Auger Electron Spectroscopy Spectra Research Articles

Chemical structural characterization of pyrolyzed and subsequently ion-implanted poly(acrylonitrile)

Infrared (IR), Auger electron spectroscopy (AES) and X-ray photoelectron spectra (XPS) of pristine, pyrolyzed, and ion-implanted poly(acrylonitrite) (PAN) samples were obtained in order to correlate the structural changes accompanying pyrolysis and implantation with the electrical properties of the respective PAN products. The results show that PAN is first converted to a polyconjugated heterocyclic ladder structure at a temperature of 435 °C and then to a graphite-like structure at temperature above 750 °C. Pyrolysis studies took place in a temperature range of 350–750 °C. IR studies showed that upon heat treatment at 435 °C, major structural changes occur as indicated by the complete disappearance of the nitrile and methylene absorption bands and the formation of new bands. The degree of conjugation in pyrolyzed PAN can be selectively controlled by the proper choice of the heat treatment temperature. From the studies, ion implantation causes extensive nitrogen depletion and the nitrogen chemical state in the implanted sample is different from that found in the pyrolyzed materials. Upon ion implantation, the component assigned to the nitrogen in a sigma bonding state (401.27 eV) increased in intensity (46%) relative to the intensity (27%) of the component for which nitrogen is in a hetroaromatic structure. Both AES and XPS analysis showed the variation of C:N ratio as a function of heat treatment.

Why are the band-like states suppressed in the M 3–M 4,5M 4,5 super Coster–Kronig electron spectrum of Cu metal compared to those in the L 3–M 4,5M 4,5 Auger electron spectrum?

The relative spectral intensity of the band-like two M 4,5-hole state to the atomic-like localized one is much suppressed in the coincidence M 3–M 4,5M 4,5 super Coster–Kronig (sCK) electron spectrum of Cu metal compared to the one in the coincidence L 3–M 4,5M 4,5 Auger electron spectroscopy (AES) spectrum. The M 3-hole lifetime width of Cu metal is calculated by an ab initio atomic many-body theory (the extended relaxed core random phase approximation with exchange). The calculated M 3-hole lifetime width of Cu metal agrees well with the experimental one. The M 3–M 4,5M 4,5 sCK decay width of Cu metal decreases much with delocalization of the two M 4,5 holes in the sCK final state, whereas the Auger decay width is fairly independent of localization and delocalization of the two M 4,5 holes in the Auger final state. Thus, the relative spectral intensity of the band-like state is much suppressed in the coincidence M 3–M 4,5M 4,5 sCK-electron spectrum of Cu metal compared to the one in the coincidence L 3–M 4,5M 4,5 AES spectrum.

Degradation of commercial Gd2O2S:Tb phosphor

AbstractThe degradation of Gd2O2S:Tb phosphor was studied with Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL). The surface reactions were monitored with AES while the light output was measured with a PC2000‐UV spectrometer. The CL of the Gd2O2S:Tb was excited with a 2 keV energy electron beam with a beam current density of 26 mA/cm2. The CL and AES were measured simultaneously while the sample was bombarded with the electrons in an oxygen atmosphere. A comparison between the low energy peaks of the AES spectra before and after degradation showed significant differences in the shape of the different peaks. A linear least squares (LLS) method was applied to resolve the peaks. Elemental standards from Goodfellow were used in conjunction with the measured data to subtract the S and Gd peaks. A direct correlation between the surface reactions and the CL output was found. The CL decreased while the S was removed from the surface during electron bombardment. A new non‐luminescent surface layer that formed during electron bombardment was responsible for the degradation in light intensity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of relaxation and decay of a charge transfer shakeup satellite on Auger-electron spectroscopy spectra and Auger-photoelectron coincidence spectroscopy spectra of adsorbates

