Shape Of Depth Profile Research Articles

The impact of electric field strength on the accuracy of boron dopant quantification in silicon using atom probe tomography

This study investigates the impact of the surface electric field on the quantification accuracy of boron (B) implanted silicon (Si) using atom probe tomography (APT). The Si Charge-State Ratio (CSR(Si) = Si2+/Si+) was used as an indirect measure of the average apex electric field during analysis. For a range of electric fields, the accuracy of the total implanted dose and the depth profile shape determined by APT was evaluated against the National Institute of Standards and Technology Standard Reference Material 2137. The radial (non-)uniformity of the detected B was also examined. At a higher surface electric field (i.e., a greater CSR(Si)), the determined B dose converges on the certified dose. Additionally, the depth profile shape tends towards that derived by secondary ion mass spectrometry. This improvement coincides with a more uniform radial B distribution, evidenced by desorption maps. In contrast, for lower surface electric fields (i.e., a lower CSR(Si)), the B dose is significantly underestimated, and the depth profile is artificially stretched. The desorption maps also indicate a highly inhomogeneous B emission localized around the center of the detector, which is believed to be an artifact of B surface migration on the tip of the sample. For the purposes of routine investigations of semiconductor devices using APT, these results illustrate the potential origin of quantification artifacts and their severity at different operating conditions, thus providing pathways towards best practices for accurate and repeatable measurements.

Cortical depth profiles of auditory and visual 7T functional MRI responses in human superior temporal areas.

Invasive neurophysiological studies in nonhuman primates have shown different laminar activation profiles to auditory vs. visual stimuli in auditory cortices and adjacent polymodal areas. Means to examine the underlying feedforward vs. feedback type influences noninvasively have been limited in humans. Here, using 1-mm isotropic resolution 3D echo-planar imaging at 7 T, we studied the intracortical depth profiles of functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) signals to brief auditory (noise bursts) and visual (checkerboard) stimuli. BOLD percent-signal-changes were estimated at 11 equally spaced intracortical depths, within regions-of-interest encompassing auditory (Heschl's gyrus, Heschl's sulcus, planum temporale, and posterior superior temporal gyrus) and polymodal (middle and posterior superior temporal sulcus) areas. Effects of differing BOLD signal strengths for auditory and visual stimuli were controlled via normalization and statistical modeling. The BOLD depth profile shapes, modeled with quadratic regression, were significantly different for auditory vs. visual stimuli in auditory cortices, but not in polymodal areas. The different depth profiles could reflect sensory-specific feedforward versus cross-sensory feedback influences, previously shown in laminar recordings in nonhuman primates. The results suggest that intracortical BOLD profiles can help distinguish between feedforward and feedback type influences in the human brain. Further experimental studies are still needed to clarify how underlying signal strength influences BOLD depth profiles under different stimulus conditions.

Multi-mode magnesium diffusion in sanidine: Applications for geospeedometry in magmatic systems

The duration of magmatic processes can occur over a wide range of time from as long as millennia to as short as hours. It is therefore important to have a variety of geospeedometers that are sensitive to different timescales. The diffusivity of Mg in K-bearing feldspar such as sanidine has previously been a critical gap in the application of geospeedometry, as sanidine is a ubiquitous phase in dacites and rhyolites and also hosts a variety of major and trace elements with variable diffusivities. Here we present the results of a series of 1-atm diffusion experiments in order to constrain the diffusivity of Mg in sanidine. Two compositions of sanidine (Or71 and Or82) and crystallographic orientations (c-parallel and c-perpendicular) are investigated, showing Mg diffusion is isotropic with little to no resolvable major element compositional dependence. Additionally, Mg diffusion in sanidine simultaneously operates by a fast- and slow-path diffusion mechanism as suggested by irregular depth profile shapes that do not conform to an analytical solution to the diffusion equation. Therefore, we employed a model that considers multi-site diffusion reactions in order to determine diffusion coefficients. The following Arrhenius relationships are obtained for Mg diffusion in sanidine:DOr71-Fast = 4.2 E-12 exp (−275 ± 14 kJ mol−1/RT) m2 s−1,DOr71-Slow = 1.4 E-05 exp (−369 ± 15 kJ mol−1/RT) m2 s−1,DOr82-Fast = 1.6 E-05 exp (−283 ± 14 kJ mol−1/RT) m2 s−1,DOr82-Slow = 3.9 E-04 exp (−405 ± 15 kJ mol−1/RT) m2 s−1.Fast-path diffusivities for Mg in sanidine are similar to those of Mg in plagioclase determined by Van Orman et al. (2014). Slow-path diffusion in sanidine is at least a few orders of magnitude slower than fast-path diffusion. Slow-path diffusion may be rate-limited by exchange reactions between divalent cations such as Ba and Sr with K, and Mg with Al. Fast-path diffusion likely operates by interstitial and/or vacancy diffusion. Equipped with these new diffusivities, this study calculates timescales for magmatic rejuvenation that likely initiated the Lava Creek Tuff supereruption at Yellowstone Caldera to be as short as weeks but no more than a few decades. This work also demonstrates the complexity that may exist in experimentally-derived geospeedometers and the importance of careful application to natural systems.

