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