FABRICATION OF A NANOIMPRINT LITHOGRAPHY …chtm.unm.edu/incbnigert/nanophotonics/final papers/Datye...mask can be used to establish a fabrication process for the creation of nanoimprint
Post on 07-Jul-2020
0 Views
Preview:
Transcript
FABRICATION OF A NANOIMPRINT
LITHOGRAPHY MASK FOR IMPROVED
INFRARED DETECTORS
Isha Datye
Faculty Mentor: Dr. Sanjay Krishna
Graduate Student Mentor: John Montoya
The Center for High Technology Materials
The University of New Mexico, Albuquerque, NM 87131
Undergraduate Student of
The Department of Electrical and Computer Engineering
The University of Illinois at Urbana-Champaign
Urbana, IL 61801
ABSTRACT
Infrared photodetectors will require new technologies on the pixel level to provide
spectral information for the development of polarimetric and color images.
Current infrared photodetectors have nearly identical pixels over a broad spectral
range, resulting in black-and-white images. Scientists have been researching the
idea of an infrared retina, which is similar in function to cones in the human eye,
to produce multi-color images. A multi-color infrared camera system can be
accomplished by tuning individual pixels to a specific infrared “color” with the
aid of resonant structures patterned onto a photodetector’s surface. In addition, a
resonant structure can also improve a detector’s detectivity (D*, a measure of the
signal to noise ratio) or increase the operating temperature. One of the key
limitations of present day technology is the difficulty in making deep
subwavelength structures on a large scale. This research paper will focus on the
fabrication of a nanoimprint lithography mask to pattern resonant structures on a
scale that would make this multi-color technology ready for mass fabrication.
Research has been conducted on nanoimprint lithography and it has proven to be
a very efficient method to pattern structures on substrates with nanoscale
precision. The goal for this project was to pattern complicated resonant structures
on a substrate for the development of a multi-color infrared camera.
1. INTRODUCTION
The infrared region of the electromagnetic
spectrum has wavelengths from 0.75
microns to 1000 microns, longer than that of
visible light, which has wavelengths from
about 400 nm to 750 nm. Infrared detectors,
photodetectors that respond to infrared
radiation, have made significant
improvements since they were first
developed. Although there are several
different divisions within the infrared
region, the mid-wavelength (MWIR) and
long-wavelength (LWIR) infrared regions
are most important for infrared detector
technologies, since they include the
wavelengths at which most objects emit
radiation. For example, humans emit
radiation at a wavelength of 10 microns,
which is in the LWIR range [1]. There is an
increased emphasis on obtaining
hyperspectral and hyperpolarimetric
sensitive detectors for night vision, missile
tracking, medical diagnostics, and
environmental monitoring applications [1-
3]. The development of frequency-selective
surface technology on the pixel level has the
potential to provide enhanced infrared
detection for a desired wavelength of
radiation. Since it was first developed in the
1960s, infrared imaging technology,
especially in the area of focal plane arrays,
has made significant improvements in
producing an image. A focal plane array, a
device that converts an optical image into an
electrical signal that can then be processed
or stored, is the core of a long wavelength
imaging sensor [14]. The first generation
consisted of a single pixel or a one-
dimensional array of pixels that required a
mechanical sweep to produce a two-
dimensional image [1]. The second
generation now consists of a two
dimensional array of pixels to produce an
image, eliminating any need for moving
parts [1]. Third generation infrared cameras
will consist of a two dimensional array of
pixels that can pass spectral information at
room temperature, which is similar in
function to cones in the human eye [1].
Although significant improvements have
been made by the infrared detector
community, infrared images that are truly
multi-color are not readily available. A few
examples are given in figure 1 to
demonstrate images taken with conventional
photodetectors. As one can see, these images
are based on the intensity of light to provide
a false color image. Next generation
photodetectors will be able to provide
spectral information based on the
wavelength of light.
