Marina Zelner - Academia.edu (original) (raw)

Papers by Marina Zelner

Power handling capability of tunable microwave devices employing ferroelectric BaxSr1-xTiO3 film-... more Power handling capability of tunable microwave devices employing ferroelectric BaxSr1-xTiO3 film-based varactors: was experimentally measured and analyzed. A microstrip resonator, excited by either harmonic or two-tone microwave signals of elevated power, was selected as an example of tunable test fixture. The nonlinear distortion of the resonant curve under microwave pulsed power and generation of the third-order intermodulation distortion products in microwave resonator, using ferroelectric varactors were measured. Formulas to estimate power handling capability connected with the microwave electric field dielectric nonlinearity and the ferroelectric film overheating are derived for the tunable microwave devices based on ferroelectric films

The impact of the residual strain induced by the thermal strain on the dielectric tunability was ... more The impact of the residual strain induced by the thermal strain on the dielectric tunability was systematically studied for rf sputtered ͑100͒-one-axis-oriented polycrystalline ͑Ba 0.5 Sr 0.5 ͒TiO 3 films. These films were grown on various substrates with different thermal expansion coefficients ͓␣ ͑sub͒ ͔ covered with a stack of ͑100͒ c SrRuO 3 / ͑100͒ c LaNiO 3 / ͑111͒Pt layers. The residual strain was ascertained to linearly increase with the increase in ␣ ͑sub͒ by enhancement of the surface-normal lattice spacing of ͑Ba 0.5 Sr 0.5 ͒TiO 3 and Pt. Dielectric tunability of the films also linearly increased with the increase in ␣ ͑sub͒. These results clearly demonstrate that dielectric tunability tailoring of the ͑Ba 0.5 Sr 0.5 ͒TiO 3 films can be achieved by using residual thermal strain.

Proceedings of the 13th IEEE International Symposium on Applications of Ferroelectrics, 2002. ISAF 2002., 2002

ABSTRACT (Ba0.7SrO0.3)TiO3 (BST) double layer capacitors with Pt electrodes were fabricated under... more ABSTRACT (Ba0.7SrO0.3)TiO3 (BST) double layer capacitors with Pt electrodes were fabricated under identical conditions on different substrates: SiO2/Si(111), r-plane sapphire, polycrystalline alumina Al2O3 (99.6%), Zirconia/Yttria Stabilized Alumina (ZYSA) and glazed polycrystalline alumina. The formation of the crystalline structure of BST films, grown by metal-organic decomposition (MOD) at various thermal processing conditions, leads to significant change in the dielectric properties of the BST films. By preparing BST films of the same thickness and under the same processing conditions, we observed that they possess higher capacitance when grown on all types of alumina-based substrates compared to those on SiO2/Si substrates. The higher capacitance on alumina were always associated with larger dissipation factors, and lower or similar leakage current densities. The final tuning of dielectric properties of BST double layer capacitors on non-silicon substrates was correlated to the processing conditions. Furthermore, the processing parameters and the type of lower electrode should be optimized individually for each specific substrate. The lowest achieved leakage current density of Pt/BST/Pt capacitor (500×500 μm2) on glazed alumina was 2.8×10-9 A/cm2 at 200 kV/cm with capacitance per unit area of 27 fF/μm2.

2005 European Microwave Conference, 2005

... 88, no. 9, pp. 5334-5342, 2000. [2] IP Koutsaroff, T. Bernacki, M. Zelner, A. Cervin-Lawry, A... more ... 88, no. 9, pp. 5334-5342, 2000. [2] IP Koutsaroff, T. Bernacki, M. Zelner, A. Cervin-Lawry, A. Kassam, P. Woo, L. Woodward, and A. Patel, "Microwave properties of parallel plate capacitorsbased on (Ba,Sr)TiO3 thin films grown on SiO2/Al2O3 substrates," in Proceedings of ...