An electron excited to an unoccupied part of adsorbate–substrate hybrid states in a chemisorbed molecule by a resonant core electron excitation or charge transfer (CT) shakeup may delocalize on time scale of core-hole decay so that the excited core-hole state relaxes partly or completely to a fully relaxed one. The Auger decay of the fully relaxed core-hole state via the relaxation of the excited one introduces an additional feature in the resonant Auger-electron spectroscopy (RAES) spectrum and the AES spectrum. However, the additional feature in the RAES spectrum is a normal AES spectrum by decay of the fully relaxed core-hole state, whereas the one in the AES spectrum is the AES spectrum by decay of the fully relaxed core-hole state broadened by the photoelectron spectroscopy (PES) CT shakeup satellite weighted by the branching ratio of the relaxation width. The discrepancies between the AES spectrum measured at high above the ionization threshold and the additional feature in the RAES spectrum consist of the symmetric-like part by the decay of the fully relaxed core-hole state via the relaxation of the CT shakeup state and the asymmetric part by the direct decay of the shakeup states. The asymmetric part increases with a decrease in the hybridization strength. This explains the variation with the hybridization strength in the discrepancies between the RAES spectra and the AES spectra of chemisorbed molecules such as CO/Ni, CO/Cu and CO/Ag. A comparison of the singles PES spectrum with the one measured in coincidence with the AES main line of a selected kinetic energy (KE) provides the delocalization rate of the excited electron in the CT shakeup state as a function of photoelectron KE. The coincidence measurement to obtain the partial singles PES spectrum is discussed.

The participant Coster–Kronig preceded Auger transition in the resonant L 2,3-M 2,3V Auger electron spectrum of Ti metal

The L 2,3-M 2,3V resonant Auger electron spectroscopy (RAES) spectrum of Ti metal measured by Le Fêvre et al. [P. Le Fêvre, J. Danger, H. Magnan, D. Chandesris, J. Jupille, S. Bourgeois, M.-A. Arrio, R. Gotter, A. Verdini, A. Morgante, Phys. Rev. B69 (2004) 155421] is analyzed in the light of relaxation and decay of the resonantly excited L 2,3-hole states. The relaxation time of the resonantly excited L 2,3-hole state to the fully relaxed (screened) one is much shorter than the L 2,3-hole Auger decay time, whereas the participant Coster–Kronig (CK) decay time of the resonantly excited L 2-hole state to the fully relaxed L 3-hole state at the L 2 resonance is as short as the relaxation time of the resonantly excited L 2-hole state to the fully relaxed one. The excited electron is predominantly either rapidly decoupled from the L 2,3-hole decay or annihilated by the participant CK decay. Thus, near the L 2,3 edges the L 2,3-M 2,3V RAES spectral peak appears at constant kinetic energy. The L 2,3-M 2,3V RAES spectrum shows a normal L 2,3-M 2,3V Auger decay profile not modulated by the density of empty d states probed by the resonant excitation. Not only the relaxation time but also the participant CK decay time depends on photon energy because they depend on the density of empty d states probed by the resonant excitation. As a result, the L 2,3 X-ray absorption spectroscopy spectral line broadening depends on photon energy.

Characteristic Microstructure and Grain Boundary Motion in Secondary Recrystallization of Fe-3%Si Alloys

The microstructure of Fe-3 mass% Si alloys before secondary recrystallization has been characterized by analyzing precipitates and grain boundary segregated elements. The samples used were mainly sheets of Fe-3%Si alloys containing manganese, sulfur, aluminum, nitrogen and tin, which were decarburized and annealed up to secondary recrystallization. Grain boundary segregation in primarily recrystallized samples was studied using Auger electron spectroscopy (AES), and precipitates were analyzed using transmission electron microscopy (TEM) with an energy dispersive X-ray spectrometer (EDX). AES spectra showed that tin and nitrogen were enriched on grain boundaries in the Fe-3 mass% Si alloys. TEM/EDX analysis showed that the morphology and distribution of the fine precipitates such as manganese sulfide and aluminum nitride were influenced by addition of tin. The characteristic structure formed by secondary recrystallization of grain oriented silicon steel is considered to be influenced by the fine precipitates and segregation of a small amount of elements, as the abnormal motion of grain boundaries of the silicon steel was correlated with the precipitation and segregation of the alloying elements.