1.1 Background
In the past decade, new infrared detector
technologies, such as quantum dot infrared
photodetectors (QDIPs), quantum well
infrared photodetectors (QWIPs), quantum
dots-in-a-well infrared photodectors
(DWELL), and superlattice structures (SLS),
have been developed with ever increasing
operating temperatures. Infrared
photodetectors that can operate at room
temperature can significantly reduce their
cost of operation and therefore expand their
use for everyday applications [2]. QWIPs,
generally made with GaAs materials [17],
are already well-known and are available
commercially [3]. However, they have many
shortcomings and are generally thought to
be inferior to QDIPs [2]. For example,
QDIPs do not require diffraction gratings to
couple normally incident light [2]. Because
of this, there is one step less in the
Figure 1. (a) [18] Infrared images of the human
body showing areas of muscle pain in the back
and post-operative inflammation in the knee.
(b) [19] Infrared detector images showing a jet
helicopter and jet engine.
a) b)
fabrication of QDIPs than in the fabrication
of QWIPs. QDIPs are similar to QWIPs in
structure; the quantum well is substituted
with a quantum dot [17]. QDIPs are
generally constructed with InAs dots on
GaAs substrates [17]. An image of a QDIP
structure is shown in figure 2. QDIPs can
operate at higher temperatures as a result of
having a lower dark current [2].
The DWELL structure, a cross between
QDIPs and QWIPs with InAs quantum dots
in an InGaAs quantum well [3], has also
been proven to have low dark currents, and
higher operating temperatures [3]. Similar to
QDIPs, these detectors allow normal
incidence, which ultimately provides better
control over the operating wavelength [16].
A DWELL structure is shown in figure 3.
InAs/GaSb type-II strain layer superlattices
also operate at higher temperatures, have a
higher detectivity, high efficiency, and some
multi-color capability [2], although not on a
large scale. This is the most promising
technology, but it also the most expensive.
2. MOTIVATION FOR PROJECT
Although the current infrared detector
technologies have made many
improvements in their images, researchers
are still interested in exploring new
technologies that can take even better
images and can incorporate more elements
such as color, polarization, and dynamic
range.
Currently, all of the pixels in an infrared
camera are nearly identical, creating black-
and-white images instead of images of
different colors [15]. Scientists would like to
change this by integrating multispectral
capability on the pixel level. An example of
multispectral imaging is shown in figure 4.
They have been researching the concept of
an infrared retina, which would act similarly
to the cones in a human eye in the
information conveyed in the images [1]. In
order to create this infrared retina, either
plasmonics or matamaterials can be used.
Current infrared detector technology, can in
general, be improved with the aid of
resonant structures of a given design to
provide a higher operating temperature,
spectral information on the pixel level, and a
higher detectivity [3]. This project will focus
on the development of a nanoimprint
lithography mask for the fabrication of these
resonant structures. Initially, a simple
nanoimprint lithography mask will be
created to imprint an array of posts. These
simple structures can aid in the fabrication
Figure 3. Image of a quantum dots-in-a-well
structure, showing the InAs quantum dot in an
InGaAs quantum well.
Figure 2. [20] The image on the left shows a 10-
layer InGaAs/GaAs QDIP structure, and the
image on the right shows a diagram of a QDIP in
an electric field.
of surface plasmon (SP) diffraction gratings,
which have been shown to enhance the
signal received by an infrared photodetector
[13]. A simple nanoimprint lithography
mask can be used to establish a fabrication
process for the creation of nanoimprint
masks with complicated features, such as
metamaterials. Metamaterials are artificial
materials that have properties usually not
found in nature. They offer a huge
advantage over SP structures because they
can be created for pixels with a small size
[5]. They can be engineered to have a
negative index of refraction, meaning that
the light is bent around the object rather than
transmitted through or reflected away from
it [5]. Narrow-band perfect absorbers can be
created because of the electric permittivity
and magnetic permeability of metamaterials
[5]. They can control and interact with
infrared radiation only if their structures
have wavelengths similar to those of the
infrared light waves with which they interact
[5].
3. RESEARCH OBJECTIVE
This project focused on the fabrication of a
mask through different forms of lithography,
such as interferometric and electron beam
lithography, to pattern metamaterial
structures. Lithography is a technique used
to transfer patterns onto a substrate.
