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1

Morphological Changes and Enhancement of Ultraviolet Emission by Subsequent Thermal Treatment of Ga-Doped ZnO Nanostructures

100%

Manzoor U.

Acta Physica Polonica A

|

2015

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vol. 127

|

issue 4

910-913

EN

ZnO nanostructures doped with a high concentration of Gallium (Ga) were synthesized on a Si substrate by thermal evaporation. Subsequent heat treatments of selected nanostructures was done at 600°C, 700°C, 800°C and 900°C. Scanning electron microscope (SEM), X-Ray diffraction (XRD) and photoluminance (PL) studies was performed after every heat treatment. Systematic scanning electron microscope (SEM) studies suggest significant sublimation at 800°C. XRD results show that crystal quality was improved by annealing and phase separation may occur after high temperatures annealing. Ultraviolet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with heat treatment.

2

Surface Morphology, Structural and Optical Properties of MgO Films Obtained by Spray Pyrolysis Technique

100%

Diachenko O., Opanasuyk A., Kurbatov D., Opanasuyk N., Kononov O., Nam D., Cheong H.

Acta Physica Polonica A

|

2016

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vol. 130

|

issue 3

805-810

EN

X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, UV-visible photometry, and photoluminescence measurements were used to investigate the surface morphology and structural and optical properties of MgO films. Magnesium oxide films deposited by the spray pyrolysis technique were studied. The substrate temperature was varied from T_{s} = 643 K to 693 K. Magnesium chloride hexahydrate (MgCl₂·6H₂O), dissolved in deionized water, was used as the precursor solution. It was established that the single phase films crystallize into a cubic structure with very fine crystallite size (about 2 nm). The optical band gaps of the samples were varied from 3.64 eV to 3.70 eV. Also, the films have a high level of transmittance of 90%. Photoluminescence spectra show the emission peaks at approximately 412 nm (3.00 eV) and 524 nm (2.38 eV). The peak with the energy of 3.00 eV is ascribed to holes trapped in magnesium ion vacancies acting as acceptors (F⁺ center). The broad emission peak at 524 nm is related to the presence of defects (F¯ centers) associated with oxygen ion vacancies.

3

Solubility and Segregation of Co in CdTe-Based Ternary and Quaternary Alloys

100%

Miotkowska S., Dynowska E., Miotkowski I., Alawadhi H., Lewicki A., Metcalf P., Ramdas A.

Acta Physica Polonica A

|

2002

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vol. 101

|

issue 5

735-742

EN

Single crystals of Cd_{1-x}Co_xTe and Cd_{1-x-y}Co_xMn_yTe are characterized with X-ray powder diffraction and electron microprobe to establish compositional dependence of the lattice parameters and deduce Co solubility limit. The experimental compositional profiles are examined on specimens taken from various locations of ingots along their longitudinal axes and compared with normal freezing distributions. The values of Co segregation coefficient are analyzed for both ternary and quaternary alloys in terms of normal freezing mode.

4

Raman Characterisation of Cd_{1-x}Zn_x Te Thick Polycrystalline Films Obtained by the Close-Spaced Sublimation

100%

Znamenshchykov Y., Kosyak V., Opanasyuk A., Dorda V., Fochuk P., Medvids A.

Acta Physica Polonica A

|

2017

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vol. 132

|

issue 4

1430-1435

EN

In this work, we studied the Raman spectra of thick polycrystalline Cd_{1-x}Zn_x Te (CZT) films with x ranged from 0.06 to 0.68. Additionally, the surface morphology and structural properties were studied in order to determine the crystalline quality of the samples. The Raman spectra had a two-mode behavior typical for CZT solid solution and showed CdTe- and ZnTe-like longitudinal and transverse optical modes. The relationship between the frequencies of CdTe- and ZnTe-related modes on x was studied. We observed the deviation of the compositional dependence of phonon mode frequencies for polycrystalline CZT films in comparison with a similar dependence for CZT single crystals. Such deviation was caused by the effect of structural defects in polycrystalline films on frequencies of vibrational modes. The values of excitation wavelength, which allow achieving of high signal-to-noise ratio on the Raman spectra of CZT films with different zinc concentration in the result of resonant enhancement of phonon modes intensities, were experimentally determined.

