Si Doping Research Articles

Picosecond Operation of Optoelectronic Hybrid Phase Change Memory Based on Si‐Doped Sb Films

AbstractPhase‐change random access memory is anticipated to break the bottleneck of the “storage wall” due to its advantages in simultaneous data storage and in‐memory computing. However, operation speed constrains its application scenarios. Antimony (Sb) thin film has ultrafast phase change speeds, low power consumption, and a straightforward chemical composition. In this study, silicon (Si) doping is employed to enhance the stability of pure Sb while achieving both ultrafast operational speeds and superior thermal stability concurrently. By utilizing optoelectronic hybrid phase change memory, the SET and RESET operation speeds can reach as fast as 26 and 13 ps, respectively, when using Si‐doped Sb films. The absence of the Si─Sb bond results in simple cubic nuclei within the amorphous film, which is posited as the structural basis for the high operational speed. These novel insights into ultrafast speed and phase mechanisms are poised to have valuable evidence for future high‐speed memory designs.

Nearly Barrierless Polarization Switching Mechanisms in ZrO2 Having Perpendicular In-Plane Domain Walls.

The polarization switching mechanism in ferroelectric ZrO2 involves the nucleation and subsequent migration of nonpolar domain boundaries; however, the fundamental mechanism driving this process remains inadequately understood. The present study introduces a mechanism for nearly barrierless polarization switching in 180° domain walls, facilitated by a the half-unit-cell nonpolar phase between oppositely polarized domains. Based on density functional theory (DFT) calculations, two types of 180° domain walls are explored, featuring head-to-head and tail-to-tail polarization boundaries, with nonpolar orthorhombic Pbcm and tetragonal P42/nmc phases as the respective domain walls. The calculations reveal exceptionally low energy barriers of 17.5 and 10.1 meV for migrating these Pbcm and P42/nmc boundaries by half a unit cell through the domains. An evaluation of the impact of defects on domain wall motion is achieved by introducing 2% oxygen vacancies or 3% Si doping, which induces a significant increase in the barrier motion activation energy, suggesting that defects serve as barriers to polarization switching.

Enhancing Thermoelectric Performance of Mg3Sb2 Through Substitutional Doping: Sustainable Energy Solutions via First-Principles Calculations

Mg3Sb2-based materials, part of the Zintl compound family, are known for their low thermal conductivity but face challenges in thermoelectric applications due to their low energy conversion efficiency. This study addressed these limitations through first-principles calculations using the CASTEP module in Materials Studio 8.0, aiming to enhance the thermoelectric performance of Mg3Sb2 via strategic doping. Density functional theory (DFT) calculations were performed to analyze electronic properties, including band structure and density of states (D.O.S.), providing insights into the influence of various dopants. The semiclassical Boltzmann transport theory, implemented in BoltzTrap (version 1.2.5), was used to evaluate key thermoelectric properties such as the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and electronic figure of merit (eZT). The results indicate that doping significantly improved the thermoelectric properties of Mg3Sb2, facilitating a transition from p-type to n-type behavior. Bi doping reduced the band gap from 0.401 eV to 0.144 eV, increasing carrier concentration and mobility, resulting in an electrical conductivity of 1.66 × 106 S/m and an eZT of 0.757. Ge doping increased the Seebeck coefficient to −392.1 μV/K at 300 K and reduced the band gap to 0.09 eV, achieving an electronic ZT of 0.859 with low thermal conductivity (11 W/mK). Si doping enhanced stability and achieved an electrical conductivity of 1.627 × 106 S/m with an electronic thermal conductivity of 11.3 W/mK, improving thermoelectric performance. These findings established the potential of doped Mg3Sb2 as a highly efficient thermoelectric material, paving the way for future research and applications in sustainable energy solutions.

