Effects of HF attack on the surface and interface microchemistry of W tips for use in the STM microscope: a scanning Auger microscopy (SAM) study (original) (raw)
Related papers
Reproducible Electrochemical Etching of Tungsten Probe Tips
Nano Letters, 2002
An electrochemical procedure in KOH electrolyte has been developed to reproducibly produce ∼5 nm radius tungsten probe tips. It has been found that a spurious electrochemical etching process, driven by the natural potential difference between an Ir electrode and the W tip, causes rapid tip blunting at the end of the electrochemical etching period. By electrically reversing this potential difference within 500 ns following tip separation, the blunting process is eliminated yielding sharp tips with varying cone angles.
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.
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.
International Journal of Scientific and Research Publications (IJSRP), 2020
One of the great challenges of Scanning Tunneling Microscopy (STM) is the production of atomically sharp tips. Tungsten tips in Scanning Probe Microscope (SPM) and Atomic Force Microscope (AFM) are used instead of platinum and iridium (Pt/Ir) tips due to their high quality factor, mechanical stability and produced at low cost. In this work we carried out different experiments on 0.5 mm (0.02 inch) tungsten wire and obtained sharp and reproducible tungsten tips by simple electrochemical etching "Drop-Off" method and we have shown that tips reproduced have better properties i.e. tip diameter and cone angle than earlier. Moreover tips reproducibility is checked by selecting a sample or two from produced tips and experimental work is repeated to show whether the procedure is reproducible or not and as shown that tips production procedure is reproducible by analyzing them, so have best control on tip shape and optimized etching conditions are reported. Similarly tips are produced by varying different voltages and maintaining various concentration of solution constant i.e. 2 molar, 3 molar and 4 molar NaOH concentration of solution and comparison is made between different tips by measuring their cone angle and tip diameter from SEM and OM images. Cone angle and tip diameter are measured from SEM and OM images by using AutoCAD software whose procedure are shown below at experimental work. Finally we have produced atomically sharp tungsten tips by analyzing optical microscope (OM) images and scanning electron microscope (SEM) images and have recommended the optimum one to be used in SPM.
Field ion microscope evaluation of tungsten nanotip shape using He and Ne imaging gases
Ultramicroscopy, 2012
Field ion microscopy (FIM) using neon imaging gas was used to evaluate a W(111) nanotip shape during a nitrogen assisted etching and evaporation process. Using appropriate etching parameters a narrow ring of atoms centered about the tip axis appears in a helium generated image. Etching of tungsten atoms continues exclusively on the outside of this well-defined ring. By replacing helium imaging gas with neon, normally inaccessible crystal structure of a tip apex is revealed. Comparison of the original W(111) tip (before etching) and partly etched tip shows no atomic changes at the tip apex revealing extraordinarily spatially selective etching properties of the etching process. This observation is an important step towards a detailed understanding of the nitrogen assisted etching and evaporation process and will lead to better control over atomically defined tip shapes.
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.
Microscopic investigations of chemo-mechanical polishing of tungsten
Thin Solid Films, 2004
The influence of aqueous solutions of KNO , KClO , and KIO on tungsten surfaces has been investigated in terms of the 3 3 3 degree of surface oxidation, metal dissolution and interfacial friction. The surface properties of tungsten films have been measured ex-situ with X-ray photoelectron spectroscopy and in situ with atomic force microscopy. Measurements of the surface composition reveal a greater degree of oxidation for surfaces treated in solutions of KIO in comparison to the other solutions. This increase 3 in surface oxidation is correlated to a greater rate of localized film dissolution that occurs under the action of the scanning probe tip. In turn, the process of material removal is the predominant origin of the higher interfacial friction measured at tungsten surfaces immersed in KIO solutions, as compared to KClO and KNO solutions. Collectively, these measurements portray a 3 3 3 fundamental pathway of material removal at tungsten surfaces in the presence of oxidizing species and highlight complementary roles of chemical and mechanical action. ᮊ