We report on the growth by evaporation under high vacuum of high-quality thin films of Fe(phen)2(NCS)2 (phen=1,10-phenanthroline) that maintain the expected electronic structure down to a thickness of 10 nm and that exhibit a temperature-driven spin transition. We have investigated the current-voltage characteristics of a device based on such films. From the space charge-limited current regime, we deduce a mobility of 6.5x10-6 cm2/V?s that is similar to the low-range mobility measured on the widely studied tris(8-hydroxyquinoline)aluminium organic semiconductor. This work paves the way for multifunctional molecular devices based on spin-crossover complexes

Thin films of the spin-crossover (SCO) molecule Fe{[Me2Pyrz]3BH}2 (Fe-pyrz) were sublimed on Si/SiO2 and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen)2(NCS)2, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

We have used the coprecipitation technique to synthesize polycrystalline Co-doped SnO 2 diluted magnetic semiconductors with Co concentrations of 0, 0.5, and 2.0%. X-ray diffraction patterns showed for all samples the expected SnO 2 tetragonal structure with no additional peaks corresponding to parasitic phases. Transmission electron microscopy (TEM) did not indicate the presence of magnetic parasitic phases and confirmed that Co ions are uniformly distributed inside the samples. Optical absorption measurements showed an energy band gap which decreases when increasing the Co concentration. Raman spectroscopy shows an intensity loss of classical cassiterite SnO 2 vibration lines, which is an indication of significant structural modifications and disorder of the SnO 2 lattice. Magnetization measurements revealed a mixture of paramagnetic and antiferromagnetic behavior for Co-doped SnO 2 with no sign of ferromagnetism.