The Anisotropic Stress-Induced Diffusion and Trapping of Nitrogen in Austenitic Stainless Steel during Nitriding

Plasma nitriding of austenitic stainless steels at moderate temperatures is considered in the presented work. The anisotropic aspects of stress-induced diffusion and influence of nitrogen traps are investigated by kinetic modeling based on rate equations. The model involves diffusion of nitrogen in the presence of internal stress gradients induced by penetrating nitrogen as the next driving force of diffusion after the concentration gradient. The diffusion equation takes into account the fact that nitrogen atoms reside in interstitial sites and in trapping sites. Stress-induced diffusion has an anisotropic nature and depends on the crystalline orientation while trapping–detrapping is isotropic. The simulations are done considering the synergetic effects of both mechanisms and analyzing the properties of both processes separately. Theoretical curves are compared with experimental results taken from the literature. Good agreement between simulated and experimental results is observed, and gives the possibility to find real values of parameters needed for calculations. The nitrogen depth profile shapes, the dependences of nitrogen penetration on nitriding time and on diffusivity, are analyzed considering crystalline orientation of steel single crystal.

Performance and Accuracy of the Shifted Laser Surface Texturing Method

A shifted laser surface texturing method (sLST) was developed for the improvement of the production speed of functional surface textures to enable their industrial applicability. This paper compares the shifted method to classic methods using a practical texturing example, with a focus on delivering the highest processing speed. The accuracy of the texture is assessed by size and circularity measurements with the use of LabIR paint and by a depth profile measurement using a contact surface profiler. The heat accumulation temperature increase and laser usage efficiency were also calculated. The classic methods (path filling and hatch) performed well (deviation ≤ 5%) up to a certain scanning speed (0.15 and 0.7 m/s). For the shifted method, no scanning speed limit was identified within the maximum of the system (8 m/s). The depth profile shapes showed similar deviations (6% to 10%) for all methods. The shifted method in its burst variant achieved the highest processing speed (11 times faster, 146 mm2/min). The shifted method in its path filling variant achieved the highest processing efficiency per needed laser power (64 mm2/(min·W)), lowest heat accumulation temperature increase (3 K) and highest laser usage efficiency (99%). The advantages of the combination of the shifted method with GHz burst machining and the multispot approach were described.

Morphology of Shear-Induced Colloidal Aggregates in Porous Media: Consequences for Transport, Deposition, and Re-entrainment.

Colloid deposition in granular media is relevant to numerous environmental problems. Classic filtration models assume a homogeneous pore space and largely ignore colloid aggregation. However, substantial evidence exists on the ubiquity of aggregation within porous media, suggesting that deposition is enhanced by it. This work studies the deposition process in relation to aggregate size and structure. We demonstrate that aggregation is induced at typical groundwater velocities by comparing the repulsive DLVO force between particle pairs to the hydrodynamic shear force opposing it. Column experiments imaged with high-resolution X-ray computed tomography are used to measure aggregate structure and describe their morphology probability distribution and spatial distribution. Aggregate volume and surface area are found to be power-law distributed, while Feret diameter is exponentially distributed with some flow rate dependencies caused by erosion and restructuring by the fluid shear. Furthermore, size and shape of aggregates are heterogeneous in depth, where a small number of large aggregates control the concentration versus depth profile shape. The range of aggregate fractal dimensions found (2.22-2.42) implies a high potential for restructuring or breaking during transport. Shear-induced aggregation is not currently considered in macroscopic models for particle filtration, yet is critical to consider in the processes that control deposition.

