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Register a new userAntiferromagnetic MnNi tips for spin-polarized scanning probe microscopy
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Added by
Fabian Donat Natterer
Publication date
2018
fields
Physics
and research's language is
English
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Spin-polarized scanning tunneling microscopy (SP-STM) measures tunnel magnetoresistance (TMR) with atomic resolution. While various methods for achieving SP probes have been developed, each is limited with respect to fabrication, performance, and allowed operating conditions. In this study, we present the fabrication and use of SP-STM tips made from commercially available antiferromagnetic $rm{Mn_{88}Ni_{12}}$ foil. The tips are intrinsically SP, which is attractive for exploring magnetic phenomena in the zero field limit. The tip material is relatively ductile and straightforward to etch. We benchmark the conventional STM and spectroscopic performance of our tips and demonstrate their spin sensitivity by measuring the two-state switching of holmium single atom magnets on MgO/Ag(100).
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A simple, reliable method for preparation of bulk Cr tips for Scanning Tunneling Microscopy (STM) is proposed and its potentialities in performing high-quality and high-resolution STM and Spin Polarized-STM (SP-STM) are investigated. Cr tips show atomic resolution on ordered surfaces. Contrary to what happens with conventional W tips, rest atoms of the Si(111)-7x7 reconstruction can be routinely observed, probably due to a different electronic structure of the tip apex. SP-STM measurements of the Cr(001) surface showing magnetic contrast are reported. Our results reveal that the peculiar properties of these tips can be suited in a number of STM experimental situations.
We report the development of a scanning force microscope based on an ultra-sensitive silicon nitride membrane transducer. Our development is made possible by inverting the standard microscope geometry - in our instrument, the substrate is vibrating and the scanning tip is at rest. We present first topography images of samples placed on the membrane surface. Our measurements demonstrate that the membrane retains an excellent force sensitivity when loaded with samples and in the presence of a scanning tip. We discuss the prospects and limitations of our instrument as a quantum-limited force sensor and imaging tool.
Reduction of the inter-probe distance in multi-probe and double-tip STM down to the nanometer scale has been a longstanding and technically difficult challenge. Recent multi-probe systems have allowed for significant progress by achieving distances of around 30 nm using two individually driven, traditional metal wire tips. For situations where simple alignment and a fixed separation can be advantageous, we here present the fabrication of on-chip double-tip devices that incorporate two mechanically fixed gold tips with a tip separation of only 35 nm. We utilize the excellent mechanical, insulating and dielectric properties of high quality SiN as a base material to realize easy-to-implement, lithographically defined and mechanically stable tips. With their large contact pads and adjustable footprint these novel tips can be easily integrated with most existing commercial combined STM/AFM systems.
In recent years, self-assembled semiconductor nanowires have been successfully used as ultra-sensitive cantilevers in a number of unique scanning probe microscopy (SPM) settings. We describe the fabrication of ultra-low dissipation patterned silicon nanowire (SiNW) arrays optimized for scanning probe applications. Our fabrication process produces, with high yield, ultra-high aspect ratio vertical SiNWs that exhibit exceptional force sensitivity. The highest sensitivity SiNWs have thermomechanical-noise limited force sensitivity of $9.7pm0.4~text{aN}/sqrt{text{Hz}}$ at room temperature and $500pm20~text{zN}/sqrt{text{Hz}}$ at 4 K. To facilitate their use in SPM, the SiNWs are patterned within $7~mutext{m}$ from the edge of the substrate, allowing convenient optical access for displacement detection.
Hard point-contact spectroscopy and scanning probe microscopy/spectroscopy are powerful techniques for investigating materials with strong expandability. To support these studies, tips with various physical and chemical properties are required. To ensure the reproducibility of experimental results, the fabrication of tips should be standardized, and a controllable and convenient system should be set up. Here a systematic methodology to fabricate various tips is proposed, involving electrochemical etching reactions. The reaction parameters fall into four categories: solution, power supply, immersion depth, and interruption. An etching system was designed and built so that these parameters could be accurately controlled. With this system, etching parameters for copper, silver, gold, platinum/iridium alloy, tungsten, lead, niobium, iron, nickel, cobalt, and permalloy were explored and standardized. Among these tips, silver and niobiums new recipes were explored and standardized. Optical and scanning electron microscopies were performed to characterize the sharp needles. Relevant point-contact experiments were carried out with an etched silver tip to confirm the suitability of the fabricated tips.
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