Structure and Thermal Conductivity of Thin Films of the Si $${}_{{1-x}}$$ Ge $${}_{{x}}$$ Alloy Formed by Electrochemical Deposition of Germanium into Porous Silicon

Abstract

Continuous and porous films of Si\({}_{1-x}\)Ge\({}_{x}\) alloys with a germanium content of about 40\(\%\) and a thickness of 3–4 \(\mu\)m formed on single-crystal silicon by electrochemical deposition into the porous silicon matrix with a subsequent rapid thermal annealing at a temperature of 950\({}^{\circ}\)C have been investigated by the Raman scattering spectroscopy and scanning electron microscopy methods. Based on the spectra in the Stokes and anti-Stokes frequency bands with the use of the Boltzmann statistics and the Fourier thermal conductivity law, the film thermal conductivity coefficients have been determined; their values are 7–9 and 3–6 W/(m K) for the continuous and porous films, respectively. The low thermal conductivity of the porous film is explained by an additional phonon scattering at a developed surface of pores. The possibility of application of such films in thermoelectric converters is provided by the simplicity and scalability of the procedure of alloy producing and its low thermal conductivity