Detection Of Secondary Ions Research Articles

The NanoSIMS-HR: The Next Generation of High Spatial Resolution Dynamic SIMS.

The high lateral resolution and sensitivity of the NanoSIMS 50 and 50L series of dynamic SIMS instruments have enabled numerous scientific advances over the past 25 years. Here, we report on the NanoSIMS-HR, the first major upgrade to the series, and analytical tests in a suite of sample types, including an aluminum sample containing silicon crystals, microalgae, and plant roots colonized with a symbiotic fungus. Significant improvements have been made in the Cs+ ion source, high voltage (HV) control, stage reproducibility, and other aspects of the instrument that affect performance. The modified design of the NanoSIMS-HR thermal-ionization Cs+ source enables a 5 pA primary ion beam to be focused into a 100 nm spot, a ∼2.5-fold increase compared to Cs+ sources on previous instruments (∼2 pA at 100 nm). The brightness of the new Cs+ source enables an ultimate lateral resolution as high as 30 nm and improved detection limits for a given analysis area. Sample stage movement accuracy is higher than 500 nm, enabling many-fold higher throughput automated analyses. With the new HV control, the primary ion beam impact energy can be reduced from 16 to 2 keV, which enables higher depth resolution during depth profiling (a 2-fold improvement), albeit with a 5-fold decrease in lateral resolution. In the NanoSIMS-HR, the secondary ion column and detection system are identical to those used in the previous series, and the isotopic analysis performance is as precise as in previous NanoSIMS instruments.

Quality assurance method for monitoring of lateral pencil beam positions in scanned carbon-ion radiotherapy using tracking of secondary ions.

Ion beam radiotherapy offers enhances dose conformity to the tumor volume while better sparing healthy tissue compared to conventional photon radiotherapy. However, the increased dose gradient also makes it more sensitive to uncertainties. While the most important uncertainty source is the patient itself, the beam delivery is also subject to uncertainties. Most of the proton therapy centers used cyclotrons, which deliver typically a stable beam over time, allowing a continuous extraction of the beam. Carbon-ion beam radiotherapy (CIRT) in contrast uses synchrotrons and requires a larger and energy-dependent extrapolation of the nozzle-measured positions to obtain the lateral beam positions in the isocenter, since the nozzle-to-isocenter distance is larger than for cyclotrons. Hence, the control of lateral pencil beam positions at isocenter in CIRT is more sensitive to uncertainties than in proton radiotherapy. Therefore, an independent monitoring of the actual lateral positions close to the isocenter would be very valuable and provide additional information. However, techniques capable to do so are scarce, and they are limited in precision, accuracy and effectivity. The detection of secondary ions (charged nuclear fragments) has previously been exploited for the Bragg peak position of C-ion beams. In our previous work, we investigated for the first time the feasibility of lateral position monitoring of pencil beams in CIRT. However, the reported precision and accuracy were not sufficient for a potential implementation into clinical practice. In this work, it is shown how the performance of the method is improved to the point of clinical relevance. To minimize the observed uncertainties, a mini-tracker based on hybrid silicon pixel detectors was repositioned downstream of an anthropomorphic head phantom. However, the secondary-ion fluence rate in the mini-tracker rises up to 1.5×105 ions/s/cm2 , causing strong pile-up of secondary-ion signals. To solve this problem, we performed hardware changes, optimized the detector settings, adjusted the setup geometry and developed new algorithms to resolve ambiguities in the track reconstruction. The performance of the method was studied on two treatment plans delivered with a realistic dose of 3Gy (RBE) and averaged dose rate of 0.27Gy/s at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. The measured lateral positions were compared to reference beam positions obtained either from the beam nozzle or from a multi-wire proportional chamber positioned at the room isocenter. The presented method is capable to simultaneously monitor both lateral pencil beam coordinates over the entire tumor volume during the treatment delivery, using only a 2-cm2 mini-tracker. The effectivity (defined as the fraction of analyzed pencil beams) was 100%. The reached precision of (0.6 to 1.5) mm and accuracy of (0.5 to 1.2) mm are in line with the clinically accepted uncertainty for QA measurements of the lateral pencil beam positions. It was demonstrated that the performance of the method for a non-invasive lateral position monitoring of pencil beams is sufficient for a potential clinical implementation. The next step is to evaluate the method clinically in a group of patients in a future observational clinical study.

