (ARPES). The Ag-4d states, when measured in the surface Brillouin zone centre (SBZ), show substrate-dependent shifts. Density functional theory (DFT...

Thin tin-oxide (SnOx) films were deposited by atmospheric pressure chemical vapor deposition (APCVD) and exposed to hydrogen plasma. The influence of such treatment on the films properties was investigated by X-ray diffraction (XRD), UV–visible spectroscopy, scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS) and grazing inci...

The surface segregation of copper was investigated in laboratory and industrial non-oriented electrical steel sheets containing copper. The cold-rolled samples of Fe-Si-Al alloys were annealed in the temperature range 320-1 120 K in the ultra-high-vacuum chamber of a field-emission Auger electron spectrometer, and subsequently characterized by Auge...

Structural and electronic properties of surfaces and ultrathin metallic films are closely connected. Because of their low dimensionality it is of the utmost importance to acquire their structural details at atomic level and their electronic structure resolved in energy and momentum at very high resolution. In this paper, we briefly review several e...

We present a combined, experimental, and computational investigation of the growth mode and the valence-band structure of Ag/ Pd111, with the focus on the Ag 4d derived quantum well states. Low-energy electron diffraction and scanning-tunneling microscopy are used to determine epitaxial, layer-by-layer growth of silver on the palladium substrate. H...

The electronic structure of 1–5 monolayer (ML) thick silver films on V(100) is investigated with scanning tunneling microscopy and compared to photoemission measurements. Using room temperature scanning tunneling microscopy in the constant current mode, standing waves were imaged for all film thicknesses. The Fourier transforms of the images were i...

Ultra thin silver films deposited on Cu(100) have been studied by high energy and angle resolved photoemission spectroscopy (ARPES), scanning tunnelling microscopy (STM) and low electron energy diffraction (LEED). An effective spin–orbit splitting in the Ag 4d was measured as the morphology of deposited silver was changing from the silver–copper al...

We report an angle-resolved photoemission study of d-derived quantum well (QW) states in ultrathin silver films grown on V(100). Distinct d-derived QW states were observed for film thicknesses between 1 and 5 ML. Using a line shape analysis we conclude that for thicker films the d electrons are almost completely confined within the silver overlayer...

The growth and structure of ultrathin silver films (1–5 monolayers thick) deposited on a reconstructed V(100)-(5×1) surface have been studied by means of scanning tunneling microscopy (STM), Auger electron spectroscopy (AES), and angle-resolved photoemission spectroscopy (ARPES). To model the structure of the system we have also performed density f...

In this study, for the first time, it is shown how the heating of an In–80Sn alloy affects its morphology and surface chemical composition. The study of the initial phases of surface oxidation of the pure In–80Sn alloy at room temperature revealed the formation of a mixture of In2O3, SnO and SnO2 oxides with a dominant contribution of In2O3. The hi...

A simple ultrahigh-vacuum-compatible Se deposition source is developed. It consists of a resistively heated crucible enveloped by a copper tube that also has provisions for liquid nitrogen cooling. The temperature of the crucible is measured via an Ni/NiCr thermocouple. All feedthroughs are executed through a CF 70 mm OD flange, which enables the S...

The reconstructed V(1 0 0)-(5×1) surface has been studied by means of the field emission high-resolution Auger electron spectroscopy (HRAES), scanning tunnelling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) using synchrotron radiation. The obtained HRAES data show that on the nano-meter scale the reconstructed V(1 0 0)-(5×...

In scanning tunnelling microscope images of thin Al2O3-films grown on Ni3Al(111) at 1000 K two super-lattices with periodicities of 2.6 and 4.5 nm, respectively, can be identified. These well-ordered nanostructures can be used as nucleation centres for metal particle growth. It can be shown that both nanostructures act as a template for the fabrica...

A brief review of the high spatial resolution Auger electron spectroscopy (HRAES) and its usage in metallurgy is presented. A combination of HRAES and X-ray photoelectron spectroscopy makes a powerful combination to resolve a large number of problems encountered in metallurgy. Several selected examples of such problems studied in the authors' labor...

The quantum wells formed by ultra-thin metallic films on appropriate metallic substrates provide a real example of the simple undergraduate physics problem in quantum mechanics of the `particle in a box'. Photoemission provides a direct probe of the energy of the resulting quantized bound states. In this review the relationship of this simple model...

The growth of different metals on thin Al2O3-films on Ni3Al(111) was investigated using scanning tunneling microscopy (STM). These thin alumna films are well ordered showing two superstructures, which appear in the STM images at different bias voltages. These superstructures, with periodicities of 2.6 and 4.5 nm, respectively, are shown here to gov...

Ultrathin metallic films may act as quantum boxes when some con-ditions are met. Here, we discuss these conditions for the simplest case of one-dimensional confinement and we review some of the pro-perties that emerge from the reduced dimensionality of the films. We emphasize the difference between extremely thin layers of up to several monolayers...

