Paper NS-ThA6
Advancing QPlus AFM Performance at 5K Towards Lower Oscillation Amplitudes and Higher Frequencies

Thursday, November 12, 2009, 3:40 pm, Room L

The QPlus sensor with its high spring constant and an optimized quality factor allows operation at very small oscillation amplitudes and is therefore ideal for atomically resolved imaging on all types of surfaces, i.e. for insulators, semiconductors and also for metallic surfaces. We have integrated the QPlus technology into an established low temperature STM platform. The extremely low signal of the QPlus sensor due to small oscillation amplitudes requires the first amplification stage to be very close to the sensor, i.e. it has to be compatible with low temperatures.

We present atomic resolution imaging on single crystal NaCl(100) with oscillation amplitudes below 100 pm_pp (peak to peak) and operation at higher flexural modes at frequencies of up to 318 kHz in constant df imaging feedback at 5K. We also present atomic resolution measurements on metallic Au(111) and Ag(111) surfaces with an extremely high stability at 5 K [1]. On a reconstructed Si(111) 7x7 surface further investigations in a temperature range between 50 K and 1070 K demonstrate the capability of the QPlus sensor for ultimate resolution in pure NC-AFM and dynamic STM measurements. At low temperatures, atomically resolved images of the rest atom layer will be presented. High temperature measurements close to the phase transition between the (1x1) and (7x7) show dynamics in the formation of step edges and kinks.

[1] A. Bettac, J. Koeble, K. Winkler, B. Uder, M. Maier, and A. Feltz, Nanotechnology, in print