Auger Electron Spectroscopy Depth Profiling Research Articles

Work Function Tailoring of Carbon-Added Tungsten Gate Electrodes

In this work, carbon-added tungsten (, ) and thin carbon layer-inserted tungsten (, the thickness of is set to be and ) gate stacks are deposited on to fabricate metal-oxide-semiconductor capacitors. Grazing incident angle X-ray diffraction reveals that the films become amorphous when the concentration of added C is lower than 16 atom %. However, when the C concentration is as high as 19 atom %, a trace of γ phase of tungsten carbide phase appears in the film. No interdiffusion between C-added W and is observed by Auger electron spectroscopy depth profiling. The resistivity of W, , , and are 132, 151, 163, and , respectively. The work function of , , , W, , and on are 4.82, 4.75, 4.73, 4.66, 4.52, and , respectively. The C-related dipole shows apparent influence on the work function. The leakage current densities of C-added W films are smaller than in the range from . No significant influence of these gate electrodes on the fixed oxide charge and the leakage behavior of are observed.

Synthesis of gadolinium aluminate thin film by ion beam sputtering sequential deposition

Sequentially deposited by thin film synthesis consisted of multilayer precursor film deposition and thermal treatment. It is especially useful in complex-ingredient or precise stoichoimetric controlling thin film synthesis. Gadolinium aluminate, a new good candidate system for many luminescence usages other than laser crystals, scintillation crystals, phosphors, contains many phases, such as Gd 4Al 2O 9(GAM), GdAlO 3(GAP), Gd 3Al 5O 12(GAG), so precise stoichoimetry of the amorphous ingredient layers is very important to the final single phase film synthesis. In our work, Gd 2O 3 and Al amorphous layers (ingredients for gadolinium aluminate film) were deposited in a certain sequence on MgO (100) and Si (100) substrate by IM100 (an ion beam sputtering instrument). The multi-amorphous-layered precursor was annealed with two-step thermal treatment (diffusion at a low temperature and then crystallization at a high temperature). The XRD (X-ray diffraction pattern), SEM (scanning electron microscope second electron image) and AES (Auger electron spectroscopy depth profiles) analyses were used to detect the film microstructures and properties. The analyses results showed that ion beam sputtering deposition could control ingredient stoichoimetric ratio by an in site depositing thickness measurement. During the two-step thermal treatment, diffusion at a low temperature would cost a rather long time to make the amorphous precursor film uniform (more than 120 h), and the suitable diffusion temperature should be around 400 °C. The crystallization temperature should be decided by the gadolinium aluminate phase types and cost rather less time (about 4 h). The stable phases GAP and GAM should be annealed at 1300 °C or higher temperatures, but the metastable phase GAG should just be annealed at around 1100 °C.

Characteristics of La 2O 3–Y 2O 3–Mo cermet cathode with RE 2O 3 nano particles

The secondary electron emission property and microstructure of La 2O 3–Y 2O 3–Mo cermet cathode have been studied. It shows that the cathode prepared by Sol–Gel doping method has fine microstructure containing rare earth oxide (RE 2O 3) nanoparticles and uniform distribution of different substances. Auger Electron Spectroscopy (AES) depth profile result shows that an RE 2O 3 layer about 28 nm in thickness could be formed on the cathode surface, which plays an important role in the emission. Pre-activation of the cathode is favorable for the improvement of emission property. La 2O 3–Y 2O 3–Mo cathode pre-activated exhibits good secondary emission property. The secondary emission yield could reach 5.24, about 1.8 times higher than that of original cathode. The enhancement on the conductivity of materials resulting from the pre-activation is favorable for the replenishment and transport of electrons, thus the secondary emission property of the cathode could be improved.