The temperature dependence of angle-resolved photoemission from quantum-well states in ultrathin films of Ag on V(100) has been examined for films from 1–8 ML thickness within the temperature range 45–600 K. Contrary to bulk solids, the photoemission peaks shift to higher binding energy as the temperature is increased. The temperature dependence of...

The growth of different metals on thin Al O -films on Ni Al(111) was investigated using scanning tunneling microscopy 2 3 3 (STM). These thin alumna films are well ordered showing two superstructures, which appear in the STM images at different bias voltages. These superstructures, with periodicities of 2.6 and 4.5 nm, respectively, are shown here...

The temperature dependence of peak widths in high-resolution angle-resolved photoelectron spectroscopy from quantum well states in ultra-thin Ag films on V(100) has been used to determine the electron-phonon coupling constant, λ, for films of thickness 1-8 layers. A strong oscillatory variation in coupling strength is observed as a function of...

The lifetime of quantum well states in ultra thin Ag films on V(100) is studied by high resolution angle-resolved photoemission spectroscopy. The temperature dependence of the quantum well state (QWS) peak widths is used to determine the electron-phonon coupling constant for 1 8 monolayers (ML) thick films. Intense variation in coupling strength is...

The X-ray photoelectron spectroscopy (XPS) is used in this work to characterize the oxide layer produced by long-term exposure to boiling 55% HNO3 of the austenitic alloyed cast steel FeCr26Ni30Si4, containing 4% of silicon. As a result, a very thin mechanical barrier was produced with thickness only about approximately 2 nm. On the surface, silico...

In this work we study the evolution and electronic properties of copper ultra-thin films grown at room temperature on a V(110) single crystal surface using angle-resolved ultraviolet photoemission spectroscopy (ARUPS), X-ray photoemission spectroscopy ( XPS), Auger electron spectroscopy (AES) and low-energy electron di V raction (LEED). Up to 5 mono...

The stabilizing effect of rhodium addition to ruthenium coatings on titanium under anodic polarization in acidic solutions is described. The addition of rhodium to the coating leads to both an overall improved stability of the electrode, and an increase of the electrochemically active surface area. The service-life of a Rh-Ru coating polarized at 0...

Extensive measurements have been made of the photoemission intensities recorded along the surface normal from quantum-well (QW) states of pseudomorphic Ag layers on V(100) in thicknesses from 1–7 ML as a function of photon energy in the range 15–45 eV. In all cases the QW states lead to intense peaks in the photoemission spectra which show strong o...

The electronic structure of the V(100) surface has been studied by means of angularly resolved photoelectron spectroscopy (ARUPS) and momentum- ( k-) resolved inverse photoemission spectroscopy (KRIPES). A narrow peak in the photoemission spectrum which is seen at the Fermi level is attributed to a transition from a surface resonance. The existence...

Normal-emission photoemission spectra from the quantum well state in a single monolayer of Ag on V(100) have been studied as a function of photon energy. By comparing the measured binding energy and calculated electron momentum perpendicular to the surface in this state with the unoccupied s-p bands of Ag and V, we show that the peak intensity corr...

The electronic structure of V(100) has been studied by means of synchrotron radiation. Normal emission (n.e.) spectra, taken in the energy range between 15 and 100 eV, were analysed in terms of existing band structure calculations. The obtained data support our previous reports suggesting that the peak at the Fermi level has a bulk and surface comp...

Scanning tunneling microscopy is used to characterize different states of the V(100) surface during the cleaning procedure in an ultrahigh vacuum apparatus, starting with the "as received" sample and finishing with an almost perfectly clean surface. We show, for the first time, STM images of the clean V(100) surface and with atomic resolution.

Normal emission photoemission spectra from a single ordered monolayer of Ag on V(100) show a sharp and intense peak associated with a quantum-well state. The photon energy dependence of the intensity of this peak shows an identical enhancement profile to the V 3d photoemission in the vicinity of the V 3p --> 3d excitation threshold, characteristic...

The electronic properties of ultra-thin vanadium films grown on the Cu(100) surface are studied by means of angular photoemission spectroscopy (ARUPS). Vanadium films with nominal film thickens of 4 ML appear to have fully developed valence band characteristic for the bulk vanadium. Influence of hydrogen on the valence band spectrum of vanadium is...

Thin films of AlW alloys were prepared by co-deposition of pure aluminum and pure tungsten, each sputtered by an independently controlled magnetron source. The deposition rate at the substrate (glass, fused quartz, and alumina ceramic), positioned 5 cm away from the target surface was 0.1–0.2 nm/s for pure metals, and the final film thickness was a...