2008 38th European Microwave Conference, 2008

ABSTRACT Ferroelectric materials such as (Bax Sr1-x) TiO3 (BST) exhibit a non-zero piezoelectric ... more ABSTRACT Ferroelectric materials such as (Bax Sr1-x) TiO3 (BST) exhibit a non-zero piezoelectric coefficient under a DC field. The piezoelectric coefficient increases from 0 as the applied DC bias increases from 0V. This gives rise to electrostrictive resonance behaviour in capacitors fabricated with these materials. This paper presents the results of high frequency measurements and simulations of induced piezoelectricity for multilayer BST thin film structures under a 10V DC bias. The Mason model and transmission line theory is used as the basis of the simulation and our work extends it to include the effects of other layers in the passivated capacitor device. High-frequency capacitors with 100 nm thick (Ba0.5Sr0.5) TiO3 and Pt electrodes were fabricated on polycrystalline Al2O3 ceramic and Si substrates with an amorphous oxide buffer layer. Correlation between measurements and simulations allowed us to evaluate the piezoelectric coefficient, its switchability and tunability as well as the contribution of the multilayer film structure to the electrostrictive resonance behaviour. The model fits very well with the measurements and can be used to adjust the resonance peaks to the desired frequencies.

2007 Sixteenth IEEE International Symposium on the Applications of Ferroelectrics, 2007

ABSTRACT The impact of the residual strain induced by the thermal strain on the dielectric tunabi... more ABSTRACT The impact of the residual strain induced by the thermal strain on the dielectric tunability was systematically studied for (100)-one-axis-oriented polycrystalline (Ba0.5Sr0.5)TiO3 films. These films were grown on various substrates with different thermal expansion coefficients [a(sub.)] covered with a stack of (100)cSrRuO3/(100) cLaNiO3/(111)Pt layers. The residual strain was ascertained to linearly increase with the increase in a(sub.) by enhancement of the surface-normal lattice spacing of (Ba0.5Sr0.5)TiO3 and Pt. Dielectric tunability of the films also linearly increased with the increase in a(sub.). These results clearly demonstrate that dielectric tunability tailoring of the (Ba0.5Sr0.5)TiO3 films can be achieved by using residual thermal strain.

Thin film voltage tunable ferroelectric capacitors on various substrates show significant promise... more Thin film voltage tunable ferroelectric capacitors on various substrates show significant promise for use in high power microwave and other RF systems. The commercialization of ferroelectric components requires compliance with certain industry standards. TDDB (Time Dependent Dielectric Breakdown) is a fundamental measure of a dielectric material's aging characteristics under applied bias. Tuning is the main function of a tunable capacitor. Stability of tuning within a required temperature and voltage range is critical. This paper presents the results of a tuning degradation test. Acceleration factors and their limitations are discussed. The relationship of Mean Time to Failure (MTTF) and film grain structure is presented.

Two methods for the synthesis of CdTe nanoparticles in zirconia sol-gel films are demonstrated. T... more Two methods for the synthesis of CdTe nanoparticles in zirconia sol-gel films are demonstrated. The nanoparticles were obtained by chemical reduction of Te(IV) using reducing agent (hydrazine) or tin chloride. Particle sizes ranging from 6 to 20 nm in diameter could be prepared by varying the experimetal parameters. The size and crystalline structure of the particles were characterized by optical absorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The film morphology was characterized by scanning force microscopy. The film obtained by SnCl 2 method is smooth and homogeneous. The dense structure of CdTe nanoparticles of a few nm in diameter is revealed. The films prepared with hydrazine are porous as a result of evolution of the decomposition gaseous products during the reduction. Advantages and disadvantages of the two methods are discussed.

Ba 0.7 Sr 0.3 TiO 3 (BST) single and quadruple layer capacitors with Pt electrodes were fabricate... more Ba 0.7 Sr 0.3 TiO 3 (BST) single and quadruple layer capacitors with Pt electrodes were fabricated together on polycrystalline alumina substrates with a SiO 2-based multicomponent amorphous buffer layer (SiO 2 /Al 2 O 3). This paper presents the results of the characterization of these capacitors, to demonstrate their suitability for application as decoupling (high value) capacitors and as components in tunable RF applications (e.g., phase shifters and filters). BST films of different compositions, (Ba 0.7 Sr 0.3)TiO 3 and (Ba 0.5 Sr 0.5)TiO 3 , were grown by metal-organic decomposition (MOD) and RF magnetron reactive sputtering. The capacitance density of 90-140 nm thick BST films was in the range of 20 to 70 fF/µm 2. Parallel plate capacitors with areas from 16 µm 2 to 2.25 mm 2 were fabricated using photolithography and ion milling techniques. For large capacitors (0.125 to 2.25 mm 2), capacitance and tanδ were measured at low frequencies (1 KHz-1 MHz) using an LCR meter. Smaller capacitors (16 µm 2 to 3600 µm 2) were additionally characterized in the frequency range of 50 MHz-20 GHz. In such case, capacitance, tanδ and equivalent series resistance (ESR) were extracted from two port scattering parameters obtained using a vector network analyzer (VNA). The relationship between dielectric loss, tunability and calculated figure of merit vs. BST composition and deposition temperature was outlined. In addition, loss and ESR at high frequencies was investigated. The typical achieved leakage current density of sputtered BST films for 2.25 mm 2 capacitors fabricated on SiO 2 /Al 2 O 3 was 7.3x10-9 A/cm 2 at 300 kV/cm (65 fF/µm 2), about 2 times lower than for (Ba 0.7 Sr 0.3)TiO 3 films deposited by MOD (1.4x10-8 A/cm 2 at 300 kV/cm, 34.5 fF/µm 2). Furthermore, the tunability of (Ba 0.7 Sr 0.3)TiO 3 deposited by both methods on SiO 2 /Al 2 O 3 was ~60% at 350 kV/cm.

