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Register a new userFabrication, properties, and applications of flexible magnetic films
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Flexible magnetic devices, i.e., magnetic devices fabricated on flexible substrates, are very attractive in application of detecting magnetic field in arbitrary surface, non-contact actuators, and microwave devices due to the stretchable, biocompatible, light-weight, portable, and low cost properties. Flexible magnetic films are essential for the realization of various functionalities of flexible magnetic devices. To give a comprehensive understanding for flexible magnetic films and related devices, we have reviewed recent advances in the studies of flexible magnetic films including fabrication methods, magnetic and transport properties of flexible magnetic films, and their applications in magnetic sensors, actuators, and microwave devices. Three typical methods were introduced to prepare the flexible magnetic films. Stretching or bending the flexible magnetic films offers a good way to apply mechanical strain on magnetic films, so that magnetic anisotropy, exchanged bias, coercivity, and magnetoresistance can be effectively manipulated. Finally, a series of examples were shown to demonstrate the great potential of flexible magnetic films for future applications.
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The double perovskite Sr2CrReO6 is an interesting material for spintronics, showing ferrimagnetism up to 635 K with a predicted high spin polarization of about 86%. We fabricated Sr2CrReO6 epitaxial films by pulsed laser deposition on (001)-oriented SrTiO3 substrates. Phase-pure films with optimum crystallographic and magnetic properties were obtained by growing at a substrate temperature of 700 degree C in pure O2 of 6.6x10-4 mbar. The films are c-axis oriented, coherently strained, and show less than 20% anti-site defects. The magnetization curves reveal high saturation magnetization of 0.8 muB per formula unit and high coercivity of 1.1 T, as well as a strong magnetic anisotropy.
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Simple vacuum evaporation technique for deposition of dyes on various solid surfaces has been developed. The method is compatible with conventional solvent-free nanofabrication processing enabling fabrication of nanoscale optoelectronic devices. Thin films of fluorescein were deposited on glass, fluorine-tin-oxide (FTO) coated glass with and without atomically layer deposited (ALD) nanocrystalline 20 nm thick anatase TiO2 coating. Surface topology, absorption and emission spectra of the films depends on their thickness and the material of supporting substrate. On a smooth glass surface the dye initially formes islands before merging into a uniform layer after 5 to 10 monolayers. On FTO covered glass the absorption spectra are similar to fluorescein solution in ethanol. Absorption spectra on ALD-TiO2 is red shifted compared to the film deposited on bare FTO. The corresponding emission spectra at {lambda} = 458 nm excitation show various thickness and substrate dependent features, while the emission of films deposited on TiO2 is quenched due to the effective electron transfer to the semiconductor conduction band.
Recently, nanolaminated ternary carbides have attracted immense interest due to the concomitant presence of both ceramic and metallic properties. Here, we grow nanolaminate Ti3AlC2 thin films by pulsed laser deposition on c-axis-oriented sapphire substrates and, surprisingly, the films are found to be highly oriented along the (103) axis normal to the film plane, rather than the (000l) orientation. Multiple characterization techniques are employed to explore the structural and chemical quality of these films, the electrical and optical properties, and the device functionalities. The 80-nm thick Ti3AlC2 film is highly conducting at room temperature (resistivity of 50 micro ohm-cm), and a very-low-temperature coefficient of resistivity. The ultrathin (2 nm) Ti3AlC2 film has fairly good optical transparency and high conductivity at room temperature (sheet resistance of 735 ohm). Scanning tunneling microscopy reveals the metallic characteristics (with finite density of states at the Fermi level) at room temperature. The metal-semiconductor junction of the p-type Ti3AlC2 film and n-Si show the expected rectification (diode) characteristics, in contrast to the ohmic contact behavior in the case of Ti3AlC2 on p-Si. A triboelectric-nanogenerator-based touch-sensing device, comprising of the Ti3AlC2 film, shows a very impressive peak-to-peak open-circuit output voltage of 80 V. These observations reveal that pulsed laser deposited Ti3AlC2 thin films have excellent potential for applications in multiple domains, such as bottom electrodes, resistors for high-precision measurements, Schottky diodes, ohmic contacts, fairly transparent ultrathin conductors, and next-generation biomechanical touch sensors for energy harvesting.
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