AVS 53rd International Symposium
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoM

Paper NS-MoM4
QPlus Sensor AFM at Low Temperatures with Atomic Resolution on NaCl

Monday, November 13, 2006, 9:00 am, Room 2016

Session: Nanoscale Imaging Techniques
Presenter: M. Maier, Omicron NanoTechnology GmbH, Germany
Authors: A. Bettac, Omicron NanoTechnology GmbH, Germany
M. Maier, Omicron NanoTechnology GmbH, Germany
M. Wittmann, Omicron NanoTechnology GmbH, Germany
A. Feltz, Omicron NanoTechnology GmbH, Germany
T. Berghaus, Omicron NanoTechnology GmbH, Germany
Correspondent: Click to Email
Over many years, low temperature STM has been established as an advanced imaging and spectroscopy tool in various scientific fields. However, the creation and investigation of nano-structures on insulating surfaces gains more and more interest an thus push AFM as an alternative and complementary imaging technique. Ideally, the used AFM probe should simultaneously or alternatively work in STM and STS modes. Based on a proven LT STM platform, we have integrated a Qplus@footnote 1,2@ sensor for atomic resolution AFM while maintaining ease of use and level of STM performance. Especially at low temperatures and related spatial constraints, this self-sensing AFM technique is an ideal alternative to cantilever based optical detection. The QPlus sensor@footnote 1,2@ employs a quartz tuning fork for force detection in non-contact AFM operation mode. One prong of the tuning fork is fixed while the SPM probe tip is mounted to the second prong. It thus acts as a quartz lever transforming it's oscillation into an electrical signal as a result of the piezo-electric effect. The feedback signal is based on frequency shift originating from tip-sample force interaction. A dedicated pre-amplification technique ensures distance control based on the pure vibrational signal. In addition, extremely low signals require the first amplification stage to be very close to the sensor, i.e. to be compatible with low temperatures. Measurements on Si(111) 7x7 show that tunnelling current and vibrational signal are clearly separated. In addition, benchmark measurements on NaCl with a typical corrugation of approx. 10pm prove that resolution on insulation samples is competitive to best cantilever based AFM results. @FootnoteText@ @footnote 1@ Franz J. Giessibl, Appl. Phys. Lett. 73, 3956 (1998)@footnote 2@ Franz J. Giessibl, Appl. Phys. Lett. 76, 1470 (1998).