Si 2p Research Articles

XPS characterization of cobalt impregnated SiO2 and γ‐Al2O3

SiO2 and γ‐Al2O3 impregnation with nominal 10 and 20% of cobalt was examined using wet impregnation method starting with Co(NO3)2·6H2O. The samples were dried and analyzed by XPS prior to calcination to study the surface species in the solids and the role of the support in the processing of supported cobalt catalysts. The results showed that cobalt introduction alters the few top nanometers of the support materials as there are significant changes recorded in the XPS spectra. Most importantly, there is a remarkable similarity between the O 1s XPS signal of SiO2 and γ‐Al2O3 following Co 20% impregnation, which suggests that these materials could have similar properties in terms of the oxidation ability and the general redox behavior. The shift of Al 2p peaks to higher binding energy (BE) in the XPS investigations and the shift of Si 2p peaks to lower BE were observed for high nominal cobalt loading. These results suggest that the choice of the support in cobalt‐based catalysts would tune the chemical characteristics of cobalt in the final materials.

XPS analysis of [formula omitted] and its [formula omitted]-subsituted alloy

The investigation reported is the study of electronic structure of the intermetallic compound Gd5Ge2Si2 and its Co-substitution i.e. Gd5Ge1.9Si2Co0.1 with the help of X-ray photoelectron spectroscopy (XPS). The investigations reveal the crystallization of the compounds to be in a single phase with Orthorhombic structure. The XPS spectra disclose the signature peaks of the various orbitals of the constituent elements of the compounds. Though a subtle shift in the binding energy values is observed. The deconvoluted XPS spectra provides the interaction of the core of the compounds with different neighbours. Deconvolution shows that for Gd(3d) spectra the strongest bonding is for Gd-Ge bond with a binding energy value of ∼ 1190 eV for both the compounds. Also, for Si(2p) spectra this value is close to 102 eV for Si-Ge bond.

Mechanical Transformation of Fly Ash toward Its Utilization in Cemented Paste Backfill

Fly ash (FA) showed low reactivity when being used to prepare the binder for cemented paste backfill (CPB). In the present work, wet‐grinding treatment was used to increase the pozzolanic reactivity of FA and promote its sustainable utilization. The results showed that wet‐grinding could be a suitable and efficient technology for FA pretreatment. Wet‐grinding strongly modified the structure of FA by decreasing the crystalline phase content and the binding energy of Si 2p and Al 2p, contributing to the increase in pozzolanic reactivity of FA. The performance of CPB samples prepared by wet‐ground FA was then optimized. This was reflected by the acceleration in the sample setting and increase in the strength development. The compressive strength of the CPB samples prepared by wet‐ground FA for 120 min was increased by around 40% after curing for 28 d compared with the control samples.

Instrumentation for tracking electrochemical reactions by x-ray photoelectron spectroscopy under conventional vacuum conditions

A bias application system for tracking electrochemical reactions by x-ray photoelectron spectroscopy (XPS) is constructed using a laboratory-based apparatus. A specialized sample holder and stage with three electrical terminals provide contacts to a potentio-galvanostat on the outside, allowing bias application to an electrochemical device in the analysis chamber under vacuum conditions. The application of a direct current bias voltage to the sample holder is confirmed using metal Au samples. The Au 4f peaks from the Au grounded to the analyzer are identical, while those from the Au insulated from the analyzer shift due to the applied bias voltage. Furthermore, galvanostatic lithiation/delithiation processes and in situ XPS measurements are performed on a Si thin-film electrode after transferring the sample into the XPS apparatus without exposure to open air using a newly developed transfer vessel. After the initial lithiation process, a Li 1s peak containing a lithium-silicide component appears, and the Si 2p peaks shift to a lower binding energy due to the lithiation of the Si electrode. After the subsequent delithiation process, the Si 2p peak from the lithium silicide partially shifts back to a higher binding energy. As a result, in situ XPS measurements of the lithiation/delithiation reactions are successfully performed using the developed system.

Exploring the structures and properties of nickel silicides at the pressures of the Earth's core.

