David L. GriscomNaval Research Laboratory, Washington, DC (retired)

impactGlass research international, San Carlos, Sonora, México

2016 Stookey Lecture of Discovery2016 Glass and Optical Materials Division Annual Meeting, May 23, 2016

Madison, Wisconsin

[Abridged]

The Life and Unexpected Discoveriesof an Intrepid Glass Scientist

STH History: How I became an MOS guru part 1 (mistaken!)

"Diffusion of radiolytic molecular hydrogen as a mechanism for the post-irradiation buildup of interface states in SiO2-on-Si structures," D.L. Griscom, J. Appl. Phys. 58

(1985) 2524-2533.

When I finally realized my errors, I decided to write a paper that would pull together all of the most important publications bearing on the different parts of this highly complex subject and explain how they all come together.

This 1985 publication was seminal, and constructive, but it turned out to be far from correct. Nevertheless, the number of citations it has garnered to date is a phenomenal 372!

Note that MOS stands for Metal-Oxide-Semiconductor, but the metal affects nothing.

The result appears in the next slide.

Here is my Introduction:A detailed microscopic model for radiation-induced interface state formation in Si-based MOS structures has long been the holy grail of researchers in the field. The experimental data upon which such models have been founded comprise electrical measurements on capacitor and transistor structures and various forms of spectroscopy. The most structure-sensitive experimental technique has been electron spin resonance (ESR), albeit that the method is restricted to those defect states which are paramagnetic. The key to securing the grail appears to lie in refinement and integration of the ESR and electrical results.

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Before I expose my gross mistake and how the truth of the matter finally evolved, Iwant to mention the names of Nelson Saks, Dennis Brown, and Keith Brower as my sources of electrical results. Without them I could never have reached this point.

5.5 times fewer than my erroneous original.

STH History: How I became an MOS guru part 2, the plot thickens

D. L. Griscom: Hydrogen model for radiation-induced interface states in SiO2-on-Si structures: A review of the evidence, J. Electron. Mat. 21 (1992) 763-767

STH History: How I became an MOS guru part 3 (My crapy model)

Griscom, Brown, and Saks, in: The Physics and Chemistry of SiO2 and the Si-SiO2 Interface, Plenum, New York, 1988, p. 287

My 1985 Model:Initial results of Irradiation:

OH preexisting in the oxide layer is fissioned by exciton decay:

Bias-Independent hydrogen drifts toward

the interface as H2

What is an STH?

Thus, my 1988 Model Became as Follows…

STH History: How I became an MOS guru part 4 (STHs at last1)

D. L. Griscom: Hydrogen model for radiation-induced interface states in SiO2-on-Si structures: A review of the evidence, J. Electron. Mat. 21 (1992) 763-767

Initial results of Irradiation:

1 %

99 % Protons drift to the interface under

non-negative bias.

It stands for “Self Trapped Hole.” I will tell you about STHs next!

?

To the left is the most important of the three figures found in the above paper.

However, I was disappointed with my overall simulation [dashed curve in (a)] and planned to improve it. But other matters intervened

Thereafter I resolved to do furtherresearch and write up a complete paper chocked full of STH history and technical details to be ready to publish in the Riga conference proceedings.

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It clearly separates STH1 from STH2.

…that is until I received the notice at the right:

My first claim to have discovered the STHs

(a) STH1

(b) STHmixed (finally recognized)

(c) STH2

Component Simulations g-ValueDistributions

STH History: Detailed Analysis of ESR Spectrum: g Values

D.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

Weighted Sum ofthe Three Components

Now Used to Fit Experiment(Mostly STH2) But this peak

is entirely STH1

STH History: Detailed Analysis of the ESR SpectrumD.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

The yellow box identifies E′ Centers

*

*

*

*Asterisks identify features due to Peroxy Radicals

The red curve is my Physics-Based Computer Simulation of the STHs

(+ E′ Centers)

*

Here is my best spectrum of a High-PurityOxygen-Excess sample of Suprasil W

silica following X irradiation a 77 K

STH History: Detailed Analysis of ESR Spectrum: Models

D.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

STH1

STH2

Hole occupies a non-bonding 2p orbital on a single bridging oxygen.

Hole must rapidly tunnel between two equivalent bridging oxygens belonging to the same tetrahedron.

This is the expected structure for the “small polaron”.

This structure was not expected.

However, later on, my ESR discoveries were matched by ab initio calculations by others.

