Auger Emission Spectroscopy Research Articles

Hydrogen and deuterium permeation in Hastelloy N

Hastelloy N was chosen as the fluoride salt-contacting structural material for the Molten Salt Reactor Experiment due to its excellent compatibility with the fuel salt FLiBe. FLiBe is currently investigated for several advanced fusion and fission reactor concepts where tritium generation in the FLiBe is anticipated. Knowledge of hydrogen transport properties through Hastelloy N is important to understand how tritium would permeate through this material and result in an unintentional release. In this study, the hydrogen and deuterium permeability, diffusivity, and solubility were measured from 500 to 700 °C at a primary-side pressure of 10 kPa in a well-characterized sample of Hastelloy N. The prepared polycrystalline Hastelloy N had C and O impurities present on the surface. These impurities were investigated using Auger Emission Spectroscopy and Ar depth profiling. The adventitious C was removed upon the first Ar sputter cycle whereas O persisted deeper into the sample. For permeation experiments, applied deuterium pressures ranged from 13 Pa to 100 kPa and deuterium transport remained in the diffusion-limited regime (J ∝ P0.5) throughout the pressure range examined. Two methods are employed to measure the effective hydrogen and deuterium diffusivity: rise and decline. The decline method produced improved statistical model fits for calculating the effective diffusion coefficient compared to the rise method. The resultant transport properties compared well to published values for other nickel alloys.

(Invited) Electrical Atomic Force Microscopy for 2D Transition Metal Dichalcogenide Materials

As Si-based electronic devices are approaching their projected scaling limits, layered two-dimensional (2D) materials such as transition metal dichalcogenides (TMDs) are extensively studied as potential new channel materials and fundamental building blocks of emerging sensors and devices. In this context, MoS2 and WSe2 to name a few, are now available for deposition using different top down approaches. However, their outstanding properties are often degraded during the fabrication processes required for the device integration. For example, 2D TMDs selective growth, patterning and tuning of the electronics properties still remain elusive. Here, electrical atomic force microscopy (AFM) and beam analysis techniques are used to develop a framework of analysis for 2D materials. The latter is applied to understand the local properties of MoS2 comparing pristine material and structures which are selectively grown and patterned. Different growth techniques are investigated. After modelling the tip-sample contact system, we assess the impact of the plasma-induced damages combining the electrical AFMs and Auger emission spectroscopy. We study the local electrical properties of grain boundaries and their transport in patterned MoS2 structures for field-effect-transistor devices by conductive atomic force microscopy (C-AFM).

(Invited) Electrical Atomic Force Microscopy for 2D Transition Metal Dichalcogenide Materials

As Si-based electronic devices are approaching their projected scaling limits, layered two-dimensional (2D) materials such as transition metal dichalcogenides (TMDs) are extensively studied as potential new channel materials and fundamental building blocks of emerging sensors and devices.[1-2] In this context, MoS2, WS2 and WSe2 to name a few, are now available for deposition trough different top down approaches. However, their outstanding properties are often degraded during the fabrication processes required for the device integration. For example, the selective growth of 2D TMDs their patterning and the electronics properties fine tuning still remain elusive. Here we report on electrical atomic force microcopy (AFM) and beam analysis techniques which are used to develop a framework of analysis for 2D materials. The latter is applied to understand the local properties of MoS2 comparing pristine material and structures which are selectively grown and patterned.[3] Different growth techniques are investigated. After modelling the tip-sample contact system, we assess the impact of the plasma-induced damages combining the electrical AFMs and Auger emission spectroscopy. We study the local electrical properties of grain boundaries and their transport respectively in pristine and patterned structures for FET devices by conductive atomic force microscopy (C-AFM). [1] G. Fiori, F. Bonaccorso, G. Iannaccone, T. Palacios, D. Neumaier, A. Seabaugh, S. K. Banerjee, and L. Colombo, “Electronics based on two-dimensional materials,” Nat. Nanotechnol., vol. 9, no. 10, pp. 768–779, 2014.[2] Desai, S. B., Madhvapathy, S. R., Sachid, A. B., Llinas, J. P., Wang, Q., Ahn, G. H., Javey, A. (2016). MoS 2 transistors with 1-nanometer gate lengths, 354(6308), 2–6.[3] Chiappe, D., Asselberghs, I., Sutar, S., Iacovo, S., Afanas’Ev, V., Stesmans, A., … Thean, A. (2016). Controlled Sulfurization Process for the Synthesis of Large Area MoS2 Films and MoS2/WS2 Heterostructures. Advanced Materials Interfaces, 3(4), 1–10.

