E. Guziewicz - Academia.edu (original) (raw)

Papers by E. Guziewicz

Journal of Alloys and Compounds, 1999

Resonant photoemission spectroscopy has been applied to study the group of Pb1−xRExBVI (RE=Eu, Gd... more Resonant photoemission spectroscopy has been applied to study the group of Pb1−xRExBVI (RE=Eu, Gd; B=Te, Se, S) diluted magnetic semiconductors. Energy distribution curves, as well as constant-initial-state or constant-final-state photoemission spectra have been taken for photon energies near to the intra-ion Eu 4d→4f or Gd 4d→4f transitions. The Eu 4f and Gd 4f contributions to the electronic structures of the

Progress in Surface Science, 2001

The paper presents the experimental results of the electronic band structure study of the semicon... more The paper presents the experimental results of the electronic band structure study of the semiconductor crystal clean surface and this surface doped by transition metal or rare earth metal atoms. For clean surfaces of the CdTe crystal the two-dimensional electronic band structure E(k) dependence was determined for surface states located in the valence band energy region. The doping of the

Journal of Crystal Growth, 2009

We report on properties of low-temperature (LT) ZnO films grown by the atomic layer deposition me... more We report on properties of low-temperature (LT) ZnO films grown by the atomic layer deposition method with diethylzinc (DEZn) precursor. It is shown that the ZnO thin film crystallographic orientation, quality of the surface, and optical properties depend on the main growth parameters like temperature, pulsing, and purging time and thus can be varied in controllable manner. All the presented

Optical Materials, 2010

Optical and magneto-optical properties of ZnMnO films grown at low temperature by atomic layer de... more Optical and magneto-optical properties of ZnMnO films grown at low temperature by atomic layer deposition are discussed. A strong polarization of excitonic photoluminescence is reported, surprisingly observed without splitting or spectral shift of excitonic transitions. Present results suggest possibility of Mn recharging in ZnO lattice. Strong absorption, with onset at about 2.1 eV, is related to Mn 2+ to 3+ photo-ionization. We propose that the observed strong circular polarization of excitonic emission is of a similar character as the one observed by us for ZnSe:Cr.

Microelectronic Engineering, 2008

Properties of ZnO films grown by atomic layer deposition at low temperature are described. By sel... more Properties of ZnO films grown by atomic layer deposition at low temperature are described. By selecting appropriate precursors and their pulses we obtained films with controlled electrical properties -from heavily n-type to p-type. Parameters of constructed Schottky and p-n junction are good enough for their application in a new generation of memory devices with cross-bar architecture.

Optical Materials, 2009

Optical properties of ZnMnO layers grown at low temperature by Atomic Layer Deposition and Metalo... more Optical properties of ZnMnO layers grown at low temperature by Atomic Layer Deposition and Metalorganic Vapor Phase Epitaxy are discussed and compared to results obtained for ZnMnS samples. Present results suggest a double valence of Mn ions in ZnO lattice. Strong absorption, with onset at about 2.1 eV, is tentatively related to Mn 2+ to 3+ photoionization.

Semiconductor Science and Technology, 2012

Despite many efforts, the origin of a ferromagnetic (FM) response in ZnMnO and ZnCoO is still not... more Despite many efforts, the origin of a ferromagnetic (FM) response in ZnMnO and ZnCoO is still not clear. Magnetic investigations of our samples, not discussed here, show that the room temperature FM response is observed only in alloys with a non-uniform Mn or Co distribution. Thus, the control of their distribution is crucial for the explanation of contradicted magnetic properties of ZnCoO and ZnMnO reported till now. In this paper, we discuss advantages of the atomic layer deposition (ALD) growth method, which enables us to control the uniformity of ZnMnO and ZnCoO alloys. Properties of ZnO, ZnMnO and ZnCoO films grown by the ALD are discussed.

Physical Review B, 2013

A series of (Zn,Co)O layers with Co contents x up to 40% grown by atomic layer deposition have be... more A series of (Zn,Co)O layers with Co contents x up to 40% grown by atomic layer deposition have been investigated. All structures deposited at 160 • C show magnetic properties specific to II-VI dilute magnetic semiconductors with localized spins S = 3/2 coupled by strong but short-range antiferromagnetic interactions resulting in low-temperature spin-glass freezing for x = 0.16 and 0.4. At higher growth temperature (200 • C) metallic Co nanocrystals precipitate in two locations giving rise to two different magnetic responses: (i) a superparamagnetic contribution coming from volume disperse nanocrystals; (ii) a ferromagneticlike behavior brought about by nanocrystals residing at the (Zn,Co)O/substrate interface. It is shown that the dipolar coupling within the interfacial two-dimensional dense dispersion of nanocrystals is responsible for the ferromagneticlike behavior.

