Micro-Nano Thermal-Fluid: Physics, Sensors, Measurements Cantilever Sensors: An Example of what you will learn in ME 3

1. Micro-Nano Thermal-Fluid: Physics, Sensors, Measurements Cantilever Sensors: An Example of what you will learn in ME 381R Prof. Li Shi Micro-Nano Thermal-Fluid Laboratory Department of Mechanical Engineering The University of Texas at Austin lishi@mail.utexas.edu

2. Outline • Cantilever Thermal Sensors: Thermal Property of Nanotubes and Nanowires • Cantilever Thermal Sensors: Scanning Thermal Microscopy • Cantilever Bio Sensors • Cantilever IR Sensors

3. Silicon Nanoelectronics Gate Source Drain Nanowire Channel Courtesy: C. Hu et al., Berkeley

4. Length Scale Lattice vibration Wl: boundary scattering - W + - L Size of a Microprocessor MEMS Devices 1 mm Thin Film Thickness in ICs 100 nm l (Phonon mean free path at RT) 10 nm Nanowire Diameter 1 nm Atom 1 Å

5. k = C v l 1 3 Thermal Conductivity Phonon Mean Free path Specific heat Sound velocity Mean free path: Umklapp phonon scattering Static scattering (phonon -- defect, boundary)

6. Silicon Nanowires Increased boundary scattering  Suppressed thermal conductivity  Localized hot spots Bulk Si: k ~150 W/m-K Diameter: Li, et al.

7. Thermoelectric Nanowires Bi or Bi2Te3 nanowires (Dresselhaus et al., MIT): Top View Al2O3 template Smaller d, shorter boundary scattering mfp  Lowered thermal conductivity k = Cvl/3  High ZT, high COP TE Cooler Hot I Thermoelectric Figure of Merit: ZT = S2Ts / k N P Cold

8. Carbon Nanotubes Multiwall -- Metallic 10 nm Super high current 109 A/cm2 Single Wall -- Semiconducting or Metallic microns 1-2 nm

9. Thermal Conductivity of Nanotubes • Strong SP2 bonding (high v), few scattering (long l)  high k • Theory: 3000 ~ 6000 W/m-K at RT (e.g. Berber et al., 2000)

10. A Cantilever Sensor for Thermal Sensing of Nano- Wires/Tubes Suspended SiNx Membrane Long SiNx Cantilever Pt Resistance Heater/Thermometer

11. Thermal Conductance: 14 nm multiwall tube VTE Beam Thermopower: Q = VTE/(Th-Ts) Island Pt heater line Measurement Scheme Gt =kA/L T T T s s h Q I R t R R h = h h s T u be Q = IR l l Environment I T 0

12. (c) Lithography Device Fabrication Photoresist (a) CVD SiNx SiO2 (d) RIE etch Si (b) Pt lift-off Pt (e) HF etch

13. Thermal Conductivity ~T2 l ~ 0.5 mm 14 nm multiwall tube • Room temperature thermal conductivity ~ 3000 W/m-K • k ~ T2 : Quasi 2D graphene behavior at low temperatures • Umklapp scattering ~ 320 K , l ~ 0.5 mm Kim, Shi, Majumdar, McEuen,Phy. Rev. Lett 87, 215502-1 (2001)

14. Thermopower For metals w/ hole-type majority carriers:  T

15. Single Wall Carbon Nanotubes Nanotube

16. High-efficiency refrigerators! Bi2Te3 Nanowire

17. Outline • Cantilever Thermal Sensors: Thermal Property of Nanotubes and Nanowires • Cantilever Thermal Sensors: Scanning Thermal Microscopy • Cantilever Bio Sensors • Cantilever IR Sensors

18. Nanotube Interconnect (Dai et al., Stanford) Molecular Electronics TubeFET (McEuen et al., Berkeley) Nanotube Logic (Avouris et al., IBM)