Many-body effect in the resonant Ti L 23–M 23V Auger-electron spectroscopy spectra and Auger-photoelectron coincidence spectroscopy spectra of Ti oxides

Recently Danger et al. [J. Danger, H. Magnan, D. Chandesris, P. Le Fèvre, S. Bourgeois, J. Jupille, A. Verdini, R. Gotter, A. Morgante, Phys. Rev. B 64 (2001) 045110] and Le Fèvre et al. [P. Le Fèvre, J. Danger, H. Magnan, D. Chandesris, J. Jupille, S. Bourgeois, M.-A. Arrio, R. Gotter, A. Verdini, A. Morgante, Phys. Rev. B 69 (2004) 155421] showed the absence of resonant Raman scattering feature in the Ti L 23–M 23V resonant Auger-electron spectroscopy (RAES) spectra of Ti oxides measured across the Ti 2p edges. They attributed the absence to the covalent character of the Ti–O bond which allows an effective delocalization of 3d electrons. It is shown by a many-body theory that when the time scale of relaxation of the resonantly excited core-hole state to the fully relaxed core-hole state is much shorter than that of core-hole decay, any sizeable Raman scattering is absent in the RAES spectra measured across the Ti 2p edges. The relaxation width depends on the hybridization strength and the charge transfer (CT) energy between the two states. The L 2–L 3V Coster–Kronig (CK) decay widths of TiO 2 and TiO 2− x are determined from the L 23–M 23V Auger-photoelectron coincidence spectroscopy (APECS) spectra reported in the aforementioned papers. They are about 0.18 and 0.35 eV, respectively. The CK-decay width in the reduced Ti oxide increases compared to that of TiO 2 in rutile because of filling of the 3d states just below the Fermi level in the former.

Many-electron effect in the resonant Auger electron spectroscopy spectra of adsorbates

It is shown by a many-body theory that a resonantly excited core hole state in a chemisorbed molecule such as CO/Ni, CO/Pd, and CO/Pt relaxes to a fully relaxed one, i.e., the ionized core hole state of the smallest binding energy observed by photoelectron spectroscopy, before the core hole decays so that the resonant Auger electron spectroscopy (RAES) spectrum shows the normal Auger decay spectrum. It is shown by a many-body theory that the Auger peaks on the higher kinetic energy (K.E.) side in the RAES or AES spectrum, i.e., so called back-bonding peaks, are the two-hole states consisting of a valence hole and a hole in the adsorbate–substrate hybrid states below the substrate Fermi level. The latter hole is the change in the density of the hybrid states occupied by the screening electron from the core hole state to the valence-hole state. The difference between the back-bonding peak energy and the single valence-hole energy provides an important information about the change in the density of the hybrid states occupied by the screening electron from the core hole state to the valence-hole state. The difference between the RAES spectrum measured at the resonance energy and the AES spectrum measured at far above the ionization limit shows the competition between relaxation and decay of shakeup satellites such as the charge transfer (CT) shakeup. The relaxation rate of the CT shakeup state can be determined by Auger-photoelectron coincidence spectroscopy (APECS).

Many-electron effect in the Pd M 45-VV APECS spectra of Pd/Ag(1 0 0) dilute surface alloys