Effect of alkaline cleaning and activation on aluminum alloy 7075-T6

The effect of alkaline cleaning and activation on the composition and thickness of the oxide layer on aluminum alloy 7075-T6 was studied. E–pH diagrams were developed to predict the effect of alkaline cleaning and activation solutions on the stability of the oxide surface layers. The thickness of the native oxide layer was determined to be ∼30 nm by Auger electron spectroscopy depth profiling analysis. The outer ∼20 nm was rich in magnesium while the remaining ∼10 nm was rich in aluminum. Cleaning in a 9.1 pH alkaline solution was found to remove the magnesium-rich layer and leave behind an aluminum-rich oxide layer ∼10 nm thick. Activation in alkaline solutions of NaOH (pH > 12.9) or Na 2CO 3 (pH > 11.5) produced an oxide that was ∼20 to 60 nm thick and rich in magnesium. Alkaline cleaning and activation altered the oxide composition and thickness making it possible for deposition of thicker cerium-based conversion coatings (∼100 to 250 nm) compared to only alkaline cleaning (∼30 nm), with application of one spray cycle of deposition solution.

Effect of Substrate Temperature on the <I>In-Situ</I> Formation of Crystalline SiC Nanostructured Film Using Ultra-High-Vacuum Ion Beam Sputtering

In this paper, we have investigated the effect of substrate temperature on the in-situ formation of crystalline SiC (c-SiC) nanostructured film using ultra-high-vacuum ion beam sputtering (UHV IBS). The phase transformation, bonding behavior, morphology, composition and interdiffusion of the SiC nanostructured film were examined by X-ray diffraction, Raman spectra, high resolution scanning electron microscopy (SEM) with the attached energy dispersive X-ray detector and Auger electron spectroscopy (AES) depth profile, respectively. The in-situ formation of c-SiC was through interdiffusion and reaction between the sputtered carbon (C) and the crystalline Si (c-Si) substrate at high temperature. The amorphous-like C microstructure is stable up to 500 degrees C and transformed into a new phase of c-SiC together with the remained C at 600 degrees C. Complete C and Si reaction was found at 700 degrees C from Raman spectra without any C peaks. The main diving force for the c-SiC formation is the thermal energy to activate the large interdiffusion between C and c-Si which was detected from AES depth profile. Also, a nanoweb-like morphology of the c-SiC was observed on the surface of film from the SEM image. Therefore, the c-SiC nanostructured film can be obtained at 700 degrees C using in-situ UHV IBS process, which is much lower than conventional CVD c-SiC.

Thermal stability of thin ZrO2 films prepared by a sol-gel process on Si(001) substrates

ZrO2 films with a thickness as low as 4 nm and a roughness of about 0.2 nm have been deposited on Si(001) by a sol-gel process. After pyrolysis in air clean and dense ZrO2 films were obtained. To simulate the influence of thermal processes in complementary metal-oxide-semiconductor fabrication on high-k gate oxides, our samples have been subjected to heat treatments up to 1000 °C. The chemical composition of the ZrO2 films and of the interface region has been monitored by Auger electron spectroscopy (AES) and AES depth profiles. No notable chemical changes in the interface region have been detected after heating at 700 °C in 2×10−5 mbar oxygen partial pressure and rapid annealing to 1000 °C. At 700 °C and 10−4 mbar oxygen partial pressure an intermediate interface layer starts to grow by oxidation of the Si substrate. Annealing above 700 °C in UHV leads to the destruction of the sample. Loss of oxygen is accompanied with the formation of islands containing Zr and Si and of holes extending up to 200 nm deep into the Si substrate.