Given the highly possible existence of nickel and silicon in the Earth's core, the study of the reaction between Ni and Si and the resulting structures at the pressure corresponding to that of the Earth's core is highly required. Therefore, we have investigated the crystal structures of Ni-Si compounds at pressures of 0-350 GPa by adopting a crystal structure search algorithm in conjunction with first-principles calculations. We uncover two high Ni-content Ni5Si and Ni6Si compounds with 12-coordination Si bonded with Ni, with both showing strong chemical stability in the Earth's core. Bonding analysis reveals that the Ni atoms in these Ni-Si compounds present oxidant features and act as electron acceptors. This distinctive anomaly is the natural result of the energy shifts of the Ni 3d and Si 3p bands, resulting in charge transfer from Si to Ni. By examining the key properties (e.g., density and sound velocities) of the Ni5Si and Ni6Si compounds, the obtained density lies within the range of the Earth's inner core, and the estimated sound velocities are found to be consistent with seismic data. These results indicate that these two compounds could be considered as possible core constituents. Our findings provide valuable insights into the enigmatic Earth's core as well as geophysical and geochemical processes.

New Tools for Imaging Neutrophils: Work Function Mapping and Element-Specific, Label-Free Imaging of Cellular Structures.

Photoemission electron microscopy and imaging X-ray photoelectron spectroscopy are today frequently used to obtain chemical and electronic states, chemical shifts, work function profiles within the fields of surface- and material sciences. Lately, because of recent technological advances, these tools have also been valuable within life sciences. In this study, we have investigated the power of photoemission electron microscopy and imaging X-ray photoelectron spectroscopy for visualization of human neutrophil granulocytes. These cells, commonly called neutrophils, are essential for our innate immune system. We hereby investigate the structure and morphology of neutrophils when adhered to gold and silicon surfaces. Energy-filtered imaging of single cells are acquired. The characteristic polymorphonuclear cellular nuclei divided into 2–5 lobes is visualized. Element-specific imaging is achieved based on O 1s, P 2p, C 1s, Si 2p, and N 1s core level spectra, delivering elemental distribution with submicrometer resolution, illustrating the strength of this type of cellular morphological studies.

Enrichment of aluminium in the near‐surface region of natural quartzite rock after aluminium exposure

Alkali–silica reaction (ASR) is an ongoing problem that causes damage to concrete constructions and reduces their durability. Therefore, minimizing this undesired reaction is of great interest for both safety and economic reasons. Additives containing high aluminium content are very effective in reducing the release of silica and enhancing the durability of concrete; however, the mechanism for this effect is still under discussion. In this study, an enrichment of aluminium in the near‐surface region was observed for natural quartzite rock after storage in Al (OH)3 and metakaolin as aluminium sources, from which we conclude that the formation of aluminosilicate sheets of a few nanometres inhibits the silica release; this hypothesis is supported by high‐resolution spectra of Al 2p, Si 2p and O 1s.

Sildenafil tablet analyzed by XPS

Sildenafil tablet was analyzed by x-ray photoelectron spectroscopy. Sample was fixed to a stainless-steel sample holder with a copper double-sided adhesive tape. Survey spectrum, C 1s, O 1s, N 1s, S 2p, Si 2p, Mg 1s, and Na 1s core levels spectra were acquired. Results showed the presence of carbon, oxygen, nitrogen, and sulfur, elements that constitute sildenafil; however, carbon and oxygen are also found in other ingredients (excipients). Additionally, the presence of silicon, sodium, and magnesium is associated with excipients.

Drastic change in surface electronic properties and creation of a new carbon-based nanostructure on the vicinal SiC(111)-4° surface

Novel carbon based nanostructure on the vicinal SiC(111)-4° surface has been found as effect of Cs adsorption. The SiC(111)-4°sample was grown by method of epitaxy of low-defect unstressed nanoscaled silicon carbide films on vicinal Si(111)-4° substrate. Electronic structure of the SiC(111)-4° surface and the Cs/SiC(111)-4°interface has been detailed studied in situ in an ultrahigh vacuum using synchrotron-based photoelectron spectroscopy. The C 1s and Si 2p core level spectra have been investigated as a function of Cs submonolayer coverage. A unique fine structure of the C 1s core level spectrum was revealed to appear under Cs atomic layer deposition. The effect was ascertained and shown to be originated from the interaction of the silicon vacancy with adsorbed Cs atoms that leads to both the redistribution of electron density and surface reconstruction with formation of a new type of the C-enriched aromatic-like nanostructure.

