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Ultra sensitive magnetic sensors integrating the giant magnetoelectric effect with advanced microelectronics.

机译：超灵敏的磁传感器将巨大的磁电效应与先进的微电子技术相结合。

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摘要

This dissertation investigates approaches to enhance the performance, especially the sensitivity and signal to noise ratio of magnetoelectric sensors, which exploits the magnetoelectric coupling in magnetostrictive and piezoelectric laminate composites. A magnetic sensor is a system or device that can measure the magnitude of a magnetic field or each of its vector components. Usually the techniques encompass many aspects of physics and electronics. The common technologies used for magnetic field sensing include induction coil sensors, fluxgate, SQUID (superconducting quantum interference device), Hall effect, giant magnetoresistance, magnetostrictive/piezoelectric composites, and MEMS (microelectromechanical systems)-based magnetic sensors. Magnetic sensors have found a broad range of applications for many decades. For example, ultra sensitive magnetic sensors are able to detect tiny magnetic fields produced outside the brain by the neuronal currents which can be used for diagnostic application. Measuring the brain's magnetic field is extremely challenging because they are so weak, have strengths of 0.1–1 pT and thus requiring magnetic sensors with sub-picotesla sensitivity. In fact, to date, these measurements can only performed with the most sensitive magnetic sensors, i.e., SQUID. However, such detectors need expensive and cumbersome cryogenics to operate. Additionally, the thermal insulation of the sensors prevents them from being placed very closed to the tissues under study, thereby preventing high-resolution measurement capability. All of these severely limit their broad usage and proliferation for biomedical imaging, diagnosis, and research.;A novel ultra-sensitive magnetic sensor capable of operating at room temperature is investigated in this thesis. Magnetoelectric effect is a material phenomenon featuring the interchange between the magnetic and electric energies or signals. The large ME effect observed in ME composites, especially the ME laminates consisting of magnetostrictive and piezoelectric components shows a promise to make novel ultra-sensitive magnetic sensors capable of operating at room temperature. To achieve such a high sensitivity (∼pT level), piezoelectric sensors are materialized through ME composite laminates, provided piezo-sensors are among the most sensitive while being passive devices at the same time. To further improve the sensitivity and reduce the 1f noise level, several approaches are used such as magnetic flux concentration effect, which is a function of the Metglas sheet aspect ratio, and resonance enhancement. Taking advantage of this effect, the ME voltage coefficient α ME=21.46 V/cm·Oe for Metglas 2605SA1/PVDF laminates and αME=46.7 V/cm·Oe for Metglas 2605CO/PVDF laminates. The resonance response of Metglas/PZT laminates in FF (Free-Free), FC (Free-Clamped), and CC (Clamped-Clamped) modes are also investigated. αME=301.6 V/cm·Oe and the corresponding SNR=4×107 Hz /Oe are achieved for FC mode at resonance frequencies. In addition to this, testing setups were built to characterize the magnetic sensors. LABVIEW codes were also developed to automatize the measurements and consequently get accurate results.;Then two commonly used integration methods, i.e., hybrid method and system in package (SIP), are discussed. Then the intrinsic noise analysis including dielectric loss noise, which dominates the intrinsic noise sources, and magnetostrictive noise is introduced. A charge mode readout circuit is made for hybrid method and a voltage mode readout circuit is made for SIP method. For sensors, since SNR is very important since it determines the minimum signal it can detect, the SNR of each configuration is discussed in detail. For charge mode circuit, by taking advantage of the multilayer PVDF configuration, SNR=7.2×10 5 Hz /Oe is achieved at non-resonance frequencies and SNR=2×10 7 Hz /Oe is achieved at resonance frequencies. For voltage mode circuit, a constant SNR=3×103 Hz /Oe is achieved at non-resonance frequencies. Both of the advantages and disadvantages of each method are also discussed.;Piezoelectric single crystal PMN-PT with optimum orientation and cut direction is developed to increase the ME coefficient α ME and reduce the intrinsic dielectric loss noise, consequently to improve the SNR of the ME sensors. For Metlgas/PMN-PT laminates, SNR=3.9×10 6 Hz /Oe is achieved at non-resonance frequencies and SNR=7.3×10 8 Hz /Oe is achieved at resonance frequencies.
机译：本文研究了提高磁电传感器性能，特别是灵敏度和信噪比的方法，该方法利用了磁致伸缩和压电层压复合材料中的磁电耦合。磁传感器是可以测量磁场强度或其矢量分量的系统或设备。通常，这些技术涵盖了物理和电子学的许多方面。用于磁场感应的常用技术包括感应线圈传感器，磁通门，SQUID（超导量子干涉装置），霍尔效应，巨磁阻，磁致伸缩/压电复合材料以及基于MEMS（微机电系统）的磁传感器。磁传感器已经发现了数十年的广泛应用。例如，超灵敏的磁传感器能够检测神经元电流在脑外产生的微小磁场，这些磁场可用于诊断应用。测量大脑的磁场非常具有挑战性，因为它们是如此之弱，强度为0.1–1 pT，因此需要具有低于皮克特斯拉灵敏度的磁传感器。实际上，迄今为止，这些测量只能使用最灵敏的磁传感器即SQUID进行。但是，这样的检测器需要昂贵且麻烦的低温操作。另外，传感器的隔热层可防止它们非常靠近要研究的组织放置，从而妨碍了高分辨率的测量能力。所有这些都严重限制了它们在生物医学成像，诊断和研究中的广泛应用和扩散。本论文研究了一种能够在室温下工作的新型超灵敏磁传感器。磁电效应是一种物质现象，具有磁能和电能或信号之间的交换。在ME复合材料中观察到的大ME效应，尤其是由磁致伸缩和压电组件组成的ME层压板显示出有望制造出能够在室温下运行的新型超灵敏磁传感器。为了实现如此高的灵敏度（pT级），压电传感器通过ME复合材料层压材料实现，前提是压电传感器是最敏感的传感器，同时又是无源器件。为了进一步提高灵敏度并降低 1 f 噪声水平，有几种方法使用诸如Metglas片长宽比的函数的磁通量集中效应和共振增强。利用此效应，Metglas 2605SA1 / PVDF层压板和α ME 的ME电压系数α ME = 21.46 V / cm·Oe对于Metglas 2605CO / PVDF层压板，sub> = 46.7 V / cm·Oe。还研究了Metglas / PZT层压板在FF（自由-自由），FC（自由-夹紧）和CC（夹紧-夹紧）模式下的共振响应。 α ME = 301.6 V / cm·Oe和对应的SNR = 4×10 7 Hz / Oe。除此之外，还建立了测试装置来表征磁性传感器。还开发了LABVIEW代码以实现测量的自动化，从而获得准确的结果;然后讨论了两种常用的集成方法，即混合方法和系统级封装（SIP）。然后介绍了本征噪声分析，包括介电损耗噪声（主导本征噪声源）和磁致伸缩噪声。充电方式读出电路用于混合方式，电压方式读出电路用于SIP方式。对于传感器，由于SNR非常重要，因为它决定了可以检测的最小信号，因此将详细讨论每种配置的SNR。对于充电模式电路，通过利用多层PVDF配置，SNR = 7.2×10 5 Hz / Oe在非谐振频率下获得，并且SNR = 2×10 7 Hz / Oe。对于电压模式电路，恒定SNR = 3×10 3 Hz / Oe在非谐振频率下获得。讨论了每种方法的优缺点。开发了具有最佳取向和切割方向的压电单晶PMN-PT，以增加ME系数α ME 和降低固有的介电损耗噪声，从而提高ME传感器的SNR。用于Metlgas / PMN-PT层压板，SNR = 3.9×10 6 Hz / Oe在非共振频率和SNR = 7.3×10 8 Hz / Oe达到共振频率。

著录项

  • 作者

    Fang, Zhao.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Engineering Electronics and Electrical.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 159 p.
  • 总页数 159
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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