Dynamic Secondary Ion Mass Spectrometry Research Articles

Challenges in quantifying Pt concentrations in Pd alloys by using secondary ion mass spectrometry: Strong grain orientation effects

Palladium–platinum alloys were analysed by dynamic secondary ion mass spectrometry (SIMS) to investigate grain orientation effects that gave differences of up to 400% in the Pt/Pd count rate ratios, even within the same grain upon small rotations of a Pd sample with 1 wt% Pt. The sample had been homogenized by annealing, and the homogeneity was confirmed by X‐ray analysis in scanning electron microscopy (SEM). Grain orientations were determined by electron backscatter diffraction (EBSD). Crater depths were measured by white light interferometry (WLI). SEM images from the bottom of SIMS craters made in the same grain after small rotations around the sample surface normally showed different patterns of microfaceting for some rotation angles, probably exposing low‐index crystallographic planes. A complete understanding of the observed grain orientation effect is still lacking. However, factors such as ion mass, sputter rate, ion channelling, ion focusing, preferential sputtering, surface height, crater microfaceting and/or angle‐dependent sputtering seem to play a role. For these Pd–Pt alloys, the strong grain orientation effect adds another level of complexity when attempting to quantify concentrations and obtain depth profiles by SIMS. Without proper sampling and/or averaging, one could reach very wrong conclusions when comparing results from different samples.

Secondary Ion Mass Spectral Imaging of Metals and Alloys.

Secondary Ion Mass Spectrometry (SIMS) is an outstanding technique for Mass Spectral Imaging (MSI) due to its notable advantages, including high sensitivity, selectivity, and high dynamic range. As a result, SIMS has been employed across many domains of science. In this review, we provide an in-depth overview of the fundamental principles underlying SIMS, followed by an account of the recent development of SIMS instruments. The review encompasses various applications of specific SIMS instruments, notably static SIMS with time-of-flight SIMS (ToF-SIMS) as a widely used platform and dynamic SIMS with Nano SIMS and large geometry SIMS as successful instruments. We particularly focus on SIMS utility in microanalysis and imaging of metals and alloys as materials of interest. Additionally, we discuss the challenges in big SIMS data analysis and give examples of machine leaning (ML) and Artificial Intelligence (AI) for effective MSI data analysis. Finally, we recommend the outlook of SIMS development. It is anticipated that in situ and operando SIMS has the potential to significantly enhance the investigation of metals and alloys by enabling real-time examinations of material surfaces and interfaces during dynamic transformations.

Excellent crystalline silicon surface passivation by transparent conductive Al-doped ZnO/ITO stack

The surface passivation materials commonly used in crystalline silicon (c-Si) solar cells are either electrically insulating or opaque to the solar spectrum, which poses the electrical loss or optical loss. Hence it is of great significance to explore functional films that are simultaneously transparent, conductive and passivating for c-Si. In this study, we successfully tune two most well-known transparent conductive oxides, i.e. Al-doped ZnO (AZO) and indium tin oxide (ITO), as excellent passivation layers for c-Si surface. The AZO film is grown by atomic layer deposition and is capped with a magnetron-sputtered ITO film. Dynamic secondary ion mass spectrometry reveals that such stack design can retain higher hydrogen concentration on c-Si surface than a single AZO film during annealing. In addition, the AZO should be highly doped to reduce the energy barrier height around c-Si surface, thereby increasing the charge carrier asymmetry and thus reducing surface recombination. It is also highly crucial to optimize the annealing temperature and interfacial silicon oxide. As such, the effective minority carrier lifetime reaches 2.0 ms and the implied open-circuit voltage approaches 700 mV. Besides, the AZO/ITO stacked films possess negligible optical absorption, low sheet resistance (∼90 Ω/sq), and outstanding antireflection effect on c-Si surface.

Permeation of oxygen and water into a plasma-enhanced chemical vapor deposited silicon nitride film as function of deposition pressure

In this work, we demonstrate that the permeability of a SiNx thin film (prepared by plasma-enhanced chemical vapor deposition) to water and oxygen is closely related to the deposition pressure. By dynamic secondary ion mass spectrometry, we confirmed that water penetration occurs into the SiNx film only in the oxidized layer. Furthermore, positron annihilation lifetime spectroscopy indicated that a SiNx film with a lower deposition pressure provides a smaller pore (free volume hole) radius, which is more effective in terms of blocking ambient molecular diffusion or penetration. The SiNx films were also applied as an encapsulation layer for organic light-emitting diodes; SiNx films with a lower deposition pressure exhibited higher encapsulation properties.

