Science and Technology of Ultrananocrystalline Ultrananocrystalline - PowerPoint PPT Presentation

Science and Technology of Ultrananocrystalline Ultrananocrystalline Science and Technology of Diamond Films for Multifunctional MEMS/NEMS Diamond Films for Multifunctional MEMS/NEMS H.D. Espinosa Acknowledgments: NSF-NIRT U.S. – South America Workshop: Mechanics and Advanced Materials Research and Education Rio De Janeiro, Brazil, August 2-6, 2004 Micro and Nanomechanics Lab Department of Mechanical Engineering

Outline Outline � NIRT Project Overview � Film Deposition and Characterization � Identification of Mechanical Properties � Multiscale Modeling starting from Quantum Mechanics � Applications: � AFM Potentiometry � Molecular Writing and Self Assembly � NEMS, e.g., nanoresonators Micro and Nanomechanics Lab Department of Mechanical Engineering

Participating Institutions/Overview Participating Institutions/Overview Micro and Nanomechanics Lab Department of Mechanical Engineering

Ultrananocrystalline Diamond Films For Diamond Films For Ultrananocrystalline Multifunctional MEMS/NEMS Devices Multifunctional MEMS/NEMS Devices H.D. Espinosa, Z. Chen, T. Belytschko, M. Hersam, G. Schatz, O. Auciello and M. Moldovan Why UNCD? Applications Massively parallel AFM potentiometry Extreme mechanical hardness (~97 GPa) Very high elastic modulus (965 GPa) Highest thermal conductivity (2 x 10 3 W/m/ K) Broad optical transparency α 2 E ϖ = t Low threshold, stable field electron emission (~2-3 Nanoresonators ρ L 12 V/ µ m) • Mass Sensors Very resistant to chemical corrosion • Wireless Communication Extremely high wear resistant (10,000 times longer than Si) • Bio-sensors Very low friction coefficient (0.03-0.04 in air) • … Micro and Nanomechanics Lab Department of Mechanical Engineering

Film Deposition Film Deposition Orlando Auciello Auciello and John Carlisle (ANL) and John Carlisle (ANL) Orlando Micro and Nanomechanics Lab Department of Mechanical Engineering

iPlas Microwave Plasma CVD System at ANL Microwave Plasma CVD System at ANL iPlas Seeding CH 4 + Ar + H 2 = 100 sccm 2CH 4 → C 2 H 2 +3H 2 CH 4 = 1 sccm; Ar = 95-99 sccm C 2 H 2 → C 2 + H 2 100 Torr; 1200 W UNCD Growth Rate: 0.15 ~ 0.2 µm/hr (400 o C) 0.25 ~ 0.3 µm/hr (800 o C) C 2 emission C 2 - Main species for Intensity (a.u.) the growth of UNCD 200 400 600 800 1000 1200 Wavelength (nm) Typical Ar/CH 4 Plasma OES of Ar/CH 4 Plasma D. Gruen, “Nanocrystalline Diamond Films,” Annu. Rev. Mater. Sci. , Vol. 29, pp. 211-259, (1999). Micro and Nanomechanics Lab Department of Mechanical Engineering

Grain Size vs. Ar Ar Ratio Ratio Grain Size vs. � Grain size as a function of the Raman Spectra shows the Raman Spectra shows the Ar ratio: (a) 40%, (b) 60%, (c) diamond band is broadened diamond band is broadened 97%, (d) 99%. D. Zhou et. al., J. Appl. Phys. , Vol. 84, pp 1981-1989, (1998). Micro and Nanomechanics Lab Department of Mechanical Engineering

Grain Size vs. N 2 Ratio Grain Size vs. N 2 Ratio Grain + Grain boundary morphology Grain + Grain boundary morphology (a) 0% N 2 (a) 0% N 2 UNCD, (b) 5% N UNCD, (b) 5% N 2 2 UNCD, (c) 10% N UNCD, (c) 10% N 2 2 UNCD, (d) 20% N UNCD, (d) 20% N 2 2 UNCD. Grain size increase from 4 to 16 nm; grain boundary width UNCD. Grain size increase from 4 to 16 nm; grain boundary width increases from 0.5 to 2.2 nm. N 2 increases from 0.5 to 2.2 nm. N 2 is incorporated preferentially at the is incorporated preferentially at the grain boundaries. grain boundaries. J. Birrell J. Birrell et al., App. Phys. Let., Vol. 81, pp. 2235 et al., App. Phys. Let., Vol. 81, pp. 2235- -2237, 2002. 2237, 2002. Micro and Nanomechanics Lab Department of Mechanical Engineering

Super Grains Super Grains 100 nm Micro and Nanomechanics Lab Department of Mechanical Engineering

Scanning Probe Microscopy Characterization of Scanning Probe Microscopy Characterization of UNCD UNCD Effect of Substrate: Si vs. W/Si M. Hersam’s group (Top Surface) (a) (b) (a) Topside of an undoped UNCD film on a Si substrate with roughness of 20 nm. (b) Topside of an undoped UNCD film on a W/Si substrate with roughness of 14 nm. Micro and Nanomechanics Lab Department of Mechanical Engineering

Scanning Probe Microscopy Characterization of Scanning Probe Microscopy Characterization of UNCD (con’t con’t) ) UNCD ( Effect of Substrate: Si vs. W/Si (Bottom Surface) (a) (b) (a) Backside of an undoped UNCD film on a Si substrate with roughness of 3 nm. (b) Backside of an undoped UNCD film on a W/Si substrate with roughness of 1 nm. Micro and Nanomechanics Lab Department of Mechanical Engineering

