Three-dimensional (3D) nanowire network is a potential building block for nanodevices. Films of 3D tungsten nanowire networks were found early, and the present study is to develop a technical procedure for achieving very high percentage of 3D tungsten nanowire networks in a film. We demonstrate that the content of 3D tungsten nanowire networks in a film, prepared by thermal vapor deposition, may be adjusted by controlling the temperature of substrate, and also that films of very high percentage of 3D tungsten nanowire networks may be prepared. It is found that all films exhibit stable field electron emission, but that the performance varies depending on content of 3D nanowire networks. (C) 2009 Elsevier B.V. All rights reserved.