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The behaviors of resistance, magnetoresistance (up to 5 T), and Hall electromotive force (EMF) with varying temperature (10-300 K) and measuring current ( [ABSTRACT FROM AUTHOR]

Formation of calcium silicide on three types of templates: Si(111)7 × 7, 2D Mg2Si, and 3D Mg2Si, was studied during Ca deposition at 120 °C in situ by Auger and electron energy loss spectroscopy, and by differential optical reflectance spectroscopy. A continuous Ca2Si layer is formed on 2D and 3D Mg2Si templates; but, on an atomically clean silicon surface (Si(111)7 × 7), a mixture of Ca2Si with another Ca silicide was found. The growth of a Si cap layer over the Ca silicide layers at about 100 °C studied by in situ methods demonstrated the full embedding of Ca silicide in amorphous silicon, independent of the used template. Transmission electron microscopy, Rutherford backscattering spectrometry, atomic force microscopy, and electrical characterization of Schottky junctions revealed the Ca2Si and Mg2Si nanoparticles and the redistribution of Mg and Ca during the silicon cap growth and its effect on the electronic properties of the structures. Reproduction of the experiments on higher doped and better purity substrates is needed to understand better the role of Mg- and Ca-related defects, and defects of silicon generated by the growth process. [ABSTRACT FROM AUTHOR]

The effect of pulsed ion-beam annealing on the surface morphology, structure, and composition of single-crystal Si(111) wafers implanted by chromium ions with a dose varying from 6 × 1015 to 6 × 1016 cm−2 and on subsequent growth of silicon is investigated for the first time. It is found that pulsed ion-beam annealing causes chromium atom redistribution in the surface layer of the silicon and precipitation of the polycrystalline chromium disilicide (CrSi2) phase. It is shown that the ultrahigh-vacuum cleaning of the silicon wafers at 850°C upon implantation and pulsed ion-beam annealing provides an atomically clean surface with a developed relief. The growth of silicon by molecular beam epitaxy generates oriented 3D silicon islands, which coalesce at a layer thickness of 100 nm and an implantation dose of 1016 cm−2. At higher implantation doses, the silicon layer grows polycrystalline. As follows from Raman scattering data and optical reflectance spectroscopy data, semiconducting CrSi2 precipitates arise inside the silicon substrate, which diffuse toward its surface during growth. [ABSTRACT FROM AUTHOR]

Low-energy electron diffraction and differential reflectance spectroscopy are used to study the self-formation of chromium disilicide (CrSi2) nanoislands on a Si(111) surface. The semiconductor properties of the islands show up even early in chromium deposition at a substrate temperature of 500°C, and the two-dimensional growth changes to the three-dimensional one when the thickness of the chromium layer exceeds 0.06 nm. The maximal density of the islands and their sizes are determined. The MBE growth of silicon over the CrSi2 nanoislands is investigated, an optimal growth temperature is determined, and 50-nm-thick atomically smooth silicon films are obtained. Ultraviolet photoelectron spectroscopy combined with the ion etching of the specimens with embedded nanocrystallites demonstrates the formation of the valence band, indicating the crystalline structure of the CrSi2. Multilayer epitaxial structures with embedded CrSi2 nanocrystallites are grown. [ABSTRACT FROM AUTHOR]

Spectral and integrated photoconductivities in chromium-disilicide epitaxial films grown on singlelayer silicon substrates have been studied in the photon energy range 0.5 - 1.6 eV. The region of the photoconductivity maximum observed at 1.23 eV corresponds to the third direct interband transition in chromium disilicide at 0.9 - 0.95 eV. Possible reasons for the weak photoconductivity signal in the region of the fundamental absorption edge are analyzed. [ABSTRACT FROM AUTHOR]

