The reflection and luminescence spectra of a CdTe/CdMgTe heterostructures doped with iodine are studied. Iodine was introduced either into a barrier layer or into a wide CdTe quantum well. It is shown how the doping method and level affect the spectra and the temperature dependence of the quantum well exciton emission intensity.

The luminescence, reflection and absorption spectra of layered BiI3 crystals on samples of different quality are studied in a wide temperature range. Based on the data obtained, the parameters of the direct exciton, which has a high oscillator strength, are estimated

The optical properties of Cu2O nanowhiskers grown by the liquid method with material deposition in an electric field have been studied. The spectral lines forbidden by the selection rules for perfect Cu2O crystals were found in the Raman spectra. The nature of related phonon states is analyzed. In the photoluminescence spectra in the red and near-IR regions, broad bands of defective origin are observed. It was found that the presence of a band at 650 nm (1.9 eV) is a specific feature of the photoluminescence of nanowhiskers. Its properties are studied and possible radiation mechanisms are discussed. In the intrinsic absorption region of nanowhiskers, the photoluminescence band at 572 nm (2.17 eV) associated with band−band transitions is detected. At a low excitation level, the emission of a free exciton n = 1 of the yellow exciton series is observed with simultaneous emission of an optical phonon.

Исследовано близкраевое излучение пленок ZnO, выращенных методом молекулярно-пучковой эпитаксии, в широких интервалах изменения интенсивности возбуждения (до 1000 kW/cm2) и температур (5-300 K). Обсуждаются проявления экситон-фононного, экситон-экситонного и экситон-электронного взаимодействий в спектрах стимулированного излучения. Обнаружена смена механизмов стимулированного излучения в различных интервалах температур. Ключевые слова: экситонное излучение, стимулированное излучение, экситон-экситонное взаимодействие, экситон-электронное взаимодействие.

A series of ZnTe matrix containing two CdTe monolayers separated by barrier layers of different thicknesses is studied. The dependences of the energies of the exciton emission bands related to the CdTe monolayers, their relative intensities, and temperature behavior on the thickness of the ZnTe barrier layer are determined. It is established that CdTe monolayers can be considered independent of each other with a barrier layer thickness of more than 30 monolayers.

In this work, InGaN nanowires with a high In content were grown, for the first time, on hybrid SiC/Si substrates and compared with InGaN nanowires grown on Si. It was shown that InGaN nanowires on SiC/Si have lower indium content (by about 10%) compared to the nanowires on Si. The results can be beneficial for studying the growth mechanisms of InGaN nanowires and creating optoelectronic devices in the visible spectral range.

Abstract Heterostructures of the CdTe/ZnTe type with ultrathin quantum wells are studied. Lines of light and heavy excitons bound to the CdTe layers are observed in the spectra. It is found that the photoluminescence intensity of the light exciton is comparable to the luminescence intensity of the heavy exciton. The temperature shifts of these lines are different, and the lines are intersected at a temperature of 65 K. The estimates of the energy and wave functions of the exciton states have made it possible to clarify parameters of some bands and excitons in such structures.

Изучена экситонная фотолюминесценция оксида цинка в температурном интервале 5-300 K. Проведен анализ формирования контура полосы экситонного излучения при 300 K и возбуждении He-Cd-лазером в спектрах нелегированных кристаллов, порошка марки ОСЧ и тонких ALD-пленок толщиной 4-450 nm. Исследовано влияние процессов фотодесорбции и фотоадсорбции атмосферного кислорода на спектр экситонного излучения порошка ZnO в последовательных циклах смены среды вакуум--воздух при комнатной температуре и непрерывном возбуждении He-Cd-лазером. Ключевые слова: экситонное излучение, фотоадсорбция, фотодесорбция, экситон-фононное взаимодействие.

Исследованы спектры отражения и модуляционного фотоотражения от эпитаксиальных слоев ZnO и Zn1-xMgxO, а также квантовых ям ZnO/Zn1-xMgxO при нормальном и наклонном падении света. Сравнение экспериментально измеренных и расчетных спектров позволило уточнить некоторые параметры экситонов в этих структурах и уточнить порядок следования энергетических зон в ZnO. Ключевые слова: гетероструктуры, квантовые ямы, экситоны, спектроскопия.

The luminescence of CdTe layers with a nominal thickness of 1, 2, 4, and 8 monolayers grown by atomic layer epitaxy in ZnTe matrix was studied. It is shown that layers with a thickness of 1 and 2 monolayers are homogeneous, while layers with a nominal thickness of 4 and 8 monolayers are the planar QD arrays. The sizes of QDs and their size dispersion increase with an increase in the nominal thickness of CdTe layer. The luminescence excitation spectra of CdTe layer in the samples vary significantly. It has been shown that, depending on the energy distance between the CdTe and ZnTe exciton levels, the ratio of contributions to the energy transfer via the exciton ZnTe and charge carriers varies greatly.

AbstractThe exciton luminescence spectra of CdTe/ZnTe heterostructures containing two thin CdTe layers separated by barriers of different thickness were studied. The complex temperature dependence of the intensity of luminescence from these layers in its underbarrier and abovebarrier excitation led to the conclusions about the effect of the thickness of the barriers on the energy transfer between the CdTe layers and gave the possibility to observe, at specific temperatures, the implementation of a resonant-type excitation. The dependence of the shape of the exciton emission contours on the excitation level gives information about the real structure of CdTe layers with the monolayer thickness of 1.5 and 4.0 monolayers.

