William Daly,

Collins Hill High School, Gwinnett County, GA

Vacuum tubes ◦ 1904 – 1950’s

Metal Oxides ◦ 1940’s – 1950’s

IV and III/V Semiconductors ◦ 1950’s to present

Renewed interest in oxides ◦ Programmable devices (no 0’s & 1’s) ◦ Resemble biological systems ◦ Neuromorphic computing

S. Williams Hewlett Packard

Resistors, Capacitors, Inductors and ???

Theorized by Leon Chua in 1971

First reported by Hewlett Packard in 2008

HP Device Made in TiO2

Ohm’s Law

𝑑𝑉

𝑑𝐼= 𝑅

𝑑𝑉 = 𝑅 𝑑𝐼

Capacitance

C 𝑑𝑉

𝑑𝑡= 𝐼

C 𝑑𝑉

𝑑𝑡=𝑑𝑞

𝑑𝑡

𝑑𝑞 = 𝐶 𝑑𝑉

Inductance

𝑉 = 𝐿𝑑𝐼

𝑑𝑡

𝑑Φ

𝑑𝑡= 𝐿

𝑑𝐼

𝑑𝑡

𝑉 =𝑑Φ

𝑑𝑡

Faraday’s Law

𝑑Φ = 𝐿 𝑑𝐼

??????

𝑑Φ

𝑑𝑡

𝑞

Φ

𝑑𝑞

𝑑𝑡

𝑑Φ = 𝑀𝑑𝑞

A New Fundamental Passive Component?

𝑑𝑉 = 𝑅 𝑑𝐼 𝑑𝑞 = 𝐶 𝑑𝑉

𝑑Φ = 𝐿𝑑 𝐼

𝑑Φ

𝑑𝑡

𝑞

Φ

𝑑𝑞

𝑑𝑡

𝑑Φ = 𝑀𝑑𝑞

If M and R are just constants, they both represent resistance – not too interesting

What if R and M are non-linear? ◦ R depends on I: (varistor)

◦ M depends on q: (memristor???)

◦ Why “mem”

𝑑𝑉 = 𝑅(𝐼) 𝑑𝐼

𝑑Φ = 𝑀(𝑞)𝑑𝑞

𝑉 =𝑑Φ

𝑑𝑡 𝑂𝑅 𝑉 𝑑𝑡 = Φ

Faraday’s Law

Present Applications ◦ Lithium Ion Battery Cathodes

Projected Applications ◦ Memristor

◦ Programmable electrical characteristics

◦ Non-volatile high density memory

◦ Multilevel memory

◦ Neuronic systems

Suggests difference crystal orientations

Enhance in batteries Suppress in batteries

104

003

Present research seeks to grow LiCoO2 on Sapphire to enhance 003 for alterable electronic properties

RF Sputter Sample

Film Thickness

(Profi-lometer)

Investigation of Semiconductor and Circuit Applications of Lithiated Oxides – Process Flow

Photo- resist

Ebeam or Filament

Evap Metallize

Test Crystal Quality (XRD)

Species (Raman)

Process Pattern

Anneal I-V (DC) Z (AC)

Zo (EM)

m (VSM)

Temperature (°C)

Gas Mix

O2 / Ar (sccm)

PVD75 RF Sputtering - Process Parameter Variation

2/48 5/45 10/40

25

200

375

27 Runs @ Pumpdown to 10-5 Torr RF Power = 100W Ramp = ± 10W / min. Hold Duration = 45 minutes No rotation 5 each 1x1 cm2 Al203 per run Target = LiCoO2