Contact Mode AFM Measurements Contact Mode AFM Measurements Initial cAFM Data (Undoped vs. N 2 Doped UNCD) M. Hersam’s group 1.2E-10 9.E-09 8.E-09 1E-10 7.E-09 8E-11 6.E-09 Current (A) Current (A) Upsweep 5.E-09 Upsweep 6E-11 Downsweep Downsweep 4.E-09 4E-11 3.E-09 2.E-09 2E-11 1.E-09 0 0.E+00 0 2 4 6 8 10 12 0 2 4 6 8 10 12 Voltage (V) Voltage (V) 10% N-Doped: R ~ 0.3 G Ω Undoped: R ~ 50 G Ω cAFM I-V spectroscopy taken with a Pt coated tip Micro and Nanomechanics Lab Department of Mechanical Engineering

Mechanical Testing Mechanical Testing • Modulus Modulus • • Strength Strength • • Fracture Toughness Fracture Toughness • Micro and Nanomechanics Lab Department of Mechanical Engineering

Wafer Level Micro- -scale Tension Test scale Tension Test Wafer Level Micro Line-load Tip Membrane Gauge Area Interferometric Objective Membrane Deflection Experiment (MDE) - Use Nanoindenter to stretch membrane - Obtain load-deflection response and stress-strain curve, extract E , σ r and σ f - Fracture Toughness, K IC H.D. Espinosa et al., J. Mech. Phys. Sol. , Vol. 51, pp. 47-67, 2003 Micro and Nanomechanics Lab Department of Mechanical Engineering

UNCD MDE Specimens UNCD MDE Specimens 4” wafer 200 µ m Non-uniformities due to wafer seeding process 20 µm Micro and Nanomechanics Lab Department of Mechanical Engineering

Fabrication Steps Fabrication Steps Al film (a) Si substrate <100> UNCD Etch Si 3 N 4 (b) (RIE) Si 3 N 4 (c) Etch Si (wet) (d) Etch UNCD (RIE) Fabrication steps on <100> Si wafers: (a) Deposition of UNCD film followed by Al film deposition (b) Wet etching of Al to define the pattern of UNCD (c) Dry etching of Si 3 N 4 followed by wet etching of Si (d) Dry etching of UNCD (O 2 plasma), removing the Al film Micro and Nanomechanics Lab Department of Mechanical Engineering

Stress Calculations Stress Calculations Combined AFM/Nanoindenter with Integrated Mirau Microscope-Interferometer Cauchy Stress P ( t ) σ t = ( ) V θ A 2 sin( ) m σ (τ) = Stress at time t L M P V P V (t) = load at time t θ ∆ Wafer P M P M A m = membrane cross-sectional area Mirau H.D. Espinosa et al . J. Mech. Phys. Microscope Sol. , Vol. 51, No. 1, pp. 47-67, 2003 Objective Micro and Nanomechanics Lab Department of Mechanical Engineering

Strain Calculations Strain Calculations Strain δ + λ 2 2 ( / 2 ) ε t = − ( ) 1 δ ε (t) = Strain at time t Bottom surface of membrane (c) Fringes δ = distance between fringes δ λ = wavelength of interferometer θ 1 light. λ/2 3 λ/4 λ/2 λ/4 Fringes Micro and Nanomechanics Lab Department of Mechanical Engineering

Stess- -Strain Curves Strain Curves Stess 4500 σ f1 σ = 4.17 GPa GPa f1 = 4.17 4000 3500 σ f2 σ = 2.71 GPa GPa f2 = 2.71 3000 Stress (MPa) σ f3 σ = 2.45 GPa GPa f3 = 2.45 2500 2000 σ f4 σ = 2.35 GPa GPa f4 = 2.35 1500 Undoped 5% Nitrogen The stress at 63% failure 1000 10% Nitrogen probability 500 20% Nitrogen 0 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045 Strain Sample Undoped Doped Sample Undoped Doped N N 2 2 percentage percentage 0% 0% 5% 5% 10% 10% 20% 20% No. of tests 30 30 30 30 No. of tests 30 30 30 30 E (GPa E ( GPa) ) 940- 940 -970 970 878- 878 -921 921 854- 854 -880 880 833- 833 -865 865 σ 0 σ (MPa MPa) ) 4172 4172 2713 2713 2446 2446 2350 2350 0 ( Micro and Nanomechanics Lab Department of Mechanical Engineering

Size Effect – – Applicability of Applicability of Weibull Weibull Theory Theory Size Effect B. Peng et al., submitted to undoped undoped J. Appl. Phys. , 2004 − i 1 / 2 exp = P f N   m   σ V     Weibull = − − P 1 exp max     f σ V     0 0   m   σ A   Weibull   = − − P 1 exp max     f σ A     0 0 Samples A B C D Length ( µ m) 400 200 200 100 Width ( µ m) 40 20 20 5 Thickness ( µ m) 1 1 0.5 1 Volume ( µ m 3 ) 16000 4000 2000 500 Total Surface Area ( µ m 2 ) 32800 8400 8200 1200 Side Wall Area ( µ m 2 ) 800 400 200 200 Micro and Nanomechanics Lab Department of Mechanical Engineering