Engineering topics

Nikiforov, A. I.

Publications and source records attributed to Nikiforov, A. I..

3 records

DOE OSTI2018

Formation of a Stepped Si(100) Surface and Its Effect on the Growth of Ge Islands

The transition from a two-domain to one-domain surface on a Si(100) substrate is investigated. It is demonstrated using reflection high-energy electron diffraction that at a temperature of 600°C and a deposition rate of 0.652 Å/s onto a Si(100) substrate pre-heated to 1000°C and inclined at an angle of 0.35°C to the plane, a series of reflections from the 1 × 2 superstructure completely vanishes at a constant flow of Si. This is attributed to the transition of the surface from monoatomic to diatomic steps. At growth rates lower than 0.652 Å/s, the transition from a two-domain to one-domain surface is also observed; with a decrease in the growth rate, the intensity ratio I{sub 2×1}/I{sub 1×2} decreases and the maximum of the dependences shifts toward lower temperatures. The complete vanishing of the series of superstructural reflections after preliminary annealing at a temperature of 700°C is not observed; this series only vanishes after annealing at 900 and 1000°C. The growth of Ge islands on a Si(100) surface preliminary annealed at a temperature of 800°C is studied. It is shown that the islands tend to nucleate at the step edges. A mechanism of Ge island ordering on the Si(100) surface is proposed.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Valence-band offsets in strained SiGeSn/Si layers with different tin contents

Admittance spectroscopy is used to study hole states in Si{sub 0.7–y}Ge{sub 0.3}Sn{sub y}/Si quantum wells in the tin content range y = 0.04–0.1. It is found that the hole binding energy increases with tin content. The hole size-quantization energies in structures containing a pseudomorphic Si{sub 0.7–y}Ge{sub 0.3}Sn{sub y} layer in the Si matrix are determined using the 6-band kp method. The valence-band offset at the Si{sub 0.7–y}Ge{sub 0.3}Sn{sub y} heterointerface is determined by combining the numerical calculation results and experimental data. It is found that the dependence of the experimental values of the valence-band offsets between pseudomorphic Si{sub 0.7–y}Ge{sub 0.3}Sn{sub y} layers and Si on the tin content is described by the expression ΔE{sub V}{sup exp} = (0.21 ± 0.01) + (3.35 ± 7.8 × 10{sup –4})y eV.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Strained multilayer structures with pseudomorphic GeSiSn layers

The temperature and composition dependences of the critical thickness of the 2D–3D transition for a GeSiSn film on Si(100) have been studied. The regularities of the formation of multilayer structures with pseudomorphic GeSiSn layers directly on a Si substrate, without relaxed buffer layers, were investigated for the first time. The possibility of forming multilayer structures based on pseudomorphic GeSiSn layers has been shown and the lattice parameters have been determined using transmission electron microscopy. The grown structures demonstrate photoluminescence for Sn contents from 3.5 to 5% in GeSiSn layers.

36 MATERIALS SCIENCE↗