Highly oriented and densely packed one-dimensional (1D) polycrystalline Zn nanorods were fabricated on zinc plate without any catalyst at room temperature by bombardment with obliquely incident Ar+ ion via ion irradiation method. The sputtered surfaces were fully covered with Zn nanostructures with diameter and the length around 60 nm and 1.3 mu m, respectively, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystal orientation of the Zn plate was investigated by electron back scattering pattern method (EBSP). The numerical density and morphology of Zn nanostructures (nanoneedle or nanorods) were found to be 2.1 x 10(6) to 9 x 10(6)/mm(2) depending upon the crystal orientation and the atomic density on different crystallographic faces. (2 (1) over bar(1) over bar0) faces of Zn polycrystal tended to form more dense nanostructures compared to (000 (1) over bar ) faces. This is because of lower atomic density on (2 (1) over bar(1) over bar0) faces in comparison with (000 (1) over bar )faces. This indicates that lower atomic density on any crystallographic faces is favorable to form nanostructure of higher density. The outstanding feature of this growth technique is that it provides a new direction for the controllable growth of desired nanostructures of variable density at room temperature without any catalyst. These well-aligned arrays of Zn nanorods/nanoneedle might be a promising material for the future application in nanodevices. (C) 2009 Elsevier B.V. All rights reserved.