Interferometric lithography is a process in
which a laser beam is split into two beams,
one going directly to the sample and one
going to mirror and then reflected to the
sample, thereby creating an interference
pattern [8]. The pitch of grating d is
determined by the formula
d =
where is the wavelength of the laser beam,
n is the index of refraction of the medium
(in air, n is 1), and is the angle between
the beam and the surface normal to the
sample. In electron beam lithography (EBL),
a beam of electrons is scanned in a pattern
across a surface with photoresist to create
small structures in the resist that can then be
transferred to the substrate.
EBL is generally used to make integrated
circuits and masks [10, 12]. Although useful
for creating interesting, repetitive patterns,
electron beam lithography cannot be
performed on a large scale because it is
extremely slow and expensive [10].
However, it can be used on a single sample
and then nanoimprint lithography can be
used utilized on a mass scale. Nanoimprint
lithography, as opposed to electron beam
lithography, is relatively simple, fast, and
inexpensive [9]. In addition, it has a high
throughput and resolution [4]. Nanoimprint
lithography (NIL) can be performed in three
different ways, the first called thermal NIL,
the second called ultraviolet NIL, and the
third called substrate conformal imprint
(a)
(b)
Figure 4. (a) [21] In the top right picture, an object is
detected that wouldn’t be seen with the human eye.
(b) [22] In the bottom three pictures, different parts of
a flame can be seen with an infrared detector.
lithography (SCIL) [4]. The general process
for NIL is shown in figure 5. In thermal
NIL, a mold is pressed into a resist on a
substrate at a high temperature, the substrate
and mold are cooled while pressed together,
and the mold is released from the substrate,
leaving a pattern on the substrate [9]. In
ultraviolet NIL, a mold is pressed into a UV
resist on a substrate, the resist is cured by
exposure to UV light, and the mold is
released from the substrate, leaving the
pattern on the substrate [4]. SCIL, developed
by Philips Research and Suss MicroTec, is
an improved version of UV NIL by
providing ways to get even better resolution
and patterning over larger areas [4]. In
addition, SCIL provides a low force and a
low temperature processing condition for
nanoimprint lithography, which is an
advantage for the fabrication of focal plane
arrays [4]. Photolithography, a simpler
method used to transfer a pattern to a
photoresist, would not be beneficial to use in
this case; it is diffraction limited, so it
doesn’t allow feature sizes as small as those
needed for the fabrication of metamaterial
structures that can be obtained using IL and
EBL [14, 15]. We wanted our feature sizes
to be around 250 nm. Our plan was to begin
with interferometric lithography to establish
the fabrication process for a mask and to
pattern simple structures, and then continue
with electron beam lithography to pattern
more complicated metamaterial structures.
Finally, the mask from EBL would be used
as a mold for mask fabrication through
nanoimprint lithography. This will
ultimately help to replace the optical filter
and put it on the chip level, which is desired
since the optical filter can be very expensive
and bulky. Also, the optical filter transmits
light of certain wavelengths and blocks the
rest of it, producing only one color at a time
[13]. By patterning metamaterial structures
on the pixels, the different geometry of the
structures will produce different colors in
the images taken by an infrared detector. As
mentioned before, metamaterial structures
have a higher absorption efficiency, which
will enhance the optical signal to an infrared
detector and produce more electrons, which
will allow the infrared detector to operate at
higher temperatures [5].
Metamaterial structures also have the
potential to create a more narrow spectral
response, which will improve multispectral
imaging [11]. This technology will be
different from other infrared detector
technologies because the mask patterned
with these structures can be used on any
infrared detector, rather than only on
specific infrared detectors.
