Quantitative modelling of nucleation kinetics in experiments for poly-Si growth on SiO2 by hot wire chemical vapor deposition
Abstract We apply a rate-equation pair binding model of nucleation kinetics to the nucleation of Si islands grown by hot wire chemical vapor deposition on SiO 2 substrates. The grain size of poly-Si films increases with H 2 dilution, which is attributed to atomic H etching of Si monomers rather than stable Si clusters during the early stages of nucleation. The nucleation density increases sublinearly with time at low coverage, implying a fast nucleation rate until a critical density is reached, after which grain growth begins. The nucleation density decreases with increasing H 2 dilution (H 2 :SiH 4 ) due to etching, and with increasing temperature, due to enhanced Si monomer diffusivity on SiO 2 . From temperature-dependent measurements, we estimate the activation energy for surface diffusion of Si monomers on SiO 2 to be 0.47±0.09 eV. Simulations of the temperature-dependent supercritical cluster density lead to an estimated activation energy of 0.42±0.01 eV and an estimated surface diffusion coefficient prefactor of 0.1±0.03 cm 2 /s.
Investigation of Volmer-Weber growth mode kinetics for germanium nanoparticles on hafnia
Germanium nanoparticle deposition kinetics were investigated on extended HfO2 surfaces and HfO2 confined within features etched into a 12.5nm SiO2 film. Electron beam lithography was used to pattern square features from 200nmto100μm in width. Hot wire chemical vapor deposition produced Ge nanoparticles on exposed HfO2 surfaces at 0.06–4.2ML∕min fluxes and 700–775K surface temperatures. Using mean-field nucleation descriptions of particle density versus flux and temperature, a noninteger critical cluster nuclei size between 0.27 and 0.4 was found, while the critical cluster formation activation energy of 0.4–0.6eV was estimated assuming a critical cluster size of zero for studies on extended, unpatterned HfO2. Restricting the HfO2 deposition area decreases nanoparticle density compared to the density found on extended surfaces. The density decrease is due to Ge desorption through adatom contact with the silica perimeter, which depletes the system of Ge adatoms that can undergo nucleation. Comparable activa...
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.