Secondary Ion Mass Spectrometry Measurements Research Articles

Structural and optical properties of highly Ag-doped TiO2 thin films prepared by flash thermal evaporation

The present study investigates the structural and optical properties of silver (Ag)-doped titanium dioxide (TiO2) thin films prepared via flash thermal evaporation using TiO2 and Ag powders mixture at various mass ratios. The crystallinity and surface morphology of the films were studied by varying the percentage of Ag content. Structural properties were characterized using X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM), while optical properties were assessed through optical transmission spectra analysis. Results indicate that Ag doping enhances crystallinity, as evidenced by XRD and Raman spectroscopy, and induces surface plasmon resonance (SPR) absorption attributed to Ag nanoparticles. SEM micrographs reveal agglomerated silver particles on the film surface, confirming Ag diffusion during annealing. Surface analysis through Secondary Ion Mass Spectrometry (SIMS) measurements illustrated the diffusion of Ag within the TiO2 samples and its subsequent accumulation at the surface. We have suggested that the crystallization observed in the evaporated TiO2-Ag thin films may primarily result from the thermal diffusion of Ag metal rather than the annealing process alone. Optical transmission spectra demonstrate a shift in the absorption edge towards the visible region with increasing Ag concentration, indicating enhanced light absorption properties.

Thickness and Mg doping of graded AlGaN layers: Influence on contact layer's structural and electrical properties for DUV emitters

One of the methods to improve p-doping properties in (Al)GaN-based materials is using a technique called polarization doping. In our study, two sets of p-AlGaN contact layers with different thicknesses of the graded layer were deposited by metalorganic vapor phase epitaxy. The grown samples were investigated by atomic force microscopy, secondary ion mass spectrometry, X-ray diffraction and Hall effect measurements to study the influence of the thickness of the graded Al0.6→0Ga0.4→1N:Mg layer on the structural and the electrical properties of the whole grown structure. Additionally, theoretical calculations for the contact structures with different thicknesses of the p-Al0.6→0Ga0.4→1N graded layer were performed. The obtained results show that the concentration of p-type carriers on the p-GaN/p-AlGaN gradient interface decreases with increasing thickness of the graded layer. Our findings reveal that among the graded structures the highest concentration of holes, 1.2 × 1018 cm−3, was obtained for a structure with 50-nm-thick graded layer, while maintaining low sample resistivity. In addition, it was also shown that non-doping of the graded layer allows to improve electrical properties.

Chromite Reference Materials and Matrix Effects in SIMS Oxygen Isotope Measurements

Secondary ion mass spectrometry (SIMS) measurements of δ18O in nine chromite (Mg, Fe)(Al, Cr, Fe)2O4 samples (Cr# = 0.58–0.79, Mg# = 0.39–0.72) from chromitites and harzburgite have confirmed their intra‐ and inter‐grain isotopic homogeneity, making them suitable reference materials for in situ analysis. The SIMS measurements of the oxygen isotopic composition of these chromites exhibit a range of instrumental mass fractionation (IMF) as a function of the end‐member compositions of the chromite, particularly the magnetite (FeOFe2O3) and spinel (MgAl2O4) components. Functional relationships have been developed to correct for IMF over the compositional range XMag = 0.01 to 0.05, and XSpl = 0.14 to 0.22. We conclude that, to be accurate, SIMS measurements of δ18O must be combined with electron probe microanalyses of the individual analysed spots.

Dislocation density as a factor compensating the polarization doping effect in graded p-AlGaN contact layers

One of the approaches to improve p-doping properties in (Al)GaN-based materials is using a method called polarization doping. In this study, the graded p-AlGaN contact layers were deposited using plasma-assisted molecular beam epitaxy with different III/N ratios. To study the influence of Ga flux on the structural and electrical properties of the grown graded p-AlGaN structures, the samples were investigated using reflection high-energy electron diffraction, atomic force microscopy, secondary ion mass spectrometry, X-ray diffraction, and Hall effect measurements. The electronic structure of the samples was investigated by X-ray absorption near edge spectroscopy, while the polarity of the layers was analyzed by means of transmission electron microscopy. Our study reveals that growing with a higher Ga flux increases Mg incorporation and changes its distribution in the graded layer. However, it was shown that the main factor drastically affecting the magnitude and the type of conductivity in the graded p-AlGaN structures is the dislocation density. The highest hole concentration of ∼3.0×1018 cm−3 was observed for sample grown with a low Ga flux.

