1 / 65

Surface Forces in Nanomechanical Systems: Living on the Edge

Surface Forces in Nanomechanical Systems: Living on the Edge. J Provine Stanford University 2012-01-11 Fermilab Colloquium. Outline. Scaling in the micro/nanometer range Introduction to several surface effects Nanoelectromechanical Switches Application As a nanoprobe

bryant
Download Presentation

Surface Forces in Nanomechanical Systems: Living on the Edge

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Surface Forces in Nanomechanical Systems: Living on the Edge J ProvineStanford University 2012-01-11 Fermilab Colloquium

  2. Outline • Scaling in the micro/nanometer range • Introduction to several surface effects • Nanoelectromechanical Switches • Application • As a nanoprobe • Device design for probing surface forces • Conclusion

  3. Outline • Scaling in the micro/nanometer range • Introduction to several surface effects • Nanoelectromechanical Switches • Application • As a nanoprobe • Device design for probing surface forces • Conclusion

  4. A few quick words on scaling • We live in the m-cm world (100to 10-2m) • MicroElectroMechanical Systems (MEMS) and CMOS electronics circa 1990 1µm (10-6m) • Current CMOS, thin film optical coatings, NEMS 10nm (10-8m) • Carbon Nanotubes, atomic layer deposition coatings, self assembled monolayers 1nm (10-9m) • Lattice constant of Si 5.4A (10-10m) • Fermilab…

  5. The Dominance of Surface Effects Volume 4/3  r3 Surface Area 6  r2 Surface Area:Volume 1/r As the size of an object shrinks, the surface affects become more dominant because the object is becoming “all surface.”

  6. Outline • Scaling in the micro/nanometer range • Introduction to several surface effects • Nanoelectromechanical Switches • Application • As a nanoprobe • Device design for probing surface forces • Conclusion

  7. Some surface effects in nanodevices • Photonics effects • Adhesion (geckos) • Nourredine smith wear/friction • Casimir Force

  8. Surface Effects in Photonics 1. Make any material a good optical material 2. Get at the unique optical properties of specific materials Various unique optical material properties can be explored and exploited now because of great materials understanding. Polariton Modes Kerr Effect Birefringence Photoelectric transduction • New ways to get excellent optical performance from a wide range of materials. • Photonic Crystal and Subwavelength Grating design for allows a very wide range of materials to provide desired performance.

  9. Excellent test bed for some deep physics experiments (QED, surface physics, etc.) Telecom and Photonic circuits. Slow light. PCs come in many flavors Lin, et al, 2003 Kuchinsky, et al, 2002

  10. Broadband Reflector Applications • High temperature, high power handling. • CMOS compatible and integrable processing. M.C.Y. Huang, Y. Zhou, and C. Chang-Hasnain, Feb. 2007 I. Jung, S. Kim, O. Solgaard, Trans. 2007

  11. Monolithic Si Photonic Crystal Slab Monolithic photonic crystal Slab photonic crystal Dielectric stack (DBR)

  12. Materials for PC 20nm (2%) Increase 20nm (5%) Increase • Extensive testing has been done for particular materials (Si, poly-Si, SiN, SiO2) • But the key is ANY DIELECTRIC can be used to design PCs. • Strong wavelength dependent guided or reflected modes can be created in materials to suit specific applications. Polysilicon thickness change Air gap thickness change 10nm (3%) Increase 0.2 (5%) Increase Refractive index change Hole radius

  13. PC Fiber Tip Sensor Applications • Biological, chemical, and mechanical sensors (such as accelerometers) at the end of an optical fiber can be useful for control and security applications • The small size (125 µm diameter) enables them to penetrate tissue or veins for medical applications • PCs at the tip of fibers can be used both for free-space and inline applications as a reflector, polarizer and filter

  14. Fiber Tip Assembly Pt weld of PC Direct weld of PC Utilize direct weld of PC with ion beam as opposed to Pt weld to study impact of weld technique.