Formation and Evaluation of Al2O3 Layer By Direct ALD on Epitaxial SiGe

In recent years, SiGe and Ge have drawn considerable attention as a high mobility channel material toward next-generation complementary metal-oxide-semiconductor (CMOS) circuits. In particular, by inducing strain into Ge using Ge/SiGe hetero-structure, highly enhanced mobility which greatly exceed the bulk mobility have been reported [1]. In order to obtain high mobility, it is necessary to generate larger strain. As one of the methods, strained SiGe on Ge-on-Si is expected. In addition, in order to realize a high mobility SiGe channel MOSFET, it is necessary to form the high-quality gate stacks and interfaces between a gate insulator film and a SiGe surface. In fact, the use of atomic layer deposition (ALD) or plasma oxidation has provided a high quality interface between Ge and the insulator film [2, 3]. However, unlike Si, wet cleaning of Ge or hydrofluoric acid treatment does not provide a high-quality hydrogen-terminated surface, and there is concern about surface oxidation and impurity adsorption. Therefore, we have attempted direct ALD on epitaxially grown Ge and reported that the Ge/Al2O3 interface properties are improved [4]. In the case of SiGe, a high-quality hydrogen-terminated surface cannot be obtained by wet cleaning or hydrofluoric acid treatment. For this reason, oxidation or impurity adsorption on the SiGe surface is feared. In this study, for the application to strained SiGe channel MOSFET, an Al2O3 film was formed using ALD on epitaxially grown SiGe as a gate stack structure on SiGe, and the interface structure was evaluated.Two types of samples were prepared by two methods. An n-type Ge (100) substrate was used in this study. The Ge substrate was chemically cleaned with NH4OH solution and followed by a HF dip and de-ionized water rinse. The wet-cleaned Ge substrate was loaded into an MBE chamber and subjected to thermal cleaning at 600 °C for 10 min. Subsequently, a 50 nm thick SiGe layer (called epi-SiGe hereafter) was hetero-epitaxially grown on the Ge substrate at 300 °C. The as-grown sample was subsequently transferred to the vacuum-connected ALD chamber and an Al2O3 film was deposited by ALD (Sample (A)). For comparison, after the epitaxial growth of the SiGe, the sample was once taken out from the chamber and exposed to the atmosphere for 5 min. The sample was then reloaded into the ALD chamber and an Al2O3 film was deposited (sample (B)). ALD of Al2O3 films was carried out for 20 cycles with precursors of TMA and H2O at a substrate temperature of 300 °C. Chemical bonding states were examined by x-ray photoelectron spectroscopy (XPS) using an ESCA-300 manufactured by Scienta Instruments AB.According to figs.1 (a) and (b), it was confirmed that the GeOx peak of the sample (A) transferred in a vacuum was significantly smaller than that of the sample (B) once exposed to the atmosphere. In particular, almost no Ge4+ peak [5] arising from Ge in GeO2 was observed, indicating that oxidation of Ge was suppressed by transport in vacuum. It is considered that the GeOx peak in the sample (A) is derived from the interface between Al2O3 and SiGe. According to figs.1 (c) and (d), no Si4+ component (binding energy range 102eV to 104eV) is found in the Si 2p 3/2 spectrum of the sample (A) transferred in a vacuum. In summary, XPS analyses reveal that formation of GeO2 and SiO2 by natural oxidation can be almost avoided by ALD on the epitaxial SiGe, and it is indicated that the Al2O3/SiGe interface created does not contain the interfacial GeO2 layer which is present for the sample exposed to the air before ALD. These results clearly indicate that the direct ALD on epitaxial SiGe is very promising way to highly improve the SiGe MOSFET performances.AcknowledgmentsThis work was partly supported by the MEXT Supported Program for the Strategic Research Foundation at Private Universities 2015–2019, a Grant-in-Aid for Scientific Research from MEXT and Interdisciplinary Research Center for Nano Science and Technology in Tokyo City University.

