Electroactivity of Al in Al-Doped ZnO Films

The report devoted to study the influence of Al content on its electroactivity in ZnO thin films. Al-doped ZnO thin films were deposited by growth method on silicon substrates. The set of ZnO:Al films with concentrations of Al in the range from 0.2 to 1.2 % were grown. For samples characterization, XRD, EDX analysis, atomic force microscopy and transmittance measurements were used. The temperature dependences of electrical resistivity and Hall coefficient were investigated

Effect of electron irradiation on transparent conductive films ZnO:Al deposited at different sputtering power

Transparent conductive oxide thin films of Al-doped ZnO grown by rf magnetron sputtering were irradiated with high energy electrons with the energy 12.6 MeV and fluence 5·10¹⁴ e/cm². The films were produced using different sputtering powers. It has been shown that electron irradiation creates defects that lead to distortions of the crystal lattice, which results in reduced crystallinity of the films. Also, it leads to film heating that results in radiation annealing and relaxation of the lattice

Properties of ZnO:Mn Nanoparticles Immobilized in Polyethylene Matrix

ZnO:Mn nanoparticles (of 3—5 nm) immobilized in polyethylene matrix are synthesized. The samples with different content of the manganese (5%, 10%, and 20% of initial solution of Mn and Zn precursors) are investigated by means of ESR, PL, and XRD. Thus, the behaviour of the Mn impurities in ZnO is studied. As revealed, the most of the manganese in ZnO forms the second undetermined phase MnOx or substitute zinc in cation sublattice at the surface layer of the nanoparticles. The value of constant of hyperfine structure of Mn is higher than an expected one (|A| = 89.5⋅10−4 cm−1 that is significantly differ from the constant of hyperfine structure of Mn incorporated into ZnO single crystal (76⋅10−4 cm−1)). Photoluminescence measurements reveal wide band of emission in green—red region (500—600 nm), with different position of the maximum depending on the manganese content.Одержано наночастинки ZnO:Mn розмірами 3—5 нм. За допомогою метод ЕПР, рентґеноструктурної аналізи та фотолюмінесценції досліджувалася структура цих наночастинок з різним вмістом мангану: 5%, 10% та 20% масової частки по відношенню до вихідного розчину прекурсорів. Було показано, що переважна кількість мангану формує другу фазу та заміщує цинок у катіонній підґратниці в поверхневому прошарку цих наночастинок. Значення надтонкої структури в ЕПР-дослідженнях виявилися більшими за очікуване (|A| = 89,5⋅10−4 см−1, що значно відрізняється від довідникових даних константи надтонкої структури для мангану в кристалічній ґратниці ZnO – 76⋅10−4 см−1). Фотолюмінісцентні міряння виявили широку лінію випромінення в зелено-червоній області спектру 500—600 нм з різним положенням максимуму (залежно від типу зразка).Получены наночастицы Zno:Mn размерами 3—5 нм. С помощью методов ЭПР, рентгеноструктурного анализа и фотолюминесценции исследовалась структура этих наночастиц с разным содержимым марганца: 5%, 10% и 20% массовой части по отношению к исходному раствору прекурсоров. Было показано, что преобладающее количество марганца формирует вторую фазу и замещает цинк в катионной подрешетке в поверхностной прослойке этих наночастиц. Значение сверхтонкой структуры в ЭПР-исследованиях оказались больше ожидаемых (|A| = 89,5⋅10−4 см−1, что значительно отличается от справочных данных константы сверхтонкой структуры для марганца в кристаллической решетке ZnO – 76⋅10−4 см−1). Фотолюминесцентные измерения выявили широкую линию излучения в зелено-красной области спектра 500—600 нм с разным положением максимума (в зависимости от типа образца)