5

PVT-Grown Single Crystals of Cd_{1-x}Zn_{x}Te (x ≤ 0.25) and ZnTe as Substrates for Epitaxy

100%

Mycielski A., Szadkowski A., Łusakowska E., Kowalczyk L., Domagała J., Bąk-Misiuk J., Wilamowski Z., Witkowska B.

Acta Physica Polonica A

|

1998

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vol. 94

|

issue 3

441-445

EN

The process of growth of single crystals of Cd_{1-x}Zn_{x}Te (x ≤ 0.25) and ZnTe by physical vapour transport has been optimized and the twin-free single crystals with a very good crystal structure and low density of dislocations are grown as substrates for MBE and other techniques of epitaxy. Characterization of the crystals is described.

6

Effect of Substrate Temperature on the Structural and Optical Properties of Nanocrystalline Cadmium Selenide Thin Films Prepared by Electron Beam Evaporation Technique

100%

Suthan Kissinger N., Suthagar J., Saravana Kumar B., Balasubramaniam T., Perumal K.

Acta Physica Polonica A

|

2010

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vol. 118

|

issue 4

623-628

EN

Cadmium selenide (CdSe) thin films on glass substrates were prepared by physical vapour deposition under vacuum using the electron beam evaporated technique for different substrate temperatures: room temperature, 100, 200, 300°C, respectively. X-ray diffraction analysis indicates that the films are polycrystalline, having hexagonal (wurtzite) structure irrespective of their substrate temperature. All the films show most preferred orientation along (0 0 2) plane parallel to the substrates. The microstructural parameters such as particle size, stress, strain and dislocation density were calculated. The grain size of deposited CdSe films is small and is within the range of 18 to 42 nm. The optical absorption spectra of electrom beam deposited CdSe films were studied in the wavelength region of 250-2500 nm. The energy gap (E_{g}) values (allowed direct transitions), calculated from the absorption spectra, ranged between 1.77 and 1.92 eV. The surface morphological quality of electron beam evaporated CdSe films were analyzed by scanning electron microscopy and atomic force microscopy.

7

Mechanochemistry of Solids: New Prospects for Extractive Metallurgy, Materials Science and Medicine

80%

Baláž P., Baláž M., Achimovičová M., Bujňáková Z., Dutková E.

Acta Physica Polonica A

|

2014

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vol. 126

|

issue 4

879-883

EN

In this review paper recent advances in chalcogene mechanochemistry are described. Three selected areas are being covered, i.e. metallurgy, materials science, and medicine. In extractive metallurgy, the processing of copper arsenic mineral enargite (Cu_3AsS_4) with the aim of its dearsenification and subsequent preparation of a new anticancer drug (Na_3AsS_4) and of copper in nanocrystalline state ( ≈ 20 nm) illustrate the non-traditional prospect of ore treatment. In material science, the new nanocrystalline semiconductors were synthesized mechanochemically, e.g. selenides of zinc and lead (ZnSe, PbSe) and bismuth sulphide (Bi_2S_3). Metal and chalcogene were applied as reaction precursors. In some cases, the amino acids (cystine, cysteine) were applied as sulphur precursor, in order to provide reactive sites on synthesized solid (PbS) for bioconjugation and to prevent agglomeration. The concept of nanomilling is described as a way to prepare effective substances for cancer treatment in medicine. In vitro activity of realgar (As_4S_4) as an example is described. In all three areas the focus is aimed also on industrial applications where suitable large-scale mills are described. The described examples represent the contemporary aim of mechanochemists - to prepare substances with the desired properties in a reproducible way under easy-operating, environmentally friendly and essentially waste-free conditions.

8

Electrical Characterization of Defects in Schottky Au-CdTe:Ga Diodes

80%

Dyba P., Płaczek-Popko E., Zielony E., Gumienny Z., Szatkowski J.

