Tip preparation for usage in an ultra-low temperature UHV scanning tunneling microscope (original) (raw)
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Fabrication of [001]-oriented tungsten tips for high resolution scanning tunneling microscopy
Scientific reports, 2014
The structure of the [001]-oriented single crystalline tungsten probes sharpened in ultra-high vacuum using electron beam heating and ion sputtering has been studied using scanning and transmission electron microscopy. The electron microscopy data prove reproducible fabrication of the single-apex tips with nanoscale pyramids grained by the {011} planes at the apexes. These sharp, [001]-oriented tungsten tips have been successfully utilized in high resolution scanning tunneling microscopy imaging of HOPG(0001), SiC(001) and graphene/SiC(001) surfaces. The electron microscopy characterization performed before and after the high resolution STM experiments provides direct correlation between the tip structure and picoscale spatial resolution achieved in the experiments.
e-Journal of Surface Science and Nanotechnology, 2007
We present a method to prepare tungsten tips for use in multi-tip scanning tunneling microscopes. The motivation behind the development comes from a requirement to make very long and conical-shape tips with controlling the cone angle. The method is based on a combination of a "drop-off" method and dynamic electrochemical etching, in which the tip is continuously and slowly drawn up from the electrolyte during etching. Its reproducibility was confirmed by scanning electron microscopy. Comparison in tip shape between the dynamic and static methods was shown.
Physical Review B, 2005
Detailed knowledge of the tip apex structure is necessary for quantitative comparison between theory-based simulations and experimental observations of tip-substrate interactions in scanning probe microscopy ͑SPM͒. Here, we discuss field ion microscopy ͑FIM͒ techniques to characterize and atomically define SPM tungsten tips. The tip radius can be estimated from field emission data, while FIM imaging allows the full atomic characterization of the tip apex. We find that when FIM is applied to tips with a radius of a few nanometers ͑as is desirable for high-resolution atomic force microscopy imaging͒, limitations not apparent with less sharp tips arise; successful resolution of these limitations will extend the utility of FIM. Field evaporation can be used to atomically engineer the apex into a desired atomic configuration. Starting from a W͑111͒ wire, a tip terminating in three atoms can reproducibly be fabricated; due to its geometry and stability, this apex configuration is well suited for application as an atomically defined electrical contact in SPM experiments aimed at understanding contact mechanics at the atomic scale.
Preparation and characterization of electrochemically etched W tips for STM
Measurement Science and Technology, 1999
Abstract. We have investigated methods for cleaning dc-etched polycrystalline tungsten tips for scanning tunnelling microscopy (STM). The cleaning methods include Ar-ion sputtering, heating, chemical treatments and Ne-ion self-sputtering. We correlate transmission electron microscopy images of the tip, field-emission data from the tip and images of a clean Cu (111) surface to find an optimum procedure for STM imaging. Clean and sharp tips are made by sputtering, combined with careful heating by electron bombardment. We found that ...
Ultrasharp tungsten tips—characterization and nondestructive cleaning
Ultramicroscopy, 2012
We study the treatment of ultrasharp tungsten tips used for applications in nanoscience and introduce a fast and simple method for estimation of the tip radius using a single measurement of the autoemission current. The method is based on a detailed investigation of the influence of an arrangement of electrodes on the electric field layout in close proximity of the tip apex. The electric field was calculated using Monte Carlo Floating Random Walk algorithm. The most frequently used cleaning procedures (heating the whole tip to high temperature, electron bombardment and selfsputtering) were investigated by electrical measurements and microscopy techniques (SEM, TEM) and the results of the particular methods are compared. We report on the effectiveness and limiting conditions of the cleaning methods with respect to the damage they cause to the tip apex.