The low-temperature luminescence spectra of Cu2O crystals grown by the different methods (copper oxidation, induction melting, magnetron sputtering, hydrothermal synthesis) and of natural crystal are compared. It was concluded that the high quality of natural crystals and crystals grown by the hydrothermal method is due to the low temperature process of their formation which minimizes the strains.

AbstractThe optical properties of the Cd_0.4Mn_0.4Te/Cd_0.5Mg_0.5Te heterostructure with quantum wells of 7 monolayers in thickness are studied. The temperature dependences of the integral intensity of luminescence of the barrier layer and quantum well and intracenter luminescence of manganese ions are determined, and the luminescence excitation spectra are measured. Numerous components corresponding to LO phonons of the CdTe, MgTe, and MnTe types are observed in the Raman scattering spectra.

AbstractThe effect of intense UV irradiation on the photoluminescence (PL) spectra of ZnO powders and nanocrystalline films obtained by atomic layer deposition (ALD) was investigated. At room temperature, the behavior of the spectra under continuous UV irradiation in multiple vacuum-atmosphere cycles was studied. The changes in the intensities of exciton radiation and radiation in the “green” band region, associated with the phenomena of oxygen photodesorption and photoadsorption, are discussed. In the temperature range of 5–300 K, the effect of strong UV irradiation on the near-edge luminescence spectrum of ZnO films was studied. The nature of a new line arising in the photoluminescence spectra of an irradiated film in the region of emission of bound excitons is discussed.

AbstractReflectance and photoluminescence spectra of the ZnO/Zn_0.78Mg_0.22O structures with ZnO quantum wells and thick ZnO and Zn_0.78Mg_0.22O layers have been thoroughly investigated at different temperatures and excitation intensities and wavelengths. All the observed spectral lines have been identified. It has been established that the built-in electric field does not affect the spectrum as strongly as was expected. The built-in field is apparently effectively screened by the carriers that have migrated to the bands from donor and acceptor levels. The parameters determining the exciton properties in zinc oxide have been estimated.

AbstractCopper (I) oxide and zinc oxide films are formed on silicon and glassy quartz substrates by magnetron assisted sputtering. The thickness of the films is tens and hundreds of nanometers. The films are grown at different substrate temperatures and different oxygen pressures in the working chamber. The film samples are studied by the X-ray diffraction technique, scanning electron microscopy, and optical methods. It is established that an increase in the substrate temperature yields a change in the surface morphology of copper (I) oxide films towards the formation of well-pronounced crystallites. The reflectance and Raman spectra suggest that the quality of such films is close to that of bulk Cu_2O crystals produced by the oxidation of copper. As concerns ZnO films, an increase in the substrate temperature and an increase in the partial oxygen pressure make it possible to produce films, for which a sharp exciton structure is observed in the reflectance spectra and the emission of excitons bound at donors is observed in the luminescence spectra.

AbstractThe transmission spectra of GaSe and GaS crystals of different thicknesses prepared by mechanical stratification of bulk crystals have been investigated. The quantum-size shifts of exciton resonances in thin GaSe samples are as high as 12 meV, which is close to the exciton binding energy. The high-energy interband transitions in GaSe and GaS are observed near 3.4 and 3.7 eV, respectively.

Кристалл нитрида галлия толщиной 5 mm был выращен методом хлорид-гидридной газофазной эпитаксии на сапфировой подложке, от которой кристалл отделился в процессе остывания. На ранней стадии был реализован трехмерный режим роста с последующей сменой на двумерный режим. В нескольких характерных областях образца исследованы спектры экситонного отражения, экситонной люминесценции и рамановского рассеяния. Анализ этих спектров и сравнение с ранее полученными данными для тонких эпитаксиальных слоев GaN с широким диапазоном легирования кремнием позволили сделать выводы о качестве кристаллической решетки в этих характерных областях образца. Работа выполнена в рамках инициативной темы СПбГУ N 11.52.454.2016, для исследования спектров рамановского рассеяния использовалось оборудование Ресурсного центра СПбГУ "Оптические и лазерные методы исследования вещества". DOI: 10.21883/FTT.2017.12.45237.120

Методом магнетронного распыления сформированы наноразмерные слои оксида меди (I) на стеклянных и кремниевых подложках при комнатной температуре в бескислородной среде и проведены исследования их структурных и оптических свойств. Показано, что на кремниевой подложке происходит формирование оксида меди с меньшей разупорядоченностью, нежели на стекле, это подтверждается большей интенсивностью и меньшей полушириной рефлексов дифрактометрической кривой. Наибольшая интенсивность рефлексов дифрактометрической кривой наблюдается для пленок Cu2O, выращенных на кремнии при мощности магнетрона 150 Вт. Спектральная зависимость коэффициентов поглощения и пропускания этих же пленок Cu2O согласуется с известными зависимостями для объемных кристаллов. В рамановских спектрах пленок идентифицированы фононы, соответствующие кристаллической решетке кубических кристаллов Cu2O. DOI: 10.21883/FTP.2017.01.8318