Auger electron spectroscopy investigation of sputter induced altered layers in SiC by low energy sputter depth profiling and factor analysis

The thickness of the altered layer created by ion bombardment of the 6H–SiC single crystal was determined by means of Auger electron spectroscopy (AES) depth profiling in conjunction with factor analysis. After pre-bombardment of the surface by argon ions with energies 1, 2 and 4 keV until the steady state, the depth profiles of the induced altered layers were recorded by sputtering with low energy argon ions of 300 eV. Since the position and shape of the carbon Auger peak depend on the perfection of the crystalline structure, they were used for depth profile evaluation by factor analysis. In this way the depth profiles of the damaged surface region could be estimated in dependence on the ion energy. As a result, the thickness of the altered layer of SiC bombarded with 1, 2 and 4 keV Ar ions using an incident angle of 80° as well as the corresponding argon implantation profile could be measured.     

Electron production by metastable rare gas atom impact on a molybdenum (110) surface

Electron production by impact of thermal energy metastable helium, argon, and xenon atoms on a molybdenum (110) surface was studied. The electron yield was always highest for a clean surface and decreased considerably when the surface was exposed to either oxygen or carbon monoxide. The change in electronic yield with gas coverage of the surface was most drastic for xenon and smallest for helium metastables. The similarity of the present results to earlier measurements of electron production by low energy noble gas ion impact led us to believe that metastable deexcitation proceeded via resonance ionization followed by Auger neutralization in the present cases.     

Precise atomic scale studies of material sputtering by light-ion gases in the prethreshold energy region

The basis and prospects of a new original technique of determining the yields of the sputtering of conductive materials and subatomic films on their surface by light ion gases in the prethreshold energy region (from 10 to 500 eV) are discussed. This information is of great importance both for science and applications. The technique is based on special modes of field ion microscopy and includes the cleaning of specimens by field-induced desorption and evaporation, and subsequent operations with the atomically clean and atomically smooth surface in a wide temperature range from cryogenic temperatures. The technique enables one to identify single surface vacancies, that is, to directly count single sputtered atoms. The original results obtained with the developed technique are briefly reviewed. The energy thresholds of sputtering and the energy dependences of the sputtering yields in the prethreshold energy region are presented and analyzed for beryllium, tungsten, tungsten oxide, mixed tungsten-carbon layers, three carbon materials, and subatomic carbon films on the surface of certain metals bombarded by hydrogen, deuterium, and/or helium ions.     

Spectroscopic study of plasmons in ion-irradiated single-walled carbon nanotubes

The electronic structure of single-walled carbon nanotubes was experimentally investigated using x-ray photoelectron spectroscopy, reflection electron energy-loss spectroscopy, and Auger electron spectroscopy. A shake-up satellite structure observed near the C 1s core-level lines in the x-ray photoelectron spectra at high binding energies in the range 284–330 eV due to excitation of π and π + σ plasmons was studied. The effect of irradiation by 1-keV argon ions on the shape of the spectra was analyzed. The shape of the C 1s satellite spectra was found to be sensitive to Ar⁺ irradiation in the electron energy loss range 10–40 eV corresponding to excitation of π + σ plasmons. Auger spectroscopy revealed the presence of argon on the surface of ion-irradiated samples. The argon content increased to ～4 at. % with increasing irradiation dose. An analysis of the results obtained and their comparison with the data available in the literature led to a qualitative conclusion that the bond angles of the carbon atoms making up the walls of single-walled carbon nanotubes are distorted at sites exposed to Ar⁺ irradiation.     

Auger study of preferred sputtering on binary alloy surfaces

Auger Electron Spectroscopy has been used to investigate the preferred sputtering behavior on homogeneous Cu/Ni alloy surfaces. Measurements were made on a range of alloy compositions with Ar⁺ sputter ions of 0.5 to 2 keV energy. A kinetic model has been formulated to describe the time variation of the surface composition during sputtering. Based on this model, we were able to determine the individual sputter yields for Cu and Ni atoms in the alloy and the depth of the surface layer where the composition is altered by sputtering. The sputter yields were found to be relatively independent of the alloy composition but increased almost linearly with energy. The depth of the altered layer was comparable to the Auger sampling depth with its value increasing from 10 Å to more than 20 Å when ion energy increased from 0.5 to 2 keV.     

