Intermediate Phases in Chalcogenide Glasses
B. Intermediate Phases in Oxide Glasses
C. Rigidity Transitions in Chalcohalide Glasses
Discovery of Intermediate Phases1,2,3,4
in network or molecular glasses has opened a novel
paradigm to understand the physical behavior of glasses at a basic
level. These phases manifest as global connectivity of molecular
networks are systematically changed, and acquire a critical value.
These ideas have led to a glass structure based classification5,6,7
in terms of their elastic properties, Floppy-intermediate-stressed rigid. Intermediate Phases are
non-mean-field phases, and represent stress-free
or self-organized phases of disordered systems. Their
physical behavior are examined in controlled laboratory experiments
in molecular glasses.
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No aging in glasses.
This work is supported by National Science
Foundation grants DMR-01-01808 and INT-0138707 with
France under an NSF-CNRS collaboration.
1. D.Selvanathan, W.J.Bresser, P.Boolchand, B.Goodman. Solid State Commun.111,619(1999) (article in
2. D.Selvanathan, W.J.Bresser and P.Boolchand. Phys.Rev B61,15061(2000) (article in
3. P.Boolchand, D.G.Georgiev, B.Goodman.
J.Optoelectronics and Adv. Materials 3,703(2001) (article in
4. Y. Wang, J.Wells, D.G.Georgiev, P.Boolchand, K.Jackson, M.Micoulaut. Phys.Rev.Lett.87,185503(2001)(article
in pdf format) .
5. M.Micoulaut ( unpublished)
6. J.C.Phillips, Phys. Rev. Letters
88, 216401 (2002).
7. M.F.Thorpe, D.J.Jacobs,
M.V.Chubynsky, J.C.Phillips. J.Non-Cryst. Solids 266-269,859(2000)
(article in pdf
Ag as an additive in Chalcogenide Glasses
New Glass Phases of Solid Electrolytes
Ionic-Conduction in Solid Electrolyte Glasses
Ag as an additive in Chalcogenide glasses has attracted
widespread interest1,2 in optical recording and information
storage technologies. Ag as a chemical additive plays a dual role3;
in Se-rich glasses it macroscopically phase separates into a Ag-rich
glass phase, and in Se deficient glasses becomes a network former to
replace Ge in select local environments. The Ag-rich glass phase is
thought to be a solid electrolyte4 with a stoichiometry
close to Ag2Se, and is characterized by a glass transition
of 230˚C. An equally important consequence of Ag addition to oxide and
chalcogenide base glasses is the several orders of magnitude
enhancement of electrical conductivity5,6 of the alloyed
glasses. Several models5 have been proposed to understand
the conductivity enhancement. Central to the problem are aspects of
glass structure, in particular the distribution of Ag in these
materials, issues that continue to be debated at present.
This work is supported by Arizona State University
on a subcontract from Axon Technologies Inc.
1. H.Fritzsche. Philos. Mag. B 68, 561(1993).
2. M.Mitkova in
Insulating and Semiconducting
Glasses, Ed. P.Boolchand, World Scientific Press, Inc., p.653.
3. M.Mitkova, Yu Wang, P.Boolchand, Phys.Rev. Lett. 83,
3848(1999) (article in pdf
4. P.Boolchand and W.J.Bresser, Nature 410,1070(2001) (article in
5. J.Kincs and S.W.Martin Phys. Rev. Lett. 76, 70(1996) (article in
6. J.Swenson, R.L.McGreevy, R.Borjesson, J.D.Wicks,
W.S.Howells, J.Phys. Cond. Matter, 8,3545(1996).
Additives In Chalcogenide Glasses and Crystalline Oxides
Chemical Aspects of Alloying
Light-Induced and Emission Effects
additives in Chalcogenide glasses have attracted widespread interest
as optical amplifiers, lasers, mid-IR photonic materials because of
the high refractive index and mid IR transparency1. Most
rare-earth ions in solids stabilize in the trivalent state, although
exceptions can occur for Eu (divalent) and Ce(tetravalent). For these
reasons trivalent Ga as an additive in the chalcogenide glasses has
been extensively studied2,3. Although Rare-earth ions can
replace Ga sites in such glasses, this does not necessarily have to be
the case. In some cases, Rare-earth ions can also occupy distorted
rocksalt environment, as is found for the case of Rare-earth
monosulfides such as LaS 4. Some of these Ga-alloyed
Chalcogenides display pronounced photobleaching effects5,
whose molecular origin remains open for debate. An issue of continuing
interest is the role of host Photoluminescence excitation on light
emission efficiency from rare-earth emitter guests1. Eu
chemical environment in BAM Phosphor is elucidated by Mossbauer
This research work
is performed in collaboration with Professor Marc Cahay.
