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E newsletter March 2007 nº 7 http://www.phantomsnet.net Nanometrology at the nanoscale Nanotechnology: applications and social implications Molecular switches: Isomerization of single azobenzene derivates STM imaging of molecules on a thin insulating film High resolution imaging of electronic and molecular structures assembled on InSb(001) c(8x2) surface with LT-STM Contents/Editorial E newsletter Editorial Information 3 Research Nanometrology at the nanoscale 5 E. Prieto Nanotechnology: applications and social implications 8 A. Correia, M. Pérez , J. J. Sáenz and P. A. Serena NANO Vacancies 18 NANO Conferences 20 NANO News 21 Pico-Inside Integrated Project Molecular switches: Isomerization of single azobenzene derivates 22 L. Grill, M. Alemani, K.-H. Rieder, F. Moresco, M. V. Peters and S. Hecht STM imaging of molecules on a thin insulating film 24 C. J. Villagomez Ojeda, S. Gauthier, A. Gourdon, S. Stojkovic and C. Joachim High resolution imaging of electronic and molecular structures assembled on InSb(001) c(8x2) surface with LT-STM 28 G. Goryl, S. Godlewski, J.J. Kolodziej and M. Szymonski Dear Readers: Deadline for manuscript submission: Issue nº08: May 01, 2007 Nanotechnology has become a rapidly growing research Issue nº09: July 01, 2007 and development field that is cutting across many tradi- tional boundaries. Given its multidisciplinary character, the list of potential applications is very long. Depósito Legal: M-43078-2005 This E-Nano newsletter issue is therefore dedicated to Editorial Board: Adriana Gil (Nanotec SL, Spain), Christian present a review on the applications and social implica- Joachim (CEMES-CNRS, France), Ron Reifenberger tions of Nanotechnology but also provide insights on the (Purdue University, USA), Stephan Roche (CEA-DRFMC, quantitative determination of dimensions (metrology) and France), Juan Jose Saenz (UAM, Spain), Pedro A. Serena other properties of nanostructures, crucial in R&D and (ICMM-CSIC, Spain), Didier Tonneau (CRMC2-CNRS, also in industrial processes. France), Rainer Waser (Research Center Julich, Germany) We would like to thank all the authors who contributed to For any question please contact the editor at: this issue as well as the European Union (FET/NANO- antonio@phantomsnet.net ICT) and the Pico-Inside Integrated Project for their close collaboration. EDITORIAL INFORMATION E newsletter nº7 March 2007 Dr. Antonio Correia Published by PHANTOMS Foundation (Spain) E newsletter Editor Editor: Dr. Antonio Correia PHANTOMS Foundation PHANTOMS Foundation antonio@phantomsnet.net Assistant Editor: Jose Luis Roldan PHANTOMS Foundation jlroldan@phantomsnet.net 1500 copies of this issue have been printed www.phantomsnet.net E newsletter March 2007 3 Research Metrology at the nanoscale to the realization of the metre and the retrorreflected di- E. Prieto ffraction order sent by a beamsplitter through a focusing Centro Español de Metrología (CEM), Alfar 2, Tres Cantos, 28760 lens to a CCD video camera acting as a null-position Madrid, Spain detector because its many advantages on the typical four- The quantitative determination of dimensions and other properties of micro and nanostructures is crucial in R&D and also in industrial proce- sses control. Understanding physical and chemical properties of stru- ctures at the nanoscale is in most cases directly linked to the knowledge of their critical dimensions. SPMs are widely used for nanometre scale characterizations but quanti- tative measurements are only possible by using traced instruments, together with suitable calibration artefacts and right measurement proce- dures. The most accurate way to perform traceable measurements with SPMs is to convert them in metrological ones by integrating 3D interferometric measurement systems. Some traceable atomic force microscopes (AFM) have been developed in last years by National Institutes of Metrology along with novel methods and standards for their calibration. Evaluating and quantifying the interaction between tip and sample, in order to differentiate features not belonging to the object under study and the design of new probes able to measure at sidewalls of nano- and Figure 1: Schematic drawing of the NRC imaging diffractometer micro-structures represent interesting contributions aimed to characte- setup. rize accurately any kind of feature. quadrant photodetectors [3]. The idea of using coordinate measuring machines (CMMs) at the nanoscale has also expanded and CMMs have become versatile and But the most accurate way to perform traceable measure- widespread metrology tools, after improving their metrological design, ments with SPMs is to convert them in metrological ones minimizing ulterior corrections, and developing specific software to se- by integrating 