Formation of Ti and TiN ultra-thin films on Si by ion beam sputter deposition

Ultra-thin titanium and titanium nitride films on silicon substrate were obtained by ion beam sputtering of titanium target in vacuum and nitrogen atmosphere, using argon ions with energy of 5 keV and 15 μA target current. Elemental composition and chemical state of obtained films were investigated by X-ray photoelectron spectroscopy with using Mg-Kα X-ray radiation (photon energy 1253.6 eV). It was shown that it is possible to form both ultra-thin titanium films (sputtering in vacuum) and ultra-thin titanium nitride films (sputtering in nitrogen atmosphere) in the same temperature conditions. Photoelectron spectra of samples surface, obtained in different steps of films synthesis, detailed spectra of photoelectron emission from Si 2p, Ti 2p, N 1s core levels and also X-ray photoelectron spectra of Auger electrons emission are presented.     

碳在钼(100)和钼(111)表面上的超结构

用一定能量的氩离子束轰击含碳、氧的钼(100)和(111)表面,不能除去表面上的碳。而用能量为1千电子伏,束流为6微安的氮离子轰击10—15分钟,氮在表面的吸附达到饱和值。加热到400—600℃之间碳、氧从表面上基本消失,600—650℃之间吸附在表面上的氮大量脱附,即氮峰陡降到较低值,碳又偏析到表面上。加热到730℃和775℃氮从表面消失,分别得到碳在钼(100)表面上的p(2×2)和c(6×2)结构。而若将大量脱附氮的钼(111)表面,冷却到室温,氧又偏析到表面上。重新加热到650℃以上碳先从表面消失 关键词：     

Effect of ion sputtering on the surface composition of tin-lead alloys

The surface compositions of two SnPb alloys (Sn_0.998Pb_0.002 and Sn_0.03Pb_0.97) were monitored by Auger electron spectroscopy during the relaxation that occurs after the cessation of argon ion sputtering. The data show that sputtering enriches the near surface region in Sn. It is concluded that, for this system, chemical bonding, i.e., the heat of vaporization, determines which component is enriched in the near surface region during sputtering.     

Auger-spectrum simulation techniques for surface analysis of alloys with overlapping peaks: sputtered and annealed W—Mo alloys

The surface composition of a 50% W—Mo alloy has been investigated using Auger electron spectroscopy. Problems arising from carbon contamination and the strong overlap of the intense, surface-sensitive low-energy Auger peaks have been solved. Spectra for the alloy were collected digitally and could be simulated satisfactorily using pure-element spectra. The steady-state surface composition under 500 V Ar⁺ ion bombardment shows an enrichment of the surface in W, caused by preferential Mo sputtering. It is observed that the surface composition is uniform over the range of escape depths of the Auger electrons. This is consistent with enhanced diffusion and mixing over the penetration depth of the bombarding Ar⁺ ions. On annealing, the W-enriched sputtered surface becomes Mo-enriched, consistent with surface segregation of the more weakly bonded Mo atoms. However, in contrast with the sputtered surface, it is observed that a single simulation over the range of Auger-electron energies is not possible. The Mo enrichment indicated is largest for the 120 eV peak and decreases with increasing energy (escape depth), becoming a minimum at 220 eV. This is consistent with a monolayer segregation model, which is tested using published values for electron inelastic mean free paths. The calculated monolayer composition is x_Mo 0.94, in agreement with the predicted ideal-solution values of 0.98 ± 0.02 for different orientations.     