Beyond defect formation: Spectroscopic characterization of plasma-induced structural and electronic transformations in graphene

Recent research suggests plasma-induced hydrogenation is an efficient method for inducing a band-gap in graphene. To date, the characterization of plasma treatment-induced chemical changes is performed almost exclusively by Raman spectroscopy with the extent of hydrogenation presented as the evolution defect structures in the sp2 lattice of graphene. Alarmingly, almost no attention is given to the concurrent electronic modification. Here, x-ray induced Auger emission spectroscopy is utilized to better understand the effect of plasma treatment on the electronic properties of graphene beyond the formation of defects as determined by Raman spectroscopy. The results indicate the fine structure of the CKLL emission offers a suitable complement to Raman spectroscopy in assessing the extent of chemical and electronic changes induced by H2 plasma treatments. Significant changes to the D-value, defined as the distance between local maxima and minima in the CKLL Auger emission, are observed after only 30 s of treatment (p < 0.001), while the ID/IG ratio remains statistically equivalent (p = 0.441). The results indicate significant differences in the electronic properties of plasma-treated graphene are observed concomitant to sp2 defect structures normally attributed to hydrogenation.

Study of compositional change in the interfacial regions between lead strontium titanate/SiO 2 and lead zirconate titanate/SiO 2 by Auger emission spectroscopy

Auger spectroscopy was used to study the compositional change in the interfacial region between ferroelectric thin films, namely lead strontium titanate (PST) and lead zirconate titanate (PZT), and commercially available Si substrates with a 200 nm thick thermal oxide layer. Both PST and PZT thin films were prepared via a sol–gel spin coating method. The thin films from both materials were annealed under the same conditions (temperature and time). It was found that strontium stops the lead diffusion into SiO 2 by forming SrSiO 3/Sr 2SiO 4 and SrO, maintaining a well defined SiO 2 region, while PbSiO 3 is formed in the PZT/SiO 2 system. These results are important for a general understanding of interdiffusions in material interfaces in particular for the realization of future high-dielectric-constant (high-k) oxide layers and for the next generation of advanced electronic devices.

Improving high‐temperature oxidation behaviour of Sn‐Zn‐Ag‐Al‐Ga solders

PurposeThe purpose of this paper is to study the influence of silver on the high‐temperature oxidation behaviour of the Sn‐8.5Zn‐xAg‐0.01Al‐0.1Ga (x=0, 0.1, 0.3 and 0.5) solder alloys.Design/methodology/approachThe weight gains of the studied solders are measured using thermal gravimetric analyzers (TGA) at temperatures of 250, 300, 350 and 400°C. The weight gains measured are used to compare the oxidation behaviour of the studied solders. The surfaces of the solders are also analyzed with Auger emission spectroscopy (AES) depth profiling and thin‐film X‐ray diffractometry (thin‐film XRD) to identify the elements present on the surface of the studied solders.FindingsThe TGA results show that the weight gains decrease with increasing silver content in the studied solders. It meant that increasing silver content could help improve the high‐temperature oxidation behaviour of the studied solder. AES and thin‐film XRD confirm that the formed oxide layers on the surface of the studied solder are Zn‐based oxide layers.Originality/valueThe findings of this paper will help provide an understanding of the effects of silver on Sn‐8.5Zn‐xAg‐0.01Al‐0.1Ga solder.

