![Page 1: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/1.jpg)
Spectroscopy and capacitance t f t limeasurements of tunneling
resonances in an Sb-implanted ppoint contact
Nathan Bishop,Sandia National Laboratories
Funded by the Laboratory Directed Research and Development program.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National
Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2010-5581C
![Page 2: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/2.jpg)
Outline• Our design and relation to previous work
Silicon MOS q ant m dots as sensiti e• Silicon MOS quantum dots as sensitive charge sensors
• Donor transport device structure• Comparison between experiment and
capacitive model• Future work – excited state spectroscopyFuture work excited state spectroscopy
and charge sensing• Conclusion• Conclusion
![Page 3: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/3.jpg)
Some previous workTan et al., Nano Lett. 2010
Morello et al., arxiv 2010
![Page 4: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/4.jpg)
Si MOS quantum dots as charge sensorscharge sensors
560400
(Nordberg)
480
520
300
nt (p
A)
curr
ent (
pA)(Nordberg)
400
440
100
200
Dot
cur
ren
oint
con
tact
c
400μV SD
-0.3 -0.2 -0.1 0.0 0.1 0.2360 0
Point contact gate voltage (V)
Po400μV SD
1mV SD
• Reverse normal usage: use a quantum dot to sense changes in a point contact.
• Can be used to sense the spin state of a donor embedded in the point contact.
![Page 5: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/5.jpg)
Si MOS process flowp• Oxide growth• Polysilicon deposition
and patterningOh i t t i l t• Ohmic contact implant and anneal
• Nitride and pre-metal dielectric dep.Sili id d lli i• Silicide and metallization
• E-beam litho and polysilicon patterning
• More EBL and Sb implantation
• Strip metal and re-oxidize polysilicon
• Second dielectric (ALD Al2O3) dep.Al2O3) dep.
• Final metallization
![Page 6: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/6.jpg)
Control sample: Silicon implantp pNo implant
40 keV silicon implant4 x 1011 cm-2 dose
V d
c)
V d
c)X X
bias
(mV
bias
(mVS D
rce-
drai
n
rce-
drai
n
S D
Sou
r
Sou
rS D
Depletion gate voltage (V)Depletion gate voltage (V)
![Page 7: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/7.jpg)
Control vs. implanted_
150nmHAntimony allows
high temperaturepost implant
Sample type Qfb(q/cm2)
Dit(q/cm2eV)
Normal process + 5 x 1010 1 x 1010
Not implantedA G
post-implantprocessing.
100 keV antimony
p
Silicon implant + RTA (Donor device equivalent dose) + 3 x 1011 2 x 1011
Silicon implant + reoxidation + 1 x 1011 1 x 1010
100
2
10-1
Not implanted
BC D E
F
y4 x 1011 cm-2 dose
Silicon implant + reoxidation + 1 x 10 1 x 10
10-2
10-1
ance
(e2 /
h)
10-3
10-2
ance
(e2 /
h)
C D E
10-3
10C
ondu
cta
10-5
10-4
Con
duct
a
-0.8 -0.6 -0.4 -0.2 0.010-4
Depletion gate bias (V)
-0.30 -0.24 -0.18 -0.12 -0.06 0.0010 5
Depletion gate bias (V) T ~ 250mKVsd = 0.5 mVrms
![Page 8: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/8.jpg)
Tunneling spectroscopy-0.30 -0.28 -0.26 -0.24 -0.22 -0.20
Depletion gate bias (V)
dI / dV(S)
H10
52 1E 07
1.0E-06
ias
(mV
) (S)
A G
0
-54.5E-08
2.1E-07
ce d
rain
bi
BC D E
F5
-10
2.0E-09
9.5E-09
Sou
rc
10-2
10-1
/ h)
C D E
Vsd = 50 Vrms 2.0E 09
10-4
10-3
ondu
ctan
ce (e
2
Relevant features:1. Aliasing – nearby charge environment2. Excited states – structure of donors / dots
-0.30 -0.24 -0.18 -0.12 -0.06 0.0010-5
Co
Depletion gate bias (V)
2. Excited states structure of donors / dots3. Slope of lines – capacitance
![Page 9: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/9.jpg)
Capacitive model
Aluminum gate
Si
2DEG
Oxide
SiO2
Polysilicon
2DEG
Al2O3
Harold Stalford, Ralph Young
![Page 10: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/10.jpg)
0.035 Experiment (A or B)
Triangulation of Resonances
0 025
0.030
R=15 nm
R=12.5 nm
Experiment (A or B)Simulated dots (R = 12.5, 15, 18 nm)Simulated donors (depths = 5, 10, 20 nm)
Only dots?
2DEGImplant window
0.020
0.025
1815
R=28 nm
5 to 20 nm donor depth
Top/C
Tota
l Only donors?
Donor atom
0.010
0.015donor depth
40 nm barrier
CT
60 nm barrier
2DEG
0.3 0.4 0.5 0.6 0.70.005
30 nm barrier
CWire+QPC/CS or D H. StalfordP iti d i d t i tiPosition and size determination1. Capacitance ratios are sensitive to small differences
in geometry2. Top gate, S/D and lateral gates cover all three spatial p g , g p
directions- Is resonance below the surface?- Still in progress
![Page 11: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/11.jpg)
Spectroscopy: Sb in SiDeeply buried donor Donor near interface
Ene
rgy
nerg
yRajib Rahman oxide silicon
Position
En
Position
![Page 12: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/12.jpg)
Spectroscopy: excited states9
66
3
mV
)
0
0
C b
ias
(m
Bg B-3 D
C
-6
-9
Bg B21
9-0.22-0.24-0.26-0.28
Depletion gate bias (V)
![Page 13: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/13.jpg)
Conclusions• Fabricated unique device which enables a
id i t f ibl i twide variety of possible experiments.• Identified tunneling resonances in
implanted point contacts, which are rare in clean controls.
