The properties of multilayer (up to 80 layers) nanoperiodic (period up to ~12 nm) Al 2 O 3 /Ge and Al 2 O 3 /Si/Ge/Si systems annealed in a nitrogen atmosphere at temperatures from 700 to 900°C are studied using transmission electron microscopy, X-ray techniques of photoelectron spectroscopy, diffractometry, and reflectometry, and optical methods of photoluminescence and Raman scattering. In Al 2 O 3 /Ge samples annealed at 700°C, the formation of Ge nanocrystals with a size of ~3 nm is detected, which disappear at 800–900°C, when nanocrystals of the Al 6 Ge 5 semiconductor phase of large size (>100 nm) grow. The introduction of separating layers of Si (Al 2 O 3 /Si/Ge/Si) leads to the formation of nanocrystals of the SiGe x alloy at a temperature of 800°C, above which the size of the crystallites of this phase is about ~3–4 nm. The data obtained using X-ray techniques are in good agreement with the results of high-resolution transmission electron microscopy and Raman spectroscopy. In the Al 2 O 3 /Ge samples, photoluminescence is observed at room temperature at ~2.1 eV, and in the Al 2 O 3 /Si/Ge/Si samples, there is an additional luminescence peak at ~1.4 eV. Hydrogenation of the samples by annealing in a hydrogen atmosphere at 500°C enhances the luminescence intensity.

It has been established that the physicochemical properties of structures based on iron silicides formed by ion implantation of iron ions into silicon depend significantly on the time of subsequent high-temperature annealing. Objects with different geometric parameters are formed on the surface and the roughness increases. Annealing at 1000 C in an Ar atmosphere is accompanied by a decrease in the content of the Fe-Si chemical bonds during the first 60 seconds. The reason for the drop in thermal conductivity with increasing annealing temperature is the formation of silicide complexes.

It has been established that the physicochemical properties of structures based on iron silicides formed by ion implantation of iron ions into silicon depend significantly on the time of subsequent high-temperature annealing. Objects with different geometric parameters are formed on the surface and the roughness increases. Annealing at 1000 o C in an Ar atmosphere is accompanied by a decrease in the content of the Fe-Si chemical bonds during the first 60 seconds. The reason for the drop in thermal conductivity with increasing annealing temperature is the formation of silicide complexes. Keywords: iron silicide, thermoelectric, ion implantation, chemical composition, X-ray photoelectron spectroscopy.

Synthesis and modification of gallium oxide as a wide-bandgap semiconductor is a topical task in the fields of power electronics, UV detectors, gas sensors, telecommunication. In the present work, the Ga2O3 films deposited on sapphire substrates by magnetron sputtering have been studied. The influence of deposition parameters and subsequent annealing on the structure and optical properties of the synthesized films is analyzed. Ion doping of magnetron-deposited films with silicon is carried out by the ion implantation method. It is shown by the Raman scattering and optical transmission spectroscopy that ion irradiation leads to the disordering of the crystal structure, but subsequent annealing results in a partial recovery of the structure. Hall-effect measurements for irradiated and then annealed films do not reveal the formation of a conducting layer. Apparently, this is due to the fact that the main contribution to the resistance is made by grain boundaries in the magnetron-deposited films.

1 Research Institute of Physics and Technology, Lobachevsky University, Nizhny Novgorod 603950, Russia 2 Chuvash State Agricultural Academy, Cheboksary, 428017 Russia 3 Research and Development Center for Advanced Technologies in Microelectronics, Tomsk State University, Tomsk, 634050, Russia 4 Ion Implantation Laboratory, Institute of Physics Federal University of Rio Grande do Sul, Brazil 5 Department of Electrical Engineering, Indian Institute of Technology Jodhpur, Jodhpur, India 6 Centre for Materials Science and Nanotechnology, University of Oslo, Blindern, 0316, Oslo, Norway

