Love mode surface acoustic wave devices based on ZnO/42 degrees YX LiTaO3 were characterized with the thickness of the sputtered ZnO guiding layer varied from 250 nm to 1.18 mu m. Phase velocity, temperature coefficient of resonant frequency, sensitivity, electromechanical coupling coefficient and humidity sensing of the Love mode SAW devices were studied as a function of the ZnO layer thickness. With increasing ZnO thickness over the range of thickness values we have examined, the sensitivity of 42 degrees YX LiTaO3 to liquid loading increased and the values of electromechanical coupling coefficient decreased. The device with a thickness of 250 nm showed the best humidity response. ZnO nanorods were grown on this device and its humidity sensing performance has been further improved due to their large surface-to-volume ratio of the ZnO nanorods. (C) 2013 Elsevier Ltd. All rights reserved.