A new nanofabrication procedure has been developed for making thermocouple probes for high-resolution scanning thermal microscopy. Thermocouple junctions were placed at the end of SiN x cantilever probe tips and were typically 100-500 nm in diameter. Cantilever bending due to thermal expansion mismatch was minimized for Au-Ni, Au-Pt, and Au-Pd thermocouples, by carefully choosing thermal probe materials, film thicknesses, and deposition conditions. A spatial resolution of 24 nm was demonstrated for thermal microscopy although the noise-equivalent limit of 10 nm was estimated from experimental data. Using thermopower measurements, a simple model was developed to calculate the tip-sample thermal resistance. Model-based calculations, correlations between topographical and thermal features, as well as experiments in different gaseous and humidity environments indicate that the dominant tipsurface heat conduction is most likely through a liquid film bridging the tip and the sample surface, and not through the surrounding gas, solid-solid point contact, or near-field radiation. Dynamic measurements within a 100 kHz bandwidth showed a time constant of about 0.15Ϯ0.02 ms which was attributed to the thermal time constant of the whole cantilever. Calculations suggested the RC electrical time constant and the thermal time constant of the thermocouple junction to be on the order of 10 ns which, however, could not be experimentally probed.

We report a new technique called scanning Joule expansion microscopy that can simultaneously image surface topography and material expansion due to Joule heating with vertical resolution in the 1 pm range and lateral resolution similar to that of an atomic force microscope. By coating the sample with a polymer film, we demonstrate that sample temperature distribution can be directly measured without the need of fabricating temperature-sensing scanning probes.

This letter presents the design, fabrication, and imaging results of an uncooled infrared (IR) camera that contains a focal plane array of bimaterial microcantilever sensors, and an optical readout technique that measures cantilever deflections in the nanometer range to directly project a visible image of the IR scene on the human eye or a visible camera. The results suggest that objects at temperatures as low as 100 °C can be imaged with the best noise-equivalent temperature difference (NEΔT) in the range of 10 K. It is estimated that further improvements that are currently being pursued can improve NEΔT to about 50 mK.

Deflections of bimaterial microcantilever beams were optically detected with 400 fm resolution at room temperature. This enabled photothermal radiation detection with resolutions of 40 pW for power and 10 fJ for energy. The resolution was improved by an order of magnitude by optimizing the thickness ratio of the two beam materials, as well as by modulating the incident radiation at sufficiently high frequency to be in the range of the thermal white noise limit of the cantilever vibrations. Radiative power was detected with a noise spectral density of and 250 pW/Hz and detectivity, D*, of 4.6×107 cm Hz/W.

This paper presents the design, fabrication and performance of an uncooled micro-optomechanical infrared (IR) imaging system consisting of a focal-plane array (FPA) containing bi-material cantilever pixels made of silicon nitride (SiNx) and gold (Au), which serve as infrared absorbers and thermomechanical transducers. Based on wave optics, a visible optical readout system is designed to simultaneously measure the deflections of all the cantilever beams in the FPA and project the visible deflection map onto a visible charge-coupled device (CCD) imager. The IR imaging results suggest that the detection resolution of current design is 3-5 K, whereas noise analysis indicates the current resolution to be around 1 K. The noise analysis also shows that the theoretical noise-equivalent temperature difference (NETD) of the system can be below 3 mK.