Quantitative depth distribution analysis of elements in high alloy steel using MCs+-SIMS approach

Elemental composition analysis in alloy samples using secondary ion mass spectrometry (SIMS) suffers from matrix effects which hamper the analytical results. These matrix effects arise due to numerous factors like change in surface work function due to primary ion beam implantation, presence of reactive chemical species in the samples or on the sample surface, sample composition, chamber pressure etc. which changes the ionization probability of secondary ion species and hence produces non-linear effects in the production of secondary ions. In order to minimize these effects, Cs+ primary ion beam in conjunction with MCs+ (M being the element of interest) secondary ion monitoring (MCs+-SIMS) approach has been used. The MCs+-SIMS approach has been extensively used for quantitative depth distribution analysis in semiconductor samples but limited reports are available for the analysis of alloys sample. In the present work, the MCs+-SIMS approach has been utilized to determine the chemical composition and quantitative depth distribution of multiple elements (C, Si, Ni, Mn, Cr, Co, Mo and Fe) in high alloy steel samples. Quantitative depth distribution analysis revealed a non-homogenous distribution of elements on the steel surface which can be due to the presence of surface oxide layers. The minor and major constituents such as Cr, Mo; Mn, Ni; and Si; were determined with relative error of <2%, 6% and 5%, respectively. Surface distribution analyses of these elements were also carried out using both Cs+ and O2+ primary ion beams. An interesting and contrasting feature has been observed for surface distribution analysis carried out with MCs+ as compared to M+ secondary ion detection mode. It was observed that the surface distribution patterns of non-homogenous elements showed homogenous distribution patterns in case of MCs+ secondary ion monitoring approach. This anomaly can be attributed to the difference in formation mechanism of MCs+ and M+ secondary ions.

Solar Wind Sputtering Rates of Small Bodies and Ion Mass Spectrometry Detection of Secondary Ions

AbstractSolar wind interactions with the surfaces of asteroids and small moons eject atoms and molecules from the uppermost several nanometers of regolith grains through a process called sputtering. A small fraction of the sputtered species, called secondary ions, leave the surface in an ionized state, and these are diagnostic of the surface composition. Detection of secondary ions using ion mass spectrometry (IMS) provides a powerful method of analysis due to low backgrounds and high instrument sensitivities. However, the sputtered secondary ion yield and the atomic composition of the surface are not 1‐to‐1 correlated. Thus, relative yield fractions based on experimental measurements are needed to convert measured spectra to surface composition. Here available experimental results are combined with computationally derived solar wind sputtering yields to estimate secondary ion fluxes from asteroid‐sized bodies in the solar system. The Monte Carlo simulation code SDTrimSP is used to estimate the total sputtering yield due to solar wind ion bombardment for a diverse suite of meteorite and lunar soil compositions. Experimentally measured relative secondary ion yields are analyzed to determine the abundance of refractory species (Mg+, Al+, Ca+, and Fe+) relative to Si+, and it is shown that relative abundances indicate whether a body is primitive or has undergone significant geologic reprocessing. Finally, estimates of the sputtered secondary ion fluxes are used to determine the IMS sensitivity required to adequately resolve major element ratios for nominal orbital geometries.

5 MeV C&lt;sub&gt;60&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;イオンを用いたペプチドの透過型二次イオン質量分析

Transmission secondary ion mass spectrometry (transmission SIMS) of thin films of leucine-enkephalin using MeV C60+ primary ions was performed to examine the advantage of the combination with detection of secondary ions emitted in the forward direction in efficient emission of the intact molecular ions. Leucine-enkephalin thin films deposited on self-supporting SiN membranes were bombarded with 5 MeV C60 ions, and positive secondary ions emitted in the forward and backward directions were mass-analyzed. The yield of fragment ions emitted in the forward direction was remarkably reduced compared to the backward direction, while the yield of intact molecular ions was reduced to a minor extent depending on the thickness of the peptide film. This suggests a potential of forward emission geometry in transmission cluster ion SIMS for less-damage and sensitive analysis of biological materials.

