The document discusses advanced terahertz (THz) technologies and their applications in materials characterization, particularly under extreme conditions such as variable temperatures and high magnetic fields. It highlights the design and capabilities of a THz system by Lake Shore Cryotronics, Inc., which includes features like continuous tuning, high spectral resolution, and integration with cryogenic systems. The document also showcases case studies on material research, including the characterization of thin films and their potential applications.

1. Proprietary | Lake Shore Cryotronics, Inc.
Terahertz Materials Characterization
in Extreme Environments
Emerging Tools for Materials Research
David R. Daughton
Applications Scientist

2. Proprietary | Lake Shore Cryotronics, Inc.
THz Systems
Probe Stations
Hall Effect
Measurement
Systems (HMS)
Magnetometers
(VSM/AGM)
Permanent Magnets
High Density Recording Media
Mineral Magnetism
Electronic thin films
Organic Electronics
Spintronics
Nanowires
Magnetoresistance
Organic electronics
Thermoelectrics
Solar Cells
HEMTS
Materials Characterization Systems
2
Systems
Measure electrical
properties of devices and
materials in temperature-
controlled environment
AC/DC measurements:
 Hall mobilities
 Carrier concentration
 Carrier type
Measure magnetic properties:
 Hysteresis M(H) loops
 FORC curves
 Temperature dependencies
Fully integrated for material properties:
 Electronic
 Magnetic
 Chemical

3. Proprietary | Lake Shore Cryotronics, Inc.
Why THz?
3

4. Proprietary | Lake Shore Cryotronics, Inc.
Equivalent Scales for THz
5
1012 Hz
2.5 THz ~ 10 meV
 Alignment of THz energy levels
with phenomena of interest
– Vibrational resonances
– Novel spin resonances
– Free carrier motion in
semiconductors

5. Proprietary | Lake Shore Cryotronics, Inc.
Materials Phenomena
6
The Electromagnetic Spectrum
D. N. Basov, et al.
“Electrodynamics of correlated electron materials”
Rev. Mod. Phys. 85(2), 471 (2011).

6. Proprietary | Lake Shore Cryotronics, Inc.
Equivalent Scales for THz
 THz wavelengths match the feature
sizes of development-grade
electronic materials
– Non-contact electronic characterization
– Novel magnetic materials
7
1012 Hz
0.6 THz ~ 0.5 mm
2”
10 mm

7. Proprietary | Lake Shore Cryotronics, Inc.
Equivalent Scales for THz
 Coupling to spin-based
materials at THz frequencies
– High speed computing
paradigms
– May require large fields
8
1012 Hz
0.2 THz ~7 T
Nagashima, T.; Nishitani, J.; Kozuki, Kohei, "Lasers & Electro Optics & The Pacific
Rim Conference on Lasers and Electro-Optics, 2009. CLEO/PACIFIC RIM '09.
Conference on , vol., no., pp.1,2, 30-3 Aug. 2009

8. Proprietary | Lake Shore Cryotronics, Inc.
Equivalent Scales for THz
9
1012 Hz
6.5 THz ~ 300 K
480 500 520 540 560 580
0.1
1
THzTransmission
Frequency (GHz)
5.8 K
75 K
150 K
a-Lactose
THzTransmission
 Cryogenic temperatures
– Homogeneous broadening of
vibrational resonances

9. Proprietary | Lake Shore Cryotronics, Inc.
Equivalent Scales for THz
10
1012 Hz
 Cryogenic temperatures
– Homogeneous broadening of
vibrational resonances
– Temperature dependent carrier
concentration and mobility
6.5 THz ~ 300 K

10. Proprietary | Lake Shore Cryotronics, Inc.
Equivalent Scales for THz
11
1012 Hz
10 meV7 T 300 K0.5 mm
 Alignment of THz energy levels with phenomena of interest
 THz wavelengths match the feature sizes of development-
grade electronic materials
 Coupling to spin-based materials at THz frequencies
 Cryogenic temperatures

11. Proprietary | Lake Shore Cryotronics, Inc.
THz System Product Challenges
 THz performance suitable for materials characterization
– Continuous tuning over bandwidth
– Spectral resolution
 Ability to characterize samples while exposed to variable
cryogenic temperatures and magnetic fields
 Affordable THz-based measurement platform
 Robust design
 Proceduralized experimental methods and reliable
analysis of the spectral results
– Convenient sample insertion without complicated alignment
– Enable materials developers to rapidly begin productive research
12

12. Proprietary | Lake Shore Cryotronics, Inc.
Filling the THz Gap
13
The Electromagnetic Spectrum
0 10 20 30 40 50
0
ElectricField(a.u.)
Time (ps)

13. Proprietary | Lake Shore Cryotronics, Inc.
THz with cryogenics & magnetics
14
 Many materials of interest for THz
require variable temperature
and/or high magnetic fields
 Optical cryostats are the standard
approach
– THz generation outside the
environment
– Must pass optical energy through
windows, cutting signal power and
spectral distortion
 Not ideal for THz spectroscopies

14. Proprietary | Lake Shore Cryotronics, Inc.
Variable Temperature and
High Magnetic Field THz Platform
15
Cryostat Sample space
±9 T magnet
Removable
sample insert
Cryo-compatible
THz emitter with
collimating optics
Rotatable
sample stage
(10 mm × 10 mm)
Thermally stable
optical
alignment stages