The performance prediction and mechanism study of doped DLC films by the combination of molecular dynamics and first-principles calculations

Doped DLC film is expected to be a vital surface protection material in aerospace and other important fields. However, the long experiment cycle for screening efficient dopants, premature failure caused by high residual stress, and insufficient understanding of the microscopic mechanism, seriously limit its further improvement. In this work, the performance prediction and mechanism study of doped DLC films were proposed by combining molecular dynamics (MD) and first-principles calculations, and the commonly used Si and MoS2 were selected as the typical elemental and compound dopants for investigations, respectively. MD was used to evaluate the influence of both the type of dopant and its amount on the structure and properties, including the content of sp2-C and sp3-C, hardness, elastic modulus, and friction coefficient of DLC films. First-principles calculations were performed to study the modification mechanism of Si and MoS2 dopants from a viewpoint beyond the experimental scale. This study was verified by experimental investigation and proven to make a fast prediction and screening for the doping craft of DLC films.

Detection of an unintentional Si doping gradient in site-controlled GaN nanowires grown using a Si3N4 mask by spatially resolved cathodoluminescence and Raman spectroscopy

Highly uniform arrays of site-controlled GaN nanowires are synthesized by selective area growth using a Si3N4 mask and molecular beam epitaxy. Systematic modulation of the emission along the nanowire axis is observed in spectrally resolved cathodoluminescence linescans. We show that this intensity change is an indicator of unintentional Si incorporation during growth resulting from the interaction between the impinging Ga atoms and the mask material. The gradual reduction of the cathodoluminescence intensity along the nanowire highlights the important role of the growth geometry within the synthesis reactor, with shadowing from the elongating nanowires inhibiting the reaction with the mask. This gradient in Si doping is confirmed by the quenching of the longitudinal optical phonon line measured in Raman spectra along the nanowire axis. The corresponding carrier density is derived from the frequency of the coupled phonon–plasmon mode. The spectroscopic identification of inversion domain boundaries in the majority of the nanowires is also attributed to the Si incorporation. From temperature dependent cathodoluminescence experiments, we derive the activation energy for excitons bound to these defects.

Design and investigation of electrostatic doped heterostructure vertical Si(1-x)Gex/Si nanotube TFET

Researchers are inclining toward heterostructures suitable lattice matching, in Tunnel FETs to eliminate the difficulties of decreased On-Current, subthreshold swings, and ambipolar behavior. Nowadays, Electrostatic doping (ED) is a scrutinized substitute device for creating areas with a high electron or hole density to the conventional doped devices. This manuscript proposes an Electrostatic Doped Heterostructure Vertical Si(1-x)Gex/Si Nanotube Tunnel Field Effect with performance scanned by analyzing the different device parameters, considering the energy band diagram, concentrations of electrons, holes, potential, and electric field. In comparison to the Nanowire TFETs, the area, and rate of tunneling of the proposed device stand superior with a better ION/IOFF ratio of 1.56∗1013 and a lower OFF-current of about ∼10−18A/μm. The device exhibits a Drain current (IDS) of 2.39∗105A/μm. The architecture of the suggested device possessing Si(1-x)Gex/Si structure exhibits enhanced characteristics like improved steepness of the sub-threshold slope, ION/IOFF ratio, drain current, and lowered OFF-current.

Combined effect of silicon doping and thermal treatment on microstructures and mechanical properties of Ti50Nb20V20Al10 refractory high-entropy alloy

This study investigates the effects of Si doping and thermal treatment on the microstructures and mechanical properties of Ti50Nb20V20Al10 refractory high-entropy alloy (RHEA) with a BCC/B2 dual-phase structure. The as-cast RHEAs exhibit typical dendrite and inter-dendrite structure. Upon Si doping, eutectic M5Si3 phase gradually precipitates along the grain boundaries (GBs), resulting in the increase of yield strength (YS) by over 200 MPa. After recrystallization, all the RHEAs exhibit fully recrystallized microstructures. The eutectic M5Si3 phase disappears while forming nanoscale M5Si3 phase distribute along GBs, thereby enhancing the mechanical properties of the RHEAs. Notably, the recrystallized RHEA with 1 at% Si exhibits favorable specific YS (SYS, 172.9 ± 2.9 MPa·cm3·g−1) and fracture elongation (22.8 ± 6.8 %), respectively. The hindrance effect of nanoscale M5Si3 phase on dislocations motion and the transition from planar slip to cross-slip significantly enhance strain hardening capability and plasticity of the RHEAs. Our research findings are of constructive significance to the study of lightweight energetic structural materials.

