Spectroscopic ellipsometry applied to phase transitions in solids: possibilities and limitations
The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigation in oxide thin films and crystals are examined in this work, along with the use of various parameters calculated from ellipsometric data (band gap energy Eg, refractive index n and surface roughness) together with the directly measured main ellipsometric angles psi and Delta, for the detection of phase transitions. The efficiency of spectroscopic ellipsometry on "surface" phase transition and its sensitivity to surface defects are also demonstrated.
Formation of Optical Gradient in Chemical Solution-Derived PbZr[sub 0.52]Ti[sub 0.48]O[sub 3] Thin Films: Spectroscopic Ellipsometry Investigation
Investigation using a variable angle spectroscopic ellipsometer revealed the influence of sample preparation conditions on sol-gel PbZr 0.52 Ti 0.48 O 3 (PZT 52/48) thin-film homogeneity that allows identification and further optimization of thin-film performance. Separate crystallization of the layers determined the optical gradient appearance, irrespective of the chemical solvents used in this work. A more refined analysis showed that a refractive index gradient was apparent in the samples in which lattice parameters strongly changed with thickness. For these films, energy-dispersive X-ray spectroscopy analysis showed significant variation in Pb and Zr. Additionally, complex dielectric fu…
Optical Gradient of the Trapezium-Shaped NaNbO[sub 3] Thin Films Studied by Spectroscopic Ellipsometry
thin films were performed in the photon energy range of 1.24–4.96 eV.Effective values of the complex refractive index and thickness nonuniformity, roughness, and depth profile of the real part of therefractive index were evaluated. An increase of the refractive index with increasing of the sample thickness was observed anddiscussed.© 2008 The Electrochemical Society. DOI: 10.1149/1.2965786 All rights reserved.Manuscript submitted May 27, 2008; revised manuscript received July 7, 2008. Published August 19, 2008.
PHASE TRANSITIONS IN THE PLZT x/85/15 SOLID SOLUTIONS
ABSTRACT Role of a La on the nature of phase transition in the PLZT x/85/15 is compared with the PLZT compositions of lower Zr/Ti ratio. Thermal dependence of the dielectric permittivity, thermal expansion and elastic modulus reveal sequential transfer from macroscopic ferroelectric to antiferroelectric and nonpolar state, if La concentration is increased. Diffused, from frequency independent thermal dependence of dielectric permittivity for compositions in certain La concentration range above 4 at% coexist with the well expressed phase transition between paraelectric and antiferroelectric phases.
<title>Irradiation effects in lead zirconate thin films</title>
Lead zirconate PbZrO3 (PZ) and PbZr0.53Ti0.47O3 (PZT) sol-gel films with a thickness of up to 1.5 μm were deposited on TiO2/Pt/TiO2/SiO2/Si substrates by spin coating technique and heterostructures of the same composition as well as on Pb0.92La0.08 (Zr0.65Ti0.35)O3 (PLZT-8) (with a thickness of 0.4 μm) were pulse laser deposited (PLD) on Pt/Ti/SiO2/Si. Observation of a typical antiferroelectric (AFE) double hysteresis loop in obtained PZ heterostructures at room temperature was attributed to the superior dielectric strength in case of thin film materials. The thermal behavior of dielectric permittivity e of PZ film reveals a maximum near 225°C on heating and 219°C on cooling. The higher res…
Thermo‐optical investigations of NaNbO 3 thin films by spectral ellipsometry
In this work a spectroscopic ellipsometry was applied to the thermo-optical investigations of sodium niobate NaNbO3 (NN) thin films at the wide temperature range of 5–820 K. The temperature dependence of complex refractive index dispersions and optical bang energy of the direct allowed electron transitions were evaluated. Additionally dynamic scans of the main ellipsometric angles at the several fixed wave lengths of 300, 400, 500 and 635 nm were performed to acquire more detailed temperature dependences of the refractive index and extinction coefficient. Pronounced minima/maxima and substantial jumps in the temperature dependence of complex refractive index and band gap energy were found a…
Compositional and Optical Gradient in Films of PbZrxTi1-xO3 (PZT) Family
Pb(ZrxTi1-x)O3 (PZT) (x = 0-1) films have attracted the attention of researchers for the past 30 years due to their excellent ferroelectric (FE) and electromechanical properties, which have led to the commercialization of thin PZT films for ferroelectric random access memory (FeRAM), forming a market of several millions USD annually. Ferroelectricity of perovskite oxide thin films, especially PZT thin films, can be exploited in semiconductor devices to achieve non-volatile random access memory (NVRAM) with high-speed access and long endurance, which can overcome the barriers, encountered in current semiconductor memory technologies. The ferroelectricity can be also exploited to voltage depe…
Antiferroelectric PbZrO3 thin films: structure, properties and irradiation effects
Abstract Irradiation effects on highly oriented antiferroelectric PbZrO 3 and ferroelectric Pb 0.92 La 0.08 (Zr 0.65 Ti 0.35 )O 3 thin films are investigated being exposed to neutron irradiation up to fluence 2*10 22 m −2 . The higher resistance of antiferroelectric PbZrO 3 thin films as compared to ferroelectric heterostructures to large fluences of neutron irradiation is recognized and discussed. Influence of two factors (structural and charge) was taken into account analysing irradiation effects on materials of different polarization states: ferroelectric PLZT (ceramics and thin films) and antiferroelectric PbZrO 3 films.