Effect of lubricant additives in rolling contact fatigue

Lubricant formulations for manual gear box applications are optimized for gear contacts although rolling element bearings are lubricated with the same fully formulated oil. This may cause fatigue-related damage to these bearings. Several explanations can be considered, but this work focuses on the effect of additives contained in the lubricant. Rolling contact fatigue tests were performed on a twin-disc machine. Artificial dents generated by a Rockwell penetrator were made on the faster surface in order to accelerate the fatigue phenomena. Then, pure rolling and 6.7 per cent slip (slide-to-roll ratio (SRR)) tests were performed with different lubricants (pure base oil, fully formulated oil, and base oil with detergent and anti-foam). Fatigue life results and spalling morphologies are compared. For the sample obtained with the fully formulated oil and 6.7 per cent of SRR, crack analysis was performed. Using focus-ion-beam technique, a spalled sample was milled to reveal a cross-section of a crack. Secondary electron microscopy (SEM) images were taken and energy-dispersive X-ray spectrometry (EDX) analyses along the crack were performed. Additive elements are detected up to the crack tip. Auger electron spectroscopy depth profiling was also performed in the tribofilm generated on the disc surface. The role of additives in rolling contact fatigue is discussed in the light of these results.

Formation of high reflective Ni/Ag/Ti/Au contact on p-GaN

A metallization scheme of Ni/Ag/Ti/Au has been developed for obtaining high reflective contacts on p-type GaN. In order to find optimal conditions to get a high reflectivity, we studied samples with various Ni thicknesses, annealing temperatures and annealing times. By annealing at 500 °C for 5 min in an O 2 ambient, a reflectivity as high as 94% was obtained from Ni/Ag/Ti/Au (1/120/120/50 nm). The effects of Ti layers on the suppression of Ag agglomeration were investigated by using Auger electron spectroscopy (AES). From AES depth profiles, it is clear that Ti acts as a diffusion barrier to prevent Au atoms from diffusing into the Ag layer, which is important in the formation of high reflectivity.

Diffusion of implanted nitrogen in the Cu(0 0 1) surface

Auger electron spectroscopy (AES) was used to study the thermally activated diffusion process of low energy N+ implanted on the Cu(0 0 1) surface, a proposed model system for self-assembled nanostructures. The nitrogen diffusion was characterized as a function of the substrate temperature and the N+ implantation energy. An experiment that combines a temperature evolution followed by an AES depth profiling was done to clarify the type of diffusion. A comparison of the experimental results with kinetic Monte Carlo simulations suggests a preferential diffusion of the nitrogen to the surface followed by nitride decomposition.

Surface characterization of Pd/Ag23 wt% membranes after different thermal treatments

Hydrogen permeation measurements of 1.5–10 μm thick Pd/Ag23 wt% membranes before and after thermal treatments at 300 °C in air (both sides) or in the temperature range 300–450 °C in N 2 (feed side) and Ar (permeate side) were performed. Accompanying changes in surface topography and chemical composition were subsequently investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) depth profiling. For a 2 μm thick membrane, the surface roughness increased for all annealing temperatures applied, while a temperature of 450 °C was required for an increase in roughness of both membrane surfaces to occur for the 5 μm membrane. The thickest membrane, of 10 μm, showed changed surface roughness on one side of the membrane only and a slight decrease in hydrogen permeance after all heat treatments in N 2/Ar. X-ray photoelectron spectroscopy investigations performed after treatment and subsequent permeation measurements revealed segregation of silver to the membrane surfaces for all annealing temperatures applied. In comparison, heat treatment at 300 °C in air resulted in significantly increased hydrogen permeance accompanied by increasing surface roughness. Upon exposure to oxygen, Pd segregates to the surface to form a 2–3 nm thick oxide layer (PdO), with more complex segregation behavior after subsequent reduction and permeance measurements in pure hydrogen. The available permeance data for the Pd/Ag23 wt% membranes after heat treatment in air at 300 °C is found to depend linearly on the inverse membrane thickness, implying bulk limited hydrogen permeation for thicknesses down to 1.5–2.0 μm.

