Effect Of Si Doping Research Articles

Si-doped Al2O3 nanosheet supported Pd for catalytic combustion of propane: effects of Si doping on morphology, thermal stability, and water resistance.

Catalytic combustion of propane as typical light alkanes was important for the purification of industrial VOCs and automobile hydrocarbon emissions. Si-doped Al2O3 nanosheet was synthesized by a hydrothermal method, and effects of Si content on the morphology and thermal stability of Al2O3 were investigated. The doping of SiO2 could tune the thickness of Al2O3 nanosheets and significantly improve its thermal stability, the θ phase was still maintained, and the specific surface area was as high as 56.3 m2 g-1 after calcination at 1200 °C. And then the Si-doped Al2O3 nanosheets were used as support of Pd catalysts (Pd/Si-Al2O3 nanosheets) for catalytic combustion of propane, especially Pd/3.6Si-Al2O3 nanosheets, which presented high activity, stability, and resistance to sintering and H2O due to the promotion of Si on the thermal stability of Al2O3 and the stabilization (dispersion, isolation, and strong interaction) of PdOx species.

Effect of Si Doping on the Performance of GaN Schottky Barrier Ultraviolet Photodetector Grown on Si Substrate

GaN Schottky barrier ultraviolet photodetectors with unintentionally doped GaN and lightly Si-doped n−-GaN absorption layers were successfully fabricated, respectively. The high-quality GaN films on the Si substrate both have a fairly low dislocation density and point defect concentration. More importantly, the effect of Si doping on the performance of the GaN-on-Si Schottky barrier ultraviolet photodetector was studied. It was found that light Si doping in the absorption layer can significantly increase the responsivity under reverse bias, which might be attributed to the persistent photoconductivity that originates from the lowering of the Schottky barrier height. In addition, the devices with unintentionally doped GaN demonstrated a relatively high-speed photo response. We briefly studied the mechanism of changes in Schottky barrier, dark current and the characteristic of response time.

Effect of Si Doping on Photoluminescence Properties of GaAs Nanowires

Effect of Si Doping on Photoluminescence Properties of GaAs Nanowires

Effects of Si doping on the ferromagnetic properties of delta doped GaMnN nanorods

Delta doping (δ-doping) of group-III nitride-based nanostructures such as nanorods (NRs) with transition metals such as manganese (Mn) can lead to one-dimensional (1D) diluted magnetic semiconductors (DMSs). In order to investigate the effects of free carrier doping on the structural, electrical, and magnetic properties of such delta-doped 1D structures, we have used nanosphere lithography to grow uniform arrays of vertically aligned NRs with fixed aspect ratios on single crystal Al2O3 substrates using plasma-assisted molecular beam epitaxy (PAMBE). The precise control of the elemental flux intensity and duration, facilitated by PAMBE, enables the growth of phase-pure nanostructures, resulting in spatial separation on the order of few nanometers, between the δ-Mn layer and the free carriers in the Si:GaN layer. Chemical quantification verifies the presence of Mn and Si, while Raman spectroscopy shows that Si doping enhances the local vibration mode associated with Mn bonded to N as well as the disorder-activated mode. The free carriers do not diminish the inherent magnetic ordering in these 1D structures, while magnetic measurements show a stability in the signal.

Large tunneling magneto-dielectric enhancement in Co(Fe)−MgF2 granular films by minor addition of Si

We report a large enhancement of the tunneling magneto-dielectric (TMD) effect in Co−MgF2 granular films induced by doping using a small amount of Si. This minor addition of Si is dispersed uniformly in the MgF2 matrix and acts by inhibiting the interdiffusion between the Co and MgF2 phases, thus enhancing the magnetization when compared with the case of the corresponding undoped Co−MgF2 films; this consequently results in a greatly enhanced peak dielectric variation (TMD ratio, Δε′/ε′), as indicated by theoretical fittings. Extension of this Si doping effect to CoFe−MgF2 films led to a record-high Δε′/ε′ of 4.3% at 10 kHz and 8.5% at 200 kHz under the application of a magnetic field (H) of 10 kOe, while remaining as high as 2.1% even under H = 1 kOe. This study presents a simple but highly effective approach to enhance the TMD effect in granular nanocomposites, thus opening up the prospect of development of high-performance magnetoelectric devices.

