Auger Electron Spectroscopy Depth Profiling Research Articles

Crystalline and Amorphous Electroless Co-W-P Coatings

Electroless deposition onto polycrystalline (Cu, Au) and amorphous (Ni-P) substrates was applied to prepare Co-W-P coatings of two types: crystalline (hexagonal close packed, hcp), with low phosphorus content about 2.4–2.7 atom %, and amorphous, with P concentration within 7.4–8.3 atom %. Tungsten content varied typically in the narrow range of 2.9–3.7 atom % in both types of coatings. Atomic force microscopy revealed substantial difference in their morphology. Polycrystalline Co-W-P coatings consist of grains of stacked plates (lamellas), confirmed by transmission electron microscopy also. Amorphous films are smoother and uniform. The crystalline structure promotes the surface oxidation to a higher extent than the amorphous structure, as shown by the X-ray photoelectron spectroscopy (XPS). Auger electron spectroscopy depth profiles display oxidation, smoothly diminishing toward the inside of the crystalline films. Amorphous coatings are oxidized only at the surface. Inside both types of coatings, however, all alloy components are in nonoxidized form, according to XPS data. Differential scanning calorimetry (DSC) studies of amorphous coatings revealed three transformation peaks, ascribed to a crystallization of hypoeutectic alloy and a transition of Co-based hcp phase into face-centered cubic. Magnetic properties variation with temperature is in agreement with DSC results.

Unexpectedly high sputtering yield of carbon at grazing angle of incidence ion bombardment

The relative sputtering yield of amorphous carbon with respect to polycrystalline nickel at Ar-ion bombardment was determined by means of Auger electron spectroscopy depth profiling as a function of the angle of incidence and projectile energy in the ranges of 49°–88° and 0.3–1keV, respectively. It was found that the relative sputtering yield YC∕YNi strongly increases with angle of incidence from 49° to 82°. At around 80° the sputtering yield of C is higher than that of Ni. Above 82° no dependence on the angle of incidence was found. The relative sputtering yield weakly depends on the energy of the projectile. The experimental results will be explained by the help of transport of ion in solid (TRIM) simulations.

Operating model for scandia doped matrix scandate cathodes

In this paper, scandate cathodes with scandia doped tungsten matrices are studied. Attempts are made to clarify some interesting phenomena presented in the whole process. The sub-micron porous tungsten matrix with uniformly distributed Sc 2O 3 was formed by quasi-spherical scandia doped W particles. During impregnation the reaction between Sc 2O 3 and barium aluminates impregnant results in the formation of compounds, preferentially of Ba 2ScAlO 5. But after the subsequent ultrasonic water cleaning, Ba 2ScAlO 5 is dissolved and mostly removed from the surface region. In the activation process, Ba and Sc re-aggregate to the surface. A uniformly distributed Sc and Ba layer on surface of tungsten substrate after proper activation has been verified by the results of high resolution scanning Auger microscopy (SAM) and Auger electron spectroscopy (AES) depth profile. For such cathodes typical emission of more than 30 A/cm 2 space charge limited current density at 850 °C b has been achieved. However, the uniform distribution of Sc and Ba on surface still seems not be able to remedy the abnormal Schottky effect. We propose that a surface multi-layer containing Ba, Sc and O, formed after proper activation on the W base, is the reason for copious emission and abnormal Schottky effect of such cathodes.

Passivation of AlGaAsSb∕InGaAsSb∕GaSb photodiodes using aqueous (NH4)2S solution and polyimide encapsulation

We studied passivation effects of treatment in aqueous (NH4)2S (ammonium sulfide) solution and polyimide encapsulation on AlGaAsSb∕InGaAsSb∕GaSb mesa photodiodes. X-ray photoelectron spectroscopy on InGaAsSb material revealed that (NH4)2S passivation reduces oxide bonds, increases III-V bonds, and produces sulfide bonds. Auger electron spectroscopy depth profiling shows a 1:1 replacement of oxygen by sulfur. The percentage of oxygen replaced by sulfur is about 30% at the surface and decays with the depth. Polyimide encapsulation of the photodiode mesa sidewall not preceded by (NH4)2S passivation reduces the dark current of the photodiodes at −0.5V bias by 3.6 times while additional 9.2 times reduction is obtained when it is preceded by (NH4)2S passivation. The dark current performance of devices did not degrade for 240 days after the combined passivation, indicating a promising long-term stability. The capacitance of devices treated with the combined passivation exhibits a standard deviation three times smaller than those with polyimide encapsulation only.

