STRUCTURAL CHANGES STUDIES OF a-Si:H FILMS DEPOSITED BY PECVD UNDER DIFFERENT HYDROGEN DILUTIONS USING VARIOUS EXPERIMENTAL TECHNIQUES Veronika Vavruňková 1 Jarmila Müllerová 2 Rudolf Srnánek 3, Pavol Šutta 1 1 Department of Materials and Technology, New Technology Research Centre, University of West Bohemia, Univerzitní 8, Plzeň, , Czech Republic 2 Department of Engineering Fundamentals, Faculty of Electrical Engineering, University of Žilina, ul.kpt. J. Nálepku 1390, Liptovský Mikuláš, Slovakia 3 Department of Microelectronics, Slovak University of Technology, Ilkovicova 3, Bratislava, , Slovak Republic Corresponding author: Introduction thin films of a-Si:H prepared using the hydrogen dilution in silane source gas by plasma enhanced chemical vapour deposition (PECVD) belong to promising materials for low-cost solar cells this deposition technique has been used to yield material with good opto- electrical properties, such as light stability (less light induced degradation known as Staebler-Wronski effect), higher optical band gap the structure of films is necessary to understand and improve properties of the a-Si:H films which is significant for the application in solar cells in this work, we focus on the effects of hydrogen dilution ration on the structural quality and evolution of c-Si in amorphous network protocrystalline silicon constitutes the evolution from amorphous to nanocrystalline silicon and contains the medium-range order (MRO) X-ray diffraction Experimental material a series of a-Si:H thin films were deposited using rf-PECVD under increasing dilution of silane plasma by hydrogen the hydrogen to silane dilution ratio R = H 2 /SiH 4 was varied from 5 to 40 the samples were deposited on Corning glass 1737 substrates and on [100] oriented c-Si wafers a reference sample was deposited using pure silane (R = 0) the thickness of all films was approximately 300 nm the XRD patterns were recorded using automatic power diffractometer X´pertPro with the Cu X-ray tube ( = nm) and a thin film attachment Raman spectroscopy the Raman spectra were excited with a He-Ne laser generating the wavelength of nm FTIR spectrometry Conclusions References R = 20R = 25 R = 30 TEM images of 1  m thick a-Si:H films deposited at different dilution R [TU Delft] substrate and dilution influence MRO was determined from thin films deposited on c-Si lower value of FWHM indicates that films and contain MRO ~ 5-7 nm in size evolution of the crystalline phase with increasing dilution on samples on glass substrate Si (220) 2D detector grain size mapping from the surface 5 x 5 μm integral intensity of Si crystalline peak IR absorbance spectra were performed in the range of 650 – 4000 cm -1 using the ATR accessory with trapezoidal silicon crystal with a bevelled edge of 45  microstructure factor and hydrogen concentration the hydride configurations are agreeing with contribution to vacancies and void surfaces stretching vibrations of silicon hydrides SiH (2000cm -1 ) and SiH 2 (2090cm -1 ) [1]Van Elzakker, G.; Šutta, P.; Tichelaar, F.; Zeman, M. Phase control and stability of thin silicon films deposited from silane diluted with hydrogen. In MRS Symposium Proceedings. Vol Warrendale : ISBN [2]Park, Y. - B., Rhee, Y. – B. Microstructure and initial growth characteristics of the low temperature microcrystalline silicon films on silicon nitride surface J. Appl. Phys. 90, 217 – 221 (2001). [3]Stannowski, B., Schropp, R.E.I. Thin Solid Films, 383 (2001) p.125 – 128. [4]Vavruňková, V., Müllerová, J., Šutta, P. AEEE. 6 (2007), p formation of the polycrystalline phase with increasing dilution – samples on glass c-Si substrate - amorphous containing medium-range order medium-range order determined from the films deposited on c-Si ~ 5-7 nm grain sizes calculated from Raman spectrometry increase with increasing dilution about ~ 3-5 nm films - quite homogeneously microstructure factor ~ 12 % in average, material - slightly porous