Biyo–Seramik Bileşimine Silisyum Katkısının Osteokondüktif ve Osteoindüktif Özelliklere Etkisi

Bone replacing Ca–phosphate based materials with strong bioactive and osteoconductive properties are being used in many medical and dental applications as coating materials on implant surfaces and as scaffold for the regeneration of bone and dentin. It is possible to produce materials with enhanced biological or physico–chemical properties by doping different suitable ions into hydroxyapatite (HA) structure. Silicon (Si) is the most found element in Earth crust and has many effective properties in living bodies. The main aim of the present study is to supply the current knowledge about apatite materials which contain Si ions. After defining bone, the factors affecting new bone formation, osteoconductivity and osteoinductivity properties, the effect of Si doping into HA structure on osteoconductivite and osteoinductivite features will be mentioned.

Modification of a-C:H films via nitrogen and silicon doping: The way to the superlubricity in moisture atmosphere

Both nitrogen and silicon-doped carbon (a-CNx:H and a-CSi:H) films show superlubrcity properties in distinguished sliding conditions, but most running machines are required to serve in humidity air atmosphere. Therefore, we aim to explore N and Si doping effects on tribology of a-C:H films and reveal the basic factors of superlubricity in open atmosphere with a humidity of 41%. In present work, three kinds of films (a-C:H, a-CNx:H and the a-CSi:H films) were prepared on n-Si(100) substrates by plasma-enhanced chemical vapor deposition (PECVD). The thickness, element distribution, bonding topolograph and nanostructure of all films before and after friction test, including wear debris, tracks and debris, were detected by means of XPS, Raman, HRTEM and SEM, etc.. Compared with hydrogenated carbon film (a-C:H), the highest COF (0.089) and wear rate (3.61 × 10−7 mm3/Nm) of a-CNx:H film are attributed to forming Fe3C, Fe2O3 and Cr2O3 on the slide surface due to the chemical reaction with moisture atmosphere, which caused by the emission of N element via the broken CN structure that induced more activity dangling bonds. However, the silicon-doped carbon film (a-CSi:H) exhibited extremely low COF (0.007) and extremely low wear rate (4.76 × 10−8 mm3/Nm), which can be ascribed to the Si which is more reactive with moisture atmosphere, prohibiting the oxidization of carbon matrix and helping to forming more curved graphene structures to low the friction force.

Effects of Si doping on structural and electrochemical performance of LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

LiNi0.5Mn1.5O4 spinels were prepared by coprecipitation-hydrothermal method followed by high-temperature calcination. Si doping was achieved by acetic acid glacial-assisted sol-gel method using TEOS as Si source. The effect of Si doping contents on the structure, morphology and electrochemical performance of LiNi0.5Mn1.5O4 material was investigated. Si doping can inhibit the formation of LixNi1-xO impurity, but excessive Si doping results in the appearance of Li2SiO3 secondary phase. Si doping can reduce particle size and improve distribution. Electrochemical tests show that Si doping has a positive impact on rate and cycling performances, due to the increased structural stability resulting from stronger SiO bond, and the enhanced Li+ ion diffusion coefficient. Post-mortem analysis shows that Si doping can mitigate the transition metal dissolution and side reactions, thus leading to the enhanced electrochemical performance of Si-doped samples. Among them, LiNi0.5Mn1.5O4 with 6% Si doping exhibits the optimal electrochemical performance.

