Spectroscopic Analysis of Rare-Earth Silicide Structures on the Si(111) Surface

Two-dimensional rare-earth silicide layers deposited on silicon substrates have been intensively investigated in the last decade, as they can be exploited both as Ohmic contacts or as photodetectors, depending on the substrate doping. In this study, we characterize rare-earth silicide layers on the Si(111) surface by a spectroscopic analysis. In detail, we combine Raman and reflectance anisotropy spectroscopy (RAS) with first-principles calculations in the framework of the density functional theory. RAS suggests a weakly isotropic surface, and Raman spectroscopy reveals the presence of surface localized phonons. Atomistic calculations allow to assign the detected Raman peaks to phonon modes localized at the silicide layer. The good agreement between the calculations and the measurements provides a strong argument for the employed structural model.

Resistance to Molten Superalloy at 1550 °C for Molybdenum Metal Core with a Silica/Silicide Coating

This work designs a silica (SiO2) layer on a molybdenum metal core to provide new insights on the corrosion resistance of the silica/silicide coating in the Ni-based superalloy. The molybdenum substrate coated with MoSi2 by pack cementation was pre-oxidized to fabricate a cristobalite scale on the surface and the preoxidation specimens were chosen to examine the corrosion-resistant property by using a DSM11 superalloy at 1550 °C. In order to prepare a cristobalite layer, the microstructure evolution of a 40- µm MoSi2 coating with the different oxidation parameters (temperature and time) was investigated. After casting test, the different casting results showed that the silicide layer was dissolved in the molten superalloy. However, the molybdenum matrix was found to be protected by the cristobalite layer, as well as accompanied by the cristobalite layer partially destroyed at the core/superalloy interfaces. Furthermore, the reason for the destruction of cristobalite layer was analyzed. The failure mechanism of the cristobalite layer was proposed during the cast process.

Synthesis and electrochemical performance of silicon-nanowire alloy anodes

Electroless coating of a silicon nanowires (SiNW) anode (a) followed by annealing, forms nickel silicide layer (b), which enables stable electrochemical behaviour of SiNi-alloy anode and higher capacity retention compared to the pristine SiNW anode (c).

METHOD OF IONIC MIXING FOR SILICIDE LAYER FORMATION

Ионная имплантация ионами отдачи или ионное перемешивание, основанное на внедрении требуемой примеси из поверхностных слоев при передаче им кинетической энергии первичного пучка, имеют большие перспективы для получения структур и соединений с заданными свойствами. В процессе масштабирования сверхбольших интегральных схем паразитное сопротивление межсодинений и неомический характер контактов являются ограничивающими факторами. Перспективными материалами для использования в системах металлизации являются силициды тугоплавких металлов. В работе проведено исследование по внедрению ионов фосфора в систему молибден-кремний. Полученные результаты демонстрируют возможность формирования силицида молибдена при пониженной температуре, применением имплантации ионов, вызывающих ионное перемешивание. Разработанная технология позволяет достичь однородной границы раздела силицида с кремнием, и необходимые электрофизические характеристики метализации и омических контактов. Из-за заглубления границы раздела в объем полупроводника снижается влияние состояния поверхности кремния на параметры омических контактов, в результате обеспечивается их необходимая стабильность и воспроизводимость. Ion implantation with recoil ions or ion mixing based on the introduction of the required impurity from the surface layers during the transfer of the kinetic energy of the primary beam to them have great prospects for obtaining structures and compounds with desired properties. In the process of ranging of very large scale integrated circuits, the parasitic resistance of interconnections and the nonohmic nature of contacts are the limiting factors. Refractory metal silicides are promising materials for use in metallization systems. In this work a study was carried out on the introduction of phosphorus ions into molybdenum-silicon systems. The results obtained demonstrate the possibility of the molybdenum silicide formation at a low temperature using implantation of ions that cause ionic mixing. The developed technology makes it possible to achieve a homogeneous interface between the silicide and silicon with the necessary electrophysical characteristics of metalization and ohmic contacts. Due to the deepening of the interface into the bulk of the semiconductor, the effect of the silicon surface state on parameters of ohmic contacts decreases. As a result their necessary stability and reproducibility are ensured.

