Metal-to-Dielectric Transition Induced by Annealing of Oriented Titanium Thin Films

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible.This is an author-deposited version published in: http://sam.ensam.eu Handle ID: .http://hdl.handle.net/10985/7486 To cite this version :Aurélien BESNARD, Nicolas MARTIN, Nicolas STAHL, Luc CARPENTIER, Jean-Yves RAUCHMetal-to-Dielectric transition induced by annealing of oriented titanium thin films -Functional Materials Letter -Vol. 6, n°1, p.5 -2013 Any correspondence concerning this service should be sent to the repository Titanium thin films were deposited by dc magnetron sputtering. The GLancing Angle Deposition (GLAD) method was implemented to prepare two series of titanium films: perpendicular and oriented columnar structures. The first one was obtained with a conventional incidence angle a of the sputtered particles (a = 0°), whereas the second one used a grazing incidence angle a = 85°. Afterwards, films were annealed in air following 6 incremental cycles of temperatures ranging from 293 to 773 K. Dc electrical conductivity was measured during the annealing treatment. Films deposited by conventional sputtering (a = 0°) kept a typical metallic-like behavior versus temperature (s300K = 2.0´10 6 S m -1 and TCR293K = 1.52´10 -3 K -1 ), whereas those sputtered with a = 85° showed a gradual transition from metallic to dielectric material. Such a transition was mainly attributed to the high porous structure, which favors the oxidation of titanium films to tend to the TiO2 compound.Keywords: Sputtering, thin films, electrical properties, metal, dielectric. * Corresponding authorMetal-insulator transitions have been investigated for many years [1]. They often arise from variations of the chemical composition, temperature, stress, electric or magnetic field, etc. [2][3][4]. They correspond to a transformation between states with a dielectric (or semiconductor) and a metallic type of conductivity. Materials exhibiting these phenomena include binary compounds of transition metal oxides. As a result, these transitions have largely been explored for bulk materials like vanadium oxides [5], but few studies have been devoted to such transitions for other materials [6] and to the best of our knowledge, never for thin films exhibiting an oriented columnar structure.In this work, we report on the effect of an annealing treatment on the micro-structural properties, optical behaviors and dc electrical conductivity of titanium films sputter deposited. Two series of samples were prepared. The first one was conventionally prepared with a normal incidence angle a of the sputtered particles (a = 0°). For the second series, the GLancing Angle Deposition (GLAD) was implemented to produce an oriented columnar structure. An incidence angle a = 85° was used to deposit an oriented structure. Both series were heated in air following 6 cycles from 293 to 773 K. Titanium films obtained at normal incidence (a = 0°) kept a metallic-like behavior, whereas those deposited by GLAD (a = 85° )...

Electrochemical characterization of nanostructured Ag:TiN thin films produced by glancing angle deposition on polyurethane substrates for bio-electrode applications

“…Consequently, more intercolumnar voids are created, thus the porosity of the GLAD deposited films is increased. This porosity increase is also closely related with the increase of the number of zigzag periods [22,26,29,39,42,60]. The obtained ß angles corroborate the morphology and porosity changes, since they vary from a minimum of 23°(for the compact α = 40°sample) to an average of 29°for the porous films.…”

“…Thus, GLAD thin films, prepared by either evaporation or magnetron sputtering are becoming an attractive strategy to obtain a wide variety of architectures and sculptured materials at the micro-and nanoscale. This involvement is mostly evident for metal and oxide coatings sputter deposited with inclined architectures [39][40][41][42][43] but very few studies are dedicated to metallic nitrides produced by the GLAD technique [44][45][46], especially regarding the relations between the possible achieved structures by GLAD (e.g. inclined columns, zigzags, spirals) and the resulting properties in terms of mechanical response, electrical conductivity or even electrochemical behaviour.…”

Synthesis of iron oxide films by reactive magnetron sputtering assisted by plasma emission monitoring

“…Film growth with an oblique incidence is a well-known phenomenon. The microstructure and the morphology can strongly be modified according to the incidence angle value, leading to the presence of porosity [47]. As previously observed by Charles et al, the diminution of the transmittance with the incidence angle could be also ascribed to a change in the porosity of the microstructure [48].…”

Improvement of ozone detection with GLAD WO3 films

“…In addition, it was previously shown that GLAD films become strongly porous for α4601 (due to extreme shadowing). Oxidation of the film is also enhanced when heated at 250 1C [19]. Thus oxygen deficiencies are strongly reduced and cannot be considered as the main criterion influencing the sensor performances.…”