19. Electron Transport in Nanotubes Ballistic (long mfp) Diffusive (short mfp) - - + + - - mfp: electron mean free path Ballistic (Frank et al., 1998) Diffusive (Bachtold et al., 2000) Multiwall Ballistic at low bias (Bachtold ,et al.) Diffusive at high bias (Yao et al., 2000) Single Wall Metallic

20. Dissipation in Nanotubes Nanotube Electrode bulk Electrode Junction Diffusive – Bulk Dissipation T T profile  diffusive or ballistic X Ballistic – Junction Dissipation T X

21. Thermal Microscopy Techniques Spatial Resolution Infrared Thermometry 1-10 mm* Laser Surface Reflectance 1 mm* Raman Spectroscopy 1 mm* Liquid Crystals 1 mm* Near-Field Optical Thermometry < 1mm Scanning Thermal Microscopy (SThM) < 100 nm *Diffraction limit for far-field optics

22. Thermal Topographic Z T X X Scanning Thermal Microscope Atomic Force Microscope (AFM) + Thermal Probe Laser Deflection Sensing Cantilever Temperature Sensor Sample X-Y-Z Actuator

23. Ta Rc Rt Tt Rts Ts Q Thermal Probe

24. Pt SiO2 SiO2 tip 200 nm 1 mm Probe Fabrication

25. 10 mm Microfabricated Probes Pt Line Tip Pt-Cr Junction Laser Reflector SiNx Cantilever Cr Line Shi, Kwon, Miner, Majumdar, J. MicroElectroMechanical Sys., 10, p. 370 (2001)

26. Locating Defective VLSI Via Tip Temperature Rise (K) Topography 19 21 40 mA Via Metal 1 23 28 25 Metal 2 20 mm Cross Section Passivation • Collaboration: TI • Shi et al., Int. Reli. Phys. • Sym., p. 394 (2000) Metal 2 Dielectric 0.4 mm Via Metal 1

27. Thermal Imaging of Nanotubes Thermal 30 10 10 20 5 5 Height (nm) Height (nm) 30 nm 30 nm 10 0 0 0 -400 -200 0 200 400 -400 -400 -200 -200 0 0 200 200 400 400 Distance (nm) Distance (nm) Multiwall Carbon Nanotube Topography Topography 3 V m 88 A m m 1 1 m m Spatial Resolution V) m 30 nm 50 nm 50 nm Thermal signal ( Distance (nm) Shi, Plyosunov, Bachtold, McEuen, Majumdar, Appl. Phys. Lett., 77, p. 4295 (2000)

28. Multiwall Nanotube Shi, Kim, et al. Thermal Topographic DTtip A B 3 K 1 mm 0 • Diffusive at low and high biases B A A B

29. Low bias: ballistic contact dissipation High bias: diffusive bulk dissipation Metallic Single Wall Nanotube Optical phonon Topographic Thermal DTtip A B C D 2 K 0 1 mm

30. Outline • Cantilever Thermal Sensors: • Thermal Property of Nanotubes and Nanowires • Cantilever Thermal Sensors: • Scanning Thermal Microscopy • Cantilever Bio Sensors • Cantilever IR Sensors

31. New: Micro-cantilever ~500 m A B deflection Detecting Biomolecules Conventional: Fluorescence probes add sample • Surface stress  • Fewer steps • Label - free wash, add marker, wash

32. Chemo-mechanical database: PSA • Prostate-specific antigen (PSA) • Important levels are ~1-10 ng/mL (30-300 pM) •  ~ 5 - 10 mJ/m2, independent of cantilever geometry.

33. CCD A B • 1 laser • 1 detector N lasers, N detectors. Multiplexing Why? Throughput Differential Signal Molecular Profile

34. Outline • Cantilever Thermal Sensors: • Thermal Property of Nanotubes and Nanowires • Cantilever Thermal Sensors: • Scanning Thermal Microscopy • Cantilever Bio Sensors • Cantilever IR Sensors (See PowerPoint File 2)