Journal of Materials Science, 2014

Aluminum-doped zinc magnesium oxide (Zn 1-x

Journal of Electron Spectroscopy and Related Phenomena, 2011

Hard X-ray photoemission UPd3 UGe2 USb2 a b s t r a c t Electronic structure of single crystal UP... more Hard X-ray photoemission UPd3 UGe2 USb2 a b s t r a c t Electronic structure of single crystal UPd 3 , UGe 2 , and USb 2 has been measured from hard X-ray photoelectron spectroscopy (HAXPES) with 7.6 keV photons at the European Synchrotron Radiation Facility (ESRF). Lower photon energy angle-resolved photoelectron spectroscopy (ARPES) was also performed at the Synchrotron Radiation Center (SRC). Herein the following results are presented: (i) ARPES results demonstrate hybridization between the U 5f and Pd 4d electrons within UPd 3 . (ii) The greatly reduced surface sensitivity of HAXPES enabled observation of the bulk core levels in spite of surface oxidation. Photoelectron mean-free-path versus oxide layer thickness considerations were used to model the effectiveness of HAXPES for probing bulk features of in-air cleaved samples. (iii) Two distinct features separated by 800 meV were observed for the Sb 3d core level. These two features are attributed to manifestations of two distinct Sb sites within the USb 2 single crystal as supported by consideration of interatomic distances and enthalpy-of-formation. (iv) Doniach-Sunjic line shape analysis of core level spectral features revealed correlations between asymmetry coefficients and 5f localization.

Physical Review Letters, 2004

Our electron photoemission experiments demonstrate that the magnetization of the ferromagnetic st... more Our electron photoemission experiments demonstrate that the magnetization of the ferromagnetic state of UTe is proportional to the binding energy of the hybridized band centered around 50 meV below E F . This proportionality is direct evidence that the ferromagnetism of UTe is itinerant; i.e., the 5f electrons are not fully localized close to the atomic core. This mechanism of itinerant ferromagnetism differs from the traditional picture for 5f-electron magnetism in an essential and a novel way. We propose a simple model for the observed proportionality between the temperature dependence of the magnetization and the binding energy of the hybridized band near E F . This model allows us to estimate the effective magnetic interaction and to identify signatures of itinerant ferromagnetism in other materials.

Materials Science and Engineering: B, 2011

ABSTRACT a b s t r a c t We investigated the aluminum distribution in aluminum-doped zinc oxide f... more ABSTRACT a b s t r a c t We investigated the aluminum distribution in aluminum-doped zinc oxide films grown by atomic layer deposition. Surface morphology, structure, composition and electrical properties of obtained films were studied. For the aluminum content less than 2 at.%, a periodicity of Al distribution along the layer depth was observed. This periodicity diminished significantly after annealing the samples in nitrogen atmo-sphere at 300 • C. For the Al content higher than 2 at.%, its distribution in ZnO:Al films was uniform within the depth measurement accuracy of ∼5–10 nm.

Many-body interactions may result in the formation of long- lived heavy quasi-particles that exhi... more Many-body interactions may result in the formation of long- lived heavy quasi-particles that exhibit kinks in their energy dispersion. Kinks are often seen in d-electron correlated systems and are attributed to many different origins, such as coupling to phonons, extended spin-fluctuations, or electron- electron correlations. We have found that the renormalization of a 5f electron band in USb2 leads to

In recent years, the concept of 5f electron duality started to play important role in our underst... more In recent years, the concept of 5f electron duality started to play important role in our understaning of the electronic structure of actinides. With respect to the photoemission spectra, duality may be seen through the existence of two distinct regions in the valence band. First region, usually in the form of one narrow peak, is located near the Fermi level and represents the itinerant part of the spectral function. Second region, comprising a broad peak of major spectral weight is located a few eV below the Fermi level and corresponds to the more localized part of 5f response. The role of 5f duality in establishing electronic structure will be discussed. Aspects of the relevant final-state effects will also be shown.

2012 IEEE International Conference on Oxide Materials for Electronic Engineering (OMEE), 2012

A series of (ZnO)m(CoO)n digital alloys (m = 2, 8, n = 1) and superlattices (m = 80, n = 5, 10) g... more A series of (ZnO)m(CoO)n digital alloys (m = 2, 8, n = 1) and superlattices (m = 80, n = 5, 10) grown by atomic layer deposition has been investigated by a range of experimental methods. The data provide evidences that the Co interdiffusion in the digital alloy structures is sufficiently efficient to produce truly random Zn1−xCoxO mixed crystals with x up to 40%. Conversely, in the superlattice structures the interdiffusion is not strong enough to homogenize the Co content along the growth direction results in the formation of (Zn,Co)O films with spatially modulated Co concentrations. All structures deposited at 160 o C show magnetic properties specific to dilute magnetic semiconductors with localized spins S = 3/2 coupled by strong but short range antiferromagnetic interactions that lead to low temperature spin-glass freezing.