Significant enhancement of the bias stability of Zn-O-N thin-film transistors via Si doping

Si doping was used to significantly improve the bias stability of ZnON thin-film transistors. Si 3 W (~1%) doped ZnON TFTs showed a saturation mobility of 19.70 cm2/Vs along with remarkable improvements in the threshold voltage shift for negative gate bias stress (NBS) within 1.69 V. The effects of Si doping were interpreted by the experimental correlation between device performance and physical analysis, as well as by the theoretical calculation. Si doping induces the reduction of N-related defects by increasing stoichiometric Zn3N2, and decreasing nonstoichiometric ZnxNy. In addition, Si doping reduces the band edge states below the conduction band. According to density functional theory (DFT) calculations, Si, when it substitutes for Zn, acts as a carrier suppressor in the ZnON matrix.

Effect of Si Doping in Self-Assembled InAs Quantum Dots on Infrared Photodetector Properties

We investigate the characteristics of self-assembled quantum dot infrared photodetectors(QDIPs) based on doping level. Two kinds of QDIP samples are prepared using molecular beam epitaxy : n+-i(QD)-n+ QDIP with undoped quantum dot(QD) active region and n+-n−(QD)-n+ QDIP containing Si direct doped QDs. InAs QDIPs were grown on semi-insulating GaAs (100) wafers by molecular-beam epitaxy. Both top and bottom contact GaAs layer are Si doped at 2×1018/cm3. The QD layers are grown by two-monolayer of InAs deposition and capped by InGaAs layer. For the n+-n−(QD)-n+ structure, Si dopant is directly doped in InAs QD at 2×1017/cm3. Undoped and doped QDIPs show a photoresponse peak at about 8.3 μm, ranging from 6~10 μm at 10 K. The intensity of the doped QDIP photoresponse is higher than that of the undoped QDIP on same temperature. Undoped QDIP yields a photoresponse of up to 50 K, whereas doped QDIP has a response of up to 30 K only. This result suggests that the doping level of QDs should be appropriately determined by compromising between photoresponsivity and operating temperature.

Effect of Si-Doping on the Structure and Conductivity of (Sr/Ca)2MnFeO6-δ Systems

Following previous work on silicate doping of perovskite (Sr/Ca)MnO3 and (Sr/Ca)FeO3- δ materials for potential application as electrode materials for solid oxide fuel cells, here we report the successful incorporation of silicon into the mixed Mn/Fe systems, (Sr/Ca)2MnFeO6-δ. The results show a higher level of Si doping to be possible for Ca2MnFe1-xSixO6— δ (0≤x≤0.4) compared to Sr2MnFe1-xSixO6— δ (0≤x≤0.2). In both cases, the conductivity is improved for low doping levels (x≤0.1), with a subsequent decrease for higher doping levels. Additional preliminary work has shown that phosphate can also be successfully incorporated into these perovskite systems. The work therefore further illustrates the potential of oxyanion doping in perovskite systems of interest for Fuel Cell applications.

Effect of Si doping on the structure and electrochemical performance of high-voltage LiNi0.5Mn0.5O2 cathode

Despite its high energy density, high-voltage LiNi0.5Mn0.5O2 cathode which suffers from a poor cycle performance that originated from the cathode structural collapse is still far from commercialization. Doping heteroatom into the lattice of LiNi0.5Mn0.5O2 is believed to be a valid strategy in overcoming this bottleneck. Herein, Si was employed as a dopant to comprehensively improve the electrochemical performance of LiNi0.5Mn0.5O2. X-ray diffraction and Rietveld refinement revealed that doping Si into LiNi0.5Mn0.5O2 can optimize its structure, which reduced the degree of Li/Ni cation mixing. As a result, an enhanced interfacial reaction kinetics of Li-ion intercalation/de-intercalation could be achieved, rendering the doped LiNi0.5Mn0.5O2 a remarkably improved reversible capacity in comparison with its pristine. Moreover, it was found that Li0.99Si0.01Ni0.5Mn0.5O2 showed a significantly higher capacity than LiNi0.5Mn0.5O2 does at 25 °C. It is believed that this work affords an effective strategy for high-performance LiNi0.5Mn0.5O2 cathode.

