High-Sensitivity Microthermometry Method Based on Vacuum-Deposited Thin Films Exhibiting Gradual Spin Crossover above Room Temperature

Abstract

We report on the fabrication, characterization, and microthermometry application of high-quality, nanometric thin films, with thicknesses in the range 20–200 nm, of the molecular spin-crossover complex [Fe­(HB­(1,2,3-triazol-1-yl)3)2]. The films were obtained by vacuum thermal evaporation and characterized by X-ray diffraction, UV spectrophotometry, and atomic force microscopy. The as-deposited films are dense and crystalline with a preferred [011] orientation of the monoclinic crystal lattice normal to the substrate surface. The films exhibit a gradual spin conversion centered at ca. 374 K spanning the 273–473 K temperature range, irrespective of their thickness. When deposited on a microelectronic device, these films can be used to enhance the UV-light thermoreflectance coefficient of reflective surfaces by more than an order of magnitude, allowing for high-sensitivity thermoreflectance thermal imaging.

Reversible Switching of Strong Light–Matter Coupling Using Spin-Crossover Molecular Materials

“…Film thicknesses were monitored in situ using a quartz crystal microbalance and ex situ by spectral reflectance measurements (Filmetrics, F20). The as-deposited films of 1 are dense and crystalline with a preferred [011] orientation of the monoclinic crystal lattice normal to the substrate surface . The as-deposited films of 2 were recrystallized by a solvent-vapor annealing treatment, resulting in oriented, nanocrystalline thin films …”

“…The as-deposited films of 1 are dense and crystalline with a preferred [011] orientation of the monoclinic crystal lattice normal to the substrate surface. 38 The as-deposited films of 2 were recrystallized by a solvent-vapor annealing treatment, resulting in oriented, nanocrystalline thin films. 37 Spectroscopic Characterization.…”

“…These two isomeric compounds, which only differ by the position of an exodentate nitrogen atom in the triazolyl ring (see their molecular structures in the insets of Figure c and Figure d, respectively), undergo the spin transition above room temperature and have the property of being sublimable, i.e. , they can be deposited by vacuum thermal evaporation in the form of high-quality homogeneous thin films. , The optical absorbance spectra of the films of 1 and 2 deposited on fused-silica substrates exhibit intense SCO-dependent absorption bands in the UV spectral range (Figure c,d). More specifically, at room temperature (in the LS state), compound 1 displays two distinct, well-separated absorption peaks at 337 and 274 nm, while complex 2 exhibits three bands around 317, 305, and 272 nm.…”

Thermometric Properties of Thio/Selenocyanato-Bridged Spin-Crossover Networks

“…The development of temperature sensors attracts much attention in various fields with the advent of numerous methods developed for accurate temperature measurements at nano- and microspatial resolutions and in various conditions. − In particular, noninvasive methods, e.g., infrared (IR), optical, and luminescence thermometry, − can be useful in determining the temperature of certain conditions, such as high temperatures or chemically reactive flames or plasmas. , Additionally, the rarely explored Raman spectroscopy is emerging as a valuable tool for thermometry with the advantages of carrying out nondestructive and noncontact measurements with high spatial resolution on micrometer-sized crystals, thin films, nanoparticles, and powder samples. , Temperature variations can be determined by following the changes in intensity, width of the peak signals, and peak position. Recently, the above thermometric concepts have been extended to spin-crossover (SCO) materials by characterizing various properties, e.g., optical reflectivity, , thermochromic properties, , magnetic resonance imaging, and fluorescence. , They suggested that SCO materials can provide a universal platform for thermometric studies due to their versatile tunability and switching effects.…”

“…9,10 Temperature variations can be determined by following the changes in intensity, width of the peak signals, and peak position. Recently, the above thermometric concepts have been extended to spin-crossover (SCO) materials by characterizing various properties, e.g., optical reflectivity, 11,12 thermochromic properties, 13,14 magnetic resonance imaging, 15 and fluorescence. 16,17 They suggested that SCO materials can provide a universal platform for thermometric studies due to their versatile tunability and switching effects.…”