M. P. J. Punkkinen

University of Turku | UTU · Department of Physics and Astronomy

High-k dielectrics Al2O3 and HfO2 are widely used in combination with Si to produce electronic components and solar cells. A negative fixed charge is known to appear at Si/high-k material interface after high-temperature annealing, yet the formation mechanism of the negative charge is poorly understood. In this work, we investigate the parameters a...

Low temperature treatments to control the Si-interface properties become more and more relevant to the broad Si-based electronics and photonics technology when the back-end-of-line processing is developed and the integration of hybrid materials on the Si platform increases. In this work we have investigated effects of NH3 nitridation of three diffe...

Growing SiO2 layer by wet-chemical oxidation of Si surfaces before growth of another insulating film(s) is a used method to passivate Si interfaces in applications (e.g., solar cell, photodiode) at low temperatures (LT) below 450 °C. We report on potential of LT ultrahigh-vacuum (UHV) treatments combined with the wet-chemical oxidation, by investig...

Properties of Ge oxides are significantly different from those of widely used Si oxides. For example, the instability of GeOx at device junctions causes electronic defect levels that degrade the performance of Ge-containing devices (e.g., transistors and infrared detectors). Therefore, the passivating Si layers have been commonly used at Ge interfa...

III-V semiconductor - oxide interfaces have attracted huge interest due to their substantial potential in electronic applications. However, due to the extreme complexity of the modeling of the interfaces, there are only few ab initio studies of these interfaces. Several model interfaces of native InPO4 oxides are designed in this study. It is shown...

The close similarity of silicon and germanium, isoelectronic group-IV elements, makes the integration of Ge layers on Si substrates suitable for technology development, but the atomic and electronic structures of Si1−xGex surfaces are still an open issue, in particular, for the alloy systems where Si is deposited on the Ge substrate. In this study,...

The adsorption of oxygen on bcc Fe–Cr(100) surfaces with two different alloy concentrations is studied using ab initio density functional calculations. Atomic-scale analysis of oxygen–surface interactions is indispensable for obtaining a comprehensive understanding of macroscopic surface oxidation processes. Up to two chromium atoms are inserted in...

Control of interfacial physicochemical properties associated with device materials to minimize the impact of point defects on device performance has been a dominant theme in the semiconductor industry. Control of the density of such defects for silicon has been well established for metal oxide-semiconductor field-effect device applications through...

Negative static charge and induced internal electric field have often been observed in the interfaces between silicon and high‐κ dielectrics, for example Al2O3 and HfO2. The electric field provides either beneficial (e.g., field‐effect passivation) or harmful (e.g., voltage instability) effect depending on the application. Different intrinsic and e...

Low-temperature (LT) passivation methods (<450 °C) for decreasing defect densities in the material combination of silica (SiO x ) and silicon (Si) are relevant to develop diverse technologies (e.g., electronics, photonics, medicine), where defects of SiO x /Si cause losses and malfunctions. Many device structures contain the SiO x /Si interface(s),...

Using scanning tunneling microscopy, x-ray photoelectron spectroscopy, and low-energy electron diffraction, we have studied clean and Ni-containing Si(1 0 0) surfaces and shown that the Ni contamination can easily appear at the Si(1 0 0) during its annealing at high temperature (1230 °C) because of migration of this impurity from heated parts of th...

X-ray photoelectron spectroscopy (XPS) is one of the most used methods in a diverse field of materials science and engineering. The elemental core-level binding energies (BE) and core-level shifts (CLS) are determined and interpreted in the XPS. Oxidation is commonly considered to increase the BE of the core electrons of metal and semiconductor ele...

Silica phases, SiOx forming at surfaces of various silicon crystals, e.g., Si wafers, nanowires, and nanoparticles via Si oxidation are key building blocks of diverse applications in the fields of electronics, medicine, and photonics for instance. The Si oxidation has been established to produce amorphous SiOx films, and the resulting oxide/silicon...

