We conducted a comprehensive investigation into the nanostructuring of the ZnO/CoO mixture by laser heating and optical attributes of partial decomposition of the obtained two-phase system represented by ZnO and ZnCo2O4. Starting mixtures were obtained across a broad range of dopant, CoO, concentrations, spanning from 5 % to 90 % of CoO. The samples were methodically prepared using the coprecipitation method and subjected to calcination at 600 degrees C. Laser-induced heating experiments were conducted at nine distinct laser powers. The characterization of these samples was accomplished through the utilization of SEM, XRD, and Raman spectroscopy. XRD analysis unveiled the presence of ZnO and ZnCo2O4 phases. Concurrently, we systematically monitored nanostructuring effects caused by laser-induced heating, the influence of partial decomposition on the behavior of surface optical phonons (SOP), and phase transitions in the samples with varying dopant concentrations during the performed experiment. New phases, including Zn1-xCoxO, ZnyCo3-yO4, CoO, and even the Co3O4 phase, were unveiled. The Raman spectra obtained distinctly indicate the presence of surface optical phonons (SOP), emphasizing the existence of the ZnO phase. The alterations in the behavior of surface optical phonon (SOP) modes were meticulously examined by laser-induced heating nanostructuring effects where it became evident that there was a discernible loss of these modes with an increase in dopant concentration and laser power. This detailed study sheds light on the intricate interplay between dopant concentration, laser power nanostructuring, partial decomposition, and the evolution of phase transformations and surface optical phonon modes in the examined samples.

Lead telluride and germanium telluride are well-known IV-VI semiconductors, which is now the focus of research due to the perspective of application as thermoelectrics for midrange temperatures. Solid solutions and heterostructures on this basis, obtained by molecular beam epitaxy, are a promising direction for the development of these materials. In this paper, we have focused on the Raman spectra excited by the 514.5 nm laser line (out of resonance) of PbTe, GeTe, (Pb, Ge)Te, and (Pb, Ge, Eu)Te layers grown on BaF2 (111) monocrystalline substrates. The obtained phonon properties are related to the properties of the corresponding bulk materials or can be explained by a model that takes into account the difference in the masses of the constituent elements only, as is the case with the local mode of Ge in PbTe (registered at about 181 cm−1). Multiphonon processes registered for this phonon are a consequence of the change in the electronic structure of PbTe and electron-phonon interaction. An improvement in the quality of thin films due to doping with Eu ions was also registered.

Laser-induced transient current technique (L-TCT) and photocurrent-voltage characteristics (PC-V) are commonly used in many laboratories to measure the values of μ e τ e and τ e . For both techniques (PC‑V and L-TCT), we observed a significant impact of the surface preparation method for the contacts on the obtained results. Different contact shapes were used on the anode to increase the interaction of light-generated charge at the cathode with near‑surface trap states and near-surface recombination, while a planar cathode was point-illuminated. In one experiment, the charge (electrons) generated at the cathode flowed directly to the pixel located vis a vis on the anode, while in another experiment, the charge had to flow first through the near-surface layer at the cathode and then to the lateral pixel on the anode. In the PC-V method, LEDs with photon energy ħω≤E g or ħω>E g (E g is the bandgap energy) were used as the light source with adjustable light intensity. In the L‑TCT method, both contacts (on the cathode and anode) were in the form of pixels. In the L-TCT method, the laser radiation energy ħω was about 2E g . In some experiments the cathode was additionally illuminated by using LED, with ħω>E g or ħω≤E g , in other not. By using the PC-V method for the well prepared surface we obtained μ e τ e ~ 10 −3 cm 2 V −1 from fitting with the Hecht formula. For a poorly prepared surface, the results were fitted with the Ridzonova formula. The electron mobility μ e was obtained from the L-TCT method. The observed results for current waveforms in the L-TCT measurements for unilluminated and LED-illuminated cathodes with different electric fields and light intensity of LEDs were compared with the PC-V results, particularly for ħω of LED≳E g . In our interpretation we consider two processes: ionization of traps by the electric field, and deionization of traps by recombination with electrons excited by the LED light illuminating the cathode.

The aim of this study was to investigate the magnetic properties of mixed nanocrystalline Zn/manganese oxide compounds synthesized by a hydrothermal method. These compounds are designed as (ZnO)1−n(MnO)n, where index n ranges from 0.05 to 0.60. The results of magnetic measurements, including AC magnetic susceptibility as a function of temperature (up to 160 K) and frequency (from 7 Hz up to 9970 Hz), as well as DC magnetization in magnetic fields up to 9 T and temperature up to 50 K, are reported. We observed various types of magnetic behavior depending on the nominal weight content of MnO. Samples with a low nominal content (up to n = 0.10) of MnO exhibited Curie–Weiss behavior at higher temperatures. For samples with high nominal weight contribution (from n = 0.30 to 0.60), spin-glass-like or/and weak ferromagnetic behavior is observed.

