Abstract Zinc oxide thin films grown by sol–gel and RF sputtering methods have been characterized. The characterization techniques used involve ellipsome- try, optical absorption, scanning tunneling micros- copy, scanning and transmission electron microscopy. The films grown by sol–gel spin method which followed zinc acetate route exhibited a smoother texture than the films, which were deposited by using zinc nitrate route. The later type of films showed a dendritic character. Nano-structured fine grains of size ranging from 20 to 60 nm were observed with zinc nitrate precursor film. Individual grains show a sharp contrast with different facets and boundaries. Crystal planes and lattice parameters calculated by electron diffraction and X-ray diffraction are quite close and in agreement with the reported values in literature. Scanning tunneling microscopy has been used for measuring the average roughness of the surface and estimating the lattice constants. The STM studies of RF sputtered films, although showing a ZnO structure, exhibited a disturbed lattice. This was presumably due to the fact that after deposition the films were not annealed. Nanographs of 2D and 3D view of atomic positions of ZnO have been presented by using scanning tunneling microscopy. Introduction Thin films of zinc oxide have varied technological applications such as piezoelectric transducer [1], transparent conductor [2], surface acoustic wave devices [3, 4] and a variety of sensors [5, 6]. Conse- quently, thin films of ZnO are grown by a variety of methods such as vacuum evaporation [7], sputtering [8], MOCVD [2, 9], sol–gel [10] chemical solution deposition [11], chemical vapor deposition [12] and spray pyrolysis [13] etc. It is known that ZnO has a wurtzite structure having a number of alternating planes composed of fourfold coordinated O 2– and Zn 2+ ions stacked alternatively along c-axis of hexag- onal unit cell with lattice constants; a 0 = 0.3255 nm and c 0 = 0.5216 nm. The tetrahedral coordination in ZnO results in non-central symmetric structure and the consequent piezoelectric and pyroelectric nature of the material. It can thus be considered as two interpenetrating hexagonal closed-packed lattices of Zn and O. The preparation and characterization of ZnO thin films has been the subject of continuous research for a long time because the properties of ZnO films depend upon the method of preparation. Currently, there is a great interest in the methods of creating nanostructures H. Bahadur (&) Á S. B. Samanta Á A. K. Srivastava Á K. N. Sood Á R. Kishore Á R. K. Sharma Á A. Basu Á Rashmi Á M. Kar National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012, India e-mail: hbahadur@yahoo.com P. Pal Á V. Bhatt Á S. Chandra Centre for Applied Research in Electronics, Indian Institute of Technology Delhi, Hauz-Khas, New Delhi 110016, India J Mater Sci DOI 10.1007/s10853-006-0841-x 123 Nano and micro structural studies of thin films of ZnO Harish Bahadur S. B. Samanta A. K. Srivastava K. N. Sood R. Kishore R. K. Sharma A. Basu Rashmi M. Kar Prem Pal Vivekanand Bhatt Sudhir Chandra Received: 28 October 2005 / Accepted: 18 November 2005 Ó Springer Science+Business Media, LLC 2006