Gallium oxide, and in particular its thermodynamically stable β-Ga2O3 phase, is within the most exciting materials in research and technology nowadays due to its unique properties. The very high breakdown electric field and the figure of merit rivaled only by diamond have tremendous potential for the next generation “green” electronics enabling efficient distribution, use, and conversion of electrical energy. Ion implantation is a traditional technological method used in these fields, and its well-known advantages can contribute greatly to the rapid development of physics and technology of Ga2O3-based materials and devices. Here, the status of ion implantation in β-Ga2O3 nowadays is reviewed. Attention is mainly paid to the results of experimental study of damage under ion irradiation and the properties of Ga2O3 layers doped by ion implantation. The results of ab initio theoretical calculations of the impurities and defect parameters are briefly presented, and the physical principles of a number of analytical methods used to study implanted gallium oxide layers are highlighted. The use of ion implantation in the development of Ga2O3-based devices, such as metal oxide field-effect transistors, Schottky barrier diodes, and solar-blind UV detectors, is described together with systematical analysis of the achieved values of their characteristics. Finally, the most important challenges to be overcome in this field of science and technology are discussed.

Synthesis of nanoparticles in insulators attracts tremendous attention due to their unique electrical and optical properties. Here, the gallium (Ga) and gallium nitride (GaN) nanoclusters have been synthesized in the silicon nitride matrix by sequential ion implantation (gallium and nitrogen ions) followed by either furnace annealing (FA) or rapid thermal annealing (RTA). The presence of Ga and GaN nanoclusters has been confirmed by Fourier-transform infrared, Raman and X-ray photoelectron spectroscopy. Thereafter, the effect of RTA and FA on the conduction of charge carriers has been studied for the fabricated devices. It is found from the current–voltage measurements that the carrier transport is controlled by the space charge limited current conduction mechanism, and the observed values of parameter m (trap density and the distribution of localized state) for the FA and RTA devices are ~2 and ~4.1, respectively. This reveals that more defects are formed in the RTA device and that FA provides better performance than RTA from the viewpoint of opto- and nano-electronic applications.

The influence of He+ ion irradiation on the transport and magnetic properties of epitaxial layers of a diluted magnetic semiconductor (DMS) (In,Fe)Sb, a two-phase (In,Fe)Sb composite and a nominally undoped InSb semiconductor has been investigated. In all layers, a conductivity type conversion from the initial n-type to the ptype has been found. The ion fluence at which the conversion occurs depends on the Fe concentration in the InSb matrix. Magnetotransport properties of the two-phase (In,Fe)Sb layer are strongly affected by ferromagnetic Fe inclusions. An influence of the number of electrically active radiation defects on the magnetic properties of the single-phase In0.75Fe0.25Sb DMS has been found. At the same time, the results show that the magnetic properties of the In0.75Fe0.25Sb DMS are quite resistant to significant changes of the charge carrier concentration and the Fermi level position. The results confirm a weak interrelation between the ferromagnetism and the charge carrier concentration in (In,Fe)Sb.

Nanosized films of stabilized zirconia with Au nanoparticles formed by implanting Au ions are studied by X-ray photoelectron spectroscopy and transmission electron microscopy. The effect of irradiation of films with Au ions and postimplantation annealing on the distribution of chemical elements and zirconium- containing ZrO x compounds over the depth of the films is studied. Based on the data on the dimensional shift of the Au 4 f photoelectron line, the average value of the nanoparticle size is determined.

AbstractNanosized films of stabilized zirconia with Au nanoparticles formed by implanting Au ions are studied by X-ray photoelectron spectroscopy and transmission electron microscopy. The effect of irradiation of films with Au ions and postimplantation annealing on the distribution of chemical elements and zirconium- containing ZrO_ x compounds over the depth of the films is studied. Based on the data on the dimensional shift of the Au 4 f photoelectron line, the average value of the nanoparticle size is determined.

The paper presents an original technique for quantitative analysis of the chemical composition from photo- electron lines obtained by X-ray photoelectron spectroscopy. Despite the simplicity, a proposed algorithm of spectral fit refinement allows one to control the fitting accuracy and to minimize the errors in determining the concentrations of chemical compounds. An obvious advantage of the iterative approach is the automatic con- vergence to the true spectrum fit form under correct input assumptions and conditions. The validity of the refinement technique is proved by the results of its application in the study of the chemical composition of three types of solid-state structures of nanoelectronics and spintronics. The error decrease in determining the concentration provides revealing new physicochemical features of the phase formation under various methods and parameters of the creation of structures. The discovered dependences of magnetic, electrical and optoelectronic properties on the local composition of nanosystems make it possible to formulate scientifically grounded principles of their development. Due to its simplicity and versatility, the spectral fit refinement technique can be extended to other experimental methods, where mathematical processing of spectral data is required.