In Situ X-Ray Photoelectron Spectroscopy for All-Solid-State Batteries: Analysis of Lithiation and Delithiation Reactions of Silicon Thin-Film Electrode

Si is an attractive anode material for next-generation lithium batteries including all-solid-state batteries because it has a high theoretical capacity density (4200 mAh g-1). However, Si suffers from the irreversible capacity loss related to the severe volume expansion/shrinkage during the lithiation/delithiation processes. In liquid-type batteries, the main cause of the capacity loss is the continuous formation/decomposition of the solid electrolyte interphase (SEI) on the Si anodes [1]. However, the capacity loss of the Si anode is also regarded as a serious issue even in all-solid-state batteries without using electrolyte solution. Thus, a fundamental understanding of the lithiation/delithiation reactions of the Si anode is important to solve the problem. X-ray photoelectron spectroscopy (XPS) enables us to analyze the elemental composition, oxidation states, and electronic structure of the sample surface. In situelectrochemical XPS, which can measure the same position of a sample under the operational condition for batteries, allows a stepwise analysis of the reactions without interference from variation and inhomogeneity of samples [2]. Here, lithiation/delithiation reactions of an amorphous Si electrode in a thin-film cell is investigated by using an XPS apparatus equipped with an applying voltage system [3]. The amorphous Si with a thickness of about 100 nm is formed on the Li6.6La3Zr1.6Ta0. 4O12 (LLZT) sheet by radio-frequency magnetron sputtering, and the Cu is further coated on the sputtered Si layer by DC sputtering. During the Cu deposition, a stainless-steel stencil mask is used to yield an uncoated amorphous Si part with a diameter of about 2 mm as an analytical region for the XPS measurements. The Li metal layer is thermally deposited on the other side of LLZT. After the thin-film cell with the final structure of [Cu/Si(100 nm)/LLZT(500 µm)/Li metal(1.3 µm)] is connected to the sample holder in an Ar-filled glove box, it is transferred to the XPS apparatus by using a vacuum suitcase to prevent from exposing to open air. The cell is cycled between 0.01 and 1.2 V at 0.02C (1.245 µA) in UHV chamber of the XPS apparatus. The Si surface is observed by XPS before/after the lithiation/delithiation processes. The galvanostatic potential profiles show that the capacity for the first lithiation and delithiation processes is 3160 and 2977 mAh g-1, respectively. A broad Li 1s peak appears after the first lithiation process, confirming the Li insertion to the Si electrode. According to the peak fitting, the Li 1s peak is composed of lithium-silicide (LixSi), Li2O, and Li2CO3. The Li2O and Li2CO3 are possibly formed by the reaction of the lithium-silicide surface with a trace amount of residual gas from the vacuum chamber and LLZT. The Li2O and Li2CO3 contribute to the irreversible capacity loss because these components remain even after the subsequent delithiation process. In the Si 2p region, peaks originated from bulk Si (Si0) at 99.1 eV and Si suboxide (SiOx) at 101.9 eV are shifted to lower binding energy side. These peak shifts indicate the formation of lithium-silicide (LixSi) and lithium-silicate (Li4SiO4) due to the insertion of Li ions to each layer. Based on the calculation using the peak intensities and known physical parameters, it is proposed that the Si electrode has a surface structure of [Li2O (2.5 nm)/Li4SiO4 (0.9 nm)/LixSi] at this state. In addition, the composition of the LixSi is estimated to be Li3.27Si from the charge integration and the thickness of each layer. After the subsequent delithiation process, the Li4SiO4 peak remains in the same position. In contrast to the immobility of the Li4SiO4 peak, the LixSi peak is shifted back to the higher binding energy side, but it does not completely return to the original position of the Si0 peak. The composition of the lithium-silicide phase at this state is estimated to be Li0.14Si. Therefore, Li trapped in Li0.14Si and formation of Li4SiO4, Li2O, and Li2CO3 contribute to the irreversible capacity loss of the Si electrode.

Ru(0001) and SiO2/Ru(0001): XPS study

X-ray photoelectron spectroscopy (XPS) is used to analyze the chemistry of the Ru(0001) film surface and the Ru/SiO2 interfacial region at different annealing conditions. The XPS spectra are collected under ultrahigh vacuum (base pressure of ∼5 × 10−10 Torr) condition using a SPECS electron spectrometer with a PHOIBOS 100 hemispherical energy analyzer and an XR 50 Al Kα x-ray source (1486.67 eV). High-resolution spectra of O 1s, Ru 3d/C 1s, and Si 2p together with survey scans are presented. The presence of 1 × 1 low energy diffraction pattern, collected from a 950 °C Ar/H2 step-annealed Ru(0001) sample, confirms the hexagonal periodicity of Ru(0001) surfaces.