The aim of the present work is to study the magnetic properties of nanocrystalline ZnO(MnO) synthesized by hydrothermal method. Detailed structural characterization was performed by use of X-ray diffraction and micro-Raman spectroscopy measurements. The morphology of the samples was studied using SEM and TEM. The results of magnetic measurements carried out using AC magnetic susceptibility as a function of temperature (up to 160 K) and frequency (from 7 Hz up to 9970 Hz) as well as DC magnetization in magnetic fields up to 5 T and temperature up to 50 K are reported. We observed different types of magnetic behavior depending on the nominal MnO content. Samples with low nominal content (up to 20 wt%) of MnO demonstrated Curie–Weiss behavior at higher temperatures. For samples with high content of magnetic dopant (from 30 wt% up to 60 wt% of MnO), spin-glass like or/and weak ferromagnetic behavior is observed.

Photocurrent-voltage characteristic (PC-V) is a method of determining the critical parameter in X-ray and gamma-ray detector plates, i.e., the carrier mobility-lifetime product, μτ. We show for the (Cd,Mn)Te samples that the measurement results depend strongly on the surface treatment and the space charge distribution. The PC-V characteristics obtained for ħω > Eg and ħω ~ Eg indicated that etching with 20% HCl caused an appearance of a significant concentration of very shallow surface traps at the (Cd,Mn)Te sample surface. These traps seriously changed the results of measurements of PC-V characteristics and PC kinetics. We also noticed a small contribution of holes to photoconductivity in the PC kinetics. The measurements of PC-V characteristics for ħω > Eg may test the detector plate surface quality.

Diluted magnetic semiconductor (DMSs) multiferroics offer intriguing possibilities and potential for spintronic applications due to the incorporation of magnetic ions in semiconducting lattice [1]. Ferroelectric GeTe based multiferroics propose striking properties to explore entanglement of magnetic and spin-orbit coupling in one system [2]. Further studies of these materials establish the basis for Rashba spin splitting, magnetoresistance, spin-torque manipulation of magnetic domains and novel quantum phases like topological insulators. In this work, we present systematic studies of ferroelectric GeTe based Ge1−x−y(SnxMny)Te crystals grown in the range 0.18 ≤ x ≤ 0.79 and 0.020 ≤ y ≤ 0.086, focused over their magnetic, magnetotransport and ferroelectric properties. We examined the ferroelectric phase transition temperature changes with the chemical composition of the samples. Temperature dependent ac susceptibility measurements were performed to explore the behavior of magnetic ordering of the chosen compositions. In extensively studied group IV-VI narrow band gap semiconductors, the Ruderrnan-Kittel-Kasuya-Yosida indirect-exchange in-teraction is known to mediate ferromagnetism via free carriers, here we report Ge1−x−y(SnxMny)Te multiferroic and its magnetic exchange interactions. Furthermore, multiferroic structures such as Ge1−x−y(SnxMny)Te present the possibility to understand the dynamics at the ferroic domain walls which could lead to atomic scale electronics [3].

Semiconductors of II-IV-V-2 type with chalcopyrite structure have been studied for several decades. Due to advances in materials synthesis technologies, and doping with various elements, the possibilities of their application have expanded. In this paper, polycrystalline ZnSnSb2 + Mn was examined with the aim to explain the connection of its high free carrier concentration with the material structure and influence on optical properties. Two samples of Zn1-xMnxSnSb2 with different compositions (x = 0.027 and x = 0.076) and significant difference in carrier concentrations were analyzed. Their structural properties were examined by x-ray diffraction, optical microscopy, and AFM. The existence of several different phases - ZnSnSb2, ZnSb, SnSb, and small amounts of Sn and MnSb, as well as very complex microstructures, were registered. It was found that the high free carrier concentrations are caused by a large number of defects, especially zinc vacancies. Optical properties were analyzed using IR spectroscopy at room temperature. Based on the analysis of IR reflection spectra, the presence of plasmon - phonons interaction was registered. It was determined that three ZnSnSb2 phonons of B-2 symmetry interact with plasma, which then leads to the change of their positions. A detailed analysis of this interaction provides insight into the behavior of some other material parameters. Also, vibration modes of ZnSb and SnSb phases were registered on the spectra. Knowledge of phonon behavior and their interaction with plasma is important for possible applications, especially as a thermoelectric material.