Performance Enhancement in Powder-Fabricated Cu2(ZnSn)Se4 Solar Cell by Roll Compression.

Despite the improved conversion efficiency of Cu2(ZnSn)Se4 (CZTSe) solar cells, their roll-to-roll fabrication nonetheless leads to low performance. The selenization time and temperature are typically considered major parameters for a powder-based CZTSe film; meanwhile, the importance of the densification during the roll-to-roll process is often overlooked. The densification process is related to the porosity of the light-absorbing layer, where high porosity lowers cell performance. In this study, we fabricated a dense CZTSe absorber layer as a method of controlling the compression of a powder precursor (Cu1.7(Zn1.2Sn1.0)S4.0 (CZTS)) during the roll-press process. The increased particle packing density of the CZTS layer was crucial in sintering the powder layer into a dense film and preventing severe selenization of the Mo back electrode. The pressed absorber layer of the CZTSe solar cell exhibited a more uniform chemical composition determined using dynamic secondary ion mass spectrometry (SIMS). Under the AM 1.5G illumination condition, the power conversion efficiency of the pressed solar cell was 6.82%, while the unpressed one was 4.90%.

Anisotropic Rh3+ Diffusion in Layered Hexaaluminate Mitigates Thermal Deactivation of Supported Rhodium Catalysts

When exposed to a high-temperature oxidizing environment, Rh catalysts supported on Al2O3-based oxides lose their three-way catalytic activity as a result of unfavorable interface interactions that allow Rh3+ to diffuse into the support structure and occupy Al3+ sites. This study showed that the incorporated Rh3+ ions were not easily reduced to active Rh metal species and caused substantial thermal deactivation. The deactivation was most obvious for γ-Al2O3 and MgAl2O4 with a spinel-type structure but much less for hexaaluminate (LaMgAl11O19) with a layered structure consisting of alternative stacking of a spinel block and a La–O monolayer. After annealing at 900 and 1000 °C for 100 h in the air, Rh-deposited single crystals were studied by dynamic secondary ion mass spectrometry to analyze the Rh depth profile. The Rh depth profile in LaMgAl11O19 showed that the diffusion along the c axis (∥c) was significantly suppressed compared to that normal to the c axis (⊥c). The diffusion of Rh3+ was faster and nearly isotropic in a MgAl2O4 single crystal, which was used as a model crystal for γ-Al2O3. These results show that the layered structure of hexaaluminate influences the Rh3+ diffusion, i.e., the La–O interlayer between closely packed spinel blocks running at every approximately 1.1 nm interval is likely the diffusion barrier. This barrier effectively blocks further penetration of the incorporated Rh3+ ions from the surface and preserves their smooth reduction to active metallic Rh nanoparticles.

Film thickness and strain rate dependences of the mechanical properties of polystyrene-b-polyisoprene-b-polystyrene block copolymer ultrathin films forming a spherical domain

While the mechanical properties of ultrathin polymer films have been extensively studied, only few studies have focused on the ultrathin block copolymer films with complex topologies. The structure-property relationship of ultrathin films (thickness = 35–1000 nm) of polystyrene- b -polyisoprene- b -polystyrene (SIS) containing 14 wt% polystyrene (PS) is established in this study. Grazing-incidence small-angle X-ray scattering, dynamic secondary ion mass spectrometry, and atomic force microscopy were used to characterize the film structure. The difference in surface energy and interfacial energy of the domains resulted in the SIS thin films to primarily consist of three layers: a PS-rich subsurface layer (30 wt%), a spherical PS bulk layer (14 wt%), and a PS-rich interface layer (20 wt%). The film-on-water tensile test was used to investigate both the film thickness and strain rate dependences of mechanical properties. We found that the Young's modulus increased dramatically as film thickness decreased, although only few PS-rich layers consisting of disperse cylindrical and spherical PS domains existed at the surface and interface. Furthermore, the strain rate dependence of the modulus and stress relaxation was more significant for thinner films than for thicker films. The increase in modulus and unusual relaxation behavior are hypothesized to be the result of a combination of different factors, including PS domain alignment, confinement effects, and surface and interface interactions. • The structure-property relationship of ultrathin SIS films is analyzed. • Young's modulus increases upon decreasing thickness. • The extent of stress relaxation is larger for thinner films. • The stiffening may result from PS domain alignment.