(a) STH1

(b) STHmixed

(c) STH2

STH History: g-Matrix Analyses: STH1D.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

STH1 Model Empirical g Value Distributions areSkew-Symmetric

But Their Corresponding

Density of StatesAre All Gaussians is the spin-orbit coupling constant for O- ion.

g1g2g3

g1g2g3

STHmixedg value offree electron

Top of Valence

Band

STH History: g-Matrix Analyses: STH2D.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

g3 g2 g1

E

σ

Empirical Result:

I derived these equations:

Much deeper in the valence band:

E

STH2 Model

Tetrahedral within experimental error!

Range II order?

This result blows my mind!!!

Density of States

Ener

gy (e

V)

Pantelides & Harrison(1979)

Upper Valence Band

Lower Valence Band

STH1 & STHmixed CalculatedSTH2

STH History: Detailed Analysis of ESR Spectrum: Density of States Derived from g-value Distributions

D.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

Here all of my skew-symmetric ESR graphs are converted to energy level Gaussians, and we are about to compare my experimental data with theory!

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STH History: ConclusionsD.L. Griscom, J. Non-Cryst. Solids 149 (1992) 137

I wrote it up. But was anyone going to believe me?8 days before this same manuscript was received

by the Journal of Non-Crystalline Solids

Material MeasuredForm Property

Fibers Optical

Bulk Glass ESR

Thin Film ESR

Thin Film Electrical Charge

1970 1980 1990 2000

Date (A.D.)

Amosov et al., Leningrad Griscom, Washington

Chernov et al., Moscow Griscom, Washington

Brower, Albuquerque

Harari et al., Princeton Saks et al., Washington

*

*

*

*

Nagasawa et al., Tokyo

Sasajima & Tanimura, Osaka

Observed Effects Unexplained STHs Explain AllMany helpers, but I was theonly one to put it all together.

4 times I appealedfor futher funding, all denied

Here is a Notable 2006 Paper of Mine that I Have Insufficient Time to Discuss

It’s Fig. 2 explains the preceding diagram in further detail.

Apropos of the military/industrial incompetence… Section 5 relates the story of how I solved the problem of AlliedSignal

ring-laser gyros suddenly failing in orbit in after just one year

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…whereas they had previously operated for 20 years in orbit!

This is a Another Notable Paper of Mine that I Have Insufficient Time to Discuss

While still at NRL I talked Bill Weber into sending me small amounts of each of his three then-17-year-old nuclear-waste-glass simulants having differing

amounts of 238Pu. I took copious ESR spectra before leaving NRL…

1006

cites

15 pages &15 figures

I think my results are well worth my trouble.

2011

But I only got around to analyzing those data until 10 years later!

But only…

Well it was pretty esoteric.

Yet a Another Notable Paper of Mine that I Have Insufficient Time to Discuss

2011

I began this undertaking with the objective of reconciling certain differences among three of the brightest materials scientists I’ve ever known.

(all from the former Soviet Union)

However,13 pages later I found myself tearing apart my own model for the role of chlorine in high-Cl silica glass upon irradiation, published by me and

Joe Friebele in Phys. Rev. B in 1986.

I’m still not certain whether or not I helped significantly in that objective.

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My bad. But better 30 years late than than not a all!

18 pages

γ irradiations carried out in the NRL pool facility.

My version of Charles Askins’ original model, which was lost during NRL’s Optical Sciences Division move to it’s new buildings.

The great advantage of this rig was that it can measure induced attenuation at times as short as 1 second, surprisingly revealing enormous bands at the start …as compared with a concomitant study in Russia, arranged by Konstatnin using monochromators, which caused his group to be unable to record the first hour or so of data.

STH History: Optical Bands (ESR Put Aside)Growth and Disappearance of 660- and 760-nm Bands in Fibers

γ and fission-reactor radiation effects on visible range transparency of aluminum-jacketed, all silica optical fibers

D.L. Griscom, J. Appl. Phys. 80 (1996) 2142-2155

My system simultaneously measured radiation-induced optical bands in four aluminum-clad silica-core fibers, three of them differing mainly in OH and Cl contents of the cores. The fourth one was made especially for me by Konstantin Golant in Russia, thanks to Hideo Hosono furnishing the F-doped core rod. This was likely NRL’s first buy from the former Soviet Union.

STH History: Optical Bands Created by γ RaysGrowth and Disappearance of 660- and 760-nm Bands in

FibersDuring Iradiation

D.L. Griscom, Appl. Phys. Lett. 71 (1997) 175 High-purity, low-OH,low-Cl, pure-silica-corefiber (KS-4V) under γ irradiation at 1.0 Gy/s

Next we’ll take a closerlook at spectrum #2.