A novel PFIB sample preparation protocol for correlative 3D X-ray CNT and FIB-TOF-SIMS tomography

We present a novel sample preparation method that allows correlative 3D X-ray Computed Nano-Tomography (CNT) and Focused Ion Beam Time-Of-Flight Secondary Ion Mass Spectrometry (FIB-TOF-SIMS) tomography to be performed on the same sample. In addition, our invention ensures that samples stay unmodified structurally and chemically between the subsequent experiments. The main principle is based on modifying the topography of the X-ray CNT experimental setup before FIB-TOF-SIMS measurements by incorporating a square washer around the sample. This affects the distribution of extraction field lines and therefore influences the trajectories of secondary ions that are now guided more efficiently towards the detector. As the result, secondary ion detection is significantly improved and higher, i.e. statistically better, signals are obtained.

Surface and depth distribution of components in high alloy stainless steel using secondary ion mass spectrometry

The direct imaging and depth sensitive analysis capabilities of secondary ion mass spectrometry were effectively utilized for surface and depth distribution analysis of major and trace elements (C, Si, Cr, Mn, Fe, Ni, Co and Mo) in high alloy stainless steel sample. Oxygen (O2+) primary ion beam with positive secondary ion detection mode was selected for surface and depth distribution analysis of elements in stainless steel sample. Qualitative surface distributions of the elements were obtained by area line scan analysis constructed from surface ion distribution images. 3D analyses were also carried out using O2+ primary ion beam in order to investigate spatial distribution of the elements. Surface ion distribution images, 3D analysis and area line scan analysis confirmed the non homogenous spatial distribution of Si and C while other elements Cr, Mn, Fe, Ni, Co and Mo were homogenously distributed over the surface as well as with respect to depth. The non homogenous spatial distribution of Si and C may be due to formation of carbide or precipitates of Si and C. Depth distribution analysis showed uniform depth distribution of all the elements including C and Si within the analysis area of 150μm×150μm.

New sample preparation method using room-temperature direct bonding in backside SIMS analysis

Secondary ion mass spectrometry (SIMS) is one of the tools to investigate the dopant or impurity profiles of the semiconductor materials. In particular, the backside SIMS is a useful technique to examine the diffusion of dopant at the surface while minimizing knock-on effect. However, it is very difficult to prevent insulating samples from charging when O2+ source is used for positive secondary ion detection in magnetic sector SIMS. In order to overcome the problem, the authors have employed a new sample preparation method using a room-temperature direct bonding (RTDB). The authors investigated the depth profiling of insulating samples, which were stacked on a dielectric silicon dioxide films with silicon wafer as a magnetic sector SIMS instrument. The samples treated with and without RTDB were compared, and the results show that the depth profiles of RTDB-treated sample could be obtained no sign of charge-up in the backside SIMS analysis.

Temperature dependent Cs retention, distribution, and ion yield changes during Cs+ bombardment SIMS

Combining Cs+ bombardment with positive secondary molecular ion detection (MCs+) can extend the analysis capability of secondary ion mass spectrometry (SIMS) from the dilute limit (&amp;lt;1 at. %) to matrix elements. The MCs+ technique has had great success in quantifying the sample composition of III–V semiconductors. However, the MCs+ has been less effective at reducing the matrix effect for group IV materials, particularly Si-containing compounds. The lack of success in quantifying group IV materials is primarily attributable to the high Cs surface concentrations overloading the sample surface and lowering ion yields. The Cs overload issue is caused by the mobility and relocation of the implanted Cs to the surface during an analysis. Critical to understanding the material-dependent success of the MCs+ technique and elucidating the Cs mobility is understanding how Cs is incorporated and distributed into the sample and how the Cs surface concentration affects the ionization processes. The authors provide both new insight for improving the MCs+ technique by investigating the Cs retention, distribution, and ion yield differences between group III–V and IV materials and a greater understanding of the temperature-dependent mobility and relocation of the implanted Cs. There have been many studies on improving the MCs+ technique; however, our novel approach to use temperature as a means of controlling the Cs mobility has not been previously explored. Cesium build-up curves were acquired to assess the in situ Cs incorporation differences. By utilizing the newly developed variable temperature stage on our SIMS, cesium build-up curves were acquired over a wide range of temperatures (−150 to 300 °C) to show the temperature-dependent relocation of Cs and the effect it has on the ionization processes. Additionally, Cs ionization and neutralization were quantified as a function of Cs fluence and temperature. The Cs retention and distribution differences were determined ex situ by measuring the Cs concentration using heat-treatment x-ray photoelectron spectroscopy and heat-treatment medium energy ion scattering. These results allow for a more thorough understanding of the material-dependent success of the MCs+ technique, the Cs+-sample interaction, and the temperature component of the Cs mobility.