Damage formation and Er structural incorporation in m-plane and a-plane ZnO

The various crystallographic orientations in semiconductors as ZnO exhibit different resistivity under the ion beam irradiation/implantation. Study of the various crystallographic orientations is mandatory for nano-structured semiconductor system development. This paper reports on the implantation damage build-up, structural modification and Er dopant position in a-plane and m-plane ZnO implanted with Er+ 400 keV ions at the ion fluences 5 × 1014, 2.5 × 1015, 5 × 1015 cm−2 and subsequently annealed at 600 °C in O2 atmosphere using Rutherford Back-Scattering spectrometry (RBS) in channelling mode as well as using Raman spectroscopy. Strongly suppressed surface damage formation was observed in both crystallographic orientations compared to the deep damage growth with the increased ion implantation fluence. More progressive damage accumulation appeared in m-plane ZnO compared to a-plane ZnO. Simultaneously, the strong Er out-diffusion depth profile in m-plane ZnO accompanied by the damage accumulation at the surface was observed after the annealing. Contrary, the surface recovery accompanied by Er concentration depth profiles keeping a normal distribution with a small maximum shift to the surface was observed in a-plane ZnO. Different structure recovery and Er behaviour was evidenced in a-plane and m-plane ZnO by RBS-C, moreover Raman spectroscopy proved a lower damage at higher ion fluences introduced in a-plane ZnO compared to m-plane. The structure modifications were discussed in connection with a damage accumulation and Er concentration depth profile shape in various ZnO crystallographic orientations in as-implanted and as-annealed samples.

Scaling Relations Associated with Millimeter Continuum Sizes in Protoplanetary Disks

Abstract We present a combined, homogenized analysis of archival Submillimeter Array (SMA) and Atacama Large Millimeter/submillimeter Array (ALMA) observations of the spatially resolved 340 GHz (870 μm) continuum emission from 105 nearby protoplanetary disks. Building on the previous SMA survey, we infer surface brightness profiles using a simple model of the observed visibilities to derive the luminosities (L mm) and effective sizes (R eff) of the continuum emission. With this sample, we confirm the shapes, normalizations, and dispersions for the strong correlations between L mm, M * (or L *), and found in previous studies. We also verify the continuum size–luminosity relation determined from the SMA survey alone (extending to an order of magnitude lower L mm), demonstrating that the amount of emission scales linearly with the emitting surface area. Moreover, we identify new, although weaker, relationships between R eff and the host and accretion properties, such that disks are larger around more massive hosts with higher accretion rates. We explore these interrelated demographic properties with some highly simplified approximations. These multi-dimensional relationships can be explained if the emission is optically thick with a filling factor of ∼0.3, or if the emission is optically thin and disks have roughly the same optical depth profile shapes and normalizations independent of host properties. In both scenarios, we require the dust disk sizes to have a slightly sublinear relationship with the host mass and a non-negligible dispersion (∼0.2 dex at a given M *).

Calculation of dose conversion coefficients for radioactive cesium in contaminated soil by depth and density

Radiation dose to personnel on the ground contaminated with radioactive cesium after nuclear power plant accident depends on cesium activity, depth profile of the activity, and soil mass density. A dosimetry method was developed to calculate radiation dose resulting from external exposure to radioactive cesium in soil with arbitrary depth profile. Dose conversion coefficients to calculate effective dose based on cesium radioactivity in soil were produced by using a radiation transport code. The dose conversion coefficient was produced for each 1 cm thickness disk source by soil depth by changing soil mass density from 0.5 to 2 g/cm3. Radiation dose due to a volumetric source can be calculated with summation of radiation doses from multiple thin disk sources. When radioactive cesium is distributed within 0–1 cm depth of soil with mass density of 1 g/cm3, effective dose conversion coefficients were 6.2 × 10−6 and 2.4 × 10−6 mSv/h per kBq/m2 for 134Cs and 137Cs nuclides, respectively. Effective doses decreased exponentially with increasing soil depth or mass density. Radiation dose on the contaminated ground can be calculated with the dose database established in this study for any shape of depth profile.