15. Proprietary | Lake Shore Cryotronics, Inc.
Application software
for turnkey operation
 Experiment setup/run
 Analysis of spectral data
 Calculation of material properties
Integrated THz System Details
16
Fiber-based optical
platform for CW THz
spectroscopy
 CW THz spectrometer instrument
 Amplitude and phase detection from
200 GHz to 1.5 THz
 Spectral resolution under 500 MHz
 Circularly polarized light
Integrated controls
 Model 336 cryogenic
temperature controller
 Model 625 superconducting
magnet power supply
Superconducting magnet
 High magnetic fields to ±9 Tesla
Integrated cryostat & insert
 Variable temperatures from 5 K to 300 K
 Sample size – 10 mm
 Measurement – THz transmission

16. Proprietary | Lake Shore Cryotronics, Inc.
Photoconductive THz Emitter
17
Photoconductive
device
-10 -5 0 5 10
-40
-20
0
20
40
Current(A)
Bias (V)
Dark
Fiber illuminated device
Room Temperature

17. Proprietary | Lake Shore Cryotronics, Inc.
Photoconductive THz Emitter
18
 THz-frequency transient current
oscillations induced by amplitude
modulated IR laser light
 Current oscillations in the antenna
structure radiate propagating EM
waves.
 A high resistivity Si lens is attached
to the emitter device to couple the
THz emission to free space.
Photoconductive
device

18. Proprietary | Lake Shore Cryotronics, Inc.
THz Time Domain Spectroscopy
19
fs
I

19. Proprietary | Lake Shore Cryotronics, Inc.
THz Time Domain Spectroscopy
20
fs
IA
0 10 20 30 40
0
ElectricField(a.u.)
Time (ps)
E

20. Proprietary | Lake Shore Cryotronics, Inc.
THz Time Domain Spectroscopy
21
ps
fs
Dispersion

21. Proprietary | Lake Shore Cryotronics, Inc.
THz Time Domain Spectroscopy
22
Dispersion
Compensation
fs

22. Proprietary | Lake Shore Cryotronics, Inc.
THz Time Domain Spectroscopy
23
Dispersion
Compensation
ps

23. Proprietary | Lake Shore Cryotronics, Inc.
Continuous-Wave THz Spectroscopy
24
DFB Laser 1
DFB Laser 2
f1
f2

24. Proprietary | Lake Shore Cryotronics, Inc.
Continuous-Wave THz Spectroscopy
- Generation
25
f1-f2
f1-f2

25. Proprietary | Lake Shore Cryotronics, Inc.26
Detected current No detected current
Continuous-Wave THz Spectroscopy
- Detection

26. Proprietary | Lake Shore Cryotronics, Inc.
Continuous-Wave THz Spectroscopy
- Frequency Tuning
27
DFB Laser 1
DFB Laser 2
f1
f2

27. Proprietary | Lake Shore Cryotronics, Inc.28
DFB Laser 1
DFB Laser 2
f1
f2

28. | Confidential Lake Shore Cryotronics, Inc.
Integrated Software for Turn-key Operation
29

29. | Confidential Lake Shore Cryotronics, Inc.
Integrated Software for Turn-key Operation
30

30. | Confidential Lake Shore Cryotronics, Inc.
Integrated Software for Turn-key Operation
31
Sample Reference Background
BLOCK

31. | Confidential Lake Shore Cryotronics, Inc.
Integrated Software for Turn-key Operation
32

32. | Confidential Lake Shore Cryotronics, Inc.
Integrated Software for Turn-key Operation
33

33. Proprietary | Lake Shore Cryotronics, Inc.
Case Study: Sr2CrReO6 Thin Films
34
In-plane
 Double-perovskite ferrimagnet (Tc = 635 K)
 Ms = 1.29 B per f.u.
 Predicted 90% spin polarization
 Large anisotropy
 Stoichiometric, epitaxial, and well ordered
 Well ordered films on STO and LSAT
substrates

34. Proprietary | Lake Shore Cryotronics, Inc.
Case Study: Sr2CrReO6 Thin Films
35
Stoichiometric, epitaxial, and well ordered
 Grown with off-axis magnetron sputtering
1 µm thickness ~ 20 hours
Low material yields
 10 to 200 nm thick film on 10 × 10 mm substrate
 After characterization, wafer is diced & distributed for
device manufacturing
Wafer real estate is at a premium
 Electrical contacts for material evaluation reduce
number of devices — non contact evaluation
 Cryogenic characterization elucidates conduction
mechanisms

35. Proprietary | Lake Shore Cryotronics, Inc.
CW-THz Transmission
36
0.5 1.0 1.5
0.0
0.5
1.0
THzTransmission
Frequency (THz)

36. Proprietary | Lake Shore Cryotronics, Inc.
CW-THz Spectroscopy of
Conductive Thin Films
37
Thickness
Conductivity
Ga-doped ZnO on ZnO

37. Proprietary | Lake Shore Cryotronics, Inc.
SCRO Film DC Conductivity
38
0.0
0.2
0.4
0.6
0.8
1.0
200 400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
120 m LSAT
5 K
50 K
100 K
300 K
1.4 mSCRO on 120 m LSAT
THzTransmission
Frequency (GHz)
300 K
0.0
0.2
0.4
0.6
0.8
1.0
200 400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
120 m LSAT
5 K
50 K
100 K
300 K
1.4 mSCRO on 120 m LSAT
THzTransmission
Frequency (GHz)
300 K

38. Proprietary | Lake Shore Cryotronics, Inc.
Variable Range Hopping Conductivity
39
Variable Range Hopping
5 K
5 K

39. Proprietary | Lake Shore Cryotronics, Inc.
What’s Next
40
– Turn-key acquisition of temperature
and field dependent THz spectra
Taking orders March 2014!
Model 8500
THz System for
Material Characterization
 Customer applications
— samples
 Sponsored research
program to develop
turn-key analysis
software for CW-THz
spectra