Acta Physica Polonica A

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2009

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vol. 116

|

issue 5

944-946

EN

Deep electron states in gallium doped CdTe have been studied by deep-level transient spectroscopy method. The Schottky Au-CdTe diodes were processed to perform the investigations. Rectifying properties of diodes have been examined by the room temperature current-voltage and capacitance-voltage measurements. Deep-level transient spectroscopy measurements performed in the range of temperatures 77-350 K yield the presence of three electron traps. The thermal activation energies and apparent capture cross-sections have been determined from related Arrhenius plots. The dominant trap of activation energy E_2 = 0.33 eV and capture cross-section σ_2 = 3 × 10^{-15} cm^2 has been assigned to the gallium related DX center present in the CdTe material.

9

Properties of ZnO and ZnMnO Thin Films Obtained by Pulsed Laser Ablation

80%

Virt I., Hadzaman I., Bilyk I., Rudyi I., Kurilo I., Frugynskyi M., Potera P.

Acta Physica Polonica A

|

2010

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vol. 117

|

issue 1

34-37

EN

The results of experimental investigation of structural and physical properties of ZnO and ZnMnO films are presented in this work. The films of ZnO and Zn_{1-x}Mn_{x}O of different thickness were obtained on Al_{2}O_{3}, glass, and KCl substrates in vacuum of 1 × 10^{-5} Torr by the pulsed laser deposition method. The samples were obtained under the substrate temperature 300-473 K. A thickness of films was in the range of 0.5-1 μm depending on the number of laser pulses. The structure of target bulk materials was investigated by X-ray diffraction method. A structure of laser deposited films was investigated by the transmission high-energy electron diffraction method. Electric resistivity was measured in the temperature range 77-450 K. The presence of two activation energies in the temperature range 300-330 K and 330-450 K is followed from the analysis of the films electrical resistivity. These activation energies correspond to two deep donor's energy levels. The shallow donor's level is connected with manganese presence. Optical transmission of ZnO and ZnMnO films deposited at various temperatures were investigated.

10

Model and Properties of Fullerene-Like and Wurtzite-Like ZnO and Zn(Cd)O Clusters

80%

Ovsiannikova L.

Acta Physica Polonica A

|

2012

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vol. 122

|

issue 6

1062-1064

EN

The electronic structure of the ground state of fullerene-like and wurtzite-like Zn_{n}O_{n} and Zn_{n - x}Cd_{x}O_{n} clusters has been investigated by computer physics methods. A relative evaluation of the stability and band gap width of clusters depending on the number of atoms in the cluster and its geometry has been performed. The model of a fullerene-like (ZnO)_{60} particle with a mixed sp^3/sp^2 type of bonds has been constructed. A (ZnO)_{12} cluster of T_{h} symmetry was taken as a base of the model. Within the framework of the B3LYP electron density hybrid functional method with a set of 3-21G(d) split valence basis functions, a numerical investigation of the influence of the incorporation of cadmium (33%) into the ZnO matrix on the electronic structure and the band gap width has been performed.

11

Epitaxial ZnO Films Grown at Low Temperature for Novel Electronic Application

80%

Wachnicki Ł., Dużyńska A., Domagala J., Witkowski B., Krajewski T., Przeździecka E., Guziewicz M., Wierzbicka A., Kopalko K., Figge S., Hommel D., Godlewski M., Guziewicz E.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 6A

A-7-A-10

EN

Monocrystalline films of zinc oxide were grown at 300C by atomic layer deposition. ZnO layers were grown on various substrates like ZnO bulk crystal, GaN, SiC and Al_2O_3. Electrical properties of the films depend on structural quality. Structural quality, surface morphology and optical properties of ZnO films were characterized using X-ray diffraction, scanning electron microscopy, and photoluminescence, respectively. High resolution X-ray diffraction spectra show that the rocking curve FWHM of the symmetrical 00.2 reflection equals to 0.058° and 0.009° for ZnO deposited on a gallium nitride template and a zinc oxide substrate, respectively. In low temperature photoluminescence sharp excitonic lines in the band-edge region with a FWHM equal to 4 meV, 5 meV and 6 meV, for zinc oxide deposited on gallium nitride, zinc oxide and sapphire substrate, respectively.

