skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Reliability of piezoelectric films for MEMS
Abstract Thin films based on PbZr1−xTixO3and K1−xNaxNbO3are increasingly being commercialized in piezoelectric MEMS due to the comparatively low drive voltages required relative to bulk actuators, as well as the facile approach to making sensor or actuator arrays. As these materials are incorporated into devices, it is critically important that they operate reliably over the lifetime of the system. This paper discusses some of the factors controlling the electrical and electromechanical reliability of lead zirconate titanate (PZT)-based piezoMEMS films. In particular, it will be shown the gradients in the Zr/Ti ratio through the depth of the films are useful in increasing the lifetime of the films under DC electrical stresses.  more » « less
Award ID(s):
1841453 1841466
PAR ID:
10467295
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
IOP Publishing Ltd.
Date Published:
Journal Name:
Japanese Journal of Applied Physics
Volume:
62
Issue:
SM
ISSN:
0021-4922
Page Range / eLocation ID:
SM0802
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract The pursuit of smaller, energy‐efficient devices drives the exploration of electromechanically active thin films (<1 µm) to enable micro‐ and nano‐electromechanical systems. While the electromechanical response of such films is limited by substrate‐induced mechanical clamping, large electromechanical responses in antiferroelectric and multilayer thin‐film heterostructures have garnered interest. Here, multilayer thin‐film heterostructures based on antiferroelectric PbHfO3and ferroelectric PbHf1‐xTixO3overcome substrate clamping to produce electromechanical strains >4.5%. By varying the chemistry of the PbHf1‐xTixO3layer (x = 0.3‐0.6) it is possible to alter the threshold field for the antiferroelectric‐to‐ferroelectric phase transition, reducing the field required to induce the onset of large electromechanical response. Furthermore, varying the interface density (from 0.008 to 3.1 nm−1) enhances the electrical‐breakdown field by >450%. Attaining the electromechanical strains does not necessitate creating a new material with unprecedented piezoelectric coefficients, but developing heterostructures capable of withstanding large fields, thus addressing traditional limitations of thin‐film piezoelectrics. 
    more » « less
  2. Abstract Silk nanofibers (SNFs) from abundant sources are low‐cost and environmentally friendly. Combined with other functional materials, SNFs can help create bioelectronics with excellent biocompatibility without environmental concerns. However, it is still challenging to construct an SNF‐based composite with high conductivity, flexibility, and mechanical strength for all SNF‐based electronics. Herein, this work reports the design and fabrication of Ti3C2Tx‐silver@silk nanofibers (Ti3C2Tx‐Ag@SNF) composites with multi‐dimensional heterogeneous conductive networks using combined in situ growth and vacuum filtration methods. The ultrahigh electrical conductivity of Ti3C2Tx‐Ag@SNF composites (142959 S m−1) provides the kirigami‐patterned soft heaters with a rapid heating rate of 87 °C s−1. The multi‐dimensional heterogeneous network further allows the creation of electromagnetic interference shielding devices with an exceptionally high specific shielding effectiveness of 10,088 dB cm−1. Besides working as a triboelectric layer to harvest the mechanical energy and recognize the hand gesture, the Ti3C2Tx‐Ag@SNF composites can also be combined with an ionic layer to result in a capacitive pressure sensor with a high sensitivity of 410 kPa−1in a large range due to electronic‐double layer effect. The applications of the Ti3C2Tx‐Ag@SNF composites in recognizing human gestures and human‐machine interfaces to wirelessly control a trolley demonstrate the future development of all SNF‐based electronics. 
    more » « less
  3. Abstract Alloying selected layered transitional metal trichalcogenides (TMTCs) with unique chain‐like structures offers the opportunities for structural, optical, and electrical engineering thus expands the regime of this class of pseudo‐one‐dimensional materials. Here, the novel phase transition in anisotropic Nb(1−x)TixS3alloys is demonstrated for the first time. Results show that Nb(1−x)TixS3can be fully alloyed across the entire composition range from triclinic‐phase NbS3to monoclinic‐phase TiS3. Surprisingly, incorporation of a small concentration of Ti (x ≈0.05–0.18) into NbS3host matrix is sufficient to induce triclinic to monoclinic transition. Theoretical studies suggest that Ti atoms effectively introduce hole doping, thus rapidly decreases the total energy of monoclinic phase and induces the phase transition. When alloyed, crystalline and optical anisotropy are largely preserved as evidenced by high resolution transmission electron microscopy and angle‐resolved Raman spectroscopy. Further Raman measurements identify Raman modes to determine crystalline anisotropy direction and offer insights into the degree of anisotropy. Overall results introduce Nb(1−x)TixS3as a new and easy phase change material and mark the first phase engineering in anisotropic van der Waals (vdW) trichalcogenide systems for their potential applications in two‐dimensional superconductivity, electronics, photonics, and information technologies. 
    more » « less
  4. Abstract MXenes constitute a rapidly growing family of 2D materials that are promising for optoelectronic applications because of numerous attractive properties, including high electrical conductivity. However, the most widely used titanium carbide (Ti3C2Tx) MXene transparent conductive electrode exhibits insufficient environmental stability and work function (WF), which impede practical applications Ti3C2Txelectrodes in solution‐processed optoelectronics. Herein, Ti3C2TxMXene film with a compact structure and a perfluorosulfonic acid (PFSA) barrier layer is presented as a promising electrode for organic light‐emitting diodes (OLEDs). The electrode shows excellent environmental stability, highWFof 5.84 eV, and low sheet resistanceRSof 97.4 Ω sq−1. The compact Ti3C2Txstructure after thermal annealing resists intercalation of moisture and environmental contaminants. In addition, the PFSA surface modification passivates interflake defects and modulates theWF. Thus, changes in theWFandRSare negligible even after 22 days of exposure to ambient air. The Ti3C2TxMXene is applied for large‐area, 10 × 10 passive matrix flexible OLEDs on substrates measuring 6 × 6 cm. This work provides a simple but efficient strategy to overcome both the limited environmental stability and lowWFof MXene electrodes for solution‐processable optoelectronics. 
    more » « less
  5. Abstract MXenes, a family of 2D transition‐metal carbides and nitrides, have excellent electrical conductivity and unique optical properties. However, MXenes oxidize in ambient conditions, which is accelerated upon heating. Intercalation of water also causes hydrolysis accelerating oxidation. Developing new tools to readily characterize MXenes’ thermal stability can enable deeper insights into their structure–property relationships. Here, in situ spectroscopic ellipsometry (SE) is employed to characterize the optical properties of three types of MXenes (Ti3C2Tx, Mo2TiC2Tx, and Ti2CTx) with varied composition and atomistic structures to investigate their thermal degradation upon heating under ambient environment. It is demonstrated that changes in MXene extinction and optical conductivity in the visible and near‐IR regions correlate well with the amount of intercalated water and hydroxyl termination groups and the degree of oxidation, measured using thermogravimetric analysis. Among the three MXenes, Ti3C2Txand Ti2CTx, respectively, have the highest and lowest thermal stability, indicating the role of transition‐metal type, synthesis route, and the number of atomic layers in MXene flakes. These findings demonstrate the utility of SE as a powerful in situ technique for rapid structure–property relationship studies paving the way for the further design, fabrication, and property optimization of novel MXene materials. 
    more » « less