Auger Energy Research Articles

Auger and photoelectron relaxation energy in aluminum compounds: A cluster model

The energies of the Al Auger KL 2,3L 2,3 transitions and the Al 2p photoelectron peak have been determined experimentally by AES, XPS and XAES for several Al compounds. The experimental results are compared with ab initio calculations based on a cluster model in which a central aluminum atom is surrounded by its first neighbours in the crystal. This model includes chemical, structural and relaxation effects and it allows the direct ab initio determination of the intra- and extra-atomic relaxation energies. These values are compared with the Wagner equation that relates the extra-atomic relaxation energy and the Auger parameter. The three approximations that support this equation are examined on the basis of the cluster results.

Surface properties and activity of Fe–Ni–B ternary glasses

The surface structure, composition and corrosion behavior of metallic glass (MG) ribbons of the Fe–Ni–B system, with nominal composition Fe 40Ni 40B 20 are investigated by X-ray diffraction, Auger electron spectroscopy (AES) and energy dispersive X-ray spectroscopy (EDS). We found that the surface is Fe enriched at the expense of both Ni and B, while exposure to 200 eV N + and Ar + plasma modifies slightly the top surface layer further enriching the surface with Fe; in the case of N +, strong incorporation of N is detected indicating the formation of nitride phases. The corrosion behavior of the Fe–Ni–B surfaces was studied by electrochemical techniques in aquatic solutions of NaCl, NaOH, HNO 3 and HCl. Corrosion properties are very satisfactory compared to other MGs and engineering crystalline alloys with similar base compositions.

Investigation of W-Ge-N deposited on Ge as a diffusion barrier for Cu metallization

The properties of W-Ge-Nthin films were investigated as a diffusion barrier material for Cu metallization. The W-Ge-Nfilms were grown by reactive sputtering on a single crystal Ge substrate. This was followed by in-situ deposition of Cu. Diffusion barrier test was performed by annealing the film stack under Ar atmosphere. Phase identification and film crystallization were determined by X-ray diffraction. The deposited W-Ge-Nfilms remained amorphous even after high temperature annealing. The Cu diffusion profile in the film was assessed by Auger electron spectroscopy and energy dispersive spectroscopy. The results indicate that Cu diffusion was minimal in W-Ge-Nfilms even at high annealing temperatures. Interface reactions and properties were analyzed by cross-section transmission electron microscopy. The results suggest that W-Ge-Nmay be a superior diffusion barrier as compared to WNx for Cu metallization.

Investigation of electroless cobalt-phosphorous layer and its diffusion barrier properties of Pb-Sn solder

The capability of a cobalt-phosphorous [Co(P)] layer, which was grown via the electroless plating process, to serve as the diffusion barrier of lead-tin (PbSn) solder was investigated in this work. The Auger electron spectroscopy (AES) and energy dispersive spectrometry (EDX) indicated that the phosphorous contents in Co(P) films decrease with increasing film thickness and that the average contents are no less than 8.7 at.% for the specimens prepared in this work. X-ray diffraction in conjunction with composition analyses revealed that the electroless Co(P) layer was a mixture of amorphous and nanocrystalline structures; however, the AES depth profile and subsequent analyses indicated that the first-formed Co(P) layer should be amorphous because it contains as much as 18 at.% P. This implied a good barrier capability for electroless Co(P) because, as revealed by EDX line scan, the Sn and Cu atoms could not penetrate the Co(P) layer after the PbSn/Cu/Co(P)/Cu/Ti/Si sample was subjected to annealing at 250°C in a forming gas ambient for 24 h. The fact that Sn and Cu underlayers could not penetrate the Co layer after such a liquid-state annealing step was evidence that the Co(P) layer may simultaneously serve as a diffusion-barrier interlayer dielectric and as an under-bump metallization for flip-chip copper (Cu) ICs.