12

Influence of Thermal Process on Physical Properties of ZnO Films Prepared by Spray Pyrolysis

80%

Gencyilmaz O., Atay F., Akyuz I.

Acta Physica Polonica A

|

2014

|

vol. 126

|

issue 6

1331-1337

EN

ZnO films were deposited on glass substrates by ultrasonic spray pyrolysis technique at a substrate temperature of 300 ± 5°C. All of the films have been annealed at 500°C temperature for different time (1, 2, and 3 h) to improve the optical, electrical and surface properties. The effect of annealing time on the films of physical properties has been investigated. UV-Vis spectrophotometer has been used for transmittance measurements. Also, band gap values of the films have been determined by optical method. Atomic force microscopy has been used to have information the surface morphology and roughness values of the films. Thicknesses, refractive index and extinction coefficient values of the films have been determined by spectroscopic ellipsometry technique. The electrical conduction mechanisms and resistivity of the films were investigated using two probe technique. After all the investigations it was concluded that annealing time has a dramatic effect especially on the surface, optical properties and electrical resistivity values of ZnO films. From the results of these investigations, the application potential of the films for solar cell devices as transparent electrode was searched.

13

Properties of GaN Nanocolumns Grown by Plasma - Assisted MBE on Si (111) Substrates

80%

Zytkiewicz Z., Dluzewski P., Borysiuk J., Sobanska M., Klosek K., Witkowski B., Setkiewicz M., Pustelny T.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 6A

A-15-A-16

EN

We report on growth of GaN nanocolumns by plasma assisted MBE on (111) silicon substrates and on their characterization. The nanocolumns nucleate on the substrate spontaneously without use of any catalyst, probably by the Volmer-Weber mechanism. Transmission electron microscopy analysis shows high crystalline quality of GaN nanocolumns and their good alignment with the c-axis being perpendicular to the substrate. Preliminary results on use of GaN nanocolumns in gas sensor devices are presented.

14

Impedance Spectroscopy of Au-CdTe:Ga Schottky Contacts

80%

Płaczek-Popko E., Trzmiel J., Gumienny Z., Wojtyna E., Szatkowski J.

Acta Physica Polonica A

|

2008

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vol. 114

|

issue 5

1279-1283

EN

The dielectric response of Au-CdTe gallium doped Schottky contacts was investigated by impedance spectroscopy in the frequency range from 0.2 Hz to 3 MHz, at temperatures in the range from 77 K to 300 K. Combined modulus and impedance spectroscopic plots were analyzed to study the response of the structure. The data were fitted with the simple RC circuit composed of a depletion layer capacitance in parallel with resistance and a series resistance of the bulk CdTe:Ga. The activation energy of the bulk trap obtained from the Arrhenius plot of the resistance was found to be equal to 0.08 eV, close to the value 0.09 eV obtained from the impedance-modulus spectroscopy. The trap dominant in CdTe:Ga is possibly the DX center related, as it has been observed that this is the dominant trap in the material.

15

Synchrotron Photoemission Study of Ferromagnetic (Zn,Co)O Films

80%

Guziewicz E., Lukasiewicz M., Wachnicki L., Kopalko K., Dłużewski P., Jakiela R., Godlewski M.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 6A

A-40-A-42

EN

The electronic structure of ferromagnetic (Zn,Co)O films was investigated by resonant photoemission across the Co 3p → Co 3d photoionization threshold, e.g. using photon energy between 50 eV and 66 eV. The films were grown by atomic layer deposition at temperature between 160C and 300C and they differed in distribution and content of cobalt. The maximum of the Fano resonance was observed at photon energy 63 eV, whereas the minimum at 58 eV. The difference between energy distribution curves taken at 63 eV and the one taken at 58 eV was calculated for a series of samples. It shows that the Co 3d contribution to the valence band electronic structure of ferromagnetic (Zn,Co)O films differs significantly from that of the films which show the paramagnetic response.