Plasma nitridation of silicon by N2 and NH3 in PECVD reactor

The effect was investigated of nitrogen and ammonia plasma treatment of monocrystalline Si wafers. The experiments were carried out in a plasma-enhanced chemical vapor deposition reactor. The wafers were subjected to N2 and NH3 plasma treatment for varying times at temperature of 380 °C. The plasma treated surfaces were studied by transmission electron microscopy with C-Pt replicas, reflection high-energy electron diffraction and Auger electron spectroscopy. The results point to the growth of an amorphous layer on the surface. The Auger electron spectroscopy depth profiles obtained by sputtering show the presence of an oxynitride layer with varying composition depending on the time of plasma treatment. The Auger electron spectroscopy analysis shows that after 60 s of treatment in N2 plasma, the nitrogen content is 8 at.%, while after 300 s it is 22 at.%, the thickness of the oxynitride nanolayer being 2.5-7.2 nm. In the case of NH3 plasma the thickness calculated from the sputtering time (from 50 s to 15 min) varies between 2 and 12 nm, and the nitrogen content, between 5 and 35 at.%.

Anomalous atomic transport in driven systems: Ion-sputtering induced enhanced intermixing and cratering in Pt/Ti

Probing the anomalous nanoscale intermixing using molecular dynamics (MD) simulations in the Pt/Ti bilayer we reveal the enhancement of the interfacial atomic transport. It is shown that the Pt atoms undergo anomalous atomic transport across the interface of Pt/Ti with surprisingly high rates. In particular, the low-energy (0.5 keV) ion-sputtering induced transient enhanced intermixing has been studied by MD simulations. Ab initio density functional calculations have been used to check and reparametrize the employed heteronuclear interatomic potential. The transient enhanced intermixing behavior explains the long diffusity tail in the concentration profile obtained by Auger electron spectroscopy depth profiling analysis in Pt/Ti bilayer (reported in Ref. P. Sule, M. Menyhard, L. Kotis, J. Labar, J.F. Egelhoff Jr., J. Appl. Phys. 101 (2007) 043502). Moreover, we point out that atomic mass-anisotropy has no effect on interdiffusion in the nanoscale hence other (unknown) factors are responsible for the anomalous interface broadening. The mean-square of atomic displacements scales superlinearly in Pt/Ti, while show sublinear scaling behavior in Ti/Pt. The exponent of a fitted power-law expression is 1.65 in Pt/Ti which suggests the anomalous character of intermixing. Anomalously long (ballistic) atomic jumps of Pt atoms across the interface are seen also only in Pt/Ti. Moreover, the robust Pt atomic injection into the Ti bulk takes place together with an enhanced surface cratering in Pt/Ti. No such behavior is seen for Ti/Pt. These surprising atomistic features could be the signature of an anomalous driven process not reported yet for bulk systems.

Switching mechanism transition induced by annealing treatment in nonvolatile Cu/ZnO/Cu/ZnO/Pt resistive memory: From carrier trapping/detrapping to electrochemical metallization

ZnO/Cu/ZnO trilayer films sandwiched between Cu and Pt electrodes were prepared for nonvolatile resistive memory applications. These structures show resistance switching under electrical bias both before and after a rapid thermal annealing (RTA) treatment, while it is found that the resistive switching effects in the two cases exhibit distinct characteristics. Compared with the as-fabricated device, the memory cell after RTA demonstrates remarkable device parameter improvements including lower threshold voltages, lower write current, and higher Roff/Ron ratio. A high-voltage forming process is avoided in the annealed device as well. Furthermore, the RTA treatment has triggered a switching mechanism transition from a carrier trapping/detrapping type to an electrochemical-redox-reaction-controlled conductive filament formation/rupture process, as indicated by different features in current-voltage characteristics. Both scanning electron microscopy observations and Auger electron spectroscopy depth profiles reveal that the Cu charge trapping layer in ZnO/Cu/ZnO disperses uniformly into the storage medium after RTA, while x-ray diffraction and x-ray photoelectron spectroscopy analyses demonstrate that the Cu atoms have lost electrons to become Cu2+ ions after dispersion. The above experimental facts indicate that the altered status of Cu in the ZnO/Cu/ZnO trilayer films during RTA treatment should be responsible for the switching mechanism transition. This study is envisioned to open the door for understanding the interrelation between different mechanisms that currently exist in the field of resistive memories.

