Unprecedented switching endurance affords for high-resolution surface temperature mapping using a spin-crossover film

Abstract

Temperature measurement at the nanoscale is of paramount importance in the fields of nanoscience and nanotechnology, and calls for the development of versatile, high-resolution thermometry techniques. Here, the working principle and quantitative performance of a costeffective nanothermometer are experimentally demonstrated, using a molecular spincrossover thin film as a surface temperature sensor, probed optically. We evidence highly reliable thermometric performance (diffraction-limited sub-µm spatial, µs temporal and 1°C thermal resolution), which stems to a large extent from the unprecedented quality of the vacuum-deposited thin films of the molecular complex [Fe(HB(1,2,4-triazol-1-yl) 3) 2 ] used in this work, in terms of fabrication and switching endurance (>10 7 thermal cycles in ambient air). As such, our results not only afford for a fully-fledged nanothermometry method, but set also a forthcoming stage in spin-crossover research, which has awaited, since the visionary ideas of Olivier Kahn in the 90's, a real-world, technological application.

Nonvolatile Voltage Controlled Molecular Spin-State Switching for Memory Applications

“…The requirements tend to exclude molecular salts and polymers, as neither can be evaporated readily. Yet the approach has been successfully applied to [Fe(1,10-phenanthroline) 2 (NCS) 2 ] (frequently known as Fe(phen) 2 (NCS) 2 ) [38][39][40][41][42][43][44], as illustrated in Figure 2a, [Fe(H 2 B(pz) 2 ) 2 phen] where H 2 B(pz) 2 = dihydrobis(1H-pyrazol-1-yl)borate [45][46][47][48][49][50][51], as illustrated in Figure 2c, [Fe(HB(tz) 3 ) 2 ] (tz = 1,2,4-triazol-1-yl) [52][53][54][55][56], as illustrated in Figure 2d, [Fe(HB(3,5-(CH 3 ) 2 -(pz) 3 ) 2 ], where pz = pyrazolyl [10,[57][58][59][60][61], as illustrated in Figure 2e, [Fe(qnal) 2 ] where qnal = quinoline-naphthaldehyde [62], as illustrated in Figure 2f, [Fe(HB(pz) 3 ) 2 ] where pz = pyrazolyl [11,63], and the molecule that is the focus of this review: [Fe{H 2 B(pz) 2 } 2 (bipy)] where (H 2 B(pz) 2 = bis(hydrido)bis(1H-pyrazol-1-yl)borate, bipy = 2,2 -bipyridine) [13,14,[64][65][66][67][68][69][70]…”

“…Although molecular devices are generally considered very fragile compared to inorganic devices, endurance may not be the issue once feared. Recently, there have been molecular spin crossover devices fabricated that have been shown to undergo 10 million switches without degradation [56]. These demonstration spin crossover molecular devices were not designed for nonvolatile voltage-controlled memory applications; just the same, this recent demonstration of spin-state switching endurance [56] provides considerable evidence in favor of spin crossover molecular devices.…”

“…Recently, there have been molecular spin crossover devices fabricated that have been shown to undergo 10 million switches without degradation [56]. These demonstration spin crossover molecular devices were not designed for nonvolatile voltage-controlled memory applications; just the same, this recent demonstration of spin-state switching endurance [56] provides considerable evidence in favor of spin crossover molecular devices. The limits of possible endurance without degradation have not been tested in spite of the fact that these are molecular devices.…”

A molecular spin-crossover film allows for wavelength tuning of the resonance of a Fabry–Perot cavity

“…Recent studies have demonstrated that the molecular spin state of these thin films can be modulated at high frequencies (1-10 MHz) with outstanding switching endurance (> 10 7 cycles). [30][31] Based on these attributes, films of 1 have been integrated into electronic/electromechanical test devices to explore their electrical resistance switching capabilities [32][33] and their ability to induce mechanical actuation. 34 and thermal damping 35 .…”

“…In addition, they have been effectively used for nanoscale thermal imaging. 31 In order to explore the photonic properties of 1, we have determined the optical constants (n, k) of a nominally 100-nm-thick film (on top of a silicon substrate) using a Horiba UVISEL ellipsometer. Ellipsometric data were acquired for wavelengths between 250 and 1000 nm at various angles of incidence (AOI = 56-60°) and selected temperatures (25-95 °C), and fitted by a single oscillator model.…”