Structure and properties of TiB2 thin films deposited at low temperatures using RF magnetron sputtering

The TiB2 thin films were deposited on steel substrates using RF magnetron sputtering technique with the low normalized substrate temperature (0.1<Ts/Tm<0.2). Microstructure of these films was obtained by field emission scanning electron microscope (FESEM) and the grazing incidence X-ray diffraction (GIXRD) characterization, while the composition of films was obtained using Auger emission spectroscopy (AES) analysis. It was found that the TiB2 thin films were overstoichiometric with the B/Ti ratio at 2.33 and the diffusion of Ti and B atoms on the substrate surface was greatly improved at 350 °C. Moreover, a new dense structure, named “equiaxed” grain structure was observed by FESEM at this substrate temperature. Combined with FESEM and AES analysis, it was suggested that the “equiaxed” grain structure was located in Zone 2 at the normalized substrate temperature as low as 0.18.

Photoluminescence of strained Si 1 − x − yGe xC y epilayers on Si(100)

Photoluminescence (PL) spectroscopy has been used to study the incorporation of C in several samples consisting of strained Si 1 − x − y Ge x C y epilayers lattice matched to Si (001). To obtain the total C concentration, these samples were characterized by both SIMS and Auger emission spectroscopy, and X-ray diffraction data was analyzed to obtain the substitutional C concentration. The difference of the total and substitutional C concentrations, i.e., the non-substitutional carbon fraction, was found to be directly correlated with specific spectral lines in both the room-temperature Raman and low-temperature PL spectra.

Photoluminescence and Raman spectral study of C incorporation in strained Si1−x−yGexCy epilayers on Si(100)

Photoluminescence (PL) and Raman spectroscopy have been used to study the incorporation of C in strained Si1−x−yGexCy epilayers lattice matched to Si(001). The samples were characterized by both secondary ion mass spectrometry and Auger emission spectroscopy to obtain the total C concentration and x-ray diffraction data were used to obtain the substitutional C concentration. The difference between the total and substitutional C concentrations, i.e., the nonsubstitutional carbon fraction, was found to be directly correlated with specific spectral lines in both the room temperature Raman and low temperature PL spectra. These variations are discussed and related to C related defects in the epilayers.

Surface modification of austenitic stainless steel on the surface of electric contact during low frequency current circulation

During process of surface treatment of steels using plasmas (ion nitriding, physical vapor deposition and chemical vapor deposition, plasma immersion ion implantation, etc.), normally, one of the surfaces of the pieces has to be in electrical contact with one of the electrodes. In this work, we investigate the surface modification of the SAE EV12 stainless steel after being in electrical contact with the cathode during a normal process of ion nitriding. The physical conditions used were of a square wave electrical current of 10, 100 and 1000 Hz with an amplitude between 40 A m −2 and 80 A m −2 passing during 40 min. The treated surface was studied under Auger emission spectroscopy and grazing angle X-ray diffraction. The results have shown that a surface layer of 60 nm is strongly altered, and that the results depend on the frequency of the applied voltage and the pressure of contact between the surface and the cathode. In this surface layer, we could see the Fe–Cr, MnO and a carbide of the type (Fe,Ni) 23C 6 called haxonite, only reported in meteorites.

The electronic structure of carbon films deposited in rf argon–hydrogen plasma

The electronic structure of C films deposited by sputtering a graphite target in rf. Ar–H 2 plasma is investigated by photoemission, Auger emission and electron energy loss spectroscopy (EELS) as a function of the H 2 concentration in the feed gas, referred to as [H 2]. Adding hydrogen to the plasma causes the films to change from a graphite-like unhydrogenated structure to a non-graphitic hydrogenated structure. The film mass density, as derived from the π + σ plasmon energy, decreases upon H 2 addition to the gas mixture, goes through a minimum at low [H 2] and increases with increasing [H 2]. It reveals a non-monotonous behavior of the film H content as a function of [H 2], the maximum H incorporation occurring at low [H 2]. This appears to be a characteristic of C deposition via graphite sputtering in Ar–H 2 plasma and it is discussed in connection with previous results on the subject.