Recombination between 13C and 2H to Form Acetylide (13C22H-) Probes Nanoscale Interactions in Lipid Bilayers via Dynamic Secondary Ion Mass Spectrometry: Cholesterol and GM1 Clustering.

Although it is thought that there is lateral heterogeneity of lipid and protein components within biological membranes, probing this heterogeneity has proven challenging. The difficulty in such experiments is due to both the small length scale over which such heterogeneity can occur, and the significant perturbation resulting from fluorescent or spin labeling on the delicate interactions within bilayers. Atomic recombination during dynamic nanoscale secondary ion imaging mass spectrometry (NanoSIMS) is a non-perturbative method for examining nanoscale bilayer interactions. Atomic recombination is a variation on conventional NanoSIMS imaging, whereby an isotope on one molecule combines with a different isotope on another molecule during the ionization process, forming an isotopically enriched polyatomic ion in a distance-dependent manner. We show that the recombinant ion, 13C22H-, is formed in high yield from 13C- and 2H-labeled lipids. The low natural abundance of triply labeled acetylide also makes it an ideal ion to probe GM1 clusters in model membranes and the effects of cholesterol on lipid-lipid interactions. We find evidence supporting the cholesterol condensation effect as well as the presence of nanoscale GM1 clusters in model membranes.

Selectively buried growth of heavily B doped diamond layers with step-free surfaces in N doped diamond (1 1 1) by homoepitaxial lateral growth

In this work, we proposed a novel method to form a buried heavily boron (B) doped p+-structure with a step-free diamond surface in nitrogen doped diamond (111) based on homoepitaxial lateral growth technique. The buried structure with a size of 10 µm × 10 µm × 0.085 µm was fabricated by inductively coupled plasma (ICP) etching of the mesa structure and subsequent heavy B-doping, with a boron to carbon (B/C) ratio of 15,000 ppm in the microwave-plasma-assisted chemical vapor deposition (MPCVD). The surface morphology of the buried area and its surrounding were observed by laser microscopy (LM) and atomic force microscopy (AFM), which showed atomically flat surfaces before and even after B doping. Surface potential difference measurements on both areas were applied using Kelvin-probe force microscopy (KFM). The intensity imaging of B concentration in and around the buried areas were measured by dynamic secondary ion mass spectrometry (SIMS), which confirmed the heavy B doping of the buried structure and the depth profile shows that B doping is uniform, with a concentration of 2 × 1020 atoms/cm3.

Surface Analysis by Secondary Ion Mass Spectrometry (SIMS): Principles and Applications from Swiss laboratories

Secondary Ion Mass Spectrometry (SIMS) extracts chemical, elemental, or isotopic information about a localized area of a solid target by performing mass spectrometry on secondary ions sputtered from its surface by the impact of a beam of charged particles. This primary beam sputters ionized atoms and small molecules (as well as many neutral particles) from the upper few nanometers of the sample surface. The physical basis of SIMS has been applied to a large range of applications utilizing instruments optimized with different types of mass analyzer, either dynamic SIMS with a double focusing mass spectrometer or static SIMS with a Time of Flight (TOF) analyzer. Here, we present a short review of the principles and major applications of three different SIMS instruments located in Switzerland.

Laser-induced activation of Mg-doped GaN: quantitative characterization and analysis

We investigate the effectiveness of laser-induced treatment as compared to rapid-thermal annealing (RTA) for the activation of p-type dopant in Mg-doped GaN layers. The study is based on a wide set of analytical techniques, including resistivity measurements, atomic force microscopy (AFM), scanning emission microscopy, dynamic secondary ion mass spectroscopy (SIMS), time-of-flight (TOF) SIMS and energy dispersive x-ray (EDX) spectroscopy in combination with scanning transmission electron microscopy (STEM). Samples are treated at different energy densities and in different atmospheres, to provide a comprehensive overview of the topic. The analysis is carried out on GaN-on-Si samples, to demonstrate the effectiveness of the treatment even in presence of high threading dislocation densities. The original results presented in this paper indicate that: (a) laser treatment is an effective process for activating the p-type dopant in Mg-doped GaN layers; even at low irradiation energy densities (400 mJ cm−2) the laser treatment can effectively activate the Mg doping, with the best resistivity results obtained (around 1.5 Ωcm) comparable with those obtained by optimized RTA; (b) resistivity varies with temperature with activation energy E a = 0.14 eV, which is compatible with the MgGa acceptor in GaN; (c) TOF-SIMS, AFM, EDX-STEM analysis indicates that the laser treatment does not modify the concentration profile of magnesium and surface roughness for low and moderate laser energy densities; changes are detected only for energy densities above 600 mJ cm−2, for which a significant degradation of the surface is revealed. The experimental evidence collected within this paper provide an accurate assessment of the process conditions for effective laser activation of Mg-doped GaN, thus allowing the fine-tuning required for selective activation and for industrial applications.

