Metallic Thin Film Structures Research Articles

Conditional radiation tolerance of ferroelectric Hf0.5Zr0.5O2 thin film under 60Co gamma-ray irradiation

We report the effect of 60Co gamma-ray irradiation on the ferroelectric properties of metal–ferroelectric Hf0.5Zr0.5O2–metal thin film structures. The pristine Hf0.5Zr0.5O2 films showed strong radiation tolerance against gamma-rays with stable remanant polarization values. When Hf0.5Zr0.5O2 films were exposed to electric field cycling, or “wake-up” process, prior to irradiation, however, their ferroelectricity demonstrated a clear degradation of remanant polarization and coercive voltage shift of the hysteresis curves. The analysis of ferroelectric switching dynamics revealed faster polarization switching with broadening of Lorentzian distribution of characteristic switching time for higher radiation doses, which is contrary to the wake-up behavior. The relationship between the wake-up process and gamma-ray irradiation on the stability of ferroelectric Hf0.5Zr0.5O2 films was discussed in light of domain alignment and defect mechanisms, considering both the redistribution and trapping of defect charges.

Chromium plasmonic polarizer for high intensity light

In this work, we investigate a thin-film polarizer for a high intensity of the electromagnetic (EM) beam based on Cr nano wire arrays. Commonly used thin-film polarizing components are very sensitive for high power of EM waves and can be easily damaged by focused beams. The solution to this problem could be the thin-film polarizer based on metallic subwavelengths structures. This type of optical element has huge resistance comparing to typical thin-film polarizers. However, designing such an optical element for proper wavelength of EM wave and transmissions is not easy task. In this paper we present numerical as well as experimental results for specially designed chromium thin-film polarizer for wavelength 532nm Full Text: PDF ReferencesW. Zhou, K. Li, C. Song, P. Hao, M. Chi, M. Yu and Y. Wu, "Polarization-independent and omnidirectional nearly perfect absorber with ultra-thin 2D subwavelength metal grating in the visible region", Opt. Express 23, 11 (2015). CrossRef W. L. Barnes, A . Dereux, and T. W. Ebbesen, "Surface plasmon subwavelength optics", Nature 424, 824-830 (2003). CrossRef C. Lee, E. Sim, D. Kim, "Blazed wire-grid polarizer for plasmon-enhanced polarization extinction: design and analysis", Opt. Express 25, 7 (2017). CrossRef A. Lehmuskero, Metallic thin film structures and polarization shaping gratings (University of Eastern Finland 2010).Y. Leroux, J. C. Lacroix, C. Fave, V. Stockhausen, N. Felidj, J. Grandm, A. Hohenau, J. R. Krenn, "Active plasmonic devices with anisotropic optical response: a step toward active polarizer", Nano Lett. 5, 9 (2009). CrossRef R. T. Perkins, D. P. Hansen, E. W. Gardner, J. M. Thorne, A. A. Robbins, Broadband wire grid polarizer for the visible spectrum, US 6122103 (2000). DirectLink D. M. Sullivan, Electromagnetic simulation using the FDTD method, New York: IEEE Press Series (2000). CrossRef J. P. Berenger, Perfectly Matched Layer (PML) for Computational Electromagnetics, Morgan & Claypool Publishers (2007). CrossRef Yu, W., and R. Mittra, "A conformal FDTD software package modeling antennas and microstrip circuit components", IEEE Antennas Propagat. Magazine 42, 28 (2000) . CrossRef L. W. Bos, D. W. Lynch, "Optical Properties of Antiferromagnetic Chromium and Dilute Cr-Mn and Cr-Re Alloys", Phys. Rev. Sect. B, 2, 4267 (1970). CrossRef

Penetrative imaging of sub-surface microstructures with a near-field microwave microscope

Microwaves have the capability of penetrating through materials with low permittivity. By means of a near-field scanning microwave microscope system, we obtained two-dimensional maps of the incident microwave's reflection coefficient intensity and frequency shift, which correspond well to the spatial distribution and electrical conductance of fluids and metallic thin film structures hidden underneath 15–170 μm thick dielectric covers. The lateral resolution and sensitivity to conductivity for the target samples were found closely related to the thickness of the cover layer. The technique offers a real-time, in-situ, and a non-invasive approach to monitor the local chemical reactions, the motion of fluids, and the distribution or concentrations of ions or bio-materials in lab-on-a-chip systems. This technique also has the potential to be developed for the detection of live cells and tissues.