Oxidation behavior of a Mo (Si, Al) 2-based composite at 300–1000 °C

The oxidation behavior of a Mo (Si,Al) 2-based composite of Mo(Si,Al) 2, Al 2O 3 and Mo 5(Si,Al) 3 (Kanthal Super ER) in synthetic air was investigated. The samples were oxidized isothermally for up to 72 h at 300–1000 °C using a thermobalance. The microstructure was analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) depth profiling. Broad ion beam milling (BIB) was used to prepare cross-sections. Oxidation behavior depended strongly on the composition of the substrate which consisted of a Mo(Si,Al) 2 matrix and the minority phases Mo 5(Si,Al) 3 and Al 2O 3. At 300–500 °C the mass gains were small with parabolic kinetics, oxidation resulting in a mixture of oxides that reflects the substrate composition. At 600 and 700 °C the oxide scale is thin and protective and depleted in molybdenum, a mass loss occurring due to MoO 3 vaporization. At 1000 °C a protective α-alumina scale forms.

Ion implantation and energy loss effect during high-voltage pulsed glow discharge in a tube

Plasma parameters of high-voltage pulsed glow discharge in a tube were studied using a static probe and optical emission spectrometry. Experiment results show that two kinds of plasma can be obtained in the tube and a virtual anode can be formed at the center of the tube. The potential of the virtual anode is about 20%–30% of the applied bias. The Auger electron spectroscopy depth profile shows that the peak depth of the implanted ions in the tube is about 70%–80% of that outside the tube, owing to the virtual anode.

Determination of the relative sputtering yield of carbon to tantalum by means of Auger electron spectroscopy depth profiling

AbstractThe relative sputtering yield of carbon with respect to tantalum was determined for 1 keV Ar+ ion bombardment in the angular range of 70°–82° (measured from surface normal) by means of Auger electron spectroscopy depth profiling of C/Ta and Ta/C bilayers. The ion bombardment‐induced interface broadening was strongly different for the C/Ta and Ta/C, whereas the C/Ta interface was found to be rather sharp, the Ta/C interface was unusually broad. Still the relative sputtering yields (YC/YTa) derived from the Auger electron spectroscopy depth profiles of the two specimens agreed well. The relative sputtering yields obtained were different from those determined earlier on thick layers, calculated by simulation of SRIM2006 and by the fitting equation of Eckstein. The difference increases with increase of angle of incidence. Copyright © 2009 John Wiley & Sons, Ltd.

Characteristics of indium-free GZO/Ag/GZO and AZO/Ag/AZO multilayer electrode grown by dual target DC sputtering at room temperature for low-cost organic photovoltaics

We compared the electrical, optical, structural and surface properties of indium-free Ga-doped ZnO (GZO)/Ag/GZO and Al-doped ZnO (AZO)/Ag/AZO multilayer electrodes deposited by dual target direct current sputtering at room temperature for low-cost organic photovoltaics. It was shown that the electrical and optical properties of the GZO/Ag/GZO and AZO/Ag/AZO multilayer electrodes could be improved by the insertion of an Ag layer with optimized thickness between oxide layers, due to its very low resistivity and surface plasmon effect. In addition, the Auger electron spectroscopy depth profile results for the GZO/Ag/GZO and AZO/Ag/AZO multilayer electrodes showed no interfacial reaction between the Ag layer and GZO or AZO layer, due to the low preparation temperature and the stability of the Ag layer. Moreover, the bulk heterojunction organic solar cell fabricated on the multilayer electrodes exhibited higher power conversion efficiency than the organic solar cells fabricated on the single GZO or AZO layer, due to much lower sheet resistance of the multilayer electrode. This indicates that indium-free GZO/Ag/GZO and AZO/Ag/AZO multilayer electrodes are a promising low-cost and low-temperature processing electrode scheme for low-cost organic photovoltaics.