Theoretical modeling of thermally activated luminescence quenching processes in Si:Er

A theoretical description of processes responsible for thermally activated nonradiative relaxation of excited ${\mathrm{Er}}^{3+}$ ions in Si is developed. Microscopic models for the back transfer mechanism of excitation reversal and for Auger energy transfer to free and localized carriers are proposed. Simulations based on physical parameters are made and reasonable agreement with experiment is obtained. At the same time, the proposed theoretical treatment reveals aspects of the Auger deexcitation. In particular, important differences between interaction with free electrons and free holes are concluded. Experimental support for these findings is pointed out.

Failure Analysis of the Pressure Vessel by Stainless Steel: 1Cr18Ni9Ti

The corrosion failure of 1Cr18Ni9Ti stainless steel pressure vessel was studied with the aid of metallurgical microscopes, scanning electron microscopes, scanning Auger energy spectra and X-ray diffraction meters. The main causes of the failure included: inter-crystalline corrosion initiated at or near welding position between head and body of cylinder, electrochemical corrosion due to chloride ions in electrolyte and corrosive action formed by oxygen separator and hydrogen separator. Some measures of corrosion resistance and design improvement were proposed.

Auger energy shifts in fcc AgPd random alloys from complete screening picture and experiment.

We extend the complete screening picture to ab initio calculations of Auger kinetic energy and Auger parameter shifts in metallic alloys. Experimental measurements of the L(3)M(4,5)M(4,5) Auger transition in fcc AgPd random alloys are compared with first-principles calculations and the results are in excellent agreement for both the Ag and Pd Auger shifts over the whole concentration range. We discuss the Auger kinetic energy shifts in terms of single-hole states for the 2p(3/2) core level and double-hole states for the 3d(5/2) level.

Improving the corrosion resistance of NdFeB magnets: an electrochemical and surface analytical study

This study reports the results of work carried out to improve the corrosion resistance of NdFeB magnets by a direct phosphate treatment of the NdFeB magnet surface. The growth of a phosphate film on a NdFeB based magnet in a solution of 0.15M NaH 2PO 4 acidified to pH 3.8, was followed by electrochemical impedance spectroscopy (EIS) and open circuit potential variation as a function of time. After removal from the phosphating solution, the magnet surface was analysed by Auger electron spectroscopy (AES) and energy dispersive X-ray analysis (EDX). Phosphate formation on the surface was confirmed and a significant variation in the Fe/Nd ratio in the phosphate between the Fe and Nd rich phases of the magnet was found. The corrosion resistance of the phosphated magnets was evaluated in a normal enclosed atmospheric environment and in Na 2SO 4 solution and synthetic saliva by EIS measurements. The corrosion resistance was found to be substantially improved by the presence of a phosphate layer.

Synthesis of PtN x films by reactive laser ablation

Thin films of platinum containing up to ∼14 at.% nitrogen have been prepared by reactive laser ablation in molecular nitrogen ambient. The films are characterized in situ by Auger, X-ray photoelectron and electron energy loss spectroscopies (AES, XPS and EELS, respectively). The N 1s binding energy of 398.4 eV supports the existence of chemisorbed nitrogen. Moreover, a +0.2 eV shift of the Pt 4f peak position is a sign of charge transfer from Pt to N. In addition, alterations in the loss characteristics are indicating changes in the electronic configuration. It is concluded that platinum is forming an incipient nitride phase with composition near to Pt 6N.

The effect of heating on InGaAs/InP(1 0 0) and InPO 4/InP(1 0 0)

We have used Auger and electron energy loss spectroscopy to study the effect of temperature on InGaAs and InPO 4 grown on InP. The thickness of InPO 4 is of about 10 Å whereas that of InGaAs is of about 800 Å. InPO 4 is of great interest because it protects InP from loss of stoichiometry when heated to 450 °C. The InGaAs system heated at 450 °C seems to be unstable; metallic indium appears on the surface in conjunction with formation of GaAs.

Yttrium nitride thin films grown by reactive laser ablation

Yttrium nitride thin films were grown on silicon substrates by laser ablating an yttrium target in molecular nitrogen environments. The composition and chemical state were determined with Auger electron, X-Ray photoelectron, and energy loss spectroscopies. The reaction between yttrium and nitrogen is very effective using this method. Ellipsometry measurements indicate that the films are metallic. We attribute this behavior to a small oxygen contamination. Each oxygen atom introduces two additional electrons to the unit cell, resulting in a complex semiconductor–ionic–metallic system. These results are corroborated by first principles total energy calculations of clean and oxygen doped YN.