Tuning the Crystal Structure and Magnetic Properties of CoNiFeB Thin Films

CoNiFeB thin films with a high saturation magnetic flux density (Bs) and a low coercivity (Hc) are used as core materials in high-density recording heads. Electroless deposition has proven to be an excellent process for the fabrication of metallic thin film structures, because it does not suffer from limitations associated with current density distribution and can therefore be used to create uniform coatings on substrates with fine and/or complex geometries. The crystal structure of CoNiFeB films, which is dependent on their chemical composition, can be controlled by changing the bath composition; however, to our knowledge, there is no report on tuning the chemical composition, crystal structure, and magnetic properties of CoNiFeB thin films only by the optimization of the electroless deposition parameters while maintaining the same concentration of salts in the bath. In this study, through the use of complementary techniques including AFM, SEM, XRD, EDS, and VSM, we show how the crystal structure of the ...

Plasmonic crystal for efficient energy transfer from fluorescent molecules to long-range surface plasmons

Corrugated metallic thin film structures that do not support short-range surface plasmon modes but do support long-range modes are discussed. The coupling efficiency of the energy of excited fluorescent molecules to long-range modes is theoretically calculated using the rigorous coupled wave approach. The obtained maximum coupling efficiency is found to be 55%, more that two times higher than the efficiency of uncorrugated metallic thin films.

A model for fatigue in ferroelectric thin films based on trapping of carriers at interfacial states

Experimental data on fatigue in the Metal∕Ferroelectric∕Metal thin film structures are reported. A model is proposed based on the trapping and the releasing of the free carriers in the band-gap states located at the interfaces between the electrodes and the ferroelectric film. Fits of the experimental data with the plots calculated from the model show very good agreement. In particular, the fatigue dependence on both the frequency and the magnitude of the applied voltage is well reproduced by the model. Saturation of fatigue for a large number of cycles is also predicted.

Monte Carlo simulation of current–voltage characteristics in metal–insulator–metal thin film structures

Many metal–insulator–metal (MIM) thin film sandwich structures exhibit an electroforming process, following which the resulting direct current (DC) current–voltage I–V characteristic exhibits ohmic conduction and voltage-controlled differential negative resistance (VCNR) at low and high voltages, respectively. One of the more successful models of these phenomena is the filamentary model, in which it is assumed that the electroforming process establishes a population of ohmic filaments within the insulating matrix, which span the metal contacts. The VCNR behaviour results from the progressive cessation of conduction in individual filaments owing to Joule heating effects. Early work showed that by postulating plausible probability distributions of filament resistances, I–V characteristics typical of those obtained experimentally could be derived. More recently more realistic normal distributions of filament resistances, radii and cross-sectional areas have been considered, and these too have yielded characteristics in accordance with experiment. In the present work normal distributions of filament resistances and radii are considered, but in contrast to previous work a novel method using a Monte Carlo simulation was employed. Furthermore, the effects of using a combination of two different filament resistivity values were explored. Variations in conductance and shifts in the current peak were explicable using existing theory. The approach adopted in this work lends itself to the exploration of more complex filament distributions, and therefore to a better representation of the underlying filament population, including those having a multivariate distribution.

Barrier photovoltaic effects in PZT ferroelectric thin films

The photoelectric characteristics (independent of ferroelectric polarization) of metal-ferroelectric- metal thin film structures upon exposure to radiation in different ranges of mercury arc lamp spectrum are stud- ied for the Pb(Zr 0.5 2Ti 0.48 )O 3 ( PZT ) ferroelectrics. The PZT films on platinized silicon substrates were prepared by the sol-gel technique. The relaxations of the short-circuit current and the open-circuit voltage are investi- gated at different intensities of light with wavelengths in the range 300-1200 nm. It is found that the open-cir- cuit voltage returns to its original value after the cessation of light exposure and a short-term holding of struc- tures in the short-circuited state. The factors responsible for the photocurrent and the photoemf are analyzed, and the conclusion is made that they are predominantly contributed by the barrier photovoltaic effects associ- ated with the presence of the p - n junction in the bulk of films and the Schottky barrier in the film region adjacent to the lower platinum electrode. © 2000 MAIK "Nauka/Interperiodica".

Seeded epitaxy of metals by sputter deposition

It is not generally appreciated that crystalline metallic thin film structures can be prepared using sputter deposition techniques by growth onto single crystalline substrates. Three systems, fcc Co/Cu(100), bcc Co/Cr(100), and hcp Co/Ru(101̄3) multilayers are described in detail from a comprehensive study of more than 40 different systems. It is shown that the use of thin ‘‘seed’’ layers readily allows the preparation of different crystal structures and/or crystal orientations for the same substrate.