• Capacitive measurements locate the resonant states in the point contact, and p ,are consistent with donors as the source.
• Charge sensing measurements ongoingCharge sensing measurements ongoing.
![Page 14: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/14.jpg)
AcknowledgementsQuantum Team:Ed BielejecMalcolm Carroll
Quantum team cont’d:Denise TibbettsLisa Tracy
Kent ChildsKevin EngRobert GrubbsPaul Hines
yJoel WendtWayne WitzelRalph Young
Paul HinesMike LillyJoel MeansRick Muller
Australian collaborators:
Susan AngusEric NordbergTammy PluymRajib RahmanBev Silva
Andrew DzurakWilliam LeeAndrea MorelloMichelle SimmonsBev Silva
Harold StalfordJeff StevensTom Tarman
Michelle SimmonsDan Tomlinson
Greg Ten Eyck
![Page 15: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/15.jpg)
Extracting capacitance-0.20-0.22-0.24-0.26-0.28-0.30
5
Depletion gate bias (V)
4
3
as (m
V)
2
1
rce
drai
n bi
a
0
-1
Sou
r
B A
B peak slopes:-0.2810 417
A peak slopes:-0.2490 277Vsd 0.417 0.277
S D
Vsd
![Page 16: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/16.jpg)
Donor distribution1E21 150 keV Sb implant
SIMS, 121Sb SIMS, 123Sb
1E20 SRIM, 150 keV
n (c
m-3)
1E18
1E19
entra
tion
1E17
1E18
b co
nce
0 300 600 900 1200 15001E16
S
oxide
0 300 600 900 1200 1500
Depth (Å)SIMS by Tony Ohlhausen, SNL
![Page 17: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/17.jpg)
Ion implantation
• E-beam litho and polysilicon patterningSb+
Back end
E beam litho and polysilicon patterning• More EBL and ion implantation• Strip metal and re-oxidize polysilicon• Second dielectric (ALD Al2O3) dep.
i l lli i• Final metallization
![Page 18: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/18.jpg)
Lever arm analysis
measuredBBMAX TkVV
TkE
GG
2cosh
402
eC3.0x10-3 TMC = 19 mK
VSD = 15 Vrms
(e /
h) ModelQuantumlimit (User)
Equationy = A + B * (cosh((x - xc)/ (2*C))) (̂-2)
Reduced Chi-Sqr
2.04899E-9
CeCG
2.0x10-3
ucta
nce
(
Adj. R-Square 0.99476Value Standard Error
West QPC cond A -2.78813E-5 3.98619E-6West QPC cond B 0.00325 2.50309E-5West QPC cond C 0.00227 2.17905E-5West QPC cond xc -0.4295 3.17039E-5
1.0x10-3
nel c
ondu
VTk measuredB
2
-0.50 -0.45 -0.40 -0.350.0
Tunn
0.50 0.45 0.40 0.35
Depletion gate bias (V)Kouwenhoven et al., Electron transport in quantum dots, NATO ASI 1997
![Page 19: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/19.jpg)
Lever arm analysis
A peak ( = 0.0167)
0.8
1.0
ure
(K)
A peak ( 0.0167) B peak ( = 0.0111) Perfect scaling Vds limit = 0.174 K
0.6
mpe
ratu
0.4
sure
d te
m
0.0
0.2
Mea
s
0.0 0.2 0.4 0.6 0.8 1.0
Mixing chamber thermometer (K)
![Page 20: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/20.jpg)
Poor scaling due to high Vdsds
1.8
1 2
1.5
re (K
)
0.9
1.2
mpe
ratu
0.6
aled
tem
A peak ( = 0.165)
0.0
0.3Sca B peak ( = 0.135)
Perfect scaling Vsd limit = 1.16K
0.0 0.2 0.4 0.6 0.8 1.0Mixing chamber thermometer (K)
![Page 21: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/21.jpg)
Top gate lever arm
1.2x10-7
S)A
6.0x10-8
9.0x10-8
ucta
nce
(S
A slope:dVPoly / dVTG = -0.639
B l
0 0
3.0x10-8
6.0x10
Con
d
B
B slope:dVPoly / dVTG = -0.625
H0.0
18.0
18 7 A G
H
-1.5 -1.2 -0.9 -0.6 -0.3Depletion gate bias (V)
18.7 A
B
G
FC D E
![Page 22: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/22.jpg)
Top gate lever arm
Depletion gate bias (V)-1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4
18.0
18 1B A
A and B have nearlyidentical top gate lever
18.1
18.2
(V)
arm.There is a disorder dotthat does have a largerlever arm.
18.3
18.4ate
bias
Disorder dot!
18.5
18 6 Top
ga
18.6
18.7
![Page 23: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/23.jpg)
Ion implant damage45 keV silicon implant, equivalent to 100 keV antimony implant
900 C furnace anneal, 24 minutes in O2
![Page 24: Spectroscopy and capacitance measurementft lits of ... and capacitance measurementft lits of tunneling resonances in an Sb-implanted point contact Nathan Bishop, Sandia National Laboratories](https://reader038.vdocuments.site/reader038/viewer/2022110112/5b0365137f8b9a2d518c1b83/html5/thumbnails/24.jpg)
Threshold difference
10-4 Leads Control Implanted
10-5
e (S
)
_150nm H
10-7
10-6
nduc
tanc
e
A G
10-8
10 7C
on
BC D E
F
0 3 6 9 12 15 18Accumulation gate bias (V)
C D E
Implant damage increases interface trap density and fixed charge, butp g p y gmostly repaired after high temperature processing.
CV measurements of Dit and Qf by Greg Ten Eyck