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International audience; We have studied the stability of manganese germanide thin films grown on Ge(111) substrates by three different growth methods: solid phase epitaxy, reactive deposition epitaxy and co-deposition. By combining X-ray diffraction and magnetic measurements, we demonstrate that we can form either Mn5Ge3 or Mn11Ge8 thin films depending on the growth processes. In the case of solid phase epitaxy, we explain the phase formation sequence by taking into consideration the kinetic and thermodynamic processes involved. Tuning phase formation of the manganese germanide thin films was determined using in situ X-ray diffraction and the effect of the thin film thickness on the Mn5Ge3 thermal stability was investigated.

In this paper, we report investigations concerning the fabrication of a diluted Ge (Mn) solution using solid state Mn diffusion, and Mn/Ge reactive diffusion for spintronic applications. The study of Mn diffusion shows that the quasi-totality of the incorporated Mn atoms occupies Ge substitutional sites and probably exhibits two negative elementary charges. The solubility limit of Mn in Ge is comprised between 0.7 and 0.9 % (T  600 °C). We show that substitutional Mn atoms are not ferromagnetic in Ge and consequently that Ge (Mn) diluted magnetic semiconductor can not be produced. Beside the ferromagnetic signal from Mn5Ge3, ferromagnetic signals detected in the samples could be always attributed to surface or bulk Mn-Ge clusters. Furthermore, we show that the CMOS Salicide process is potentially applicable to Mn5Ge3 nanolayer fabrication on Ge for spintronic applications. During Mn (thin-film)/Ge reaction, Mn5Ge3 is the first phase to form, being thermally stable up to 310 °C and exhibiting ferromagnetic properties up to TC ~ 300 K.

In situ experiments based on X-ray diffraction, sheet resistance and differential scanning calorimetry were performed on Pt thin films deposited on Si either undoped or doped with As (n type) or B (p type). In all cases, these measurements show a sequential formation of Pt 2 Si followed by PtSi phases. Simulations of the kinetics show that the growth is controlled by both the interface and the diffusion through the growing silicide. A slowdown of the formation of Pt 2 Si has been observed at the end of Pt consumption; this might be due to the accumulation of impurities in the Pt film. The in situ measurements show a delay between the end of the growth of Pt 2 Si and the formation of PtSi that is related to the strain relaxation in Pt 2 Si: i.e. the growth of PtSi starts when most of the strain in Pt 2 Si is relaxed. Anisotropy in the magnitude of strain value and gradient was found for two grain orientations of Pt 2 Si. The dopants (B and As) do not significantly influence the silicide formation properties (phase sequence, strain and sheet resistance). Boron addition has almost no influence on the formation kinetics while Arsenic slightly slows it down. The sheet resistance of Pt 2 Si is lower than that of PtSi, which remains stable until 800 °C.