Ultrathin and Efficient Organic Photovoltaics with Enhanced Air Stability by Suppression of Zinc Element Diffusion.

Ultrathin (thickness less than 10 µm) organic photovoltaics (OPVs) can be applied to power soft robotics and wearable electronics. In addition to high power conversion efficiency, stability under various environmental stresses is crucial for the application of ultrathin OPVs. In this study, the authors realize highly air‐stable and ultrathin (≈3 µm) OPVs that possess high efficiency (15.8%) and an outstanding power‐per‐weight ratio of 33.8 W g−1. Dynamic secondary‐ion mass spectrometry is used to identify Zn diffusion from the electron transport layer zinc oxide (ZnO) to the interface of photoactive layer; this diffusion results in the degradation of the ultrathin OPVs in air. The suppression of the Zn diffusion by a chelating strategy results in stable ultrathin OPVs that maintain 89.6% of their initial efficiency after storage for 1574 h in air at room temperature under dark conditions and 92.4% of their initial efficiency after annealing for 172 h at 85 °C in air under dark conditions. The lightweight and stable OPVs also possess excellent deformability with 87.3% retention of the initial performance after 5000 cycles of a compressing–stretching test with 33% compression.

Characterization of gold deportment and thiosulfate extraction for a copper‑gold concentrate treated by pressure oxidation

Gold extraction from porphyry copper‑gold ore is challenging due to the presence of copper and sulfide minerals. In this study, pressure oxidation (POX) was used for copper extraction and gold liberation from the sulfide mineral matrix. The POX residue was investigated for gold mineralization and leaching study. Gold deportment study was conducted using a series of techniques, including X-ray diffraction (XRD), optical microscope, scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX), and dynamic secondary ion mass spectrometry (D-SIMS). Cyanidation was compared as a baseline for gold extraction; ammoniacal thiosulfate ((NH4)2S2O3) and non-ammoniacal thiosulfate (Na2S2O3) were investigated as alternative leaching conditions.In this work, POX achieved a high copper removal percentage and left 0.66% copper in the residue. Undestroyed sulfide minerals such as chalcopyrite, pyrite, and molybdenite presented with 2.7%. Hematite formed during POX and accounted for 66% of the total mineral phases. Meanwhile, hematite was the major sub-microscopic gold carrier, containing 64.7% of the total gold as colloidal gold. Visible gold was identified as 24.4%. Gold extraction tests revealed that the maximum gold extraction achieved by cyanidation was 85% using 250 mg/L NaCN, consistent with the gold deportment study. Similar gold recovery was observed using 0.03 M (NH4)2S2O3, but it reduced drastically in Na2S2O3 leaching solution due to the absence of ammonia.

Sputtering of Oxides from LaNi5 Surface

The changes in chemical composition of the intermetallic alloy LaNi5 surface monolayers were studied using secondary ion mass spectrometry (SIMS) in the process of the alloy interaction with oxygen. The investigated samples were pellets made by pressing the fine-grained LaNi5 alloy. Ar+ ions having energies of 10-18 keV were used as primary ions. The primary beam current density was 9-17 μA·cm-2, which corresponds to the dynamic SIMS mode. The emission intensities of secondary ions were measured within the dynamic range of at least 6 orders of magnitude. Before the measurements, the samples were annealed in residual vacuum at a temperature of ~ 1000 K. After the annealing, the sample surface was cleaned using the primary ion beam until the mass-spectrum composition and secondary ion emission intensity stabilized completely. The gas phase composition was monitored using a gas mass spectrometer. The conducted studies showed that a complex chemical structure including oxygen, lanthanum, and nickel is formed on the surface and in the near-surface region of LaNi5 as a result of its exposure to oxygen. Oxygen forms strong chemical bonds in such a structure with both components of the alloy. This is evidenced by the presence of a large set of oxygen containing emissions of positive and negative secondary ions with lanthanum, with nickel, and oxygen containing lanthanum-nickel cluster secondary ions in mass spectra. The resulting oxide compounds have a bulk structure and occupy dozens of monolayers. In such a bulk oxide structure, the outer monolayers are characterized by the highest ratio of oxygen atom number to the number of matrix atoms. This ratio decreases along the transition from the surface to the underlying monolayers. This process occurs uniformly, without any phase transformation. The observed secondary ions are not a product of association between sputtered surface fragments and oxygen in the gas phase at the fly-off stage after sputter-ejection, but they are products of the oxide compounds being sputtered, hence they characterize the composition of surface and near-surface region.

