R. M. Bayazitov

Structure and photoluminescent properties of SiC layers on Si, synthesized by pulsed ion-beam treatment

Abstract We report the formation of the continuous β-SiC layers on Si by means of C + implantation into Si followed by pulsed ion-beam treatment (C + , 300 keV, 50 ns). Transmission electron microscopy and electron diffraction indicate the formation of a polycrystalline β-SiC layers with a grain size of up to 100 nm. Porous SiC/Si structures were prepared by anodization and were studied by photoluminescence (PL) at room temperature. Three PL bands were observed at 460, 520 and 615 nm and were ascribed to the SiC nanocrystals, C-rich clusters and Si nanocrystals, respectively. The time constant τ =40 ns was deduced from time-resolved PL measurements. It is close to the value for direct band gap semiconductors and is shorter nearly by 3 orders of magnitude than that for porous Si.

Formation of Cubic Silicon Carbide Layers on Silicon under the Action of Continuous and Pulsed Carbon Ion Beams

The structure and infrared absorption of cubic silicon carbide (β-SiC) layers produced by the continuous high-dose implantation of carbon ions (C+) into silicon (E=40 keV and D=5×1017 cm−2), followed by the processing of the implanted layers with a high-power nanosecond pulsed ion beam (C+, τ=50 ns, E=300 keV, and W=1.0–1.5 J/cm2), are investigated. Transmission electron microscopy and electron diffraction data indicate the formation of a coarse-grained polycrystalline β-SiC layer with grain sizes of up to 100 nm. A characteristic feature of such a layer is the dendritic surface morphology, which is explained by crystallization from the melt supercooled well below the melting point of β-SiC.

Influence of Cr+ ion implantation and pulsed ion-beam annealing on the formation and optical properties of Si/CrSi2/Si(111) heterostructures

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.

Pulsed ion beam formation of highly doped GaAs layers

Abstract The formation of heavily doped n-GaAs layers using continuous ion implantation and subsequent treatment by powerful pulsed ion beams has been investigated. Using Auger electron spectroscopy (AES), electrical measurements and computer simulations, correlation between donor distributions and electrical activation was established. It is shown that the n+-GaAs layers (n=1019–1020 cm−3) are formed in the deep tail of the impurity atom distributions. Thermal stability of formed supersaturated layers was investigated.

Fabrication of composite based on GeSi with Ag nanoparticles using ion implantation

Comparative analysis of the structural and optical properties of composite layers fabricated with the aid of implantation of single-crystalline silicon (c-Si) using Ge+ (40 keV/1 × 1017 ions/cm2) and Ag+ (30 keV/1.5 × 1017 ions/cm2) ions and sequential irradiation using Ge+ and Ag+ ions is presented. The implantation of the Ge+ ions leads to the formation of Ge: Si fine-grain amorphous surface layer with a thickness of 60 nm and a grain size of 20–40 nm. The implantation of c-Si using Ag+ ions results in the formation of submicron porous amorphous a-Si structure with a thickness of about 50 nm containing ion-synthesized Ag nanoparticles. The penetration of the Ag+ ions in the Ge: Si layer stimulates the formation of pores with Ag nanoparticles with more uniform size distribution. The reflection spectra of the implanted Ag: Si and Ag: GeSi layers exhibit a sharp decrease in the intensity in the UV (220–420 nm) spectral interval relative to the intensity of c-Si by more than 50% owing to the amorphization and structuring of surface. The formation of Ag nanoparticles in the implanted layers gives rise to a selective band of the plasmon resonance at a wavelength of about 820 nm in the optical spectra. Technological methods for fabrication of a composite based on GeSi with Ag nanoparticles are demonstrated in practice.

Pulsed modification of germanium films on silicon, sapphire, and quartz substrates: Structure and optical properties

The structural and optical properties of thin Ge films deposited onto semiconducting and insulating substrates and modified by pulsed laser radiation are studied. The films are deposited by the sputtering of a Ge target with a low-energy Xe+ ion beam. Crystallization of the films is conducted by their exposure to nanosecond ruby laser radiation pulses (λ = 0.694 μm) with the energy density W = 0.2−1.4 J cm−2. During pulsed laser treatment, the irradiated area is probed with quasi-cw (quasi-continuous-wave) laser radiation (λ = 0.532 and 1.064 μm), with the reflectance recorded R(t). Experimental data on the lifetime of the Ge melt are compared with the results of calculation, and good agreement between them is demonstrated. Through the use of a number of techniques, the dependences of the composition of the films, their crystal structure, the level of strains, and the reflectance and transmittance on the conditions of deposition and annealing are established.

Optical diagnostics of the laser-induced phase transformations in thin germanium films on silicon, sapphire, and fused silica

The in-situ procedure is used to study the modification of thin (200–600 nm) germanium films induced by nanosecond pulses of a ruby laser. The films are produced using the ion-beam or magnetron sputtering on single-crystalline silicon (Si), sapphire (Al2O3), and fused silica (α-SiO2) substrates. The results on the dynamics of the laser-induced processes are obtained using the optical probing of the irradiated region at wavelengths of λ = 0.53 and 1.06 μm. The results of probing make it possible to determine the threshold laser energy densities that correspond to the Ge and Si melting and the generation of the Ge ablation plasma versus the amount of deposited Ge and thermophysical parameters of the substrate. The reflection oscillograms are used to obtain the dependences of the melt lifetime on the laser-pulse energy density.

Epitaxial growth of silicon on silicon implanted with iron ions and optical properties of resulting structures

The method of ultrahigh-vacuum low-temperature (T = 850°C) purification of silicon single crystals having the (100) and (111) orientation and implanted with low-energy (E = 40 keV) iron ions with various doses (Φ = 1015−1.8×1017 cm−2) and subjected to pulsed ion treatment (PIT) in a silicon atom flow has been tested successfully. The formation of semiconducting iron disilicide (β-FeSi2) near the surface after PIT is confirmed for a Si(100) sample implanted with the highest dose of iron ions. The possibility of obtaining atomically smooth and reconstructed silicon surfaces is demonstrated. Smooth epitaxial silicon films with a roughness on the order of 1 nm and a thickness of up to 1.7 μm are grown on samples with an implantation dose of up to 1016 cm−2. Optical properties of the samples before and after the growth of silicon layers are studied; the results indicate high quality of the grown layers and the absence of iron disilicide on their surface.

Pulsed nanosecond annealing of magnesium-implanted silicon

Single-crystalline silicon is implanted by magnesium ions at room temperature and then subjected to pulsed ion-beam annealing. The surface morphology, crystallinity, and optical properties of the implanted silicon are studied before and after annealing. It is shown that ion implantation makes a near-surface layer of silicon about 0.1 m thick amorphous. Pulsed nanosecond ion-beam annealing results in silicon recrystallization and the formation of crystalline magnesium silicide precipitates. Optimal values of the implantation dose and pulse energy density for the formation of magnesium silicide precipitates in the near-surface layer of silicon are found.

Anisotropic local melting of semiconductors under light pulse irradiation

This paper summarizes the careful investigation of the mechanism and basic regularities of anisotropic local melting of semiconductors subjected to light-pulse irradiation. The dependences of the density, sizes, and shapes of local motion regions on the intensity and duration of light pulses, the type of monocrystalline substrate, as well as the regime of preliminary implantation and ion type are established. The model of superheating in solid phase is used to explain the experimental results. It is shown that the main centers for liquid nuclei formation are the surface defects available before the light irradiation. The influence of the thermoplastic effects caused by both the light pulse itself and the tetrahedral covalent radius of implanted impurity is shown.