ultra low power gas sensing for health and environmental ... · ultra low power gas sensing for...

Ultra Low Power Gas Sensing for Health and Environmental Tracker (HET) TestbedStudents: Steven Mills, Daniel Schulman, Alexander Tellado, Michael Lim

Post-docs: Dr. Oren Z. Gall, Dr. Xiahua Zhong

PIs: Veena Misra, Bongmook Lee, Theresa Mayer and Thomas Jackson

Institutions: North Carolina State University and Penn State University

1

Testbeds: HET Block Diagram

Smart Phone

IOIO

Signal Processing

User Interface

Radio

ASSIST CustomTechnologies

Antenna

Power Management

SPI

RADIO

Battery

Sensors

SPIMSP SOC

Breakout Board

Antenna

Power Management

SPI

RADIO

Battery

Sensors

SPIMSP SOC

Breakout Board

CHEST PATCH w/ breakout sensor boards

WRISTBAND w/ breakout sensor boards

Aggregator

Hydration

ECG

Pulse Ox

Accelerometer

Ozone Sensor

Humidity/ Temp Sensor

Pulse Ox

Accelerometer

Microphone

Cloud Storage

Signal Processing

CustomizedOff the Shelf Technologies

Ozone sensor for HET 1.0 2

Metal oxide sensors have good response to gases but suffer from high power and poor specificity

Ozone gas sensors based on metal oxides are commercially used in industrial and automotive

applications

Gas sensor typically operate at temperatures >200 C with the use of microheaters. Power

consumption can reach well over 10 mW

*Spa

nnha

keJ.

Sen

sors

200

6 6,

405

-419

Thin-film based ozone sensor with integrated micro heater

Miniaturization of gas sensors for ubiquitous applications

Most thin film sensors require significant heating

Sensaris

Futurlec

3

Research Goals driven by HET Specifications for Gas Sensing Ultra Low Power ~ 100microwatts

ALD Nanowires ALD nanofilms with room temperature operation Self heating or UV erase

Specificity towards targeted gases (Ozone vs. NO2 vs. CO) Temperature enhanced specificity Filters against ozone E-nose pattern matching

Sensitivity down to 25ppb Nanofilms and nanowires FET approaches

Reversibility at low power levels UV erase Self heating

4

ASSIST Gas Sensing Strategy

Materials

Low Power Sensitivity

Specificity Multi-gas VOCResponse

Time

Sensing Mechanism Systems

Repeatability

Resonant based CMUTs

Field Effect Transistors

Resistance BasedHeterogeneous Field Assisted assembly

Multichannel CMUT

Metal Oxides Nanofilms and

Nanowires

Polymer Coatings

Top Down Arrays

5

5-20nm ALD (tetrakis dimethylamino tin) + H2O + ozone= SnO2

400C 30 min crystallization anneal

10 nm Ti/150 nm Au

Testing Teledyne T700U Ozone generator

Keithley 4200

Characterization and Analysis Sensitivity based on slope of response

Selectivity against NO2 and CO

(top left) Optical image of electrodes and 3D model of sensor (top right) XDS analysis of film (bottom) low and high resolution STEM images showing device structure and film crystallinity

Nanofilms: ALD SnO2 can enable thicknesses down to the Debye length resulting in increased sensitivity

66

Nanofilms: Post processing leads to crystallization of ultrathin SnO2 films 200C deposition temperature Linear deposition rate Rutile crystal phase after 400C anneal

7

Sensing Power consumption

Slope of R correlated with O3 Concentration Response magnitude linearly correlated with ozone concentration

0 1000 2000

20200

20400

20600

20800

21000

21200 O3 Concentration24% RH

Res

ista

nce

()

Time (s)

Room Temperature Response to O3

0

50

100

O3 C

once

ntra

tion

(ppb

)40 50 60 70 80 90 100 110

0.7

0.8

0.9

1.0

1.1

1.2

Sen

sitiv

ity, d

R/d

T (

/s)

O3 Concentration (ppb)

Rate of Change for Room Temperature O3 Exposure

24% RH

Nanofilms: Quantification of R with ozone concentration has been achieved

9

Year 2 SWOT related to Gas Sensing

Attention to sufficient selectivity is lacking in metal oxide gas sensors

Response: we have used two routes to address selectivity

10

Selectivity @ Room temperature

100ppb NO2

Selectivity Towards Gases Using Organic Filters

Improvement in real time detection and selectivity of phthalocyanine gas sensors dedicated to oxidizing pollutants evaluation. Brunet J. et al Thin Solid Films (490) 1 2005 pp.28

Glass or SiO2

GateAl2O3

ZnO

Al2O3

75 nm of a thin film of Indigo dye is deposited over the entire device.

