Correlation between structural and electrical properties of PLD prepared ZnO thin films used as a photodetector material

• Published in: Applied surface science Vol. 359; pp. 266 - 271
• Main Authors: Triolo, C., Fazio, E., Neri, F., Mezzasalma, A.M., Trusso, S., Patanè, S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-12-2015
• Subjects: Coarsening; Crystal defects; Deposition; Morphology; Photoconductivity; Photocurrent; Photoelectric effect; THIN films; ZINC oxide; Photoconductivity; THIN films; ZINC oxide
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.10.120

•ZnO thin filmswere deposited by pulsed laser ablation from a metallic zinc target in a controlled oxygen atmosphere in shock wave regime.•The samples morphology is tuned, varying the growth temperature.•The transport properties were measured at RT and at 30K under vacuumboth illuminating the sample by an UV laser and in dark conditions.•All samples are sensible to the UV radiations; the oxygen chemisorbed on the grain surface affects the speed of photoresponse.
The electrical transport properties of a set of zinc oxide (ZnO) thin films, prepared by pulsed laser ablation, were investigated at the temperatures of 30K and 300K. Information about the structural and morphological properties of the samples were obtained by means of atomic force microscopy (AFM) and X-ray diffraction (XRD). A significant variation in the surface morphology and photoresponse characteristics of the ZnO thin films were observed as a function of the deposition temperature. Upon increasing the deposition temperature, the surface topography changes from a more fine-grained to a more coarse-grained structure, showing a tetragonal wurtzite crystalline structure. Time resolved photocurrent measurements showed significantly variations as function of the observed samples morphologies. A photocurrent value of about three order of magnitude larger is observed for samples showing a more coarse-grained structure with respect to the fine-grained ones. Such a result is interpreted as due to the contributions of both “bulk” and defect centers that affect the conduction mechanisms and influence both the photoconductivity values and the photoresponse speed. The observed decay times are very long with respect to films grown by other techniques, due to the reduction of the surface localized centers of defect available for recombination. In this context, the sample morphology appears to be a key parameter to control the photoconductivity in ZnO thin films.