Рассматривается возможность анализа локальной атомной структуры по сильно перекрывающимся экспериментальным EELFS-спектрам двух различных химических элементов. С поверхности сплавов CuxNi1 - x и CuxMn1 - x (х = 0.5) получены М2,3 спектры протяженных тонких структур энергетических потерь электронов. Предложена методика определения параметров локальной атомной структуры (координационные числа, длина химической связи и параметры их дисперсии) ближайшего атомного окружения сверхтонких (1–5 нм) поверхностных слоев двухкомпонентных сплавов 3d-металлов из перекрывающихся протяженных тонких структур спектров энергетических потерь электронов. Методика апробирована на экспериментальных M2,3 EELFS-спектрах поверхности тестовых сплавов Cu50Ni50 и Cu50Mn50.

A technique for determining parameters of the local atomic structure of a manganese-oxygen system by the extended energy loss fine structure method has been proposed. Experimental extended energy loss fine structure spectra of the clean surface of metallic manganese and its stoichiometric oxides have been measured. Normalized oscillating portions have been separated from the experimental spectra and analyzed by solving the inverse problem using the Tikhonov regularization. The parameters of the local atomic structure of the objects under study, i.e., coordination numbers, bond lengths, and their variance parameters, have been determined.

In this work, we consider the possibility of analyzing local atomic structure based on strongly overlapping experimental extended electron-energy-loss fine structure (EELFS) spectra of two different chemical elements. M 2,3 EELFS spectra have been obtained from the surface of Cu x Ni1 − x and Cu x Mn1 − x (x = 0.5) alloys. The method of determining the parameters of the local atomic structure (coordination numbers, lengths of the chemical bonds, and the parameters of their dispersion) of the nearest atomic surroundings in ultrathin (1–5 nm) surface layers of two-component alloys of 3d metals has been suggested based on the overlapping extended fine structures of the electron-energy-loss spectra. The method was tested on experimental M 2,3 EELFS spectra of the surface of testing alloys Cu50Ni50 and Cu50Mn50.

Предложено теоретическое описание процессов формирования протяженных тонких структур спектров вторичных электронов 3d-металлов с учетом XAFS-подобного рассеяния вторичных электронов в конечном состоянии в процессах первого и второго порядка и электрона промежуточного состояния в процессе второго порядка. Предложена методика и проведены расчеты матричных элементов, определяющих атомные амплитуды и интенсивности соответствующих электронных переходов. Показано, что учет процессов первого и второго порядков и немонотонность интенсивностей соответствующих атомных электронных переходов позволяют описать аномальное температурное поведение протяженных тонких структур спектров вторичных электронов.

The formalism of collision theory was used to describe the formation of extended electron energy loss fine structures taking into account multipolarity of the electron-impact excitation of internal atomic layers, and the formation of extended secondary electron fine structures taking into account the first and second order nonradiative relaxation of excited state of the electronic subsystem of a sample. The extended electron energy loss fine structures, extended secondary electron fine structures, and corresponding oscillating parts were obtained in the experiments. The experimental and calculated data showed good agreement.

The extended energy-loss fine structure (EELFS) spectra for pure nickel samples (M 2,3 EELFS spectra), a NiO stoichiometric film (nickel M 2,3 EELFS and oxygen K EELFS spectra), and an “inhomogeneous” oxide film (Ni-O system) on the surface of nickel have been obtained. The calculations of amplitudes and intensities of electron transitions are performed for the corresponding inner levels of atoms taking into account the multipolarity of the excitation of inner atomic levels by an electron impact. The normalized oscillating components are extracted from EELFS spectra using the results of calculations. Close agreement between experimental results and theoretical data obtained for test Ni samples and NiO films indicate that the theoretical approaches applied to the description of EELFS spectra and the results of calculations are good approximations. Atomic pair correlation functions are obtained from the experimental normalized oscillating components of EELFS spectra with the use of the Tychonoff regularization technique.

Simple formulas for describing the extended fine structures of spectra of electron energy losses (EELFS) with allowance for the multipolarity of the process of excitation of the inner level of atoms by electron impacts have been derived. The experimental M 2,3 EELFS spectra of nickel and K EELFS spectra of oxygen were obtained from pure samples of nickel and stoichiometric oxide film on the surface of nickel. Good agreement has been obtained between the experimental and calculated results, as well as between the parameters of a local atomic structure obtained from the experimental EELFS spectra and available crystallographic data.