High Temperature Induced Low Friction and Wear in a-C:Si via Formation of a "H Passivation Layer/a-SiO2/H Passivation Layer" Structure in a Humid Environment.

Doping Si into amorphous carbon can decrease humidity sensitivity, improve thermal stability, and retain excellent friction performance. Experimental studies have shown that Si-doped amorphous carbon formed Si-OH structures and frictional oxides in high-temperature and humid environments. However, the formation process of Si-OH and frictional oxides, as well as their structure, formation conditions, and antifriction properties, remains unclear. In this paper, reactive force field molecular dynamics (ReaxFF MD) was used to investigate the frictional performance of a-C and a-C:Si (7.2 atom %) at temperatures of 300, 700, and 1500 K in H2O environments. The results showed that with increasing temperature, the friction force of a-C increases from 8.2 nN at 300 K to 15.51 nN at 1500 K, while that of a-C:Si decreases from 10.3 nN at 300 K to 5.6 nN at 1500 K. In H2O environments, a-C:Si formed a "H passivation layer/a-SiO2/H passivation layer" structure, which inhibited the formation of interfacial bonds between the upper and lower substrates and reduced the wear of the substrate while ensuring the antifriction and antiwear properties of a-SiO2. This paper reveals the mechanism behind the low friction characteristics of a-C:Si in high-temperature and humid environments, providing theoretical guidance for the application of a-C:Si under such conditions.

Accretion of SiO2/doped-Si cuboid for terahertz absorber and impedance matching

This paper presents an ultra-broadband polarization-insensitive terahertz absorber that consists of a doped Si substrate and a triple-layer of doped Si covered with a SiO2 anti-reflective coating. The finite element method is used to investigate the absorption of the absorber. The absorber exhibits high absorption rates of over 95 % between frequencies of 0.9 THz and 9.2 THz, with a center frequency of 5.05 THz and a relative bandwidth ratio of 164 %. Moreover, it exhibits outstanding wide-angle absorption properties, achieving over 90 % absorption at angles of incidence ranging from 0 to 55° and frequencies spanning from 1.1 to 10 THz. Furthermore, the underlying mechanisms behind broadband absorption and high absorption rates are studied by analyzing the electric field distribution and impedance matching theory. Additionally, this absorber showcases excellent fabrication tolerance. Therefore, the proposed terahertz absorber featuring doped silicon triple-layer stacked arrays has significant potential in applications such as sensing, stealth technology, and biomedicine.

Impact of doping on MgB2 superconductors: A comprehensive review

This review introduces fresh insights into the ongoing discussion on doping in the MgB2 superconductor compound, enriching the comparative analysis with previous reviews. Its primary objective is to succinctly summarize and enhance comprehension regarding the influence of doping on the superconducting properties of MgB2. It delves into various aspects, including the impact on the superconducting transition temperature (Tc) and the critical current density (Jc) of the doped samples, while also shedding light on the diverse synthesis methodologies employed by different research laboratories. Throughout the review, the doping agents under scrutiny encompass a wide array, ranging from Li and Be to Bi and Pb. The properties are compared with those undoped samples crafted by the authors of each publication. This review catalogs a range of cited doping agents, including H, Li, Be, C, C15H12O2, diamond, graphene oxide, NaCl, Na2CO3, Mg, Al, Si, K2CO3, CaH2, CaCO3, Sc, Ti, Ni, Cu, Zn, MgGa, GeO2, Se, Rb2CO3, Rh, Pd, Ag, In, Sn, Sb2O3, Te, Cs2CO3, LaB6, La2O3, CeO2, Pr6O11, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, Os, Ir, Pt, Hg, Pb, and Bi. Notably, doping with Be, Na2CO3, C, Al, Rb2CO3, Cs2CO3, Hg and Pb impacts mesh parameters through either Mg or B substitution. Conversely doping with Li, CaH2, Cu, Ag, La2O3, CeO2, Pr6O11, Nd2O3, Gd2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Lu2O3, GeO2, Rh, In, Sb2O3, and Pt exhibits minimal impact on Tc. Moreover, Jc can be substantially enhanced by adding C, Zn, Ag, or Sb2O3. Remarkably, the incorporation of Pd or Pt has shown a substantial increase in Jc with a remarkable improvement of +328 % and +614 % respectively observed at 2 T and 20 K. Doping with rare earth elements such as La2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, and Ho2O3 resulted in extraordinary improvement in the value of the critical current density at 20 K under specific conditions, within a range of 0–4 T.