Exposed open active area: no filter

Ozone is expected to be filtered by the indigo film before reaching the ZnO interface

Indigo dye molecule

12

Indigo films prevent ozone from diffusing to sensor surface

Stable ZnO TFT ozone sensor with low power UV sensor reset with

Nanowire Metal-Oxide Sensors

High performance, low-power metal-oxide nanowire sensors Optimal sensitivity when

operated between 100 C to 250C

High surface-to-volume ratio gives enhanced sensitivity

Joule heating for low power dissipation of 10s W per sensor

O2(g)+ 2e- 2O-(s) CO(g)+O-(s) CO2(g)+ e-

Depleted Conducting (n-type)

Power Dissipation

Sensing Mechanism

14

Cross-Reactive Nanosensor Array

Monolithic integration of multiple nanosensor types on CMOS readout and processing circuitry Discrimination through classification of sensor array response On-chip response amplification and signal conditioning

http://lnbd.technion.ac.il/NanoChemistry 15

Metal-Oxide/Si Core-Shell Nanowires

Batch fabrication of metal-oxide nanosensors Optimize process for each

type of metal oxide Uniform and highly

reproducible dimensions High-quality metal-oxide

shell with low impurities and defects

Mechanically robust with intrinsic Si wire core

600nm

Si core ALD MOX shell

1. Deep reactive ion etching of Si wires2. Atomic layer deposition of MOX shell3. Thermal crystallization of MOX shell

under optimized conditions16

Optimized Metal-Oxide Synthesis

Different high-temperature annealing conditions are required to crystallize amorphous metal-oxide shell to optimize sensitivity to target environmental pollutants

30 nm TiO2 shell Anneal: N2 600C, 10 min

30 nm SnO2 shell Anneal: N2 600C, 10 min

30nm SnO2Anneal: O2 650C, 1 hour

anatase rutile rutile

International collaboration with Osaka U (2014) 17

Field-Assisted Directed Assembly

Localized regions of highest field intensity within patterned depressions provide high-yield nanowire assembly with registration to predefined features on the CMOS chip

Dielectrophoretic Force: FDEP E2

log(E2)Top view

Cross section through well

18

Field-Assisted Directed Assembly

Localized regions of highest field intensity within patterned depressions provide high-yield nanowire assembly with registration to predefined features on the CMOS chip

Top view

Cross section through well

Video

19

15 nm SnO2 Shell Sensor Response

Sensitivity to CO of

Uniformity of SnO2 and TiO2 NanosensorsDevices Diameter Variation in Resistance Reference

50 In2O3 nanowire

chemiresistors10nm 45% Zhang, et al.

55 Si nanowire FET 20nm 106% Jin, et al.

40 ITO nanowire resistors 20nm 108% Wan, et al.

30 TiO2 coated nanowires30nm TiO2 coated,

260nm dia.18% this work

30 SnO2 coated nanowires 30nm SnO2 coated,


[i]. Zhang, D., Liu, Z., Li, C., Tang, T., Liu, X., Han, S., Lie, B., Zhou, C. Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices. Nano Lett. 4, 1919-1924 (2004)[ii]. Jin, S., Whang, D., McAlpine, M., Friedman, R., Wu, Y., Lieber, M. Scalable interconnection and integration of nanowire devices without registration. Nano Lett. 4, 915-919 (2004)[iii]. Wan, Q., Dattoli, E., Fung, W., Guo, W., Chen, Y., Pan, X., Lu, W. High-performance transparent conducting oxide nanowires. Nano Lett. 5, 2909-2915 (2006) 21

Highlight Organic EDLC Powered SnO2 Nanosensor Measurement of supercapacitor

discharge current in response to 400 ppm CO exposure

Low power regulator supplies stable operating voltage and demonstrates system level integration with wearable platforms

Supercapacitor energy density = 4J/cc ~40 wires can run for 10min Leakage current

GEN I - Monolithic Integration on CMOS

Prototype CMOS 32 x 32 multiplexer with three metal interconnect layers fabricated by Lincoln Labs foundry for back-end nanosensor assembly and integration

CMOS design Calhoun group, UVA

FESEM image

23

Back-End Nanosensor Integration

Process compatible with single-wire sensor test structures and back-end integration on CMOS

Assemble nanowires

Pattern contacts

Deposit contact metal

Vias to CMOS access

transistor

On-Chip Assembly

24

Integration of 15 nm SnO2 Sensors on CMOS

Comparing the I-V characteristics of an 15 nm SnO2 nanowire sensor when the access transistor is open and closed confirm circuit operation