  15. Broadband source Power meter 3dB coupler Optical spectrum analyzer Fiber PC Water/Solvent Index Sensing Experiment Index Sensing Experiment Experimental data

  16. Refractive Index Sensing Isopropanol concentration increase in increments of 30ml in DI Water of 150ml Refractive index calculated from volume concentration • Responsivity = DR.I./Dl = 0.04768 [nm-1] • Sensitivity ≈ 4.8 x10-5 [pm-1] • Using an optical system (tunable laser, OSA) with picometer resolution • Comparable to FBG refractive index sensors [W. Liang, A. Yariv et al, APL 2005] IEEE Nanophotonics 2009.

  17. Temperature Sensing Experiment Temperature Sensing Experiment Experimental data

  18. Temperature Sensing Temperature measurement taken while cooling from 80°C to room temperature • Responsivity = Dtemp/Dl = 16.0858 [°C/nm] • Sensitivity ≈ 0.016 [°C/pm] • Using an optical system (tunable laser, OSA) with picometer resolution • Almost an order better sensitivity than a FBG temperature sensor [A. D. Kersey et al., Fiber Grating Sensors Invited Paper, JLT 1997] LEOS annual meeting 2009

  19. [blog.mlive.com] [Onur Kilic] [www.cnconveyorbelt.com] [www.tommcmahon.net] [www.blueparrotevents.coml] [www.reuk.co.uk] [www.gallagher.com] [newswhitehouse.com] [www.af.mil] Impact & Applications • Harsh environments • High voltage, high power machinery • High temperature • Motion/Vibration/Explosion detection • Acoustic sensing • Gyro/Acceleration • Bio/chemical detection • Biological/chemical agents • Fluid, Gas sensing • Structural Health monitoring • Combustion chambers, Turbines • Aircraft, wind turbines, bridges, dams, oil wells, pipelines • Smart structures: Integrated fiber-optic sensors (aging, vibrations)

  20. Accessing a particular optical property in a novel material: SiC Spitzer, et al, Phys Rev., 1959. SiC coating The optical properties of SiC have also been studied for a long time. Recently the interest has expanded because of the extremely strong mid-IR Phonon Polariton resonance. Si beam 1m

  21. Device Fabrication SiO2 SiC LPCVD SiC @ 800C LPCVD SiO2 for hard mask Bulk Si Transfer photolithographic mask through SiO2 and SiC by RIE RIE of SiC is HBr/HCl Bulk Si Release membrane by XeF2 etch Remove hard mask with HF dip 80 sidewall

  22. Extraordinary Transmission Polariton Gap t = 4m a = 10.4m d = 5.6m Hole Array Patterned Film Unpatterned Film a d t Theroretical simulation with FD3D Finite Difference Time Domain code.

  23. Extraordinary Transmission Polariton Gap Polariton Gap Hole Array Patterned Film Unpatterned Film t = 4m a = 10.4m d = 5.6m t = 1.5m Polycrystalline SiC Experimental Data from FTIR Unpatterned Film

  24. Extraordinary Transmission Polariton Gap Polariton Gap Hole Array Patterned Film d=5.6m Unpatterned Film t = 4m a = 10.4m d = 5.6m t = 1.5m a = 10m Polycrystalline SiC Experimental Data from FTIR Unpatterned Film

  25. Extraordinary Transmission Polariton Gap Polariton Gap Hole Array Patterned Film d=5.6m d=3.9m Unpatterned Film t = 4m a = 10.4m d = 5.6m t = 1.5m a = 10m Polycrystalline SiC Experimental Data from FTIR Unpatterned Film Provine, et al, OMEMS 2007

  26. Reflection Spectra t = 1.5m a = 10m Polycrystalline SiC Experimental Data from FTIR d=3.1m d=3.9m d=4.8m d=5.6m

  27. Ongoing Experiments: A True Meta-Material • Selective metal surface coatings. (Catrysse and Fan, Physical Review B, 2007)

  28. Adhesion at the Nanoscale Work between Autumn Lab (Lewis & Clark) & Kenny Lab (Stanford)

  29. Casimir Force in Metals • Uncharged metals (equipotential) will still attract. • Purely a quantum & geometrical effect. • Hotly debated and studied because of the relation to the cosmical constant. • At the nanoscale starts to have appreciable forces. Valid at 0 K and vacuum.

