Optical and structural properties of RF-sputtered Si x C 1-x thin films

1. PSCM Optical and structural properties of RF-sputtered SixC1-x thin films International Conference on Nano-Materials and Renewable Energies Presented by : Abdelilah El Khalfi • EL KHALFI ,E. ECH-CHAMIKH ,Y. IJDIYAOU, M. AZIZAN,A. ESSAFTI • Laboratoire de Physique du Solide et des Couches Minces, Faculté des Sciences • Semlalia,Université Cadi ayyad, BP : 2390, Marrakech 4000, Maroc

2. OUTLINE • Introduction • Experimental details - Deposition technique - Characterization techniques • Results and discussion • Structural properties • Optical properties • Conclusion & prospects

3. Introduction • a-SiC is mach attractive in the nano-materials field. • Some applications : • Electronic devices; Anti-wear, protective and hard surface coatings; solar cells • Many works, on amorphous silicon carbide (a-SixC1-x), realized by RF-Sputtering by : - Multilayers method (silicon and graphite targets) - From silicon carbide target - From composite target (co-sputtering) • In this work : co-sputtering (with RF power varying from 150 to 350W and Si/C surface rate coverage from 17% to 33% of total graphite target surface)

4. Experimental details - Deposition technique : RF-sputtering Experimental conditions: Residual pressure : 10-6 mbar Argon pressure : 10-2 mbar Composite target : Graphite target (5N) with silicon chips (fragments ) (17% to 33% of total graphite target surface) RF power : 150 W, 250 W and 350 W. Deposition time : 2 hours for all samples prepared Graphite target silicon chips Composite target (Silicon chips + graphite target )

5. - Characterizationtechniques Structural properties of thin films • Optical properties : • Absorption coefficient • Refractive index • Optical band gap • Thin films thickness Grazing incidence X-Ray Diffraction (GIXD) UV-Visible-NIR Spectroscopy

6. Results and discussion - GIXD Measurements • Typical GIXD diagrams of as deposited a-SixC1-x thin films : Amorphous films

7. Optical measurements - Theoretical formula Transmission Coefficient : Refractive index : Films thickness :

8. Absorption Coefficient : For amorphous thin films : the optical band gap is indirect

9. - Optical transmission

10. Variation of the deposition rate versus the surface coverage Si/C and the RF power - Films thickness For the explored ranges of Si compositions and RF powers, the deposition rate, of the a-SixC1-x thin films, increases with the RF power and the Si fragments surface coverage ratio.

11. - Optical band gap Variation of the optical band gap versus the surface coverage Si/C and the RF power The optical band gap increases from 1,7 to 2,2 eV with increasing the Si content or decreasing the RF power.

12. - Refractive index Variation of the refractive index With the low of Cauchy ; n(l ) = n(IR) + b/(l²)

13. Refractive index (in IR) Variation of the refractive index (IR) versus the surface coverage Si/C and the RF power : is the same of thickness film • The refractive index n(IR) varies from 2 to 2,5

14. Conclusion • All the as deposited SixC1-x thin films are amorphous. • The deposition rate of the a-SixC1-x thin films increases with the RF power and the Si fragments surface coverage ratio. • The optical band gap increases from 1,7 to 2,2 eV with increasing the Si content or decreasing the RF power. • The refractive index n(IR) varies from 2 to 2,5

15. Prospects • Complete the results obtained by other analytical techniques such as RBS or XPS, RAMAN, IR, electrical measure • Enlarge the target surface covered (by the Si ships) : from 0% to 100% • Study the surface roughness and electronic density by Grazing incidence X-Ray Reflectometry (GIXR) • Annealing effect on the properties of SixC1-x • Addition of gases (H2, O2 and N2) to produce SixC1-x:H,O,N thin films

16. Thank you for your attention