Thin Solid Films 403 – 404 (2002) 543–548 0040-6090/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0040-6090 Ž 01 . 01651-0 Electron microscopic characterization of microcrystalline silicon thin films deposited by ECR-CVD I. Sieber*, N. Wanderka, I. Kaiser, W. Fuhs Hahn-Meitner-Institut, Kekulestr. 5, D-12489 Berlin, Germany ´ Abstract Microcrystalline silicon (mc-Si) thin films were deposited by electron cyclotron resonance-chemical vapor deposition (ECR- CVD) on single crystal silicon (c-Si) and glass substrates at temperatures of 325 and 465 8C. The films and the interfaces were characterized by scanning and transmission electron microscopy (SEM, TEM). On c-Si substrates local initial epitaxial growth was observed, on glass substrates an amorphous interlayer is found for films deposited at 325 8C. It is shown that using this deposition technique and proper choice of the deposition parameters (high substrate temperature, low deposition rate) the initial growth of an amorphous film can be avoided.  2002 Elsevier Science B.V. All rights reserved. Keywords: Microcrystalline silicon; ECR-CVD; Structural properties; Electron microscopy 1. Introduction Hydrogenated microcrystalline silicon (mc-Si:H) thin films are produced mainly by chemical vapor decom- position of SiH y H gas mixtures. Such films are known 4 2 to grow in complicated heterogeneous and anisotropic structures which may depend on the film thickness and which are strongly influenced by the nature of the substrate. Characteristic features of the growth of this material are the pronounced columnar structure and an initial amorphous layer. This behavior has been observed for a large variety of chemical vapor deposition proc- esses, such as plasma-enhanced PECVD w1–3x, very- high frequency VHF PECVD w4,5x, electron cyclotron resonance ECR CVD w6x and hot-wire CVD w7x. This phenomenon of course is of great importance for appli- cations of mc-Si:H in large area devices such as solar cells. This quite general occurrence of an amorphous interlayer in the deposition of mc-Si-films suggests to consider this effect as an inherent property of the growth of thin films at low temperature on foreign substrates. Recently this behavior has been explained in terms of * Corresponding author. Tel.: q49-30-67053-354; fax: q49-30- 67053-333. E-mail address: sieber@hmi.de (I. Sieber). ‘Ostwald’s rule of stages’ which states that the conden- sation of a solid phase from the gas phase first leads to the formation of metastable phases before the most stable phase can grow w8x. In this picture the initial growth of amorphous silicon is a natural consequence of a growth mechanism which proceeds via a set of phases of descending metastability and nucleation. The interesting question is as to whether deposition para- meters can be found, which avoid the initial a-Si-growth. Here we report on a structural study using electron microscopy to examine the substrate y mc-Si interface of films prepared by ECR-CVD on glass and crystalline silicon substrates. It is shown that using ECR-CVD the amorphous interlayer can be avoided by a proper choice of deposition conditions. 2. Experimental details Microcrystalline silicon films were deposited by plas- ma-enhanced CVD from SiH y H gas mixtures. The 4 2 plasma was generated by an electron cyclotron resonance (ECR) operating at 2.45 GHz. The microwave power amounted to 1000 W and was coupled to the plasma region through a fused silica window. Details of the applied technique have been described recently w9x. The polished (111) silicon wafers were cleaned by the