Effect of Si doping on the structure and optical properties of Ge2Sb2Te5 studied by ab initio calculations

Ge2Sb2Te5 (GST) alloys have the ability of rapidly transforming between amorphous and crystalline phases, therefore, they can be adopted in the non-volatile phase change memory. Here, using First-Principles Molecular Dynamic Simulations, we studied the amorphous process of Si-doped GST and its possible applications, the effect of Si doping on the structure and optical properties of GST was studied by ab initio calculations. The results show that the Si doping can improve the stability of GST material and the 20% Si-doped GST is the most stable. Moreover, by analysis the complex dielectric function, absorption, reflectivity, and conductivity, it can be seen from the optical properties that 20% Si-doped GST has a lower turn-on voltage, lower RESET current compared with GST which provides a theoretical basis for the application of GST materials in optical storage devices.

Si Doping Effects on the Growth of Large Single-Crystal Diamond in a Ni-Based Metal Catalyst System under High Pressure and High Temperature

Si powder was added to Ni-based metal catalysts under high pressure and high temperature conditions to investigate its effects on the growth of large single-crystal diamonds. As the Si content increased, the internal inclusions of the diamonds showed a trend in the distribution of point-like → sheet-like → string-like, illustrating that it is ultimately difficult to grow intact crystals. The results show that the first-order Raman peak shifted from 1331.71 to 1329.76 cm–1, and its full width at half-maximum increased from 3.945 to 4.976 cm–1. These results indicate that the Si doping caused an increase in the stresses inside the crystal and that the crystalline quality of the diamond became worse. The Raman and X-ray photoelectron spectroscopy results confirm that the inclusion impurities (graphite, amorphous carbon, and Si3N4) in diamond increase with the Si content. There are significant interactions between silicon and nitrogen in the synthesis process. The addition of Si reduces the nitrogen concentration in diamond. Meanwhile, the presence of nitrogen also reduces the effectiveness of Si doping into diamond.

Si-doped polycrystalline via chemical deposition

Microcrystalline diamond films doped with silicon have been grown on aluminum nitride substrates by a microwave plasma CVD. The doping has been performed via adding silane in various concentrations to CH4–H2 reaction gas mixture in course of the deposition process. The films produced at the substrate temperatures of 750 to 950°C have been characterized by SEM, AFM, Raman and photoluminescence (PL) spectroscopy to assess the effect of Si doping on the diamond structure. The doped films showed bright photoluminescence of silicon-vacancy (SiV) color centers at 738 nm wavelength as well as noticeable side band at 723 nm. The optimum doping condition (SiH4/CH4 = 0.6%), that maximize the SiV PL emission, was determined for the range of silane concentrations SiH4/CH4 (0.0 – 0.9%) explored. A further PL enhancement can be achieved by increase in the substrate temperature. The applied in situ doping from gas phase is shown to be an easy and effective method to incorporate Si in diamond in a controllable way.

Si-doping effect on solution-processed In-O thin-film transistors

In this work, silicon-doped indium oxide thin-film transistors (TFTs) have been fabricated for the first time by a solution processing method. By varying the Si concentration in the In2O3–SiO2 binary oxide structure up to 15 at%, the thicknesses, densities, and crystallinity of the resulting In–Si–O (ISO) thin films were investigated by x-ray reflectivity (XRR) and x-ray diffraction techniques, while the produced TFTs were characterized by a conventional three-probe method. The results of XRR analysis revealed that the increase in the content of Si dopant increased the thickness of the produced film and reduced its density, and that all the Si-doped ISO thin films contained only a single amorphous phase even after annealing at temperatures as high as 800 °C. The manufactured ISO TFTs exhibited a reduction in the absolute value of threshold voltage VT close to 0 V and low current in the off-state, as compared to those of the non-doped indium oxide films, due to the reduced number of oxygen defects, which was consistent with the behavior of ISO TFTs fabricated by a sputtering method. The ISO TFT with a Si content of 3 at% annealed at 400 °C demonstrated the smallest subthreshold swing of 0.5 V/dec, VT of −5 V, mobility of 0.21 cm2 V−1s−1, and on/off current ratio of about 2 × 107.

