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

Libioulle, Laurent; Radenović, Aleksandra; Bystrenová, Eva; Dietler, Giovanni

doi:10.1063/1.1533100

Cited by 16 publications

(10 citation statements)

References 24 publications

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“…21 All components of the feedback electronics 22 have to be sufficiently high in bandwidth ͑including appropriately high slew rates͒ as well as sufficiently low in noise. 23 These conditions are conflicting, as the noise of electronic components usually increases with the bandwidth f bw proportional to ͱ f bw . In addition, one also needs a low-noise scan generator, a fast data acquisition system, and fast display of the measured data.…”

Section: Introductionmentioning

confidence: 99%

Scanning probe microscopes go video rate and beyond

Rost¹,

Crama

Schakel

et al. 2005

Review of Scientific Instruments

217

144

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In this article we introduce a, video-rate, control system that can be used with any type of scanning probe microscope, and that allows frame rates up to 200 images/ s. These electronics are capable of measuring in a fast, completely analog mode as well as in the more conventional digital mode. The latter allows measurements at low speeds and options, such as, e.g., atom manipulation, currentvoltage spectroscopy, or force-distance curves. For scanning tunneling microscope ͑STM͒ application we implemented a hybrid mode between the well-known constant-height and constant-current modes. This hybrid mode not only increases the maximum speed at which the surface can be imaged, but also improves the resolution at lower speeds. Acceptable image quality at high speeds could only be obtained by pushing the performance of each individual part of the electronics to its limit: we developed a preamplifier with a bandwidth of 600 kHz, a feedback electronics with a bandwidth of 1 MHz, a home-built bus structure for the fast data transfer, fast analog to digital converters, and low-noise drivers. Future improvements and extensions to the control electronics can be realized easily and quickly, because of its open architecture with its modular plug-in units. In the second part of this article we show our high-speed results. The ultrahigh vacuum application of these control electronics on our ͑UHV͒-STM enabled imaging speeds up to 0.3 mm/ s, while still obtaining atomic step resolution. At high frame rates, the images suffered from noticeable distortions, which we have been able to analyze by virtue of the unique access to the error ͑dZ͒ signal. The distortions have all been associated with mechanical resonances in the scan head of the UHV-STM. In order to reduce such resonance effects, we have designed and built a scan head with high resonance frequencies ͑ജ64 kHz͒, especially for the purpose of testing the fast electronics. Using this scanner we have reached video-rate imaging speeds up to 200 frames/ s ͑5 ms/ image͒, while still obtaining atomically resolved structures.

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Section: Introductionmentioning

confidence: 99%

Scanning probe microscopes go video rate and beyond

Rost¹,

Crama

Schakel

et al. 2005

Review of Scientific Instruments

217

144

View full text Add to dashboard Cite

show abstract

“…Dilution refrigeration is unique in providing a cold point stable in time that can cool down large devices to temperatures which are one or two orders of magnitude below 1 K. The environment of dilution refrigeration is, however, rather inadequate for STM, due to the vibrations usually associated to its operation [159][160][161][162]. Some improvements in the cryogenics have been proposed, such as eliminating the 1 K pot bubbling [156,163], by substituting it with a capillary or by using a large 1 K pot which can be closed using a needle valve. But mechanical vibrations remain unavoidable in operating a STM in a dilution refrigerator, and they lead to changes in the position of the probe with respect to the sample.…”

Section: Design and Constructionmentioning

confidence: 99%

“…Typical current noise levels correspond to height changes of the order of the pm. Vibrations should be of the order or below this value [163,167]. The resonant frequency of the STM head should be as large as possible, and the one of the supporting assembly as low as possible.…”

Section: Design and Constructionmentioning

confidence: 99%

Imaging superconducting vortex cores and lattices with a scanning tunneling microscope

Suderow¹,

Guillamón²,

Rodrigo³

et al. 2014

Supercond. Sci. Technol.

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Abstract. The observation of vortices in superconductors was a major breakthrough in developing the conceptual background for superconducting applications. Each vortex carries a flux quantum, and the magnetic field radially decreases from the center. Techniques used to make magnetic field maps, such as magnetic decoration, give vortex lattice images in a variety of systems. However, strong type II superconductors allow penetration of the magnetic field over large distances, of order of the magnetic penetration depth λ. Superconductivity survives up to magnetic fields where, for imaging purposes, there is no magnetic contrast at all. Static and dynamic properties of vortices are largely unknown at such high magnetic fields. Reciprocal space studies using neutron scattering have been employed to obtain insight into the collective behavior. But the microscopic details of vortex arrangements and their motion remain difficult to obtain. Direct real space visualization can be made using scanning tunneling microscopy and spectroscopy (STM/S). Instead of using magnetic contrast, the electronic density of states describes spatial variations of the quasiparticle and pair wavefunction properties. These are of order of the superconducting coherence length ξ, which is much smaller than λ. In principle, individual vortices can be imaged using STM up to the upper critical field where vortex cores, of size ξ, overlap. In this review, we describe recent advances in vortex imaging made with scanning tunneling microscopy and spectroscopy. We introduce the technique and discuss vortex images which reveal the influence of the Fermi surface distribution of the superconducting gap on the internal structure of vortices, the collective behavior of the lattice in different materials and conditions, and the observation of vortex lattice melting. We consider challenging lines of work, which include imaging vortices in nanostructures, multiband and heavy fermion superconductors, single layers and van-der-Waals crystals, studying current driven dynamics and the liquid vortex phases.

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“…61,62 The measured noise level for this homebuilt part is 0.6 pA rms. The feedback loop controller can stabilize a current as low as 1 pA.…”

Section: Appendix Amentioning

confidence: 99%