Realization of improved metallization‐Ti/Al/Ti/W/Au ohmic contacts to n‐GaN for high temperature application

Tungsten metal layer was used for the first time as an effective diffusion barrier for the standard Ti/Al/Ti/Au ohmic metallization scheme to obtain thermally stable ohmic contact suitable for high temperature applications. Comparative studies were performed on three distinct metallization schemes: 1) standard GaN/Ti/Al/Ti/Au, 2) GaN/Ti/Al/W/Au, and 3) GaN/Ti/Al/Ti/W/Au. For the GaN with doping level of 5 × 1017 cm–3, the lowest specific contact resistance for the Ti/Al/Ti/W/Au metallization scheme annealed in argon at 750 °C for 30 sec was 5 × 10–6 Ω.cm2, which is comparable to the standard Ti/Al/Ti/Au scheme. X-ray diffractions (XRD), auger electron spectroscopy (AES) depth profiling, field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (TEM) revealed that the Ti/Al/Ti/W/Au metallization has superior morphology and microstructural properties compared to standard Ti/Al/Ti/Au metallizations. Remarkably, this metallization was able to withstand thermal aging at 500 °C for 50 hrs with only marginal morphological and electrical deterioration. These studies revealed that the utilization of a compound diffusion barrier stack, as in the Ti/Al/Ti/W/Au metallization, yields electrically, structurally, and morphologically superior metallizations with exceptional thermal stability. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ga 1−xMn xSb grown on GaSb with mass-analyzed low-energy dual ion beam deposition

The Ga 1− x Mn x Sb samples were fabricated by the implantation of Mn ions into GaSb (1 0 0) substrate with mass-analyzed low-energy dual ion beam deposition system, and post-annealing. Auger electron spectroscopy depth profile of the Ga 1− x Mn x Sb samples showed that the Mn ions were successfully implanted into GaSb substrate. Clear double-crystal X-ray diffraction patterns of the Ga 1− x Mn x Sb samples indicate that the Ga 1− x Mn x Sb epilayers have the zinc-blende structure without detectable second phase. Magnetic hysteresis-loop of the Ga 1− x Mn x Sb epilayers were obtained at room temperature (293 K) with alternating gradient magnetometry.

Characterization of Pd/Ni/Au ohmic contacts on p-GaN

A low-resistance ohmic contact to Mg-doped p-type GaN grown by metal-organic chemical vapor deposition (MOCVD) with a carrier concentration of 2 × 10 17 cm −3 using Pd/Ni/Au metallization was formed. An anneal at 500 °C for 1 min in a flowing N 2 ambient produced an excellent ohmic contact with a specific contact resistivity as low as 2.4 × 10 −5 Ω cm 2. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) depth profiles of Pd/Ni/Au contacts annealed at 500 °C demonstrated a strong correlation between Ni and Pd interdiffusion toward the GaN surface and a reduction in specific contact resistance. The low contact resistance is attributed to the reduction of the native oxide by Ni diffusion along with the formation of Pd and Ni related-gallide phases at the p-GaN surface region.

Characterization of oxide layers on amorphous Zr-based alloys by Auger electron spectroscopy with sputter depth profiling

Amorphous Zr–Cu–Ni–Al–[Ti, Nb] ribbons prepared by melt spinning under argon atmosphere were subjected to electrochemical investigations. Passive films developed at potentiostatic anodic polarization in sulphuric acid solution were investigated by Auger electron spectroscopy (AES) and sputter depth profiling. Changes in the shape of the Auger peaks have been analyzed by factor analysis of the spectra obtained during depth profiling. Pronounced changes in shape and position occur for the Zr, Al, and Ti Auger transitions, but not for Cu and Ni. At least three different peak shapes for O(KVV) were found and attributed to different oxygen binding states. The alloy composition has no significant effect on the thickness and composition of the oxide layer. In multi-element alloys preferential sputtering is a common phenomenon. In the steady state of sputtering, a significant depletion in Cu is found. At the oxide/metal interface, a distinct enrichment of copper is found for all alloys and treatments. The degree of this Cu enrichment depends on the pretreatment. It is higher for the electrochemically-passivated samples than for samples with oxide layers grown during melt spinning.