Quantification of secondary ion mass spectrometry measurements by using ion‐implanted metallic standards

This research addresses an analytical methodology to quantify elements of interest in fusion‐relevant materials using secondary ion mass spectrometry (SIMS). For this purpose, internal standards have been fabricated by ion implantation to avoid the well‐known matrix effect of this technique. In particular, chromium has been implanted at an energy of 12 MeV using two fluences in high‐purity iron and tungsten matrices together with Si control substrates. The latter were applied to determine the Cr concentration implanted through experimental and semiempirical methods. Specifically, the IBA technique Rutherford backscattering spectrometry (RBS) provided the quantitative results being 3.1 × 1019 at/cm3 and 1.6 × 1019 at/cm3 for the high and low dose, respectively. The SIMS depth profiles of Cr for the Fe and W matrices established an ion implantation depth close to 2 μm on both substrates in agreement with the calculations previously performed by Stopping and Range of Ions in Matter (SRIM) simulations. Correlation between the integration of SIMS profiles and known concentrations of the implanted ion resulted in the calibration curve for each matrix, obtaining the SIMS quantification approach by means of this relative sensitivity factor (RSF). Additionally, a cross‐check of the method by comparing commercial Fe‐Cr alloys with the Cr‐implanted Fe matrices of the present study pointed out the need to produce standards with higher chromium concentrations.

Impact of degradation mechanisms at the cathode/electrolyte interface of garnet-based all-solid-state batteries

All-solid-state batteries have the potential to improve the safety, energy-, and power density of lithium-ion batteries. However, the limited stability of rigid solid-solid interfaces remains a key challenge. The cathode/electrolyte interface is particularly prone to degradation during high-temperature sintering and electrochemical cycling, forming secondary phases that impede charge transport and limit cell performance. Experimental analysis of these phases is challenging since they result in thin resistive films that are sensitive to typical characterization techniques. In this study, we use structure-resolved electrochemical simulations to investigate the impact of resistive phases at the cathode/electrolyte interface on cell performance and identify dominant degradation mechanisms. We extend our simulation framework with a novel resistive film model that accounts for the additional charge transfer resistance at the interface based on interphase properties. Our approach combines continuum simulations with insights from density functional theory and experimental data, including secondary ion mass spectrometry measurements. This allows us, for the first time, to assess the impact of resistive films on the degradation of full-cell performance.

Artifact-free secondary ion mass spectrometry profiling of a full vertical cavity surface emitting laser structure

The optimization of the structure of vertical-cavity surface-emitting lasers (VCSELs) is required to produce more efficient devices. The secondary ion mass spectrometry (SIMS) technique can provide information about the structure and the distribution of dopants and contaminants. However, VCSELs are relatively thick, contain hundreds of layers with varying compositions, and consist of very thin layers. Classical SIMS is prone to artifacts which decreases the quality of the results. In this work, modifications of the SIMS measurement procedures are presented: high incident angle bombardment reduces the mixing effect; optimization of the extraction parameters increases the signal-to-noise ratio from 2.1 to 24.3 dB; Ion polishing and beam service preserves the quality of the measurement. Due to impact energy modulations quantum wells and barriers are registered as box-shaped features. The raw data is free of artifacts and reflects the realistic distribution of elements. Such accuracy may prove invaluable for further optimization of VCSELs.

Diagenetic history of calcite fractures in Vaca Muerta shales (Argentina) inferred from paired Δ47 and fluid inclusion geothermometry

