Introduction Definition General characteristics Brief history Fabrication 1
Introduction
Definition
General characteristics
Brief history
Fabrication
1
Solution-processed TFT
Applications of chalcogenide materials
under developmentcommercialized
Optical memory
TE generation
X-ray digital imaging
Optical fiber
Solar cell
FIC Thin film battery
Thin film switching device
(chalcogenide)
Flexible sensorChemical sensor
PRAMIT
Energy
IR optics
2
absorption @500~600nm
ionic conduction of Li [S/cm]
Processing temp (C)
bandgap (eV)
mobility (cm 2/Vs)
resistivity (Wcm )
insulator1018
conductor
10-1 10-81010 103 >10-1
103 105
(CdTe, CuInGaSe 2)
a-Sic-Si
1.81.0 a-Sic-Si0.5 0.7
LiPON, LiBPO
10-2
Liquid electrolyteChalcogenide
10-310-410-510-6
Polymer gel electrolyte
300 250 150200
PA_Tg: 330 PES_T g: 228 PC_Tg: 150PI_Tg: 385
500 450 350400
crystalline Si
1400~600
a-Si
0.1~1
ZnO
20~30
(Ge2Sb2Te5, ZnSe , CdTe)
TE coeff. (mV/K) Pb
4.0
(n-Bi2Te3, p-BiSbTe 3, Pb15Ge37Se58)
230
Ca3Co4O9
440Si
memory / switch
solar cell
thin film battery
flexible device
TFT
TE device
ChalcogenideChalcogenide(PbTe, Ge 2Sb2Te5)
ChalcogenideChalcogenide
(Ge2Sb2Te5, CuInSe 2, CuInGaSe 2, CdTe , CuGaSe 2)ChalcogenideChalcogenide
ChalcogenideChalcogenide
Chalcogenide
(SnS(Se ), n-Ge2Sb2Te5)
ChalcogenideChalcogenide
Characteristics of chalcogenide materials
3
“Chalcogenides are chameleon compounds: they can
be crystalline or amorphous, metallic or
semiconducting, and conductors of ions or electrons.”
“Thus, a unified approach to the study of
chalcogenides, assessing the roles of atoms, ions and
electrons, may prove crucial for both device
performance and reliability.”4
Chalcogenide glass?
5
Glass consisting of the Group VI elements (S, Se, Te), as major
constituents, and others (usually Group IV and/or V elements)
Covalent amorphous solids
The chemical bond nature of inorganic glasses
Ionic bond: fluoride and halide glasses
Covalent bond: chalcogenide glasses (S-, Se-, or Te-based)
Metallic bond: amorphous metals
Mixed (ionic + covalent) bond: oxide glasses
Relatively strong covalent bonds in ChG
Semiconducting but can’t be doped: the empirical 8-N rule
Presence of the homopolar bonds
Similar electronegativity of constituent atoms
Relatively well-defined intermediate range order
Presence of (various kinds of) electronic defects
6
Good transmittance in the infrared region (~20 mm) IR optical devices
Low phonon energy (~200 cm-1 for selenide glass) Host for ion-doped laser and amplifier
High c(3) optical nonlinearity (~103 higher than a-SiO2) Ultrafast all optical switching for optical communications
Semiconducting Photocopying machines, digital x-ray imaging, PCM
Fast ion conducting Thin film battery, ionics devices
Photo-induced phenomena Photolithography, Optical waveguide
Some characteristics of chalcogenide glasses
7
Classification
Amorphous covalent solid
Glassy semiconductor
Lone-pair semiconductor
Strong covalent glass
Obeying the 8-N rule
Ge, Si, As, Sb…
Electronic conductor
Weak covalent glass
Violating the 8-N rule
Ga, In, Na, Ag…
Ionic conductor
Bulk or film?* Figure taken from K. Tanaka, Optoelectronic Mater. Devices 1 (2004) 43.
8
9
165 164 163 162 1612000
4000
6000
8000
10000
S2p84 % AsS
3/2
16 % within S-S
Counts
Binding energy (eV)
Bulk As2S3
45 44 43 42 410
1000
2000
3000
4000
5000
6000
7000
As 3d
As-As
AsS3/2
Co
un
ts
Binding energy (eV)
165 164 163 162 161 1600
3000
6000
9000
12000
15000
18000
21000As
2S
3 bulk
S 2p core levelC
ou
nts
Binding energy, eV
Freshly deposited As2S3 film
46 45 44 43 42 410
2000
4000
6000
8000
10000
12000
14000 As2S
3 bulk
As3d core level
Cou
nts
Binding energy, eV
Surface of fresh cut of glass vs freshly deposited thin film
* Slide provided by Dr A. Kovalskiy
Chemical bonds
* K. Tanaka, Optoelectronic Mater. Devices 1 (2004) 43. 10
Brief history The earliest experimental data on an oxygen-free glass have been published
by Schulz-Sellack in 1870 [1].
Later on, Wood in 1902 [2], as well as Meier in 1910 [3] carried out the first
researches on the optical properties of vitreous selenium.
In 1950, Frerichs [4] published the paper: “New optical glasses transparent in
infrared up to 12 mm”
Glaze and co-workers [5] developed in 1957 the first method for the
preparation of the glass at the industrial scale.
Winter-Klein [6] published reports on numerous chalcogenides prepared in the
vitreous state.
A research group lead by Kolomiets and Goriunova discovered the first
semiconducting glass, TlAsSe2 [7].
In 1968, Ovshinsky [8] discovered the memory and switching effects of some
chalcogenide glasses.
1. C. Shultz-Sellack, Ann. Phys. 139, 182 (1870).
2. R. W. Wood, Phil. Mag. 3, 607 (1902).
3. W. Meier, Ann. Phys. 31, 1017 (1910).
4. R. Frerichs, Phys. Rev. 78, 643 (1950).
5. F. W. Glaze, D. H. Blackburn, J. S. Osmalov, D. Hubbard, M. H. Black, J. Res. Nat. Bur. Standards 59, 83 (1957).
6. A. Winter-Klein, Verres et Refractaires 9, 147 (1955).
7. N. A. Goriunova, B. T. Kolomiets, Zhurnal Tekhnicheskoi Fiziki (Russ.) 25, 2069 (1955).
8. S. R. Ovshinsky, Phys. Rev. Lett. 21, 1450 (1968) 11
12
The material used: amorphous AsSiGeTe
13
Fabrication
Melt-quenching
* Feltz book, p. 16.* Photo provided by D. Zhao
14
Low-temp. wet process
Solution process
15
Low-temp. wet process
Sol-gel
* Feltz book, p. 19.
16
PVD (Evaporation)
Thermal and/or e-beam
* Feltz book, p. 22.
17
PVD (Sputtering)
DC or RF magnetron
* Feltz book, p. 25.
18
PVD (PLD)
Laser ablation
19
Mechanical milling
20