A variable-temperature scanning tunneling microscope capable of single-molecule vibrational spectroscopy

Abstract

The design and performance of a variable-temperature scanning tunneling microscope (STM) is presented. The microscope operates from 8 to 350 K in ultrahigh vacuum. The thermally compensated STM is suspended by springs from the cold tip of a continuous flow cryostat and is completely surrounded by two radiation shields. The design allows for in situ dosing and irradiation of the sample as well as for the exchange of samples and STM tips. With the STM feedback loop off, the drift of the tip–sample spacing is approximately 0.001 Å/min at 8 K. It is demonstrated that the STM is well-suited for the study of atomic-scale chemistry over a wide temperature range, for atomic-scale manipulation, and for single-molecule inelastic electron tunneling spectroscopy (IETS).

Magneto-quantum oscillations of the conductance of a tunnel point contact in the presence of a single defect

“…The amplitude of the oscillations (25) having de Haas-van Alphen period is proportional to the small parameter ( Ω/ε F ) 3/2 , which for H ∼ 0.1T is of the order of ∼ 10 −3 G c0 . Comparing this to previous STS experiments [26], where signal-to-noise ratios of 5 · 10 −4 (at 1 nA, 400 Hz sample frequency) have been achieved, it should be possible to observe the predicted conductance oscillations.…”

“…3 the full expression for the oscillatory part ∆G(H) of the conductance (the second term in Eq. (19)) is compared with the semiclassical approximation ∆G 1 (H, ρ 0 , z 0 ), Eq (26). The long period oscillation is a manifestation of the flux quantization effect and is well reproduced by the semiclassical approximation.…”

Nucleation of ordered Fe islands on Al2O3/Ni3Al(111)

“…1, 2(a) and 4 were done in Bonn using a homebuilt liquid helium cooled beetle type STM [18]. The main components of this low temperature (LT) STM are a copy of the original design by Stipe et al [19]. The two other STM images (Figs.…”

Low noise current-to-voltage converter and vibration damping system for a low-temperature ultrahigh vacuum scanning tunneling microscope

“…Very often, for operation at low temperature, external amplifiers are connected to the tunnel junction through at least 1 m of copper wire. 2 This connection picks up electromagnetic and mechanical noise due to temperature fluctuations and cryostat vibrations, but the most limiting factor is the drastic increase of the capacitance of the line. Therefore, reaching a bandwidth of few hundred Hz for tunnel currents in the range of pA is a challenge.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] For high-quality STM measurements, one has to be able to measure small currents, while reaching low-level tunnel current noise and a sufficient bandwidth. Therefore, the development of efficient current-voltage (I -V) converters is required.…”