Time-of-flight secondary neutral & ion mass spectrometry using swift heavy ions

We report on a new time-of-flight (TOF) spectrometer designed to investigate sputtering phenomena induced by swift heavy ions in the electronic stopping regime. In this experiment, particular emphasis is put on the detection of secondary ions along with their emitted neutral counterparts in order to examine the ionization efficiency of the sputtered material. For the detection of neutral species, the system is equipped with a pulsed VUV laser for post-ionization of sputtered neutral atoms and molecules via single photon ionization at a wavelength of 157nm (corresponding to 7.9eV photon energy). For alignment purposes and in order to facilitate comparison to nuclear sputtering conditions, the system also includes a 5keV Ar+ ion beam directed to the same sample area. The instrument has been added to the M1-branch beam line at the German accelerator facility in Darmstadt (GSI) and was tested with 4.8MeV/u Au26+ ions impinging onto various samples including metals, salts and organic films. It is found that secondary ion and neutral spectra obtained under both bombardment conditions can be acquired in an interleaved manner throughout a single accelerator pulse cycle, thus making efficient use of valuable beam time. In addition, the keV ion beam can be intermittently switched to dc mode between subsequent data acquisition windows and accelerator pulses in order to ensure reproducible surface conditions. For the case of a dynamically sputter cleaned metal surface, comparison of secondary ion and neutral signals obtained under otherwise identical instrumental conditions reveals a nearly identical ionization probability of atoms emitted under electronic and nuclear sputtering conditions.

Experimental study of the organic ion intensity distribution in the ion imaging of coated polymer fibres with S-SIMS

Time-of-Flight Static Secondary Ion Mass Spectrometry excels in probing the molecular composition of the outer monolayer of flat samples with a lateral resolution in the sub-μm range. However, the method faces significant methodological problems in the case of non-conducting samples with high topography or surface curvature, such as fibres, yarns or fabrics. Specifically, the useful secondary ion yield in a given spot on the fibre depends on the local incidence angle, the height above the earthed sample holder, the position relative to the axis of the mass analyser and the extent of the local surface charging. This study has focused on the empiric reduction of the useful ion yield variations observed in the ion images of fibres with diameter of 25 and 100μm. Up to now, most literature data consider the analysis of fibres positioned along or perpendicular to the projection of the projectile beam in the plane of the sample surface because these specific geometries facilitate the interpretation of the ion images. However, it has been discovered that the diagonal orientation of the fibre in the field-of-view largely reduces the ion yield variations for fibres with a small diameter (25μm). The situation is different for fibres with a diameter of 100μm. In that case, the ion images contain no secondary ion counts for the pixels referring to a significant part of the fibre. In particular, the resulting lack of delineation between the shadow zone in the front of the fibre and the boundary of the fibre hampers the practical use of the ion images A fourfold decrease of the extraction voltage or a 20% increase of the distance between sample holder and extraction electrode is found to improve the detection of secondary ions from the part of the fibre facing towards the impinging primary ion beam. These observations have been tentatively related to the mass analyser acceptance and its dependence on the delicate balance between conflicting effects such as field strength and curvature of the field lines, secondary ion emission angle and initial kinetic energy and difference in local surface potential due to the position in the extraction field and charge build-up during analysis.

Study and optimisation of SIMS performed with He+ and Ne+ bombardment

The combination of the high-brightness He+/Ne+ atomic level ion source with the detection capabilities of secondary ion mass spectrometry (SIMS) opens up the prospect of obtaining chemical information with high lateral resolution and high sensitivity on the Zeiss ORION helium ion microscope (HIM). A feasibility study with He+ and Ne+ ion bombardment is presented in order to determine the performance of SIMS analyses using the HIM. Therefore, the sputtering yields, useful yields and detection limits obtained for metallic (Al, Ni and W) as well as semiconductor samples (Si, Ge, GaAs and InP) were investigated. All the experiments were performed on a Cameca IMS4f SIMS instrument which was equipped with a caesium evaporator and oxygen flooding system. For most of the elements, useful yields in the range of 10−4 to 3×10−2 were measured with either O2 or Cs flooding. SIMS experiments performed directly on the ORION with a prototype secondary ion extraction and detection system lead to results that are consistent with those obtained on the IMS4f. Taking into account the obtained useful yields and the analytical conditions, such as the ion current and typical dwell time on the ORION HIM, detection limits in the at% range and better can be obtained during SIMS imaging at 10nm lateral resolution with Ne+ bombardment and down to the ppm level when a lateral resolution of 100nm is chosen. Performing SIMS on the HIM with a good detection limit while maintaining an excellent lateral resolution (<50nm) is therefore very promising.