InAs crystals are emerging materials for various devices like radio-frequency transistors and infrared sensors. Control of oxidation-induced changes is essential for decreasing amounts of the harmful InAs surface (or interface) defects because it is hard to avoid the energetically favored oxidation of InAs surface parts in device processing. We hav...

Our understanding of bias-dependent scanning-tunneling-microscopy (STM) images is complicated not only by the multiplicity of the surface electronic structure, but also the manifold tunneling effects in probing semiconductor surfaces having directional dangling- and covalent-bond orbitals. Here we present a refined interpretation of empty-state STM...

Oxidation treatment creating a well-ordered crystalline structure has been shown to provide a major improvement for III-V semiconductor/oxide interfaces in electronics. We present this treatment's effects on InSb(111)B surface and its electronic properties with scanning tunneling microscopy and spectroscopy. Possibility to oxidize (111)B surface wi...

Effects of magnesium (Mg) alloying of GaxIn1−xAs(100) semiconductor surfaces have been investigated by low-energy electron diffraction, scanning tunneling microscopy/spectroscopy, and responsivity analysis of an infrared-detector component. In particular, the formation of an unusual Mg-induced (2 × 1) structure on GaAs(100) surfaces is found when d...

We investigated surface properties of metals by performing first-principles calculations. A systematic database was established for the surface relaxation, surface energy (γ), and surface stress (τ) for metallic elements in the periodic table. The surfaces were modeled by multi-layered slab structures along the direction of low-index surfaces. The...

Crystalline oxide phases on InSb(111)B revealed with scanning tunneling microscopy and spectroscopy

Control of defect densities at insulator/GaxIn1−xAs interfaces is essential for optimal operation of various devices like transistors and infrared detectors to suppress, for example, nonradiative recombination, Fermi-level pinning, and leakage currents. It is reported that a thin InOx interface layer is useful to limit the formation of these defect...

III-V semiconductors are prominent alternatives to silicon in metal oxide semiconductor devices. Hafnium dioxide (HfO2) is a promising oxide with a high dielectric constant to replace silicon dioxide (SiO2). The potentiality of the oxide/III-V semiconductor interfaces is diminished due to high density of defects leading to the Fermi level pinning....

Hydrogen, carbon, and oxygen are common unintentional impurities of Al(x)Ga(1-x)N crystals. This impurity structure and its interplay with Mg impurities in Al(x)Ga(1-x)N semiconductors are relevant to develop the p-type nitride crystals for various devices (e.g, LEDs, transistors, gas sensors), but are still unclear. Here we have investigated Mg-do...

Epitaxial Bi-containing III–V crystals (III-V1-xBix) have attracted increasing interest due to their potential in infrared applications. Atomic-scale characterization and engineering of bulk-like III-V1-xBix properties (e.g., Bi incorporation and defect formation) are challenging but relevant to develop applications. Toward that target, we report h...

Ab initio total-energy calculations, based on the exact muffin-tin orbitals method, are used to determine the equilibrium chemical configuration of alloy as a function of disorder and temperature. The transition from a substitutionally disordered face-centred-cubic crystallographic phase to an ordered phase is monitored using the coherent potential...

Strong Fermi-level pinning (FLP) near the valence-band maximum on n-type Ge surfaces has been a long-standing challenge in semiconductor physics, and the nature of this phenomenon has been heavily debated for years. Here, we report a systematic synchrotron-based photoemission study of atomically well-defined Ge(100) surfaces and interfaces to eluci...

We investigate the effect of short-range order (SRO) on the electronic structure in alloys from the theoretical point of view using density of states (DOS) data. In particular, the interaction between the atoms at different lattice sites is affected by chemical disorder, which in turn is reflected in the fine structure of the DOS and, hence, in the...

The oxidation of GaSb(100) surface has been widely studied because it affects the functionality of various devices. However even initial stages of the oxygen incorporation are not completely understood. To clarify this issue, we have investigated the oxidized GaSb(100) surfaces, which have been recently probed by scanning tunneling microscopy and s...

