(a) Schematic of the homebuilt STM: A. GeckoDrive, B. overall frame, C. sapphire interface, D. tip, E. string strip, F. channel for wires, G. sample, H. sample stage. (b) Exploded view of the scanning unit of the STM: I. scanning part, J. sapphire ball, K. rail, L. piezo tube scanner, M. tip holder, N. sapphire base, O. sapphire tube, P. string strip, Q. rail cover. (c) Photo of the STM: R. pre-amplifier circuit box, S. power switch, T. connectors.
Block diagram of the STM control system, in which AO and AI stand for analog output and analog input, respectively, and pre-amplifier output is the measured tunneling current.
Raw data constant height STM images of the HOPG sample taken under the condition of “with vibration and sound isolations.” The sample was scanned at room temperature and in air with 100 mV sample-positive bias voltage. The scan ranges are (a) 177 Å × 177 Å, (b) 37.5 Å × 37.5 Å, (c) 18.3 Å × 18.3 Å, and (d) 9 Å × 9 Å.
Measured tunneling current vs. inner electrode voltage of PTS: (a) as well as vs. bias voltage (b). The inset in (a) is plotted in semi-log scale.
(a) Photo of the setup when taking images under the condition of “without vibration and sound isolation”: A. sound-isolated box on a vibration damped table mentioned in Ref. 18 , showing that the STM was not vibration and sound isolated; B. sound isolation materials; C. control circuit boxes; D. ground of the fifth floor; E. STM cover for electromagnetic shielding. (b) Vibration spectra, (c) tunneling current spectra, and (d) FFT spectra of tunneling current taken under Measurement-condition I and Measurement-condition II which correspond to without and with vibration and sound isolations, respectively. (e) Raw data constant height STM image of the HOPG sample taken under the condition of “without vibration and sound isolations.” The sample was scanned at room temperature and in air with 100 mV sample-positive bias voltage. The scan range is 44.6 Å × 44.6 Å. (f) Duplication of Fig. 3(b) . Notes: The upper plot of (e) and (f) are the cross-sectional tunneling current profiles corresponding to the lines shown in the atoms images, and the lower are the frequency spectra of these profiles. The insets are given the fast Fourier transforms of these two images.
Images taken under the conditions of coarse approach motor touching (a) and being detached from (b) the scanner, respectively. (c) Tunneling current spectra, and (d) FFT spectra of tunneling current where I and II stand for these two conditions, respectively.
Spiral-scanned raw data STM images of a HOPG sample taken at varying scan rates. (a) Scan rate = 250 s/image. (b) Scan rate = 166.7 s/image. (c) Scan rate = 125 s/image.
Drift data in XY and Z directions and their linear fitting.
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