Interpretation of KL2,3L2,3 radiative auger thresholds in metals and semiconductors

High-resolution measurements of the KL_2,3L_2,3 radiative Auger edge in Mg and Al are reported. The theory of soft X-ray absorption thresholds by Flynn and Lipari is modified to account for the KL_2,3L_2,3 threshold energies. The calculated energies are in excellent agreement with the experimental results including previous measurements on Si.     

SiO2 surface defect centers studied by AES

A theoretical model is proposed on how a Si dangling bond associated with an oxygen vacancy on a SiO₂ surface (E_s′ center) should be observed by Auger electron spectroscopy (AES). The Auger electron distribution N_A(E) for the L₂₃VV transition band is calculated for a stoichiometric SiO₂ surface, and for a SiO_x surface containing Si-(e^?O₃) coordinations. The latter is characterized by an additional L₂₃VD transition band, where D is the energy level of the unpaired electron e^?. The theoretical N_A(E) spectra are compared with experimental N(E) spectra for a pristine, and for an electron radiation damaged quartz surface. Agreement with the theoretical model is obtained if D is assumed to lie ≈2 eV below the conduction band edge. This result shows that AES is uniquely useful in revealing the absolute energy level of localized, occupied surface defect states. As the L₂₃VD transition band (main peak at 86 eV) cannot unambiguously be distinguished from a SiSi₄ coordination L₂₃VV spectrum (main peak at 88 eV), supporting evidence is presented as to why we exclude a SiSi₄ coordination for our particular experimental example. Application of the Si-(e^?O₃) model to the interpretation of SiO₂Si interface Auger spectra is also discussed.     

Solid-state shifts in the L3M4,5M4,5 Auger spectra of the elements Cu TO Se

The kinetic-energy shifts between atomic and solid-state L₃M_4,5M_4,5 Auger electron spectra of Cu, Zn, Ga, Ge, As, and Se are determined with the aid of semiempirically calculated atomic and experimental solid-state Auger energies. The shift values are calculated by applying the thermochemical model to the Auger process. Good agreement is found between the calculated and experimental values.     

On the intensity ratio I(KL2,3L2,3)/I(KL1L1) of the auger carbon lines in series of d-metal carbides

C KVV Auger spectra have been obtained for series of nd-metal carbides (n = 3,4 and 5). The numbers of electrons participating in the C KVV Auger processes for these compounds are estimated by considering the intensity ratio I(KL_2,3L_2,3)/I(KL₁L₁). It is concluded that to explain the high intensities of the KL_2,3L_2,3 Auger lines for the d-metal carbides, it is necessary to consider the participation of conduction-band electrons (and/or interatomic transitions) in the C KVV Auger decay process.     

Theory of spin-polarized Auger electron spectra in ferromagnetic materials with particular attention to L23M23M23 Auger spectrum in Fe83B17

Spin polarization of L₂₃M₂₃M₂₃ Auger electrons from ferromagnetic Fe₈₃B₁₇ is calculated with a simplified model, and compared with recent experiments. The Auger electron spectrum has two peaks, corresponding to the singlet and triplet final states of a 3p hole pair. It is shown that the spin polarizations of the singlet and triplet peaks, respectively, originate from the exchange interaction between 3d and 2p spins and that between 3d and 3p spins. Similar effects are expected to be observed commonly for L₂₃M₂₃M₂₃ Auger electrons from various ferromagnetic materials including transition elements.     

M4,5N4,5N4,5 auger electron spectrum of Ba metal

The Al Kα excited M_4,5N_4,5N_4,5 Auger spectrum of Ba has been measured from the metallic sample evaporated on a Ag substrate. The spectrum has been decomposed into individual line components after the background subtraction. The decomposed spectrum has been compared with the theoretical spectrum calculated for the 4d^?2 final state configuration in the mixed coupling scheme applying jj-coupling for the initial state and intermediate coupling for the final state. The most prominent structure of the spectrum shows the two 4d-hole coupling, but the structure which is caused by the Auger transitions M_,45N_2,3V has also been observed. The screening of the core holes in Ba metal seems to be produced by (5d6s) electrons. The simple excited atom model HF-calculations give an Auger kinetic energy shift (metal-free atom) of 16.7 eV, which is comparable to the experimental value 14–18 eV.     

The L1L2,3V Auger transition in Si

The L₁L_2,3V Auger transition in silicon has been analyzed. No substantial differences are observed in the comparison with the deconvolution of the L_2,3VV Auger spectrum. Comparison is also made with other valence band spectroscopies. It is concluded that L₁L_2,3V transition has a band character.     

