Si 2p Research Articles

Epitaxial SiGeSn grown on Si by ion implantation

We have formed SixGe1−x−ySny compounds on Si substrates by ion implantation and annealing and investigated their concentration profiles, crystallization, and optical properties. Ge and Sn ions were implanted in the range (2.5–10) × 1016 Ge/cm2 at 65 keV, and (1.0–4.0) × 1016 Sn/cm2 at 100 keV, resulting in a peak implant dose at a depth of 50 nm for both species. Epitaxially regrown SixGe1−x−ySny layers (110 nm thick) were produced with Ge and Sn contents that allowed bandgap tuning in the (0.88–1.1) eV range. Shifts in photoelectron binding energies (Si 2p, Ge 3d, and Sn 3d) were consistent with ternary compound formation. Sn segregation was observed for annealing temperatures ≥600 °C. A significant increase in the optical absorption coefficient (×104 cm−1 for λ = (800–1700) nm) was observed for SiGe, SiSn, and SiGeSn alloys, with SiGeSn having coefficients several orders of magnitude higher than for Si. Contributions of segregated Sn to these properties were observed. Metastable SixGe1−x−ySny layers were achieved, which may point to a promising route to mitigate Sn incorporation challenges for near-infrared detectors.

Interface analysis of oxide free MoS2 films fabricated by solution process.

We report a solution-based approach for the synthesis of oxidation-free MoS2 films, focusing on interface analysis. Through a sulfurization-free solution process and single-step annealing, the oxidation-free MoS2 film is successfully prepared on Si3N4 surfaces, showing improved uniformity with a surface roughness below 0.5nm and a thickness of 4nm at a precursor solution concentration of 30 mM, annealed between 700 and 800ºC. The MoS2 films exhibit a hexagonal lattice structure with crystallographic orientations of (1 1 0 0) and (1 2 1 0) with lattice spacings of 0.27nm and 0.16nm respectively. Interfacial analysis by X-ray photoelectron spectroscopy (XPS) on SiO2 reveals migration of oxygen species as evidenced by a shift in the Si 2p spectrum at binding energies between 102.6eV and 102.8eV. MoS2 films on Si3N4 show a complex Si 2p peak evolution at binding energies between 100.9 and 101.8eV, providing valuable insights into the synthesis of oxide-free MoS2 films for potential applications in advanced electronic devices.

Substitution of blast furnace slag by melting furnace slag as active component in green concrete application

Blast furnace slag (BFS), a commonly used substitute for cement clinker, is in large demand and gradually increasing in price. Melting furnace slag (MFS), a by-product of the co-disposal of waste incineration fly ash and metallurgical dust sludge, has potential hydration properties, and its large accumulation also poses a serious threat to the environment. In this study, we focus on the effect of MFS replacing BFS on concrete properties and its hydration mechanism. Results showed that MFS significantly enhanced the compressive strength at the later stage of hydration, and the 28-d compressive strength of MSD concrete was 15.15 % higher than BSD concrete. MFS enriched with a large amount of amorphous silica and alumina played a key role in the hydration process. This is mainly shown as the increase in the fluctuation of Si-O and Al-O bond strengths and the decrease in the energy separation between Ca 2p and Si 2p levels. In addition, the increased substitution of aluminum for silicon in MSD results in the formation of C-A-S-H gels, which are tightly bonded with ettringite to form a composite structure. Subsequent durability assessments indicate that the incorporation of MFS diminishes the permeability to chlorides and sulfates, while also bolstering the concrete’s resistance to carbonation. These findings imply a positive impact on the concrete’s enduring service life.

