Thermoelectric effect in very thin film Pt∕Au thermocouples

Abstract

The thickness dependence of the thermoelectric power of Pt films of variable thickness on a reference Au film has been determined for the case when the Pt film thickness, t, is not large compared to the charge carrier mean free path, ℓ, that is, t / ℓ. Pt film thicknesses down to 2.2 nm were investigated. We find that ΔS F = S B -S B F (where S B B and S F are the thermopowers of the Pt bulk and film, respectively) does not vary linearly as 1/t as is the case for thin film thermocouples when the film thickness is large compared to the charge carrier mean free path.Keywords: Thermopower effect; Thin-film platinum-gold thermocouples. where the scattering coefficient, p, is the fraction of energy lost by the charge carriers when reflected by the film surface. Since ρ = 1/σ, Eq. (1) can be written in terms of the resistivityAccording to Justi et al. [3] and Mayer [4], when Eq. (1) is obeyed the thermoelectric power S F of pure metal thin films with thickness t >> ℓ is given byB where U = (∂ lnℓ(E)/∂ lnE) E= ξ , E is the electron energy, ξ is the Fermi energy, and the bulk thermoelectric power S B is given bywherer k is Boltzmann's constant, T the absolute temperature, and e the electron charge.From Eqs. (2) and (3) we obtainIf Φ F and Φ B are the thermopowers of a thin-film and a thick-film of Pt with respect to a thick standard film, respectively, then [17] of the thermoelectric power of thin iron films showed the predicted 1/t thickness dependence. 3For all of the above experimental work [1,5,6,8,[14][15][16][17] The Pt and Au films were formed using a filtered vacuum arc plasma deposition method that has been fully described elsewhere [18]. Briefly, a repetitively-pulsed vacuum arc plasma gun equipped with either a Au or Pt cathode is used to form a dense metal (Au or Pt) plasma, which is then transported through a 90 o bent solenoidal magnetic field to remove any solid particulates (cathode debris) from the plasma stream. The plasma is then allowed to deposit on a substrate that is positioned near the exit of the solenoid filter. Thin film samples of different thicknesses can readily be prepared by varying the number of plasma pulses used for the deposition. For the work described here the plasma pulses were 5 ms long and the repetition rate was 1 pulse/sec. The substrates used for film deposition were ordinary glass microscope slides of dimension 25 × 75 mm 2 . The geometry used for all samples is shown in Fig. 1. The Au film strips were the same thickness for all samples, and the thickness of the Pt film was varied for the different samples. We prepared a set of samples in which the Au films were of thickness 141 ± 2 nm and the Pt films were of thicknesses from 2.2 to 166 nm. 4Importantly, we note that the vacuum arc plasma deposition method that we have used is an energetic deposition, with the depositing Pt ion flux having a directed ion energy of ~100 eV [19], resulting in films that are void free and fully dense [20].Measurements were made with the hot junction immersed in oil inside a calorimet...

Determining intracellular temperature at single-cell level by a novel thermocouple method

“…In a calibration experiment with these two types of probes, we found that the 100 nm probe produced a temperature-thermoelectricity curve that showed an almost perfect match with the standard curve produced by a regular macro-sized TC, while the readings from the 50 nm probe showed deviations from the standard curve ( Figure 1B and 1C and Supplementary information, Figure S2). This result is consistent with earlier reports that when the thickness of the Pt film decreases beyond the 100 nm range, it will affect the resulting thermoelectric power compared to the macrosized TC at the same temperature [6,7]. Thus, we have chosen the 100 nm probe in further experiments.…”

Self-completed Joule heat welding of ultrathin Pt wires

“…Moreover, welding technologies for low-dimensional materials have been found to be effective for manipulating materials 11 and for generating functional elements, e.g., thermoelectric 15,16 and optical elements, 17 etc.…”

Antenna-Coupled Nanowire Thermocouples for Infrared Detection

“…Previous studies have shown that the relative Seebeck coefficient of thin films decreases as the film thickness is reduced to less than 200 nm [9], [10]. The impact of different metal combinations on the Seebeck coefficients of the nanowire thermocouples was characterized with the platform described in [11].…”