Cleaning of tungsten tips for subsequent use as cold field emitters or STM probes

Author:

Košelová Zuzana12,Horáková Lenka3,Burda Daniel14,Allaham Mohammad M.14,Knápek Alexandr1,Fohlerová Zdenka2

Affiliation:

1. Institute of Scientific Instruments of the Czech Academy of Sciences , Královopolská 147 , Brno , Czech Republic

2. Department of Microelectronics , Brno University of Technology , Technologická 10 , Brno , Czech Republic

3. Institute of Materials Science , Brno University of Technology , Purkyňova 464 , Brno , Czech Republic

4. Department of Physics , Brno University of Technology , Technologická 8 , Brno , Czech Republic

Abstract

Abstract This study investigates the crucial process of cleaning cold field emission electron emitters and scanning tunnel microscopy (STM) probes, particularly focusing on tungsten tips. The cleanliness of these tips is essential for maintaining optimal cathode properties, preventing impurities that can significantly affect the emission process. Various cleaning methods, including macroetching, ammonia cleaning, and hydrofluoric acid (HF) cleaning were explored and compared by scanning electron microscopy. The macroetching method, involving a mixture of hydrochloric acid, nitric acid, and hydrogen fluoride, proved to be too reactive, causing significant material removal and altering the tip’s structure. Ammonia cleaning did not significantly improve or harm the samples. However, oxide islands appeared in some areas, suggesting the potential formation of ammonium tungsten oxide. HF cleaning, specifically at 20% and 50% concentrations, demonstrated effectiveness in removing tungsten oxides without damaging the tip. Pre-cleaning with water and ethanol proved beneficial for subsequent HF refinement. Results suggest that HF is the most suitable method for oxide removal but a rinse with water is essential for removing residual sodium hydroxide. To maintain optimal properties, it is crucial to apply a less reactive layer quickly or transfer the tips to a water/ethanol bath to prevent oxidation.

Publisher

Walter de Gruyter GmbH

Cited by 3 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Comparative analysis of surface layer functionality in STM and AFM probes: Effects of coating on emission characteristics;Journal of Electrical Engineering;2024-08-01

2. Scanning Enhancement of STM-tungsten Probes by Applying Colloidal Graphite Coatings;2024 37th International Vacuum Nanoelectronics Conference (IVNC);2024-07-15

3. From Deformation to Performance: WO3-Coated Tungsten Emitters Created by Anodization;2024 37th International Vacuum Nanoelectronics Conference (IVNC);2024-07-15

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