XPS study of the nitridation of hafnia on silicon

We report a comprehensive quantitative ARXPS study of 20-cycle ALD-grown HfO2 films on Si (001) substrates with and without remote plasma nitridation. The films comprised a 0.6 nm HfO2 layer atop a 1 nm hafnium-rich silicate interlayer. A detailed analysis of the Hf 4f, Si 2p, O 1s, C 1s, and N 1s core level spectra is presented for samples with and without nitridation. The fitting of the Hf 4f spectra reveals four contributing components associated with silicate, hafnia, and their respective nitrided species. The Hf 4f, O 1s, and C 1s spectra exhibit a negative binding energy shift of about 0.2 eV upon nitridation induced by a Si2+-N dipole formed at the interface. Quantitative ARXPS analysis, employing the MultiLayer Model, enabled the determination of the thicknesses, and composition together with their associated uncertainties. The analysis showed that the composition of the nitrided hafnia is HfO1.66N0.33. There is a higher degree of nitridation in the silicate interlayer compared to the overlying hafnia layer. The degree of nitridation is found to increase with plasma power; N2+ is identified as the primary plasma species responsible for the nitridation of hafnia.

Peculiarities in XPS spectra of Sn/SiO2 layers as an effect of surface charge

X-ray photoelectron spectroscopy based on synchrotron radiation was used to investigate the composition of the observed SnO2-x/Sn:SiO2-x thin layer grown by organometallic chemical vapour deposition on single-crystalline silicon wafer with additional argon ions etching treatment. Due to the formation of a thermodynamic anomaly during in situ layer growth, an efficient oxygen exchange between silicon and tin oxide phases occurs. The present study addresses the effect of localized surface charging and its influence on the obtained XPS core level spectra. We found that due to the high electrical conductivity of metallic tin and the direct coupling of tin particles to the silicon wafer, the XPS Sn 3d5/2 core level spectrum is not affected by the surface charge compared to the highly charged dielectric silicon oxide matrix, as observed for the XPS O 1 s and Si 2p core level spectra. Our results show that the core level spectra of Si 2p and O 1 s are shifted up to 3 eV due to the presence of uncompensated positive charge on the surface of the silica matrix. These results provide insight into the influence of surface charge effects on the analysis of conductor/insulator composite materials and contribute to the application of Sn-based materials in various application concepts related to energy and surface functionalization.

Development of MWCNTs@PDMS nanocomposites with enhanced hydrophobicity and thermo-oxidative stability

This paper presents the fabrication of hydrophobic polymer nanomaterials with improved thermal characteristics based on MWCNTs and poly(dimethylsiloxane). The samples were synthesized by physical adsorption of poly(dimethylsiloxane) onto P-MWCNTs surfaces in the amount from 5 to 20 wt%. The effect of different content of adsorbed polymer on the structure and properties of the prepared nanocomposites was studied in detail using ATR-FTIR, SEM, TEM, XRD and RS techniques. XPS results showed that with the increase of adsorbed PDMS onto the MWCNTs surfaces, the Si 2p atomic percentage increased from 1.5 to 5.0 at.%. The investigation of thermal properties using TGA/DSC techniques in air atmosphere revealed that polymer adsorption on the MWCNTs surfaces enhances the thermo-oxidative stability of the nanocomposites to a great extent. The WCA of MWCNTs@PDMS-1000(20) nanocomposite reached 138.9° while this value was 81.8° in the case of the P-MWCNTs. The electrical characterization of the examined samples demonstrated a non-linear current–voltage behaviour and the invariance of the electrical current value with the increasing polymer content in the nanocomposites. The results suggest that the obtained nanocomposites have multi-functional surfaces and are promising for integration into a silicon-based polymer matrix for the development of new materials for electronic devices.