Nanocrystalline haematite thin films by chemical solution spray

Haematite thin films were prepared by spraying ethanolic solution of iron tri-chloride onto tin-doped indium oxide (ITO) coated glass substrates. The spray time, spray rate, pressure of carrier gas, etc were optimized to obtain nanocrystalline thin films. The films were adherent, smooth, compact and pinhole free. The films were characterized for their structural, morphological, optical and compositional properties. X-ray diffraction studies show that films are nanocrystalline α-Fe2O3 having haematite phase. SEM shows that the film consists of elliptical grains randomly distributed with average grain size of about 40–45 nm. The optical band gap was found to be 2.0 eV. Compositional uniformity was confirmed by Auger emission spectroscopy. Annealing the films at 380 °C for half an hour increases the particle size.

Nuclear motion in the O 1s −12π u core-excited states of CO 2 probed by sub-natural-width resonant Auger emission spectroscopy

A promotion of the O 1s electron in the CO 2 molecule to the lowest unoccupied molecular orbital 2π u brings about the stretching and bending motions in the core-excited states. These nuclear motions are investigated by use of the sub-natural-width resonant Auger emission spectroscopy.

Ti/TiN/Ti(N) PVD liners for W-plug applications

A novel scheme for implementing a same chamber Ti/TiN/Ti(N) W-plug liner is introduced. The Ti(N) cap is the result of a TiN-coated target clean in an argon only plasma. It is found that a process window exists within which a thin flash layer renders the contribution of TiF 3 formation during the CVD W deposition process to via resistance insignificant. At the same time the flash process time is long enough to sufficiently de-nitride the target. The subsequent Ti deposition is pure enough to getter any surface contamination at the bottom of the vias. The W-liner interfaces for flash layers of varying thicknesses are investigated using Auger emission spectroscopy. The electrical results presented demonstrate that the Ti/TiN/Ti(N) liner is comparable to standard liner processes.

A study of the NiSi to NiSi 2 transition in the Ni–Si binary system

The growth mechanisms of the transition from polycrystalline NiSi to single-crystal NiSi 2 have been investigated. Samples were prepared by depositing Ni on 〈100〉 Si substrates by ultra high vacuum electron-beam deposition followed by vacuum annealing to form a silicide. Experiments were carried out at the transition temperature of 750°C for different annealing times. Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM), scanning electron microscopy (SEM), Auger emission spectroscopy (AES) and X-ray diffraction (XRD) were employed with special emphasis placed on scanning and transmission electron microscopy. Cross-sectional examination in the transmission electron microscope reflects the coexistence of nickel monosilicide and nickel disilicide for samples annealed at 750°C. Scanning electron microscopy shows interesting surface morphology of samples in which island-like NiSi 2 growth takes place in an NiSi thin film. Grain boundaries in the initial and final stages of NiSi 2 formation are characterized by holes which extend from the surface to the silicon substrate. A mechanism is proposed to account for these observations by involving the following: lattice diffusion of Ni into the Si substrate, the conversion of NiSi grains to NiSi 2 via nucleation and diffusion processes and lateral grain growth resulting in accumulation of vacancies on grain boundaries resulting in holes.

Spin-resolved electron spectroscopies of epitaxial magnetite (001) (abstract)

We will present the first spin-resolving electron spectroscopic studies of a magnetite (Fe3O4)(001) surface. Magnetite is a semimetal with a high density of states in the minority band, but a large band gap in the majority states at the Fermi energy. The polarization of the secondary emission cascade is measured using spin-resolved secondary electron emission spectroscopy (SRSEES), and reflects the semimetallic spin structure of Fe3O4. The polarization plateau of spin-resolved secondary emission (29.8%) matches the average 3D band polarization of stoichiometric Fe3O4 as determined from spin-resolved band structure calculations (34.2%). An enhancement of the polarization of the secondary electrons at lowest energies will also be discussed. Spin-resolved Auger emission spectroscopy (SRAES) of the Fe3O4 films have been measured and show correlation effects in the valence-valence Auger transitions. Suppressed intensity and polarization of M23M45M45 Auger emission relative to M1M45M45 Auger emission is observed, as well as strong resonant emission with shake-up. Conversely, no spin polarization is detected in the spin-resolved oxygen LMM Auger features, although oxygen Auger emission (in which we can distinguish between adsorbed and bonded oxygen) is used to verify surface cleanliness of the samples. The synthesis of Fe3O4 films grown on magnesium oxide (001) substrates using oxygen plasma-assisted molecular beam epitaxy will be discussed, as will thin-film characterization using SQUID magnetometry and x-ray and electron diffraction. A unique angle-, energy-, and spin-resolved electron spectrometer has been designed and built for the study of magnetic surfaces, and these studies represent its’ first use. That spectrometer is based on a tandem configuration of an energy-dispersive energy analyzer and Mott spin polarimeter.