Effect of Si Doping on Magnetic and Magnetocaloric Properties of Ni–Co–Mn–Sn Alloys

Herein, the magnetic, exchange bias (EB), and magnetocaloric properties of polycrystalline Ni48Co1.5Mn35Sn15.5− x Si x ( $x=1$ , 2, and 4) Heusler alloys have been investigated by magnetic measurements. All these alloys are found to undergo a first-order structural phase transition from martensite to austenite along with a second-order ferromagnetic to paramagnetic transition. It is observed that martensitic transition temperature shifts to lower temperature with increasing Si substitution in place of Sn, whereas the Curie temperature is insensitive to the doping amount. Magnetic entropy change ( $\Delta S_{M}$ ) and net relative cooling power are measured across martensite to austenite transition and the corresponding values are found to 10.86, 5.46, 2.42 Jkg−1K−1 and 122.7, 144.5, and 63 Jkg−1 for $x=1$ , 2, and 4 alloys due to a field change of 50 kOe, respectively. Interestingly, with increasing Si substitution in place of Sn, hysteresis loss reduces significantly from 52.1 J/kg ( $x=1$ ) to 8.62 J/kg ( $x=4$ ). However, the EB property of these alloys does not change significantly due to the doping amount.

Alternating Magnetic Force Microscopy: Effect of Si doping on the temporal performance degradation of amorphous FeCoB magnetic tips

In order to increase the resolution of traditional MFM and extend its applications in the past, we created an Alternating Magnetic Force Microscopy (A-MFM) with a magnetic force modulation by applying an off-resonance AC magnetic field. A new magnetic tip has been developed for A-MFM in this work. Perpendicular magnetic recording medium with 500 kfci recording density is successfully imaged and analyzed by using the new tips coated by 6–15 nm amorphous FeCoSiB-based soft magnetic film. The effect of Si doping to the magnetic film on the A-MFM imaging was studied. It was found that Si additive had no effect on the imaging properties, such as signal-to-noise ratio and spatial resolution (kept at ∼5 nm level). But on other side, Si additive significantly degraded the chemical stability of FeCoSiB film due to oxidation in ambient atmosphere. Surface passivation by metal and boron oxides is considered to have a main effect on improvement of chemical stability of Si-free magnetic coating. The results have shown that Si-free FeCoB-based magnetic tips are appropriate candidates for A-MFM imaging in ambient conditions.

Manipulation of Si Doping Concentration for Modification of the Electric Field and Carrier Injection for AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes

Electron overflow is one of the key factors that limit the quantum efficiency for AlGaN-based deep-ultraviolet light-emitting diodes. In this work, we report a numerical study to improve the electron injection efficiency by manipulating the electric field profiles via doping the n-Al0.60Ga0.40N electron source layer with different concentrations and reveal the physical mechanism of the Si doping effect on the electron and the hole injection. By utilizing the appropriate doping concentration, the electric field will reduce the electron drift velocity and, thus, the mean free path. Therefore, a higher electron capture efficiency by the multiple quantum wells (MQWs) and an increase of the hole concentration in the active region can be realized, resulting in an improved radiative recombination rate and an optical output power.

Structure and electronic properties of Si-doped CeO2 (111) surface by the first principle method

This study aimed to determine the effects of Si doping in CeO2 (111) surface on the polishing performance. For this purpose, the structure and electronic properties of pure CeO2 (111) surface and Si-doped surface were calculated and compared by the first principles based on density functional theory. The reduction capabilities of the two surface systems were analyzed. Calculated results demonstrate that the ionic structure of Si-doped surface presents a symmetric change and that the formation energy of surface O vacancy decreases by 1.388 eV, indicating that Si doping is conducive for the reduction in surface system. Two electrons left by the O vacancy in the reduction system are obtained by the nearest 2 Ce4+, and the Ce4+ are reduced to Ce3+. After Si doping, the hybridization state between Si ion and adjacent Ce and O ions occurs at the Fermi level. Therefore, the synergistic effect of Si doping and O vacancy can enhance the reactivity of CeO2 polishing particle surface.