Isotopic study on metalorganic chemical vapor deposition of manganite films

Isotopic labeling experiments using 18O2 were carried out to understand the decomposition and oxidation reactions of source molecules in the metalorganic chemical vapor deposition (MOCVD) of strontium-doped lanthanum manganite films. The isotopic ratios of oxygen incorporated in the deposited films were determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS) in both negative and positive secondary ion detection modes. The obtained M18O+/M16O+ (M=La, Sr, Mn) ratios showed good agreement with the corresponding 18O−/16O− ratios. The oxygen incorporation from the oxidant gas (18O2) to the strontium oxide films is dominant under typical deposition conditions, while the majority of oxygen in the lanthanum oxide films originates from the ligands of the source molecules. In the complex oxide film deposition, an interaction occurred with another metal source molecules in the film deposition reaction. As a result, about three quarters of MO bonds of the original source molecules were preserved in the La0.7Sr0.3MnO3 film formation.

Normal-incidence Electron Gun alignment method for negative ion analysis on insulators by magnetic sector SIMS

On Cameca magnetic sector SIMS (Secondary Ion Mass Spectrometer) instruments, detection of negative secondary ions during analysis of insulating materials represents one of the more challenging uses of the instrument. This is because the highest sensitivity is achieved using a positive Cesium primary ion beam to sputter a sample held at a negative potential. The combination of positive charge from the primary beam and the acceleration of negative ions from the sample surface results in the build-up of positive charge in the sputtered area. The Normal-incidence Electron Gun (NEG) is used to deliver electrons to neutralize the positive charge build-up. At typical conditions, the electron beam diameter is rather small (∼150μm), so it is critical to align the NEG to overlay the analysis area as closely as possible. A new method has been developed to utilize cathodoluminescence of gallium nitride (GaN) to visually align the electron gun. This approach is shown to result in reproducible analyses of insulating phases, including depth profiling of oxide on semiconductor materials, bulk analyses for hydrogen, and oxygen isotope ratio microanalyses.

Simultaneous detection and localization of secondary ions and electrons from single large cluster impacts.

The use of large cluster primary ions (e.g. C60, Au400) in secondary ion mass spectrometry has become prevalent in recent years due to their enhanced emission of secondary ions, in particular, molecular ions (MW ≤ 1500 Da). The co-emission of electrons with SIs was investigated per projectile impact. It has been found that SI and electrons yields increased with increasing projectile energy and size. The use of the emitted electrons from impacts of C60 for localization has been demonstrated for cholesterol deposited on a copper grid. The instrumentation, methodologies, and results from these experiments are presented.

Real‐time localization of single C60 impacts with correlated secondary ion detection

AbstractWe assembled hardware and software for the synchronized detection of electrons and ions emitted under the impacts of the individual C60+ and C602+ ions. A projectile impact is localized via the ejected electron(s) with an emission electron microscope (EEM). The (x,y) coordinates of each impact combined with the corresponding record of detected secondary ions (Sis), allow the construction of mass‐selected surface maps.The setup comprises a custom‐built ToF‐SIMS with a C601, 2+ source, an EEM with an electron imaging detector consisting of dual microchannel plates (MCPs), phosphor screen and a 1.3 megapixel CMOS camera. The electron pulse on the aluminized phosphor screen triggers the camera resulting in a frame with the electron image. It also triggers the ToF electronics resulting in a suite of SI time records corresponding to each individual impact event. The data processing and management are handled by custom software including combination of the positional and the mass spectrometric information from each impact.The present study demonstrates the feasibility of mapping a surface by localizing the SI emission from single C602+ impacts. A spatial resolution of 1.3 µm has been obtained. Interestingly, maps of coemitted SIs from a given localization display chemically resolved information from an emission area of ∼102 nm2. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Bi 3 + cluster primary ions in SIMS depth profiling of YBaCuO high-temperature superconductor films

SIMS depth profiling of YBa2Cu3O7 high-temperature superconductor films was performed using a TOF.SIMS-5 instrument. A new approach was proposed to obtain additional information on the phase composition of YBa2Cu3O7 films based on detection of cluster secondary ions.