Optiskā gradienta un fāzu pāreju pētījumi NaNbO3 un Pb(Zr, Ti)O3 plānās kārtiņās
Elektroniskā versija nesatur pielikumus
Alternating-Current Properties of Elastomer-Carbon Nanocomposites
Optical Spectra and Direct Optical Transitions in Amorphous and Crystalline ZnO Thin Films and Powders
Comparative studies of ZnO crystalline and amorphous thin films and nanocrystalline powders are reported. The UV-visible optical spectra were analyzed with special attention paid to the direct optical bandgap. Atmospheric radio-frequency barrier torch discharge and pulsed hollow cathode sputtering techniques for the film fabrication were used. For the crystalline films, similar values of the direct optical bandgap were found independent of the growth method used. The analysis of the amorphous films and powders revealed a pronounced Urbach-like exponential absorption tail approaching the bandedge. For the powders, the bandgap energies were larger than those for the crystalline and amorphous …
Amorphous ultra-wide bandgap ZnOx thin films deposited at cryogenic temperatures
Crystalline wurtzite zinc oxide (w-ZnO) can be used as a wide band gap semiconductor for light emitting devices and for transparent or high temperature electronics. The use of amorphous zinc oxide (a-ZnO) can be an advantage in these applications. In this paper we report on X-ray amorphous a-ZnOx thin films (~500 nm) deposited at cryogenic temperatures by reactive magnetron sputtering. The substrates were cooled by a nitrogen flow through the copper substrate holder during the deposition. The films were characterized by X-ray diffraction (XRD), Raman, infrared, UV-Vis-NIR spectroscopies, and ellipsometry. The a-ZnOx films on glass and Ti substrates were obtained at the substrate holder temp…
Enhanced Reflectivity Change and Phase Shift of Polarized Light: Double Parameter Multilayer Sensor
Herein, the concept of point of darkness based on polarized light phase difference and absorption of light is demonstrated by simulations using low refractive index and extinction coefficient semiconductor and dielectric, and high refractive index nonoxidizing metal multilayer thin film structures. Several multilayer sensor configurations show great sensitivity to thickness and refractive index variation of the detectable material by measuring the reflectivity ratio {\Psi} and phase shift {\Delta}. Focus is on such multilayers, which have sensitivity to both parameters ({\Psi}, {\Delta}) in the visible spectral range, thus opening the possibility for further research on a new biomedical sen…
Thermo-optical studies of NaNbO3thin films
Thermo-optical studies of sodium niobate NaNbO3 (NN) thin films, deposited by the pulsed laser ablation technique on Si/SrRuO3 substrates, were performed by spectroscopic ellipsometry in the temperature range 300-550°C. Optical constants at the room temperature were measured in the spectral range 250-1000 nm. Substantial changes in the refractive index temperature behaviour (taken at λ = 300 nm) were found at temperatures 370, 445, 503, 520, and 532°C, where the first and the last temperatures are the phase transitions P → R and S → T1, respectively. Other temperatures (445, 503, and 520°C) are suggested as the points of some local structural changes in the NN film.