Distribution of Excited Atoms and Ions in a Plasma Generated at the Surface of Ferroelectric Ceramic

The distribution of excited atoms and ions in a plasma generated at the surface of ferroelectric ceramic has been studied. For all studied spectral lines of He I, Ar I, Ar II and hydrogen a decrease of the total line intensity with the increasing distance from the ceramic surface has been found. The shapes of these distributions are characteristic of the specific spectral lines. The distributions for He I lines depend strong on the concentration of argon in the helium — argon mixture. The effect of overpopulation of some excited Ar II ion levels in an argon discharge observed already in a previous work has been found also in the case of a helium — argon plasma.     

AES investigations of Ar+ ion retention in Si during Ar sputtering

Argon retention in silicon has been studied by AES in the energy range between 1 and 15 keV at bombardment fluences up to ∼10¹⁸ ions/cm². AES data of implanted argon in silicon near the surface region, as obtained during sputtering, can be interpreted qualitatively by a simple model of ion collection. Discrepancies between calculated and measured saturation values of collected argon ions indicate that during implantation at high fluences addition surface effects become important and that the simple model of ion collection has to account for this. Quantitative AES correlated with RBS indicates pronounced concentration gradients of argon in silicon near surface regions.     

AES investigations of Ar+ ion retention in Si during Ar sputtering

Argon retention in silicon has been studied by AES in the energy range between 1 and 15 keV at bombardment fluences up to ～10¹⁸ ions/cm². AES data of implanted argon in silicon near the surface region, as obtained during sputtering, can be interpreted qualitatively by a simple model of ion collection. Discrepancies between calculated and measured saturation values of collected argon ions indicate that during implantation at high fluences addition surface effects become important and that the simple model of ion collection has to account for this. Quantitative AES correlated with RBS indicates pronounced concentration gradients of argon in silicon near surface regions.     

An AES study of surface segregation of AgAu alloys with ion bombardment and annealing

Equilibrium segregation and selective sputtering in the surface of AgAu alloys have been investigated systematically with argon ion bombardment and with annealing by means of AES measurements. Slight enrichment of Ag was observed on the alloy surfaces after the annealing of the alloys at 550°C, while relatively large enrichment of Au was observed on the ion-bombarded surfaces with the use of Au (240 eV) and Ag (300 eV) Auger electrons. With the aid of other Auger electrons with different escape lengths, it was found that the concentration varies with distance from the surface within the sampling depth of the Auger electrons. On the basis of the above facts, the depth profiles were proposed for the annealed and the ion-bombarded surfaces. The uppermost surface layer is enriched more with Ag than the apparent AES observations on both the ion-bombarded and the annealed surfaces. The proposed depth profiles on both the surface layers were compared with previous results by different authors.     

Ultraviolet photoelectron spectroscopy of nano In clusters Schottky barriers on sputtered InP

Plasmon peaks along with Auger P_LVV peak have been observed in the ultraviolet photoelectron spectra (UPSs) of InP after 5 min of sputtering with 0.5 kV Ar⁺ ions. Plasmon and Auger peaks are not observed in UPS of un-sputtered InP surface with native oxides of In and P. Filled electron energy levels are not observed near the Fermi level from 5 min sputtered InP surface due to increase of ionization potential of nano In clusters.     

Deep radiation damage in copper after ion implantation

Copper single crystals were implanted off-axis at room temperature with carbon, neon, argon and xenon ions having energies ranging from 50 to 150 keV. Deep radiation damage was observed by α-particle channelling in a backscattering geometry. The total damage range was found to depend primarily on the ion energy, whereas the influence of the atomic number of the ion was significant only with xenon.     

