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...
Solid-phase reactions and the order-disorder phase transition in thin films
A comparative analysis was carried out of the initiation temperatures of solid-phase reactions in bilayer solid films and the Kurnakov temperatures of the phases forming in the reaction products. It has been shown that in superstructures where ordering is usually observed, the Kurnakov temperature coincides with the initiation temperature of the solid-phase reactions if no other solid-phase structural transformation precedes the order-disorder phase transition in the state diagram. A rule was proposed by which pairs of films capable of entering into solid-phase reactions and their initiation temperatures can be determined.
Auger studies of Au diffusion through Pt films; dependence on annealing ambient
Pt/Au thin‐film couples were heat treated in 1 atm N2, He, and in vacuum. The outdiffusion kinetics of Au through the Pt were determined by measuring the Au concentration on the Pt surface using Auger electron spectroscopy. Au was found to outdiffuse through 6–10 kA Pt at rates 15 and 30 times faster in 1 atm N2 and 1 atm He, respectively, than in vacuum, at 350 °C. These results are the first published documentation of the remarkable acceleration of thin‐film interdiffusion caused by the presence of nonreacting gases.