Ž . Thin Solid Films 383 2001 110112 Grain populations in laser-crystallised silicon thin films on glass substrates M. Nerding a,  , S. Christiansen a , J. Krinke a , R. Dassow b , J.R. Kohler b , J.-H. Werner b , ¨ H.-P. Strunk a a Uni  ersitat Erlangen-Nurnberg, Institut fur Werkstoffwissenschaften, Lehrstuhl fur Mikrocharakterisierung, Cauerstr. 6, D-91058 ¨ ¨ ¨ ¨ Erlangen, Germany b Uni  ersitat Stuttgart, Institut fur Physikalische Elektronik, Pfaffenwaldring 47, D-70569 Stuttgart, Germany ¨ ¨ Abstract We investigate the polycrystalline microstructure, i.e. grain size and orientation distribution, that forms during laser crystallisation of amorphous silicon on glass substrates by a frequency doubled Nd:YVO -laser operating at a wavelength of 532 4 nm. Transmission electron microscopy reveals that the grains have an average width from 0.25 to 3 m and a length of several 10 m. Electron back-scattering diffraction indicates that the grain orientation of the poly-Si films is textured. Type and extent of texturing depend in a complex way on the thickness of the crystallised amorphous silicon layer and on whether or not a buffer layer is present.  2001 Elsevier Science B.V. All rights reserved. Keywords: Transmission electron microscopy; Electron back-scattering diffraction; Laser crystallisation; Texture; Grain orientation distribution 1. Introduction Ž . Polycrystalline silicon poly-Si fabricated at low tem- peratures is of great interest for large area electronics on temperature sensitive, cheap substrates. Possible Ž . devices are thin film transistors TFTs in active matrix   liquid displays 1 and thin film solar cells 2 on glass.   Over the past few years a variety of techniques 3  6 were applied to improve the performance of the films essentially to control the defect population, density and location. Especially for thin film solar cells, where laser crystallised films are used as seeding layers for a subse- quent epitaxial, low-temperature thickening process but also for TFTs, the surface normal needs to be con- trolled in many cases. The defect density produced by Ž the most promising thickening processes e.g. ion-as- sisted deposition, electron-cyclotron resonance chemi-  Corresponding author. Tel.: 49-9131-8528618; fax: 49-9131- 8528602. Ž . E-mail address: nerding@ww.uni-erlangen.de M. Nerding . . cal-vapour deposition shows a strong dependence on  the crystallographic orientation of the seeding layer 7  4 with the 100 surface normal direction having the lowest defect density. We analyse in this paper how the grain size and the texture are influenced by the process parameters and thereby give a first indication on how to control them. 2. Experimental Ž . The amorphous silicon a-Si layers, deposited by sputtering on Corning 1737F glass substrates are crys- tallised by the so-called sequential lateral solidification Ž .  process SLS 8 . This method is based on lateral epitaxy where the already formed grains act as seeds for the solidification process in the adjacent melt. An important aspect of this technique is that elongated, large grains, result only when the a-Si layer is com- pletely molten when laser irradiated. This defines a Ž minimum laser pulse energy depending on film thick- . ness required for growth of large grained material. 0040-609001$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 0 - 6 0 9 0 00 01623-0