Spatial and chemical interface asymmetry in Fe/MgO/Fe(001) heterostructures

The chemical nature of the different interfaces and possible segregation effects are studied in fully epitaxial Fe/MgO/Fe (001) oriented heterostructures fabricated by combined sputtering plus laser ablation deposition techniques. Auger electron spectroscopy depth profiling experiments showed that the interfaces of the MgO spacer with the Fe layers are different, the inner MgO/Fe being spatially broader and with an FeO interlayer, while that of the outer Fe/MgO is spatially narrower with no evidence of FeO formation. This spatial and chemical asymmetry is interpreted in terms of the different deposition procedures, which affect the formation of both interfaces. No Fe segregation in the MgO layers or MgO segregation in the Fe films is observed.

Low resistance ohmic contact to p-type GaN using Pd∕Ir∕Au multilayer scheme

Ohmic contacts on p-type GaN utilizing Pd∕Ir∕Au metallization were fabricated and characterized. Metallized samples that were rapid thermally annealed at 400°C for 1min exhibited linear current-voltage characteristics. Specific ohmic contact resistivities as low as 2×10−5Ωcm2 were achieved. Auger electron spectroscopy and x-ray photoelectron spectroscopy depth profiles of annealed Pd∕Ir∕Au contact revealed the formation of Pd- and Ir-related alloys at the metal–semiconductor junction with the creation of Ga vacancies below the contact. The excellent contact resistance obtained is attributed to the formation of these Ga vacancies which resulted in the reduction of the depletion region width at the junction.

Investigation of Electroplating-Induced Degradation of PMZNT Relaxor Ferroelectrics

Resistance degradation of lead magnesium niobate-based (PMZNT) ceramics during nickel electroplating was investigated using resistivity measurement and auger electron spectroscopy (AES) analysis. It was found that the resistivity of the ceramics remained nearly unchanged at the initial stage of the electroplating, and, as electroplating time increased, the resistivity decreased rapidly. An AES depth profile analysis of a degraded specimen showed oxygen content in the surface to be lower than the theoretical value, and the relationship of oxygen content and detection depth was obtained. The results indicated that Pb 2+ and Nb 5+ were reduced to lower valence states and oxygen in the lattice was lost, thereby leading to a generation of oxygen vacancies. Hence, the conductivity of the dielectrics was enhanced. The results also indicated that only the outermost surface had suffered the reducing effect induced by hydrogen generated during nickel electroplating, whereas the bulk material remained impervious.

Film thickness degradation of Au/GaN Schottky contact characteristics

Electrical characteristics of Au/n-GaN Schottky contacts with different Au film thicknesses up to 1300 Å, have been investigated using current–voltage ( I– V) and capacitance–voltage ( C– V) techniques. Results show a steady decrease in the quality of the Schottky diodes for increasing Au film thickness. I– V measurements indicate that thin (<500 Å) film Schottky diodes show significantly better rectification characteristics than those of thick Au films (>500 Å). Depth profiling Auger electron spectroscopy (AES) shows that the width of the Au/GaN junction interface increases with increasing Au thickness, suggesting considerable inter-mixing of Au, Ga and N. The results have been interpreted in terms of Ga out-diffusion from the GaN giving rise to gallium vacancies that in turn act as sites for electron–hole pair generation within the depletion region. The study supports the recent suggestion that gallium vacancies associated with threaded dislocations are playing an important role in junction breakdown.