3D cross-linked POSS-containing borate single ion conductor organic-inorganic hybrid gel electrolytes for dendrite-free lithium metal batteries

At present, lithium (Li) metal has become the most promising anode for the next generation of batteries due to its excellent theoretical capacity and low electrochemical potential. Nevertheless, low lithium-ion transference numbers and poor stability between conventional electrolytes and electrodes limit its development. In this work, a novel three-dimensional cross-linked hybrid borate single ion conductor polymer electrolyte (POSS-BSICP) was constructed by coupling of novel synthesized lithium bis-allylmalonate borate (LiBAMB), poly (ethylene glycol) diacrylate (PEGDA) and vinyl-containing caged poly(sesquisiloxane) (MAPOSS) in the presence of pentaerythritol tetrakis(mercaptoacetate) (PETMP) as cross-linker and PVDF-HFP as support materials through UV-thermal Dual-Curing procedures. As expected, the lithium-ion transference number and electrochemical stability of the hybrid electrolyte membranes improve with the incorporation of MAPOSS. The tLi+ is up to 0.82 and the electrochemical window reaches 5.50 V. The Li/Li cell assembled with the POSS-containing single ion conductor gel polymer electrolytes can be subjected to stripping/plating cycles without short circuit over 2700 h at 0.1 mA cm−2, the peak of the SiO bond at 102.3 eV in the Si 2p spectrum confirms that the POSS participate in the formation of SEI, indicating that the incorporation of MAPOSS could increase the compatibility between the electrolytes and electrode. The Li|POSS-BSICP|LiFePO4 cell exhibits excellent cycle performance with a capacity retention over 90 % after 170 cycles and 82.0 % after 290 cycles at 0.1 C.

Quantification of aluminium and silicon‐containing materials using Ag Lα X‐rays

In recent years, instrument manufacturers have been providing laboratory‐based HAXPES (hard X‐ray photoelectron spectroscopy) instruments that have monochromated silver Lα, chromium Kα and gallium Kα X‐ray sources. To be more than a qualitative tool, two things are required: calibration of the signal intensity as a function of kinetic energy (spectrometer response function) and relative sensitivity factors. This is now possible because of routines being available to generate the spectrometer response functions for dual Al Kα/Ag Lα X‐ray sources and the availability of Cant average matrix relative sensitivity factors (AMRSFs). However, to improve accuracy when using the Cant AMRSF care needs to be taken in the definition of the peak areas being used. This is because they need to include the total intrinsic signal that often extends beyond the main peak. This is a particular challenge when quantifying using the Al 1s peak generated with Ag Lα X‐rays as some of the intrinsic signal overlaps with the Al KLL Auger peak. When materials include both aluminium and silicon atoms, the Si 2s and 2p peaks sit upon extended signals coming from the Al 2s and 2s peaks, respectively. Thus, quantification should be limited to using the main peak area, which necessitates different relative sensitivity factors (RSFs). Using polydimethylsiloxane (PDMS) and sapphire (Al2O3) as model systems, experimental RSFs have been determined for use with the main peaks for O 1s, Al 1s, Al2s Al 2p, Si 1s, Si 2s and Si 2p subshells normalized to the RSF of the carbon 1s main peak.

Silicon nanowires analyzed by x-ray photoelectron spectroscopy

Silicon nanowires were characterized by x-ray photoelectron spectroscopy with an Al Kα (1486.6 eV) excitation source. The sample was fixed to a stainless-steel sample holder with a copper double-sided adhesive tape. Survey spectrum and C 1s, O 1s, and Si 2p core-level spectra were acquired.

Evaluation of the chemical states and electrical activation of ultra-highly B-doped Si1-xGex by ion implantation and subsequent nanosecond laser annealing

