Higher Manganese Silicide Films Research Articles

Electron microscopy characterization of higher manganese silicide film structure on silicon

The structure and composition of higher manganese silicide (HMS) films on Si(111) substrate are studied by high-resolution transmission electron microscopy, electron diffraction, and energy-dispersive X-ray spectroscopy. The formation of Mn4Si7 HMS film by the deposition of the gas-phase manganese onto silicon at 1040°C is observed. The film/substrate interface is semicoherent and does not contain any intermediate layer. The interface structure is refined by computer simulation. The orientation relationship \(\left( {\overline 1 \overline 2 4} \right)\left[ {443} \right]M{n_4}S{i_7}||\left( {1\overline 1 \overline 1 } \right)\left[ {001} \right]Si\) between the film and substrate is determined.

Enhancement of thermoelectric power factor bySi:Baddition to higher manganese silicide film

Higher manganese silicide film ( HMS , MnSix, x = 1.73–1.75) with addition of Si : B has been prepared on quartz substrate ( SiO2) by magnetron sputtering of MnSi2and Si : B (1 at.% B content) targets. It is found that the Si : B -added HMS film has a much lower electrical resistivity (R) but maintains its high Seebeck coefficient (S). As a result, the thermoelectric power factor, PF= S2/R, is greatly enhanced. It is also found that the metal In together with Ag -paste can be used as ohmic contact materials for measuring the electrical properties of the HMS film. The thermoelectric power factor can reach 1255 μW/m-K2at 733 K for the Si : B -added HMS film, which is about two times higher than that of the pure HMS film.

Highly Textured Mn15Si26 Film Obtained by High-Temperature Treatment

The growth of higher manganese silicide (HMS) films on monocrystalline silicon (100) has been investigated. This growth was performed by solid-state reaction. Using electron beam evaporation a single layer of manganese was deposited on a silicon substrate. The samples so prepared were heat treated in a classical furnace under vacuum. A highly textured film was obtained after treatment at 890°C for 18 h. The obtained HMS was identified as Mn15Si26. The texture relationship is (105) [100] Mn15Si26 ∥ (100) [100] Si. Mn15Si26 has a tetragonal cell; hence, the angle between the c-axis and the normal of the sample surface is 60°. Since this value is far from 0° and 90°, a large transverse thermoelectric effect is expected in these samples. As a consequence the HMS films could be used in anisotropic electromotive force-thermogenerators.

On the growth of higher manganese silicide films on silicon

The growth of manganese silicide films on silicon under the conditions of equilibrium and non-equilibrium diffusion doping of the silicon from the vapor phase is studied for different weight percent of the dopant.

CHARACTERIZATION OF p- AND n-TYPE MnSi1.7 FILMS BY AUGER ELECTRON SPECTROSCOPY

P- and n-type higher manganese silicide ( MnSi 1.7) films are characterized by Auger electron spectroscopy (AES). The relationship between Auger chemical shift and electrical property of the film has been established. Compared with pure Mn , the peak positions of Mn [MVV] Auger spectra in p- and n-type MnSi 1.7 films move to higher energy regions with +2.0 and +7.0 eV, respectively. New peaks around 50 eV in the Mn [MVV] Auger spectra, and 600, 654, and 705 eV in the Mn [LMM] Auger spectra appear in MnSi 1.7 films prepared by magnetron sputtering. These new peaks are considered to arise from iron impurities which are unintentionally introduced from the Mn–Si alloy target and during the magnetron sputtering process. The intensities of these new peaks are much stronger for the n-type MnSi 1.7 film. Compared with pure Si , the peak positions of Si [LVV] Auger spectra move to higher energy regions with +1.0 eV for both p- and n-type MnSi 1.7 films. However, the peak positions of Si [KLL] Auger spectra in p- and n-type MnSi 1.7 films move to lower energy regions with energy shifts between -1.0 and -3.0 eV.

Thermoelectric properties of higher manganese silicide films with addition of carbon

AbstractPolycrystalline higher manganese silicide (MnSi1.73, HMS) films with addition of carbon were prepared on thermally oxidized silicon substrates by magnetron sputtering. A carbon cap layer was used as the doping source. Both the Seebeck coefficient and the resistivity were strongly dependent on the amount of carbon added to the films. When the thickness ratio of carbon to manganese was about 17%, the Seebeck coefficient and resistivity at room temperature were about 35 μV/K and 4.45 × 10–3 Ω cm, respectively. By reducing the thickness ratio to about 3%, the Seebeck coefficient and resistivity at room temperature increased to 107 μV/K and 18 × 10–3 Ω cm, respectively. With addition of carbon, both the maximum value of the Seebeck coefficient and the temperature at which the maximum occurred increased. Several shallow (0.028–0.085 eV) and deep (0.106–0.299 eV) energy levels were observed from the curves of the resistivity versus temperature. The activation energies of 0.845 and 1.11 eV were consistent with the reported energy band gaps for higher manganese silicide. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of higher manganese silicide films on silicon

The formation of higher manganese silicide (HMS) films on silicon and the properties of the silicide-silicon interface are studied. Morphology analysis of the surface and thin transition layer at the HMS-Si interface suggests that the growth of HMS films by the method of Mn reactive diffusion follows the vapor-liquid-crystal mechanism.

On the Possibility of Developing Thermoelectric Sensors Based on Multielement Higher Manganese Silicide Film Structures

The possibility of designing thermoelectric sensors based on multielement structures of higher manganese silicide (HMS) polycrystalline films is considered. Test structures with various configurations are developed for studying electrical and thermoelectric parameters of polycrystalline HMS films. The geometrical sizes of the elements of test structures are chosen to match the grain size in polycrystalline HMS films. The test structures are prepared using the planar silicon technology. In these structures, the current-voltage characteristics, Hall constant, charge carrier concentration, and mobility are measured. The thermopower (α) and electrical conductivity (σ) are studied in a temperature range of T = 77–600 K, where α > 250 μV/K and electrical conductivity σ ∼ 20 (Ω cm)−1. It is shown that the sensitivity and thermopowers increase upon a decrease in the cross-sectional area of the elements.

The potential of higher manganese silicide as an optoelectronic thin film material

Every published study of higher manganese silicide (HMS) that has been concerned with its electronic band structure has affirmed its semiconducting nature. The results fall into two main camps: (1) it has a direct bandgap near 0.7 eV, or (2) it has an indirect gap near 0.4 eV. The difference is crucial because if the direct bandgap is correct, then HMS may be expected to have useful photoconductivity and luminescence efficiencies at important infrared wavelengths. This divergence of bandgap results for HMS may be due to fundamental structural variations, rather than experimental error: HMS is frequently referred to as “MnSi 1.7” and may be either a continuum of ordered phases or perhaps a group of several distinct compounds. Furthermore, there are reasonable prospects for growth of large-area single crystal HMS films on (001) silicon substrates—using template techniques and surfactant-mediated growth. HMS offers a rich field for furthering our understanding of epitaxy on silicon, and directed research should reveal whether we will have a new and useful thin film optoelectronic material.