TRANSMISSION ELECTRON-MICROSCOPY STUDIES OF MICROSTRUCTURAL EVOLUTION, DEFECT STRUCTURE, AND PHASE-TRANSITIONS IN POLYCRYSTALLINE AND EPITAXIAL TI1-XALXN AND TIN FILMS GROWN BY REACTIVE MAGNETRON SPUTTER DEPOSITION

The microstructural evolution, as revealed by plan-view and cross-sectional transmission electron microscopy, of polycrystalline NaCl-structure Ti1-xAlxN (x less-than-or-equal-to 0.5) and TiN films deposited by reactive magnetron sputter deposition is similar. At low growth temperatures (T(s) less-than-or-equal-to 500-degrees-C) and in the absence of ion bombardment, the films are underdense and exhibit a pronounced columnar morphology. The addition of low-energy (E(i) less-than-or-similar-to 200 eV) ion irradiation during deposition using incident ion-to-neutral ratios J(i)/J(n) less-than-or-equal-to 1 in mixed Ar/N2 plasmas results in film densification, defect incorporation, and a more equiaxed grain structure. At higher incident flux ratios (J(i)/J(n) greater-than-or-equal-to 4), low-energy ion irradiation provides increased apparent adatom mobility and, hence, larger grain size. The epitaxial temperature for mu-thick films of both Ti1-xAlxN (x less-than-or-equal-to 0.5) and TiN, deposited in pure N2 discharges, on MgO(001) substrates, is almost-equal-to 500-degrees-C. The density of {111} dislocation loops n(d), the primary defects, was found to depend both on T(s) and E(i). For example n(d) was decreased by several orders of magnitude using low-energy ion irradiation. However, the use of higher-energy (greater-than-or-equal-to 300 eV) ion irradiation gave rise to the formation of Ar and/or N2 gas bubbles due to precipitation of trapped ions. Plastic deformation in the films took place through glide of edge dislocations. Phase transition reaction paths were determined for Ti1-xAlxN as a function of x and T(s). In the case of epitaxial Ti0.5Al0.5N, increasing T(s) resulted in surface-initiated spinodal decomposition during growth in the range T(s) = 540-560-degrees-C with the formation of compositionally modulated NaCl-structure platelets along [001] as a precursor to bulk phase separation of wurtzite-structure AlN and NaCl-structure TiN at higher T(s). In the case of Ti1-xAlxN grown on oxidized silicon at T(s) = 500-degrees-C, increasing x resulted in single-phase NaCl-structure alloys for 0 less-than-or-equal-to x less-than-or-similar-to 0.4, two-phase TiN and AlN-structure for 0.4 < x less-than-or-similar-to 0.9, and single-phase AlN for x > 0.9. Pseudomorphic forces associated with growth on MgO(001) substrates extended the stability range for the NaCl-structure phase to x greater-than-or-equal-to 0.5 at T(s) = 500-degrees-C.