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Samples of ZnO and ZnO:Mn nanocrystals with Mn 2 and 4 at.% impurity concentrations obtained by ultrasonic spray pyrolysis were studied by X-ray diffraction. It was determined that the reflexes of the X-ray diffractions of the samples had a shift relative to the standard position towards large diffraction angles. This indicated the nonequilibrium state of the crystal lattice, which caused the appearance of strain stresses. Debye–Scherrer and Williamson–Hall methods were used to calculate the parameters of the crystal lattice, the size of nanocrystals, and strain stresses with different concentrations of Mn. When the concentration of Mn increased to 4 at.%, there was an increase in strain stresses in nanocrystals by 10 times in comparison with undoped ZnO. The unit cell volume of ZnO:Mn nanocrystals was significantly smaller in comparison with single-crystal ZnO, which indicated that they had their intrinsic defects.

A method is proposed for decomposing a sum of Gaussian functions to resolve an experimental photoluminescence spectrum into individual Gaussian bands. The decomposition process is based on a single experimental measurement. Here the parameters of a Gaussian (amplitude, location of maximum, and spectral half width) are calculated using three experimental points. The method has been tested in an analysis of the photoluminescence spectra of ZnS:Mn crystals in which the individual bands were revealed by the proposed method as well as by the Alentsev–Fock method and by derivative spectroscopy.

A smoothing method for noisy experimental photoluminescence spectra distorted by narrow spectral peaks and observed in ZnS:Mn bulk crystals and nanocrystals is proposed. Use of this method makes it possible to separate slowly varying components of the photoluminescence spectrum and narrow spectral peaks caused by radiation of the He–Cd laser plasma or harmonics of N2-laser radiation that excite photoluminescence.

Samples of ZnO:Mn nanocrystals with Mn concentrations of 2 and 4 at.% were synthesized by ultrasonic aerosol pyrolysis. The synthesis was carried out at 550°C using aqueous solutions of zinc and manganese nitrates. The samples obtained were subjected to heat treatment at 550°C and 850°C in air for 1 hour. The study of the samples by XRD and EPR methods shows that during the synthesis the process of doping ZnO nanocrystals with manganese occurs only partially, on the surface, in the near-surface layer. Residues of the Mn impurity are located on the surface of nanocrystals and appear during annealing at 550°С in the form of manganese oxides (Mn2O3). During heat treatment at 850°C, decomposition of Mn2O3 and bulk doping of ZnO:Mn nanocrystals occur.

In the work, the nanocrystals ZnO and ZnO:Mn with a concentration of Mn 2 and 4 at.% were obtained by the low-temperature freeze-drying method. For this purpose, solutions of zinc acetate Zn(CH3COO)2∙2H2O and manganese one Mn(CH3COO)2∙4H2O were used. By means of XRD, it is established that nanocrystals (NC’s) have a pure phase and wurtzite-type hexagonal lattice, their size is d ~ 65 nm. The EPR spectra of the samples have a broad absorption line. It is due to the presence of a large number of intrinsic and impurity defects in the NC’s. These defects are the result of the destructive action of hydrogen, which is a product of the thermal decomposition of zinc and manganese acetates. It is shown that there is a relationship between the number of crystal lattice defects in the ZnO:Mn NC’s and their ferromagnetic properties at room temperature. Samples of ZnO:Mn with a concentration of Mn 2 and 4 at.%. have a specific magnetization value of Мs equal to 0.089 and 0.045 emu/g, respectively. The results can have great potential in spintronic devices and spin-based electronics.

ZnSe and ZnSe:Mn nanocrystals were obtained by combustion synthesis (self-propagating high-temperature synthesis) using current pulses to initiate a reaction with amplitudes of ∼35 A and ∼40 A. The magnitude of the amplitude of the current pulse affects the size of the nanocrystals, their phase composition, the ratio of the cubic and hexagonal phases, the degree of microstresses and the density of dislocations. The inclusion of Mn dopants into ZnSe has little effect on the nanocrystal morphology and strongly influences the morphology of polycrystals. An EPR spectrum of Mn2+ ions with a hyperfine structure constant A = 6.55 mТ and a g-factor g = 2.0055, which is due to Mn2+ ions in a cubic environment, was found in self-activated and doped ZnSe and ZnSe: Mn nanocrystals. It was found that increasing the amplitude of the current pulse, which initiates the combustion synthesis reaction, increases the intensity of the diffusion processes and more effective isovalent substitution of Zn2+ ions by Mn2+ ions in the crystal lattice of ZnSe nanocrystals. The photoluminescence spectra of ZnSe and ZnSe:Mn nanocrystals were investigated, and individual emission bands were detected in the integral spectra. There were three such individual bands in the photoluminescence spectrum of ZnSe nanocrystals. Their maxima were characterized using the following parameters: λ max = 592 nm (E = 2.095 eV), λ max = 543 nm (E = 2.282 eV), and λ max = 505 nm (E = 2.455 eV). Six individual emission bands were detected in the photoluminescence spectra of ZnSe:Mn nanocrystals with the parameters: λ max = 675. 5 nm (E = 1.835 eV), λ max = 642.5 nm (E = 1.929 eV), λ max = 613 nm (E = 2.022 eV), λ max = 583.5 nm (E = 2.124 eV), λ max = 550 nm (E = 2.255 eV), λ max = 528.5 nm (E = 2.345 eV). This paper discusses the nature of the centers of radiative recombination of individual bands.