The Pd M45-VV Auger-photoelectron coincidence spectroscopy (APECS) spectra of Pd/Ag(1 0 0) dilute surface alloys measured by Arena et al. [D.A. Arena, R.A. Bartynski, R.A. Nayak, A.H. Weiss, S.L. Hulbert, M. Weinert, Phys. Rev. Lett. 91 (2003) 176403] are analyzed. MX is the atomic shell Mx. In Pd/Ag dilute surface alloys the lifetime of a valence hole created by the M4-M5V Coster-Kronig (CK) transition or by the M45 shakeup is comparable to that of the M45 hole, while in Pd metal the former lifetime is shorter than the latter one. Thus, both the M4-M5(V)-VV transition and the M4-M5V-VVV transition contribute to the Auger-electron spectroscopy (AES) spectrum measured in coincidence with the M4 photoelectrons. This is because the Pd DOS at the Fermi level at the surface becomes lower compared to the bulk. An ab-initio atomic many-body calculation (the extended random phase approximation with exchange (ERPAE)) of the M4-M5V CK-transition rate of Pd atom shows that the localization of the valence hole in the M5V two-hole state increases the CK rate by a factor of about two. As the CK transition occurs near the threshold, the effect on the CK rate by the lifetime of the valence hole in the M5V state is substantial. This should also contribute to the M4-M5V CK rate increase in the surface alloys. We discussed how to determine the relaxation rate of the M5V two-hole state to the M5-hole state and the M4-M5V CK-transition rate by the coincidence photoelectron spectroscopy.

Competition between relaxation and decay of a core-level electron ionized state in a charge transfer system

In a weak charge transfer (CT) system, such as an adsorbate–substrate system a core-level electron ionized state in an adsorbate observed by photoelectron spectroscopy (PES) as the smallest binding energy state, may be a metastable state. On time scale of core–hole decay it may relax further to the most stable state by CT core–hole screening via transfer of an electron from the substrate to an unoccupied adsorbate discrete level pulled down below the Fermi level of the substrate by an attractive core–hole potential. The latter state is a CT shakedown state, which is not observable by PES but its presence is visible in a decay spectrum, such as Auger-electron spectroscopy (AES) spectrum. The CT shakedown state resembles a resonantly excited core–hole state lying below the core–hole state of the smallest binding energy. If this is so, the AES spectrum measured at far above the core-level electron ionization threshold has then an additional spectral feature, which resembles the autoionization spectrum by the core–hole decay of the resonantly excited core–hole state. Such an example is the N 1s AES spectrum of N 2 molecule physisorbed on graphite reported by Björneholm et al. [Q. Björneholm, A. Nilsson, A. Sandell, B. Hernnäs, N. Mårtensson, Phys. Rev. Lett. 68 (1992) 1892]. The competition between relaxation and core–hole decay of a core-level electron ionized state in a weak CT system is formulated by a many-body theory and discussed. The present theory provides a theoretical foundation of the interpretation by Björneholm et al. They determined the CT time from the intensity ratio of the AES spectrum by the decay of the CT shakedown state to that by the decay of the core–hole state observed by PES as the smallest binding energy state. However, the CT time cannot be determined, unless the branching ratio of the former decay rate is equal to that of the latter one.

Transition from the radiationless resonant Raman scattering to the normal Auger decay in a charge transfer system

The transition from the radiationless resonant Raman scattering to the normal Auger decay in resonant Auger-electron spectroscopy (RAES) spectra of charge transfer (CT) systems is discussed by treating the relaxation and the core-hole decay of the excited core-hole state on the same footing by a many-body theory. When the resonantly excited electron remains at the excited atomic site during the core-hole decay, the RAES spectrum shows the characteristic feature of the resonant Auger–Raman effect, whereas when the excited electron has been transferred from the atomic site before the core-hole decays, the RAES spectrum shows the normal Auger decay. The present theory supports the interpretation of the variation with photon energy of the intensity ratio of the latter spectrum to the former one in the RAES spectrum by the Ar 2p → 4s resonance of Ar atoms adsorbed on Ru(0 0 1) surface reported by Keller et al. [C. Keller, M. Stichler, G. Comelli, F. Esch, S. Lizzit, D. Menzel, W. Wurth, Phys. Rev. B 57 (1998) 11951]. The transition from the radiationless resonant Raman scattering to the normal Auger decay in the RAES spectrum of CuO reported by Finazzi et al. [M. Finazzi, G. Ghiringhell, O. Tjernberg, Ph. Ohresser, N.B. Brookes, Phys. Rev. B 61 (2000) 4629] is discussed in terms of the relaxation of the resonantly excited core-hole state to the core-electron ionized main-line state by the hole–particle excitations. The merging of the resonant Raman–Auger-electron kinetic energy into the normal one about 2 eV above the absorption maximum in Cu 2O reported by Finazzi et al. [M. Finazzi, G. Ghiringhell, O. Tjernberg, Ph. Ohresser, N.B. Brookes, Phys. Rev. B 61 (2000) 4629] is explained in terms of the change in the characteristics of the screening electron in the two-hole final state. The Ti L 23-M 23V RAES spectra of TiO 2 and TiO 2− x are also analyzed.

