Unprecedented Size Effect on the Phase Stability of Molecular Thin Films Displaying a Spin Transition

Shalabaeva, Victoria; Mikolasek, Mirko; Manrique-Juárez, María Dolores; Bas, Alin-Ciprian; Rat, Sylvain; Salmon, Lionel; Nicolazzi, William; Molnár, Gábor; Bousseksou, Azzedine

doi:10.1021/acs.jpcc.7b10124

Cited by 26 publications

(41 citation statements)

References 33 publications

(52 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is particularly clear in Figure b, which displays the temperature dependence of the two elastic moduli peaks: the transition curve corresponding to the surface area near the crack (denoted “Peak 2”) is downshifted by about 3 K. Interestingly, this shift is approximately of the same order of magnitude—with opposite sign—as the variation of the spin transition temperature with decreasing film thickness. Indeed, in a previous work we have shown that when decreasing the thickness of films of 1 , the LS state is progressively stabilized due to its lower surface/interface energy and stress . We can thus suggest that cracks relieve the surface stress effects and thus restore the HS state in the film by a strain relaxation mechanism.…”

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 65%

“…At first sight, the spin transition curve of the thin film of 1 , obtained by far‐field optical microscopy (Figure b), is reminiscent to that of the bulk crystal (Figure ). In particular, a thermal hysteresis loop of ≈0.5 K width is reproducibly observed for the films (see ref . for more details), which is a mark of a first‐order transition.…”

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 70%

“…These films exhibit a well‐reproducible thermal SCO (similar to the bulk material) as well as an ultrafast (≈10 −13 s) light‐induced spin state switching at room temperature . With decreasing film thickness, the transition is slightly shifted to higher temperatures, which we attributed to the stabilization of the LS phase by surface energy and stress . The transition in the films is accompanied by a substantial spontaneous strain and associated changes of refractive index and electrical resistance, which gives rise to numerous potential applications of 1 in mechanical actuators, temperature sensors, photonic and electronic devices …”

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 88%

“…The surface/interface energy can be therefore viewed as a key parameter, which governs the SCO properties at the nanoscale . Understanding surface/interface phenomena is not only important to elucidate nanoscale SCO behaviors but also opens up possibilities for engineering these nanomaterials . However, thin films and nanostructures usually have nonuniform properties due to defects, grain boundaries, strain distributions, and so forth.…”

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 99%

“…

also opens up possibilities for engineering these nanomaterials. [12][13][14][15][16][17][18][19] However, thin films and nanostructures usually have nonuniform properties due to defects, grain boundaries, strain distributions, and so forth. There is therefore a need toward the assessment of these effects on a submicrometer scale from spatially resolved techniques.Scanning probe microscopy (SPM) provides an attractive means for quantitative and noninvasive studies of local phase change behaviors in various materials under external stimuli (magnetic and electric fields, temperature, light irradiation, etc.).

…”

mentioning

confidence: 99%

See 4 more Smart Citations

Direct Visualization of Local Spin Transition Behaviors in Thin Molecular Films by Bimodal AFM

Shalabaeva

Bas

Piedrahita‐Bello

et al. 2019

Small

Self Cite

View full text Add to dashboard Cite

Thin films of the molecular spin‐crossover complex [Fe(HB(1,2,4‐triazol‐1‐yl)3)2] undergo spin transition above room temperature, which can be exploited in sensors, actuators, and information processing devices. Variable temperature viscoelastic mapping of the films by atomic force microscopy reveals a pronounced decrease of the elastic modulus when going from the low spin (5.2 ± 0.4 GPa) to the high spin (3.6 ± 0.2 GPa) state, which is also accompanied by increasing energy dissipation. This technique allows imaging, with high spatial resolution, of the formation of high spin puddles around film defects, which is ascribed to local strain relaxation. On the other hand, no clustering process due to cooperative phenomena was observed. This experimental approach sets the stage for the investigation of spin transition at the nanoscale, including phase nucleation and evolution as well as local strain effects.

show abstract

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 65%

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 70%

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 88%

Section: Comparison Of Reported Elastic Moduli Ofmentioning

confidence: 99%

“…

…”

mentioning

confidence: 99%

See 3 more Smart Citations

Direct Visualization of Local Spin Transition Behaviors in Thin Molecular Films by Bimodal AFM

