Optical Studies of Reactively Co-Sputtered Bcn Thin Films

The motivation behind the boron carbon nitride (BCN) ternary compounds is their similarities in the structure and difference in properties between graphite and hexagonal boron nitride (h-BN). Both theoretical calculations and experimental studies show that BCN compounds exhibit excellent mechanical, optical and electrical properties [1], [2]. In particular, the possibility to control the band gap (E_G) by atomic composition and structure makes them good candidates for the application in electronic and photonic devices [3], [4].

The optical characteristic like transmittance is improved with initial incorporation of nitrogen into the film composition and has a stable trend with further increase in nitrogen concentration.  Also the optical band gap of BCN (2.2eV-3eV) increased with incorporation of nitrogen and said to follow a linear trend between B₄C (2eV) and BN (4eV) [5]. The co-sputtering helps in creation of films with graded indexes of refraction as well. It gives more freedom to vary the composition as when compared to single target sputtering. Thickness uniformity and the film quality are better when using co-sputtering.

Dual target approach will be conducted to prepare BCN tin films. In this work we are depositing BCN thin films on quartz substrates using two targets namely B₄C and BN using RF power and DC power respectively at different N₂/Ar gas flow ratios. Also the input power for B₄C and BN are varied to achieve different composition of the BCN thin films to control the optical properties. The optical properties like transmission and reflectance are studied using the UV-visible spectrophotometer. The optical absorption is studied by Tauc plot which is instrumental in finding the optical band gap of the material and the refractive index.

REFERENCES

[1] I. Caretti, J.M. Albella, I. Jiménez,  Diamond Relat. Mater., 16 (2007), p. 1445

[2] A. Perrone, A.P. Caricato, A. Luches, M. Dinescu, C. Ghica, V. Sandu, A.Andrei , Appl. Surf. Sci., 133 (1998), p. 239

 [3] M.O. Watanabe, S. Itoh, K. Mizushima, T. Sasaki, J. Appl. Phys., 78 (1995), p. 2880

 [4] P.R. Fitzpatrick, J.G. Ekerdt, J. Vac, Sci. Technol. A, 26 (2008), p. 1397

[5] Optical characterization of BCN films deposited at various N₂/Ar gas flow ratios by RF magnetron sputtering

.