Well-aligned arrays of silicon nanowires (SiNWs) have been synthesized by a chemical vapor deposition (CVD) template method without catalyst. The micro-structures of the SiNWs were studied by high-resolution transmission electron microscopy (HRTEM). Selected-area electron diffraction (SAED) and X-ray diffraction (XRD) indicate that each nanowire is essentially a single crystal and has a different orientation in an array. According to VLS mechanism, the growth of SiNWs without catalyst is related to the structure of template. The superior field emission behavior is believed to result from the oriented growth and the sharp tips of SiNWs. (C) 2003 Elsevier Science B.V. All rights reserved.