Estimation of the optical errors on the luminescence imaging of water for proton beam

Although luminescence imaging of water during proton-beam irradiation can be applied to range estimation, the height of the Bragg peak of the luminescence image was smaller than that measured with an ionization chamber. We hypothesized that the reasons of the difference were attributed to the optical phenomena; parallax errors of the optical system and the reflection of the luminescence from the water phantom. We estimated the errors cause by these optical phenomena affecting the luminescence image of water. To estimate the parallax error on the luminescence images, we measured the luminescence images during proton-beam irradiation using a cooled charge-coupled camera by changing the heights of the optical axis of the camera from those of the Bragg peak. When the heights of the optical axis matched to the depths of the Bragg peak, the Bragg peak heights in the depth profiles were the highest. The reflection of the luminescence of water with a black wall phantom was slightly smaller than that with a transparent phantom and changed the shapes of the depth profiles. We conclude that the parallax error significantly affects the heights of the Bragg peak and the reflection of the phantom affects the shapes of depth profiles of the luminescence images of water.

Quantitative estimation of nonmonotonic residual stress depth-profiles using an extended Kypris-Jiles model of the magnetic Barkhausen noise spectrum

Using nondestructive techniques to quantitatively estimate residual stresses along the depth is necessary to improve the ability to predict the real fatigue life of pieces for many applications. Magnetic Barkhausen noise has been proven to successfully estimate the residual stress at the surface produced by machining, plastic deformation, phase transformation or surface treatments such as shot peening, also allowing one to obtain information of the residual stress depth-profile in shot peened pieces which presented similar depth-profile shapes. However, residual stress depth-profiles with nonmonotonic or different shapes have not been successfully estimated. In the present study, an extended approach is developed in order to estimate these stresses independent of the shape of the residual stress depth-profile. The approach proposed here improves an existing model of the Barkhausen noise spectrum (Kypris-Jiles model) by adding the effect of the attenuation of the applied magnetic field on the Barkhausen noise. This extended approach is used to estimate the residual stress depth-profiles of samples with different depth-profiles using a calibration process. The approach is validated by estimating the residual stress depth-profiles, with errors smaller than 70 MPa in a depth of 130 μm, in all the samples studied.

Development of a global ocean mercury model with a methylation cycle: Outstanding issues

We present a newly developed global ocean mercury (Hg) transport and biogeochemistry model and use preanthropogenic equilibrium simulations to highlight physical and chemical processes which reveal significant knowledge gaps that need to be addressed. As with previous 3‐D ocean Hg model work we use a bulk chemistry scheme based on particulate organic carbon remineralization. We also include an explicit methylation cycle based on available reaction rates. The methylation to demethylation rate ratio based on various field studies is found to be inconsistent with the concentration ratios measured in the Southern Ocean around Antarctica and in the Arctic. There is also model‐measurement disagreement in the old waters of the tropical and North Pacific Ocean. The model produces an intermediate water maximum in total Hg in this region reflecting the higher age of water which is absent in observations. The model also underestimates total Hg concentrations in the deepest waters in this region. These disagreements in depth profile shape point to an inadequate representation of scavenging and sedimentation and possibly seabed emission or remobilization of Hg. In addition, the total Hg distribution differences compared to previous model work reflect sensitivity to ocean model transport characteristics and in particular the tracer diffusion. The residence time of Hg in the global ocean and the surface evasion flux of elemental Hg is sensitive to such model aspects. We find a global ocean Hg turnover time against sediment burial to be about 1100 years which is within the range of previous studies.

The effects of the 2001 Barotropic intrusion of bottom-water upon the vertical distribution of inorganic iodine in the Gotland Deep

