http://amoprotemics.wordpress.com/2013/08/
About the author
Michael Nagel received his PhD from the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen University, Germany, in 2003. During his thesis, he developed the world-wide first label-free DNA sensor-chip utilizing THz range frequencies [1]. From 2004 he worked as a chief engineer at the Institute of Semiconductor Electronics, RWTH Aachen, where he initiated and led applied and fundamental research projects focusing on Terahertz technology development. Since 2011 he is working at AMO GmbH, Aachen (Germany), with a focus on Terahertz research and technology transfer.
He has authored or co-authored over 120 publications and international conference presentations with more than 1600 citations and filed eight patents [2].
[1] M. Nagel, P. Haring Bolivar, M. Brucherseifer, H. Kurz, A. Bosserhoff, and R. Büttner, “Integrated THz technology for label-free genetic diagnostics,” Appl. Phys. Lett. 80, 154 (2002).
[2] http://scholar.google.com.au/citations?user=TFpoYn8AAAAJ&hl=de
Impressum
The following is the first post from April of this year.
Touch-screen displays are still among the most expensive parts in a mobile device. The replacement of indium tin oxide (ITO) which is used as optically transparent conduction layer by Graphene is widely considered as a promising route to lower the costs of this component. Being better suited for future flexible touch-screens is a further advantage of Graphene against ITO. However, a hitherto existing problem is given by the lack of suitable measurement tools for the quality and process analysis of large-scale graphene layers. Photoconductive (PC) Terahertz microprobes developed at AMO GmbH (Aachen, Germany) have now proved as a key component for contact-free high-resolution mapping of graphene layer sheet conductance [1]. In comparison to standard contact-based four-point probing up to 1000-fold increased measurement speed (5 ms/pixel) has already been achieved.
The microprobes are used as THz near-field detectors triggered by femtosecond laser pulses for the spatially resolved mapping of pulsed THz radiation transmitted through the device under test. Absolute sheet conductivity values can be directly determined from the obtained transmission data.
In contrast to earlier diffraction-limited THz transmission systems [2, 3] – the new microprobe-equipped system is able to achieve substantially higher (deep sub-wavelength) resolution as required for the inspection of the typically micro-structured graphene layers in touch screen devices. At the same time the measurement area size can be freely selected from small cut-outs to full display mappings.
In addition to sheet conductivity mappings the microprobes are also used for further analytic applications on active graphene-based devices as they have already been applied for THz emission measurements at optically excited graphite and graphene samples [4].
[1] http://www.amo.de/thz_tip.0.html?&L=1&L=2
[2] J. L. Tomaino et al. , “Terahertz imaging and spectroscopy of large-area single-layer graphene,“ Opt. Express, 19, 1, 141-146 (2011)
[3] J. D. Buron, D. H. Petersen, P. Bøggild, D. G. Cooke, M. Hilke, J. Sun, E. Whiteway, P. F. Nielsen, O. Hansen, A. Yurgens, and P. U. Jepsen, “Graphene Conductance Uniformity Mapping,” Nano Lett. 12 (10), 5074–5081 (2012).
[4] M. Nagel, A. Michalski, T. Botzem, and H. Kurz, “Near-field investigation of THz surface-wave emission from optically excited graphite flakes,“ Opt. Express 19 (5), 4667-4672 (2011).
He has authored or co-authored over 120 publications and international conference presentations with more than 1600 citations and filed eight patents [2].
[1] M. Nagel, P. Haring Bolivar, M. Brucherseifer, H. Kurz, A. Bosserhoff, and R. Büttner, “Integrated THz technology for label-free genetic diagnostics,” Appl. Phys. Lett. 80, 154 (2002).
[2] http://scholar.google.com.au/citations?user=TFpoYn8AAAAJ&hl=de
Impressum
The following is the first post from April of this year.
TERAHERTZ MICROPROBES: Efficiently fostering the development of Graphene-based touch-screen displays
Reply
Touch-screen displays are still among the most expensive parts in a mobile device. The replacement of indium tin oxide (ITO) which is used as optically transparent conduction layer by Graphene is widely considered as a promising route to lower the costs of this component. Being better suited for future flexible touch-screens is a further advantage of Graphene against ITO. However, a hitherto existing problem is given by the lack of suitable measurement tools for the quality and process analysis of large-scale graphene layers. Photoconductive (PC) Terahertz microprobes developed at AMO GmbH (Aachen, Germany) have now proved as a key component for contact-free high-resolution mapping of graphene layer sheet conductance [1]. In comparison to standard contact-based four-point probing up to 1000-fold increased measurement speed (5 ms/pixel) has already been achieved.
Fig. 1: (a) THz microprobe tip-structure (b) Measurement data example taken from a sheet conductance sample study conducted for Samsung Techwin, South Korea. The plot is showing the sheet conductivity of a structured Graphene layer.
In contrast to earlier diffraction-limited THz transmission systems [2, 3] – the new microprobe-equipped system is able to achieve substantially higher (deep sub-wavelength) resolution as required for the inspection of the typically micro-structured graphene layers in touch screen devices. At the same time the measurement area size can be freely selected from small cut-outs to full display mappings.
In addition to sheet conductivity mappings the microprobes are also used for further analytic applications on active graphene-based devices as they have already been applied for THz emission measurements at optically excited graphite and graphene samples [4].
[1] http://www.amo.de/thz_tip.0.html?&L=1&L=2
[2] J. L. Tomaino et al. , “Terahertz imaging and spectroscopy of large-area single-layer graphene,“ Opt. Express, 19, 1, 141-146 (2011)
[3] J. D. Buron, D. H. Petersen, P. Bøggild, D. G. Cooke, M. Hilke, J. Sun, E. Whiteway, P. F. Nielsen, O. Hansen, A. Yurgens, and P. U. Jepsen, “Graphene Conductance Uniformity Mapping,” Nano Lett. 12 (10), 5074–5081 (2012).
[4] M. Nagel, A. Michalski, T. Botzem, and H. Kurz, “Near-field investigation of THz surface-wave emission from optically excited graphite flakes,“ Opt. Express 19 (5), 4667-4672 (2011).
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