This paper presents an improved technique for monitoring and controlling the contact condition of on-wafer RF probes with nanometer accuracy to enhance the measurement repeatability. The setup consists of a vector network analyzer, a modified probe station with a planar calibration substrate aligned under microwave GSG probe through a closed-loop nanopositioner and a camera system. A fully one-port SOL calibration is performed in the frequency range 0.05-50 GHz. A repeatability study based on standard deviations of the measured data considering both conventional and proposed approaches is described. From these experimental results, the improvement of the technique proposed is achieved by accurately controlling the probe contacts.
The micro- and nanoscale characterization and mapping of surface properties and surface behaviour is critical to both physical and biological science. Mechanical contact probes are a critical tool for investigating surface and interface science, and have seen greater development and a diversification in recent years. In particular, mechanical contact probes that have been fabricated from the bottom-up by the assembly of synthesized nano- or microscale materials can provide enhanced functionality and sensitivity over traditional microcantilevers. This work provides an overview of recent developments in the field of assembled micro- and nanoscale mechanical contact probes, with a specific focus on three probe types: colloidal particle probes with high aspect ratio and a high lateral sensitivity, one-dimensional probes comprising of nanotube and/or nanowire deflection elements, and liquid metal-based probes. For each probe type, the state-of-the-art is reviewed, and their assembly, design, functionality and capabilities are discussed. An outlook on the future direction of probe development and potential applications is also given.
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