Papers by Author: Jean François Barbot

Abstract: In order to form Ti₃SiC₂ on 4H-SiC(0001) 8°-off, 200 nm of Ti₃₀Al₇₀ was deposited onto SiC substrates by magnetron sputtering from pure Ti₃₀Al₇₀ targets. The samples were then annealed at 1000°C for 10 min under Ar atmosphere in a Rapid Thermal Annealing (RTA) furnace. Structural analyses reveal the formation of epitaxial hexagonal Ti₃SiC₂ (0001) oriented. Elemental analyses show that high amount of Al and O elements are present inside the deposit. Obviously, the formation of Ti₃SiC₂ is accompanied by parasitic Al oxide, probably due to some unwanted oxygen residual in the RTA chamber. By using proper backing steps before the annealing, the deposit is not anymore composed of only Ti₃SiC₂ but accompanied with other compounds (Al₃Ti, and Al). On the oxide-free sample, the specific contact resistance ρ_c of the Ti₃SiC₂ based contact on p-type 4H-SiC (having N_a= 2×10¹⁹ cm^-3) was measured to be as low as 6×10^-5 Ω.cm².

Abstract: In this study, investigations on MAX phase Ti3SiC2 formation to n-type 4H-SiC substrates and its ohmic-behaved are reported. Ti-Al layers were deposited onto SiC substrates at room temperature by magnetron sputtering in high vacuum system. Thermal annealing at 1000°C in Ar atmosphere were performed to allow interdiffusion processes. X-ray diffraction and High Resolution Transmission Electron Microscopy reveal that a Ti3SiC2 contact, in perfect epitaxy with 4H-SiC substrate, is so-obtained. In situ annealing experiment underlines the evolution of Ti-Al contact microstructure versus temperature. The evolution of contact system from Schottky to Ohmic behaved is observed by I-V measurements for annealing temperatures larger than 700°C.

Abstract: Ion implantation into 4H-SiC induces a local gradient of strain which increases with the nuclear energy losses. With the increase of temperature the strain tends to become uniform in the whole implanted area requiring the migration of particles. In case of helium implantation, defects are more stabilized and their evolutions observed post thermal annealing are concomitant with the surface swelling. The local modifications imputed to the ion process lead to the formation and the pile-up of stacking faults in the highly damaged region.

Abstract: The evolution of the normal strain induced by nitrogen implantation in 4H-SiC was investigated through X-ray diffraction measurements and compared to previous studies on helium implanted SiC. The shape of the normal strain profile in the near surface region shows that the accumulation of point defects is not the only mechanism operative at room temperature. In the highly damaged region, the normal strain profile fits the N concentration.

Abstract: The evolution of mechanical properties of helium-implanted 4H-SiC at room temperature has been mainly studied by nanoindentation tests. The curves of hardness and elastic modulus present a maximum at low levels of damage while a degradation of the mechanical properties is observed for high levels of damage. However, when the concentration of implanted ions exceeds 0.5 %, complex defects (helium-vacancy defects) become predominant which results in the increase of both the hardness and the modulus. Under high fluence of helium implantation tiny bubbles form and the amorphous transition is observed above a critical level of damage.

Abstract: In this study, Co germanide Schottky barrier diodes on n-Ge (100) substrate were fabricated by sputtering metal Co on Ge, followed by annealing in vacuum at 700°C. The influence of annealing time was investigated on both the electrical properties of Co germanide Schottky barrier diodes and on the phase formation on n-Ge (100) substrate. With increasing annealing times growing or transformation of germanide entities occurs leading to reduction of the trap concentration and therefore the leakage current.

Abstract: (001) n-type Ge has been implanted at given fluence and intermediate temperature with hydrogen ions using two processes: conventional in-line implantation and plasma based ion implantation. The as-created microstructure has been compared using transmission electron microscopy. In particular, it has been shown that the major differences observed are due to the implantation temperature, much higher during the PBII process. This suggests that plasma based ion implantation could be used for layer transfer in spite of a higher surface roughness observed after the PBII process.

Abstract: Single crystals SiC were implanted with 50 keV helium ions at room temperature and fluences in the range 1x1016 -1x1017 cm-2. The helium implantation induced swelling was studied through the measurement of the step height. The damage was studied by using X-ray diffraction measurements and the transmission electron microscopy observations. Degradation of mechanical properties is found after helium implantation.

Abstract: Different group IV impurities (Pb, C, and Sn) have been introduced in the melt during the growth of n-type Czochralski silicon. The samples have been irradiated with 1 MeV electrons to a fluence of 4x1015cm-2. The irradiation-induced defects have been studied by Deep Level Transient Spectroscopy (DLTS). It is shown that the formation of one of the irradiation-induced deep level is avoided by the Pb-doping. This level is located at 0.37 eV from the conduction band edge (EC) and shows an apparent capture cross-section of 7x10-15cm2. In addition, another irradiation induced deep level located at EC - 0.32 eV has been studied in more details.

Abstract: In the present work, we report on the effects of the implantation temperature on the formation of bubbles and extended defects in Ne+-implanted Si(001) substrates. The implantations were performed at 50 keV to a fluence of 5x1016 cm-2, for distinct implantation temperatures within the 250°C≤Ti≤800°C interval. The samples are investigated using a combination of cross-sectional and plan-view Transmission Electron Microscopy (TEM) observations and Grazing Incidence Small-Angle X-ray Scattering (GISAXS)measurements. In comparison with similar He implants, we demonstrate that the Ne implants can lead to the formation of a much denser bubble system.