Given that transistordimensions are approaching atomic scale in metal–oxide–semiconductor field-effect-transistors (MOSFETs), attaining low-contact resistivity (ρc) between contact-metal and Si is a primary challenge for source/drain (S/D) fabrications. To reduce ρc, it is necessary to increase active dopant concentration in the semiconductor region underneath the contact-metal. High-dose ion-implantation and nanosecond laser-annealing (NLA) have been intensively investigated to produce highly activated layers in S/D regions. Particularly for the B-doped SiGe layers, which are used as S/D stressor for p-MOSFETs, non-substitutional B species are generated in the highly doped films at concentrations exceeding ∼ 1021 cm−3. These non-substitutional B are electrically non-activated and thus should be minimized to reduce ρc. In this study, we investigated the chemical states and electrical activation in highly B-doped SiGe layer. Using X-ray photoelectron spectroscopy (XPS), we examined the substitutionality of B-atoms and identified new chemical states of Si-B and Ge-B bonds in Si 2p and Ge 3d peaks. In the B 1s spectra, electrical activation states are determined by quantifying relative area ratios of the active/inactive B peaks, which are well matched with activation rates calculated by Hall measurements. Our findings systematically explained the activation behavior of NLA-treated B-doped SiGe films in high B-concentration ranges.

Crucial Chemical Revelations in 45S5 Bioactive Glass via Sequential Precursor Integration Order.

Among the wet chemical nanoparticle fabrication techniques, the sol-gel process happens through hydrolysis and subsequent polycondensation reactions. The bioactive glass known as the 45S5 SiO2-Na2O-CaO-P2O5 quaternary system has intricate chemistry, yet its advantages benefit the biomedical field on an enormous scale. The order in which the ethanol and TEOS inclusions are exchanged was investigated in this work because it has a direct impact on the early hydrolysis process. Another strategy involves adding phosphate species to the sol before gelation, modifying the network chemistry, and interpreting the findings. Adding phosphate species before gelation in the biomaterial (E-Si-P) resulted in the formation of hydroxyapatite and other calcium silicate phases at 800 °C. Swapping ethanol and TEOS biomaterials (E-Si and Si-E) resulted in the sodium-calcium silicate phase only. Si-E with strong Si-O-Si siloxane rings demonstrated superior mechanical stability, hemocompatibility, and bioactivity. This compact Si-O-Si decreased the surface area of Si-E. XPS spectra revealed that E-Si-P has the lowest Na 1s binding energy (BE) and the highest BE for Si 2p. More Si-O-/Si-OH groups formed by E-Si make the network weak and decrease the surface area and protein adsorption. These differences significantly influenced the morphology, surface properties, mechanical studies, and compatibility test. This study has further unraveled the protocol to design a biomaterial with mechanical stability and load-bearing ability. In addition, the appropriate protocol to yield the desired property-rich biomaterial with preserved bioactivity, mechanical stability, cytocompatibility, as well and surface porosity has been elaborated in detail.

Investigation of structural, temperature and frequency dependent dielectric behavior of Zn2SnO4@amorphous SiO2 core shell nanocomposites

Herein, the detailed investigation of frequency and temperature dependent dielectric behavior of Zn2SnO4@SiO2 core shell nanocomposites (CSNs) is reported. Powder XRD analysis and FTIR spectral analysis were employed to comprehend the structure. The chemical and valence states are analyzed using XPS which confirms the existence of Zn, Sn, and SiO2, each with their distinctive Zn 2p, Sn 3d, and Si 2p valence states. The core shell formation is confirmed from their distinct color contrast in the TEM micrographs. The electrical response was investigated using impedance spectroscopy in the frequency range 1Hz-1 MHz at various temperatures. Positive temperature coefficient of resistance type behavior was established from impedance and modulus formalism. The total conductivity values were well fitted by the universal Jonscher law σtotal = σdc+ Aωn, and the temperature dependence of dc conductivity was discussed.

Cluster Mo2C deposited on graphene nanowalls by x-ray photoelectron spectroscopy

Molybdenum deposited on carbon graphene nanowalls was characterized by x-ray photoelectron spectroscopy with an Al Kα (1486.6 eV) excitation source. The sample was fixed to a stainless-steel sample holder with copper double-sided adhesive tape. Survey spectrum, C 1s, O 1s, Si 2p, and Mo 3d core levels spectra were acquired.