16

Application of GaN Pressure Grown Crystals for Epitaxy of GaN-Based Structures

80%

Grzegory I.

Acta Physica Polonica A

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2000

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vol. 98

|

issue 3

183-193

EN

The results obtained with the use of the pressure grown GaN single crystalline substrates allow to draw the following conclusions important for the construction of In-free UV light emitting diodes and lasers and InGaN-based high power blue lasers: 1. The application of the pressure grown GaN single crystalline substrates allows to grow near dislocation free layer structures by both metal organic chemical vapor deposition and MBE. 2. The elimination of dislocations leads to highly efficient UV emission from GaN and GaN/AlGaN quantum wells which is impossible for strongly dislocated structures grown on sapphire. 3. At high excitations (i.e. in lasers) dislocations are effective nonradiative recombination centers also in the InGaN containing structures, therefore the elimination of these defects is crucial for better performance of blue lasers. 4. The analysis of microstructural and optical properties of the InGaN containing dislocation free structures shows that the main mechanisms of carrier localization in InGaN are not related with the nm scale compositional fluctuations in InGaN. In the paper, the optical and structural properties of the near dislocation free GaN-based structures leading to the above conclusions are discussed.

17

Physical Properties of ZnCoO Tetrapods and Nanofibers

80%

Gas K., Fronc K., Dziawa P., Knoff W., Wojciechowski T., Zaleszczyk W., Baranowska-Korczyc A., Morhange J., Paszkowicz W., Elbaum D., Karczewski G., Wojtowicz T., Szuszkiewicz W.

Acta Physica Polonica A

|

2009

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vol. 116

|

issue 5

868-870

EN

In this paper the physical properties of two types of Co-doped ZnO nanostructures: tetrapods and nanofibers grown by a rapid thermal evaporation process and prepared by the electrospinning technique, respectively, were investigated and analyzed. Surface morphology of the samples was examined using scanning electron microscopy. X-ray diffraction measurements showed hexagonal wurtzite crystal structure of both types of investigated nanostructures. Both X-ray diffraction and Raman scattering data confirmed high phase purity of the samples. The magnetic properties studied with the use of the SQUID magnetometer confirmed a presence of ferromagnetic order in analyzed nanostructures. The observed photoluminescence spectra exhibited two groups of lines. The first one, in the ultraviolet spectral range, is due to the optical transitions close to ZnO band gap, the second one in the red region is most probably related to the Co^{2+} d-d internal transitions. The influence of native defects on the optical properties is also shown and discussed. All results reported here lead us to the conclusion that in the mixed crystal nanostructures obtained, a fraction of the Zn^{2+} ions is substituted by Co^{2+} ions.

18

Photoluminescence Properties of ZnO Nanowires Grown on Ni Substrate

80%

Zaleszczyk W., Fronc K., Przeździecka E., Janik E., Czapkiewicz M., Wróbel J., Paszkowicz W., Kłopotowski Ł., Karczewski G., Wojtowicz T., Presz A.

Acta Physica Polonica A

|

2008

|

vol. 114

|

issue 5

1451-1456

EN

Photoluminescence studies of zinc oxide nanowires produced by a carbo-thermal method on a nickel foil substrate are reported. Two types of as-grown samples: the first - containing only buffer film, and the second - containing both zinc oxide nanowires and buffer film grown in the same technological process, were investigated by means of the temperature-dependent photoluminescence. X-ray diffraction measurements of buffer film show that it is polycrystalline and is composed from wurtzite-type ZnO (main phase) and includes minority phases: rock salt type (Ni,Zn)O and hexagonal C₃N₄. The shape of the apparently monocrystalline nanowires is characterized by hexagonal section matching with the expectations of the hexagonal ZnO structure. The presence of LO-phonon replicas in photoluminescence spectra for the second sample is used as an argument for confirmation that ZnO nanowires are single crystalline. The method of growth of ZnO nanowires on nickel oxide opens perspectives to produce Zn_{1-x}Ni_{x}O diluted magnetic semiconductor nanowires.