The distribution of iodide, iodate and total inorganic iodine in the water column of the Gotland Deep, in July 2001 and April 2002, is described. The general stratification of the water column is inferred from hydrographic measurements and nutrient analyses. These identify a well-oxygenated, estuarine surface layer (0–60m), an oxy-cline (60–125m), and a sulphidic zone (125–232m). Fortuitously, the two sampling events occurred either side of a major barotropic intrusion which renewed the bottom water, thereby uplifting the earlier water column by about 20–30m. The effects of this upon the iodine system is reported. The shapes of depth profiles for total inorganic iodine and their salinity counterpart are similar, with total inorganic iodine concentration rationalised to 35 salinity (RTiI) of 680nM in waters between 100 and 232m, and 75 and 232m in July 2002 and April 2002, respectively. Meanwhile, between 0 to 60m RTiI=440nM at both samplings. As a result of this it is argued that upwards transport of iodine and salt in the Gotland Deep is closely coupled. A weaker co-variation between total inorganic iodine and phosphate concentration is taken to indicate that re-mineralisation of organic-I probably takes place mainly in the sediment, and not in the water column. In effect, re-mineralisation in the sediment produces a pool of salty, iodine rich bottom water, which by advection-diffusivity, moves up the water column. The uplift between the samplings was found to enrich the intermediate water (∼70–100m) in iodide, which was subsequently oxidised to iodate in the period between the samplings. It is argued that the alternative possibility of an injection of iodate direct into this intermediate zone by means of a baroclinic intrusion, although possible, is unlikely. Greater integration of the mechanistic oceanographic approach underpinning this study into future 129I radiological assessments is advocated, to bring significant opportunities offered by the radio-chemistry, into marine chemistry.

A porewater-based stable isotope approach for the investigation of subsurface hydrological processes

Abstract. Predicting and understanding subsurface flowpaths is still a crucial issue in hydrological research. We present an experimental approach to reveal present and past subsurface flowpaths of water in the unsaturated and saturated zone. Two hillslopes in a humid mountainous catchment have been investigated. The H2O(liquid) – H2O(vapor) equilibration laser spectroscopy method was used to obtain high resolution δ2H vertical depth profiles of pore water at various points along two fall lines of a pasture hillslope in the southern Black Forest, Germany. The Porewater-based Stable Isotope Profile (PSIP) approach was developed to use the integrated information of several vertical depth profiles of deuterium along transects at the hillslope. Different shapes of depth profiles were observed in relation to hillslope position. The statistical variability (inter-quartile range and standard deviation) of each profile was used to characterize different types of depth profiles. The profiles upslope or with a weak affinity for saturation as indicated by a low topographic wetness index preserve the isotopic input signal by precipitation with a distinct seasonal variability. These observations indicate mainly vertical movement of soil water in the upper part of the hillslope before sampling. The profiles downslope or at locations with a strong affinity for saturation do not show a similar seasonal isotopic signal. The input signal is erased in the foothills and a large proportion of pore water samples are close to the isotopic values of δ2H in streamwater during base flow conditions indicating the importance of the groundwater component in the catchment. Near the stream indications for efficient mixing of water from lateral subsurface flow paths with vertical percolation are found.

EM38 for volumetric soil water content estimation in the root-zone of deep vertosol soils

Electromagnetic induction sensors, such as EM38, are used widely for monitoring and mapping soil attributes via the apparent electrical conductivity (EC a) of the soil. The sensor response is the depth-integrated combination of the depth-response function of the EM38 and ‘local’ electrical conductivity (EC az) at depth. In deep, Vertosol soils, assuming the instrument depth-response function is not perturbed by the soil and where volumetric moisture content at depth ( θ v( z)) dominates EC az, EM38 should be capable of predicting average moisture content without recourse to mathematically complicated, and unstable profile inversion processes. Firstly a multi-height EM38 experiment was conducted over deep Vertosol soils to confirm the veracity of the EM38 depth-response function and test the concomitant hypothesis of the EM38 response being an integrated (i.e. additive) combination of depth-response function and θ v( z). Secondly, depth profiles of moisture content were used to calibrate the EM38 to infer average θ v( z) within the ‘root-zone’ of crop plants—here taken to be surface—0.8 m and surface—1.2 m. EM38 calibration was performed using soil samples acquired from both extracted cores and excavated pits. Mathematical summation of measured θ v( z) from sectioned cores and the known depth-response function of the EM38 was found to explain 99% and 97% of the variance in measured EC a for horizontal and vertical dipole configurations at multiple sensor heights above the ground. Average θ v from surface to 0.8 m ( θ ¯ 0.8 ) and surface to 1.2 m ( θ ¯ 1.2 ) explained only 37% and 46% of the variance in on-ground EC a for vertical dipole configuration measurements compared to 55% and 56% of the variance for horizontal dipole configuration. In a separate validation experiment, the shape of the vertical moisture profile proved highly influential in determining the ability of the calibration equations to infer underlying average moisture content, especially where the depth profile shapes differed between sensor calibration and subsequent field validation (for example following rainfall or irrigation).