Mechanical and Electrochemical Properties of Highly-Dense Li-Si Alloy Anodes Fabricated by Arc Plasma Deposition

Silicon is one of the most promising anode materials because it has a very high theoretical capacity (4200 mAh g− 1). This capacity is about 10 times higher than that of carbon anode (372 mAh g− 1).[1] However, enormous volumetric change and mechanical stress occur in a silicon anode during electrochemical lithiation-delithiation. Consequently, the specific capacity is degraded during repetition of charge-discharge because of cutting off conductive paths caused by mechanical fracture. It is reported that pre-lithiation by sputtering and electrochemical methods suppresses fracture of silicon anodes by decrease in elastic modulus and yielding stress.[2] However, the reported Li-Si alloy anodes possesses the mechanical properties derived from both the deposited silicon and the voids generated during the synthetic processes. Therefore, a highly-dense alloy is necessary to investigate relationships between mechanical and electrochemical properties of Li-Si itself. We have already fabricated highly-dense amorphous silicon films by an arc plasma deposition (APD) method.[3] Thus, we attempted to fabricate highly-dense Li-Si alloy films by an APD method. The obtained Li-Si alloy films were investigated with focusing on relationships between mechanical properties and electrochemical properties.Li x Si (x = 0-3.56) alloy films were prepared on Al2O3(0001) single-crystal and Cu substrates by an APD method. Metallic lithium and B-doped silicon coated with carbon were used as target materials in the APD apparatus. The physical structures and chemical states of the obtained Li x Si alloy films were investigated with Raman spectroscopy, hard X-ray photoelectron spectroscopy (HAXPES), and neutron reflectometry (NR). Elastic modulus and hardness of the Li x Si alloy films were calculated from load-displacement curves gained by nanoindentation measurement. Constant-current charge-discharge tests were carried out with 2032-type coin cells assembled using the Li x Si films as the working electrodes, Li foils as counter electrodes, and 1 M LiPF6 in EC: DEC 3:7 vol% as electrolytes. The charge-discharge tests were conducted with constant current of 0.01-0.16 mA (1C rate), lower and upper voltages of 20 mV and 1.5 V vs. Li/Li+.In HAXPES spectra, Si 2p peaks derived from Si0 shifted to lower binding energy compared to the Si (x = 0) film as x increased. Therefore, Li x Si alloy films with different compositions were successfully fabricated by the APD method. The peaks because of Si-Si bonds in Raman spectra also shifted to lower wavenumber with the increase in x. The shifts suggest that the length of the Si-Si bonds extended with the increase in x. The NR analyses revealed that Li x Si alloy films possessed the smooth surface with the roughness less than 3 nm. The elastic modulus and hardness of Li x Si alloy films decreased as x increased, meaning that Li x Si alloy films were softer and more easily deformed compared to Si films. In addition, the elastic modulus and hardness of Li x Si alloy films were higher than those of Li x Si films previously reported,[2] suggesting that the APD method more densely made the Li x Si alloy films than the reported sputtering and electrochemical methods. Thus, the objective highly-dense films of Li x Si alloys were successfully obtained. The plateaus corresponding to the reactions of Li x Si ↔︎ Li x ’Si ↔︎ Li y Si (x < x’ < y) were observed in charge-discharge curves of Li x Si alloy films. The first discharge capacities of Li x Si alloy films were lower than the theoretical capacity of silicon. This is due to the existence of lithium in the structure by pre-lithiation. Cycle stabilities of Li x Si alloy films were superior to the Si film. To reveal factors of the cycle stabilizing, the charge-discharge reactions were analyzed with dQ/dV plots. The peaks around 0.5 V in the delithation process decreased about Si film. This decrease in the reaction peak is attributed to the decrease in the active species during the reaction process because of the fracture. In contrast, the peaks of Li x Si alloy films around 0.5 V hardly decreased. This result suggests that delamination and fracture by volumetric change during charge-discharge processes were suppressed in Li x Si alloy films because of their softness. Thus, the analyses of the highly-dense Li x Si alloy films fabricated by the APD method clarified that cycle stabilities of active materials were improved by controlling mechanical properties.[1] Ashuri, M.et al., Nanoscale 2016, 8, (1), 74-103.[2] Sitinamaluwa, H. et al., RSC Adv. 2017, 7, 13487-13497.[3] Asano, S. et al., Highly-dense and smooth amorphous silicon films fabricated by arc plasma deposition and electrochemical properties., ACSSI-17, 3A-06, 9.15.2022.

