C-doped Films Research Articles

Impact of annealing temperature and carbon doping on the wetting and surface morphology of semiconducting iron disilicide formed via radio frequency magnetron sputtering

Iron disilicide (FeSi2) films were formed onto Si(111) substrates via radio-frequency magnetron sputtering at room temperature (RT) and 560 °C. The effects of annealing temperature and carbon (C) doping concentration on the physical properties of FeSi2 films were investigated. For annealing conditions, the crystallinity of the unannealed FeSi2 films was enhanced after annealing. The surface of unannealed FeSi2 films consisted of many small crystallites, which were clustered after annealing at 500 °C. The root mean square roughness (Rrms) of the unannealed FeSi2 films increased from 0.94 nm to 5.32 nm after air-annealing at 500 °C. The surface of the unannealed FeSi2 films exhibited an average contact angle (θCA) of 102.35°, which decreased to 41.70° after annealing at 500 °C. For C-doping conditions, the X-ray diffraction patterns for the undoped and C-doped FeSi2 revealed β(202/220) and β(404/440) peaks. The undoped FeSi2 film surfaces presented many small grains with grain boundaries, where the C-doped FeSi2 films displayed a finer surface. Rrms of the undoped FeSi2 film surface was 15.71 nm, which decreased to 10.59 nm for 3.0 at.% C-doped FeSi2 films. The average θCA of the undoped FeSi2 films was 108.35°, and this reduced slightly to 103.65° for 3.0 at.% C-doped films. Based on the obtained results, it was shown that the as-formed FeSi2 and FeSi2 films after annealing at 100 and 300 °C formed at Tsub of RT, together with the undoped and C-doped FeSi2 films formed at Tsub of 560 °C, could potentially be employed for hydrophobic coating applications.

Thermal conductivity of carbon doped GeTe thin films in amorphous and crystalline state measured by modulated photo thermal radiometry

The thermal conductivity and thermal boundary resistance of GeTe and carbon doped GeTe thin films, designed for phase change memory (PCM) applications, were investigated by modulated photo thermal radiometry. It was found that C doping has no significant effect on the thermal conductivity of these chalcogenides in amorphous state. The thermal boundary resistance between the amorphous films and SiO2 substrate is also not affected by C doping. The films were then crystallized by an annealing at 450°C as confirmed by optical reflectivity analysis. The thermal conductivity of non-doped GeTe significantly increases after crystallization annealing. But, surprisingly the thermal conductivity of the crystallized C doped GeTe was found to be similar from that of the amorphous state and independent of C concentration. As for the amorphous phase, C doping does not affect the thermal boundary resistance between the crystalline GeTe films and SiO2 substrate. This behaviour is discussed thanks to XRD and FTIR analysis. In particular, XRD shows a decrease of crystalline grain size in crystalline films as C concentration is increased. FTIR analysis of the film before and after crystallization evidenced that this evolution could be attributed to the disappearing of Ge-C bonds and migration of C atoms out of the GeTe phase upon crystallization, limiting then the growth of GeTe crystallites in C-doped films.

Carbon-doped In 2O 3 films for photoelectrochemical hydrogen production

Carbon-doped In 2O 3 films were synthesized by spray pyrolysis and evaluated for photoelectrocatalysis. All C-doped films showed cubic structure, and XPS confirmed carbon's presence and content. 13C SSNMR showed the presence of carbonate-type species. C-doped In 2O 3, compared to undoped, showed increased absorption in the 350–500 nm range with a red shift in the band gap transition. The photoactivity was evaluated under near-UV and visible light irradiation. The C-doped films exhibited photocurrent densities up to 1 mA/cm 2, with a high contribution (40%) from visible light irradiation. Under the same irradiation conditions, C-doped In 2O 3 produced much greater photocurrent densities than the undoped films. Photocurrent densities of the C-doped films were determined as a function of the dopant source, its concentration, and film thickness. These results indicate the potential for further development of In 2O 3 photocatalysts, and provide useful information towards understanding the structure and enhanced photoelectrochemical properties of these new materials.

A comparative study on microstructures of β-FeSi 2 and carbon-doped β-Fe(Si,C) 2 films by transmission electron microscopy

The microstructures of β-FeSi 2 and carbon-doped β-Fe(C,Si) 2 films, synthesized on Si substrates by metal vapor vacuum arc ion source ion implantor, are studied by transmission electron microscopy. Structure evolution at different annealing temperatures shows that, in comparison with undoped films, the C-doped film quality is improved as manifested by smooth β/Si interface, homogeneous film thickness, fine grains, and high thermal stability. When the energy and dosage are 60 KV and 4×10 17 ions/cm 2, amorphous layer is formed directly, which transforms into homogeneous and smooth β-FeSi 2 surface films after crystallization.