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1

Structure and Charge Compensation of Heteropolar SiC/GaN Interfaces

100%

Sznajder M., Majewski J.

Acta Physica Polonica A

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2013

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vol. 124

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issue 5

772-774

EN

We present studies of the morphology and charge distribution at the 4H-SiC/wz-GaN heteropolar junctions. Our investigations are based on the first principles calculations in the framework of the density functional theory where the interfaces between the SiC substrate and GaN layers are represented by means of a slab. These studies reveal possible charge compensation patterns at the interfaces that lead to charge redistribution from monopole to dipole character and increase the stability of the junctions. It turns out that the interfaces with C-Ga and Si-Ga bonds across the junction and reconstructions involving substitution of group IV elements into Ga layer are the most favorable energetically.

2

Ab Initio Studies of Al and Ga Adsorption on 4H-SiC{0001} Surfaces

100%

Wachowicz E., Sznajder M., Majewski J.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1045-1048

EN

Changes in the atomic and electronic structure of Si- and C-terminated 4H-SiC{0001} surfaces resulting from aluminium and gallium adsorption have been studied within density functional theory framework. Al and Ga coverages ranging from a submonolayer to one monolayer were considered. Our results show that Al binds more strongly to both surfaces than Ga. The binding is stronger to the C-terminated surface for both metals. The sites occupied by Al and Ga atoms at 1 monolayer are different and it is due to a different charge transfer from metal to the substrate.

3

Variable Temperature STM/STS Investigations of Ag Nanoparticles Growth on Semiconductor Surfaces

100%

Suto S., Czajka R., Szuba S., Shiwa A., Winiarz S., Nagashima H., Kato H., Yamada T., Kasuya A.

Acta Physica Polonica A

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2003

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vol. 104

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issue 3-4

289-302

EN

We have investigated the growth of Ag nanoparticles deposited on Si(111), H/Si(111)-(1×1) and Bi_2Te_3 substrates using a variable temperature scanning tunneling microscopy. These substrates are different as regards the model system for cluster and islands growth at the nanometer scale. Ag was evaporated onto the sample mounted at the scanning tunneling microscopy stage in vacuum of 10^{-10} Torr range during evaporation. The substrates were kept at different temperatures: -150˚C, room temperature, and 300˚C during the deposition process. In general, we have observed 3D growth mode up to several ML coverage. The density of clusters and their size were functions of the substrate's temperature during the deposition process - a higher density and a smaller size at -150˚C were in opposition to the 300˚C results - a lower density and a larger size. Low temperature depositions led to continuous layers above 10 ML coverage but the surface was covered by small Ag clusters of 1-2 nm in heights and 2-3 nm in diameters. The log-log graphs of height and projected diameter of Ag clusters revealed different slopes indicating different growth mechanisms at low and high temperatures. We obtained the value of n=0.25±0.02, typical of the so-called droplet model of cluster growth, only at 300˚C. Scanning tunneling spectroscopy measurements revealed clearly different I-V (and dI/dV vs. bias voltage) curves measured above clusters and directly above the substrate. In discussion, we compared our results to theoretically calculated density of states from other papers, finding conformity for partial density of states.

4

STM/STS Investigations of Surface Evolution of Si(111)-(7×7) Induced with Nickel

100%

Gutek J., Szuba S., Czajka R.

Acta Physica Polonica A

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2003

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vol. 104

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issue 3-4

345-350

EN

By means of scanning tunneling microscopy and spectroscopy we studied the surface evolution of Si(111)-(7×7) induced with nickel followed by annealing at specified temperatures (400, 600, and 800˚C). Nickel evaporation resulted with 0.05 ML and 0.2 ML coverage was carried out at room temperature with the use of solid phase epitaxy. The characteristic phase formations occurred after gradual annealing the sample depending on the amount of deposited material. At very low coverages scanning tunneling microscopy observation showed two types of ring clusters (1×1 -RC and clusters of the √(19)×√(19) reconstruction) accompanied by the Si(111)-(7×7) surface reconstruction. All above-mentioned phases appeared in that order as the annealing temperature increased. Deposition of about 0.2 ML of Ni followed by annealing at 600˚C formed extended regions of 1×1 nickel silicide reconstruction. Very clear, extended regions of √(19)×√(19) reconstruction appeared when annealed to 800˚C. The electronic properties of observed structures have been studied by the scanning tunneling spectroscopy. Spectroscopy curves measured above certain surface formations revealed the presence of the Si rest atom, NiSi, and NiSi_2 local density of electronic states.

