Physical and chemical properties of sputter-deposited TaC_xN_yfilms

Abstract

The structural, electronic, optical, and mechanical properties of stoichiometric TaC(x)N(y = 1-x) were simulated using an ab initio calculation based on density functional theory (DFT) within the generalized gradient approximation. The calculations revealed the theoretical lattice parameter, density of states, refractive index, and elastic constants as a function of carbon and nitrogen content. TaC(x)N(y) films were subsequently produced on Si wafers using unbalanced magnetron sputtering. The structural, optical, and mechanical properties were measured using x-ray diffraction/transmission electron microscopy, vacuum ultraviolet spectroscopic ellipsometry, and nanoindentation, respectively. The computational and experimental properties were compared. The lattice parameter, the energy of the 2p bands in the density of states, and the energy of the interband transitions were found to decrease with increasing C content. No significant changes in the elastic constants were observed as a result of substituting N atoms with C atoms. The hardness and the elastic modulus were in the 40 and 380 GPa range, respectively. The experimental Young's modulus was much smaller than the computational one and this discrepancy was attributed to the nanocrystalline nature of the films. Also, the elastic constants were found to decrease dramatically for over-stoichiometric films.

Identification of a potential superhard compound ReCN

“…Studies of hard coatings indicate that the electronic and mechanical properties of transition metal nitrides (carbides) are generally expected to be significantly modified by the incorporation of carbon (nitrogen) [22][23][24][25][26] . Thus transition metal carbonitrides could be potentially useful hard materials.…”

Tuning structure and mechanical properties of Ta-C coatings by N-alloying and vacancy population

“…To date, Ta-C-N thin films have only been employed as diffusion barriers between copper and silicon in semiconductor devices 25 . Their use as protective coating with excellent mechanical properties, especially in a highly crystalline constitution, is indeed relatively unexplored 24 , 26 .…”

Detection of ultrathin biological films using vacuum ultraviolet spectroscopic ellipsometry

“…In literature, researchers have used VUV-SE to investigate: (a) interband optical properties of crystalline (quartz) and amorphous SiO 2 [11], (b) optical properties of thin silicon oxynitride film with thickness 25-35 nm [12], (c) direct observation of the dielectric properties of cubic SiC from electronic transitions [13], (d) optical and electronic properties of amorphous carbon films [13] and [14], (e) electronic structure of complex oxides such as high k dielectrics [15], [16], [17], [18], [19] and [20], (f) optical properties of binary transition metal (TM) nitrides and carbides [21], (g) optical constants of lithography based films (photoresists, AR coatings, etc.) and Alq 3 thin films for large-area display applications [22] and (h) optical and electronic properties of high refractive index materials such tantalum oxide thin films [23].…”