Many-electron effect in the Si K-LL resonant Auger-electron spectroscopy spectra of the Si delta layer in GaAs

The Si K-LL resonant Auger-electron spectroscopy (RAES) spectra of silicon delta dopped layers in GaAs with very thin capping layers show both normal Auger decay and resonant Auger decay, when the core-level electron is excited to the conduction band. The resonant Auger peak kinetic energy (KE) shows no dispersion with photon energy, except when excited by the highest energy photons [M.D. Jackson, J.M.C. Thornton, D. Lewis, A. Robinson, M. Fahy, A. Aviary, P. Weightman, Phys. Rev. B71 (2005) 075313]. The RAES spectra are analyzed using a many-body theory. The presence of resonant Auger decay and no dispersion of resonant Auger peak KE with photon energy is explained in terms of the relaxation of a metastable excited core-hole state to a stable one on the time scale of core-hole decay. The excited electron in the conduction band either delocalizes rapidly leaving the ionized Si to decay by a normal Auger decay or drops to a state localized in the Si delta layer before the core-hole decays so that the RAES spectrum has both normal Auger decay and resonant Auger decay. As a result of the relaxation, the resonant Auger peak KE does not show any dispersion with photon energy. The variations with photon energy of the normal or resonant Auger peak intensity, KE, and width are explained in a consistent manner by a many-body theory.

Effect of competition between relaxation and decay on the Auger-photoelectron coincidence spectroscopy (APECS) spectra of Pd metal

The high-resolution coincidence M45 photoelectron spectra and coincidence M45-VV Auger-electron spectroscopy (AES) spectra of Pd metal reported by Butterfield et al. [M.T. Butterfield, R.A. Bartynski, S.L. Hulbert, Phys. Rev. B66 (2002) 115115] are analyzed by a many-body theory. MX is the atomic shell Mx. The Auger-photoelectron coincidence spectroscopy (APECS) spectra provide the evidence of the rapid delocalization of the valence hole created in Pd metal either by the M45 shakeup or by the M4-M5V Coster-Kronig transition before the M45-hole or the M5-hole decays. The M45 shakeup state relaxes to the M45 main-line state before the M45-hole decays. As a result, the singles (noncoincidence) M45-VV AES spectral line shape becomes the sum of the intrinsic coincidence M5-VV AES one and the intrinsic coincidence M4-VV one, weighted by a M5-VV to M4-VV ratio of 1.0:0.7, which agrees well with the theoretical M45-level ionization cross section ratio of 1.0:0.69. A high-resolution APECS can reveal the core-hole dynamics in much more detailed manner than conventional noncoincidence techniques.

Many-electron effect in the resonant L 23-M 23V Auger-electron spectrum of Ti metal

Above the L23 absorption edge the L 23-M 23V resonant Auger-electron spectroscopy (RAES) spectrum of Ti metal shows a normal L 23-M 23V Auger decay spectrum at a constant kinetic energy (K.E.). Here LX and MY are the atomic shells L x and M y, respectively. Apart from a weak spectral feature of the L2-M23V Auger transition appearing around the L2 edge, the RAES spectra of Ti meal show a very little difference between the L2 and L3 regions [P. Le Fèvre, J. Danger, H. Magnan, D. Chandesris, J. Jupille, S. Bourgeois, M.-A. Arrio, R. Gotter, A. Verdini, A. Morgante, Phys. Rev. B69 (2004) 155421]. It is shown that the time scale of relaxation of the resonantly excited L23-hole state to the L23-electron ionized state is much shorter than that of the L23-hole decay so that the L 23-M 23V RAES spectrum of Ti metal resembles much the normal L 23-M 23V Auger decay spectrum. The relaxation of the resonantly excited L23-hole state to the fully relaxed L23-hole state before the L23-hole decays, explains the extra width which is the primary cause of the discrepancy between the experimental high resolution near edge X-ray absorption spectroscopy (XAS) spectrum of Ti metal and the one calculated by the particle–hole Green's function including the Coulomb exchange interaction between the 2p hole and the 3d electron. The time scale of relaxation of the L3V two-hole state created by the L2-L3V Coster–Kronig (CK) decay to the single L3-hole state is much shorter than that of the L3-hole decay so that the L2-L3V-L3-M23V CK preceded Auger decay spectrum resembles much the L3-M23V Auger decay one.

