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RESEARCH ARTICLE
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JULY 05 2023
Lateral nanoscale field emission comb for frequency mixing
L. B. De Rose
;
W. M. Jones
;
A. Scherer
Appl. Phys. Lett.
123, 013505 (2023)
https://doi.org/10.1063/5.0150034
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Lateral nanoscale field emission comb
for frequency mixing
Cite as: Appl. Phys. Lett.
123
, 013505 (2023);
doi: 10.1063/5.0150034
Submitted: 10 March 2023
.
Accepted: 25 May 2023
.
Published Online: 5 July 2023
L. B.
De Rose,
1,a)
W. M.
Jones,
2,b)
and A.
Scherer
1
AFFILIATIONS
1
Department of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA
2
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
a)
Author to whom correspondence should be addressed:
lderose@caltech.edu
b)
Present address:
AWS Center for Quantum Computing, Pasadena, California 91125, USA.
ABSTRACT
Nanoscale field emission devices are promising candidates to design high-frequency electronics due to the lack of scattering in the vacuum
channel that enables ballistic transport. In-plane devices are relatively easy to fabricate with current fabrication techniques and offer sub-fF
capacitance. In this work, the characteristics of lateral gold multi-tip field emission arrays are studied. Vacuum gaps between the electrodes
of 30 nm are fabricated, which allow
<
10 V operation. The effect of number of emitting tips on measured current is investigated. By taking
advantage of the strong non-linearity in the emission characteristic, frequency mixing in the MHz range is also demonstrated.
V
C
2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (
http://
creativecommons.org/licenses/by/4.0/
)
.
https://doi.org/10.1063/5.0150034
Field emission devices have been widely used for various applica-
tions, including as sources in electron microscopes and high-
resolution electron beam lithography,
1,2
microwave power amplifiers,
3
flat panel displays,
4
x-ray sources,
5
pressure gauges,
6
and free-electron
lasers.
7,8
Field emission-based technology is an attractive choice for
designing electronic devices due to several reasons. First, vacuum devi-
ces are inherently resilient to extreme temperatures and radiation.
9,10
Continuous proper operation in harsh environments is crucial for
applications in the automotive, nuclear, down-hole, and aerospace
industries.
11,12
Moreover, unlike thermionic emission, field emission
does not require heating, thus reducing power consumption and elimi-
nating the need for thermal management. In addition, nanoscale vac-
uum gaps can be manufactured using either a top-down approach
with current nanofabrication techniques and high-resolution electron
lithography
13
or via a bottom-up approach using nanostructured
materials such as nanocrystals, 2D materials, nanowires, and nano-
tubes.
14–18
This allows for operation at low voltages,
19
which is advan-
tageous in terms of energy efficiency, Joule heating reduction, and
minimizing the effects of ion sputtering that can result in device
destruction.
Furthermore, field emission devices are promising candidates for
high-frequency electronics due to their intrinsic superiority of vacuum
as a transport medium that enables ballistic electron transport. In
semiconductors, carriers suffer from acoustic and optical phonon
scattering, which limits the maximum velocity a charge carrier can
attain.ThesaturationvelocityforSiisontheorderof1

10
7
cm/s,
and for gallium arsenide, it is 1
:
2

10
7
cm/s, while the velocity of an
electron in vacuum is theoretically about 3

10
10
cm/s.
20
Thus, by
fabricating the smallest nanoscale vacuum channels to shorten the
electron transit time, field emission devices that operate at gigahertz
frequencies or higher could be envisioned.
21
However, even though
there have been multiple attempts to fabricate field emission devices
for high-frequency operation, most of them have employed traditional
Spindt-type vertical field emitter arrays, which have a large overlap-
ping area between the gate and base electrodes. As a result of their
high capacitance, their maximum frequency of operation has been
limited to a few gigahertz.
22,23
In this study, we propose to develop lateral symmetric field emis-
sion devices to minimize the overlapping area between the electrodes
and, thus, reduce the capacitance compared to vertical geometries.
Gold is selected as the electrode material due to its chemical unreactiv-
ity, ensuring that the value of the work function does not vary and
affect emission stability, its high thermal and electrical conductivity,
and the fact that liftoff is relatively easy and results in clean edges and
reproducible fabrication. We will manufacture devices with many
electron-emitting tips to source higher currents and to achieve stable
emission, as the use of multiple tips should decrease flicker noise
by ensemble averaging.
24
By taking advantage of the non-linear
Appl. Phys. Lett.
123
, 013505 (2023); doi: 10.1063/5.0150034
123
, 013505-1
V
C
Author(s) 2023
Applied Physics Letters
ARTICLE
pubs.aip.org/aip/apl
27 October 2023 21:58:06