A novel simple method to produce a high-quality interface between semiconductor (e.g., Ge or III-V) and dielectric film (i.e., SiO2) is suggested. A nonoxygen element is deposited directly on an oxidized substrate at T ≥ 300 °C, leading to semiconductor reduction and dielectric film growth. As a result, the formed interface is atomically abrupt and...

Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investigate segregation, precipitation, and phase separatio...

TiO2/AlInP junctions are used to construct the antireflection coatings for solar cells and to passivate III–V nanostructure surfaces. The thickness of AlInP epilayer affects light absorption and appropriate Al composition determining further the energy barrier for carriers. We report on reducing the AlInP thickness by dry etching down to 10 nm with...

Oxidation of semiconductor surfaces is known to cause defect states at oxide-semiconductor interfaces of various devices. In contrast, effects of the semiconductor interaction with non-oxygen elements at such junctions are still unclear. We present evidence for the interrelationship between a metal (non-oxygen)-semiconductor reaction and formation...

The elastic properties of ferromagnetic Fe1-x-yMnyAlx (0≤x≤0.5, y=0, 0.1, and 0.2) random solid solutions in the body-centered cubic (bcc) crystallographic phase have been investigated using the ab initio exact muffin-tin orbitals method in combination with the coherent-potential approximation. Comparison with the experimental data demonstrates tha...

GaAs1-xBix alloys have useful properties for many optoelectronic applications. Although the crystal growth by molecular beam epitaxy is influenced by kinetics, it is also important to understand the thermodynamics of the alloys. The Gibbs formation energies and the immiscibility curve of the totally disordered GaAs1-xBix (0 ≤ x ≤ 1) are determined...

Atomic-scale knowledge and control of oxidation of GaSb(100), which is a potential interface for energy-efficient transistors, are still incomplete, largely due to an amorphous structure of GaSb(100) oxides. We elucidate these issues with scanning-tunneling microscopy and spectroscopy. The unveiled oxidation-induced building blocks cause defect sta...

Atomic structure of the Sr-adsorbed Si(100)(1 × 2) surface has been investigated by scanning tunneling microscopy (STM) and ab initio calculations. This surface reveals rows of Sr atoms between unbuckled Si dimer rows as well as an abundance of vacancy defects in the metal rows. The density of such defects can be minimized by the optimization of gr...

Segregation, precipitation, and phase separation in Fe-Cr systems is investigated. Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy are used. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bu...

The In 3d5/2 photoelectron spectroscopy peak has been widely used to determine the interface structures of In-containing III–V device materials (e.g., oxidation states). However, an unclear parameter affecting the determination of the energy shifts and number of the core-level components, and therefore, the interpreted interface structure and compo...

Atomic-scale understanding and processing of the oxidation of III–V compound–semiconductor surfaces are essential for developing materials for various devices (e.g., transistors, solar cells, and light emitting diodes). The oxidation-induced defect-rich phases at the interfaces of oxide/III–V junctions significantly affect the electrical performanc...

The pre-oxidized crystalline (3×1)-O structure of InAs(100) has been recently found to significantly improve insulator/InAs junctions for devices, but the atomic structure and formation of this useful oxide layer are not well understood. We report high-resolution photoelectron spectroscopy analysis of (3×1)-O on InAs(100) and InSb(100). The finding...

Atomic structure of interfaces between oxide layers and semiconductors is usually challenging to probe because of its buried nature. Here, we present a synchrotron photoemission approach to unveil the interface structure of BaO/Si(100), a prototype model of crystalline-oxide/semiconductor junctions, and demonstrate that such interface outspreads ov...

GaAs1 − xBix alloys attract significant interest due to their potentiality for several applications, including solar cells. Recent experiments link the crucial optical properties of these alloys to Bi clustering at certain Bi compositions. Using ab initio calculations, we show that there is no thermodynamical driving force for the formation of smal...