Many-body effect in the N 23-VV Auger-photoelectron coincidence spectroscopy (APECS) spectra of Ag metal

The coincidence N23-VV Auger-electron spectroscopy (AES) spectra and N23 photoelectron spectroscopy (PES) spectra of Ag metal are analyzed. Here N X is the notation for atomic shell N x ( X = 2, 3). The band-like feature in the coincidence N23-VV AES spectra is much more intense than that in the coincidence M45-VV ones because the potential in the delocalized two-hole state is less attractive than that in the localized one. The partial N23-VV super Coster–Kronig (sCK) transition rate depends critically on both the final-state potential and the sCK-electron kinetic energy (KE) because the KE is low, whereas the partial M45-VV Auger-transition rate is fairly independent of them because the KE is very high. As a result, the partial sCK-transition rate to the band-like state is enhanced compared to that to the atomic-like localized state. The low KE tail in the coincidence N23-VV AES spectra which is likely due to the sCK transition involving more than two electrons, is more enhanced than that in the coincidence M45-VV ones. This is due to the enhancement of the partial sCK-transition rate by the presence of extra holes in the final state. The sharp peaks of small intensity on the lower KE side of the main line in the coincidence N2 PES spectrum are tentatively attributed to the shakeup satellites.

Many-body effect in Auger-electron spectra by participant Auger transitions of a core-hole satellite

A discrete two-hole one-particle (2hlp) shakeup/down state can decay either by spectator Auger transitions or by participant Auger transitions. The 2hlp state created by the participant Auger transition of the 2hlp shakeup/down state can be the same as the one created by the Auger transition of the 1h state. The participant Auger transition by which the electron excited by the shakeup/down fills the core hole, can be dominant. If this is so, when the two discrete core-hole states couple to the same continuum and their separation energy is smaller than or comparable to the core-hole lifetime width, there is a possibility of an interference between the Auger transition of the 1h state and the participant Auger transition of the 2hlp state. The screening of the Auger electron emission of the 1h state via the participant Auger transition of the 2hlp state leads to a pronounced interference in the Auger-electron spectroscopy (AES) spectrum. Because the screening function behaves like a Fano resonance. As the function is critically energy dependent, the photoelectron spectroscopy (PES) line peaks do not coincide with the AES ones, when the latter ones are shifted by the 2h final-state energy. In such a case, the PES line peak measured in coincidence with the AES one is shifted from the noncoincidence PES one. When the photoelectron is collected in coincidence with the Auger electron (or X-ray fluorescence) for a selected decay channel, i.e., when the doubly differential photoionization cross section of the photoelectron and the Auger electron (or X-ray fluorescence) being emitted and collected in coincidence is integrated over the Auger-electron kinetic energies (or X-ray fluorescence energies) of the selected decay channel and summed for the final states of the selected decay channel, the photoelectron spectrum is the noncoincidence (singles) photoelectron spectrum weighted by the branching ratio of the partial decay rate of the selected decay channel so that we can extract the screening function by comparing the coincidence photoelectron spectrum with the singles (noncoincidence) photoelectron one.