Dynamic SIMS ion microscopy imaging of individual bacterial cells for studies of isotopically labeled molecules

A CAMECA IMS-3f SIMS ion microscope instrument capable of 500 nm spatial resolution was used for imaging single bacterial cells in the soil treated with 13C-labeled phenol in desired treatments. After formaldehyde fixation, the soil samples containing bacterial cells were smeared on the silicon substrate. The O 2 + primary ion beam was used for the detection of negative secondary ions. Images of individual bacterial cells were recorded on a CCD camera in masses 24, 25, 26, and 27 signals. The respective mass images represented contributions from the molecular ions of interest, for example 24( 12C 2) −, 25( 13C 12C) −, 26( 12C 14N) −, 27( 13C 14N) −, as well as interfering mass species associated with a particular mass. However, in cells treated with 13C-labeled phenol the enhancement of signals in masses 25 and 27 images due to increased signals of 25( 13C 12C) − and 27( 13C 14N) −, respectively, unequivocally indicated the presence of 13C-labeled phenol in bacterial cells in direct comparison to the samples treated only with unlabeled phenol. The ratio images of masses 25/24 and 27/26 from individual cells revealed a cell-to-cell heterogeneity in the labeling with 13C-phenol. This study indicates that the ion microscope can be applied effectively for studies of labeled molecules in microbiology and biogeochemistry.

Fragmentation of molecular compounds on silicon wafers and low dielectric constant materials studied by time‐of‐flight secondary ion mass spectrometry using a polyatomic ion source

AbstractRecent time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) studies using primary cluster ion sources such as Aun+, SFn+, Bin+ or C60+ have shown polyatomic ions to be more appropriate for the detection of high mass molecular secondary ions than monoatomic ion sources like Ga+, thanks to secondary ion yield and ion formation efficiency enhancements.This work is part of a study aiming at improving molecular compound quantification at the surface of microelectronics industry substrates by taking advantage of a polyatomic ion source in ToF‐SIMS analysis. It focuses on the case of a phthalate‐related contamination. Fundamental parameters like secondary ion yield, damage cross section and secondary ion efficiency were studied as a function of the size and the energy of the primary ions. The substrate composition influence on the ToF‐SIMS results was also studied by comparing several substrates of interest in the microelectronics industry such as silicon wafers and low dielectric constant materials SiOxCyHz.Phthalate‐related secondary ions detected at the surface of the contaminated surfaces were compared and a fragmentation pathway of the di‐isononyl phthalate (DNP) molecule was determined. A drastic improvement of the secondary ion yield was provided when using a polyatomic ion source. Furthermore, a clear increase in damage cross section was observed as a function of the secondary ion size for a given Bin primary ion as well as an increase for a given fragment as a function of the number of Bi atoms in the Bin aggregate. This led to a lower static limit when taking into account higher phthalate fragments and primary ions of larger size. Copyright © 2008 John Wiley &amp; Sons, Ltd.

SIMS quantification of matrix and impurity species in Al xGa 1− xN

The quantification in Al x Ga 1− x N with different AlN mole fraction ( x) is challenging because of matrix effects and charging effects. For quantitative characterization of both matrix and impurity elements in Al x Ga 1− x N, a novel charge neutralization method was employed and calibration curves were created using an O 2 + primary beam with positive secondary ion detection and a Cs + primary beam with negative and MCs + secondary ion detection. Over the range of 0 < x < 0.58, the matrix ion intensity ratios of Al +/Ga + and AlCs +/GaCs + appear linear with the mole fraction ratio x/(1 − x), and the ratio of AlN −/GaN − is linear with AlN mole fraction ( x). The sputter rate decreases as AlN mole fraction increases, while the relative sensitivity factors (RSF's) of impurities have an exponential relationship with AlN mole fraction. These calibration curves allow the quantification of both matrix and impurity species in AlGaN with varying AlN mole fraction. The technique can be employed for impurity control, composition and growth rate determination, as well as structural analysis of the finished optoelectronic and electronic devices.