Auger deexcitation ofEr3+ions in crystalline Si optically induced by midinfrared illumination

We report on the de-excitation of ${\mathrm{Er}}^{3+}$ ions in crystalline silicon, induced by midinfrared radiation from a free electron laser. The effect is interpreted as an Auger energy transfer between excited erbium ions and free holes in the valence band. These are liberated from shallow traps by the powerful mid infrared laser beam. The traps are dynamically populated during the initial band-to-band excitation. The efficiency of the proposed de-excitation mechanism depends on the number of traps occupied at the moment when the free electron laser pulse is applied. Therefore the quenching effect is sensitive to the total number of acceptor traps present in the sample and the excitation density of the pump pulse. A competition between this de-excitation process and the previously reported mid infrared-induced Er photoluminescence enhancement is investigated. The optically induced Auger process, as revealed in this study, complements the description of energy transfer processes in the Si:Er system under optical pumping.

Electrical and Structural Properties of Refractory Metal Multilayer Au/Ti/W/Ti Ohmic Contacts to n-GaAs

The ohmic contact characteristics of Au/Ti/W/Ti on n-GaAs were evaluated. Structural and electrical properties were studied by means of X-ray diffraction (XRD), Auger energy spectrum (AES) and an HP4145B analyzer. AES results show that W is a good barrier for preventing Ga and As from out-diffusing. Electrical measurement showed a minimum ohmic contact resistance of 5.5×10-6 Ωcm2. Thermal annealing results revealed that Au/Ti/W/Ti contact to GaAs treated by a (NH4)2S solution can withstand a temperature of 400°C for 15 h. This indicates that Au/Ti/W/Ti contact to (NH4)2S-treated GaAs may be suitable for practical application.

Study of plasma etching of β-SiC thin films grown on Si-substrate

Abstract Plasma etching (PE) of β-SiC single crystal thin films produced via epitaxial growth on Si-substrate has been performed with different etching gases such as CF4, SF6, CF4 + O2, and SF6 + O2 mixtures. Experimental results using different etching gases are compared with respect to PE process condition, etching mechanism and products, surface states and Auger energy spectra analyses.

Copper nitride films produced by reactive pulsed laser deposition

Deposition of copper nitride films is of importance due to its technological applications. Copper nitride thin films are deposited by reactive pulsed laser deposition (nitrogen environments) on silicon substrates at room temperature. The resultant films are in situ characterized by Auger (AES), X-Ray Photoelectron (XPS) and Reflection Electron Energy Loss spectroscopies (REELS). The chemical bond is strongly linked to the stoichiometry, and both can be controlled by the deposition pressure. The mass density achieved for Cu 3N is 5.91 g cm −3, close to the theoretical value of 5.84 g cm −3 . We conclude that this deposition method offers a means for fine-tuning the properties of copper nitride.

Structural and electrical properties of Au/Pt/Ti ohmic contacts to degenerated doped n-GaAs

The ohmic contact characteristics of Au/Pt/Ti on degenerated doped n-GaAs were evaluated. Structural and electrical properties were studied by means of X-ray diffraction (XRD), Auger Energy Spectrum (AES) and a HP4145B parameter analyzer. The structural analysis revealed a TiAs phase in the interface between metal multilayer and GaAs at higher annealing temperatures. Electrical measurement showed a minimum ohmic contact resistance of 3×10-4 Ω cm2. The dominant current mechanism was found to be thermionic emission with a barrier height of Φb, of 0.09 V by comparing the experimental data with different theoretical models.

