The design of microelectromecanical systems (MEMS) and micro-opto-electromechanical systems (MOEMS) are often
materials-limited with respect to the efficiency and capability of the material. Graphene, a one atom thick honeycomb
lattice of carbon, is a highly desired material for MEMS applications. Relevant properties of graphene include the
material's optical transparency, mechanical strength, energy efficiency, and electrical and thermal conductivity due to its
electron mobility. Aforementioned properties make graphene a strong candidate to supplant existing transparent
electrode technology and replace the conventionally used material, indium-tin oxide. In this paper we present
preliminary results on work toward integration of graphene with MEMS structures.
We are studying mechanical exfoliation of highly ordered pyrolytic graphite (HOPG) crystals by repeatedly applying and
separating adhesive materials from the HOPG surface. The resulting graphene sheets are then transferred to silicon oxide
substrate using the previously applied adhesive material. We explored different adhesive options, particularly the use of
Kapton tape, to improve the yield of graphene isolation along with chemical cross-linking agents which operate on a
mechanism of photoinsertion of disassociated nitrene groups. These perfluorophenyl nitrenes participate in C=C addition
reactions with graphene monolayers creating a covalent binding between the substrate and graphene. We are focusing on
maximizing the size of isolated graphene sheets and comparing to conventional exfoliation. Preliminary results allow
isolation of few layer graphene (FLG) sheets (n<3) of approximately 10μm x 44μm. Photolithography could possibly be
utilized to tailor designs for microshutter technology to be used in future deep space telescopes.
We have successfully fabricated a superconducting transition edge sensor (TES), bolometer that centers on the use of
electron-phonon decoupling (EPD) for thermal isolation. We have selected a design approach that separates the two
functions of far-infrared and THz radiative power absorption and temperature measurement, allowing separate
optimization of the performance of each element. We have integrated molybdenum/gold (Mo/Au) bilayer TES and ion
assisted thermally evaporated (IAE) bismuth (Bi) films as radiation absorber coupled to a low-loss microstripline from
niobium (Nb) ground plane to a twin-slot antenna structure. The thermal conductance (G) and the time constant for the
different geometry device have been measured. For one such device, the measured G is 1.16×10-10 W/K (± 0.61×10-
10 W/K) at 60 mK, which corresponds to noise equivalent power (NEP) = 1.65×10-18W/ √Hz and time constant of ~5 μs.
The microshutter array (MSA) is a key component in the James Webb Space Telescope Near Infrared Spectrometer
(NIRSpec) instrument. The James Webb Space Telescope is the next generation of a space-borne astronomy platform
that is scheduled to be launched in 2013. However, in order to effectively operate the array and meet the severe
operational requirements associated with a space flight mission has placed enormous constraints on the microshutter
array subsystem. This paper will present an overview and description of the entire microshutter subsystem including the
microshutter array, the hybridized array assembly, the integrated CMOS electronics, mechanical mounting module and
the test methodology and performance of the fully assembled microshutter subsystem. The NIRSpec is a European
Space Agency (ESA) instrument requiring four fully assembled microshutter arrays, or quads, which are independently
addressed to allow for the imaging of selected celestial objects onto the two 4 mega pixel IR detectors. Each
microshutter array must have no more than ~8 shutters which are failed in the open mode (depending on how many are
failed closed) out of the 62,415 (365x171) total number of shutters per array. The driving science requirement is to be
able to select up to 100 objects at a time to be spectrally imaged at the focal plane. The spectrum is dispersed in the
direction of the 171 shutters so if there is an unwanted open shutter in that row the light from an object passing through
that failed open shutter will corrupt the spectrum from the intended object.
KEYWORDS: James Webb Space Telescope, Spectrographs, Electronics, Galactic astronomy, Near infrared, Astronomical imaging, Camera shutters, Silicon, Space telescopes, Imaging spectroscopy
One of the James Webb Space Telescope's (JWST) primary science goals is to characterize the epoch of galaxy formation in
the universe and observe the first galaxies and clusters of galaxies. This goal requires multi-band imaging and spectroscopic
data in the near infrared portion of the spectrum for large numbers of very faint galaxies. Because such objects are
sparse on the sky at the JWST resolution, a multi-object spectrograph is necessary to efficiently carry out the required
observations. We have developed a fully programmable array of microshutters that will be used as the field selector
for the multi-object Near Infrared Spectrograph (NIRSpec) on JWST. This device allows apertures to be opened at the
locations of selected galaxies in the field of view while blocking other unwanted light from the sky background and bright
sources. In practice, greater than 100 objects within the field of view can be observed simultaneously. This field selection
capability greatly improves the sensitivity and efficiency of NIRSpec. In this paper, we describe the microshutter arrays,
their development, characteristics, fabrication, testing, and progress toward delivery of a flight-qualified field selection
subsystem to the NIRSpec instrument team.