Nanometer-Thick SiN Films as Gas Barrier Coatings Densified by Vacuum UV Irradiation

Gas barrier films are widely used in electronic and packaging applications. They are also critical components of flexible organic light-emitting diodes (FOLEDs) that require high gas barrier performance. Among the various film manufacturing techniques, solution-processed thin-film encapsulation (TFE) represents a low-cost FOLED fabrication method. The nanometer-thick SiN films produced following the vacuum ultraviolet (VUV)-induced densification of solution-processed perhydropolysilazane (PHPS) films in a N2 atmosphere can potentially serve as TFE barrier films. However, the nanometer-thick PHPS densification process has not been examined in sufficient detail. We investigated and discussed the effects of the Si–N bond number, PHPS film composition, and free volume (present in the produced Si–N network) on the VUV-induced PHPS densification process. It was found that VUV irradiation caused rapid hydrogen release and film densification through the formation of Si–N bonds. The results obtained using the X-ray photoelectron spectroscopy and dynamic secondary ion mass spectrometry techniques, and the calculated residual hydrogen ratios, revealed that the film composition was strongly related to the number of residual hydrogen atoms and Si–N bonds. Notably, nanometer-thick PHPS film densification was a relatively slow process, in which the free volume in the Si–N network was considerably reduced by the atomic rearrangement induced by the simultaneous cleavage of several Si–N bonds during VUV irradiation. We believe that the results presented herein can potentially serve as a guideline for developing solution-processed nanometer-thick SiN films with relatively high density and excellent gas barrier performance (that is comparable to that exhibited by vacuum-processed barrier films).

Mechanical Properties of Ultrathin Polystyrene-b-Polybutadiene-b-Polystyrene Block Copolymer Films: Film Thickness-Dependent Young’s Modulus

This study investigated the mechanical properties of ultrathin polystyrene-b-polybutadiene-b-polystyrene (SBS) block copolymer films with thicknesses ranging from 20 to 600 nm using a pseudo-free-standing tensile test carried out using an ultrathin film floating on water. The Young’s moduli of ultrathin SBS films increased drastically with decreasing thickness for films thinner than 100 nm, i.e., 2 or 3 times the domain spacing of the SBS. We analyzed the depth profiles of the polystyrene (PS) domain in the SBS thin films by dynamic secondary ion mass spectrometry and the surface and interface in-plane morphology using atomic force microscopy. The PS-rich continuous subsurface layer was observed to be a major factor for the drastic increase in Young’s modulus under ultrathin film conditions. Therefore, we propose a simple two-layer model consisting of a hard PS-rich layer and a soft bulk layer to explain the specific increase in Young’s modulus with decreasing film thickness.

High temperature reaction of multiple eutectic-component system: The case of solid metallic Zr and molten stainless steel-B4C

The eutectic melting, one of the fundamental phenomena in high temperature reactions involving liquid phases, is a primitive but important subject for both scientific and industrial fields associated with metallurgy. The present study aims at revealing the formation and reaction mechanisms of the multiple eutectic-component system consisting of solid metallic Zr and molten stainless steel-boron carbide (SS-B4C) by combining multiple analytical methods (i.e. powder X-ray diffraction (PXRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), and dynamic secondary ion mass spectrometry (D-SIMS)) with thermodynamical consideration. The results indicate that the solidified Zr-SS-B4C mixture is composed of major phases of (Fe,Cr)2Zr, (Fe,Cr,Ni)2Zr, (Ni,Fe)Zr2, ZrB2, and a minor phase of ZrC. The results also reveal that the eutectic melting between solid metallic Zr and molten SS-B4C can be described as the combination of diffusion kinetics and thermodynamic stability. That is, the initial formation of ZrC and ZrB2 layers at the reaction interface significantly retards the diffusion of other SS-B4C components (i.e. Cr, Fe, and Ni) into solid metallic Zr.