Photoemission spectra of ion implanted amorphous Si and Fe84B16 metal glass

Ultraviolet photoemission spectra of Si and Fe₈₄B₁₆ were measured in amorphous and crystalline states at 10.2 eV photon energy. The surface compositions were determined by Auger electron spectroscopy. The samples were prepared by ion implantation, evaporation and by splat-cooling. The photoelectron spectra of amorphous phases are found to be different from those of the crystalline for both materials and all preparation methods. The UPS of amorphous Si and Fe₈₄B₁₆ metal glass have some common characteristics.     

Study of L2,3M4,5M4,5 Auger spectra of Zn and Cu in molecular ZnCl2 and (CuCl)3 vapours

L_2,3M_4,5M_4,5 Auger electron spectra of Zn and Cu have been measured in molecular ZnCl₂ and (CuCl) ₃ vapours. The spectra have been analyzed and compared with the corresponding free-atom spectra. It is found that the main features of the spectra are atomic-like. The energies are shifted by 0.55 eV in ZnCl₂ and by 3.2 eV in (CuCl)₃ towards higher kinetic energy compared with the corresponding free-atom spectra. For the intensity ratios between the L₃ and L₂ groups, the values 2.8 and 3.7 are obtained for Zn and Cu, respectively. These intensity ratio, together with energy considerations based on free-atom Dirac—Fock calculations and observed Auger shifts, indicate that the L₂L₃M_4,5 Coster—Kronig process is energetically possible in (CuCl)₃ molecular clusters but not in ZnCl₂. The satellite structure in the spectra studied also supports this conclusion.     

Si3N4/Si表面Si生长过程的扫描隧道显微镜研究

利用原位扫描隧道显微镜和低能电子衍射分析了Si的纳米颗粒在Si₃N₄/Si(111)和Si₃N₄/Si(100)表面生长过程的结构演变.在生长早期T为350—1075K范围内,Si在两种衬底表面上都形成高密度的三维纳米团簇,这些团簇的大小均在几个纳米范围内,并且在高温退火时保持相当稳定的形状而不相互融合.当生长继续时,Si的晶体小面开始显现.在晶态的Si₃N₄(0001)/S 关键词： 氮化硅 扫描隧道显微镜 纳米颗粒     

Surface oxidation study of Fe67Co18B14Si1 metallic glass using Auger electron spectroscopy

Surface composition and depth profile of native oxide on Fe₆₇Co₁₈B₁₄Si₁ metallic glass has been investigated using Auger electron spectroscopy. The native oxide is compared with chemisorbed oxygen on the cleaned surface. Results indicate that boron segregates on the surface in the presence of oxygen. The low energy L₂₃M₄₅M₄₅ peak of iron in metallic glass is compared with that in crystallized sample and pure iron foil.     

Properties of the SiO2/SiC interface investigated by angle resolved studies of the Si 2p and Si 1s levels and the Si KLL Auger transitions

Angle resolved photoemission studies of the Si 2p and Si 1s core levels and the Si KL_2,3L_2,3 Auger transitions from SiO₂/SiC samples are reported. Most samples investigated were grown in situ on initially clean and well ordered √3×√3 reconstructed 4H-SiC(0 0 0 1) surfaces but some samples were grown ex situ using a standard dry oxidation procedure. The results presented cover samples with total oxide thicknesses from about 5 to 118 Å. The angle resolved data show that two oxidation states only, Si⁺¹ and Si⁺⁴, are required to explain and model recorded Si 2p, Si 1s and Si KLL spectra.The intensity variations observed in the core level components versus electron emission angle are found to be well described by a layer attenuation model for all samples when assuming a sub-oxide (Si₂O) at the interface with a thickness ranging from 2.5 to 4 Å. We conclude that the sub-oxide is located at the interface and that the thickness of this layer does not increase much when the total oxide thickness is increased from about 5 to 118 Å.The SiO₂ chemical shift is found to be larger in the Si 1s level than in the Si 2p level and to depend on the thickness of the oxide layer. The SiO₂ shift is found to be fairly constant for oxides less than about 10 Å thick, to increase by 0.5 eV when increasing the oxide thickness to around 25 Å and then to be fairly constant for thicker oxides. An even more pronounced dependence is observed in the Si KLL transitions where a relative energy shift of 0.9 eV is determined.The relative final state relaxation energy ΔR(2p) is determined from the modified Auger parameter. This yields a value of ΔR(2p)=−1.7 eV and implies, for SiO₂/SiC, a “true” chemical shift in the Si 2p level of only ≈0.4 eV for oxide layers of up to 10 Å thick.     

Effect of Ni interlayer on stress level of CoSi2 films in Co/Ni/Si(1 0 0) bi-layered system

The effect of Ni interlayer on stress level of cobalt silicides was investigated. The X-ray diffraction patterns (XRD) show that low temperature formation of Co_1−xNi_xSi₂ solid solution was obtained while Ni interlayer was present in Co/Si system, which was confirmed by Auger electron spectrum (AES) and sheet resistance measurement. XRD was also used to measure the internal stress in CoSi₂ films by a 2θ_ψ − sin²ψ method. The result shows that the tensile stress in CoSi₂ films evidently decreased in Co/Ni/Si(1 0 0) system. The reduction of lattice mismatch, due to the presence of Ni in Co_xNi_1−xSi₂ solid solution, is proposed to explain this phenomenon.     