19

Realization of p-Type Conductivity in ZnO via Potassium Doping

80%

Bousmaha M., Bezzerrouk M., Baghdad R., Chebbah K., Kharroubi B., Bouhafs B.

Acta Physica Polonica A

|

2016

|

vol. 129

|

issue 6

1155-1158

EN

Our work focuses on the study of the electronic structure of undoped and K-doped ZnO using density functional theory as implemented in the Wien2k package. Generalized gradient approximation and GGA plus Tran-Blaha-modified Becke-Johnson (TB-mBJ) were used to calculate the exchange-correlation energy. From the electronic properties, ZnO has a direct band gap in (Γ-Γ) direction with a value of 0.76 eV within GGA and 2.63 eV within GGA + TB-mBJ. For the K-doped ZnO (12.5%) the gap was found to be 1.15 eV within GGA and 3.28 eV within GGA + TB-mBJ, we have observed that an emersion of a new narrow band exists in the valence band which is mainly caused by K 3p states with a little Zn 4s and Zn 3d effect.

20

Type I CdSe and CdMgSe Quantum Wells

80%

Rudniewski R., Rousset J., Janik E., Kossacki P., Golnik A., Nawrocki M., Pacuski W.

Acta Physica Polonica A

|

2014

|

vol. 126

|

issue 5

1167-1170

EN

In this work we present the band gap engineering, epitaxial growth and optical characterization of CdSe/Cd_{0.9}Mg_{0.1}Se and Cd_{0.9}Mg_{0.1}Se/Cd_{0.85}Mg_{0.15}Se quantum wells with a thickness ranging from 1 to 15 nm. These structures exhibit strong near-band-gap photoluminescence from helium up to room temperature. The emission energy is tuned in the range from 1.74 to 2.1 eV at 7 K, depending on the thickness and well composition. The most intense photoluminescence (both at 7 and 300 K) was observed for 10 nm thick CdSe/Cd_{0.9}Mg_{0.1}Se wells. Such a structure gives also a sharp emission line (FWHM = 20 meV) at low temperature. The presented quantum wells are well suited for being embedded in lattice matched ZnTe based microcavities.

Refine search results

Morphological Changes and Enhancement of Ultraviolet Emission by Subsequent Thermal Treatment of Ga-Doped ZnO Nanostructures

Surface Morphology, Structural and Optical Properties of MgO Films Obtained by Spray Pyrolysis Technique

Solubility and Segregation of Co in CdTe-Based Ternary and Quaternary Alloys

Raman Characterisation of Cd_{1-x}Zn_x Te Thick Polycrystalline Films Obtained by the Close-Spaced Sublimation

PVT-Grown Single Crystals of Cd_{1-x}Zn_{x}Te (x ≤ 0.25) and ZnTe as Substrates for Epitaxy

Effect of Substrate Temperature on the Structural and Optical Properties of Nanocrystalline Cadmium Selenide Thin Films Prepared by Electron Beam Evaporation Technique

Mechanochemistry of Solids: New Prospects for Extractive Metallurgy, Materials Science and Medicine

Electrical Characterization of Defects in Schottky Au-CdTe:Ga Diodes

Properties of ZnO and ZnMnO Thin Films Obtained by Pulsed Laser Ablation

Model and Properties of Fullerene-Like and Wurtzite-Like ZnO and Zn(Cd)O Clusters

Epitaxial ZnO Films Grown at Low Temperature for Novel Electronic Application

Influence of Thermal Process on Physical Properties of ZnO Films Prepared by Spray Pyrolysis

Properties of GaN Nanocolumns Grown by Plasma - Assisted MBE on Si (111) Substrates

Impedance Spectroscopy of Au-CdTe:Ga Schottky Contacts

Synchrotron Photoemission Study of Ferromagnetic (Zn,Co)O Films

Application of GaN Pressure Grown Crystals for Epitaxy of GaN-Based Structures

Physical Properties of ZnCoO Tetrapods and Nanofibers

Photoluminescence Properties of ZnO Nanowires Grown on Ni Substrate

Realization of p-Type Conductivity in ZnO via Potassium Doping

Type I CdSe and CdMgSe Quantum Wells