Microstructure and Composition Evolution of a Fused Slurry Silicide Coating on MoNbTaTiW Refractory High-Entropy Alloy in High-Temperature Oxidation Environment

In this paper, the Si-20Cr-20Fe coating was prepared on MoNbTaTiW RHEA by a fused slurry method. The microstructural evolution and compositions of the silicide coating under high-temperature oxidation environment were studied. The results show that the silicide coating could effectively prevent the oxidation of the MoNbTaTiW RHEA. The initial silicide coating had a double-layer structure: a high silicon content layer mainly composed of MSi2 as the outer layer and a low silicon content layer mainly contained M5Si3 as the inner layer. Under high-temperature oxidation conditions, the silicon element diffused from the silicide coating to the RHEA substrate while the oxidation of the coating occurred. After oxidation, the coating was composed of an outer oxide layer and an inner silicide layer. The silicide layer moved toward the inside of the substrate, led to the increase of its thickness. Compared with the initial silicified layer, its structure did not change significantly. The structure and compositions of the oxide layer on the outer surface strongly depended on the oxidation temperature. This paper provides a strategy for protecting RHEAs from oxidation at high-temperature environments.

Microstructure and Composition Evolution of a Fused Slurry Silicide Coating on MoNbTaTiW Refractory High-entropy Alloy in High-temperature Oxidation Environment

The poor oxidation resistance of refractory high-entropy alloys (RHEAs) is a major obstacle for their use in high-temperature engineering applications. Anti-oxidation coating technology is an effective method for improving the oxidation resistance. In this paper, the Si-20Cr-20Fe coating was prepared on MoNbTaTiW RHEA by a fused slurry method. The microstructural evolution and compositions of the silicide coating under high-temperature oxidation environment were studied. The results show that the silicide coating could effectively prevent the oxidation of the MoNbTaTiW RHEA. The initial silicide coating had a double-layer structure; a high silicon-content layer mainly composed of MSi2 as the outer layer and a low silicon-content layer mainly contained M5Si3 as the inner layer. Under high-temperature oxidation conditions, the silicon element diffused from the silicide coating to the RHEA substrate while the oxidation of the coating occurred. After oxidation, the coating was composed of an outer oxide layer and an inner silicide layer. The silicide layer moved toward the inside of the substrate, led to the increase of its thickness. Compared with the initial silicified layer, its structure did not change significantly. The structure and compositions of the oxide layer on the outer surface strongly depended on the oxidation temperature. This paper provides a strategy for protecting RHEAs from oxidation at high-temperature environments.

Experimental study silicon low-dimensional structures for generation of THz radiation

Capabilities of precision technologies for manufacturing on SOI wafers of silicon low-dimensional structures for terahertz generation are investigated. The design of diode device based on array of silicon nanowires or on ultrathin (<10 nm) silicon layer are proposed. This generating silicon diode includes nano-sized elements with ballistic transport of carriers, which is coupled to a metal antenna made from silicide layer.

Thickness-Dependent Structural and Magnetic Study of Co/Si/Co Trilayers Grown by Ion Beam Sputtering

The magnetic properties of the metal/semiconductor structure can be modulated by the semiconductor layer thickness and therefore in the present paper, a series of trilayers of ion beam sputtered Cobalt–Silicon–Cobalt (Co/Si/Co) were grown to study the interface characteristics and their connections with magnetic properties. The thickness of Co layer, [Formula: see text], is fixed to 3[Formula: see text]nm, while varying the thickness of Si sandwich layer, [Formula: see text], from 1.5[Formula: see text]nm to 4[Formula: see text]nm, respectively. Grazing incidence X-ray diffraction (GIXRD), grazing incidence X-ray reflectivity (GIXRR), Atomic Force Microscopy (AFM) and Magneto-Optic Kerr Effect (MOKE) techniques were employed to study the crystal structure, surface and interface structure, morphology and magnetic characteristics of thin films. X-ray reflectivity measurements show substantial intermixing between the layers leading to trilayers of complicated structure at the interface during deposition. At [Formula: see text][Formula: see text]nm, whole Si layer is converted into silicide, whereas at higher spacer layer thickness ([Formula: see text]), in addition to silicide layer, an unreacted elemental layer of Si also remains in the spacer. A magneto-optical measurement reveals the presence of anti-ferromagnetic coupling in these samples and the strength of coupling between Co layers is found to be depended on [Formula: see text].