Many low-permeability, hydrocarbon-bearing rocks are productive for petroleum because natural fractures enhance hydrocarbon delivery to wellbores. Exploration and development decisions often must be made in the face of uncertainty about the presence and properties of natural fractures at scales of beds, field and plays, and how they contribute to production. Fractures patterns in subsurface rocks are challenging to predict or characterize owing to the difficulty in obtaining representative samples of fractures and the sparse set of tools for reconstructing how and when fractures grow during sedimentary basin evolution. In this study, we investigate bed-parallel fracture diagenesis in the Vaca Muerta shales (Argentina) based on a set of calcite vein collected from core across a thermal maturity sequence that ranges from the oil to dry gas window. We characterize these samples using secondary ions mass spectrometry (SIMS) measurements of stable isotope ratios, carbonate clumped isotope geothermometry and fluid inclusion analysis. These measurements precisely reconstruct the evolution of fluid geochemistry, temperature and pore fluid pressure during fracture opening. Here we show that within each studied site, all bedding parallel fibrous veins calcite formed at similar ranges of temperature. The fracture mineralization temperature increases substantially at the basin scale, from 90 °C to 120 °C, correlated with host-rock thermal maturity. We compare our constraints on carbonate and fluid temperature with apatite fission track thermal models and find that most of the fractures of the Vaca Muerta shales have formed in a relatively early stage of subsidence of the basin (c.a. 90 to 70 Ma). These ages estimations are consistent with recently published U–Pb ages on calcite veins from the outcropping area (117–61 Ma). The presence of petroleum inclusions (oil, condensate, and gas) in most of the vein's calcite fibers from cores also provides clear evidence that fracture formation was contemporaneous or posterior with petroleum generation, constraining the timing of catagenesis in the Vaca Muerta. Reconstructed paleo pressures conditions of veins formation from fluid inclusion analysis highlight significant fluid overpressure in the shale interval, which likely contributed to fracture initiation and growth. Preserved apparent Δ47 temperatures in fibrous veins carbonates mineralization evolves gradually from 130 °C to 175 °C with increasing host rock thermal maturity. These clumped-isotope-based temperatures are systematically higher than trapping temperatures of associated fluid inclusions; one interpretation of this observation is that carbonate clumped isotope compositions re-equilibrated to near maximum burial conditions by solid-state isotopic re-ordering, yielding a record of the maximum burial temperature the shale unit experienced. The combination of paleothermometry techniques used in this study illustrates the importance of simultaneously exploring several independent geothermometers, particularly the informative combination of fluid inclusion and clumped isotope constraints, which provides a means of understanding the complex diagenesis of old sedimentary rocks that have experienced burial temperatures in the oil and gas thermal windows.

Highlighting the role of 3C–SiC in the performance optimization of (Al,Ga)N‒based High‒Electron mobility transistors

AlN nucleation layer is the key issue for the performance of GaN high frequency telecommunication and power switching systems fabricated after heteroepitaxy on Silicon or Silicon Carbide. In this work, we demonstrate and explain both the low level and the origin of propagation losses in GaN/3C–SiC/Si High Electron Mobility Transistors (HEMTs) at microwaves frequencies, in view of providing efficient circuits. First, it is shown that the use of 3C–SiC as an intermediate layer between the Si substrate and the GaN epitaxial layer drastically decreases RF propagation losses. Using Secondary Ion Mass Spectroscopy (SIMS) measurements, we demonstrate that dopant in-diffusion (both Al and Ga) into the 3C–SiC pseudo-substrate remains confined beneath the interface. Furthermore, by combining scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM), the 2D profile shows the presence of a slightly conductive zone beneath the AlN/3C–SiC interface that is highly limited (less than 50 nm) whatever the growth conditions of the (Al, Ga)N layers on 3C–SiC explaining the low propagation losses obtained for such devices. This behavior differs from the one previously observed for GaN growth on Si substrate. This work demonstrates the importance and efficiency of the 3C–SiC intermediate layer when used as a pseudo-substrate increasing not only the crystalline quality of the subsequent (Al, Ga)N layers but also permits to achieve high potential GaN power devices as it is crucial.

Comparison of δ13 C analyses of individual foraminifer (Orbulina universa) shells by secondary ion mass spectrometry and gas source mass spectrometry.

The use of secondary ion mass spectrometry (SIMS) to perform micrometer-scale in situ carbon isotope (δ13 C) analyses of shells of marine microfossils called planktic foraminifers holds promise to explore calcification and ecological processes. The potential of this technique, however, cannot be realized without comparison to traditional whole-shell δ13 C values measured by gas source mass spectrometry (GSMS). Paired SIMS and GSMS δ13 C values measured from final chamber fragments of the same shell of the planktic foraminifer Orbulina universa are compared. The SIMS-GSMS δ13 C differences (Δ13 CSIMS-GSMS ) were determined via paired analysis of hydrogen peroxide-cleaned fragments of modern cultured specimens and of fossil specimens from deep-sea sediments that were either untreated, sonicated, and cleaned with hydrogen peroxide or vacuum roasted. After treatment, fragments were analyzed by a CAMECA IMS 1280 SIMS instrument and either a ThermoScientific MAT-253 or a Fisons Optima isotope ratio mass spectrometer (GSMS). Paired analyses of cleaned fragments of cultured specimens (n = 7) yield no SIMS-GSMS δ13 C difference. However, paired analyses of untreated (n = 18) and cleaned (n = 12) fragments of fossil shells yield average Δ13 CSIMS-GSMS values of 0.8‰ and 0.6‰ (±0.2‰, 2 SE), respectively, while vacuum roasting of fossil shell fragments (n = 11) removes the SIMS-GSMS δ13 C difference. The noted Δ13 CSIMS-GSMS values are most likely due to matrix effects causing sample-standard mismatch for SIMS analyses but may also be a combination of other factors such as SIMS measurement of chemically bound water. The volume of material analyzed via SIMS is ~105 times smaller than that analyzed by GSMS; hence, the extent to which these Δ13 CSIMS-GSMS values represent differences in analyte or instrument factors remains unclear.

