UTOT probe: ultra-sensitive and ultra-fast SThM probe
In order to reduce the thermal time constant, minimize the tip radius, and maximize the thermal sensitivity of the SThM probe at the same time, SThM probe with UTOT (ultra-thin oxide tip) is developed. We modify the design of NP SThM01, shown in Fig. 1(a), such that the SiO2 film that composes the probe tip becomes extremely thin, as shown in Fig. 1(b). When the SiO2 film composing the probe tip becomes extremely thin (~100 nm), the thermal insulation of the sensor located at the tip’s apex is radically improved. Furthermore, because the thermal mass of the tip is also reduced drastically, the thermal time constant of the probe is decreased significantly. In addition, because the thin SiO2 tip is formed by thermally oxidizing a very sharp silicon tip for a much shorter time than is required to produce a thick SiO2 tip (~1.5 μm), the radius of the thin SiO2 tip is reduced further than NP SThM01.
Fig. 1 Comparison of the structure of UTOT probe and that of NP SThM 01 (not to cale).
Fig. 2 The SEM images of the tip of UTOT probe and that of NP SThM 01.
Tip radius Electrical resistance Seebeck coefficient
40 ± 10nm 600 ± 50 Ω 20.5 μV/K
Cantilever length Tip height Tip half angle
200 μm 10 ± 1 μm 18 o