Ion implantation induced by Cu ablation at high laser fluence

High energy laser plasma-produced Cu ions have been implanted in silicon substrates placed at different distances and angles with respect to the normal to the surface of the ablated target. The implanted samples have been produced using the iodine high power Prague Asterix Laser System (PALS) using 438 nm wavelength irradiating in vacuum a Cu target. The high laser pulse energy (up to 230 J) and the short pulse duration (400 ps) produced a non-equilibrium plasma expanding mainly along the normal to the Cu target surface. Time-of-flight (TOF) technique was employed, through an electrostatic ion energy analyzer (IEA) placed along the target normal, in order to measure the ion energy, the ion charge state, the energy distribution and the charge state distribution. Ions had a Boltzmann energy distributions with an energy increasing with the charge state. At a laser fluence of the order of 6 × 10⁶ J/cm², the maximum ion energy was about 600 keV and the maximum charge state was about 27+.In order to investigate the implantation processes, Cu depth profiles have been performed with Rutherford backscattering spectrometry (RBS) of 1.5 MeV helium ions, Auger electron spectroscopy (AES) with 3 keV electron beam and 1 keV Ar sputtering ions in combination with scanning electron microscopy (SEM). Surface analysis results indicate that Cu ions are implanted within the first surface layers and that the ion penetration ranges are in agreement with the ion energy measured with IEA analysis.     

Applying scattered-ion spectroscopy to the analyzing of plasma-surface interactions

A setup based on an ion mass monochromator and intended for investigating plasma interactions with surfaces of plasma facility materials is described. It analyzes the composition and thickness of surface films by means of ion scattering spectroscopy. An analysis of the composition of stainless steel and graphite is performed using helium and argon ions in the range of 2?C8 keV. The obtained results demonstrate the possibility of investigating the dynamics of carbon and oxygen behavior on the surface of materials using negatively charged recoil ions and scattered helium ions.     

Quantitative auger electron analysis of homogeneous binary alloys: Chromium in gold

Quantitative Auger electron analysis of Cr/Au alloys with up to 20% Cr has been accomplished. The surface composition of scribed areas were compared to bulk compositions and it was shown that corrections for variation of density, escape depth, and electron backscattering must be included; these corrections change the measured surface Cr concentrations by approximately 15%. Alloy sputter yield ratios have been calculated from surface concentrations after sputtering with Ar or Ne (0.5, 1.0, 1.5, and 2.0 keV). The sputter yield ratio of Cr to Au was 0.5 at 1% Cr (significant preferred sputtering) but was near unity at 20% Cr (no preferred sputtering). The sputter yield ratio was nearly independent of ion species and ion energy. The 2 keV argon ion sputter yields for pure Cr and Au were determined to be 2.0 and 7.9 atoms/ion, respectively. However, the 2 keV argon ion sputter yield for Au in the alloys drops rapidly from 7.9 atoms/ion for pure Au, to 5 atoms/ion at 10–20% Cr. The sputter yield for Cr in alloys (5 atoms/ion) is relatively independent of composition and is 2.5 times higher than the yield of pure Cr. No simple model is known by which pure elements sputter yields could be used to predict alloy sputtering behavior.     

Influence of ambient gas ionization on the deposition of clusters formed in an ablation plume

The effect of inert gas ionization on the dynamics of a laser ablation plume expanding through a background inert gas is studied. Charge transfer reactions between ablated ions and neutral background gas atoms yield to the formation of a charged layer on the plume expansion front. The energy lost by ablated ions when the plume is slowed down is calculated. The observed microstructure differences between carbon films prepared by pulsed laser deposition in helium, where the ionization mechanism is absent and respectively in argon, where it is present, are well correlated to model predictions.     

Possibilities of C 1s XPS and N(E) C KVV Auger spectroscopy for identification of inherent peculiarities of diamond growth

The interaction of C-atoms and CH_n-radicals with uncleaned and argon cleaned silicon substrate and with diamond surface after H-treatment have been studied in situ by XPS and Auger spectroscopy. It was found the formation of a new chemical surface state of carbon atoms in the case of carbon atoms and radicals interaction with cleaned silicon. The same chemical state was revealed on the H-treated diamond surface. Graphite-like structure of carbon atoms was observed on the surface of unlearned silicon and H-treated diamond after interaction with carbon atoms and radicals. N(E) C KVV Auger spectrum for the new chemical state of carbon atoms significantly differs from typical spectra for sp²- and sp³-bonded carbon materials. The high energy part of this spectrum was interpreted under the hypothesis of sp³-bonded carbon atoms but with shifted fermi level position.