BAlGaN light‐emitting diode emitting at 350 nm

AbstractIn this work, the authors report the first demonstration of an ultraviolet light‐emitting diode (LED) with boron‐containing quantum wells (QWs). Secondary ion mass spectrometry measurements revealed a B concentration of 1% in the first QW with an increase in subsequent QWs and lingering decay into the p‐region, likely attributable to boron's surfactant nature. Electroluminescence emission from the BAlGaN LED was observed at 350 nm, with higher intensity compared to the AlGaN reference LED at low currents. A higher operating voltage compared to the reference LED was also observed which may be attributable to a nanomasking behaviour of boron in (Al)GaN alloys.

Probing Boron Vacancy Complexes in h-BN Semi-Bulk Crystals Synthesized by Hydride Vapor Phase Epitaxy

Hexagonal BN (h-BN) has emerged as an important ultrawide bandgap (UWBG) semiconductor (Eg~6 eV). The crystal growth technologies for producing semi-bulk crystals/epilayers in large wafer sizes and understanding of defect properties lag decades behind conventional III-nitride wide bandgap (WBG) semiconductors. Here we report probing of boron vacancy (VB)-related defects in freestanding h-BN semi-bulk wafers synthesized by hydride vapor phase epitaxy (HVPE). A photocurrent excitation spectroscopy (PES) was designed to monitor the transport of photoexcited holes from deep-level acceptors. A dominant transition line at 1.66 eV with a side band near 1.62 eV has been directly observed, which matches well with the calculated energy levels of 1.65 for the VB-H deep acceptor in h-BN. The identification of VB complexes via PES measurement was further corroborated by the temperature-dependent dark resistivity and secondary ion mass spectrometry measurements. The results presented here suggested that it is necessary to focus on the optimization of V/III ratio during HVPE growth to minimize the generation of VB-related defects and to improve the overall material quality of h-BN semi-bulk crystals. The work also provided a better understanding of how VB complexes behave and affect the electronic and optical properties of h-BN.

Carrier transport mechanism of Mg/Pt/Au Ohmic contact on p-GaN/AlGaN/GaN platform with ultra-low resistivity

In this work, the carrier transport mechanism of Mg/Pt/Au Ohmic contact on p-GaN/AlGaN/GaN with a very low specific contact resistivity of 1.98 × 10−5 Ω cm2 is investigated. Secondary ion mass spectroscopy measurement results show that the Mg concentration near the p-GaN surface increases form 8 × 1019 to 7 × 1020/cm3 for Mg/Pt/Au contact after annealing. It indicates that Mg atoms from the Mg/Pt/Au metal stack diffuse into the p-GaN during annealing, forming a heavily Mg doped p++-GaN layer with a depth of about 3 nm. The sheet resistance Rsh depends on temperature for Mg/Pt/Au contacts on p-GaN/GaN, indicating that the influence of 2DHG on carrier transport mechanisms at the metal/p-GaN interface was eliminated. For Mg/Pt/Au contacts at ≥360 K, specific contact resistivity reasonably follows T−1, which indicates that the band conduction of Schottky theory dominates the carrier transport. For Mg/Pt/Au contacts at 200–360 K, the electrical resistivity reasonably follows T−1/4, indicating variable-range hopping (VRH) conduction through Mg-related deep-level defects (DLD). Based on the VRH conduction model, the effective barrier height (qφ) of the Mg-related DLD band is extracted as 0.265 eV, which well matches the excellent Ohmic contact.

