Study of Hf—Al—O High-k Gate Dielectric Thin Films Grown on Si

Ultrathin amorphous films of Hf-aluminate (Hf—Al—O) have been deposited on p-type (100) Si substrates by pulsed-laser deposition. Transmission electron microscopy study revealed that for the films deposited in oxygen ambient with partial pressure of 1 × 10^?3 Pa, the amorphous structure of Hf—Al—O films is stable under rapid thermal annealing at temperatures up to at least 1000°C. Electrical properties have been characterized by means of high-frequency capacitance-voltage measurements at 1 MHz on the metal-oxide-semiconductor (MOS) capacitors using Pt dot electrode. The relative permittivity of the Hf—Al—O dielectric film is calculated approximately to be about 10 and the equivalent oxide thickness to SiO₂ is 30 Å. However, for the Hf—Al—O films deposited in a relatively higher vacuum condition (1 × 10^?4 Pa), islands of Hf silicide formed from interfacial reaction between the films and Si substrates. The formation of Hf silicide was attributed to the presence of Al oxide in the films that altered the Gibbs free energy for the reaction between the Hf atoms in the amorphous Hf—Al—O films and Si under an oxygen deficient condition. X-ray photoelectron spectroscope results suggested that there is Hf silicide formation in the interfacial region.     

Investigation of the High Frequency Properties of BST Thin Films—A Comparison of Three Different Commonly Used Methods

In this work three different commonly used high frequency measurement techniques for the determination of the electrical properties of BST thin films are compared. Two of the three setups determine the permittivity and the loss factor of planar sapphire capacitors by either measuring the reflection coefficient or the influence onto the resonance frequencies of two coupled microstrip resonators. The third setup utilizes the differential propagation constant of two identical coplanar wave guides (CPW) of different length to calculate the permittivity and the loss factor of the involved sapphire substrate. It is found that the latter method shows the best accuracy for the measurement of the permittivity and the loss factor of the sapphire substrates over a broad frequency range. Measurements of BST coated sapphire substrates are presented using this technique.     

Jiles–Atherton Hysteresis Approach in Analyzing the Effect of Field Suppression in Saturated Iron-core Superconducting Fault Current Limiters

Saturated iron-core superconducting fault current limiters (SISFCL) are becoming more popular in the recent years due to their ability of reliable, effective and instantaneous fault limiting. With a superior performance than conventional current limiting methods, the SISFCL is finding its application in modern transmission lines and distribution system. In the SISFCL, the iron core is forced into saturation using a superconducting coil carrying DC current. During a fault in the system, the high fluxes set up in the AC coils interact with the DC flux, thereby reducing the flux density abruptly. This sudden change in the flux density induces a high voltage across the DC coil, which may damage the DC current source as well as the superconducting material. As a protective measure, a field suppressor unit is used that disconnects the DC supply following a fault. In this paper, a mathematical model of the SISFCL is developed considering hysteresis and the effects of the field suppressor unit have been analyzed. The paper also aims to highlight the effects on the performance of SISFCL with varying hysteresis loops of the core material.     

Evaluation of Chemical Solution Deposited Ba x Sr 1−x TiO 3 Thin Films on LaAlO 3 in Tunable Microwave Devices

Epitaxial Ba x Sr 1 m x TiO 3 (BST) films grown on LaAlO 3 by several deposition methods have been tested in coupled microstrip phase shifters (CMPS) at frequencies from 10 to 24 GHz. To date the best performance for the devices has been achieved using Pulsed Laser Deposition (PLD). However, recently chemical solution deposition (CSD) methods such as sol-gel and Metal-Organic Chemical Liquid Deposition (MOCLD) have shown advances in fabricating BST films for tunable microwave applications. CSD processes promise improvements in cost, speed and area covered during BST film deposition. This paper compares over 35 BST films used in identical CMPS circuits. In this study, the highest measured figures of merit of phase shift per dB of loss for PLD, MOCLD and sol-gel CMPS are 49, 47 and 41°/dB respectively. While other phase shifter designs using BST films have surpassed these values, these data base of identical circuits allows us to compare the BST films. X-ray diffraction characterization for many of the BST films is also given.