Devices with increased sensitivities are needed for various applications including the detection of chemical and biological agents. This paper presents the design of microelectromechanical systems (MEMS) devices that incorporate lead zirconate titanate (PZT) films in order to realize highly sensitive sensors. In this work, the piezoelectric properties of the PZT are exploited to produce sensors that perform optimally for mass sensing applications. The sensor is designed to operate as a thin-film bulk acoustic resonator (TFBAR) whereas a piezoelectric is sandwiched between electrodes and senses a change in mass by measuring a change in resonance frequency. Modeling of the TFBAR sensor, using finite element analysis software COMSOL, was performed to examine optimal device design parameters and is presented in this paper. The effect of the PZT thickness on device resonance is also presented. The piezoelectric properties of the PZT is based on its crystal structure, therefore, optimization of the PZT film growth parameters is also described in this work. A detailed description of the fabrication process flow developed based on the optimization of the device design and film growth is also given. The TFBAR sensor consists of 150 nm of PZT, 150nm of silicon dioxide, silicon substrate, titanium/platinum bottom electrodes, and aluminum top electrodes. The top electrodes are segmented to increase the sensitivity of the sensor. The resonance frequency of the device is 3.2 GHz.
This paper presents the design of glucose sensors that will be integrated with advanced nano-materials, bio-coatings and
electronics to create novel devices that are highly sensitive, inexpensive, accurate, and reliable. In the work presented, a
glucose biosensor and its fabrication process flow have been designed. The device is based on electrochemical sensing
using a working electrode with bio-functionalized zinc oxide (ZnO) nano-rods. Among all metal oxide nanostructures,
ZnO nano-materials play a significant role as a sensing element in biosensors due to their properties such as high
isoelectric point (IEP), fast electron transfer, non-toxicity, biocompatibility, and chemical stability which are very crucial
parameters to achieve high sensitivity. Amperometric enzyme electrodes based on glucose oxidase (GOx) are used due
to their stability and high selectivity to glucose. The device also consists of silicon dioxide and titanium layers as well as
platinum working and counter electrodes and a silver/silver chloride reference electrode. Currently, the biosensors are
being fabricated using the process flow developed. Once completed, the sensors will be bio-functionalized and tested to
characterize their performance, including their sensitivity and stability.
We have studied ferroelectric properties of Pb (Zr0.6Ti0.4) O3(PZT)/SrTiO3 thin films grown on
platinized silicon substrates using pulsed-laser deposition and magnetron sputtering technique.
The spontaneous polarization (Ps) and remnant polarization (Pr) varies between 15.5 K and 100
K from 33-38 μC/cm2 and 25-30 μC/cm2,respectively. Similar values of Ps and Pr were also
observed until temperature reached to 300K. However, more pronounced ferroelectric hysteresis
loops were observed between T= 323 to 353 K. The Ps and Pr remain around 36-40 μC/cm2and
23-28 μC/cm2, respectively, between T = 323 to 353 K. The remnant polarization remains fairly
consistent over the chosen temperature range. X-ray diffraction and high-resolution microscopic
studies reveal that the Pb (Zr0.6Ti0.4) O3 layers are superior in crystalline quality than that of
SrTiO3. The PZT in multilayered films show remarkably enhanced polarization properties
relative to their single layers on the same substrates. The collective contribution of dipole
moments from each layer is the reason for such enhancement in polarization properties. This
growth strategy may be very useful for fabrication of sensitive sensing and other relevant
devices.
For many sensors, bio-sensors, and probes, it is critical to provide a suitable power
source nano or micro scale feature size, flexible structure, and physiologically
friendly materials. In this study, rectenna array was considered as a power source
using microwave that transmits through the tissues of humans or animals. In
addition, biological effects on humans and animals are discussed as well.
Multicomponent semiconductor oxides mainly composed of elements like indium, zinc, tin or gallium are very
promising new class of materials for application in transparent electronics, multifunctional sensors and other electronic
applications. The major characteristic of these materials is high mobility, and the electrical behavior is a consequence of
a conduction band primarily derived from spherically symmetric heavy-metal cationns orbital with (n-1)d10ns0 (n ≥4)
electronic configuration. The carrier transport becomes insensitive to the degree of disorder of the film, and makes this
class of quasi-polycrystalline and amorphous semiconductors attractive for numerous applications.We report here on the
environmental sensing, such as ultra-violet-radiation and various gases of pulsed-laser deposited composite
semiconductor films. These films demonstrate outstanding sensing capability from measuring the surface resistivity
taking into account the absorption of sensing species. Our results show new possibilities for the low-cost high
performance environmental sensors for numerous potential applications. The details of the results will be presented.
Sensor arrays for bio/chemical sensing generally incorporate different types of sensors with different substrate
coatings, enabling increased sensor sensitivity and selectivity. However, a challenge in using multiple sensor
systems is integration with RF electronic circuitry. This work presents the development of flexural plate
wave (FPW) acoustic devices implemented in a sensor array and co-integrated on a Si-CMOS circuit. FPWs
are highly sensitive to surface perturbations and indirectly sense analytes by detecting mass changes on the
sensing plate surface. The sensors are placed in an oscillating circuit, where changes in the oscillation
frequency are used to determine changes in the wave velocity due to mass loading by the analyte [1, 2]. Since
FPWs are generated in thin plates, these devices are highly sensitive to loading and exhibit the highest mass
sensitivities of any acoustic wave device [1, 2]. In the work presented, FPWs are fabricated on Si/SiO2/Si
native substrates, with the interdigitated transducers (IDTs) isolated from the active sensing surface. This
innovative design enables the sensors to be fabricated and then separated from the native substrate, transferred,
and bonded to the host Si-CMOS circuit. Thus, a new approach for the heterogeneous integration of FPW
sensors and circuitry is provided. Following integration, the FPWs can be customized with either chemical
membranes or biological functionalization. Moreover, this novel approach allows each sensor to be
optimized independently before being connected to the host substrate. This paper presents the design,
development, and integration process of an FPW sensor on Si-CMOS circuitry.
In light of the efforts to improve the performance of micromachined gyroscopes, this paper presents an investigation of
energy loss mechanisms in a SOI-based tuning-fork gyroscope, since these loss mechanisms dictate the value of the
mechanical Quality factor (Q) that has been identified as a critical determinant for achieving high-precision
performance. The numerical models of thermoelastic damping (TED) and anchor loss in the tuning-fork gyroscope
design are created in a FEM software, ANSYS/Multiphysics, according to a thermal-energy method and a separationand-
transfer method, respectively. The calculated results indicate that thermoelastic damping is the dominant loss while
anchor loss is negligible for the gyroscope design. In order to validate the created models, an experimental study on the
Q of the SOI-based tuning-fork gyroscope is consequently conducted. Comparison between the calculated results and the
measured data not only validates the numerical models, but also demonstrates the significant effect of fabrication process
on the final achievable Q values of the fabricated gyroscopes.
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