ABSTRACTDouble layer (DL) Ba0.7Sr0.3TiO3 (BST) capacitors with Pt electrodes have been fabricated... more ABSTRACTDouble layer (DL) Ba0.7Sr0.3TiO3 (BST) capacitors with Pt electrodes have been fabricated with similar growth conditions on different substrates. The substrates used in the present study were r-plane sapphire, polycrystalline alumina Al2O3 (99.6% and 96%), and glazed polycrystalline alumina. BST films were grown by metal-organic decomposition (MOD) method. By varying the annealing conditions which affects the formation of the crystalline structure, significant changes in the dielectric properties of the BST films have been observed. BST films were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Powder X-ray Diffractometer (PXRD). These observations showed that BST films grown at lower temperatures on alumina substrates exhibited the smallest grain size. BST films of the same thickness prepared under the same thermal processing conditions showed higher capacitance when grown on all types of alumina-based substrates compared to those deposited on control SiO2/Si. The higher capacitance on alumina was always associated with larger dissipation factor, and lower or similar leakage current density. The final tuning, of the dielectric properties of BST DL capacitors on non-silicon substrates, was correlated to the initial film formation temperature and post-annealing conditions of the BST films. The leakage current density, of DL BST capacitors fabricated on glazed alumina, becomes smallest when the BST processing temperature was lowered by 100 °C compared to the control SiO2/Si. The typical achieved leakage current density for 1500×1500 μm2 DL capacitors on glazed alumina was 3.8×10-9 A/cm2 at 250 kV/cm (36.5 fF/μm2), about 3 times lower than on SiO2/Si substrates (1.1×10-8 A/cm2 at 250 kV/cm, 31 fF/μm2).

Advances in Energy Transfer Processes - Proceedings of the 16th Course of the International School of Atomic and Molecular Spectroscopy, 2001

ABSTRACT Optical films doped by semiconductor nanocrystals and semiconductor nanocrystals with Eu... more ABSTRACT Optical films doped by semiconductor nanocrystals and semiconductor nanocrystals with Eu+3 and Tb+3 were prepared by the sol-gel method. The newly developed techniques for preparation of thin glass films of silica and zirconia doped by nanoparticles of CdS, CdSe are described. Intensification of rare earths (Eu+3, Tb+3) luminescence by their incorporation into semiconductor quantum dots of CdS is observed as compared to the same luminescence with the absence of quantum dots. The prepared materials were characterized by the optical absorption, luminescence and X-ray diffraction. The sizes of the particles varied from few tens to hundreds of angstroms depending on parameters of thermal treatment and precursor composition. The deviation from the average size in each case is about 10%. Quantum size effect is demonstrated.

Materials Letters, 2000

Semiconductor CdS particles were formed in ZrO films, together with Eu 3q and Tb 3q ions. The ste... more Semiconductor CdS particles were formed in ZrO films, together with Eu 3q and Tb 3q ions. The steady-state, as well as 2 the time-resolved luminescence, revealed that the intensity of emission of the REE is increased significantly in the presence of CdS particles. This phenomenon can be explained by energy transfer resulting from electron-hole recombination in the CdS to the REE. From the lifetime measurements, it is evident that this transfer occurs in the nanosecond scale.

Proceedings of the 13th IEEE International Symposium on Applications of Ferroelectrics, 2002. ISAF 2002., 2002

2005 European Microwave Conference, 2005

2008 38th European Microwave Conference, 2008

2007 Sixteenth IEEE International Symposium on the Applications of Ferroelectrics, 2007

Advances in Energy Transfer Processes - Proceedings of the 16th Course of the International School of Atomic and Molecular Spectroscopy, 2001

Materials Letters, 2000