4. METHOD
We began with a 530 nm thick quartz wafer,
since quartz is stronger than many other
materials. In addition, it is clear, making it
easier for us to see through it for mask
alignment in later steps. Using a dicing saw,
we inscribed 230 nm thick cuts into the
wafer to make it easier to later cleave into
square samples. We deposited about 35 nm
of chrome on the side of the wafer without
the dicing lines using metal evaporation. We
used chrome because it is a strong metal for
Figure 5. [23] Schematic of NIL fabrication
process.
the dry etching process, and the IL process
allows metallic nanostructures to be
transferred easily [6]. Next, we used a
spinner to spin-coat ICON-16 anti-reflection
coating, which prevents reflections from the
quartz wafer, at 2700 RPM, and did a soft
bake at 200°C for 60 seconds. We then spin-
coated SPR-505A photoresist, a material
coated on a surface to create patterns, at
3000 RPM and did a soft bake at 95°C for
60 seconds. At this point, we cleaved the
wafer into separate square samples along the
lines we inscribed with the dicing saw. This
way, we had multiple samples to test for
different exposure times using
interferometric lithography. The laser that
we used had a beam with a wavelength of
355 nm, frequency of 60 Hz, and energy of
75 mJ. The pitch of grating for our samples
was 500 nm. Initially, we exposed a few
samples without rotating the sample in the
sample holder to create one dimensional
lines. We tested exposure times varying
from 5 to 13 seconds, and with each sample
we incremented the time by 2 seconds. After
each exposure, the sample was placed on a
hot plate heated to 110°C for 60 seconds,
and then developed using MF-702 for 60
seconds. The developer removes the
photoresist from the parts of the sample not
exposed by the laser beam and leaves
patterns across the surface of the sample. At
this point we looked at our samples under a
scanning electron microscope (SEM) to see
how the lines looked. Once we found a
sample with solid, unconnected lines, we
used that exposure time to pattern two
dimensional posts on new samples. We once
again took SEM images to examine the
posts. The next step in the fabrication of the
mask was dry etching the ARC, which was
done with a reactive ion etching (RIE)
machine. In this process, gases and plasma
are introduced in a chamber. We used
oxygen gas for the dry etching. We tested a
few different etch times and then looked at
our samples under an SEM to see if we were
successful. Our final recipe for the RIE was
10 mTorr chamber pressure, 10 sccm
oxygen gas, a radiofrequency (RF) power of
15% of 200 W, and an etch time of 1.75
minutes.
The next step in our procedure was to wet
etch the chrome. We used a wet etchant,
called CEP-200, and tested different etch
times—10, 15, and 20 seconds—on a few
samples. After looking at these samples
under an SEM, we determined that the
chrome needed to be etched for at least 20
seconds, because we could still see the
chrome on the wafer with the etch times less
a)
b) c)
d) e)
f) g)
h) i)
j) k)
Figure 6. Visual representation of the interferometric
lithography process. a) quartz substrate, b) chrome
deposition, c) ARC coating, d) photoresist coating, e)
IL, f) developing sample, g) dry etching ARC, h) wet
etching chrome, i) removing ARC and photoresist, j)
dry etching quartz, and k) removing chrome.
than 20 seconds. At this point in our
experiment, we didn’t have enough samples
to test the dry etching of the quartz, so we
repeated the entire process—dicing saw cut
lines, metal deposition, interferometric
lithography, dry etching the ARC, and wet
etching the chrome. Then, we removed the
photoresist and ARC by using another
plasma dry etching machine with oxygen
gas. Since our facility, the Center for High
Technology Materials (CHTM), does not
have the capability to dry etch quartz, we
had to go to the Center for Integrated
Nanotechnologies (CINT) at Sandia
National Laboratories to use their machine
for dry etching. We used a Trion Tech
fluorine dry etching machine with a chamber
pressure of 10 mTorr, ICP radiofrequency of
350 W, RIE radiofrequency of 35 W, 45
sccm CF4, 5 sccm Ar, 5 sccm O2, and an
etch time of 120 seconds. We went back to
CHTM to take some SEM images to see if
the etching worked. After removing the
chrome with the chrome wet etchant and
taking a few more SEMs, we had completed
the process for the fabrication of a mask. A
visual process for the fabrication of a mask
using IL is shown in figure 6. We then
applied this process to the fabrication of a
new mask using electron beam lithography
to pattern more complicated shapes than
posts. We began with a new quartz wafer on
which we spin-coated a photoresist, called
poly methylmethacrylate (PMMA),
specifically for electron beam lithography, at
3000 RPM. Next, we went to CINT to use
their electron beam lithography machine.
