A magnetic force instrument is described which makes use of a differential interferometer which can be used with a very short length cantilever in the force detection assembly. Conventional methods work with cantilevers of a few millimetres in length, but are not suitable for the very much smaller commercial cantilevers which are now available. The instrument described contains novel features which enable it to be used with such cantilevers. Topographical images of calibration specimens and magnetic images of hard disk samples obtained using this instrument are presented.

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A cascode gallium nitride (GaN) switch integrating four paralleled GaN depletion-mode metal-insulator-semiconductor (MIS) high-electron-mobility transistors (HEMT) and a silicon MOSFET (Si-MOSFET) is presented. Each GaN chip is wire-bonded into a multi-chip power module to scale up the power rating. An optimized symmetric configuration and wire bonding of an integral package are used in the cascode switch. By utilizing an optimized packaging approach, the performance of the multi-GaN-chip cascode switch was evaluated through both static and dynamic characterizations. The constructed cascode switch provides a low-static on-state resistance of 72 mΩ and an off-state blocking capability of 400 V with a positive threshold voltage of 2 V. Analysis of dynamic switching characteristics are discussed and demonstrates stable dynamic on-state resistance (RDS-ON) in inductive load circuits with switching dependencies of voltage, frequency, time, and temperature. The extended defects from buffer caused a minimal decrease in dynamic and static RDS-ON with respect to hard switching conditions. However, there was no noticeable degradation in RDS-ON under harsh switching conditions. This study provides a complete analysis of the multi-GaN-chip cascode switch, including MIS-HEMT manufacturing, cascode packaging and static and dynamic characterizations.

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In this work, we describe a nonconfocal differential interferometer to detect the cantilever vibration for a scanning probe microscope. Capable of focusing the beams on the different height surfaces of a cantilever to adapt the length of commercially available cantilever chips, the proposed two-beam interferometer can maintain the sensitivity by placing a glass slip for an object beam to extend the focal length to the cantilever. An experiment involving a scanning force microscope is performed in static mode operation for applications where topography and magnetic images are presented.