A method for computer processing of experimental EPR spectra using the derivative spectroscopy method is proposed. Application of the proposed method to a wide, structureless line of the EPR spectrum in ZnO: Mn nanocrystals obtained by the cryochemical method made it possible to isolate the components of the spectrum, associate them with Mn2+ ions. Application of the proposed method to the analysis of the EPR spectrum ZnO: Mn nanocrystal's obtained by ultrasonic pyrolysis of an aerosol with a different activator concentration after annealing made it possible to reveal the presence of an hyperfine structure of the EPR spectrum of Mn2+ ions, which are located in different local environments. The constants of the detected spectra are determined.

The smoothing method for experimental photoluminescence spectra, which uses Tikhonov regularization method, is proposed. Smoothing problem statement is performed as a statement of the minimization problem based on the least squares criterion. The functional to be minimized is a compound of two terms. The first one is the basic term, which determines the quality of data approximation provided by smooth function. The second one is the regularization term, which sets a constraint on the energy by smooth function derivative of a given order. A solution of the smoothing problem is obtained in the closed form analytically. The solution can be implemented by a simple array of matrix operations; one of those is an operation of matrix inversion. The necessity of matrix inversion imposes constraints on the order of derivative used in the proposed method and on noise level. It is related to the increase of either the order of derivative at the given noise level in data or the noise level at the given order of derivative, that deteriorates the conditionality of a matrix to be inverted and limits the scope of the proposed method, accordingly. Efficiency comparison of the proposed smoothing method, the Savitzky-Golay method, and the moving average method was performed by the numerical simulation of two models of photoluminescence spectra. Their advantages, disadvantages, and also the scopes of applicability are noted. The best values of operating parameters of these methods for the different noise levels in data were obtained. The conditions, under which the potential capabilities of the proposed smoothing method excel the potential possibilities of Savitzky-Golay method, were indicated. The results of smoothing the experimental photoluminescence spectra obtained for ZnO:Mn nanocrystals and ZnS:Mn crystals are provided.

It has been investigated the influence of heat treatment with the following temperins on the integral photoluminescence spectra and on the individual bands of this spectra. It has been showed the correlation between the changes of intensity of photoluminescence individual bands and real structure of crystal, controlled with the help of EPR method. The basic changes of photoluminescence and structural properties have threshold nature. They begin to show up at temperature of annealing T > 650o С. The maximum intensity of integral photoluminescence spectrum was observed in the region of phase transition crystal structure of zinc sulphide.

Досліджено спектри фотолюмінесценції нанокристалів твердих розчинів ZnSxSe1 – x:Mn, отриманих методом самопоширюваного високотемпературного синтезу. При кімнатній температурі ці нанокристали при всіх значеннях параметра х люмінесціювали у видимій області спектра. Методом похідної спектроскопії четвертого-шостого порядків у спектрах фотолюмінесценціі нанокристалів ZnSxSe1 – x:Mn виявлено шість індивідуальних смуг. Для складу з х = 1 ці смуги характеризуються такими максимумами випромінювання: λmax = 639 нм (1), 616 нм (2), 600 нм (3), 580.5 нм (4), 555 нм (5), 530.5 нм (6) відповідно. Смуги 1-5, ймовірно, пов'язані з іонами Mn2+ в різному локальному оточенні. Положення максимумів випромінювання індивідуальних смуг 4-5 практично не залежить від значення параметра х, максимуми смуг 2-3 монотонно зміщуються в короткохвильову область зі збільшенням параметра х. Максимум випромінювання смуги 1 стрибкоподібно змінює своє положення в діапазоні значень x = 0.2÷0.4, що пов'язано зі стрибкоподібному зміною локального оточення іонів Mn2 + у фазі MnS. Смуга випромінювання 6, напевно, не є елементарною, тому положення її максимуму випромінювання в залежності від значення параметра х носить стрибкоподібний характер. We investigated photoluminescence spectra of nanocrystals of ZnSxSe1 – x:Mn solid solutions obtained by the method of self-propagating high-temperature synthesis. At room temperature, these nanocrystals luminesced in the visible area of spectrum for all values of the parameter x. Six individual bands were discovered in photoluminescence spectra of ZnSxSe1 – x:Mn nanocrystals by the method of fourth-sixth derivative spectroscopy. For compounds with х = 1, these bands are characterized by maxima of emission: λmax = 639 nm (1), 616 nm (2), 600 nm (3), 580.5 nm (4), 555 nm (5), 530.5 nm (6), respectively. Probably, bands 1-5 are related to Mn2 + ions in different local environment. The maxima position of emission of 4-5 individual bands does not almost depend on x parameter value, maxima of 2-3 bands are monotonously displaced in a short-wave area with the increase of x parameter. Maximum of band emission 1 changes the hopping position in the range of x values: x = 0.2÷0.4, which is related to hopping change of local environment of Mn2 + ions in MnS phase. To all appearance, 6 band's emission is not elementary, therefore its position of maximum of emission depending on the parameter value of x has hopping character.