Magnetoresistance, ac and dc magnetization, and photoluminescence (PL) experiments have been performed on the p-type Zn0.99Mn0.01Te and Zn0.97Mn0.03Te alloys strongly doped with phosphorus (P). The investigated samples exhibit spin glass behavior with ferromagnetic regions near the freezing temperature T-f = 1.9 K and colossal negative magnetoresistance (negMR) of 2.2 x 10(3) times at 4.2 K for 0 <= B <= +/- 6 T. The negMR curves contain occurrences of hysteresis providing evidence for the memory effect. Looking for possible ferromagnetic interactions responsible for the spin glass behavior at low hole densities, we observe in PL spectra that the P doping quenches internal recombination in Mn2+ ions. This strongly indicates a charge transfer between Mn2+ and P2- ions leading to the creation of Mn3+ and P3- ions. The creation of Mn3+ is confirmed by an observation of strong PL enhancement at excitation energies lower than the band gap and PL study at various temperatures. The resulting simultaneous existence of the mixed valence Mn2+ and Mn3+ ions can lead to double exchange mechanism of ferromagnetic interaction. Also, Mn3+ ions can exhibit a superexchange interaction leading to local ferromagnetic phases.

The nanopowders of (ZnO)1–x(Al2O3)x, where x ranges from 0 to 0.7, were obtained by two chemical methods: the co-precipitation/calcination and hydrothermal synthesis. The first assessment of structural and optical properties of the obtained nanopowders was undertaken by the SEM, XRD, Raman and far-infrared spectroscopy, which was followed by the photoluminescence spectroscopy at room temperature. The obtained far-infrared reflectivity spectra were analyzed using the fitting procedure. The dielectric function of ZnO–Al2O3 nanopowders was modeled by the Maxwell-Garnet formula under the assumption that the nanopowders are a mixture of homogenous spherical inclusions in air. The combined plasmon-LO phonon modes (CPPM) were observed in the far-infrared reflection spectra. The photoluminescence spectra contain emissions related to the presence of ZnO, ZnAl2O4, and AlOOH phases in the nanomaterial, which is in agreement with the results obtained by other experiments.

The influence of the locally induced laser heating on MnO nanoparticles were investigated by atomic force microscopy (AFM) and far-infrared spectroscopy (FIR) at room temperature, in the spectral region between 80 and 600 cm(-1). The FIR spectra were analyzed by using Maxwell-Garnet formula, where MnO nanoparticles are modeled as a mixture of homogeneous spherical inclusions in air. Laser induced heating leads to the conversion of the part MnO nanoparticles into the MnO2, Mn3O4 and MnOOH, along with possible formation of elemental Mn on the sample surface.

Superparamagnetic behavior of ZnFe2O4 nanoparticles formed by doping ZnO with various content of α‐Fe2O3 is investigated by 57Fe Mössbauer spectroscopy measurements performed in a temperature range from 300 to 10 K. The nanoparticles were obtained by the hydrothermal synthesis with Fe2O3 doping ranging from 30 to 70 wt.%. The results are compared with the ZnO sample doped with 60% Fe2O3, prepared by the calcination method. At room temperature the Mössbauer spectra of all samples consist of a nonmagnetic component characteristic for Fe3+ ions in ZnFe2O4 spinel structure. Low temperature Mössbauer measurements of hydrothermally synthesized nanoparticles reveal appearance of a magnetically ordered spectral component at about 120 K for the sample doped with 70% Fe2O3 and below 30 K for all other compositions. The spectral contribution of the magnetic component increases gradually at decreasing temperature at the expense of the nonmagnetic component, indicating superparamagnetic relaxation of ZnFe2O4 nanoparticles. It is concluded that the spinel nanoparticles are significantly smaller in the samples obtained by the hydrothermal method than by the calcination one. The blocking temperature is found to decrease with decreasing content of Fe2O3 doping during preparation of the nanoparticles.

The far-infrared spectroscopy was used to analyze optical properties of PbTe single crystals doped with different amounts of Si. A dielectric function that takes into account the plasmon-phonon interaction was employed in the measured data manipulation. Two frequencies of plasmon-phonon coupled modes were obtained with the best-fit method, whereas the values for LO mode and plasma frequency (ωP) were calculated. The best-fit to the experimentally obtained spectra agrees very well with the theoretical prediction.

