Small Sensors at Low Temperature Revealing Cryogenic Turbulence University of Florida Physics Gary Ihas- Yihui Zhou Ridvan Adjimambetov Shu-chen Liu Isaac Luria Mario Padron Miramare June 10, 2005 Andrew Rinzler Jennifer Sippel-Oakley Mark Sheplak-University of Florida Engineering T. Chen Vadim Mitin-V. Lashkarev Institute of Semiconductor Physics, NASU, Kiev, Ukraine Funding: Research Corporation
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Small Sensors at Low Temperature Revealing Cryogenic Turbulence University of Florida Physics Gary Ihas- Yihui Zhou Ridvan Adjimambetov Shu-chen.
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Small Sensors at Low TemperatureRevealing Cryogenic Turbulence
Mark Sheplak-University of Florida EngineeringT. ChenVadim Mitin-V. Lashkarev Institute of Semiconductor Physics, NASU, Kiev, Ukraine Funding: Research Corporation
Thank you Mr. Organizer
In his lab circa 2004 (with research trainee)
Thank you Mr. Director
In his lab circa 2005
Thank you Mr. Helium Vorticity
50th Anniversary of First Direct Detection of Quantized Vorticity
Outline Low Temperature Motivation-Small apparatus
sensitivity (rms energy fluctuation 6 eV at 25mK); T/T ~ 4.810-6
response time < 20 ms size: 1mm1mm0.25mm
2. Miniature Ge Film Resistance Thermistors-- [V.F. Mitin, et al.]
sensitivity =50/K- 100/K in the temperature range 50mK- 10mK
response time< 0.1s size: 650 m
1. Operating temperature: 10 - 100mK.
2. Sensitivity: T ~ 10-7K, or T/T ~ 10-5.
3. Short response time: t ~ 10-3 s.
4. Small mass & good thermal contact.
Conduction in a doped semiconductor
1 10 10010
100
1000
10000
100000
1000000
Electron Collisions
(R~T-1)
Phonon Collisions
(R~T-1/2}
Variable Range Hopping
(R~exp{T-1/4})
Coulomb Interaction
(R~exp{T-1/2})
Re
sist
an
ce ()
Temperature (K)
Mass Production/Consistency•Each wafer will generate sensors with very similar properties•Resistance measurements made on a single batch over the range 10K – 150K•A single fixed point measurement at 4.2K will approximate the sensors properties if the entire curve for any one sensor from the batch is known
1 10 10010
1
102
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Re
sis
tan
ce,
Oh
ms
Tem p erature, K
Advantages of Thin Film Technology
Semiconductor Chip Technology
Ge/GaAs thermistors 300 m square by 150 m thick. Mass of the thermistor = 7.2 10-5 gram.
Active layerInsulator
Thermistor R vs. T Development Work
10 100 10001
10
100
1000
#3
#2
#1
Th
erm
isto
r re
sist
ance
(K
oh
m)
Temperature (mK)
http://microsensor.com.ua/products.html
Pressure Transducer Requirementssampling on micron scale sensitivity: 0.1 Pascal fast: 1 msecfunction at low temperatures (20 – 100 mK) transduction: as simple as possible
Design Of Piezo-resistive Pressure Sensors Typical design: 4 piezo-resistors in Wheatstone bridge on a diaphragm diaphragm deflects from applied pressure causing the deformation of the piezo-resistors mounted on the surface
Wheatstone bridge
Piezo-resistive Pressure Sensor SM5108
Manufactured by Silicon Microstructures, Inc.
Semiconductor resistors joined by aluminum conductors in bridge configuration
Resistors placed on diaphragmTwo strained parallel to ITwo strained perpendicular to I
Piezo-resistive Pressure Sensor SM5108
Drawbacks of Piezo-resistive Pressure Sensors-Results Relatively low sensitivity Large temperature dependence temperature
compensation necessary
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40
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55 300 K 91.2 K - 94.6 K 64.4 K - 66.0 K 49.8 K - 51.0 K 40.4 K - 43.5 K 29.9 K - 30.4 K 22.9 K - 26.0 K 26.2 K
Voltage vs Pressure for Piezoresistive Transducer at varying temperatures
Vo
ltag
e (
mV
)
Pressure (Bar)
Capacitive Pressure Sensors Inherently nonlinear output of the sensor Distributed capacitance of read-out circuit
requires low T amplifierTypical design: parallel-plate capacitor integrated electronics for signal processing reference capacitors for temperature compensation
Advantages And Disadvantages Of Capacitive Pressure Sensors Over Piezo-resistive Sensors Advantages:
Higher sensitivity Long-term stability Smaller temperature dependence
Disadvantages: Non-linear output More complicated manufacturing due to the
integration of the compensation circuit and signal processing electronics to the sensor chip
Relatively high price
Optical Pressure Sensors
Optical techniques typically employ a microsensor structure that deforms under pressure resulting in change in optical signal.
Diaphragm-based sensors, for example, incorporate optical waveguides on the top surface.
Example Of An Optical Pressure Sensor
Simple Interferometer Sensor
Difficulty is readout
Production Process
Attach optical fiber
Nanotube/Film Technology•Small•Strong•Conducting•But not too conducting•Elastic•Stick to some surfaces
Can be used forThermometersHeatersStrain gaugesCapacitor platesFlow metersTurbulence detectors