Epitaxial Growth and Doping of N-Polar AlN by Plasma-Assisted Molecular Beam Epitaxy

In recent years, AlN has garnered significant attention in the research community due to its excellent electronic properties. AlN, which is an ultra-wide bandgap material with a direct band gap of 6.2 eV, has a high breakdown electric field (12 MV/cm) and high thermal conductivity. In addition, band engineering can be achieved by alloying AlN with Gallium (Ga), Indium (In), and Scandium (Sc), and two-dimensional electron gas (2DEG) is formed at the AlGaN/AlN interface due to strong piezoelectric and spontaneous polarization. Furthermore, AlN has high-temperature stability, which is suitable for application in harsh environments. Due to these unique properties, AlN has gained attention as a promising candidate for the next generation of high power electronic and optoelectronic applications.In this talk, we present the demonstration of controllable Si doping in N-polar AlN films grown on single crystal AlN substrates by plasma assisted molecular beam epitaxy (PAMBE). Through optimization of growth conditions, we obtained high quality N-polar AlN films at high temperatures. However, our studies revealed that Si incorporation dramatically decreases at such high growth temperature. To enable higher Si incorporation, a hybrid growth scheme was developed, using a combination of low-temperature and high-temperature growth condition and by using Ga as a surfactant at low growth temperature. By lowering the growth temperature of AlN to 750°C, we were able to incorporate Si with concentrations as high as 2x1020 cm-3 and demonstrated an electron concentration as high as 1.25x1019 cm-3 at room temperature.

On curve fitting between topological indices and Gibb’s energy for semiconducting carbon nitrides network

Quantitative structure relationships linked to a chemical structure that shed light on its properties and chemical reactions are called topological indices. This structure is upset by the addition of silicon (Si) doping, which changes the electrical and optical characteristics. In this article, we examine the connection between a chemical structure’s Gibbs energy (GE) and K-Banhatti indices. In this article, we compute the K-Banhatti indices and then show the correlation between the indices and Gibb’s energy of the molecule using curve fitting. Through the curve fitting, we see that there is a strong correlation between indices and Gibb’s energy of a molecule. We use the polynomial curve fitting approach to see the correlation between indices and Gibb’s energy.

Challenges to extracting spatial information about double P dopants in Si from STM images

The design and implementation of dopant-based silicon nanoscale devices rely heavily on knowing precisely the locations of phosphorous dopants in their host crystal. One potential solution combines scanning tunneling microscopy (STM) imaging with atomistic tight-binding simulations to reverse-engineer dopant coordinates. This work shows that such an approach may not be straightforwardly extended to double-dopant systems. We find that the ground (quasi-molecular) state of a pair of coupled phosphorous dopants often cannot be fully explained by the linear combination of single-dopant ground states. Although the contributions from excited single-dopant states are relatively small, they can lead to ambiguity in determining individual dopant positions from a multi-dopant STM image. To overcome that, we exploit knowledge about dopant-pair wave functions and propose a simple yet effective scheme for finding double-dopant positions based on STM images.