  30. Casimir effect in Ptnanobeams Nanobeam constructed from a single sheet of evaporated Pt (equipotential). Slices are made with ion beam and then released from unlying Si with XeF2. Crystal orientation makes this a challenging study.

  31. Outline • Scaling in the micro/nanometer range • Introduction to several surface effects • Nanoelectromechanical Switches • Application • As a nanoprobe • Device design for probing surface forces • Conclusion

  32. Application: a downside of scaling • As modern CMOS electronics scales to smaller and smaller devices, the power consumption rising rapidly. • Because of the ubiquitous computing ongoing (and being proposed) the amount of energy going to servers and even personal computing is becoming appreciable. E. J. Nowak, IBM J. Res & Dev. 2002

  33. A Solution: Back to the Future • Mechanical computing can be an answer to this issue because it can deliver zero off-state power consumption. • Additional benefits: • Radiation hard operation • Lower thermal dependence • Is this a CMOS killer? NO • But it can have many applications and certainly help with energy consumption. (see for instance Chen et al FPGA 2010.) Babbage Analytical Engine c 1877

  34. Implementing a NEM Swith

  35. Examples of NEM Switches:Metallic Structures Vertically actuated W Colorado, Boulder Laterally actuated Ru Sandia National Labs Vertically actuated Ni KAIST

  36. Examples of NEM SwitchesConducting Ceramics Laterally actuated TiN Stanford Vertically actuated TiN KAIST

  37. Examples of NEM Switches:Semiconducting Structures Vertically actuated W coated SiGe California, Berkeley Vertically actuated poly-Si KAIST

  38. Arbitrary NEM Logic Design Methodologies • Only 6T relays required for all 3 generations • Our lateral 6T elemental logic block • New elemental block allows new design methodologies G

  39. The Logic Element: 6T Relay Source 1 Gate 1 Isolation Beam Drain Source 2 Gate 2 =Insulating Layer (eg, Hafnium Oxide) =Mold Layer (eg, Polysilicon) =Conductive Layer (eg, TiN or Pt)

  40. Y-Device Process Flow AA’ BB’ (a) Deposit 1um polysilicon on 1.5um oxide. Oxide Substrate (b) Pattern polysilicon (mask 1).

  41. Y-Device Process Flow AA’ BB’ (c) Deposit 20nm HfO2 via ALD. (d) Blanket etch of HfO2.

  42. Y-Device Process Flow AA’ BB’ (e) Deposit 20nm Pt or TiN via ALD. (f) Etch Pt or TiN and pattern pads (mask 2).

  43. Y-Device Process Flow AA’ BB’ (g) Pt or TiN wet etch for sidewall isolation (mask 3). (h) Release in 49% HF followed by CPD.

  44. Fabricated Device

  45. Y-Device Switching Properties Current Flow (Source to Drain) No Beam Current [S. Lee et al., Transducers 2011]

  46. Mechanical Delay Measurement 1.2µs

  47. Easy, right? Not Always

  48. ALD Platinum Coated Relay • Large pull-out variation! • Adhesion force variations: asperity deformation Single device, multiple cycles

  49. Other issues • Desired improvement in • Total Lifetime • Uniformity between devices (same chip) • Uniformity between devices (different wafers) • Concerns • Fabrication tolerance • Adhesion forces • Contact Resistance

  50. NEM Relays with improved contact properties Controlling the contact mechanism and apparent contact area: Flexible Contact Surface Existing designs Before pull-in After pull-in Point contact Overdrive voltage surface-surface contact Point-surface contact mechanism with limited asperity-asperity contact Flexible surface-surface contact

More Related