PVD75 RF Sputter Sample Prep - Mounting

PVD75 RF Sputter Sample Prep – LiCoO2 Target

PVD75 RF Sputter Sample Prep – Align Sample & Gun

PVD75 RF Sputter Sample Prep – Deposit

1st Samples (3x3 floor of Parameter Variation Plan) ◦ 100W RF Power

◦ 45 minute deposition

◦ Post-annealed thickness of ~ 1000 Å

Sought greater thickness – 2 additional samples ◦ 150 W RF Power

◦ 60 minute and 120 minute depositions

◦ 3000 Å at 60 minutes

Anneal Samples In O2 For 2 Hours

Annealed from 500ºC to 900ºC, 50ºC increments

500ºC remained amorphous

900ºC yielded Co3O4

Optimal anneal from 700ºC to 750ºC

Characterization centered on 700ºC

Characterization ◦ Profile

◦ * Raman spectroscopy

◦ * XRD – rocking curve

◦ VSM (vibrating sample magnetometer)

Testing ◦ * DC I-V Characteristic

◦ Impedance spectroscopy

Electromagnetic waves interact with matter when photon energy is absorbed as ◦ Electron is removed (ionization)

◦ Electron changes increases multiple discrete levels – reemits more than one photons (fluorescence)

◦ Photon is elastically scattered (diffracted) - XRD

◦ Photon is inelastically scattered (electrons undergo partial or virtual energy state transitions) - Raman

http://fy.chalmers.se/OLDUSERS/brodin/MolecularMotions/CCl4modes.html

Vibrating molecule ◦ Results in vibrating dipole moment

◦ Assume “polarizability” a

◦ If vibrating, a(t)= a0+ ak cos wkt

Incident light, electromagnetic wave, has electric field given by E=E0 cos w0t

E induces a, results in dipole moment M=aE

M=aE is seen in spectrum of reflected light.

Inelastic - reflected photon has shifted wavelength (shifted energy) depending on which vibration

From Mk=akE0 cos(𝜔0 ±𝜔𝑘)𝑡 = A cos 2πc (1

𝜆0±

1

𝜆𝑘)𝑡

The Raman shift is 1

𝜆0−1

𝜆𝑘 (in cm-1).

That this is D energy is evident by multiplying argument by h/h.

It is the energy taken or given to the reflected photon in an inelastic collision.

It is a signature of the characteristic vibrational mode of a molecular species.

LCO 6E annealed at 900C for 15 Min

0 200 400 600 800 1000 1200 1400 16000

200

400

600

800

1000

1200

1400

1600

1800

2000

X: 164.3

Y: 655.9

LCO 6E Annealed at 900 C for 2 Hours

Inte

nsity

Raman Shift (1/cm)

X: 195.6

Y: 341

X: 576.5

Y: 1141

X: 494.5

Y: 624.6

X: 748.6

Y: 1598

X: 712

Y: 1434

X: 688.8

Y: 1317

X: 628.1

Y: 935.6

X: 416.9

Y: 1850

X: 523.4

Y: 757.7

Co3O4

Li2O

Al2O3

0 200 400 600 800 1000 1200 1400 16000

100

200

300

400

500

600

700

800

X: 747.1

Y: 680.1

LCO 5A Annealed at 700 CX: 416.9

Y: 780.2

X: 577

Y: 440.4

X: 591.9

Y: 598.4

X: 447.8

Y: 138.2

X: 481.5

Y: 218.8

Al2O3

LiCoO2

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750

Ra

ma

n i

nte

nsi

ty

200 400 600 800 1000 1200 1400

Raman shi ft (c m-1)

2.00

5.00

10.00

0

5

10

15

20

5

10

15

Oxyg

en f

low

rate

(sccm

)

FW

HM

(cm

-1)

Chamber pressure (mTorr)

Figure 14 (a): Raman Peak for LiCoO2 at 486 cm-1

Raw FWHM of Isolated Peak vs. Pressure and Gas Mix

15-20

10-15

5-10

0-5

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750

Ra

ma

n i

nte

nsit

y

200 400 600 800 1000 1200 1400

Raman shi ft (c m-1)

2.00

5.00

10.00

0

10

20

30

40

5

10

15

Oxyg

en f

low

rate

(sccm

)

FW

HM

(cm

-1)

