Energy Postgraduate Conference 2013 Low temperature deposition of silicon nitride thin films by hot-wire CVD University of the Western Cape A. Adams and C. J. Arendse Energy Postgraduate Conference 2013

Outline Introduction Experimental Details Results Conclusion Acknowledgments

Introduction Solar power Energy crises Viable alternative Amorphous solar cells Antireflective coating for increased efficiency Multitude of uses stemming from stoichiometric tunability Permeation barrier Gate insulator in thin film electronics Passivation of dangling bonds Antireflective coating Deposition Method Current technique of choice is PECVD Ion bombardment, resulting in oxidation Complex (potential difference, plasma source) Desired technique of choice is HWCVD Ease of upscale Eradicates bombardment (absence of plasma ions) Low cost High deposition rates of > 7 nm/s Low temperature deposition

Experimental details The a-SiN:H thin films were deposited at Tw=1400 °C, Ts = 240 °C, P = 100 µbar, ΦH2 = 20 sccm, ΦSiH4 = 5 sccm and ΦNH3 = 1 – 7 sccm (LOW PARAMETERS) Technique Information Reflectance ·         Thickness ·         Band Gap ·         Refractive index FTIR ·         SiN bonds ·         Total bonded H EDS ·         N/Si ratio AFM ·         Surface morphology ·         Roughness ERDA ·         H depth profiling TOF-HIERD ·         N depth XRD ·         Phase

Results and discussion Decrease in surface roughness as ΦNH3 is increased columnar structures decreases Decrease in deposition rate as ΦNH3 is increased Competing reaction at the filament

Results and Discussion Films are uniform Negligible oxidation occurred in the bulk Increase in N content as NH3 is increased ToF-HIERD and EDS corroborate well NH3 = 5 sccm

Results and Discussion

Results and discussion Linear relation between static refractive index and N content Direct relation between Tauc band gap and N content

Conclusion Future Work High quality a-SiN:H deposited at low processing parameters, suitable for device applications (permeation barrier, Passivation layer) Resistant to oxidation Tuneable refractive index Corroboration between EDS, ToF-HIERD Low H content Silicon rich Films Future Work Incorporation in organic PV devices

Acknowledgments Financial Support Team University of the Western Cape National Research Foundation (NRF) Team A. Adams, Prof. C. Arendse, Dr. T. F. G. Muller, Dr. G. Malgas, Dr. C. Oliphant and Dr. M. Msimanga.