This process was quite complicated and took
a few hours to complete, unlike
interferometric lithography, which only
takes a few minutes. We did a direct write to
create the pattern on our substrate. We
developed the sample using MIBK diluted
1:3 for 1 minute. After this, we deposited
around 35 nm chrome using a metal
evaporator and dry etched the quartz at
CINT, using the procedure outlined above.
A few SEM images confirmed that the
patterns were transferred to the quartz.
Although the next step of our project was to
fabricate many masks using the sample from
electron beam lithography as a mold through
nanoimprint lithography, we unfortunately
were not able to access the machines and
materials needed to do so.
5. RESULTS
We were able to successfully make one
dimensional lines and two dimensional posts
using interferometric lithography, as seen in
the SEM images in figure 7. The lines and
posts have a diameter of 250 nm.
After creating the patterns in the photoresist,
we dry etched the ARC to transfer the
pattern to the ARC. We tested a few
different etch times, and even though
different etch times may have successfully
dry etched the ARC, some of the times
reduced the diameter of the posts
significantly. We wanted the posts to still be
similar in diameter to how they were before
the dry etching. We determined that 1.75
minutes was the etch time that correctly
transferred the pattern to the ARC and kept
the diameter of the posts, as shown in figure
8. We knew we had dry etched the ARC
because we could see a slight horizontal line
Figure 7. The sample on the left was exposed for
7 seconds, and the sample on the right was
exposed for 3.5 seconds, and then rotated and
exposed for another 3.5 seconds.
showing the separation between the
photoresist and ARC.
We then wet etched the chrome using
different etch times and took SEM images of
the different samples. After comparing the
images, we believe that 20-30 seconds was
enough time to wet etch the chrome, as seen
below in figure 9.
After wet etching the chrome, we removed
the photoresist and ARC using a plasma RIE
machine with oxygen gas. Then, we went to
CINT to dry etch the quartz. We dry etched
approximately 100 nm per minute. To
determine the etch rate, we took a quartz
substrate that had half of the quartz exposed
and the other half with 35 nm of chrome.
We dry etched the sample for 5 minutes and
measured an etch depth of 0.5 microns using
an alpha-step machine. For our samples, we
dry etched the quartz for 2 minutes and
achieved an etch depth of 200 nm. An
example of this is shown in figure 10. We
wanted close to a 1:1 ratio between the
diameter of the post (250 nm) and the depth
of the post (200 nm).
After using the SEM at CHTM, we went to a
different facility, The Center for Micro-
Engineered Materials, to use their SEM to
obtain different types of images. We took
some secondary electron (SE) images and
some back-scattered electron (BSE) images
to get new information from the images, as
shown in figure 11. SE images show the
topographical contrast in the images, and
BSE images show the contrast in the
material. We performed electron beam
lithography on a sample to pattern a
metamaterial structure. Although we were
able to transfer the pattern to the quartz
Figure 10. Titled view of the substrate after we
dry etched the quartz. There is still chrome on the
posts, but we believe we were able to successfully
etch the quartz.
Figure 9. SEM image of a sample that was wet
etched for 20 seconds to remove the chrome. The
quartz can be seen in between the posts. The
photoresist can be seen on top of the posts (the
darker spots).
Figure 8. Both of these images are SEMs of a
sample after the anti-reflection coating was dry
etched for 1.75 minutes using oxygen gas. The
image on the left is the top view and the image on
the right is the side view of the same sample.
successfully, the patterns did not look
exactly as we intended them to look.
The metamaterial structure that we
attempted to pattern on the substrate is
shown in figure 12. The patterns were
distorted and non-uniform, as seen in figures
13 and 14, but we were not completely sure
why this happened. This may have happened
due to surface charging from the electron
beam lithography machine. We believe
reducing the current and coating the sample
in gold prior to performing EBL would
reduce the charging effects. If we had more
time, we would vary the parameters to try to
perfect the EBL process. This process would
take another two weeks to perfect, since
there are still many unknowns, such as level
of current and amount of gold. Another
reason why the patterns appear to be
disconnected and non-uniform is poor
adhesion of the photoresist. This can be seen
in figure 14, where parts of the cross do not
appear. One way to prevent this is to clean
the substrate thoroughly before applying
photoresist, by baking the substrate for a
long period of time and then cleaning it with
acetone and isopropanol. Although our
results were not perfect, we were still able to
show that it is possible to pattern these
metamaterial structures on a quartz
substrate.