Properties of nanoparticles ZnO:Mn immobilized in polyethylene matrix

Nanoparticles ZnO:Mn (3–5nm) immobilized in polyethylene matrix were synthesized. The samples with different content of the manganese (5, 10 and 20%) in the initial solution of the Mn and Zn precursors were investigated by means of ESR, PL and XRD. Thus the behavior of the Mn impurities in ZnO was studied. It was observed that most of the manganese in ZnO form second undefined phase MnOx or substitute the zinc in cation sublattice at the surface layer of the nanoparticles. The mean value of constant of hyperfine structure of Mn is higher than expected one ( = (94±3)·10⁻⁴ cm⁻¹) that is significantly differ from the constant of hyperfine structure of Mn incorporated into single crystal ZnO (76·10⁻⁴ cm⁻¹). Photoluminescence measurements has revealed wide band of emission in green-red region 500–600 nm, with different position of the maximum depending on the manganese content.Отримано наночастинки ZnO:Mn розміром 3–5 нм. За допо-могою методів ЕПР, рентгеноструктурного аналізу та фотолюмінесценції досліджували структуру цих наночастинок із вмістом марганцю 5, 10 і 20% щодо вихідного розчину пре-курсорів. Показано, що переважна кількість марганцю формує другу фазу та заміщує цинк у катіонній підрешітці вповерхневому прошарку цих наночастинок. Середнє значення константи надтонкої структури ( = (94±3)·10⁻⁴ см⁻¹),отримане методом ЕПР, виявилося більшим за очікуване та відмінним від довідникового для марганцю в кристалічній решітці ZnO (76·10⁻⁴ см⁻¹). Фотолюмінесцентні вимірювання виявили широку лінію випромінювання в зелено-червоній області спектра 500–600 нм із різним положенням максимуму залежно від типу зразка.Получены наночастицы ZnO:Mn размером 3–5 нм. С помощью методов ЭПР, рентгеноструктурного анализа и фотолюминесценции исследовалась структура этих наночастиц с содержанием марганца 5, 10 и 20% относительноисходного раствора прекурсоров. Показано, что преимущественное количество марганца формирует вторую фазу и замещает цинк в катионной подрешетке в поверхностномслое этих наночастиц. Среднее значение константы сверхтонкой структуры ( = (94±3)·10⁻⁴ cm⁻¹), полученное методомЭПР, оказалось большим по сравнению с ожидаемым и отличным от справочного для марганца в кристаллической решетке ZnO (76·10⁻⁴ см⁻¹). Фотолюминесцентные измерения выявили широкую линию излучения в зелено-красной области спектра 500600 нм с разным положением максимума в зависимости от типа образца

Thermoelectric studies of electronic properties of ferromagnetic GaMnAs layers

Thermoelectric power, electrical conductivity, and high field Hall effect were studied over a broad temperature range in ferromagnetic Ga₁₋xMnxAs epitaxial layers (0.015 ≤ x ≤ 0.06). Thermoelectric power analysis gives information about carrier transport mechanisms in layers with both metallic and non-metallic types of conductivity and allows determination of the Fermi energy and carrier concentration. At high temperatures (T > 70 K), the thermoelectric power in GaMnAs linearly increases with increasing temperature. That indicates the presence of a degenerate hole gas with the Fermi energy EF = 220 ± 25 meV, nearly independent of Mn content (for 0.02 ≤ x ≤ 0.05). At lower temperatures, GaMnAs layers with metallic-type conductivity show an additional contribution to the thermoelectric power with the maximum close to the Curie temperature