The exothermic nature of oxidation causes nearly all semiconductor applications in various fields like electronics, medicine, photonics, and sensor technology to acquire an oxidized semiconductor surface part during the application manufacturing. The significance of understanding and controlling the atomic scale properties of oxidized semiconductor...

The work of separation and interfacial energy of the Ni(1 1 1)/Cr(1 1 0) interface are calculated via first-principles methods. Both coherent and semicoherent interfaces are considered. We find that magnetism has a significant effect on the interfacial energy, i.e. removing magnetism decreases the interfacial energy of the semicoherent interface by...

Synthesis of layered SnO with a monocrystalline structure on a semiconductor substrate is demonstrated using a vacuum deposition method as well as diffraction, microscopy, and spectroscopy characterization.

Bismuth (Bi) induced c(4 × 4) surface structure of the GaAs(100) substrate, i.e., the GaAs(100)c(4 × 4)-Bi surface has been studied with synchrotron-radiation photoelectron spectroscopy and ab initio calculations. The surface was prepared by combining molecular beam epitaxy and in-situ electron diffraction methods, and then the sample was transferr...

In our previous study [Phys. Rev. B 86, 201104 (2012)] we introduced the so called quasi-non-uniform gradient-level exchange-correlation approximation (QNA) and demonstrated it's strength in producing highly accurate equilibrium volumes for metals and their alloys within the density-functional theory. In this paper we extend the scheme to include t...

The synthesis of novel functional crystalline films on semiconductor substrates calls for atomic-level knowledge and controlling of the initial stages of interface or junction formation. Technologically relevant epitaxial oxide films can be grown on Si(100) surfaces modified by submonolayer alkaline earth adsorbates, e.g., barium (Ba) and strontium...

Growing a crystalline oxide film on III-V semiconductor renders possible approaches to improve operation of electronics and optoelectronics heterostructures such as oxide/semiconductor junctions for transistors and window layers for solar cells. We demonstrate the growth of crystalline barium oxide (BaO) on GaAs(100) at low temperatures, even down...

We determine the interface energy and the work of separation of the Fe/Cr2O3 interface using first-principles density functional theory. Starting from different structures, we put forward a realistic interface model that is suitable to study the complex metal-oxide interaction. This model has the lowest formation energy and corresponds to an interf...

In this chapter, it is first described how the surface science and engineering of the III–V compound semiconductors are relevant to developing the semiconductor-based materials, including bismuth (Bi) containing III–V films, for improved electronics and optoelectronics devices. After that the general properties of the III–V(100) surfaces, which usu...

Clean and metal-adsorbed (100) surfaces of group-IV semiconductors, such as Si and Ge, often exhibit electronically and structurally similar reconstructions. However, the fundamental bulk properties of group-IV materials can have an impact on particular features of such systems, which are related, e.g., to final-state relaxation in photoemission an...

Surface and interface properties of Fe-Cr, Fe-Al, and Fe-Cr-Al are studied using Exact Muffin-Tin Orbitals and Monte Carlo methods and with x-ray photoelectron and Auger electron techniques. Surface composition is investigated as a function of oxidation (heating) time. Hard x ray photoelectron spectroscopy (HAXPES) is used to scan non destructively...

Ab initio calculations are employed to determine the lower and upper bounds of the interfacial energy and work of separation of a fcc-Ag/bcc-Fe interface. The strain-free interfacial energy of the coherent interface is taken as the lower bound and the interfacial energy of the commensurate incoherent interface as the upper bound of the interfacial...

Using ab initio alloy theory, we determine the elastic parameters of ferromagnetic and paramagnetic Fe1-cCrc (0 ≤ c ≤ 1) alloys in the body centered cubic crystallographic phase. Comparison with the experimental data demonstrates that the employed theoretical approach accurately describes the observed composition dependence of the polycrystalline e...