Chamber pressure (mTorr)

Figure 14 (b): Raman Peak for LiCoO2 at 486 cm-1

Fitted FWHM of Isolated Peak vs. Pressure and Gas Mix

30-40

20-30

10-20

0-10

2.00

5.00

10.00

05

101520253035404550

5

10

15

Oxyg

en f

low

rate

(sccm

)

FW

HM

(cm

-1)

Chamber pressure (mTorr)

Figure 14 (c): Raman Peak for LiCoO2 at 596 cm-1 Fitted

FWHM of Peak Masked by Sapphire Peak vs. Pressure and

Gas Mix

45-50

40-45

35-40

30-35

25-30

20-25

15-20

10-15

5-10

0-5

◦ Presence of crystal at given orientation:

◦ Constructive interference at (l/2)/d = sin q

◦ LiCoO2 has a peak at 18.8º

◦ n l = 2d sin q . For a perfect crystal …

º º

◦ LiCoO2 has a peak at 18.8º

◦ n l = 2d sin q . For a perfect crystal …

◦ LiCoO2 has a peak at 18.8º

◦ n l = 2d sin q . For a “busted up” crystal…

2.00

5.00

10.00

0

5

5

10

15

Oxyg

en f

low

rate

(sccm

)

FW

HM

(cm

-1)

Chamber pressure (mTorr)

Figure 15: XRD FWHM of Rocking Curves at 18.8o

2.00

5.00

10.00

Sputtering – LiCoO2 growth oriented in 003 plane disfavored by (both raw and fitted Raman) ◦ Low pressure

◦ High O2 / Ar ratio

Annealing - LiCoO2 growth oriented in 003 favored ◦ by 700ºC to 750ºC

◦ 2 hour annealing is incidental

◦ Optimal time requires additional investigation

XRD ◦ Found 003 orientation corresponding to 18.8º

◦ Rocking curves obliquely support Raman

◦ Raman on small region vs. XRD across sample

◦ Sample edge suggests XRD on masked sample

Electrical testing of sample suggests thicker deposit. ◦ 1000 Å exhibits weak memristive effect

◦ 3000 Å exhibits 667 A / (V·s) memristive effect

Further study is required to correlate 003 to electrical characteristics.

http://en.wikipedia.org/wiki/File:Selenium_rectifier.agr.jpgs http://en.wikipedia.org/wiki/High-temperature_superconductivity D. B. Strukov, G. S. Snider, D. R. Stewart1 & R. S. Williams, The missing memristor

found, Nature 453, 80-83 (1 May 2008). X. W. Lou, D. Deng, J. Y. Lee, J. Feng, L. A. Archer, Self-Supported Formation of

Needlelike Co3O4 Nanotubes and Their Application as Lithium-Ion Battery Electrodes, Advanced Materials, 20, 258–262 (2008).

H.Y. Park, S.R. Lee, Y.J. Lee, B.W. Chod, W.I. Chod, Bias sputtering and characterization of LiCoO2 thin film, Materials Chemistry and Physics 93 70–78 (2005).

J. G. Grasselli and M. K. Snavely, Chemical Applications of Raman Spectroscopy, John Wiley & Sons, Inc., New York (1981).

M. Bradley, Curve Fitting in Raman and IR Spectroscopy: Basic Theory of Line Shapes and Applications, Application Note: 50733, Thermo Electron Corporation, Madison, WI

http://fy.chalmers.se/OLDUSERS/brodin/MolecularMotions/CCl4modes.html http://spectrum.ieee.org/semiconductors/design/the-mysterious-memristor

Jordan Greenlee, Mentor

Dr. Alan Doolittle, Sponsor

Dr. Leyla Conrad, Assoc. Director, Education

MIRC Staff ◦ Hang Chen

◦ Jason Herrington

◦ Gary Spinner

◦ Janet Cobb-Sullivan

Georgia Tech and the NSF for support of the Step-Up Program