Insights into secondary ion formation during dynamic SIMS analysis: Evidence from sputtering of laboratory synthesized uranium compounds with a high-energy O− primary beam on a NanoSIMS 50L

We investigate the sputtering and ionization process that takes place during secondary ion mass spectrometry (SIMS) analysis in order to develop a better understanding of the underlying controls on elemental and molecular oxide secondary ion yields. Using data from a suite of uranium compounds that were sputtered with an O- primary beam on a NanoSIMS 50L, our goal is to understand whether a compound’s intrinsic properties, or processes operating at the sputtering site, exert the greatest influence over the relative abundances of uranium elemental and molecular oxide secondary ions observed during an analysis. While the observed 238U/238U16O and 238U/238U16O2 of the various compounds exhibit considerable overlap, there are relationships between the weighted mean 238U/238U16O and 238U/238U16O2 ratios for the various compounds and their enthalpies of formation. This reinforces the existing theory that the nature of the material being sputtered can influence relative ion yields (e.g. the SIMS matrix effect), but we also document significant evidence for the influence of processes operating at the sputtering site as a major factor. The existence of a strong relationship between the relative uranium molecular oxide production rate and the mass fractionation regimes taking place within an analysis, as well as the existence of sudden shifts in molecular oxide production rates taking place within an analysis, provide further evidence for the importance of processes related to the sputtering and ionization dynamics as exerting the most control over observed ion yields. Evaluation of our data within the context of existing models for secondary ion production during SIMS analysis highlights the need for additional models that consider the competing influences of a sample’s chemical and/or structural form, reactions taking place at the sputtering site, as well as the ionization and ion extraction dynamics of the various elemental and molecular oxide species.

Combining secondary ion mass spectrometry image depth profiling and single particle inductively coupled plasma mass spectrometry to investigate the uptake and biodistribution of gold nanoparticles in Caenorhabditis elegans

Analytical techniques capable of determining the spatial distribution and quantity (mass and/or particle number) of engineered nanomaterials in organisms are essential for characterizing nano-bio interactions and for nanomaterial risk assessments. Here, we combine the use of dynamic secondary ion mass spectrometry (dynamic SIMS) and single particle inductively coupled mass spectrometry (spICP-MS) techniques to determine the biodistribution and quantity of gold nanoparticles (AuNPs) ingested by Caenorhabditis elegans. We report the application of SIMS in image depth profiling mode for visualizing, identifying, and characterizing the biodistribution of AuNPs ingested by nematodes in both the lateral and z (depth) dimensions. In parallel, conventional- and sp-ICP-MS quantified the mean number of AuNPs within the nematode, ranging from 2 to 36 NPs depending on the size of AuNP. The complementary data from both SIMS image depth profiling and spICP-MS provides a complete view of the uptake, translocation, and size distribution of ingested NPs within Caenorhabditis elegans.

Effects of Oxygen Partial Pressure on the Properties of SnOx Thin Films Doped with Indium

This study examined the effects of the oxygen partial pressure on the properties of heavily indium-doped tin-oxide (In-SnOx) thin films grown at room temperature by reactive direct-current pulse sputtering from a mixed metallic target containing Sn (70 atomic %)-In (30 atomic %). X-ray photoelectron spectroscopy (XPS), dynamic secondary-ion mass spectrometry, X-ray diffraction (XRD), and Hall Effect measurements showed that the In-SnOx samples prepared with oxygen pressures of 10–20% had metallic properties. This was attributed to the notable Sn0 area ranges of 5.6–17.3%, low resistivity ranges of 5.5×10−3–2×10−4 Ωcm, and the high carrier concentration ranges of 3.5×1021–5.1×1022/cm3. On the other hand, the Sn4+ area and the resistivity increased significantly to 73.3% and 9.4 Ωcm. In comparison, the Sn2+ area and the electron concentration decreased dramatically to 23.6% and 6.5×1016/cm3, respectively, with increasing oxygen partial pressure up to 30%. The samples prepared with oxygen pressures higher than 20% exhibited nonmetallic properties with the dominant n-type SnO2 phase. This steep increase in the Sn4+ area was attributed to an increase in the oxygen contents in the samples, resulting in a decrease in the number of oxygen vacancy donors in the samples prepared with oxygen pressures higher than 20%. The decrease in the Sn2+ area was related to a decrease in the indium (In) contents in the samples, which also decreased the number of metal acceptors in the samples. XRD also showed that the metallic indium stannide (In0.2Sn0.8) and In–Sn–O(ITO) peaks coexisted for samples prepared with an oxygen pressure of 0–10%. In contrast, the samples prepared with oxygen pressures higher than 20% had an amorphous structure with SnO2 and SnO phases, supporting the XPS and Hall Effect measurement results.