Improved Dielectric Constant and Leakage Current of ZrO₂-Based Metal–Insulator–Metal Capacitors by Si Doping

Improved Dielectric Constant and Leakage Current of ZrO₂-Based Metal–Insulator–Metal Capacitors by Si Doping

Effects of Ar ion bombardment on the structure and properties of β-quartz

β-quartz is an important component that affects the physical and chemical properties of glass-ceramics. The material removal process of ion beam machining is complicated as one of the ultra-precision machining forms. Therefore, it is important to understand the removal mechanism of ion beam machining materials. The methods of molecular dynamics (MD) and first-principles were adopted to investigate the microscopic mechanism of ion beam bombardment of the β-quartz structure. The damage evolution of structures and the evolution of material properties caused by defects respectively from the atomic and electronic levels. Through MD analysis, we find that the random collision between incident ions and matrix atoms can lead to the formation of sputtered atoms. The incidence of ions will increase the disorder degree of the matrix, and the influence on the disorder degree at different depths of the matrix is different. The degree of disorder increases obviously in the range of 50–70 Å from the surface of the matrix. It has a significant impact on the surface topology of the matrix, the number of defects, surface roughness, and matrix density. The results of first-principle calculation show that the refraction, absorption and other characteristics of the system are significantly different with different doping forms, and the energy loss is most affected by substituted doping. And the substituted doping defects have the most significant effects on the structural energy loss. Among, the Ar-substituted O doping structure leads to higher energy loss, and the peak energy loss intensity reaches 5.146. In contrast, the Ar-substituted Si doping structure causes the least energy loss, the intensity is 2.543. This study provides a theoretical basis for the selection of parameters and the realization of ultra-smooth surface in actual ion beam machining.

Effect of reactive elements in MCrAlX bond coat for durability improvement of thermal barrier coatings

The effects of reactive elements (RE) in MCrAlX alloy (M: Metals, X: RE) as the bond coat for thermal barrier coatings durability were investigated by both experimental evaluation and density functional theory (DFT) calculations. Cyclic oxidation tests showed that the lifetime of the sample with Y, Hf, and Si as RE displayed approximately twice of the sample with Y only. Furthermore, the interface energies between oxide (α-Al2O3) and bond coat with various RE (Si, Sc, Ti, Y, Zr, Hf, La, and Ce) were calculated by DFT. DFT results indicate that Hf and Si doping effectively reduce the interface energy.

Investigation of mechanical behavior of porous carbon-based matrix by molecular dynamics simulation: Effects of Si doping

Understanding the mechanical properties of porous carbon-based materials can lead to advancements in various applications, including energy storage, filtration, and lightweight structural components. Also, investigating how silicon doping affects these materials can help optimize their mechanical properties, potentially improving strength, durability, and other performance metrics. This research investigated the effects of atomic doping (Si particle up to 10 %) on the mechanical properties of the porous carbon matrix using molecular dynamics methods. Young's modulus, ultimate strength, radial distribution function, interaction energy, mean square displacement and potential energy of designed samples were reported. MD outputs predict the Si doping process improved the mechanical performance of porous structures. Numerically, Young's modulus of the C-based porous matrix increased from 234.33 GPa to 363.82 GPa by 5 % Si inserted into a pristine porous sample. Also, the ultimate strength increases from 48.54 to 115.93 GPa with increasing Si doping from 1 % to 5 %. Silicon doping enhances the bonding strength and reduces defects in the carbon matrix, leading to improved stiffness and load-bearing capacity. This results in significant increases in mechanical performance. However, excess Si may disrupt the optimal bonding network, leading to weaker connections within the matrix. Also, considering the negative value of potential energy in different doping percentages, it can be concluded that the amount of doping added up to 10 % does not disturb the initial structure and stability of the system, and the structure still has structural stability. So, we expected our introduced atomic samples to be used in actual applications.