It was recently found that oxygen induces ordered reconstructions on several III–V surfaces. The most oxygen-rich reconstruction shows (3 × 1) periodicity. Based on first-principles investigations, a detailed atomic model is presented for this reconstruction. The uncommon periodicity is attributed to the highly stable InOIn trilayer below surface w...

Using first-principles total energy calculations we have found complex defects induced by N incorporation in GaAsN. The formation energy of the Ga interstitial atom is very significantly decreased due to local effects within the defect complex. The stability of the Ga interstitials is further increased at surfaces. The present results suggest that...

We determine the atomic surface structure of the Bi-terminated GaAs(001) (1 × 3) reconstruction for the first time using scanning probe microscopies, photoemission spectroscopy, and ab initio calculations. The proposed kinked-dimer (4 × 3) model is consistent with experimental characterization and can accommodate a variety of species configurations...

The flexibility of common generalized gradient approximation for the exchange-correlation energy is investigated by monitoring the equilibrium volume of transition metals. It is shown that no universal gradient-level approximation yielding consistent errors for all metals exists. Based on an element-specific optimization, the concept of quasi-non-l...

The elastic properties of paramagnetic (PM) Fe1−xMx (M = Al, Si, V, Cr, Mn, Co, Ni, and Rh; 0 ≤ x ≤ 0.1) solid solutions in the body-centered-cubic (bcc) and face-centered-cubic (fcc) structures are investigated using the exact muffin-tin orbital density functional method in combination with the coherent-potential approximation and disordered local...

Iron-chromium forms the basis of most of the stainless steel grades in the markets. Recently new insights into the physical and chemical properties of Fe-Cr based alloys have been obtained. Some of the new results are quite unexpected and call for further investigations. The present study addresses the magnetic contribution in the atomic driving fo...

Silicon dimer–containing reconstructions on Si(100) can be induced by submonolayer amounts of rare earth (RE) metals. The tilt of dimer bonds in such reconstructions can be controlled by the coverage and electronic properties of RE adsorbates. In this study, we have utilized improved high-resolution photoelectron spectroscopy with the synchrotron r...

The boosting effect of Cr on the growth of the protective alumina scale on Fe–Al alloys is investigated by X-ray photoelectron spectroscopy. Using low oxygen pressure the surface chemistry of the alloys is monitored starting from the first moments of oxidation. Chromium affects the Fe/Al surface-bulk exchange which is clearly detected by analyzing...

Using the projector augmented wave method within density functional theory, we present a systematic study of the layer relaxation, surface energy and surface stress of 3d transition metals. Comparing the calculated trends for the surface energy and stress with those obtained for 4d and 5d metals we find that magnetism has a significant effect on th...

Ab initio total energy calculations, based on the projector augmented wave method and the exact muffin-tin orbitals method in combination with the coherent-potential approximation, are used to examine the effect of magnesium on hydrogen absorption/desorption temperature and phase stability of hydrogenated ScAl1−xMgx (0⩽x⩽0.3) alloys. According to t...

The surface properties of Fe-rich ferromagnetic Fe–Cr alloys are investigated using a first-principles quantum-mechanical method. In dilute alloys, the surfaces are dominated by Fe, whereas the Cr-containing surfaces become favorable when the bulk Cr concentration exceeds the limit of ~ 10 atomic per cent. The abrupt change in the surface behavior...

Combining high-resolution photoelectron spectroscopy and density functional theory (DFT) calculations, 3d photoemission line shape and surface core-level shifts have been reinvestigated on the Ge(111)c(2 × 8) surface. It is found that 3d spectra include, in addition to the bulk and three surface-shifted components reported in literature, a componen...

Amorphous surface oxides of III–V semiconductors are harmful in many contexts of device development. Using low-energy electron diffraction and photoelectron spectroscopy, we demonstrate that surface oxides formed at Sn-capped GaAs(100) and InAs(100) surfaces in air are effectively removed by heating. This Sn-mediated oxide desorption procedure resu...