1. S.G.Bishop, D.A.Turnbull,
B.G.Aitken, J.Non Cryst. Solids 266-269,876(2000).
2. M.Yamane and Y.Asahara, Glasses for
Photonics, Cambridge University Press,,2000.
3. Liuchun Cai and P.Boolchand (
4. P.Boolchand in
Insulating and Semiconducting Glasses,
Ed. P.Boolchand, World Scientific Press, Inc., Singapore, 2000,
5. S.H.Messaddeq, M.Siu Li, D.Lezal,
Y.Messaddeq, S.J.L.Riberio, L.F.C.Oliveira, J.M.D.A.Rollo,
J. Optoelectronics and Adv. Mater. 3,295(2001).
6. M.Stephan, P.C.Schmidt, R,C,Mishra, M.Raukao,
A.Ellens, P.Boolchand. Z.Phys.Chem, 215, 1347 (2001).
The work on BAM is supported by
- Negative Electron Affinities,
New Cold Cathode and Organic Light Emitting Diodes
A. LaS based trilayered Structure
Rare-earth monosulphides, such as LaS and NdS, are
unusual metals as they possess low work-functions1. These
materials in conjunction with III-V or II-VI semiconductors and
separately with light emitting polymers2, can be used as
efficient cold cathode emitters3,4 and light emitting
devices5. An effort to synthesize bulk materials of the
rare-earth sulfides, and grow thin-films of the rare-earth sulfides by
sputtering and evaporation is made, to fabricate new solid state cold
cathode emitters and efficient and durable organic light emitting
diodes ( OLEDS).
Current research efforts are directed towards growth of
thin-films of various rare-earth sulfides on compound semiconductors
by RF magnetron sputtering deposition6,7.
This research in collaboration with
Cahay, is funded by National Science
Foundation grant ECS – 9906053, and Wright-Patterson AFB
under contract No. F33615-98-C-1204.
J.Willis, P.D.Mumford, M.Cahay and W.Eriz, Phys.Rev.B 57,4067(1998).
M.Cahay, J.Willis, Phys.Rev.B65, 033304(2002).
and M.Cahay, J.Appl.Phys.79,2176(1996).
4. P.D.Mumford and M.Cahay,
5. M.Lueck, P.Draviam and M.Cahay (
6. Y.Modukuru, J.Thachery, H.Tang,
A.Malhotra, M.Cahay and P.Boolchand, J.Vac. Sci. and Tech.B
7. Y.Modukuru, J.Thachery, M.Cahay,
P.Boolchand, Proceedings of the Second Intl. Symposium on Cold
Cathodes, May 12-17(2002)
- Synthesis and Nanostructure of
Super Hard Thin-Films
Films in the B-N-C ternary are of interest because of
their super hardness. The ternary encompasses some of the hardest
crystalline materials known including diamond, BN, B2C. A
collaborative effort to synthesize and characterize nanostructure of
vapor deposited thin-films is ongoing with Professor Raj Singh
(Materials Science and Engineering, University of Cincinnati) and
with Professor Hans-Joachim Kleebe (Colorado School of Mines).
At the core of the research effort is an ECR microwave plasma enhanced
CVD facility1(Professor R.Singh) for growth of the ternary
alloy films. The films are characterized2 by x-ray
diffraction, and Raman scattering (Professor P.Boolchand) and
Electron microscopy3 including HRTEM, SEM and EELS
(Professor H.-J.Kleebe). The mechanical properties of these films
including Hardness, Elastic Moduli, and thermal conductivity
(Professor Singh) are measured. Constraint counting algorithms along with aspects
of nanostructure are used to understand their physical behavior
The project is funded by the
National Science Foundation as a Focused Research
Group grant DMR-0200839 and a NIRT grant 0210351.
1. R.N. Singh Proc. Xth International Conf. On CVD,
Ed. G.W.Cullen, The Electrochemical Society V.87-8,543(1987).
2. P.Boolchand, M.Zhang, B.Goodman Phys. Rev B, 53,11188(1996) (article in
3. H.J Kleebe, Phys. Stat. Sol. (A)