Thermoelectric voltage at a nanometer-scale heated tip point contact

Abstract

We report thermoelectric voltage measurements between the platinum-coated tip of a heated atomic force microscope (AFM) cantilever and a gold-coated substrate. The cantilevers have an integrated heater-thermometer element made from doped single crystal silicon, and a platinum tip. The voltage can be measured at the tip, independent from the cantilever heating. We used the thermocouple junction between the platinum tip and the gold substrate to measure thermoelectric voltage during heating. Experiments used either sample-side or tip-side heating, over the temperature range 25-275 °C. The tip-substrate contact is ∼4 nm in diameter and its average measured Seebeck coefficient is 3.4 μV K(-1). The thermoelectric voltage is used to determine tip-substrate interface temperature when the substrate is either glass or quartz. When the non-dimensional cantilever heater temperature is 1, the tip-substrate interface temperature is 0.593 on glass and 0.125 on quartz. Thermal contact resistance between the tip and the substrate heavily influences the tip-substrate interface temperature. Measurements agree well with modeling when the tip-substrate interface contact resistance is 10(8) K W(-1).

Topography-free sample for thermal spatial response measurement of scanning thermal microscopy

“…As the heat coefficient defined for the air gap between the tip and sample is independent of the sample material, 56,62 the thermal resistance of the air gap will not vary with SiN x or gold and is considered to be on the order of 10 5 K/W. 49 Therefore, when comparing all of these interactions between the tip and sample, the spatial variation of thermal spreading resistance due to different sample materials is the most likely candidate for causing the variations observed in the SThM thermal image.…”

“…The thermal spatial resolution of SThM probes is commonly claimed to be sub-100 nm, with the heat conduction area considered to be the same as the tip curvature radius. 33,49 To address these length scales, narrow gold wires with width ranging from 35 to 75 nm were fabricated as patterns.…”

Scanning Thermal Microscopy (SThM)

“…• Development of a micromechanical calibration stage (Dobson et al, 2005), which so far offers the most accurate calibration of an SThM probe. There also have been significant contributions to the analysis of tip-sample physical contact (e.g., Thiery, Toullier, Teyssieux, & Briand, 2008;Kim & King, 2009;Fletcher, Lee, & King, 2012;Gotsmann & Lantz, 2013;Tovee & Kolosov, 2013), including a paper introducing a novel technique meant to help compensating for contact effects during data postprocessing called tip thermal mapping (TThM) ( Jóźwiak et al, 2013).…”

“…Such a design originates in the IBM's Millipede device (Vettiger et al, 2002), although it was not originally meant to be used in SThM-like measurements. Semiconductor SThM probes are being developed in William P. King's group (Nelson & King, 2008), in variants with enhanced thermal insulation (Dai et al, 2010) and a platinum layer enabling thermoelectric measurement (Fletcher et al, 2012), and as matrices of few microcantilevers (Kim et al, 2013). Microcantilevers similar to those of the Millipede are used in A-SThM experiments carried out in IBM laboratories (Menges et al, 2012), while basic heated silicon probes are also available from Anasys Instruments, aimed at measuring thermal properties of polymers (Anasys Instruments Corporation, 2011;Asylum Research, 2011).…”

2-ω and 3-ω temperature measurement of a heated microcantilever

“…10 Several published articles report the investigation of heat generation and heat flow within heated AFM cantilevers, [11][12][13][14] which has led to a clear understanding of the temperature within and near the heated cantilever. 1,2,[15][16][17][18] However, most articles show cantilever temperature calibration during steady-state heating 2,4,15,19 or pulsed heating. 11,[20][21][22] A few articles have investigated the thermal behavior of heated AFM cantilevers during periodic heating.…”