Research on reactivity evaluation and micro-mechanism of various solid waste powders for alkali-activated cementitious materials

Alkali-activated cementitious material (AACM) based on the utilization of solid waste is a new type of environmentally friendly inorganic material, which has the advantages of early strength, fast hardening, high strength, and better durability. The reactivity of solid waste powder is a key factor for its appropriate utilization in alkali-activated cementitious materials, necessitating a rational evaluation of its reactivity. The reactivity evaluation was conducted on various solid waste powders, including fly ash (FA), red mud (RM), recycled micro-powder (RMP), red brick powder (RBP), coal gangue powder (CGP), and cement kiln dust (CKD). The effects of NaOH concentration, weight ratio of water to solid waste powder (W/P) and curing humidity on the compressive strength were investigated，then the compressive strength under optimal conditions was determined based on response surface analysis. The compressive strength under optimal conditions was used to evaluate the reactivity of solid waste powders. Moreover, microscopic tests (e.g., XPS test, ICP test, and NMR test) were carried to evaluate the reactivity of the solid waste. The relative number of bridging oxygen (RBO) measured by the NMR method in conjunction with chemical composition analysis serves as an effective method for evaluating the reactivity of solid waste powders. The leaching rate of Silicon (Si) and Aluminum (Al) ions in the ICP method depended mainly on the NaOH concentration and the elemental content in the raw material. In addition, the binding energies of O1s, Si 2p, and Al 2p tested by the XPS method had no particular correlation with the compressive strength.

New assignments of Raman spectra of tetrahedra and the effects of electronegativity. II. Silicate glasses

Our density functional theory calculations (by GAUSSIAN) on the Si4O104− moiety and Na4Si4O10 molecule reproduce the experimental Raman frequencies and relative intensities for the three A1 modes in the experimental Raman spectra of Na2Si2O5 and BaSi2O5 crystals and glasses. Taking the center of mass into consideration, accompanied by visualization using GaussView, these calculations provide a firm assignment of these three peaks: the 1060 cm−1 peak to the Si-NBO stretch (NBO = Si–O or Si–O–Na), the ∼600 cm−1 peak to the Si-BO stretch (BO = Si–O–Si), and the ∼500 cm−1 peak to the Si-BO-Si bend. Our GAUSSIAN calculations on modified “non-equilibrium” SiO44− tetrahedra, constrained to have the same Si–O bond lengths and O–Si–O bond angles as in the Si4O104− moiety, confirm the above-mentioned assignment and show reasonable agreement with the experimental Raman frequencies and relative intensities. We then examine the regular trends in the Si-NBO and Si-BO stretch frequencies for all Qn (n = 0–4) species in silicate glasses and crystals. The large systematic change in the differences between these frequencies (Δ1) is explained by electronic changes within the SiO4 tetrahedron. For example, the larger Δ1 for the Q3 tetrahedra than the Q2 tetrahedra is due to the changes in Si, BO, and NBO electron densities on the tetrahedral Si and O atoms, as measured by Si 2p and O 1s x-ray photoelectron spectra. This trend strongly suggests that the Si-BO stretch frequency for the Q4 species in v-SiO2 should be ∼500 cm−1, close to the A1 breathing mode frequency of 495 cm−1 for four membered rings previously assigned.

