NOVELTY - A string (12) for a string ribbon crystal (10), comprises a substrate (28); a refractory layer (30) supported on the substrate; and an externally exposed layer (32) having a contact angle of 5-120 degrees with the crystal material. The externally exposed layer is radially outward of the refractory layer. The string ribbon crystal comprises a crystal material. The crystal material comprises silicon, silicon-germanium, gallium arsenide or indium phosphide. The string has a coefficient of thermal expansion that matches with a coefficient of thermal expansion of the crystal material.    USE - As a string useful for forming a string ribbon crystal (claimed) useful for forming electronic devices such as photovoltaic/solar cell.    ADVANTAGE - The string has a high contact angle (i.e. 5-120 (preferably greater than 25) degrees ) with the ribbon crystal material. The string having a coefficient of thermal expansion that matches with a coefficient of thermal expansion of the crystal material, improves the robustness of the ribbon crystals. The string has a reduced wetting, outer exposed layer that increases grain size near the edge of a ribbon crystal. The increase in grain sized near the string, improves electrical efficiency of the ribbon crystals. The handling layer provides a small compressive stress to the base string portion, thus improving robustness to the overall string.    DETAILED DESCRIPTION - A string (12) for a string ribbon crystal (10), comprises a substrate (28); a refractory layer (30) supported on the substrate; and an externally exposed layer (32) having a contact angle of 5-120 degrees with the crystal material. The externally exposed layer is radially outward of the refractory layer. The string ribbon crystal comprises a crystal material. The crystal material comprises silicon, silicon-germanium, gallium arsenide or indium phosphide. The string has a coefficient of thermal expansion that matches with a coefficient of thermal expansion of the crystal material. The string further comprises a handling layer radially outward of the refractory layer. The handling layer applies a radially inward force to the refractory layer. The exposed layer is thinner than the refractory layer. INDEPENDENT CLAIMS are included for the following:    (1) the ribbon crystal comprising the string having a string coefficient of thermal expansion and an outer surface; and a body comprising a body material having a body coefficient of thermal expansion that matches with the string coefficient of thermal expansion, where the string outer surface is partially exposed;    (2) forming the string involving forming the refractory layer on the substrate; and applying a reduced wetting material radially outward of the refractory layer, where the reduced wetting material has a contact angle with silicon of 15-120 degrees ; and    (3) forming the ribbon crystal involving providing molten material having a material coefficient of thermal expansion; providing the string having outer surface with contact angle with the molten material of 15-120 degrees , and a string coefficient of thermal expansion that is matching with the material coefficient of thermal expansion; and passing the string through molten material to form a sheet.    DESCRIPTION OF DRAWING(S) - The figures show a schematic cross-sectional view of a string, and a schematic cross-sectional view of a ribbon crystal using the string.    Ribbon crystal (10)    String (12)    Substrate (28)    Refractory layer (30)    Thin neck portion (36)    Wider portion (38)