Diluted magnetic layered semiconductor InSe:Mn with high Curie temperature

We present a detailed study of layered semiconductor InSe doped with Mn. Xray and neutron diffraction analyses of (In,Mn)Se single crystals show the presence of a main phase as In₁−xMnxSe solid solution, the second antiferromagnetic MnSe phase, and traces of In₄ Se₃ Magnetic measurements reveal ferromagnetic behavior of (In,Mn)Se with the Curie temperature about 800 K. The ferromagnetic cluster model and exchange interaction via 2D electron gas, as the reasons of spontaneous magnetization, are discussed. The dramatic transformation of (In,Mn)Se electron spin resonance (ESR) spectra as a function of temperature is revealed. At the magnetic field perpendicular to crystallographic c axis, a low-field line within the temperature range 70 down to 4.7 K is observed. It shifts to smaller magnetic fields with temperature decrease. Neutron diffraction studies reveal the strong rise for one of the reflection peaks with temperature decrease in the same temperature region where ESR spectra transformation occurs. This peak corresponds to double MnSe interplanar distance in the [111] direction what is a period of its magnetic lattice. Magnetic structure of (In,Mn)Se single crystal is discussed

Photoluminescence of two-dimensional GaTe and GaSe films

Gallium chalcogenides are promising building blocks for novel van der Waals heterostructures. We report on the low-temperature micro-photoluminescence (PL) of GaTe and GaSe films with thicknesses ranging from 200 nm to a single unit cell. In both materials, PL shows a dramatic decrease by 10e4–10e5 when film thickness is reduced from 200 to 10 nm. Based on evidence from continuous-wave (cw) and time-resolved PL, we propose a model explaining the PL decrease as a result of non-radiative carrier escape via surface states. Our results emphasize the need for special passivation of two-dimensional films for optoelectronic applications

Electronic and optical spectra in a diluted magnetic semiconductor multilayer

The effects of random distribution of magnetic impurities with concentration $x$ in a semiconductor alloy multilayer at a paramagnetic temperature are investigated by means of coherent potential approximation and tight-binding model. The change in the electronic states and the optical absorption spectrum with $x$ is calculated for weak and strong exchange interactions between carrier spins and localized spin moments on magnetic ions. We find that the density of states and optical absorption are strongly layer-dependent due to the quantum size effects. The electronic and optical spectra are broadened due to the spin fluctuations of magnetic ions and in the case of strong exchange interaction, an energy gap appears in both spectra. Furthermore, the interior layers show higher contribution in the optical absorption of the system. The results can be helpful for magneto-optical devices at a paramagnetic temperature.Comment: 7 pages, 5 figure

Hot wall growth and properties of lead telluride films doped by germanium and gallium

The researches results of films (PbTe)₁₋y(GaTe)y and (Pb₁₋xGexTe)₁₋y(GaTe)y of n-type conductivity with carrier concentration within (2⋅10¹⁷÷9⋅10¹⁸) cm⁻³ are represented. The films were growth by modified hot wall technology on barium fluoride substrate. A state of films surface was investigated by Atomic Force Microscope using both contact and taping modes. Hall coefficient, specific resistivity and thermoelectromotive force of films were measured in the temperature range 77-300 K. The investigation showed that the presence of germanium leads to an appearance of significant features on temperature dependencies of termoelectro-motive force which are connected with phase transition of displacement type. Doping gallium leads to n-type conductivity of films which increases with impurity concentration. The ionization energies of Ga impurities levels (n - exp(-E/2kT)) were within 3÷10 meV. The change of energy position and width of impurity level with increase of impurity concentration is established. The unusual protrusions on terraces of growth were discovered. The tops of protrusions can be considered as quantum dots. Inasmuch as composition of protrusions is expected to be distinguished from that of the terraces, they can create pieces of quantum wires

The influence of substrate temperature on properties of Cu-Al-O films deposited using the reactive ion beam sputtering method

For the first time, Cu-Al-O films were grown using the reactive ion beam sputtering at temperatures ranging from 80 to 380 °C in 50 °C increments. Correlations between the properties of as-grown films measured by X-ray diffraction, energy dispersive X-ray spectroscopy, atomic force microscopy, Fourier transform infrared spectrometry and optical transmission measurements have been discussed. It was shown that the increase of substrate temperature caused formation of the CuAlO2 phase. Additional optimization of technological parameters of growth and post-growth temperature annealing are necessary to obtain single-phase CuAlO2 films