Optical, electronic, and transport properties of nanocrystalline titanium nitride thin films

Abstract

Heteroepitaxial VO2 thin films on GaN: Structure and metal-insulator transition characteristics J. Appl. Phys. 112, 074114 (2012) Investigation of nonuniformity phenomenon in nanoscale SiO2 and high-k gate dielectrics J. Appl. Phys. 112, 064119 (2012) Strain dependent stabilization of metallic paramagnetic state in epitaxial NdNiO3 thin films Appl. Phys. Lett. 101, 132101 (2012) Electrical and optical properties of vanadium dioxide containing gold nanoparticles deposited by pulsed laser deposition Appl.Spectroscopic ellipsometry ͑SE͒ was employed to get insights on the optical, electronic, and transport properties of nanocrystalline titanium nitride (TiN x ) films with respect to their microstructure and stoichiometry. The films' properties can be tailored by varying the energy of bombarding ions during sputter deposition and the substrate temperature (T d ). The best metallic behavior of TiN x ͑resistivity 40 ⍀ cm and conduction density 5.5ϫ10 22 electrons/cm 3 ͒ has been observed in films developed with energy above 100 eV and T d у400°C. A redshift of the optical gaps has been observed for overstoichiometric films, suggesting it as a sensitive probe to investigate the TiN x stoichiometry. The energy, strength, and broadening of the interband transitions were studied with respect to the energy of ions and T d and they were explicitly correlated with the TiN x crystal cell size and grain orientation. On the other hand, the study of intraband absorption has provided the conduction electron density with respect to ion energy and T d , which promotes the densification of TiN x films due to different mechanisms. Combined SE and x-ray analysis was used to identify the electron scattering mechanisms, showing that the main electron scattering sites are the grain boundaries and the Ti vacancies for stoichiometric (xϭ1) and overstoichiometric (xϳ1.1) films, respectively.

Reactive deposition of TiNx layers in a DC‐magnetron discharge

“…For these films also, the complex refractive index profiles versus wavelength measured by SE techniques are compatible to titanium nitride. [11] These supplementary results prove the XR layer analyses.…”

In situ spectroscopic ellipsometry study on the growth of ultrathin TiN films by plasma-assisted atomic layer deposition

“…19 The interband absorptions in the TiN can be described by Lorentz oscillators. 21 In the literature, the dielectric function of TiN is often composed of two Lorentz oscillators to account for the interband absorption around 3.5 and 5.2 eV. 21,27,28 We adopted the same model and describe the dielectric function by the combination of a Drude term and two Lorentz oscillators:…”

“…21,22 The Drude oscillator accounts for the intraband absorption of the free electrons and, therefore, contains information on the metallic properties of the TiN film. 19 The interband absorptions in the TiN can be described by Lorentz oscillators.…”

“…For TiN, the atomic mass is A ͑=A Ti + A N ͒ = 62 amu and we assume a value of Z = 0.95. 21 An estimation on the effective electron mass is required to calculate the mass density. Following Patsalas and Logothetidis, we estimate the effective electron mass to be m * = 1.15m e , in which m e is the electron rest mass.…”

“…8 It is obvious that the change of material properties with film thickness is of key importance for ALD of ultrathin metallic films and should be studied in greater detail. In addition to the work of Patsalas and Logothetidis who used spectroscopic ellipsometry to study dc reactive magnetron sputtered TiN films, 21,22 we will use in situ spectroscopic ellipsometry to obtain detailed information on the film thickness and the material properties during the PA-ALD growth process of ultrathin TiN films. The experimental procedure and ellipsometry data analysis procedure using the Drude-Lorentz oscillator parametrization will be described in more detail in Secs.…”