多功能高溫超導量子干涉元件磁量計與梯度計之製作與特性研究

Abstract

After the discovery of high-transition-temperature superconducting (HTS) material, many HTS superconducting-quantum-interference-device (SQUID) systems have been constructed and applied to different applications such as nondestructive evaluation (NDE), scanning SQUID microscope (SSM), magnetocardiography (MCG), magnetoencephalography (MEG), low field nuclear magnetic resonance (NMR), etc. For practical applications, a multichannel system is more useful and powerful, especially in biomagnetic research. A multichannel system could perform a large area measurement and reduce measuring time. Alternatively, a multichannel system offers the possibility for the measurement of the gradient of magnetic field. In this work, I try to develop the new design of the high-Tc dc SQUID magnetometer to increase the practicability of SQUID. The basic physics of the dc SQUID magnetometer and gradiometer are introduced in the chapter 1. Before fabricating a high-Tc SQUID, it is very important to prepare the superconducting thin film with good quality. We use the pulsed laser deposition (PLD) to deposit the YBa2Cu3O7-δ thin film. The technique of PLD, the SQUID fabrication steps and the measurement processes are shown in the chapter 2. In the Chapter 3, the multifunctional high-Tc directly coupled SQUID magnetometers will be presented. This design contains four magnetometers on a chip. Moreover, these magnetometers can be used to construct four kinds of first-order electronic planar gradiometers or two kinds of second-order electronic planar gradiometers by using analog subtracting electronic circuits. The noise spectra of each magnetometer, two first-order electronic planar gradiometers, and a second-order planar gradiometer are measured. Next, we design two first-order planar gradiometers on a chip. The gradiometer is more stable than the magnetometer in a noisy environment. These two first-order planar gradiometers also can be connected to a second-order electronic planar gradiometer by using analog subtracting electronic circuits. The performance and the noise spectra of this device are shown in the chapter 4. Electric field modulated devices have been developed intensively in the semiconductor. Referring to the structure of the semiconductor field effect transistor (FET), we design a three terminal-like SQUID to investigate the electric field effect in SQUID. We find that the electric filed effect can affect the performance of SQUID. The details and the results of this experiment will be exhibited in the chapter 5.