Reaction paths and kinetics of aluminide formation in Al/epitaxial-W(001) model diffusion barrier systems
Single‐crystal bcc W(001) layers, 140 nm thick, were grown on MgO(001) substrates by ultrahigh‐vacuum (UHV) magnetron sputter deposition at Ts=600 °C. Al overlayers, 190 nm thick with strong (001) and (011) preferred orientation and an average grain size of 200 nm, were then deposited at Ts=100 °C without breaking vacuum. Changes in bilayer sheet resistance Rs were monitored continuously as a function of time ta and temperature Ta during UHV annealing. In addition, Rutherford backscattering spectroscopy, x‐ray diffraction, transmission electron microscopy (TEM), and scanning TEM, in which cross‐sectional specimens were analyzed by energy‐dispersive x‐ray analysis with a 1 nm resolution, were used to follow area‐averaged and local interfacial reaction paths as well as microstructural changes as a function of annealing conditions. The initial reaction products were discontinuous regions of monoclinic‐structure WAl4 which exhibit a crystallographic relationship with the underlying W layer. bcc WAl12 forms at...
Aluminide formation in polycrystalline Al/W metal/barrier thin-film bilayers: Reaction paths and kinetics
Polycrystalline bcc W layers, 110 nm thick with 011 preferred orientation and an average grain size of 40 nm, were grown on amorphous-SiO2/Si(001) substrates by ultrahigh vacuum (UHV) magnetron sputter deposition at Ts=600 °C. Al overlayers, 170 nm thick with strong 111 preferred orientation and an average grain size of 120 nm, were then deposited at Ts=100 °C without breaking vacuum. Changes in bilayer sheet resistance Rs were monitored continuously as a function of time ta and temperature Ta during UHV annealing. In addition, area-averaged and local interfacial reaction paths, as well as microstructural changes as a function of annealing conditions, were determined by x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy (TEM), and scanning TEM in which compositional distributions in cross-sectional specimens were obtained by energy-dispersive x-ray analysis using a 1 nm diam probe beam. The two tungsten aluminides which form, WAl4 and WAl12, are nucleated essential...
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.