The growth mode, structural and electronic properties of vanadium ultra-thin films deposited on Cu(100) at room temperature were studied by means of Auger electron spectroscopy, low energy electron diffraction and angular-resolved photoemission. The results of all measurements are consistent with a picture of simultaneous multilayer growth of vanad...

In this study, Inconel-600 (Ni–Cr–Fe alloy) was modified by repetitive potential cycling in 1M NaOH solution. This procedure induced the growth of a hydrous oxide film, following the same mechanism as previously reported for pure nickel in alkaline solution under similar experimental conditions. The electrode, modified by 30 repetitive potential cy...

Growth modes and electronic properties of ultra-thin films of copper deposited on the V(100) surface were studied over a wide temperature range (220–1200 K). XPS, LEED, TDS and angular resolved UPS data are presented. At 300 K, initially, two copper layers grow in an ordered, “layer-by-layer” mode, in registry with the V(100) surface. These layers...

Angular-resolved photoemission and inverse-photoemission spectroscopies have been used to investigate the valence-electron states in ultrathin films of silver and copper deposited on a V(100) surface. For both noble metals, discrete {ital s}-{ital p} derived states are observed within the {Delta}{sub 1} gap of the vanadium substrate (approximately...

We report an experimental study of the CVV Auger transition of vanadium. A comparison between the experimental spectrum and the self-convolution of the calculated density of states (DOS) failed to show any significant shift between the spectra as reported for Ti and Sc. We have also found good agreement between our experimental and Contini's et al....

Passive film formation as a function of applied potential on tin in citrate buffer solution was studied by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In order to avoid air oxidation and to minimise contamination of the samples, an electrochemical preparation and transfer system attached to the ultrahigh vacuum system was used. Q...

The antimony surface segregation was investigated on surfaces of a polycrystalline Fe-Si alloy with 0.05 wt. % Sb, under UHV conditions, in the temperature range from 450 to 950 ° C. The grain boundary segregation in experimental alloys was negligible. It was concluded that the texture formation results from orientation-dependent effects of antimon...

The interaction of silver ultrathin films and chemisorbed oxygen is studied on the V(100) surface using AES, XPS and UPS techniques. It is found that oxygen induces a disordering of silver films even at 220 K. The disordering of the films is more pronounced at higher temperatures. Above 600 K the diffusion of oxygen into the vanadium bulk takes pla...

The properties of the vanadium valence band have been studied by normal emission ultraviolet photoelectron spectroscopy from V(100) surface by the use of different photon energies (21.2, 16.8 and 11.8 eV). The bottom of the d-band at the high symmetry point H12 was found to be around 2.5 eV. We did not find conclusive evidence for the existence of...

A growth mode of silver ultrathin films on the V(100) surface was studied by Auger electron spectroscopy, angular resolved ultraviolet photoelectron spectroscopy. X-ray photoelectron spectroscopy, thermal desorption spectroscopy, low energy electron diffraction, electron energy loss spectroscopy and work function change (w.f.c.) measurements. The f...

The anodic stability of an electrodeposited ruthenium electrode was measured by anodic galvanostatic polarization in 0.5 mol dm–3 H2SO4 solution. The role of water and adsorbed hydroxyl groups in electrode stability was determined by means of thermogravimetric analysis. A continuous weight loss due to water removal and condensation of hydroxyl grou...

Growth modes and properties of ultra-thin films of silver on a V(100) surface were studied by means of AES, XPS, UPS, TDS and LEED techniques. The experiments were carried out in a temperature range 50–1100 K. Above room temperature the films grow following the Stranski-Krastanov mode with two layers of silver serving as a substrate for clusters. T...

Edge‐defined film‐fed grown polycrystalline silicon sheets, grown with one face exposed to oxidizing CO gas added to the inert Ar atmosphere, were studied. Interaction of CO with molten silicon surface during growth produced SiC‐like structures in a thin layer on the surface exposed to CO. Infrared spectroscopy results suggest that this layer is co...

Gold ultra-thin films deposited on V(100) surface at 120 and 300 K were characterized by AES, UPS and XPS at different stages of film growth and after an annealing treatment. The work function (WF) changed from 4.3 eV at zero Au coverage to 5.6 eV at a bulk-like film. The Au 5d splitting at low coverages was 1.4 eV. At the same time, the Au 4f peak...

A detailed procedure required to obtain an atomically clean and well-ordered vanadium (100) surface is described. The measured valence band spectra are in agreement with theoretical predictions and some experimental findings. The work function of the clean and well-ordered V(100) is found to be 4.3 ± 0.1 eV.

We have determined electron energy band dispersion of the vanadium valence bands along the HGN high symmetry direction of the bulk Brillouin zone by use of angular-resolved photoemission spectroscopy of the V(100) surface. The dispersion of the states associated to the electron transitions from the bands G1 and G3 were found to be in very good ag...