3D interferometric measurement systems to parate errors coming from different sources. follow the scanner/tip position along with means to elimi- Most of the efforts we are observing in instrumentation, calibration and measurement methods are directly motivated by the need of fulfilling the nate the scanner and Abbe errors [4-7]. continuously narrower manufacturing requirements as those stated, for Some traceable atomic force microscopes (AFM) have instance, in the International Technology Roadmap for Semiconductors, been developed by National Institutes of Metrology in the where many of the figures are not reachable yet because they are last years [8-10], along with novel methods for their cali- depending on new measurement capabilities, not yet fully developed. bration. Some of these 'metrological AFMs' claim to reach Keywords: nanoscale, nanostructures, critical dimen- measurement uncertainties of 1 nm (Figure 2) [11]. sions, SPM, AFM, metrology, traceability, calibration. The quantitative determination of the properties of micro and nanostructures is essential in R&D and also in indus- trial processes control and quality assurance. Knowledge of the geometrical dimensions of structures is, in most cases, the base for understanding other physical and chemical properties [1]. As in the macro world, also at the nanometre scale all quantitative dimensional and geometrical measurements should be traceable to the definition of the metre. This means to follow an unbroken chain of comparisons with stated uncertainties (the traceability chain) in order to link the actual measurements to the highest point of the metro- logical pyramid, the meter, normally realized by a stabi- lized laser or, more recently, by femtosecond frequency combs linking the metre and the second [2]. Figure 2: The traceable AFM developed at NMi-VSL consists of SPMs are widely used for nanometre scale characteriza- a scanning stage (SS), an invar metrology frame (MF) with a 3D tions but as indicated above quantitative measurements laser interferometer and an AFM head (AH). are only possible by using traced instruments, together with suitable calibration artefacts and right measurement Even with these metrological instruments, it is important to procedures. So, there is a real need of moving to tra- evaluate and quantify the interaction between tip and ceable atomic force microscopes (AFM). This can be sample, in order to differentiate between the features of made by interferometric calibration of the scales of the the object and those caused by the interaction, due to AFM or by using calibrated grids as transfer standards. affecting factors as bending and twisting of the cantilever, One of the possible ways to calibrate grids is using a laser friction, humidity and surface forces. diffraction setup (Figure 1) composed by a precision Some of these interactions have been studied with the rotary table, the sample grating mounted in Littrow confi- help of a modified microscope [12] with added optical fibre guration, a collimated spatially filtered laser source linked and homodyne differential interferometers, able to mea- sure the movement of the cantilever and detect residual www.phantomsnet.net E newsletter March 2007 5 Research movements together with the vertical displacement beams come back to detectors after being further reflec- between the cantilever holder and the sample (Figure 3). ted by other surfaces, as shown in Figure 5, leading to wrong measurement results [15]. Figure 5: Difficulties encountered by conventional measure- ment techniques during sidewall profiling. In order to solve major limitations of conventional AFM probes, novel Assembled Cantilever Probes (ACP), appli- cable for direct and non-destructive sidewall measure- ments of nano and micro-structures have been developed Figure 3: Photograph of the AFM developed by NPL and PTB to [15]. study tip–sample interactions Considering the advantages of combining scanning probe microscopy with X-ray interferometry [13] such AFM has been designed so that it can also be mounted over the X- ray interferometer developed in the COXI project [14]. The X-ray interferometer would then be used as a one-dimen- sional translation stage for scans that require high resolu- tion, making displacements traceable to the definition of the metre, in discrete steps of 0.192 nm, the lattice spa- cing of the (2 2 0) planes in silicon. Figure 6: Schematic diagram illustrating the versatile structures of ACPs. Figure 7: Micrograph of an ACP taken using a scanning elec- tron microscope. Figure 4: Combined optical and X-ray interferometer (COXI) Project, NPL/PTB/INRIM. Another kind of instruments originated in the macro world but used now in nanometrology, because the new New developments also occupy on solving specific pro- demands