Temperature dependence of the bandgap of Eu doped {ZnCdO/ZnO}30 multilayer structures

In situ Eu-doped {ZnCdO/ZnO}30 multilayer systems were grown on p-type Si-substrates and on quartz substrates by plasma-assisted molecular beam epitaxy. Various Eu concentrations in the samples were achieved by controlling temperature of the europium effusion cell. The properties of as-grown and annealed {ZnCdO/ZnO}30:Eu multilayers were investigated using secondary ion mass spectrometry (SIMS) and X-ray diffraction methods. SIMS measurements showed that annealing at 700 °C and 900 °C practically did not change the Eu concentration and the rare earth depth profiles are uniform. It was found that the band gap depends on the concentration of Eu and it was changed by rapid thermal annealing. Varshni and Bose-Einstein equations were used to describe the temperature dependence of the band gap of {ZnCdO/ZnO}30:Eu multilayer structures and Debye and Einstein temperatures were obtained.

Degradation mechanism of surface sulfidization and hydrophobicity by Fe(III) in the flotation of cerussite

Unavoidable metal ions commonly exist in the pulp during flotation. These ions can affect the floatability of minerals, and they can also result in the differences in the surface features between different minerals. In this study, how Fe3+ affected the flotation behavior of cerussite was investigated by micro-flotation tests. The corresponding adsorption characteristics of the sulfidizing agent and collector on the surfaces of cerussite were investigated by surface-analysis techniques. The results of micro-flotation tests showed that the floatability of cerussite significantly decreased when Fe3+ was added before Na2S and xanthate. The flotation recovery of cerussite decreased compared with that obtained without participation of Fe3+. Additionally, the results of xanthate and Na2S adsorption tests, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and zeta potential measurements verified that Fe3+ and its hydrophilic hydroxyl derivatives (Fe-OH compounds) resulted in reduced amounts and reactive activities of S-bearing species adsorbed on the surfaces of cerussite. This decreased the adsorption capacity of subsequently added xanthate, resulting in the difficulty in effectively recovering cerussite in the sulfidization-xanthate system.

Controllable nitrogen doping of MOCVD Ga2O3 using NH3

We report on the controllable nitrogen doping of β-Ga2O3 as a deep acceptor dopant using ammonia diluted in nitrogen (NH3/N2) as a source of active nitrogen in the metal organic chemical vapor deposition epitaxy. The effects of the NH3/N2 flow rate and substrate temperature on the incorporation efficiency, reproducibility, and controllability of N doping into Ga2O3 were studied using secondary ion mass spectrometry measurements. With the increase in the NH3/N2 molar flow rate from ∼2 × 10−8 to ∼2 × 10−6 mol/min, the N impurities incorporated into the β-Ga2O3 increased linearly from ∼1 × 1018 to ∼2 × 1020 cm−3. At low substrate temperatures (<800 °C), hydrogen was incorporated into the film accompanying nitrogen with comparable concentrations. Despite this, the current–voltage measurements showed that the N and H co-doped films were resistive with a measured resistance of >70 MΩ for a film grown with [N] ≈ [H] of ∼8 × 1018 cm−3. X-ray on-axis (020) and off-axis (111) rocking curve ω-scans and atomic force microscopy measurements show no influence of NH3/N2 dopant on the structural and surface quality of the films. However, the presence of H promoted the growth of (110) and (1¯10) facets elongated along the [001] direction. At high growth temperatures (≥950 °C), the H concentration in the films was reduced by nearly ∼10×, but with a slight increase in the concentration of N. The results show that controllable and repeatable nitrogen doping into β-Ga2O3 can be achieved using ammonia to obtain deep acceptor doping or compensation needed for device engineering in β-Ga2O3-based power electronic devices.

Electrical characterization of thin silicon-on-insulator films doped by means of phosphorus end-terminated polymers