Structural, electronic, and electrical behaviour of MWCNTs: TiO2 (:SiO2) nanocomposites

We have functionalized multiwall carbon nanotubes (MWCNTs) with the composition of SiO2 and TiO2 (MWCNTs:TiO2:SiO2) at different Ti:Si stoichiometric ratios (Ti:Si ≈ 6:6 at% and ≈10:10 at%) using the hydrothermal process. The micro-structural, electronic and electrical properties of the unfunctionalized and functionalized MWCNTs were studied. Changes in surface morphology, degree of hybridization, crystallite structure and bonding structure due to functionalization were studied using field-emission scanning electron microscopy, Raman spectroscopy, x-ray diffraction, x-ray photoemission spectroscopy (XPS) and x-ray absorption near edge structure (XANES) spectroscopy techniques. Memristive and charge storage properties for MWCNTs:TiO2:SiO2 nanocomposites (NCs) are more pronounced on NCs functionalised with high stoichiometric ratio (Ti:Si ≈ 10:10) due to the contribution of Ti3+ and Si 2p core states as indicated by XPS and XANES results. The tunability of electrical conductivity is shown by an increase in the measured current and semiconducting I–V behaviour of the material as a result of high content of Ti-charge transfer. These observed changes in the electrical behaviour and electronic/bonding structure of the NCs indicate that the material could be useful for electrical/electronic applications and photocatalytic activity.

Structure and hydrogen generation mechanism of Si-based agent

Si-based agent fabricated from Si powder generates a high amount of hydrogen by reactions with weak alkaline solutions for long periods (e.g., more than 500 mL/g hydrogen at pH8.5 and 36 °C for 24 h). The hydrogen generation rate greatly increases with pH, indicating that the reacting species is OH− ions. In the Si 2p XPS spectra of Si-based agent, peaks due to suboxide species and SiO2 are present. The suboxide layer is present near the Si core, and the SiO2 layer outside of the suboxide layer. The charging effect caused by photoemission largely shifts the Si 2p peak due to SiO2 while the shifts induced by charging are much lower for suboxide species. This phenomenon is well explained by the silicon oxide structure that SiO2 is present outside of the suboxide species.

Pozzolanic activity of corn straw leaf ash produced at different temperatures and treated with portlandite solution

The effect of calcination temperature on the pozzolanic activity of corn straw leaf ash (CSLA) was evaluated. The CSLA samples calcined at temperatures of 500, 700, and 850 °C were mixed in a portlandite solution for 6 h, and residual samples were obtained. The CSLA and residual samples were analyzed using Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and a contact angle goniometer to determine the vibration bonds, minerals, phase composition, microstructure, Si 2p transformation behavior, and wetting behavior. The conductivity and loss of conductivity with mixing time of the CSLA-portlandite mixed solution was determined. The loss of conductivity of the CSLA prepared at 500 °C was high compared to that of the other calcination temperatures at the same mixing time, which was attributed to the higher amorphous SiO2 content in the CSLA at 500 °C. Calcium silicate hydrate was easily identified in the CSLA residual samples, and some dense small cubic and nearly spherical shaped calcium silicate hydrate particles were found in the CSLA residual samples at 500 °C. Based on the findings, it is recommended that CSLA be calcined at 500 °C using the cement system in view of higher pozzolanic activity but avoiding excessive agglomeration.

Time-resolved X-ray photoelectron diffraction using an angle-resolved time-of-flight electron analyzer

X-ray photoelectron diffraction (XPD) provides atomic resolution, element sensitive local structure information about the surfaces and interfaces of materials. In the work reported in this paper, a two-dimensional angle resolved time-of-flight (2DARTOF) system is used to perform time-resolved XPD experiments on epitaxial silicene. The two Si 2p peak components from the different atomic sites in the silicene layer allow extraction of the individual XPD patterns. Time-resolved measurements captured small angle shifts in the forward focusing peak, indicating laser-induced changes in the silicene structure. At 10 ns, the XPD patterns appear to relax back to the equilibrium state. This work demonstrates that 2DARTOF systems are well suitable for time-resolved XPD measurements.