We have studied self-assembled bismuth (Bi) nanolines on the Bi-terminated InAs(100) surface by core-level and valence-band photoelectron spectroscopy, and ab initio first-principles calculations. A structural model for this intriguing surface is suggested based on the comparison of the measured and calculated core-level shifts. Also, the atomic or...

Previously found oxidized III-V semiconductor surfaces have been generally structurally disordered and useless for applications. We disclose a family of well-ordered oxidized InAs, InGaAs, InP, and InSb surfaces found by experiments. The found epitaxial oxide-III-V interface is insulating and free of defects related to the harmful Fermi-level pinni...

Tin (Sn) induced (1×2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface core-level shifts shows that these sur...

Because of the increased electron density within the surface layer, metal surfaces are generally expected to have tensile surface stress. Here, using first-principles density functional calculations, we demonstrate that in magnetic 3d metals surface magnetism can alter this commonly accepted picture. We find that the thermodynamically stable surfac...

Good high-temperature corrosion resistance of Fe–Al alloys in oxidizing environments is due to the α-Al2O3 film which is formed on the surface provided temperature is above 900 °C and the Al-content of the alloy exceeds the critical value. Ab initio calculations combined with experiments on Fe–13Al, Fe–18Al, Fe–23Al and Fe–10Cr–10Al alloys show tha...

Body-centered-cubic (bcc) iron is one of the most investigated solid-state systems. Using four different density-functional methods, we show that there is a magnetic transition close to the ground-state volume of bcc Fe, which originates from the particular magnetic band structure. The common equation of state functions, used to determine the basic...

Combining photoelectron spectroscopy and density-functional theory calculations, we have studied the atomic geometry of Yb/Si(100)(2×6) reconstruction and the mechanisms responsible for its stabilization as well as the influence of this reconstruction on Si 2p core-level photoemission. The analysis of measured and calculated surface core-level shif...

Ab initio electronic-structure methods are used to study the properties of Fe2P1−xSix in ferromagnetic and paramagnetic states. The site preference and lattice relaxation are calculated with the projector augmented wave method as implemented in the Vienna ab initio simulation package. The paramagnetic state is modeled by the disordered local magnet...

The polycrystalline elastic parameters of ferromagnetic Fe(1-x)M(x) (M = Al, Si, V, Cr, Mn, Co, Ni, Rh; 0 ≤ x ≤ 0.1) random alloys in the body centered cubic (bcc) crystallographic phase have been calculated using first-principles alloy theory in combination with statistical averaging methods. With a few exceptions, the agreement between the calcul...

Technologically useful indium- (In) terminated c(8×2)-reconstructed GaAs(100) substrate surface has been studied by first-principles calculations and scanning tunneling microscopy (STM) measurements. Our total-energy calculations demonstrate the stability of four different so-called ζa structures with In monomer rows and In coverage between 0.5 and...

The elastic properties of ferromagnetic Fe1−xMx (M=Al, Si, V, Cr, Mn, Co, Ni, and Rh; 0≤x≤0.1) random alloys in the body-centered-cubic (bcc) crystallographic phase have been studied using the all-electron exact muffin-tin orbitals method in combination with the coherent-potential approximation. The theoretical lattice parameters and the single-cry...

By means of scanning tunneling microscopy and spectroscopy (STM/STS), we have investigated the stability and the structure of atomic chains on Yb/Ge(111)3×2. STM allows the identification of different building blocks of this reconstruction, depending on the bias polarity and voltage, and validates the honeycomb chain-channel (HCC) structure with th...

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We have studied In-stabilized c(8 × 2)-reconstructed InAs(1 0 0) and InSb(1 0 0) semiconductor surfaces, which play a key role in growing improved III–V interfaces for electronics devices, by core-level photoelectron spectroscopy and first-principles calculations. The calculated surface core-level shifts (SCLSs) for the ζ and ζa models, which have...

The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that...