New assignments of Raman spectra of tetrahedra and the effects of electronegativity. I. P4O10 and Si-containing molecules

Our new density functional theory calculations by Gaussian reproduce the bond lengths and Raman spectra of a number of model tetrahedral Si and P compounds [the ten compounds in the SiHxD4−x and SiFxCl4−x (x = 0–4) series, and the tetramer P4O10]. The number of symmetric A1 peaks is determined by group theory, and the center of mass is especially important for the assignment of the three A1 peaks for P4O10 to the two P–O stretches and the O–P–O bend. Additional Gaussian calculations on isolated C3v PO4 tetrahedra, using the P–O bond lengths and O–P–O bond angles from the P4O10 optimization, also reproduce the three peak P4O10 Raman spectra and provide an important guide to the assignment of the two low energy peaks at ∼500 and ∼700 cm−1 to the P–BO (BO = P–O–P) stretch and BO–P–BO bend, respectively, in contrast to all earlier assignments. In the SiFxCl4−x series, there is a regular increase in the Si–F A1 frequency and a decrease in the Si–Cl A1 frequency across the series. Similar trends are seen in the SiClx(CH3)4−x series, and these trends are due to changes in the electron densities in the tetrahedron when an electronegative F or Cl is replaced by a less electronegative Cl or CH3, as measured by previous Si 2p, F 1s, Cl 2p, and C 1s x-ray photoelectron spectroscopy. These considerations serve as a guide for the interpretation of the Raman spectra of silicate glasses in Paper II [Bancroft et al., AIP Adv. 13, 125216 (2023)].

A systematic study to investigate the effects of x-ray exposure on electrical properties of silicon dioxide thin films using x-ray photoelectron spectroscopy.

X-ray photoelectron spectroscopy (XPS) is generally used for chemical analysis of surfaces and interfaces. This method involves the analysis of changes in binding energies and peak shapes of elements under consideration. It is also possible to use XPS to study the effect of x-ray radiation on the electrical properties of thin films. We measured the Si 2p peak using x-ray powers of 300 and 150W on ∼135nm silicon dioxide (SiO2) thin films grown on both n- and p-type substrates while applying DC or AC external biases. Using the shifts in the binding energy of the Si 2p peak, we calculated the resistances and the capacitances of the SiO2 thin film. The way that the binding energies of the Si 2p peak and the capacitance of the thin film change as a function of the type of Si substrate and the power of the x-ray are explained using band bending.

Paracetamol tablet analyzed by XPS

Paracetamol tablet was analyzed by x-ray photoelectron spectroscopy (XPS). Sample was fixed to a stainless-steel sample holder with a copper double-sided adhesive tape. Survey spectra, C 1s, O 1s, N 1s, Si 2p, Mg 2s, Mg KLL, and Mg 1s core levels spectra were acquired. Results showed the presence of carbon, oxygen, and nitrogen, elements that constitute the chemical structure of paracetamol; however, these can also be part of the excipients. In addition, silicon and magnesium were detected, which are related to excipients.

Evidence for heterogeneous oxidation on the surface of a plasma SiC nanopowder based on synchrotron-excited XPS

The surface chemistry of a plasma SiC nanopowder was characterized by X-ray photoelectron spectroscopy using a tunable synchrotron X-ray source. The sample surface was representative of SiC nanopowder surfaces in interaction with ambient air, with no significant influence from carbonaceous deposits. By choosing an incident photon energy in the range 200–1200 eV, the escape depth of photoelectrons was altered from 0.5 to 3 nm based on the C 1s, Si 2p and O 1s core-level transitions. The spectral series gave evidence for surface enrichment of silica and sp2-bonded elemental carbon. Several models of surface enrichment were tested against the spectral intensities as a function of escape depth. This analysis led to sp2-carbon islands and two types of oxidation depths. While on the larger part of the surface, the silica is only a near-monolayer in thickness, there are surface regions that are oxidized to a depth of ≥3 nm. These heavily oxidized regions are attributed to defected open channel pores on the outer surface of nanoparticle agglomerates, based on the previous electron tomography results.