Annealing and oxidation study of Mo–Ru hard coatings on tungsten carbide

As a protective hard coating on glass molding dies, Mo–Ru coatings were fabricated on binderless tungsten carbide substrates by RF magnetron sputtering. The Mo–Ru deposits were deposited at 550 °C, which revealed a columnar structure with a major axis perpendicular to the substrate. To evaluate the performance of hard coating in a realistic glass molding environment, the annealing effect was studied by heating the samples at 600 °C under the atmosphere constructed with a steady flow of nitrogen and controlled oxygen content of 12 ppm. The oxygen was absorbed into the Mo–Ru deposits, which affected the phase stability and mechanical properties. The Auger electron spectroscopy depth profiles certified the difference of oxidation resistance between Mo-rich and Ru-rich deposits. The X-ray photoelectron spectroscopy proved the valence variation of Mo in the near surface, accompanied by the introduction of oxygen ions. A scale of MoO 3 and a Mo-depleted transition zone near the surface were pointed out by the transmission electron microscopy investigation on the Mo-rich deposit. On the other hand, the Ru-rich deposits absorbed oxygen in a less content and behaved higher hardness after annealing in the glass molding atmosphere, and became an appropriate protective coating for the die material.

Comparative Investigation of Transparent ITO/Ag/ITO and ITO/Cu/ITO Electrodes Grown by Dual-Target DC Sputtering for Organic Photovoltaics

We investigated the characteristics of transparent indium tin oxide (ITO)/Ag/ITO (IAI) and ITO/Cu/ITO (ICI) multilayer electrodes grown by continuous dual-target dc sputtering for bulk heterojunction organic solar cells (OSCs). The IAI and ICI multilayer electrodes show a significant reduction in their sheet resistance and resistivity with increasing thickness of the Ag and Cu layers, respectively, despite the very small thickness of ITO (80 nm). However, the IAI electrode exhibits a much higher optical transmittance in the visible wavelength region under optimized conditions due to the more effective surface plasmon resonance of the Ag layer than that of the Cu layer. The Auger electron spectroscopy depth profile results for the IAI and ICI electrodes show that there is no severe interfacial reaction between the metal (Ag or Cu) layers and the ITO layers due to the high formation enthalpy of the Ag–O and Cu–O phases at room temperature. Moreover, the OSC fabricated on the IAI electrode shows a higher power conversion efficiency (3.26%) than the OSC prepared on the ICI electrode (2.78%) due to its high optical transmittance in the region of 400–600 nm corresponding to the absorption wavelength range of the organic active layer. This indicates that the IAI multilayer electrode is a promising transparent conducting electrode for OSCs or flexible OSCs due to its very low resistivity and high optical transmittance in the 400–600 nm range.

Effect of gelatin additions on the corrosion resistance of cerium based conversion coatings spray deposited on Al 2024-T3

The corrosion resistance of cerium based conversion coatings on Al 2024-T3 was improved by the addition of a water soluble gelatin to the coating solution. Auger electron spectroscopy depth profiling showed that coatings deposited from solutions containing 800–3200 ppm gelatin were ~ 400 nm thick, while coatings deposited from solutions with 0–200 ppm gelatin were ~ 850 nm thick. The thinner coatings exhibited reduced surface cracking and spalling. Open circuit potential measurements during deposition showed that adding gelatin to the coating solution resulted in a more negative and stable potential with increasing gelatin concentrations. Visually, increasing gelatin concentrations promoted the formation of stable bubbles that covered panel surfaces, which limited transport of cerium species to the surface and decreased the deposition rate. X-ray diffraction analysis revealed that only coatings deposited from solutions containing 400–3200 ppm gelatin could be converted to CePO 4H 2O during post-treatment, potentially improving the corrosion resistance compared to coatings deposited from solutions without gelatin.