edfas.org ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 25 NO . 1 12 on (110) SrTiO3 substrates uncoveredadramatic first-order phase transition with a colossal magnetoresistance from the antiferromagnetic charge/orbital-order insulating state to the ferromagnetic metallic state. With sMIM, researchers observed an orientation-ordered percolating network of domains through the transition.[9] The network has a large periodof ~100 nanometers and the filamentary metallic domains preferentially align along certain crystal axes of the substrate, suggesting that the anisotropic elastic strain from the substrate is a key interaction in this system. DOMAIN WALLS IN MAGNATE In the study of domainwalls inmagnatematerials, the areas to be investigated are often buried under an insulating bulk. By using microwaves, sMIM can image through the insulating material enabling local nanoscale conductivity measurements. In a published study,[10] by using sMIM the researchers were able to show the existence of conductivemagneticdomainwalls inamagnetic insulator. SUMMARY The study of the properties of materials at the nanoscale requires new tools and technologies to enable discoveries and improve our understandingof thephysical world. Scanningmicrowave impedancemicroscopy is one such technology that has been configured to operate in a wide range of temperatures fromsub 100mK to roomtemperature. Usingmicrowaves, electrical properties ofmaterials such as permittivity and conductivity can bemapped at the nanoscale at ultra-low temperatures and under strongmagnetic fields. In addition, ACmeasurements can be taken to determine doping type and concentration in semiconductors. Themicrowave signal also provides sub surface informationwithout any special sample treatment. sMIM is now commercialized and turnkey solutions are offered so that researchers can focus on their research and not equipment building. High sensitivity electronics combined with a shielded probe and impedance matching provide extremely high electrical resolution (0.075 aF capacitance sensitivity) and nanoscale spatial resolution. Until recently, sMIM images have been qualitative in nature but quantification of dopant levels in semi- (a) Fig. 7 Quantumwell behavior under varyingmagnetic fields: (a) device structure, (b) 5.5 nmquantumwell device conductivity vs magnetic filed, and (c) 7.5 nm quantumwell device conductivity vs magnetic field. (b) (c) Fig. 6 An aluminumplate surrounded by SiO2 imaged at sub 100mK. Top image is of topography,middleof sMIM-C (in volts) and bottom is the sMIM-R image (in volts).
RkJQdWJsaXNoZXIy MTMyMzg5NA==