This article describes the development of an Si-based light-emitting diode with β-FeSi2 nanocrystals embedded in the active layer. Favorable epitaxial conditions allow us to obtain a direct band gap type-I band alignment Si/β-FeSi2 nanocrystals/Si heterostructure with optical transition at a wavelength range of 1500-1550 nm at room temperature. Transmission electron microscopy data reveal strained, defect-free β-FeSi2 nanocrystals of diameter 6 and 25 nm embedded in the Si matrix. Intense electroluminescence was observed at a pumping current density as low as 0.7A/cm². The device reached an optical emission power of up to 25 µW at 9A/cm² with an external quantum efficiency of 0.009%. Watt-Ampere characteristic linearity suggests that the optical power margin of the light-emitting diode has not been exhausted. Band structure calculations explain the luminescence as being mainly due to radiative recombination in the large β-FeSi2 nanocrystals resulting from the realization of an indirect-to-direct band gap electronic configuration transformation arising from a favorable deformation of nanocrystals. The direct band gap structure and the measured short decay time of the luminescence of several tens of ns give rise to a fast operation speed for the device. Thus a method for developing a silicon-based photonic integrated circuit, combining complementary metal-oxide-semiconductor technology functionality and near-infrared light emission, is reported here. [ABSTRACT FROM AUTHOR]

A thin iron film deposited at the rate of 10 nm/sec on the Si(001) surface and a sandwich structure silicon/iron/Si(111) are studied by Surface Magneto-Optic Kerr Effect, High Resolution Electron Microscopy and X-ray Photoelectron Microscopy methods. The phases present in the structures are identified. Both structures are non-uniform. The ultra-fast-deposited film is magnetically hard ( H=45 Oe), it contains the silicide FeSi. The XPS line shift by +0.55 eV with respect to the pure iron 2p 3/2 level is attributed to FeSi. The cross-section image of the sandwich structure shows the presence of enhanced-intermixing channels crossing the Si-rich layer. Iron atoms are the main diffusion species both at the Fe/Si(111) and Si/Fe interfaces. The nature of the volume defect and internal stresses in the transforming iron silicides and their effects on material intermixing and film growth process are discussed. [ABSTRACT FROM AUTHOR]

The initial stages of room-temperature Mg film growth of Si (111) were studied using low-energy electron diffraction, electron energy-loss spectroscopy, and differential reflectance spectroscopy. In the studied range of magnesium film thickness ( h = 0–0.2 nm), the formation of semiconductor magnesium silicide (Mg2Si), which is a promising material for silicon-silicide thermocouples, was detected. At small thicknesses of the deposited film, identical Mg2Si clusters are formed. An increase in the number of Mg atoms results in the formation of two-dimensional and then three-dimensional Mg2Si islands. Spectra of the optical response function δΛ″θ were measured for all structures; these spectra represent a characteristic of opticalproperties of these structures. [ABSTRACT FROM AUTHOR]

Schottky contacts on p-type silicon, with embedded arrays of β-FeSi2 nanocrystallites, were studied by current-voltage (I-V), deep level transient spectroscopy (DLTS), and low-frequency noise measurements. Forward I-V characteristics on logarithmic scale indicate that space-charge limited current (SCLC) dominates the carrier transport in these diodes. From an analysis of the SCLC characteristics, we found that two arrays of β-FeSi2 nanocrystallites induce a trap level at 320 meV above the valence band edge with concentration of 5×1014 cm-3, which is in relatively good agreement with the trap detected by DLTS. By inserting ten arrays of β-FeSi2 nanocrystallites, two trap levels at 300 and 340 meV with concentrations of 2.6×1014 and 1.1×1015 cm-3, respectively, were found from the SCLC analysis. By increasing the number of the inserted arrays of β-FeSi2 nanocrystallites from 2 to 10, a trap at 402 meV with concentration of 6.5×1015 cm-3 has been detected by DLTS, failing to detect the second trap observed by SCLC measurements. The normalized power spectral density SI/I2 vs V exhibits a peak at the transition voltage from the trap-filling regime to the SCLC regime, corresponding to a deep trap level. It is demonstrated that the noise technique is more sensitive than the SCLC and DLTS techniques in extracting information about the deep trap parameters. [ABSTRACT FROM AUTHOR]