The work presents the theoretical description of formation processes of extended electron energy loss fine structure (EELFS) spectra. Simple analytical formulas are obtained to calculate EELFS spectra. Methods are proposed to compute amplitudes and intensities of electronic transitions of different multipolarity in electron-impact excitation of the inner shell of an atom. The corresponding test calculations are performed. We present experimental M 2,3 EELFS spectra of 3 d -metals obtained from clean surfaces of Fe, Ni, and Cu and ultrathin stoichiometric oxide films of Fe 2 O 3 , NiO, and CuO as well as K EELFS spectra of oxygen from thin stoichiometric oxide films. Techniques are proposed to extract normalized oscillating parts from experimental EELFS data based on the use of calculated intensities of the corresponding electronic transitions. Atomic pair correlation functions are obtained for the objects under study from experimental EELFS data with regard to multipolarity of electron impact excitation of the atomic inner shell. Experimental results correspond well to known crystallographic data (partial interatomic distances, coordination numbers, and Debye-Waller factors).

The local atomic structure of thin surface layers of crystalline quasi-binary Cu(In x Ga1−x )Se2 solid solutions was studied by SIMS and EXAFS techniques. The SIMS method showed that the elemental composition of the sample changes most significantly in thin layers at a depth of 5–10 nm; in deeper layers, the component concentrations correspond to the bulk values. The EXAFS method in the x-ray fluorescence mode showed that the results obtained are in agreement with the assumption that quaternary crystalline quasi-binary Cu(In x Ga1−x )Se2 solid solutions exhibit local disorder while average long-range order is detected from x-ray diffraction data.

In the present paper in the one-electron approach has been account the process of excitation inner level and corresponding Auger-relaxation process in the creations LMM Auger-lines in 3d-metals and corresponding stoichiometric oxides. Well qualitative agrement of experimental data end calculated ones demonstrate the necessity of taking into account the process of inner level atom excitation in Auger theory.

Получены протяженные тонкие структуры спектров энергетических потерь электронов (EELFS) M-краев ионизационных потерь для чистой поверхности монокристаллического (110) Ni, стехиометрической сверхтонкой (1 нм) оксидной пленки NiO и сверхтонкой пленки нестехиометрической системы Ni-O. Из полученных EELFS-спектров выделены соответствующие нормированные осциллирующие части. В приближении ОПВ проведен расчет амплитуд и интенсивностей возбуждения внутреннего уровня атома вещества электронным ударом. На основе расчетных данных, в рамках решения обратной задачи по Тихонову, найдены межатомные расстояния и координационные числа.

For extended electron energy loss fine structure (EELFS) in the case of ionized K -level, the effects of nondipole processes are estimated at different excitation energies and scattering angles of incident electron. A multiplet resolution converging fast for any scattering angles of incident electron is suggested, and simple analytical expressions up to the quadrupole term are derived. Using these estimates, we have calculated the Al K -edge EELFS spectrum and compared the calculated data with the experimental results. The problem of violation of the dispersion law of secondary electrons is discussed; this problem is caused by the finite lifetime of the excited electronic subsystem of the sample compared to the dispersion law of free electrons.

Extended fine structure (EFS) of secondary electron (SE) spectra has been detected beyond the high-energy (∼720 and ∼840 eV) LVV Auger lines in iron and nickel. Two mechanisms of its formation are considered: 1) direct transitions of electrons to the final state p according to Fermi’s “golden rule” and 2) second-order processes of auto-ionization type, passing through excitation of a core electron to an intermediate state q of the continuum with subsequent filling of the hole formed during this process by a valence electron and transition of the electron from the intermediate state q to the final state p. Interference of the direct wave with the wave reflected from neighboring atoms generates the EFS both in the final (p) and in the intermediate (q) state with two different periods determined by the wave numbers p and q. Comparison of calculated extended fine structures with the experimentally observed ones leads to the conclusion that the structure is formed by second-order auto-ionization processes.