The AC magnetic susceptibility in the range 5–130 K of the tellurite glass systems: TeO 2 –MnO 2 –ZnO–PbO and TeO 2 –MnO 2 –V 2 O 5 –Fe 2 O 3 was measured and analyzed. The investigations of the AC magnetic susceptibility facilitated the determination of the molar susceptibility, paramagnetic magnetic susceptibility, paramagnetic Curie temperature, and magnetic entropy changes of the tellurite glasses. The results clarified that the temperature dependence of the magnetic susceptibility deviated from the Curie law and the increase of the small negative values of Curie temperature indicated negative interchange interactions between the antiferromagnetically coupled manganese ions within the present glass network. The magnetic moments evaluated from susceptibility measurements of the glasses show the predominance of the Mn 2+ valence state than Mn 3+ valence state of MnO 2 .

Structural and optical properties of CdTe thin films were investigated applying atomic force microscopy (AFM), XRD powder technique, Raman spectroscopy and far–infrared spectroscopy. CdTe thin films were prepared by using thermal evaporation technique. In the analysis of the far – infrared reflection spectra, numerical model for calculating the reflectivity coefficient for system which includes films and substrate has been applied. Effective permittivity of film mixture (CdTe and air) was modeled by Maxwell – Garnet approximation. We reveal the existence of surface optical phonon (SOP) mode and coupled plasmon-SOP modes (CPSOPM).

The phase changes of MnO nanoparticles under laser-induced heating have been studied. Previous confirmation of the existence of MnO phase was based on the X-ray diffraction measurements. Here, we report the experimental spectra of nonresonant Raman scattering in the range between 100 and 1,600cm(-1), for a sample irradiated with 8 different laser powers. The laser-induced heating has produced change in existing phases in sample, destruction of MnO phase, and creation of MnO2, Mn3O4, and MnOOH phases along with formation of Mn2+ on the sample surface. These phase changes have been confirmed by X-ray diffraction and atomic force microscopy measurements.

The aim of the present work was to study the magnetic properties of ZrO2(Mn) nanocrystals prepared by microwave-assisted hydrothermal synthesis using three different precursors: KMnO4, MnCl2, and Mn(NO3)2. The structural characterization was performed by means of X-ray diffraction. The morphology of the samples was studied by using STEM microscopy. The magnetic properties were studied by means of alternating current (AC) susceptibility (at a small AC magnetic field with amplitude not exceeding 5 Oe) and direct current (DC) magnetization (up to 9 T). All of the samples demonstrated Curie–Weiss behavior at higher temperatures with negative values of the Curie–Weiss temperature θ. It was shown that the conditions of the synthesis, e.g., pH and the type of precursor, can be adjusted to decrease the value of the Curie–Weiss temperature and reduce antiferromagnetic interactions.

Doping of II-IV-V-2 semiconductors opens up new opportunities for wide application. Addition of Mn to these materials induces formation of magnetic clusters, which are responsible for high-temperature ferromagnetism. Our aim was to examine how the addition of Mn influences the optical and structural properties of ZnSnSb2 by micro-Raman spectroscopy. For four samples of Zn1-xMnxSnSb2 synthesized using the direct fusion method, with x=0.027, 0.066, 0.076, and 0.086, Raman spectra were measured at room temperature in spectral range from 60 to 300cm(-1). The obtained results indicate that these are multiphase materials. Based on the size and shape of complex microstructures, which consist of different phases and clusters, dispersive and duplex or triplex types of microstructures can be identified. Existence of ZnSb, SnSb, and MnSb phases was confirmed. By analyzing the Raman spectra, phonons of ZnSb and SnSb are determined and they are consistent with the data from literature. Phonon properties of ZnSnSb2, as well as of MnSb, are experimentally obtained for the first time. On the basis of a shift of the ZnSnSb2 phonons, we found that some amount of Mn entered lattice and form Zn1-xMnxSnSb2. Microstructures affect the physical properties and behavior of a material. Analysis of this complex semiconductors and obtained results are important for their optimization and customization for possible applications.

We have been studying magnetic properties of magnetic ion clusters in ternary, quaternary, and quinary IV-VI and II-IV-V-2 diluted magnetic semiconductors with varying concentrations of different magnetic and non-magnetic cations. We observed clusters of different types, from non-random distribution of magnetic ions in the host lattice to precipitates with the crystalline structure different from that of the host. The size of such precipitates varied from 200 nm to 20 mu m. Depending on the type and size of clusters we observed different magnetic properties of the compounds, such as paramagnetic, spin-glass, spin-glass-like, or ferromagnetic states. For example, Zn1-xMnxGeAs2 compounds with x <= 0.053 were paramagnetic with evidence of small short-range magnetic interactions, while in the same material with x >= 0.078 we observed room-temperature ferromagnetism. In IV-VI DMS clusters usually created a spin-glass or spinglass- like state. However, in some Ge1-x-yPbxMnyTe crystals we observed a co-existence of two very different spin-glasslike states with transition temperatures T-1 approximate to 5 K and T-2 approximate to 90 K.