Sampling and analysis of particles generated in contact start/stop-mode of a hard disk drive by using a particle sampler

Particle contamination must be controlled to increase the storage capacity of a hard disk drive (HDD) as the flying height of the slider decreases. In the primary steps of particle contamination control, particles are precisely detected and analyzed. To carry out these steps, many researchers have used sampling methods. In this paper, we newly designed a particle sampler and evaluated the performance of the sampler. This sampler can collect particles by the applied electric field, by the impaction of particles, and by Brownian diffusion onto the sampling plate. We tested the performance of our sampler in terms of the parameters that affect the sampling efficiency of the particle sampler; sampling airflow rate, particle size, and externally applied electric field. The maximum sampling efficiency of unipolarly charged particles whose sizes ranged from 50 to 400 nm was about 90%. Also, we sampled particles generated during 20 contact start/stop cycles (CSS) of the HDD by using the particle sampler and analyzed the sampled particles by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The SEM images showed that the sizes of the particles decreased and the number of sampled particles increased as the disk rotational speed increased. The AES spectrum showed that the sampled particles were composed of P, C, Ni and Al, which are the components of the disk materials. Therefore, we believed that the generated particles originated from the disk surface. To determine the overall sampling efficiency of the particle sampler, particles generated in the HDD were counted at the inlet and outlet of the sampler. The overall sampling efficiency increased with increasing applied voltage and disk rotational speed. The maximum overall sampling efficiency of the particles generated in the HDD was about 70% when the applied voltage and disk rotational speed were 0.5 kV and 9,600 rpm, respectively.

SiC pore surfaces: Surface studies of 4H–SiC(11¯02) and 4H–SiC(1¯102¯)

The morphology and atomic structure of 4H–SiC(11¯02) and 4H–SiC(1¯102¯) surfaces, i.e., the surfaces found in the triangular channels of porous 4H–SiC, have been investigated using atomic force microscopy, low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). After hydrogen etching, the surfaces show steps parallel and perpendicular to the c axis, yet drastically different morphologies for the two isomorphic orientations. Both surfaces immediately display a sharp LEED pattern. Together with the presence of oxygen in the AES spectra, this indicates the development of an ordered oxide. Both surfaces show an oxygen-free well-ordered surface after Si deposition and annealing.

Atomic Structure of Non-Basal-Plane SiC Surfaces: Hydrogen Etching and Surface Phase Transformations

AbstractA-plane (11-20) and diagonal cut (1-102) and (-110-2) surfaces of 4H-SiC have been investigated using atomic force microscopy (AFM), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). After hydrogen etching the surfaces show large, flat terraces. On SiC(11-20) steps down to single atomic heights are observed. On the diagonal cut surfaces steps run parallel and perpendicular to the [-1101] direction, yet drastically different morphologies for the two isomorphic orientations are found. All surfaces immediately display a sharp LEED pattern. For SiC(1-102) and SiC(-110-2) the additional significant presence of oxygen in the AES spectra indicates the development of an ordered oxide. All three surfaces show an oxygen free, well ordered surface after Si deposition and annealing. A transformation between different surface phases is observed upon annealing.

Many-electron effect in the angle resolved L 3-M 23M 23 Auger-photoelectron coincidence spectroscopy (APECS) spectrum of metallic Zn

The many-body effect in the L 3-M 23M 23 Auger-electron spectroscopy (AES) spectrum of metallic Zn is discussed. The lifetime width and residual relaxation energy shift of the two M 23-hole state are governed by the (super) Coster-Kronig (sCK) transitions of two M 23-hole state. The residual relaxation energy shift and decay width of the two M 23-hole state are calculated in an average configuration by an ab initio atomic many-body theory. The agreement with experiment is good. To elucidate the many-body effect in the two-hole states, it is necessary to be able to discriminate individual components of the multiplet-split AES spectrum. We discuss how to discriminate individual components of the multiplet-split L 3-M 23M 23 AES spectrum of metallic Zn by angle-resolved Auger-photoelectron coincidence spectroscopy (AR-APECS) in order to determine accurately their line shapes, multiplet splitting energies, and spin states (singlet etc.).