We have developed microshutter array systems at NASA Goddard Space Flight Center for use as multi-object
aperture arrays for a Near-Infrared Spectrometer (NIRSpec) instrument. The instrument will be carried on the
James Webb Space Telescope (JWST), the next generation of space telescope, after the Hubble Space
Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light from
objected galaxies in space with high efficiency and high contrast. Arrays are close-packed silicon nitride
membranes with a pixel size close to 100x200 μm. Individual shutters are patterned with a torsion flexure
permitting shutters to open 90 degrees with minimized stress concentration. In order to enhance optical
contrast, light shields are made on each shutter to prevent light leak. Shutters are actuated magnetically,
latched and addressed electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining
and packaged utilizing a novel single-sided indium flip-chip bonding technology. The MSA flight system
consists of a mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays. The system will be placed in
the JWST optical path at the focal plane of NIRSpec detectors. MSAs that we fabricated passed a series of
qualification tests for flight capabilities. We are in the process of making final flight-qualified MSA systems
for the JWST mission.
KEYWORDS: Camera shutters, Electrodes, Magnetism, Indium, Silicon, James Webb Space Telescope, Optical fabrication, Metals, Microelectromechanical systems, Space telescopes
A complex MEMS device, microshutter array system, is being developed at NASA Goddard Space Flight
Center for use as an aperture array for a Near-Infrared Spectrometer (NirSpec). The instrument will be
carried on the James Webb Space Telescope (JWST), the next generation of space telescope after Hubble
Space Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light
with high efficiency and high contrast. Arrays are close-packed silicon nitride membranes with a pixel size
close to 100x200 &mgr;m. Individual shutters are patterned with a torsion flexure permitting shutters to open 90
degrees with a minimized mechanical stress concentration. Light shields are made on to each shutter for light
leak prevention so to enhance optical contrast. Shutters are actuated magnetically, latched and addressed
electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining technologies and
packaged using single-sided indium flip-chip bonding technology. The MSA flight concept consists of a
mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays placed in the JWST optical path at the focal
plane.
KEYWORDS: Camera shutters, Electrodes, Indium, Magnetism, Silicon, James Webb Space Telescope, Optical fabrication, Metals, Microelectromechanical systems, Space telescopes
MEMS microshutter arrays (MSAs) are being developed at NASA Goddard Space Flight Center for use as an aperture
array for the Near-Infrared Spectrometer (NirSpec). The instruments will be carried on the James Webb Space
Telescope (JWST), the next generation of space telescope after Hubble Space Telescope retires. The microshutter arrays
are designed for the selective transmission of light with high efficiency and high contrast. Arrays are close-packed
silicon nitride membranes with a pixel size of 105x204 μm. Individual shutters are patterned with a torsion flexure
permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are made on each
shutter for light leak prevention to enhance optical contrast. Shutters are actuated magnetically, latched and addressed
electrostatically. The shutter arrays are fabricated using MEMS technologies. Single-side indium flip chip bonding is
performed to attach microshutter arrays to substrates.
KEYWORDS: Camera shutters, Electrodes, Silicon, Metals, Magnetism, James Webb Space Telescope, Optical fabrication, Microelectromechanical systems, Semiconducting wafers, Reactive ion etching
Micro Electromechanical System (MEMS) microshutter arrays are being developed at NASA Goddard Space Flight Center for use as a field selector of the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST). The microshutter arrays are designed for the spontaneous selection of a large number of objects in the sky and the transmission of light to the NIRSpec detector with high contrast. The JWST environment requires cryogenic operation at 35 K. Microshutter arrays are fabricated out of silicon-on-insulator (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100 x 200 μm. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are processed for blocking light from gaps between shutters and frames. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes multi-layer metal depositions, the patterning of magnetic stripes and shutter electrodes, a reactive ion etching (RIE) to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, followed by a deep RIE (DRIE) back-etch to form mechanical supporting grids and release shutters from the silicon substrate. An additional metal deposition is used to form back electrodes. Shutters are actuated by a magnetic force and latched using an electrostatic force. Optical tests, addressing tests, and life tests are conducted to evaluate the performance and the reliability of microshutter arrays.
KEYWORDS: Camera shutters, James Webb Space Telescope, Electrodes, Silicon, Spectrographs, Magnetism, Prototyping, Failure analysis, Near infrared, Galactic astronomy
The Near Infrared Spectrograph (NIRSpec) for the James Webb Space Telescope (JWST) is a multi-object spectrograph operating in the 0.6-5.0 μm spectral range. One of the primary scientific objectives of this instrument is to measure the number and density evolution of galaxies following the epoch of initial formation. NIRSpec is designed to allow simultaneous observation of a large number of sources, vastly increasing the capability of JWST to carry out its objectives. A critical element of the instrument is the programmable field selector, the Microshutter Array. The system consists of four 175 x 384 close packed arrays of individually operable shutters, each element subtending 0.2” x 0.4”on the sky. This device allows simultaneous selection of over 200 candidates for study over the 3.6’ x 3.6’ field of the NIRSpec, dramatically increasing its efficiency for a wide range of investigations. Here, we describe the development, production, and test of this critical element of the NIRSpec.
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