1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.00

5000

10000

15000

In

duce

d Lo

ss (d

B/k

m)

Photon Energy (eV)

STH History: Optical Bands Created by γ Rays660- and 760-nm Bands in Optical Fibers Appear to Be Due to STH2

D.L. Griscom, Appl. Phys. Lett. 71 (1997) 175

760nm

660nm

Could thesebe STH’s?

Do you remember the red line at 2.0 eV passing horizontally through the STH2 energy peak back 7 slides ago?

So now let us now erect verticals corresponding the horizontal peaks of STHmixed and STH1.

The orange horizontals of 7 slides ago came with the caution that the eV scale was based on an unknown parameter close to 1 …so I took it to be exactly 1. So the difference between the position of the red vertical passing through 2.0 eV and the high point of my spectrum may prove to be the needed correction.

STHmixedSTH1 STH2 Photon Energy (eV)

Indu

ced

Loss

(dB

/km

) Well, here is a red line vertical to an optical spectrum also in eVs which corresponds to STH2.

Clearly STHmixed doesn’t match an optical peak.

And likely neither does STH1, given no hint a band tail.

Ergo, thisspectrum mustbe solely dueto STH2!

STH History: Optical Bands Created by γ RaysRadiation-Induced “Reconfiguration” of High-Purity a-SiO2

FibersD.L. Griscom, Appl. Phys. Lett. 71 (1997) 175

t-1

So it appears that pure-silica-core fibersare “reconfigured” by long-term, low-dose-rate irradiation in such a way that color centers (now recognized as STHs) are no longer formed, even when the irradiation continues.

Indeed, a re-irradiation 3 months later peaked where the original left off …before once again heading downward.

I have patented this.

Loss at 760 nm vs γ irradiation time at 1 Gy/s

103 104 105 106 107 108

0.01

0.1

1

10

100

1000

Classical Kinetic Solutions: Red Curves: 2nd-Order; Small Circles: 1st-Order

340 rad/s

17 rad/s

0.45 rad/s

Experimental Data:

17 rad/s

0.45 rad/s

340 rad/s

Indu

ced

Loss

(dB

/km

)

Dose (rad)

Slope = 1.0

These Data

Cannot Be Fit by These Solutions

Note Overlapping Linears

Fractal kinetics of radiation-induced point-defect formation in amorphous insulators: Application to color centers in silica-based optical fibers

D.L. Griscom, PHYSICAL REVIEW B, Vol. 64, 174201 (2001)

What to do? Well, it was about time to try fractal kinetics.

Fortunately, a Russian colleague of mine, Vladimir Mashkov, had done such a classical-to-fractal problem of this nature, so I decided to follow his lead. However, it turned out that my problem was quite different from his…

However, not a one of my many fractal-kinetics articles treated this kind of problem.

My Foray into Fractal KineticsD.L. Griscom, Physical Review B, Vol. 64, 174201

Vladimir was looking at E´ centers in bulk, low-OH silica, whereas I was primarily studying optical fibers, with Ge-doped silica cores.

Nevertheless, after a week of cut-and-try efforts I finally arrived at the following results:

IMPORTANT:In the present case (Ge-doped silica), there were dose-rate effects determined empirically, requiring modification of fractal parameters K and R.

And the Ge(1) and Ge(2) centersare as different from E´ centers as night is to day!

1000 10000 100000 10000000.1

1

10

100

C

B

0.011 rad/s=1.017 rad/s

=0.66

0.45 rad/s=0.85

340 rad/s=0.52

Indu

ced

Loss

(dB

/km

)

Dose (rad)

1th- and 2nd-Order Fractal Kinetics of Irradiated Ge-Doped Silica Fibers

D.L. Griscom, Physical Review B, Vol. 64, 174201My Final Fit for Single-Mode Fibers

A

AA

A

Solid curves “A” represent growth and thermal decay ofinduced optical of attenuation at 1300 nm in Corning SM Ge-doped silica fibers subjected to γ irradiation at the noted dose rates. These curves and the black squares were taken by Joe Friebele and his helpers.

My small-circles fitting Joe’s “A” data are derived from 2nd-order fractal-kinetic growth curves applied to Ge-doped silica glass, but including the “B” and “C” permanent damage curves, which I co-optimized by my cut-and-try procedures.

