200 nm

Time (ns)

epi-YSZ is deposited by PLD

2 m

NbN

NbNOx

Oxide

5m

Same 6.6 nm NbN sample as for XRD

Further improvements and developments:

Optimization of ultra-thin NbN (and other nitrides or cuprates) superconducting films on large wafers and of patterned devices adapted to Hot Electron Bolometer SSPD.Development of new integrated digital applications of NbN and nitrides devices integrated with NbN RSFQ circuits on silicon wafers (see talk 3EA04)

Fabrication and characterization of superconducting NbN epitaxial ultrathin layers and nanowires
R. Espiau de Lamaestre1, E. Bellet-Amalric1, R. Setzu1,J-C. Villgier1,

J. Claudon2,1, J-Ph. Poizat2,1, C. Delacour2,V. Bouchiat2, L. Mchin3,P. Moretti4,

1 CEA-Grenoble (France), 2 CNRS-Grenoble (France), 3 ENSI-Caen (France) , 4 UCB-Lyon (France)

Perspectives

Epitaxial superconducting film deposition conditions

Typical DC-magnetron sputtering conditions and characterization of a 3 to 100 nm film epitaxially grown on R-plane sapphire or MgO

2MM02

Structuration of NbN layers for photon detection

Applied Superconductivity Conference 2006

D(T), normalized conductance (2 (0) = 4.3 meV) using LT-STM and Jc (T) characterisations and surface imaging (2x2 m2) showing a good uniformity and small roughness in a 3.4 nm thick NbN on 3inch R-plane sapphire.

NbN (100)

Epitaxial growth of 4 nm NbN on Si (100) using either an ultrathin TaNx (~1 nm) silicide or an YSZ buffer layer

Reciprocal space section in both plane chosen for this study. Epitaxial relation:

Experimental limits are materialized by light (wavelength) and dark (plane opaque sample) grey.

Example of Mo2N cubic nitride thin film (~10 nm thick) epitaxially grown of on R-plane Sapphire

HR-TEM cross-section image of an ultrathin NbN film grown at 600C on R-plane sapphire

M.Faucher et al. Physica C, 368, 211, (2002)

NbN (3.4 nm thick) nano-bridges patterned by e-Beam lithography

Characterization of 3-7 nm epi-NbN films on R-plane sapphire and on Si (100)

6.6nm epi-NbN on R-sapphire. Reciprocal space map (units: 2/) around the awaited position (Qx=-3.05; Qz=4.82, green circle) of the 004 diffraction peak of NbN.

=-40.2

100nm NbN line spaced by 100nm. E beam litho,PMMA

Very thin (2.5-10nm thick) epi-NbN superconducting layers with large Tc and large Jc are grown by dc-magnetron sputtering in a controlable way on heated 3' and 4' R-plane Sapphire, YSZ or silicide buffered silicon (100) and MgO (100). Very thin (~1nm) AlN overlayer are insuring storage without degradation. (135) NbN growth on top of R-plane Sapphire at 600C is directly observed by XRD for very thin layers.

E-beam lithography or AFM tip anodization are used for patterning robust NbN nanowires less than 100nm width & meander SSPD. Stability of NbN layers under proton irradiation allows the realization of buried optical wave-guide under NbN stripes. Such NbN nanolayers and SSPD integrated devices are applied to photon detection, THz mixers and fast RSFQ circuit interfaces.

AFM lithography limited by the tip radius ~30nm

Narrow and dense (80% surface)

Observation of SSPD single photon @~1m time response of the NbN (3.4 nm thick)

NbN 3.4 nm strips before and after proton irradiation: 1 MeV/1.75.1016 ions/cm2 + 0.95 MeV/1.75.1016 ions/cm2

0

2000

4000

6000

8000

10000

12000

0,5

1,0

1,5

2,0

Gap (mV)

Temperature (mK)

0

2

4

6

8

10

12

14

16

18

20

0

2

4

6

8

10

12

14

Mo

2

N / R-AL

2

O

3

A-1162

R

square300K

= 32

W

R (

W

)

T (K)

0

1

2

3

4

5

6

7

8

9

10

11

12

0

50

100

150

200

250

R(

W

)

T (K)

NbN (4 nm) /buffer/Si (100)

ref. A-2032

0

5

10

15

20

25

30

0

20

40

60

80

100

Resistance

(

W

)

Temperature (K)

NbN(3nm)/YSZ(130nm)/Si

A-2090 - R(T)

NbN/MgO

NbN/Al2O3NbNMo2N

Ar/N2 pressure (Pa)1.81.81,7/0,21,7/0,2

Target power (W/cm2)10.610.411.411.4

Deposition rate (nm/s)4.55.566

Substrate Temp (C)600600600600

Tc (K) 9.24.616.5 > 7

Resistivity at 10K~ 0.3 ~ 0.3 ~ 80 ~ 20

0

1

2

3

4

5

6

7

8

9

10

11

12

0,1

1

Critical current I

C

(mA)

Temperature (K)

NbN (3.4 nm)/R-Sapphire (A1179)

-3.4

-3.3

-3.2

-3.1

-3

-2.9

-2.8

-2.7

Qx

4

.

5

4

.

6

4

.

7

4

.

8

4

.

9

5

5

.

1

Q

z

0.25

0.5

1

1.5

2

2.5

3

4

5

6

7

8

9

10

11

{

}

(

)

[

]

3

2

1

1

10

012

1

1

21

135

O

Al

NbN

8

10

12

14

16

18

20

1E-5

1E-4

1E-3

0,01

0,1

1

10

100

RRR=0.76

T

c

=12.74K

D

T

c

=0.9K

A2040

T (K)

R (Ohms)

0,0E+00

5,0E+02

1,0E+03

1,5E+03

2,0E+03

2,5E+03

0100200300

T (K)

R (Ohms)

irradiated

non irradiated

0,0E+00

5,0E+02

1,0E+03

1,5E+03

2,0E+03

2,5E+03

3,0E+03

12,5013,0013,50

T (K)

R (Ohms)