Ex-situ doping of 30 nm thick silicon-on-insulator (SOI) substrates is performed by using polymers terminated with a doping containing moiety. Poly(methylmetachrylate) polymers with a P containing moiety are used to create a phosphorus δ-layer at the interface between the Si device layer and a 10 nm thick SiO2 capping layer deposited on the SOI sample by conventional e-beam evaporation. Drive-in of the P atoms is performed by annealing the samples in a rapid thermal processing (RTP) system at temperatures (TA) ranging from 900 to 1200 °C in N2 atmosphere. Annealing time is properly selected to inject a constant P dose of ∼ 1 × 1013 cm−2 into the SOI substrate, achieving a uniform dopant concentration throughout the entire Si device layer as verified by Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) measurements. Sample resistivity (ρ), carrier concentration (ne) and mobility (μ) are determined combining sheet resistance and Hall measurements in the van der Pauw configuration. An average activation rate above 95% is observed at room temperature in the samples annealed at 1000 °C for 100 s, suggesting complete activation of the injected dopants. The detection of phosphorus signal by EPR analysis confirms the extremely high effective concentration of dopants. Low temperature (5–300 K) electrical characterization of a 30 nm thick SOI sample (ne ∼ 2.7 × 1018 cm−3 at 300 K) indicates that the evolution of ρ, ne and μ values as a function of temperature are perfectly consistent, within the experimental error, with those reported for a P doped bulk Si.

Impact of B2H6 plasma treatment on contact resistivity in silicon heterojunction solar cells

We investigated the effect of the B2H6 plasma treatment on p-type hydrogenated amorphous silicon (p-a-Si:H) surfaces for high-performance silicon heterojunction (SHJ) solar cells. Secondary ion mass spectroscopy measurements revealed that the boron concentration at the p-a-Si:H surface is increased by employing the B2H6 plasma treatment. Furthermore, specific contact resistance is decreased by about one-third after the B2H6 plasma treatment. No degradation of passivation performance is induced by the B2H6 plasma treatment. The power conversion efficiency of the SHJ solar cells with the B2H6 plasma treatment is improved by the increase in fill factor (FF) due to decreased series resistance and increased shunt resistance. From numerical simulations, the upward band bending is enhanced at the heterointerface between transparent conductive oxide (TCO) and p-a-Si:H by the B2H6 plasma treatment, which is responsible for the improved FF owing to facilitated tunneling holes from c-Si to p-a-Si:H layers and the TCO/p-a-Si:H heterointerface.

Nitrogen vacancies in GaN templates and their critical role on the luminescence efficiency of blue quantum wells.

In InGaN-based LEDs, an InGaN layer underlying active region has been widely used to improve the luminescence efficiency of the quantum wells (QWs). It has been reported recently that the role of InGaN underlayer (UL) is to block the diffusion of point defects or surface defects in n-GaN into QWs. The type and the source of the point defects need further investigations. In this paper, using temperature-dependent photoluminescence (PL) measurements, we observe emission peak related to nitrogen vacancies (VN) in n-GaN. In combination with secondary ion mass spectroscopy (SIMS) measurement and theoretical calculation, it is found that VN concentration in n-GaN is as high as about 3 × 1018 cm-3 in n-GaN grown with low growth V/III ratio and can be suppressed to about 1.5 × 1016 cm-3 by increasing growth V/III ratio. Luminescence efficiency of QWs grown on n-GaN under high V/III ratio is greatly improved. These results indicate high density of nitrogen vacancies are formed in n-GaN layer grown under low V/III ratio and diffuse into quantum wells during epitaxial growth and reduce the luminescence efficiency of the QWs.

Phosphorus diffusion and deactivation during SiGe oxidation

Dopant profiles near the semiconductor–oxide interface are critical for microelectronic device performance. As the incorporation of Si1−xGex into transistors continues to increase, it is necessary to understand the behavior of dopants in Si1−xGex. In this paper, the diffusion and electrical activation of phosphorus within a strained, single-crystal Si0.7Ge0.3 layer on Si during oxidation are reported. Both layers were uniformly doped, in situ, with an average phosphorus concentration of 4 × 1019 atoms/cm3. After high-temperature oxidation, secondary ion mass spectrometry measurements revealed that the bulk of the phosphorus diffuses out of only the SiGe layer and segregates at the oxidizing SiGe–SiO2 interface. Hall effect measurements corroborate the observed phosphorus loss and show that the phosphorus diffusing to the oxidizing interface is electrically inactive. Through density functional theory (DFT) calculations, it is shown that phosphorus interstitials prefer sites near the SiGe–SiO2 interface. Finally, based on a combination of experimental data and DFT calculations, we propose that the phosphorus atoms are displaced from their lattice sites by Ge interstitials that are generated during SiGe oxidation. The phosphorus atoms then migrate toward the SiGe–SiO2 interface through a novel mechanism of hopping between Ge sites as P–Ge split interstitials. Once they reach the interface, they are electrically inactive, potentially in the form of interstitial clusters or as part of the reconstructed interface or oxide.