The gray arrows emphasize the unidirectional variationof β with increasingly lower dose rates.

My Foray into Fractal Kinetics: The Most Important Result

D.L. Griscom, Physical Review B, Vol. 64, 174201

1E-3 0.01 0.1 1 10 100

10

100(c)

Slope =

Slope = /2

Sat

urat

ion

Loss

(dB

/km

)

Dose Rate (rad/s)

1E-3 0.01 0.1 1 10 10010-8

10-7

10-6

10-5

10-4

10-3

Linear!!!

(b)Classical 1st-Order Kinetics

Classical 2nd-Order Kinetics

Rat

e C

oeffi

cien

t (s

-1)

1E-3 0.01 0.1 1 10 100

0.7

0.8

0.9 (a)

Stretched 2nd Order Kinetics

Stretched 1st-Order Kinetics

Pow

er-L

aw E

xpon

ent

1E-3 0.01 0.1 1 10 1001

10

100(c)

Slope =

Slope = /2

Sat

urat

ion

Loss

(dB

/km

)

Dose Rate (rad/s)

1E-3 0.01 0.1 1 10 10010-910-810-710-610-510-410-3

Linear

(b)

Rat

e C

oeffi

cien

t (s

-1)

1E-3 0.01 0.1 1 10 1000.6

0.7

0.8

0.9

1.0(a)

Pow

er-L

aw E

xpon

ent

Two different ways to normalize the results

Not much difference at all in this case

2nd-Order Fractal Kinetics 2nd-Order Fractal Kinetics

β

k

Nsat

Can BeExtrapolated!

Two different ways to normalize the results

5 ½ Orders ofMagnitude!

What an Unexpected Discovery this One Was!!!

Joe Friebele and I were co-authors of a chapter entitled “Color Centers In Glass Optical Fiber Waveguides,”

1986

which included the 3 Ge-related features to the right.

This was the first and only study of it’s kind making use of both ESR and Opticalmethods from 77 K to ~1000 K and a Bulk sample instead of an Optical fiber.

Ge(1)

Ge(2)

GLPC

ESR: Trapped Electrons

Optical:Ge-LonePair Center

And 26 years later I realized that the story of irradiation effects in Ge-doped silica glasses was far from understood. But Joe and I had both lost our notes, so I had to start over from scratch…

Joe’s optical spectrawere impeccable. So no problem here.

The big problem was the center one.

Single Hole STHs Note the generic

name OHC ca. 1986

Note that by 1992 theybecome Self Trapped Holes

The ESR-silent GLPCs rise at 50% of the combined electrons’ diving.Ergo, the GLPCs are trapping electrons in pairs!

Ge(2)

Ge(1) & Ge(2), both trapped electrons, are diving↓

What I had failed to notice were the consequences of the STHs trapping holes in pairs.

STHs

← Over here normal STHs that trap single holes have disappeared below 200 K, whereas the real action is from 200 to 380 K. Thus, if each STH were to trap a second hole (making it ESR-silent) theymay exactly balance the electron pairs of the GLPCs!

Then, bothwould followthe greenarrow!!!

View of a portion of the crystal structure of quartz looking down a c-axis channel. The central circles 1, 2, and 3 are normal silicons.

This one is “Crystal-like" because itfollows α quartzsymmetry.

These can be called “Glass-like”

“The dynamic interchange and relationship between germanium centers in α quartz”Isoya, Weil & Claridge, J. Chem. Physics(11), 4876-4884 (1987)

Now supposethat this Si2+ is replaced bya Ge2+ …

In that event, Isoya et al. have proven that an electron trapped at a site occupied by a Ge2+ has two different options:

(1) Be trapped in a p orbital parallelto the ɑ1 axis denoted II1 or…(2) one of the two I1 orbitals.

These can be called “Glass-like”All other noted details in black pertain to any Ge2+ that may take the place of a normal Si2+.

(a) Quartz (b) GeO2-SiO2 Glass

Ground States

Ge(II)

Ge(1)

Ge(I) Ge(2)

As proven by John Weil and coworkers

As proven by me

Ge-Doped α Quartz Ge-Doped Silica Glass

Doubly Degenerate Energy Wells

Conclusion: The Ge(1, 2) defects in Ge-doped silica glass are two energeticallydifferent configurations of the same defect, as proven to be true

for the Ge(I, II) centers in α quartz …only with their ground states reversed.

Glass-Like

Quartz-Like

My master paper on the natures of radiation-induced point defects in Ge2-SiO2 glasses

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