The chemical and the phase compositions of multilayer nanoperiodic SiO x /ZrO 2 structures prepared by vacuum evaporation from separated sources and subjected to high-temperature annealing have been studied by X-ray photoelectron spectroscopy with a layer-by-layer etching. It is found that, under deposition conditions used, the silicon suboxide layers had the stoichiometric coefficient x ~1.8 and the zirconium-containing layers were the stoichiometric zirconium dioxide. It was found, using X-ray photoelectron spectroscopy, that annealing of the multilayer structures at 1000°C leads to mutual diffusion of the components and chemical interaction between ZrO 2 and SiO x with predominant formation of zirconium silicate at heteroboundaries of the structures. The SiO x layers of the annealed nanostructures contained ~5 at % elemental silicon as a result of the phase separation and the formation of fine silicon nanocrystals.

Методом рентгеновской фотоэлектронной спектроскопии с послойным травлением выполнен анализ химического и фазового состава многослойных нанопериодических структур SiOx/ZrO2, полученных испарением в вакууме из раздельных источников и подвергнутых высокотемпературному отжигу. Установлено, что при используемых условиях напыления слои субоксида кремния имели коэффициент стехиометричности x~1.8, а цирконийсодержащие слои представляли собой стехиометрический диоксид циркония. С помощью рентгеновской фотоэлектронной спектроскопии обнаружено, что отжиг многослойных структур при 1000oC приводит к взаимодиффузии компонентов и химическому взаимодействию ZrO2 и SiOx c образованием преимущественно силиката циркония на гетерограницах структур. Слои SiOx отожженных наноструктур содержали ~ 5 at.% элементарного кремния как следствие фазового разделения и формирования нанокристаллов кремния малого размера. Исследование проводилось при поддержке Министерства образования и науки РФ (государственное задание N 3.285.2014/K) и при частичной финансовой поддержке РФФИ (гранты N 14-02-00119 и 15-02-05086). DOI: 10.21883/FTT.2017.06.44491.377

The crystal structure, composition, and magnetic, and electric-transport properties of Mn x Ga y layers deposited onto a GaAs surface by pulsed laser deposition in a hydrogen atmosphere, pulsed laser deposition in vacuum, and electron-beam evaporation in vacuum are investigated. It is shown that the features of each technique affect the composition and crystal structure of the formed layers, and the degree of abruptness and crystalline quality of the heterointerface. Apparently, the composition and crystal structure are responsible for modification of the ferromagnetic properties. The defects in the heterointerface affect the properties of the Mn x Ga y /GaAs diode structure, in particular, the height of the Schottky diode potential barrier.

Исследованы кристаллическая структура, состав, магнитные и электротранспортные свойств слоев MnxGay, осажденных на поверхность GaAs методами импульсного лазерного осаждения в потоке водорода, импульсного лазерного осаждения в вакууме и электронно-лучевого испарения в высоком вакууме. Показано, что особенности каждого из методов оказывают влияние на состав и кристаллическую структуру формируемых слоев, на степень резкости и кристаллического совершенства гетерограницы. Состав и кристаллическая структура, предположительно, обусловливают модификацию ферромагнитных свойств. Дефекты гетерограницы оказывают влияние на свойства диодной структуры MnxGay/GaAs, в частности на высоту потенциального барьера диода Шоттки.

The possibility of fabricating a ferromagnetic injector based on a near-equiatomic CoPt alloy with pronounced perpendicular magnetization anisotropy in the InGaAs/GaAs spin light-emitting diode is shown. The physical properties of experimental spin light-emitting diode prototypes are comprehensively studied. Circularly polarized electroluminescence of fabricated diodes is obtained in zero magnetic field due to the remanent magnetization of CoPt layers.

Circularly polarized electroluminescence from GaMnAs/ n ++ GaAs/ n -GaAs/InGaAs/ p -GaAs heterostructures is studied. A hysteresis-like magnetic field dependence of the degree of circular polarization can be attributed to the injection of spin-polarized electrons from the magnetized GaMnAs layer. This effect is observed in the temperature range 10–90 K.