Shalabaeva

Bas

Piedrahita‐Bello

et al. 2019

Small

Self Cite

View full text Add to dashboard Cite

show abstract

Finite Size Effects on the Switching Dynamics of Spin‐Crossover Thin Films Photoexcited by a Femtosecond Laser Pulse

et al. 2019

Self Cite

View full text Add to dashboard Cite

Using ultrafast optical absorption spectroscopy, we have studied the room-temperature spinstate switching dynamics induced by a femtosecond laser pulse in high-quality thin films of the molecular spin-crossover complex [Fe(HB(tz)3)2] (tz = 1,2,4-triazol-1-yl). These measurements reveal that the early, sub-picosecond, low-spin to high-spin photoswitching event, with linear response to the laser pulse energy, can be followed under certain conditions by a second switching process occurring on a tens of nanoseconds timescale, enabling nonlinear amplification. Such out-of-equilibrium dynamics is discussed in light of characteristic timescales associated with the different switching mechanisms, i.e. the electronic and structural rearrangements of photo-excited molecules, the propagation of strain waves at the material scale and the thermal activation above the molecular energy barrier. Importantly, size reduction effects are evidenced on the second switching step. Notably, this nonlinear process appears to be completely suppressed in the thinnest (50 nm) film due to the efficient heat transfer to the substrate, allowing the system to retrieve the thermal equilibrium state on the 100-ns timescale.These results provide a first milestone towards the assessment of the physical parameters that

show abstract

Vertical Tunnel Junction Embedding a Spin Crossover Molecular Film

Poggini

Gonidec

González‐Estefan

et al. 2018

Adv Elect Materials

View full text Add to dashboard Cite

properties of SCO compounds is fundamental, to understand how they behave under electronic stimuli, especially when prepared as thin films. [8,9] Indeed, these molecules can be switched between two electronic states-termed high-spin (HS) and low-spin (LS)-with different magnetic, optical, and structural properties by the action of external stimuli (pressure, temperature, light-irradiation) [10][11][12][13][14] making them promising systems for new functional materials. [7] This is particularly important since the use of electrical stimuli to control (read/write) the spinstate of the system would provide a great advantage toward technological applications, compared to other conventional addressing methods such as light irradiation, and changes in temperature or pressure, that are less easily implemented. In this paper, we show that it is possible to design large area switchable molecular tunnel junctions, in which the switchable tunneling barrier is made of a thin film of a SCO compound. Those thin films, made by evaporation on TS Au (template-stripped gold), were thoroughly characterized using highly-sensitive and specific surface tools. Electrical switching has been studied as a function of temperature in a tunnel junction configuration, and the experimental results have been rationalized thanks to a theoretical model based on energy levels and electronic densities obtained at density functional theory (DFT) level. The good correlation we establish between experimental measurements and modeling proves the feasibility to design, manipulate, and read such ultrathin film devices, an important prerequisite for the development of future active multistable devices. The most critical issues toward the development of large-area spin-crossover based molecular junctions are i) to obtain high quality SCO thin films over large areas and ii) to have a measurement methodology that allows to measure their properties in an efficient and reliable manner. Moreover, to facilitate further developments and applications of those systems, it is highly desirable to have a transition temperature (and thus, possibly, a switching temperature) close to room temperature. For those reasons, we have chosen the [Fe(HB(trz) 3 ) 2 ] SCO complex, hereafter called 1 (HB(trz) 3 = tris(1H-1,2,4-triazol-1-yl)borohydride), [15][16][17][18] for which it was shown recently that it can be deposited as continuous thin films on surfaces by thermal evaporation. [19,20] Some recent efforts have focused on vertical large area SCO junctions with film thicknesses in the 10-200 nm range Thin films of a molecular spin crossover (SCO) Iron(II) complex featuring a high transition temperature are grown by sublimation in high vacuum on TS Au and investigated by X-ray and UV photoelectron spectroscopies. Temperaturedependent studies demonstrate that the thermally induced spin crossover behavior is preserved in thin films. A large-area ultrathin switchable spin crossover molecular vertical tunnel junction with top electrodes of the liquid eutectic of gallium and indium...

show abstract

Unprecedented Size Effect on the Phase Stability of Molecular Thin Films Displaying a Spin Transition

Cited by 26 publications

References 33 publications

Direct Visualization of Local Spin Transition Behaviors in Thin Molecular Films by Bimodal AFM

Direct Visualization of Local Spin Transition Behaviors in Thin Molecular Films by Bimodal AFM

Finite Size Effects on the Switching Dynamics of Spin‐Crossover Thin Films Photoexcited by a Femtosecond Laser Pulse

Vertical Tunnel Junction Embedding a Spin Crossover Molecular Film

Contact Info

Product

Resources

About