In the scanning thermal microscope, the probe employs normally a microfabricated thermocouple or thermistor at the end of probe as a thermal sensor. The thermodynamic properties of sample are detected from the change of thermal electromotive force or electrical resistance of the sensor. In order to improve the thermal detectivity of the sensor, mechanical resonant thermal probe, which relies on the frequency shift due to heat in resonator, have been developed and evaluated.
In this research, we aim at developing a scanning probe for detecting local information on thermodynamic phenomenon using mechanical vibration of a bimetal microresonator. The scanning probe for a temperature sensor, Al/Si bimetal microresonator is integrated at the end of the scanning probe. For simultaneous measurement on topography and infinitesimal heat from a sample, the dual resonance mode of the probe using the first and the second resonant mode is employed. The fundamental resonance mode mainly detects atomic force between chip and surface for topography by the scanning probe microscopy (SPM). The second resonant mode using the self-oscillated bimetal resonator can detects heat on the basis of the resonant frequency changes.
The scanning probes were fabricated by etching the front end of a commercial SPM probe using Focused Ion Beam (FIB). Al metal layer of 500 nm is deposited on the probe by electron beam evaporator and partly removed as well. The length, width, and thickness of bimetal resonator are 45 µm, 8 µm, 2 µm, respectively. The thermal mass of bimetal resonator is about 2Χ10-9 g. The fundamental resonance frequency of probe is 91 kHz, and the resonance frequency of second mode is 441 kHz. The temperature dependences of the resonant frequency of 91 kHz and 441 kHz modes were 115 ppm/K and 127 ppm/K, respectively. Simultaneous measurements of topography and temperature profile on the glass surface were successfully demonstrated.
|