Simplified feedback control system for scanning tunneling microscopy
Francisco Martín-Vega, Víctor Barrena, Raquel Sánchez-Barquilla, Marta Fernández-Lomana, José Benito Llorens, Beilun Wu, A. Fente, David Perconte, Ignacio Horcas, Raquel López, Javier G. Blanco, Juan Antonio Higuera, Samuel Mañas‐Valero, Na Hyun Jo, Juan Schmidt, P. C. Canfield, Gabino Rubio‐Bollinger, J. G. Rodrigo, Edwin Herrera, Isabel Guillamón, Hermann Suderow
Abstract
A Scanning Tunneling Microscope (STM) is one of the most important scanning probe tools available to study and manipulate matter at the nanoscale. In a STM, a tip is scanned on top of a surface with a separation of a few Å. Often, the tunneling current between the tip and the sample is maintained constant by modifying the distance between the tip apex and the surface through a feedback mechanism acting on a piezoelectric transducer. This produces very detailed images of the electronic properties of the surface. The feedback mechanism is nearly always made using a digital processing circuit separate from the user computer. Here, we discuss another approach using a computer and data acquisition through the universal serial bus port. We find that it allows successful ultralow noise studies of surfaces at cryogenic temperatures. We show results on different compounds including a type II Weyl semimetal (WTe2), a quasi-two-dimensional dichalcogenide superconductor (2H–NbSe2), a magnetic Weyl semimetal (Co3Sn2S2), and an iron pnictide superconductor (FeSe).