Low Resistance and High Reflectance Pt/Rh Contacts to p-Type GaN for GaN-Based Flip Chip Light-Emitting Diodes

We report on a Pt(8 nm)/Rh(200 nm) metallization scheme for use in low resistance and high reflectance ohmic contacts to p-GaN for use in flip chip light-emitting diodes (FCLED) applications. The thermal annealing of a Pt/Rh contact at 500°C led to linear current-voltage characteristics with a specific contact resistance of while the as-deposited Pt/Rh contact showed nonohmic characteristics. It was also shown that the 500°C annealed contact produces a high reflectance of 62% at a wavelength of 460 nm. Auger electron spectroscopy depth profiles and glancing-angle X-ray diffraction results indicated that the low contact resistance of the annealed sample can be attributed to the formation of Ga-Pt and Ga-Rh intermetallic phases. Furthermore, the electrical performance of an FCLED with the Pt/Rh reflector scheme was superior to that of a FCLED with a Ni/Au/Ag reflector scheme. © 2004 The Electrochemical Society. All rights reserved.

Nanolaminated Al2O3–TiO2 thin films grown by atomic layer deposition

Alternately stacked Al2O3–TiO2 nanolaminates were grown by atomic layer deposition (ALD) using the precursors of trimethyl aluminum, tetraisopropyl titanium, and water at growth temperature of 250°C. Laminated configuration and nanostructural features were analyzed by cross-sectional transmission electron microscopy (TEM), depth-profiling Auger electron spectroscopy (AES) and X-ray diffraction (XRD). These material characterizations were well interpreted with layer-by-layer ALD growth mode and material properties of single oxide films, namely conformal growth of amorphous Al2O3 with a growth rate of 1.0Å/cycle and polycrystalline anatase TiO2 with 0.3Å/cycle. In addition, the dependences of leakage current density on applied electric field were measured for several nanolaminates with different TiO2 content and bilayer, single Al2O3 and TiO2 layer, thickness. Obtained results exhibit the successful tailoring of leakage current densities and permittivity with adjusting layer thicknesses in the nanolaminates. These properties were discussed in terms of utility as a current-controlling layer in direct current thin-film electroluminescence (TFEL) devices.

Investigation of Mn-implanted n-Si by low-energy ion beam deposition

Mn ions were implanted to n-type Si(0 0 1) single crystal by low-energy ion beam deposition technique with an energy of 1000 eV and a dose of 7.5×10 17 cm −2. The samples were held at room temperature and at 300 °C during implantation. Auger electron spectroscopy depth profiles of samples indicate that the Mn ions reach deeper in the sample implanted at 300 °C than in the sample implanted at room temperature. X-ray diffraction measurements show that the structure of the sample implanted at room temperature is amorphous while that of the sample implanted at 300 °C is crystallized. There are no new phases found except silicon both in the two samples. Atomic force microscopy images of samples indicate that the sample implanted at 300 °C has island-like humps that cover the sample surface while there is no such kind of characteristic in the sample implanted at room temperature. The magnetic properties of samples were investigated by alternating gradient magnetometer (AGM). The sample implanted at 300 °C shows ferromagnetic behavior at room temperature.

Depth Profiling Analysis of Tarnish Films on Copper Formed during Short-Term Outdoor Exposure by Glow Discharge Optical Emission Spectroscopy

Abstract The elemental depth profiling of tarnish films were analyzed at the early stages of atmospheric copper corrosion by glow discharge optical emission spectroscopy (GDOES), where the tarnish films had been formed by exposing copper plates to various outdoor environments, i.e., urban, rural/coastal, and hot-spring sites, for 1 month. Since GDOES probed a large surface area, on the order of millimeters, the depth profiles reflected macroscopic-averaged characteristics over this area, which are representative of real corroded surfaces. GDOES complemented previous analyses, i.e., Auger electron spectroscopy (AES), x-ray diffraction, field-emission scanning electron microscopy (FE-SEM), coulometric reduction, and x-ray photoelectron spectroscopy, and provided a better understanding of these tarnish films. In particular, the previous findings from microscopic FE-SEM observation and AES depth profiling were well supported by the GDOES results. With GDOES we observed the generation and distribution of cupri...