Electronic structure studies on single crystalline Nd2PdSi3, an exotic Nd-based intermetallic: evidence for Nd 4f hybridization

In the series R2PdSi3, Nd2PdSi3 is an anomalous compound in the sense that it exhibits ferromagnetic order unlike other members in this family. The magnetic ordering temperature is also unusually high compared to the expected value for a Nd-based system, assuming 4f localization. Here, we have studied the electronic structure of single crystalline Nd2PdSi3 employing high resolution photoemission spectroscopy and ab initio band structure calculations. Theoretical results obtained for the effective on-site Coulomb energy of 6 eV corroborate well with the experimental valence band spectra. While there is significant Pd 4d–Nd 4f hybridization, the states near the Fermi level are found to be dominated by hybridized Nd 4f–Si 3p states, which is possibly responsible for the ferromagnetism in Nd compound. Nd 3d core level spectrum exhibits multiple features manifesting strong final state effects due to electron correlation, charge transfer and collective excitations. These results serve as one of the rare demonstrations of hybridization of Nd 4f states with the conduction electrons possibly responsible for the exoticity of this compound.

Formation of BN-covered silicene on ZrB2/Si(111) by adsorption of NO and thermal processes.

We have investigated the adsorption and thermal reaction processes of NO with silicene spontaneously formed on the ZrB2/Si(111) substrate using synchrotron radiation x-ray photoelectron spectroscopy (XPS) and density-functional theory calculations. NO is dissociatively adsorbed on the silicene surface at 300 K. An atomic nitrogen is bonded to three Si atoms most probably by a substitutional adsorption with a Si atom of silicene (N≡Si3). An atomic oxygen is inserted between two Si atoms of the silicene (Si-O-Si). With increasing NO exposure, the two-dimensional honeycomb silicene structure gets destroyed, judging from the decay of typical Si 2p spectra for silicene. After a large amount of NO exposure, the oxidation state of Si becomes Si4+ predominantly, and the intensity of the XPS peaks of the ZrB2 substrate decreases, indicating that complicated silicon oxinitride species have developed three-dimensionally. By heating above 900 K, the oxide species start to desorb from the surface, but nitrogen-bonded species still exist. After flashing at 1053 K, no oxygen species is observed on the surface; SiN species are temporally formed as a metastable species and BN species also start to develop. In addition, the silicene structure is restored on the ZrB2/Si(111) substrate. After prolonged heating at 1053 K, most of nitrogen atoms are bonded to B atoms to form a BN layer at the topmost surface. Thus, BN-covered silicene is formed on the ZrB2/Si(111) substrate by the adsorption of NO at 300 K and prolonged heating at 1053 K.

Moderate bandgap and high carrier mobility simultaneously realized in bilayer silicene by oxidation

Semiconductors simultaneously possessing high carrier mobility, moderate bandgap, and ambient environment stability are so important to modern industry, and Si-based semiconducting materials can match well with the previous silicon-based electronic components. Thus, searching for such Si-based semiconductors has been one hot project due to the lack of them nowadays. Here, with the help of density functional theory, we found that the full-oxidized bilayer silicene exhibits high carrier mobility with a moderate direct bandgap of 1.02 eV. The high carrier mobility is derived from the remaining of big π bond, and the moderate bandgap is opened by the saturation of dangling Si 3p bonds. Originated from the formation of strong Si-O and Si-Si bonds, the sample exhibits strong thermodynamic and dynamical stabilities. Our work indicates that the full-oxidized bilayer silicene has many potential applications in modern electronic fields.

Evaluation of stabilities and thermophysical properties of Si-Sr intermetallics based on first-principles analysis

First-principles calculations have been used for investigating the structural stability, elastic properties, electronic structure and thermodynamic properties of Si-Sr intermetallics (Si2Sr, Si6Sr, SiSr, Si3Sr5 and SiSr2). The calculated results show that all of them are thermodynamically stable at ground state. The bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio have been deduced from elastic constants, and the values of B/G and Poisson’s ratio have characterized brittleness and ductility of Si-Sr compounds. It is shown that Si6Sr has the highest Young’s modulus, and all calculated Si-Sr compounds in this paper present brittleness. The calculated shear anisotropic factors and elastic anisotropy show that all Si-Sr intermetallics are markedly anisotropic. The calculated electronic structure shows that the DOS of Si-Sr intermetallics are mainly originated from Si 3s, Si 3p and Sr 4d states. We further find that the Debye temperature of Si3Sr5 and SiSr2 is low, which indicates that Si3Sr5 and SiSr2 have weaker chemical bonding and smaller thermal conductivity, matching the results of elastic modulus.