Reference
TBTDEN
1. Background
Development of NbN films by atomic layer deposition for
Superconducting Tunnel Junction particle detectors with a high
operating temperatureM. Ukibe, and Go Fujii
National Institute of Advanced Industrial Science and
Technology, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568, JAPAN
Nanoelectronics Research Center
A) Understanding the evolution of molecules in spaceneed to
evaluate quantitatively dissociationbranching ratios and the yields
of neutral products indissociative electron-ion recombination
(DR)processes.
The combination of a solid-state kinetic-energy-sensitive
superconductingtunnel junction (STJ) particle detector and tandem
mass spectrometers (MS) ora compact electrostatic storage
rings.[2][3]
[2] M. Ohkubo, et al., IJMS 299, 94 (2011), doi:
10.1016/j.ijms.2010.09.027
B) The powerful analytical instrument of the DR processes
fabricated at AISTMS/KEMS instrument, AIST, Tsukuba
Lab-based MS/MS
[3] T. Tanabe, et. al., Dissociative Recombination of Molecular
Ions with Electrons, p.p. 75-85(2003)
[1] Scott Sandford, et. al., The Astronomy and Astrophysics
Decadal Survey, Science White Papers,257(2009)
[1]
Solid state kinetic-energy-sensitive
Nb/Al STJ detector Electrostatic Storage Ring
or
MS instruments
+
2. Difficulties of the STJ operation in MSA) An appropriate
operation temperature of Nb/Al STJs : 0.3 K
IR shield
Particles can pass through holes in IR shield
B) Large thermal inflows from room temperature to STJs for a
high throughputA large number of wirings (>100) for obtaining a
large detection areaInsufficient thermal filter setup for the
particles sources
It is necessary for particles to pass IR shieldsC) STJ detectors
with high operation temperature > 1 K
Operation temperature < Transition temperature (TC ) / 10NbN
(TC : 17.8 K for 100 nm[4] ) is appropriate
[4] A. Shoji, IEEE Tran. Mag. 27, p.p. 3184(1991)
D) NbN/AlN/NbN STJ (NbN-STJ)Nice lattice matching : NbN(0.439 nm
(a-axis)) and AlN (0.498 nm (c-axis))
Full nitride multilayerAlN thickness should be controlled
between 1.4 and 1.6 nm in order to realize a JC value between 100
and 1000 A/cm2[5]
[5] Z. Wang, et. Al., Appl. Phys. Lett., 75, p.p. 701(1999)
Full epitaxial multilayerGood tunnel barrier
E) Atomic layer deposition (ALD) is best for the deposition of
NbN-STJsNbN films deposited by an ALD tended to exhibit a low TC of
about 10 K [6].
3. Experiments
[6] Mario Ziegler et.al., Supercond. Sci. Technol. 26, 025008
(2013)
• Source (precursors) of NbN : TBTDEN [C16H39N4Nb]• Substrate :
M-plain sapphire wafer• ALD : Ultratech Fiji 200 G2 • Substrate
temperature(Tsub) : 570 K• Film thickness (tNbN) : 50 nm•
Dissociation of TBTDEN : N2 plasma
[7]
http://www.longsun.asia/uploadfile/upload/2015072113420828.pdf
Ultratech Fiji 200 G2 [7]
A) Deposition condition
We have tried improving the superconducting properties of ALD
NbNfilms by a post-deposition RTP to realize a high TC about 17
K.
B) Anneal condition• Annealer : ANNEALSYS AS-One 100• Process
gas : N2 at of 1 atm• Anneal temperature : 770, 870, 970, 1050,
1120 K• Temperature ramp rate : 50 K/sec • Anneal time : 20 ~ 2000
sec
AS-One 100
C) Evaluation of film characteristics(i) X-ray diffraction •
Diffractometer :Rigaku Ultima X Multipurpose X-ray diffraction
system• Measurement : Grazing incident(0.6 degree), θ-2θ, In-plane,
φ-scan, Pole figure (ii) Surface morphology• SPM : Shimadzu
SFT-4500 scanning probe microscope• Scan area : 500 x 500 nm(iii)
R-T curve• Pattern size : A line patter of 50 µm width and 1 mm
long• Cryostat : 4K GM
4. Results
X-ray diffraction pattern(GI) of a NbN film annealedat 870 K,
200 sec.
A) Crystal structure• ALD NbN film on M-plain sapphire wafer :
110 orientation• After the anneal process at 970 K, a part of the
cubic NbN transformed into
tetragonal NbN.• Crystallite size : ALD film(9-11 nm) <
Sputter film (14-16 nm)• Best crystallinity so far at 870 K, 200
sec
Pole figure of a NbN film annealed at 770 K, 2000 sec. Itshows
that the NbN film has 110 orientation.
B) Surface morphology• The surface of the NbN film became rough
by the anneal.• With increasing the anneal temperature, the root
mean square roughness (Sq)
was considerably enlarged but wasn’t larger than that of the
sputter film.• The grain size of the NbN in the ALD film increased
by the anneal too.
C) R-T curves• The TC of the ALD NbN film was 12.35 K,
higher than that of the previous data [6]and was increased to
13.37K by theanneal of 770K, 2000 sec.
• The RRR values of the ALD NbN filmswere smaller than that of
the sputter film.
5. Conclusion• We succeeded in depositing a 50 nm - thick NbN
film on M-plain sapphire with
relatively high TC of 12.35 K.• The anneal certainly changed the
crystal structure conditions of the ALD NbN
films and the TC was improved up to 13.37 K.• It is considered
that the enlargement of the grain size of the NbN by the anneal
process was occurred by an agglutination of many NbN
crystallites, not by thecrystal growth of each NbN crystallite.
• It is necessary to perform the further investigation in order
to decide theoptimal anneal condition of the ALD NbN films.
This work was supported by JSPS KAKENHI Grant Number 15H03599. A
part of this work was conducted at the AIST Nano-Processing
Facility.
AcknowledgmentThe authors thank H. Yamamori and S. Shiki for
their help with the experiments, and the clean room members of
analog-digital superconductivity (CRAVITY) forperforming
experiments.
6-16am-Poster-2
Pea
k inte
nsi
ty (
cps)
δ-N
bN(1
11)
δ-N
bN(2
00)
δ-N
bN(2
20)
β-N
b2N(1
03)
δ-N
bN(3
11)
δ-N
bN(2
22)
δ-N
bN(4
00)
γ-N
bN(1
10)101 011
110
1-10 -110
10-1 01-1
別2
別1別1
別2
別2別2
別3
別3 別3
別3
0.00E+00
5.00E+02
1.00E+03
1.50E+03
2.00E+03
2.50E+03
3.00E+03
13.00 13.20 13.40 13.60 13.80 14.00
Resi
stiv
ity
(ohm
)
Temperature (K)
Development of NbN films by atomic layer deposition for
Superconducting Tunnel Junction particle detectors with a high
operating temperature�M. Ukibe, and Go Fujii�National Institute of
Advanced Industrial Science and Technology, 1-1-1, Umezono,
Tsukuba, Ibaraki, 305-8568, JAPAN