0 0.5 1-5

0

5

10

15

20

25

Vin (V)

Iin (

A)

OpenWire PresentWire Present90 nm PDK Simulation

Linear Saturation

Circuit used to electrically address individual metal-oxide nanowire sensors N2 at 25C

25

Integration into HET 1.0: SnO2 Nanofilm Sensors

ASSIST Ozone sensor with HET26

Benchmarking ASSIST Low Power ozone sensors

Gas MaterialTem

pSensing range Method

Response time

structure Type

humidity selectivity Ref

O3 CoPc RT20-200

ppb conductometric 5min100 nm

film organic SC N/A O3 over NH3 [30]

O3 SnO2-CNT RT 20 ppb conductometric 4 min compositeMOx

hybrid N/A N/A [33]

O3 In2O3 RT20-2400

ppb conductometric 16/75 min5 m

porous film MOx 20~40% N/A [35]

O3 SnO2-CNT RT 20 ppb conductometric 3/20 min200 nm

filmMOx

hybrid Zero Air N/A [37]

O3 ZnO-InOx RT16-2300

ppb conductometric 10 min 1 m film MOx Zero Air N/A [40]

O3 SnO2 RT 58 ppb conductometric 1/20 min100 nm

film MOx Zero Air N/A [41]

O3 ZnO RT30-600

ppb conductometric 2 min100 nm

NW MOx Zero Air N/A [42]

O3Poly-

butadiene RT 28-50 ppb frequency shift 4 min tuning fork Polymer N/A N/A [43]

O3ALD SnO2

RT 20-300 ppb conductometric 1 min 7 nm film MOx Zero AirOnly Sensitive

to O3

NCSU ALD based ozone sensors provide highly sensitive (20 ppb) with very fast response time and only sensitive to ozone.

27

Summary Nanofilms of ALD SnO2 provide room temperature ozone

sensing with power levels of 100nWatts and recovery via UV erase

Selectivity of sensors has been achieved by i) room temperature operation of SnO2 nanofilms and ii) use of organic filters

Nanowires were integrated with CMOS for cross-reactive nanosensor arrays

ALD nanofilm SnO2 sensors have been packaged and delivered to HET Testbed team

Future work: Reducing nanowire diameter and UV free recovery of gas sensors

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Preliminary results towards UV free recovery using SnOx nanotiles

Thermal CVD process: Graphite/SnO2nanoparticle mixture heated to 900C

Substrate located downstream of furnace

0 1000 2000 3000 4000 5000 6000 7000 8000 900011500

12000

12500

13000

13500

14000

14500

15000

15500

16000

16500

AirAirAirAirAirAirAirAirAirAirAir

10 ppb O3

10 ppb O3

20 ppb O3

30 ppb O3

40 ppb O3

50 ppb O3

60 ppb O3

70 ppb O3

80 ppb O3

90 ppb O3

Air

Res

ista

nce

()

Time (s)

100 ppb O3

UV free recovery at RT Reducing response to ozone Very high sensitivity to O3 at RT Possibility: p-type SnOx films

29

Thank you

30

Scaling to Smaller Nanosensors

=1E-8W/nmK-1,L=300nm, S=(RNW2-RSi2)=2E4nm2 , S*=2RNWL=8E5nm2,T=T-T0 =100K

Pmetal 4S T/L~280W

Pgas 0

S*T~20W

Prad~S*(T4+T3T0+T2T02+TT03-4T04)

References

[1] Appl. Phys. Lett. 93, 123110 (2008)

[2] Sensors and Actuators B 77 (2001) 496-502

[3] Sensors and Actuators B 124 (2007) 7483

[4] Sensors and Actuators B 169 (2012) 151 160


[6] Sensors and Actuators B 171 172 (2012) 18 24

[7] IEEE SENSORS JOURNAL, VOL. 12, NO. 5, MAY 2012

[8] Procedia Engineering 25 (2011) 1417 1420


[10] Sensors and Actuators B 169 (2012) 113 120[11] Current Applied Physics 13 (2013) 526e532[12] Cryst. Growth Des.2007, 7, 2500[13] Nano Lett.2004, 4, 1919[14] Nanotechnology 2008, 19, 095508[15] Sens. Actuators B 2005, 107, 708[16] Angew. Chem. Int. Ed.2006, 45, 261[17] Appl. Phys. Lett.2006, 88, 203101[18] Appl. Phys. Lett.2007, 90, 173119