On The Origin of Laser-Induced Surface Activation of Ceramics

ABSTRACTThe surfaces of Al2O3and AlN are modified by pulsed-laser irradiation This modification promotes the deposition of copper when the irradiated substrates are immersed in an electroless bath. In this paper the nature of the surface modification is analyzed using results from Auger Emission Spectroscopy (AES) and Cross Sectional Transmission Electron Microscopy (XTEM). During irradiation AlN thermally decomposes leaving a discontinuous metallic film on the surface. A film of Al2O3is detected at the surface of the irradiated AlN substrate, much thicker when the irradiation is performed in an oxidizing atmosphere than when done in a reducing one. Nanoparticles of metallic aluminum are generated during laser irradiation of Al2O3in a reducing atmosphere. When the irradiation of Al2O3is performed in an oxidizing atmosphere, regions containing aluminum or substoichiometric alumina are detected by AES. It is concluded that the presence of metallic aluminum is the main reason why electroless deposition can occur in both AlN and Al2O3. Deposition kinetics are completely consistent with this conclusion. It is very likely that also substoichiometric alumina helps to catalyze the electroless deposition.

Pyrolysis Studies of Single-Source Precursors to Gallium Phosphide

ABSTRACTNew dialkylgallium dialkylphosphide compounds having the formula [(t- Bu)(R)GaPR'2]n (R = t-Bu, Me3SiC=C; R' = t-Bu, i-Pr, Et; n = 1, 2) were recently prepared and characterized. When R = R' = t-Bu, the compound is a low melting, monomeric solid. The other compounds are dimeric solids with the unsym-metrical acetylides occurring as cis and trans isomers. Polycrystalline gallium phosphide was deposited from these sources on silicon atlow pressure (0.05–0.1 Torr) and low temperature (350–600 °C) in a horizontal OMVPE reactor. The film growth was monitored by a residual gas analyzer and the by-products were trapped (N2(1)) to be later analyzed by 1H and 13C NMR. The deposited films were characterized by Raman spectroscopy, X-ray powder diffraction, and Auger emission spectroscopy.

Uses of the plasma arc in microelectronics

Abstract The crystallization of amorphous silicon (a:Si) thin films and metal-silicide compound formation using the plasma arc discharge has been studied using Raman spectroscopy, Auger emission spectroscopy, Rutherford backscattering, photoconductivity measurements and surface morphology examination. Crystal sizes of the order of hundreds of microns were produced from 05 μm thick a:Si film by using a single light pulse having 3–5 Jcm−2 incident energy density. In the nickel-silicide formation study, a high degree of mixing of Ni and Si was found after exposure to an arc light pulse having 45 J cm−2 incident energy density, A 1000 A thick film of Ni was deposited onto a 〈100〉 silicon wafer and covered with a 300A-thick anti-reflection a:Si coating.

A quartz crystal-controlled evaporator for the study of metal film alloy hydrides

The authors describe an automated evaporation system for the production of metal alloy thin films that can be used for the study of metal alloy hydrides. This apparatus has been used to reproducibly fabricate alloy thin film structures (30-150 nm) with control of alloy composition, rate of mass deposition and thickness. Composition homogeneity is evaluated using Auger emission spectroscopy (AES). The system is also designed to perform automated hydrogenation in order to obtain reproducible pressure-solubility phase diagrams of the metal alloy hydrogen systems over a wide range of alloy compositions and temperatures. Although designed to produce binary alloy structures, the system can be adapted for deposition of more complex alloy systems including artificially structured materials.