6. CONCLUSION
In this paper, we have outlined the current
infrared detector technologies and the
reasons for continued research in this field.
We discussed the need to increase the
functionality of pixels on an infrared camera
by patterning metamaterial structures
through lithography to enhance the function
of the focal plane arrays and improve the
optical signal to an infrared camera. We
have shown that it is possible to pattern
these structures and that, if produced on a
mass scale using nanoimprint lithography,
they show much promise in ultimately
improving infrared detectors. This
technology is different than the other
technologies mentioned earlier in this paper,
Figure 12. Image of the metamaterial structure
that we patterned on the quartz substrate.
Figure 11. Both pictures are top views of the
substrate after the quartz was dry etched. The top
image is an SE image, and the bottom image is a
BSE image.
since it can be used on any infrared detector;
it is not specific to a certain type of infrared
detector.
As mentioned before, these metamaterial
structures have the potential to improve the
images taken by an infrared camera by
incorporating polarization, dynamic range,
color, and multispectral capabilities in the
images.
7. FUTURE WORK
If we had more time to continue this
research project, we would attempt to
improve the process for electron beam
lithography. We would like to be able to
successfully pattern metamaterial structures
on the quartz substrate. After obtaining the
required materials for nanoimprint
lithography, we will be able to use this
quartz substrate as a mold for NIL to
fabricate masks on a large scale. Then, we
will be able to use the masks from NIL to
print patterns on the focal plane arrays in
infrared detectors. NIL can be used to create
subwavelength grating patterns on the mask
[7]. Currently, EBL can only be
implemented for substrates of small sizes. If
we could perform EBL on a large sample,
then we could fabricate a mask that could be
used for any infrared detector. The final step
in this project would be to actually construct
devices with multi-color and multispectral
capabilities using the metamaterial
structures we fabricated.
8. ACKNOWLEDGEMENTS
I would like to thank the National Science
Foundation and their Research Experience
for Undergraduates program for giving me
the opportunity to perform undergraduate
research. I would like to thank my faculty
mentor, Dr. Sanjay Krishna, and my
graduate student mentor, John Montoya, for
all their help and guidance in my project
throughout these ten weeks. In addition, I
would like to thank some of the other
researchers at CHTM, including Dr. Alex
Raub, for helping me become familiar with
some of the steps in the IL process, Xiang
He, for helping me learn how to use the laser
and for helping with the dry etching process,
Figure 14. 30 degree tilted view of the
metamaterial structure patterned on the quartz
substrate.
Figure 13. Top view of the pattern after dry
etching the quartz. The pattern is non-uniform
and some parts of the crosses are disconnected.
and Ajit Barve, for helping me take many of
the SEM images in this paper. I would also
like to thank CHTM at UNM and Sandia
National Laboratories for allowing me to use
their facilities throughout the summer.
9. References
[1] S. Krishna. The Infrared Retina. J. Phys.
D: Appl. Phys, vol. 42, pp. 1-6, 2009.
[2] A. V. Barve, S. J. Lee, S. K. Noh, and S.
Krishna. Review of current progress in
quantum dot infrared photodetectors. Laser
Photonics Rev. (in press).
[3] Krishna, S., Gunapala, S. D., Bandara, S.
V., Hill, C. & Ting, D. Quantum Dot Based
Infrared Focal Plane Arrays. Proc. IEEE 95,
1838–1852, 2007.
[4] Ji, R.; Hornung, M.; Verschuuren, M. A.;
van de Laar, R.; van Eekelen, J.; Plachetka,
U.; Moeller, M.; Moormann, C. UV
Enhanced Substrate Conformal Imprint
Lithography (UV-SCIL) Technique for
Photonic Crystals Patterning in LED
Manufacturing Microelectron. Eng. 2010,
87, 963-967.