Factor analysis of AES sputter depth profiles of B, C and N sequentially implanted in silicon

AbstractIn this work, a crystalline silicon wafer was sequentially implanted with N+, C+ and $\hbox{BF}_{2}^{+}$ ions of 25, 21 and 77 keV and doses up to 5 × 1017, 1 × 1018 and 5 × 1017 cm−2, respectively. The energies and doses of the respective ions were chosen according to standard simulations to obtain an implanted layer with the appropriate BC2N composition. After that, the sample was annealed at 1200°C for 3 h.The sample has been characterized by Auger electron spectroscopy (AES) depth profiling in order to get a quantitative analysis of the components in the sample. Factor analysis has been used to deconvolute the different chemical states of Si, B, C and N, and to identify different compounds. The analysis of the as‐implanted sample indicates the formation of a quaternary compound with an estimated average composition of SiB0.3C0.6N0.1 in a broad region close to the surface, as well as a ternary compound with an estimated average composition of SiB0.1N0.05 at the interface with the silicon substrate. The major effect induced by the thermal treatment is observed at the interface which shows an out‐diffusion of boron from the interface. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Corrosion of Metals by Bio-Oil Obtained by Vacuum Pyrolysis of Softwood Bark Residues. An X-ray Photoelectron Spectroscopy and Auger Electron Spectroscopy Study

The corrosion of three metals (aluminum, copper, and austenitic steel (SS 316)) at 80 °C by bio-oil obtained by vacuum pyrolysis of softwood bark residue was studied using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) depth profiling. The bio-oil is very acidic (pH value of 3) and contains significant amounts of water and metal ions that are not present in significant concentrations in the feedstock material (e.g. Cu, Pb, and Fe). These metals were most probably leached from the pyrolysis reactor or peripheral installations. Aluminum and, to a much smaller degree, copper were corroded by bio-oil, whereas SS 316 was not affected. Oxide and/or hydroxide layers were formed on all three metals. However, in the case of aluminum and copper, these layers did not protect the underlying metal against further oxidation. For SS 316, after initial modification of the surface (e.g., leaching of Fe species), subsequent oxidation was prevented by the chromium oxide layer.

Development of CIS solar cells with evaporated InxSeybuffer layer

We investigated CuInSe2 (CIS) based solar cells with InxSey (IS) deposited by evaporation and CdS deposited by the Chemical Bath Deposition (CBD) method, as buffer layer. I–V measurements gave the following output parameters for cells fabricated using IS as buffer: Jsc= 30.8 mA/cm2, Voc = 0.44V, FF ≈ 0.6 and η = 8.3 % with 100 mW/cm2 irradiance. Solar cells fabricated using a CdS buffer layer deposited on a CIS substrate prepared under the same conditions as those employed in the fabrication of CIS/ IS/ZnO cells, gave the following results: Voc = 0.43 V, Jsc = 34 mA/cm2, FF ≈ 0.63 and η = 9.2%. Auger Electron Spectroscopy (AES) depth profiles measurements were carried out to identify possible diffusion processes affecting the cell operation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermal Stability of Spin Valves Incorporating New Amorphous ZrAl Alloy Films as Under and Capping Layers

We investigated the thermal stability and interdiffusion behavior of new amorphous ZrAl-based spin valves (SVs) and compared them with similarly structured Ta-based top (T) and bottom (B) SVs. The magneto-resistance (MR) ratios of ZrAl-based T-and B-SVs were enhanced from 8.49 to 9.14% and from 6.91 to 7.54%, respectively. The Ta-based SVs degraded relatively quickly at elevated temperatures because of interlayer diffusion. In contrast, the MR ratio of the ZrAl-based T-SV decreased by only 6.6% (9.14 /spl rarr/ 8.54%), while that of the B-SV increased by 2.3% (7.54 /spl rarr/ 7.71%), after annealing at 300/spl deg/C for 240 min. This result and the Auger electron spectroscopy (AES) depth profile clearly showed that ZrAl-based SVs have high interdiffusion resistance. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses of the root-mean-square (rms) roughness indicated that the ZrAl layer (0.162 nm) has a smoother interface than the Ta layer (0.431 nm). The ZrAl-based SV has a fine, dense microstructure. It resists interdiffusion at elevated temperature and results in superior thermal stability over traditional Ta-based SVs.