Radiation Physics and Chemistry, 2011

We present results of a resonant photoemission study of (Zn,Co)O films with Co content between 2%... more We present results of a resonant photoemission study of (Zn,Co)O films with Co content between 2% and 7%. The films were grown by Atomic Layer Deposition (ALD) at low temperature of 160 1C, and show fully paramagnetic behavior. The Co ions are uniformly distributed in the ZnO matrix and are free of foreign phases and metal accumulations as indicated by TEM data. The electronic structure of (Zn,Co)O films was studied by Resonant Photoemission Spectroscopy across the Co3p-Co3d photoionization threshold. We have observed that the resonant enhancement of the photoemission intensity from the Co3d shell is not the same for samples with different cobalt content. We suggest that the Co3d contribution to the valence band depends on both Co and H content.

MRS Proceedings, 2005

ABSTRACT The electronic structure of Pu materials is examined using photoelectron spectroscopy. F... more ABSTRACT The electronic structure of Pu materials is examined using photoelectron spectroscopy. For delta-phase Pu metal as well as PuCoGa5 and PuIn3, the 5f electrons appear to be at the threshold between localized and itinerant character. A mixed level model computational scheme is used which results in non-magnetic solutions for the electronic structure and agrees well with the photoemission measurements. Several other computational schemes are assessed against photoemission results for delta Pu. Additional insight is provided by O2 and H2 dosing of the delta Pu samples and consideration of surface effects. The experimental and computational results are consistent with the 5f electrons in Pu materials exhibiting a dual nature with some fraction of the 5f levels localized and not participating in the bonding while the other fraction of 5f character is involved in bonding and hybridization with the conduction electrons.

Physical review letters, Jan 24, 2003

The electronic structure of the first Pu-based superconductor PuCoGa5 is explored using photoelec... more The electronic structure of the first Pu-based superconductor PuCoGa5 is explored using photoelectron spectroscopy and a novel theoretical scheme. Exceptional agreement between calculation and experiment defines a path forward for understanding the electronic structure aspects of Pu-based materials. The photoemission results show two separate regions of 5f electron spectral intensity, one at the Fermi energy and another centered 1.2 eV below the Fermi level. The results for PuCoGa5 clearly indicate 5f electron behavior on the threshold between localized and itinerant. Comparisons to delta phase Pu metal show a broader framework for understanding the fundamental electronic properties of the Pu 5f levels in general within two configurations, one localized and one itinerant.

Semiconductor Science and Technology

Stable silver Schottky contacts are formed on nitrogen-doped thin ZnO films grown by the atomic l... more Stable silver Schottky contacts are formed on nitrogen-doped thin ZnO films grown by the atomic layer deposition technique. The IV characteristics show the rectification ratio of about 4 and the leakage current of about 10−3 A cm−2 in as-grown samples. The electrical properties of the Schottky diodes can be significantly improved by annealing the samples in oxygen or nitrogen atmosphere at 400 °C. We correlate this observation with the reduction of free carrier concentration in thin ZnO films after the heat treatment. We rule out that hydrogen at the bond-centred lattice site or hydrogen bond in an oxygen vacancy are dominant donors in our samples. Our findings confirm the model where the vacancy of oxygen acts as a dominant donor in nitrogen-doped as-grown samples. From DLTS measurements three deep levels (E130, E220 and E305) are present in the samples annealed in oxygen atmosphere. We assign E130 to an extended defect, whereas E220 and E305 are tentatively attributed to an impuri...

Thin Solid Films, 2012

ABSTRACT In this paper, we report on transparent transistor obtained using laminar structure of t... more ABSTRACT In this paper, we report on transparent transistor obtained using laminar structure of two high-k dielectric oxides (hafnium dioxide, HfO2 and aluminum oxide, Al2O3) and zinc oxide (ZnO) layer grown at low temperature (60 °C–100 °C) using Atomic Layer Deposition (ALD) technology. Our research was focused on the optimization of technological parameters for composite layers Al2O3/HfO2/Al2O3 for thin film transistor structures with ZnO as a channel and a gate layer. We elaborate on the ALD growth of these oxides, finding that the 100 nm thick layers of HfO2 and Al2O3 exhibit fine surface flatness and required amorphous microstructure. Growth parameters are optimized for the monolayer growth mode and maximum smoothness required for gating.