Suppression of Auger deexcitation and temperature quenching of the Er-related 1.54 μm emission with an ultrathin oxide interlayer in an Er/SiO2/Si structure

A strong enhancement of the Er3+-related 1.54 μm emission was obtained from Er-doped porous silicon (PSi), when host PSi was slightly oxidized before Er incorporation. Separate measurements of the energy transfer and the Auger deexcitation between carriers in Si crystallites of preoxidized PSi and Er3+ ions were measured as functions of the preoxidized time or the thickness of the SiO2 interlayer, and revealed that a 1 nm order thick SiO2 interlayer between Si crystallites and Er3+ ions suppressed the Auger energy backflow strongly with only a moderate decrease of the carrier mediated Er3+ excitation. A thin SiO2 interlayer was also effective at suppressing the phonon-assisted energy backtransfer at high temperatures, leading to a strong room temperature Er3+-related 1.54 μm emission.

Preferential suppression of Auger energy backflow by separation of Er ions from carriers with a thin oxide interlayer in Er-doped porous silicon

Strong enhancement of the Er-related 1.54μm emission was obtained at room temperature from Er-doped porous silicon (PSi), when host PSi was slightly preoxidized at 900°C before Er incorporation. It was speculated that the formation of the oxide interlayer played an important role. Separate measurements of the energy transfer and the Auger deexcitation between carriers in Si crystallites and Er ions were carried out using a two-beam (cw and pulse) excitation method for various preoxidation time which was supposed to change the oxide interlayer thicknesses from about 1 to 10nm. It was found that a very thin SiO2 interlayer between Si crystallites and Er ions suppressed preferentially the Auger deexcitation to the carrier-mediated Er excitation. A thin SiO2 interlayer was also effective to suppress the phonon-assisted energy backtransfer at high temperatures (so-called temperature quenching). This preferential suppression of the energy backflow (both Auger deexcitation and temperature quenching) by a thin oxide interlayer led to a strong room temperature Er-related emission at 1.54μm in Er-doped porous silicon. The Er/SiO2/Si structure was also formed on a flat Si surface and quite the same result was obtained. The oxide interlayer thickness of ∼2nm was found optimum to suppress the energy backflow sufficiently with only a slight decrease in the carrier-mediated excitation of Er ions.

Fabrication of two-dimensional assembly of L1 0 FePt particles

Synthesis of L1 0 phase FePt particles which are two-dimensionally distributed on a substrate surface is studied. In order to obtain a fine particle assembly of L1 0 phase the low temperature ordering process of FePt from Fe/Pt multilayers is extended to multilayers of Fe–(MgO,Ag)/Pt–(MgO,Ag). In the annealing process of these multilayer structures Fe tends to migrate in MgO or Ag toward Pt while Pt tends to remain in the original position. Double layers of Fe–Ag/Pt are chosen to synthesize a two-dimensional distribution of ordered FePt particles. According to the Auger and micro-beam energy dispersion X-ray spectroscopy (EDX) analysis a part of Ag in Fe–Ag layer tends to move to the surface by annealing to embed the ordered FePt particles. Measurements of δ M suggest that the particles are magnetically separated.

Excitation of triply excited Be+ (2lnl′n′l″) states in 300 and 500 keV-Be+ + CH4 collisions

We have studied high resolution beryllium Auger electron spectra in the 120–160 eV projectile electron energy range following intermediate energies (1.2 and 1.5 a.u. impact velocities) in Be++CH4 ion–molecule single collisions [Comments At. Mol. Phys. D 14 (1984) 117]. The major focus of this study is the double K-shell excitation of the Be+ projectile forming triply excited BeII*** states (hollow atoms) and BeIII** K shell ionization plus excitation of BeII doubly excited states with two inner shell vacancies. In such intermediate velocity ion-molecular collisions, the CH4 target plays an important role in the enhancement of the population of BeII*** triply excited states when compared to a more tightly bound He (1s2) 1S ground state target. Due to the pioneering theoretical work of Gou and Chung [Phys. Rev. A 29 (1996) 6103] most line structures can now be unambiguously identified. The main triply excited states are associated with the 2s22p, 2s2p2 and 2p3 and 2l2l′n′l″ (n=3 and 4) configurations decaying to different final BeIII (1snl) ionic states. The line identification method used here is based on Auger energy levels, decay channels and branching ratios.