We investigate the basis set convergence of the exact muffin-tin orbitals by monitoring the equation of state for Al, Cu, and Rh calculated in the conventional face-centered-cubic lattice (str-I) and in a face-centered-cubic lattice with one atomic and three empty sites per primitive cell (str-II). We demonstrate that three (spd) muffin-tin orbital...

By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and first-principles calculations, we have studied the bismuth (Bi) adsorbate-stabilized InSb(100) substrate surface which shows a c(2×6) low-energy electron diffraction pattern [thus labeled Bi/InSb(100)c(2×6) surface] and which includes areas with metall...

We have studied, by means of ab initio calculations, the energetics and the atomic and electronic structures of various reconstructions induced by rare-earth metals (RE=Eu, Nd, Sm, and Yb) and Ba on Si(100) in the coverage range up to 0.5 monolayer. It is shown that Si dimer buckling is an important structural element for such systems, leading freq...

A novel aluminium rich alloy for hydrogen storage has been discovered, ScAl0.8Mg0.2, which has superior properties regarding hydrogen storage capacity, kinetics and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. Detailed analysis of the hydrogen absorption in ScAl0.8Mg0.2 has been p...

The reversal of the magnitudes of the bulk and surface chemical-potential differences induces the outburst of Cr on the otherwise pure Fe surface of Fe-Cr alloys. This threshold value for the Cr content is about 10at.% . It is found that vanadium addition to Fe-Cr shifts the Cr threshold to a substantially lower value suggesting V having a positive...

Surface core-level shifts (SCLSs) of the (2 × 4)-reconstructed InP(1 0 0) surface with the established mixed In–P dimer structure have been investigated by first-principles calculations and photoelectron spectroscopy. Theoretical values were calculated using both the local density approximation (LDA) and the generalized gradient approximation (GGA)...

DOI:https://doi.org/10.1103/PhysRevB.79.149902

Ab initio total-energy calculations, based on the exact muffin-tin orbital method, are used to determine the elastic properties of Pd{sub 1-x}Ag{sub x} random alloys in the face-centered-cubic crystallographic phase. The compositional disorder is treated within the coherent-potential approximation. The single crystal and polycrystalline elastic con...

Duplex stainless steels have many superior properties compared to conventional steels, this being mainly due to their microstructure containing approximately equal amount of ferrite and austenite phases formed by iron, chromium (or Cr equivalent), and nickel (or Ni equivalent). Using computational methods based on first-principles theories, the pha...

The Yb growth on a vicinal Si(1 0 0) surface has been studied by scanning tunneling microscopy and low energy electron diffraction in the coverage range of 1–4 ML. Two different methods of the Yb/Si(1 0 0) interface formation are applied, leading to a remarkable modification of structural and morphological properties of two-dimensional (2D) wetting...

Bismuth adsorbate-stabilized (2×1) and (2×4) reconstructions of the GaAs(100) surfaces have been studied by first-principles calculations, valence-band and core-level photoelectron spectroscopies, and scanning tunneling microscopy. It is demonstrated that large Bi atom size leads to the formation of the pseudogap at the Fermi energy and to the lowe...

We report here a combined theoretical and experimental study of Yb/Si(100)−(2×3) and −(2×4) reconstructions by means of first-principles calculations and high-resolution core-level photoelectron spectroscopy. Energetically stable atomic structures are presented for these reconstructions. Yb atoms are found to occupy the cave sites in the structures...

By considering GaAs(110) and Si(100)(2×1) surfaces, it is shown that the use of the pseudohydrogen atoms to saturate the dangling bonds at one side of the slab modeling a free surface can lead to distorted surface core-level shifts within the complete screening picture. The effect is linked to the polarization of the slab and to the change in the b...

Due to the lower compressibility of the close-packed crystallographic planes compared to the less close-packed ones, the open free surfaces of the late transition and noble metals are generally expected to become thermodynamically stable with increasing pressure. Surface segregation in concentrated alloys and heteroepitaxial growth are possible mec...