Characterization of Metal-Insulator-Transition (MIT) Phase Change Materials (PCM) for Reconfigurable Components, Circuits, and Systems

Many microelectromechanical systems (MEMS) use metal contact micro-switches as part of their reconfigurable device design. These devices utilize a mechanical component that can wear down and fail over time. Metal insulator transition (MIT) materials, also known as phase change materials (PCMs), exhibit a reversible transition that can be used to replace the mechanical component in reconfigurable devices. In the presence of a thermal or electric field stimuli, the PCMs will transition back and forth between a crystalline and amorphous state. During this transformation, the resistivity, reflectivity, and Young\u27s modulus of the material drastically change. This research effort focuses on characterizing the stimuli required to transition germanium telluride (GeTe) and vanadium oxide (VOx). To do this, test structures were designed and microfabricated in AFIT\u27s class 1000 cleanroom. The resistivity of the GeTe films underwent a volatile transition from 1.4E3Ohm-cm down to 2.28Ohm-cm and a nonvolatile transition from 1.4E3Ohm-cm to 2.43E-3Ohm-cm when a thermal stimulus was applied. The reflectivity of the film also changed significantly when crystallized, increasing over 30%. Lastly, the Young\u27s modulus was measured and showed a 28% change during crystallization. After the materials were characterized, reconfigurable devices were designed to utilize the phase change properties of the PCMs

Characterizing Metal-Insulator-Transition (MIT) Phase Change Materials (PCM) for RF and DC Micro-switching Elements

Metal-insulator transition (MIT) phase-change materials (PCM) are material compounds that have the ability to be either conductors or insulators depending on external stimuli. A micromachined test structure for applying external electric fields across MIT wire segments was designed and fabricated. Using this novel test structure, Germanium Telluride (GeTe) and Vanadium Oxide (VOx) were successfully transitioned from a conductor to an insulator. The resistivity of the GeTe wire segments increased three to five orders of magnitude with ∼40 V applied to the parallel plates of the test structure. The VOx wires exhibited an order of magnitude transition in resistivity with ∼20 V applied. Characterization of both RF and DC switching performance of these MIT wire segments was completed and GeTe and VOx appear to be viable materials for micro-switching

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.Comment: Full report: 498 pages. Executive Summary: 14 pages. More information about HabEx can be found here: https://www.jpl.nasa.gov/habex

Characterizing Metal Insulator Transition (MIT) Materials for Use as Micro-Switch Elements

Metal insulator transition (MIT) materials, or phase change materials (PCM) are material compounds that have the ability to be either conductors or insulators. Vanadium dioxide (VO2) and germanium telluride (GeTe) exhibit such a transition property. These materials have ferroelectric properties as well as a variable resistivity. The ability to vary the resistance of a single material is useful when designing integrated circuits on the micro scale. By varying the temperature or the electric field across these materials, we are able to change the resistivity within a portion of a line. This can in turn be used to create a switch within a wire. In order to measure these changing properties, we developed novel surface micromachined test structures capable of using a variety of MIT materials. By varying the electric field or the thermal gradient across an area of the wire segment, we were able to adjust the resistivity of the material. Therefore, by tailoring the properties of specific portions of a conductor, we were able to control current flow in a circuit without needing a micro-mechanical or a microelectronic device

Unique Fabrication Method for Novel MEMS Micro-contact Structure

Microelectromechanical systems (MEMS) switch reliability is a major obstacle for large-volume commercial applications despite offering lower power consumption, better isolation, and lower insertion loss compared to conventional field-effect transistors and PIN diodes (Yang et al. IEEE J Microelectromech Syst 18(2): 287–295, 2009). To enhance reliability and performance, MEMS researchers focus on the micro-contact lifecycle evolution based on material choice and design of the micro-contact. In order to examine the micro-contact phenomena and physics, a novel DC MEMS micro-contact structure has been developed. The structure is composed of a Gold contact pad and a layered Gold beam. The reliability and performance of a micro-contact is directly influenced by its ability to make and break its electrical connection. Its ability to separate from the contact area is a function of applied force, adhesion forces, and the restoring force. The layered Gold micro-contact structure was fabricated and the processing steps, performance, and experimental results of the device reliability of the device are presented