Improved SrTiO3 thin films using oxygen relaxation technique

Published versio

Dielectric properties characterization of La- and Dy-doped BiFeO3 thin films

The dielectric response of La- and Dy- doped BiFeO3 thin films at microwave frequencies (up to 12 GHz) has been monitored as a function of frequency, direct current (dc) electric field, and magnetic field in a temperature range from 25 to 300 °C. Both the real and imaginary parts of the response have been found to be non-monotonic (oscillating) functions of measuring frequency. These oscillations are not particularly sensitive to a dc electric field; however, they are substantially dampened by a magnetic field. The same effect has been observed when the volume of the characterized sample is increased. This phenomenon is attributed to the presence of a limited number of structural features with a resonance type response. The exact origin of these features is unknown at present. Leakage current investigations were performed on the whole set of films. The films were highly resistive with low leakage current, thereby giving us confidence in the microwave measurements. These typically revealed ‘N'-type I-V characteristic

Enhanced electrical properties of ferroelectric thin films by ultraviolet radiation

Published versio

Sintered alumina with low dielectric loss

Published versio

Continuous-wave room-temperature diamond maser

The maser, older sibling of the laser, has been confined to relative obscurity due to its reliance on cryogenic refrigeration and high-vacuum systems. Despite this it has found application in deep-space communications and radio astronomy due to its unparalleled performance as a low-noise amplifier and oscillator. The recent demonstration of a room-temperature solid- state maser exploiting photo-excited triplet states in organic pentacene molecules paves the way for a new class of maser that could find applications in medicine, security and sensing, taking advantage of its sensitivity and low noise. However, to date, only pulsed operation has been observed in this system. Furthermore, organic maser molecules have poor thermal and mechanical properties, and their triplet sub-level decay rates make continuous emission challenging: alternative materials are therefore required. Therefore, inorganic materials containing spin-defects such as diamond and silicon carbide have been proposed. Here we report a continuous-wave (CW) room-temperature maser oscillator using optically pumped charged nitrogen-vacancy (NV) defect centres in diamond. This demonstration unlocks the potential of room-temperature solid-state masers for use in a new generation of microwave devices.Comment: 7 pages, 4 figure

`Maser-in-a-Shoebox': a portable plug-and-play maser device at room-temperature and zero magnetic-field

Masers, the microwave analogues of lasers, have seen a renaissance owing to the discovery of gain media that mase at room-temperature and zero-applied magnetic field. However, despite the ease with which the devices can be demonstrated under ambient conditions, achieving the ubiquity and portability which lasers enjoy has to date remained challenging. We present a maser device with a miniaturized maser cavity, gain material and laser pump source that fits within the size of a shoebox. The gain medium used is pentacene-doped in para-terphenyl and it is shown to give a strong masing signal with a peak power of -5 dBm even within a smaller form factor. The device is also shown to mase at different frequencies within a small range of 1.5 MHz away from the resonant frequency. The portability and simplicity of the device, which weighs under 5 kg, paves the way for demonstrators particularly in the areas of low-noise amplifiers, quantum sensors, cavity quantum electrodynamics and long-range communications

Optimizing strontium ruthenate thin films for near-infrared plasmonic applications

Several new plasmonic materials have recently been introduced in order to achieve better temperature stability than conventional plasmonic metals and control field localization with a choice of plasma frequencies in a wide spectral range. Here, epitaxial SrRuO 3 thin films with low surface roughness fabricated by pulsed laser deposition are studied. The influence of the oxygen deposition pressure (20-300 mTorr) on the charge carrier dynamics and optical constants of the thin films in the near-infrared spectral range is elucidated. It is demonstrated that SrRuO 3 thin films exhibit plasmonic behavior of the thin films in the near-infrared spectral range with the plasma frequency in 3.16-3.86 eV range and epsilon-near-zero wavelength in 1.11-1.47 mm range that could be controlled by the deposition conditions. The possible applications of these films range from the heat-generating nanostructures in the near-infrared spectral range, to metamaterial-based ideal absorbers and epsilon-near-zero components, where the interplay between real and imaginary parts of the permittivity in a given spectral range is needed for optimizing the spectral performance. . At the same time, new applications were put on the agenda, such as perfect absorbers and the so-called epsilon-near-zero (ENZ) effects where the interplay between real and imaginary parts of permittivity is essential for flexibility of the design and achieving required light penetration in the material needed for heat and hot-electron generation. SrRuO 3 (SRO), a material with perovskite-type crystal structure, has been the subject to intense research due to its high thermal and electrical conductivity, and high thermal and chemical stability (up to 1200 K in oxidizing or inert-gas atmospheres

Electrocaloric effect in a ferroelectric Pb

AbstractThe electrocaloric effect in a 0.92Pb(Zn₁/₃Nb₂/₃)O₃-00.8PbTiO₃ single crystal was measured by a direct calorimetric technique as a function of sample temperature and electric field. The temperature of the maximum electrocaloric effect was found to coincide with the ferroelectric transition temperature. We present a theoretical description based on mean-field theory that gives a satisfactory description of the temperature and electric field dependence of the experimentally observed electrocaloric effect.Abstract The electrocaloric effect in a 0.92Pb(Zn₁/₃Nb₂/₃)O₃-00.8PbTiO₃ single crystal was measured by a direct calorimetric technique as a function of sample temperature and electric field. The temperature of the maximum electrocaloric effect was found to coincide with the ferroelectric transition temperature. We present a theoretical description based on mean-field theory that gives a satisfactory description of the temperature and electric field dependence of the experimentally observed electrocaloric effect