Recombination Activity of Crystal Defects in Epitaxially Grown Silicon Wafers for Highly Efficient Solar Cells

Aiming for highly efficient solar cells based on wafers with a low carbon footprint, silicon (Si) EpiWafers are grown epitaxially on reusable, highly doped Si substrates with a stack of porous Si layers (PorSi) for detachment. A state‐of‐the‐art p‐type Si EpiWafer exhibiting a minority charge carrier lifetime of up to 2.2 ms detected at an excess charge carrier density of ≈1 × 1015 cm−3 by photoluminescence (PL) imaging is presented. This translates to a predicted solar cell efficiency of 25.6%, calculated by efficiency limiting bulk recombination analysis (ELBA), and corresponds to losses of less than 1%abs compared to the theoretical limit of the investigated solar cell concept. A detailed loss analysis shows that the major remaining quality limitations are structural defects, specifically stacking faults (SFs). Therefore, the recombination activity of isolated SFs in epitaxially grown reference (EpiRef) wafers on polished substrates without a PorSi is assessed by highly resolved μPL mappings. The recombination activity rises with the number of dislocations within an SF as demonstrated by a comparison to microscope images. When using highly doped substrates, as currently required for EpiWafer fabrication, EpiRef wafers show more SFs exhibiting additionally a higher number of dislocations than SFs in EpiRef wafers on moderately doped substrates.

Extremely enhanced friction and wear performance of hydrogen-free DLC film at elevated temperatures via Si doping

Hydrogen-free diamond-like carbon (DLC) films have garnered significant attention as a highly efficient solid lubrication material, but poor high-temperature lubrication and wear resistance limit their further application. Here, silicon-doped DLC (Si-DLC) films with different Si contents were deposited using a superimposed HiPIMS-DCMS deposition system to improve their high-temperature lubrication and wear resistance performance. The influence of Si content on the microstructure, mechanical and high-temperature friction and wear behavior of Si-DLC films was investigated. The results showed that Si-DLC films had a dense structure and nanoscale smooth surface. The Si doping enhanced the adhesion strength and relieved the residual stress of Si-DLC films, but decreased the hardness and Young's modulus. Meanwhile, Raman and XPS spectroscopy revealed significant local structural changes in Si-doped DLC films. Furthermore, the results showed that DLC films doped with low Si content displayed excellent tribological performance at elevated temperatures due to the graphite lubricating layer on the surface of wear marks. Specifically, Si-DLC film with 3.31 at% Si had an ultra-low average friction coefficient of 0.04 at 450 °C and still provided effective lubrication at temperatures up to 500 °C. In contrast, pure DLC film failed to lubricate at 450 °C due to the severe graphitization transition and Si-DLC film with 17.47 at% Si quickly failed to lubricate at 200 °C due to the SiC and SiO2. This work sheds light for the high-temperature application of DLC films doped with low Si content by superimposed HiPIMS-DCMS deposition system.

Silicon-doped cobal–aluminum layered double hydroxide electrocatalyst with high catalytic activity for oxygen evolution reactions

Electrochemical water splitting is a zero-carbon-emission and environmentally friendly method for hydrogen production. However, the process requires electrocatalysts to lower its energy requirements. In this study, Si-doped cobalt–aluminum layered double hydroxide (Si-CoAl-LDH) had been successfully synthesized by SiCl4 chemical etching at room temperature. The Co-O-Si chemical bonds promoted the formation of γ-CoOOHx during the process of water oxidation, thereby increasing the number of active sites. Moreover, Theoretical calculations revealed the overlap of atomic orbitals on the Si-CoAl-LDH catalyst surface and the improved electronic structure due to Co–O–Si chemical bonds. The Si-CoAl-LDH exhibited overpotentials of 295, 336, and 363 mV for oxygen evolution reactions (OERs) at current densities 10, 50, and 100 mA cm−2, respectively. The Tafel slope of the sample was 74.16 mV·dec−1. Physical characterization and in situ Raman analysis revealed the formation of intermediate hydroxylated cobalt species, which act as active centers during OER. This study serves as a basis for the surface reconstruction and activity enhancement of other electrocatalysts through Si doping.