Solution growth of crystalline silicon on glass in the In–Si–Mo system Robert Heimburger à , Thomas Teubner, Nils Deßmann, Hans-Peter Schramm, Torsten Boeck, Roberto Fornari Leibniz-Institut f¨ ur Kristallz¨ uchtung, Max-Born-Straße 2, 12489 Berlin-Adlershof, Germany article info Article history: Received 18 September 2009 Received in revised form 15 January 2010 Accepted 28 January 2010 Communicated by T.F. Kuech Available online 6 February 2010 Keywords: A3: Liquid phase epitaxy A3: Physical vapor deposition processes B2: Semiconducting silicon abstract Progress in low-temperature growth of crystalline silicon from a metallic solution is presented. Growth has been performed on glass that is coated with an electrically conductive layer. Thermodynamic stability of this interlayer in contact with the saturated growth solution is an essential precondition for subsequent process steps. Therefore, materials involved in the process must be properly chosen. Molybdenum disilicide thin films are shown to withstand the solution contact. In this way, further processing, that includes the formation of seed crystals by use of the vapor–liquid–solid mechanism and subsequent outgrowth from a low-temperature metallic solution, is successful. Growth of {1 1 1} faceted silicon crystallites on glass with a size of up to 200 mm in diameter has been shown. & 2010 Elsevier B.V. All rights reserved. 1. Introduction The growth of crystalline silicon on low-cost substrates like glass for application in thin film solar cells is still a challenging task. Several attempts have been made to produce thin films of polycrystalline silicon onto amorphous substrates. Much research work was conducted on the recrystallization of amorphous films by furnace [1,2] or laser annealing [3,4], and on metal-induced crystallization [5,6]. All techniques suffer from either a high density of grain boundaries or a high impurity content. In this paper, we present recent progress on low-temperature solution growth of silicon crystals on glass substrates. Main advantages of solution growth are low deposition temperatures and distribution coefficients far less than unity for common impurities. Because of the lack of lattice information in the case of amorphous substrates, the principles of conventional epitaxy have to be modified. It is widely accepted that formation of separated seeds or a continuous seeding layer promotes the growth of subsequent thick silicon layers. In our approach, well separated seeds are deposited by applying vapor–liquid–solid growth from indium microdroplets on conductive coated glass substrates [7]. Subse- quently, these seeds are enlarged by means of steady-state solution growth, again using indium as the solvent. Hereby, a temperature gradient, which is controlled by two thermocouples (T top and T bot ), promotes convective solute transport and super- saturation [8]. During this process, the conductive coating comes into direct contact with the growth solution and strong interac- tion of all constituents may set in. Therefore, phase relations, that include all constituents, have to be considered to identify coating materials that show only minor interaction with the growth solution. In this work we have analyzed and investigated the In–Si–Mo system with the target of providing a stable conductive electrode, which simultaneously acts as a template for the formation of the necessary droplets. In contrast to pure molybdenum, molybde- num disilicide is shown to withstand solution contact. Therefore, the application of MoSi 2 thin films instead of pure molybdenum is proposed as a novel approach. 2. Experimental First, the chemical stability of several conductive layers in contact with silicon saturated indium has been investigated. In former work regarding the feasibility of vapor–liquid–solid growth for seed crystal formation, molybdenum was used as it allows both, indium droplet formation and silicon seed crystal growth [7]. Therefore, the experiments started with electron beam evaporation of 50 nm thick Mo layers on glass. The deposition rate was measured using a quartz crystal microbalance and averaged 0.4 ˚ A/s. The deposition was carried out at a base pressure of 1  10 6 mbar and the substrates were not intention- ally heated. Afterwards, the samples were brought into contact with the silicon saturated growth solution for 2 h at 600 1C. The graphite crucible, the silicon feeding source and indium, which were used in these preliminary experiments, were replaced in order to start with a molybdenum-free growth solution in ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jcrysgro Journal of Crystal Growth 0022-0248/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2010.01.043 à Corresponding author. E-mail address: heimburger@ikz-berlin.de (R. Heimburger). URL: http://www.ikz-berlin.de (Leibniz-Institut f ¨ ur Kristallz ¨ uchtung). Journal of Crystal Growth 312 (2010) 1632–1635