X-ray photoelectron spectroscopy and Auger electron spectroscopy were used for the characterization of an electrodeposited ruthenium electrode (unactivated) and an electrode subjected to electrochemical activation. The characterization was performed at room temperature and after 30 min of annealing at 400, 520 and 640 K. It was found that, at room...

Thermal stability of TiO2 thin polycrystalline films obtained by the very simple chemical vapour deposition method on the quartz, molybdenum and gold substrates have been examined by X-ray photoelectron and Auger spectroscopy (XPS and AES), respectively, before and after annealing in vacuum at temperatures from 298 K to 1200 K. In this temperature...

The anodic behaviour of galvanically plated ruthenium-iridium coatings on titanium was investigated. The dependence of the Tafel slopes and the stability of the coatings for the oxygen evolution reaction in sulphuric acid on the electrode composition was established. A change in the Tafel slope from 33 to 90 mV per decade on going from pure rutheni...

The adsorption behavior of oxygen on Cu submonolayer, monolayer and multilayer films epitaxially grown on a Ru(0001) substrate is studied by AES, LEED, TDS and Δφ-measurements. In the presence of coadsorbed oxygen and below 500 K the Cu films preserve a layered structure. In the case of θCu < 1 ML the interaction is dominated by the free Ru(0001) s...

The influence of defects in thin metal films was studied for Cu films deposited on a Ru (001) surface at 40 K by means of angular resolved photoelectron spectroscopy (ARPES), photoemission of adsorbed xenon (PAX) and work function measurements. The cold deposited films are dominated by defects and the defect concentration at their surfaces is hardl...

Silver interaction with a Pd(110) surface was investigated, in a wide range of Ag coverages, by means of UPS, XPS and TDS. Our XPS measurements of the 3d levels of both Ag and Pd show significant shifts of the Ag signal as a function of Ag coverage, while the Pd level position remains constants. Both, silver and palladium 3d level binding energies...

An adapter is described that enables one to use a nonbakable closed‐loop helium cryostat in ultrahigh‐vacuum experiments. The adapter is fully bakable, simple and cheap, and has been designed specifically for systems where a sample holder is mounted to an x,y,z‐rotational manipulator. During bakeout of the ultrahigh‐vacuum apparatus the cold head o...

High coverage thermal desorption (TD) spectra of oxygen taken from Pd(110) and Pd(polycrystal) surfaces after oxygen exposure at Tad = 510 K are shown and discussed in terms of possible intermediate states of oxygen between two limiting cases: chemisorbed oxygen on the surface and bulk palladium oxide. Both sets of TD spectra exhibit complexity whi...

The influence of localized surface fields arising from local surface potential differences near structural and chemical surface irregularities on chemisorbed molecules is simulated by ab initio SCF-LCAO cluster calculations with a linear CO-Al cluster in the presence of an external point charge. Our exploratory study substantiates the notion of a l...

Using thermal desorption spectroscopy (TDS) the interaction of gaseous oxygen with a polycrystalline palladium foil was studied for the first time over a very wide temperature (110 < T < 1400 K) and exposure (10 000 L) range. Since studies with polycrystalline and defect surfaces are generally hampered by a serious lack of structural information, t...

The interaction of oxygen with a Pd(110) surface was studied mainly by means of thermal desorption spectroscopy (TDS); some Auger electron spectroscopy (AES) results are also presented. The results obtained show that at low adsorption temperatures (Tad < 160 K) oxygen adsorbs molecularly. Atomic oxygen is also present but it may be the consequence...

The parameter Y, the ratio between the full width at half maximum (FWHM) and the temperature at peak maximum (Tp), may be easily obtained from thermal desorption (TD) spectra. In this paper we exploit the functional dependences of Y on the coverage θ, the adsorption energy E(θ), and the pre-exponential factor v(θ) using computer simulations, and de...

The adsorption of oxygen on Pd(foil) was studied with thermal desorption spectroscopy (TDS) between 110 and 1400 K. Prior to the oxygen adsorption studies the surface topography of the Pd foil was characterized by PAX (photoemission of adsorbed xenon). First order desorption of molecular oxygen was found at 160 K. Dissociative adsorption occurs at...

In an attempt to detect possibly hyperconjugative, homohyperconjugative and/or steric interactions in the title compound specifically deuterated 7-norbornyl triflates 3-8-OTf were solvolyzed in aqueous trifluoroethanol. 3-OTf and 4-6-OTf showed normal, positive isotope effects (kH/kD > 1). The α-effect of 1.13 in 3-OTf is interpreted as being due t...

The topological resonance energy, TRE, concept is introduced. TRE values depend solely on topology of a conjugated system and do not contain any additional parameters outside the MO method used (in the present work Hückel theory is employed). TRE values are reported for a number of conjugated hydrocarbons, heterocycles, conjugated ions, and radical...