[22] Sensors and Actuators B: Chemical(2012)[23] Nanotechnology 2008, 19, 175502

[24] J. Mater. Res. 2006, 21, 2894[25] J. Phys. Chem. C 2008, 112, 10784[26] J. Phys. Chem. C 2008, 112, 9061[27] J. Mater. Res. 2008, 23, 2047





[32]IEEE Transactions on Nanotechnology, VOL. 10, NO. 5, SEPTEMBER 2011

[33] Journal of Physics: Conference Series 307 (2011) 012054[34] Thin Solid Films 520 (2011) 966970[35] Thin Solid Films 520 (2011) 918921[36] J. Mater. Chem., 2012, 22, 6716



[39] Sensors and Actuators B 168 (2012) 8 13[40] Vacuum 86 (2012) 495e506

[41] Sensors and Actuators B 176 (2013) 811 817[42] small 2012, 8, No. 21, 33073314[43] Sensors 2009, 9, 5655-5663




Uniformity of SnO2 and TiO2 NanosensorsDevices Diameter Variation in Resistance Reference

50 In2O3 nanowire

chemiresistors10nm 45% Zhang, et al.

55 Si nanowire FET 20nm 106% Jin, et al.

40 ITO nanowire resistors 20nm 108% Wan, et al.

30 TiO2 coated nanowires30nm TiO2 coated,


30 SnO2 coated nanowires 30nm SnO2 coated,


[i]. Zhang, D., Liu, Z., Li, C., Tang, T., Liu, X., Han, S., Lie, B., Zhou, C. Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices. Nano Lett. 4, 1919-1924 (2004)[ii]. Jin, S., Whang, D., McAlpine, M., Friedman, R., Wu, Y., Lieber, M. Scalable interconnection and integration of nanowire devices without registration. Nano Lett. 4, 915-919 (2004)[iii]. Wan, Q., Dattoli, E., Fung, W., Guo, W., Chen, Y., Pan, X., Lu, W. High-performance transparent conducting oxide nanowires. Nano Lett. 5, 2909-2915 (2006) 33

TiO2 Nanosensor Response Benchmark

Type Sensitivity tresponse

(minutes)

trecovery

(minutes)

Temp.

(C)

[H2] (ppm) Reference

Nanotube 3 20 16 180 1000 Varghese, et al.

Thin film 2.5 1.5 NA 250 1000Ren, et al.

Thin film 19 0.3 NA 370 5000Tang, et al.

Nanotube 26 30 30 150 1000Sennik, et al.

Nanowire 25 29 15 175 1000 This work[i]. Varghese, et al. Adv. Mater. 15, 624-627 (2003)

Ren et al. Sens. Actua. B 148, 195-199 (2010)[ii]. Tang et al. Sens. Actuat. B 26, 71-75 (1995)[iii]. Sennik, et al. International Journal of Hydrogen Energy 35, 4420-4427 (2010)

34

Ultra Low Power Gas Sensing for Health and Environmental Tracker (HET) TestbedTestbeds: HET Block DiagramMetal oxide sensors have good response to gases but suffer from high power and poor specificityResearch Goals driven by HET Specifications for Gas SensingASSIST Gas Sensing StrategyNanofilms: ALD SnO2 can enable thicknesses down to the Debye length resulting in increased sensitivityNanofilms: Post processing leads to crystallization of ultrathin SnO2 filmsALD nanofilms of SnO2 can sense ozone at room temperature resulting in significant savings in power consumptionNanofilms: Quantification of R with ozone concentration has been achievedYear 2 SWOT related to Gas SensingNanofilm sensors exhibit intrinsic selectivity towards Ozone at room temperatureSelectivity Towards Gases Using Organic FiltersIndigo films prevent ozone from diffusing to sensor surfaceNanowire Metal-Oxide SensorsCross-Reactive Nanosensor ArrayMetal-Oxide/Si Core-Shell NanowiresOptimized Metal-Oxide SynthesisField-Assisted Directed AssemblyField-Assisted Directed Assembly15 nm SnO2 Shell Sensor ResponseUniformity of SnO2 and TiO2 Nanosensors Highlight Organic EDLC Powered SnO2 Nanosensor GEN I - Monolithic Integration on CMOSBack-End Nanosensor IntegrationIntegration of 15 nm SnO2 Sensors on CMOSIntegration into HET 1.0: SnO2 Nanofilm SensorsBenchmarking ASSIST Low Power ozone sensorsSummaryPreliminary results towards UV free recovery using SnOx nanotiles Thank youScaling to Smaller NanosensorsReferencesUniformity of SnO2 and TiO2 Nanosensors TiO2 Nanosensor Response Benchmark

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