AES and factor analysis study of silicide growth at the Pd/c-Si interface

We have measured the evolution of a palladium/silicon interface under consecutive annealing periods, performed at 200°C in UHV conditions. The interface was analyzed by means of Auger electron spectroscopy combined with factor analysis applied in a sequential way. We found that silicide appears only after annealing and evolves until all the palladium is consumed. A silicon compound different from silicide, identified as Pd_xSi with x<2 is found at the interface Pd/Si and Pd₂Si/Si, before and after annealing respectively.     

Intensity ratios of the KL1L1, KL23L23 oxygen Auger lines in different compounds

A simple model is proposed to interpret the relative intensities of the KLL oxygen Auger lines of several compounds. The basic assumption is that the intensity ratios depend on the atomic charges of the L₁ and L₂₃ orbitals localized at the oxygen site. The appropriate atomic charges can be calculated after Pauling's scale of electronegativity. The theoretical intensity ratios are compared with experimental results of different authors.     

The M4,5- VV Auger spectrum of silver: An interpretation based on quasi-atomic final states

The M_4,5- VV Auger spectrum of silver has been studied under high-resolution conditions. The relative energies and intensifies of the Auger lines calculated for a 4 d⁸ final state configuration account well for the experimental spectrum. This quasi-atomic behaviour is due to the fact that the effective two-hole Coulomb interaction is larger than the bandwidth. The influence of the solid state on the width of the Auger lines is discussed.     

The Rotational Spectra of H2CCSi and H2C4Si

The microwave rotational spectra of two singlet chains H₂CCSi and H₂C₄Si, have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. Following detection of the singly substituted rare isotopic species and D₂CCSi, an experimental structure (r₀) has been determined to high accuracy for H₂CCSi by isotopic substitution. In addition, the rotational transitions of the ²⁹Si and the two ¹³C isotopic species of H₂CCSi exhibit nuclear spin-rotation hyperfine structure. The component of the spin-rotation tensor along the a-inertial axis is abnormally large for each of these isotopic species, especially for that with ²⁹Si, where the magnitude of C_aa is in excess of 700 kHz.     

A comparative study of surface oxidation behaviour of amorphous and crystallized Ni36Fe32Cr14P12B6 metallic glass using Auger Electron Spectroscopy

Native oxide and in situ oxidation of amorphous Ni₃₆Fe₃₂Cr₁₄P₁₂B₆ have been investigated at room temperature using Auger Electron Spectroscopy. The Ni₃₆Fe₃₂Cr₁₄P₁₂B₆ sample has been annealed as ～ 800 K in UHV and its oxidation behaviour has been studied at room temperature. A comparison of in situ oxidized amorphous and crystallized samples has been carried out.     

Theoretical modeling of excitation and de-excitation processes of Er in SiO2 with Si nanocrystals

We construct the theory of carriers confined in Si quantum dots with finite energy barriers for electrons and holes in the framework of the multiband effective mass theory. We apply this theory for theoretical modeling of the excitation of erbium inside and outside of Si nanocrystals in SiO₂ matrix due to the Auger process induced by the recombination of a confined electron-hole pair as well as the intraband transitions of “hot” confined carriers. Auger de-excitation processes of the Er³⁺ ion leading to the quenching of erbium luminescence are discussed as well.     

Crystal chemistry of layered carbide, Ti3(Si0.43Ge0.57)C2

 The crystal structure of a layered ternary carbide, Ti₃(Si_0.43Ge_0.57)C₂, was studied with single-crystal X-ray diffraction. The compound has a hexagonal symmetry with space group P6₃/mmc and unit-cell parameters a=3.0823(1) Å, c=17.7702(6) Å, and V=146.21(1) Å³. The Si and Ge atoms in the structure occupy the same crystallographic site surrounded by six Ti atoms at an average distance of 2.7219 Å, and the C atoms are octahedrally coordinated by two types of symmetrically distinct Ti atoms, with an average C-Ti distance of 2.1429 Å. The atomic displacement parameters for C and Ti are relatively isotropic, whereas those for A (=0.43Si+0.57Ge) are appreciably anisotropic, with U₁₁ (=U₂₂) being about three times greater than U₃₃. Compared to Ti₃SiC₂, the substitution of Ge for Si results in an increase in both A-Ti and C-Ti bond distances. An electron density analysis based on the refined structure shows that each A atom is bonded to 6Ti atoms as well as to its 6 nearest neighbor A site atoms, whether the site is occupied by Si or Ge, suggesting that these bond paths may be significantly involved with electron transport properties.