5

Ru/GaN(0001) Interface Properties

100%

Wasielewski R., Grodzicki M., Sito J., Lament K., Mazur P., Ciszewski A.

Acta Physica Polonica A

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2017

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vol. 132

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issue 2

354-357

EN

We report the results of our studies of ruthenium layer structures adsorbed on GaN(0001). Ruthenium was evaporated at room temperature under ultrahigh vacuum conditions onto n-type GaN substrates epitaxially grown on sapphire. While X-ray photoelectron spectroscopy confirmed the presence of Ru bonds in the deposited adlayers, the ultraviolet photoelectron spectroscopy show a peak at the Fermi level as well as lines originating from ruthenium. The height of the Schottky barrier was calculated based on the data measured by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy and amounts to 1.5 eV.

6

Modification of Electronic Structure of n-GaN(0001) Surface by N⁺-Ion Bombardment

100%

Grodzicki M., Mazur P., Ciszewski A.

Acta Physica Polonica A

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2017

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vol. 132

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issue 2

351-353

EN

The electronic structure of n-type GaN(0001) surface and its modification by N⁺ ion bombardment are presented in this report. The studies were carried out in situ in ultrahigh vacuum by ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and low-energy electron diffraction. Low-energy N⁺ ion bombardment, which was done using an ion gun at an energy of 200 eV, leads to nitriding of the surface. The process changes the surface stoichiometry and, consequently, provides formation of a disordered altered GaN layer. The calculated electron affinity of the clean n-GaN surface of 3.4 eV and band bending of 0.2 eV became changed after bombardment to 2.9 eV and 0.8 eV, respectively. The obtained difference in valence band maximum between the clean sample and the bombarded one was 0.6 eV.

7

Substrates Grown from the Vapor for ZnO Homoepitaxy

75%

Skupiński P., Kopalko K., Łusakowska E., Domukhovski V., Jakieła R., Mycielski A., Grasza K.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1361-1368

EN

The novel method of preparation of epi-ready ZnO substrates is demonstrated. The substrates were made of unique ZnO crystals grown by chemical vapor transport method using hydrogen as the transport agent. The effect of low-level doping (Mn, Co, Cu, and V) on the structural quality of the crystals was investigated. Atomic layer deposition was used to verify usability of the substrates for homoepitaxy. The thermal annealing prior to the atomic layer deposition process and effect of thermal annealing of the epitaxial layers was studied. The X-ray diffraction and atomic force microscopy methods were applied to study the structural quality of the ZnO layers. Detection of the dopants in the substrates by secondary ion mass spectroscopy made possible the measurement of the thickness of the layers. The obtained root mean square roughness for both the substrates and layers ranged between 0.2 nm and 5 nm, and was dependent on the sample crystallographic orientation and sequence of polishing and annealing procedures. The optimal recipe for the epi-ready substrate preparation was formulated.

8

Ge diffusion on Si surfaces

63%

Dolbak A., Olshanetsky B.

Open Physics

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2006

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vol. 4

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issue 3

310-317

EN

Ge diffusion on Si(100), (111), and (110) surfaces has been studied by Auger electron spectroscopy and low energy electron diffraction in the temperature range from 600 to 800 °C. Surface diffusion coefficients versus temperature have been measured.

9

Interval Identification of FMR Parameters for Spin Reorientation Transition in (Ga,Mn)As

63%

Gutowski M., Stefanowicz W., Proselkov O., Sawicki M., Żuberek R., Sadowski J.

Acta Physica Polonica A

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2012

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vol. 121

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issue 5-6

1228-1230

EN

In this work we report results of ferromagnetic resonance studies of a 6% 15nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5 K and 120 K. We observe a temperature induced reorientation of the effective in-plane easy axis from [\overline{1}10] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H_{eff} (=4π M-H_{2⊥}), H_{2∥}, and H_{4∥}. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In "fitting" mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.

Refine search results

Structure and Charge Compensation of Heteropolar SiC/GaN Interfaces

Ab Initio Studies of Al and Ga Adsorption on 4H-SiC{0001} Surfaces

Variable Temperature STM/STS Investigations of Ag Nanoparticles Growth on Semiconductor Surfaces

STM/STS Investigations of Surface Evolution of Si(111)-(7×7) Induced with Nickel

Ru/GaN(0001) Interface Properties

Modification of Electronic Structure of n-GaN(0001) Surface by N⁺-Ion Bombardment

Substrates Grown from the Vapor for ZnO Homoepitaxy

Ge diffusion on Si surfaces

Interval Identification of FMR Parameters for Spin Reorientation Transition in (Ga,Mn)As