[5] N. I. Landy, S. Sajuyigbe, J. J. Mock, D.
R. Smith, and W. J. Padilla. A Perfect
Metamaterial Absorber. Physical Review
Letters, volume 100, issue 20, pages
207402/1-207402/6, 2008.
[6] K. Du, I. Wathuthanthri, W. Mao, W.
Xu, and C. Choi. Large-area pattern transfer
of metallic nanostructures on glass
substrates via interference lithography.
Nanotech 22:285306, 2011.
[7] Ahn S-W, Lee K-D, Kim J-S, Kim S H,
Lee S H, Park J D and Yoon P W.
Fabrication of subwavelength aluminium
wire grating using nanoimprint lithography
and reactive ion etching. Micro.
Eng. 78/79 314-8, 2005.
[8] L. Gao, L, Lin, J. Hao, Weifeng Wang,
R. Ma, H, Xu, J, Yu, N. Lu, Wenchong
Wang, L. Chi. Fabrication of split-ring
resonators by tilted nanoimprint lithography.
Journal of Colloid and Interface Science,
vol. 360, issue 1, pp. 320-323, 2011.
[9] Tao H, Landy N I, Bingham C M, Zhang
X, Averitt R D and Padilla W J. A
Metamaterial Absorber for the Terahertz
Regime: Design, Fabrication and
Characterization. Opt. Express 75 7181,
2008.
[10] Harriott, Lloyd R. Electron Beam
Lithography. American Physical Society,
APS/AAPT Joint Meeting, April 18-21,
1997, abstract #K7.02.
[11] Lammel G, Schweizer S, Schiesser S,
and Renaud P. Tunable optical filter of
porous silicon as key component for a
MEMS spectrometer. J. Microelectromech.
Syst. 11 815-28, 2002.
[12] Digital Focal-Plane Arrays. Rep.
Lincoln Laboratory (MIT). Web.
[13] S. J. Lee, Z. Ku, A. Barve, J. Montoya,
W. Jang, S. R. J. Brueck, M. Sundaram, A.
Reisinger, S. Krishna, and S. K. Noh. A
monolithically integrated plasmonic infrared
quantum dot camera. Nat. Commun. 2:286
doi: 10.1038/ncomms1283, 2011.
[14] S. R. J. Brueck, Optical and
interferometric lithography—
nanotechnology enablers, Proc. IEEE 93, p.
1704, 2005.
[15] A. Boltasseva and V. M. Shalaev.
Fabrication of optical negative-index
metamaterials: Recent advances and
outlook. Metamaterials2, 1–17, 2008.
[16] S. Krishna. Quantum dots-in-a-well
infrared photodetectors. Journal of Physics
D: Applied Physics, 38, p.p 2147., 2005.
[17] H. C. Liu. Quantum dot infrared
photodetector. Opto-Electron. Rev. 11(1),
2003.
[18] "Infrared Camera Image Gallery."
Infrared Camera and Night Vision
Superstore. Web.
[19] "FLIR Thermography - Infrared
Cameras & Thermal Imagers." FLIR. Web.
[20] Fu, Lan, P. Kuffner, H. Hoe Tan, and
Chennupati Jagadish. "Using Controlled
Interdiffusion to Make a Two-color
Quantum Dot IR Photodetector | SPIE
Newsroom: SPIE." SPIE - the International
Society for Optics and Photonics. SPIE,
2006.
[21] Dereniak, E. Snapshot Polarimetry.
Photograph.
[22] R. Rehm, M. Walther, J. Schmitz, J.
Fleibner, J. Ziegler, W. Cabanski and R.
Breiter. Dual colour thermal imaging with
InAs/GaSb superlattice in mid-wavelength
infrared spectral range. Elec. Lett., 42(10),
2006.
[23] "Nano Imprint Lithography: A Giant
Leap for Miniature Manufacturing - News -
NRC-CNRC." National Research Council
Canada: From Discovery to Innovation /
Conseil National De Recherches Canada :
De La Découverte à L'innovation. National
Research Council Canada, 05 Aug. 2005.
top related