Highly accurate shave-off depth profiling by simulation method

Shave-off depth profiling, our own unique technique, utilizes a focused ion beam (FIB) micro-machining process to provide the depth profile. It is known that the FIB has long tails outside of the beam. The long tails affect the shape of depth profile and make depth resolution worse. The influence of long tails can be minimized by depositing a protection film on the sidewall or changing the speed of shave-off scan. In this study, we discussed about shave-off scanning speed toward depth direction by using simulation method and accomplished highly accurate shave-off depth profiling.

Depth distribution of infrared absorption of ion irradiated PETP

Abstract The depth distributions of infrared absorption of PETP (polyethyleneterepthalate, ‘mylar') were measured for a number of different ion irradiation conditions. It turned out that at low fluences the depth profiles resemble the ones of the transferred electronic energy distribution. With increasing fluence the depth profiles of IR absorption approach the ones of the transferred nuclear energy distribution, thus reflecting the increasing polymer destruction. The earlier assumed correlation of the depth profile shapes with the ratio of electronic to nuclear energy transfer can thus be ruled out.

Study of Nitrogen Implanted in Aluminum at Various Doses

Abstract Experimental and theoretical studies are carried out to understand transport of nitrogen in aluminum during implantation process. 60 keV and 120 keV N2 + ion are implanted in pure Al substrates at doses ranging from l×l017 to 9×l017 N-atoms per cm2. RBS and Glancing angle XRD studies are carried out. RBS studies show that the depth profiles are gaussian in nature at low doses and gradually become rectangular in shape as the dose increases. XRD analysis reveals that AlN is formed even at low doses. Theoretical simulations of depth profiles at low dose, include displacement mixing and radiation enhanced diffusion, which are modelled to be described by a diffusion like process. Effective diffusion coefficient in radiation environment is found to be equal to 8×l0−16 cm2.sec−1. At high doses, when new N-atoms are added during implantation their transport gets linked with the already formed AlN. This leads to a rectangular shape of depth profiles observed at high doses.

Identification and quantification of Cu contamination on GaAs surfaces

AbstractSecondary ion mass spectrometry has been used to identify the presence of Cu contamination on undoped semiinsulating GaAs wafer surfaces following polishing under certain conditions. The presence of a contaminating species on the wafer surface is indicated by the influence of pre‐etch treatments on electrical measurements performed on heat‐treated wafers, with and without Si implants. The identification of Cu as a contaminant is confirmed by photoluminescence measurements. With the appropriate wafer preparation process, the level of Cu contamination is below the SIMS detection limit of <1 × 1016 atoms cm−3.In the SIMS analysis of the surface‐contaminated wafers, the Cu depth profile shape was dependent on the primary beam bombardment energy, suggesting a chemical segregation of Cu out of the altered layer, a redistribution that is known to occur in Si.To quantify the surface concentration of Cu, GaAs wafers were deliberately contaminated with Cu, heat treated and analysed with glow discharge mass spectrometry and SIMS to provide a cross‐calibration.

Effects of crystallinity on depth resolution in sputter depth profiles

AbstractFor sputter depth profiling the effect of the layer crystallinity on the resolution of the underlying interfaces was investigated. By applying D. Onderdelinden's model of monocrystal sputtering (Appl. Phys. Lett. 8, 189 (1966); Can. J. Phys. 46, 739 (1968)) and J. Lindhard's approach to axial ion channelling (Phys. Lett. 12, 126 (1965); K. Dan. Vidensk. Selsk. Mat. Fys. Medd. 34, No. 14 (1965)) to textured and non‐textured polycrystalline layers, it is shown that the interface resolution under these layers is largely affected by the channelling of incident ions. The strong dependence of channelling on the orientation of individual grains leads to extremely non‐uniform erosion and poor interface resolution. This model of polycrystalline layer sputtering reproduces well the dependence of depth profile shape and depth resolution on layer thickness, ion energy and incidence angle, as shown for sputter depth profiling through textured aluminium layers by inert gas ions. In the case of higher ion masses, the observed effects are slightly overestimated by the model, as anticipated from the inherent limitations of the Lindhard and the Onderdelinden approaches. The implications of channelling for depth profiles of polycrystalline layers are discussed and conclusions are drawn for appropriate selection of sputter parameters to ensure optimum depth resolution. The effects of sample temperature, continuous rotation of the sample during sputter erosion and reactive ion sputtering are also discussed.