Excimer laser annealing ͑ELA͒ of ultra-low-energy ͑ULE͒ B-ion implanted Si has been performed. Highresolution transmission electron microscopy has been used to assess the as-implanted damage and the crystal recovery following ELA. The electrical activation and redistribution of B in Si during ELA has been investigated as a function of the laser energy density ͑melted depth͒, the implant dose, and the number of laser pulses ͑melt time͒. The activated and retained dose has been evaluated with spreading resistance profiling and secondary ion mass spectrometry. A significant amount of the implanted dopant was lost from the sample during ELA. However, the dopant that was retained in crystal material was fully activated following rapid resolidification. At an atomic concentration below the thermodynamic limit, the activation efficiency ͑dose activated/ dose implanted into Si material͒ was a constant for a fixed melt depth, irrespective of the dose implanted and hence the total activated dose was raised as the implant dose was increased. The electrical activation was increased for high laser energy density annealing when the dopant was redistributed over a deeper range.
The diffusion and activation of arsenic implanted into germanium at 40 keV with maximum concentrations below and above the solid solubility (8 x 10(19) cm(-3)) have been studied, both experimentally and theoretically, after excimer laser annealing (lambda = 308 nm) in the melting regime with different laser energy densities and single or multiple pulses. Arsenic is observed to diffuse similarly for different fluences with no out-diffusion and no formation of pile-up at the maximum melt depth. The diffusion profiles have been satisfactorily simulated by assuming two diffusivity states of As in the molten Ge and a non-equilibrium segregation at the maximum melt depth. The electrical activation is partial and decreases with increasing the chemical concentration with a saturation of the active concentration at 1 x 10(20) cm(-3), which represents a new record for the As-doped Ge system
Chemical vapor deposition in the low pressure regime of a high quality 3C-SiC film on silicon ͑100͒-oriented substrates was carried out using silane ͑SiH 4 ͒, propane ͑C 3 H 8 ͒, and hydrogen ͑H 2 ͒ as the silicon supply, carbon supply, and gas carrier, respectively. The resulting bow in the freestanding cantilever structures was evaluated by an optical profilometer, and the residual gradient stress ͑ 1 ͒ in the films was calculated to be approximately between 15 and 20 MPa, which is significantly lower than the previously reported 3C-SiC on Si films. Finite element simulations of the stress field in the cantilever have been carried out to separate the uniform contribution ͑ 0 ͒, related to the SiC/Si interface, from the gradient one ͑ 1 ͒, related to the defects present in the SiC epilayer.There is an increasing demand for sensors that can operate at temperatures well above 300°C and in severe environments such as automotive and aerospace applications. In particular, combustion process and gas turbine control have stimulated the search for alternatives to silicon. Silicon carbide ͑SiC͒ is a material that has attracted much attention for a long time, particularly due to its wide bandgap, its ability to operate at high temperatures, its mechanical strength, and its inertness to exposure in corrosive environments. However, the difficulty in growing high quality crystalline material and processing electronic devices has limited its use to very specific application areas, such as high temperature, high power, and high frequency applications that are not suitable for Si-based devices. For other applications, and particularly for SiC-microelectromechanical systems ͑MEMS͒ devices, large-area substrates are essential. 1 The cubic polytype, namely, 3C-SiC but also known as -SiC, is the only polytype with a cubic crystal structure which crystallizes in a ZnS lattice structure and hence it can be deposited on silicon substrates. This allows the growth of cubic silicon carbide layers on large-area silicon substrates and paves the way for this suitable and important material to be applied to MEMS or nanoelectromechanical systems. 2 The use of large-area substrates offers the possibility for economical and low cost batch processing, which makes SiC more attractive for sensors and device applications. The heteroepitaxy of SiC on Si substrates results in the heterostructure 3C-SiC/Si, which is a very interesting material system for MEMS and nanoelectromechanical systems.With respect to the mechanical properties of the silicon carbide films for use in sensors or freestanding MEMS structures, one important issue is the residual stress field, which is normally created during the growth process and which can result in the unwanted deformation or failure of these structures. Stress varies from point to point within the crystal lattice, altering the lattice spacing and consequently changing the properties of the material.For example, the built-in stress may change the mechanical response, the resonant frequency of the thin-film struc...
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