Scientific Results

Ultrasonic force microscopy: Detection and imaging of ultra-thin molecular domains

Year: 2011

Authors: Dinelli F., Albonetti C., Kolosov O.V.

Autors Affiliation: CNR, Istituto Nazionale di Ottica(INO), via Moruzzi 1,56124 Pisa,Italy; CNR, Istituto Studio Materiali Nanostrutturati (ISMN), via Gobetti 101, 40129 Bologna, Italy; Department of Physics, Lancaster University, Lancaster LA14YB, UK

Abstract: The analysis of the formation of ultra-thin organic films is a very important issue. In fact, it is known that the properties of organic light emitting diodes and field effect transistors are strongly affected by the early growth stages. For instance, in the case of sexithiophene, the presence of domains made of molecules with the backbone parallel to the substrate surface has been indirectly evidenced by photoluminescence spectroscopy and confocal microscopy. On the contrary, conventional scanning force microscopy both in contact and intermittent contact modes have failed to detect such domains. In this paper, we show that Ultrasonic Force Microscopy (UFM), sensitive to nanomechanical properties, allows one to directly identify the structure of sub-monolayer thick films. Sexithiophene flat domains have been imaged for the first time with nanometer scale spatial resolution. A comparison with lateral force and intermittent contact modes has been carried out in order to explain the origins of the UFM contrast and its advantages. In particular, it indicates that UFM is highly suitable for investigations where high sensitivity to material properties, low specimen damage and high spatial resolution are required.

Journal/Review: ULTRAMICROSCOPY

Volume: 111 (4)      Pages from: 267  to: 272

More Information: The authors would like to thank Mauro Murgia for film preparation and acknowledge the use of Gwyddion for the treatment of the images [27]. FD and CA acknowledge the support from the CNR under the program Short term mobility in 2008 and 2009, respectively. OK acknowledge the support of EPSRC Grant EP/G017301/1.
KeyWords: scanning probe microscopy; ultrasonic force microscopy; organic conjugated molecules; sexithiophene; ultra-thin films
DOI: 10.1016/j.ultramic.2010.12.019

Citations: 13
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