Three-Dimensional Nanothermistors for Thermal Probing

:Accessing the thermal properties of materials or even fulldevices is a highly relevant topic in research and development. Along withthe ongoing trend toward smallerfeature sizes, the demands onappropriate instrumentation to access surface temperatures with highthermal and lateral resolution also increase. Scanning thermal microscopyis one of the most powerful technologies to fulfill this task down to thesub-100 nm regime, which, however, strongly depends on the nanoprobedesign. In this study, we introduce a three-dimensional (3D) nanoprobeconcept, which acts as a nanothermistor to access surface temperatures.Fabrication of nanobridges is done via 3D nanoprinting using focusedelectron beams, which allows direct-write fabrication on prestructured, self-sensing cantilever. As individual branch dimensions are in the sub-100 nm regime, mechanical stability isfirst studied by acombined approach offinite-element simulation and scanning electron microscopy-assisted in situ atomic force microscopy(AFM) measurements. After deriving the design rules for mechanically stable 3D nanobridges with vertical stiffness up to 50 Nm−1, a material tuning approach is introduced to increase mechanical wear resistance at the tip apex for high-quality AFMimaging at high scan speeds. Finally, we demonstrate the electrical response in dependence of temperature andfind a negativetemperature coefficient of−(0.75±0.2) 10−3K−1and sensing rates of 30±1msK−1at noise levels of±0.5 K, whichunderlines the potential of our concept.