ZinciteProperties. Growth

methods. Applications.

ZnO

Kortunova E.V., Dubovskiy A.B., Filippov I.M., Kaurova I.A.

- Mineral Ltd.

1, Institutskaya st., Alexandrov, Vladimir Region 601650, Russia

Applications of ZnO crystals

High quality crystal substrates

Luminescence devices

Electronic components

Piezoelectronic devices

Acoustoelectronics

for ZnO heteroepitaxy

for optical waveguides

Phosphorscintillators

Light emitting diodes and semiconductor lasers for UV spectrum

Varistors

High-temperature diodes, transistors Ultraviolet photoconverters

Ultrasonic emitters, receivers

Piezoelectric transducers

Piezoresonance components

Discrete SAW-components, convolvers

Surface acoustic wave filters and resonators

Radiofrequency markers

ZnO structure

(11-20) projection (0001) projection

Structural prototype – WurtziteHexagonal syngony

Space group P63mc

Lattice parameters :а=3,2495 А, с=5,2069 А

Density – 5,64 ± 0,01 g /cm3

Melting point – 1975 °С

Temperature of phase transition – 1870°С

Thermal conductivity – 49,1 W/m · К

Hardness – 4 (by Mohs scale)

Width of district zone (bandgap) – 3.44 eV

Specific resistivity – 0,1..1 · 1013 Om·cm

Mobility of carriers –180 cm2/V · s

ZnO main properties

Elastic constant

с11 - 209,718 GPa; s11 - 7.858 TPa-1

с12 - 121,14 GPa; s12 - -3.432 TPa-1

с13 - 105,13 GPa; s13 - -2.206 TPa-1

с33 - 210,941 GPa; s33 - 6.94 TPa-1

с44 - 42,449 GPa; s44 - 23.57 TPa-1

с66 - 44,289 GPa; s66 - 22.58 TPa-1

Permittivity

11s/0 – 8.33 33

s/0 – 8.8 11

t/0 – 9.26 33t/0 – 11.0

Piezomodule

d15 - -13.9*10-12 Cl/N; d31 - -5,2*10-12 Cl/N; d33 - 10,6*10-12 Cl/N

Optical parameters

Refraction index wave-length, mkm n0 ne

0,45 2,105 2,123 0,5 2,051 2,068 0,8 1,959 1,975 1,4 1,9298 1,943 1,8 1,923 1,937 2,6 1,913 1,927 3,4 1,902 1,916 4,0 1,889 1,907

Growth methods of ZnO

Growth from solution in

melt

Growth by hydrothermal

method

Growth from gas phase

Growing ZnO single crystals from solution in melt

Solubility of ZnO in PbF2 melt. Grower diagram

mm/daymole %

Growing ZnO single crystals by gas-transporting reactions method

Hydrothermal method to obtain ZnO single crystals of large size

1. body of autoclave,2. lining,3. insert, 4. insert cover, 5. frame for seed

suspension, 6. charge, 7. baffle, 8. thermocouple, 9. steel sealing ring, 10. hole in steel ring,11. steel ring, 12. flange,13. flange, 14. obturator, 15. bolt, 16. nut.

• Working solution: mixture

4М(КОН) + 1М(LiOH) + 0.1M(NH4OH)

• Seeds: ZnO monoherdal or prism

orientation

• Size ~ 80 mm

• Cycle duration ~ 180 days

• Working temperature ~ 300-350 ºС

• Pressure ~ 500 atm.

• Temperature gradient between growth

and dissolution chambers 8-15 ºС.

• Thickness of crystals 25-30 mm

Hydrothermal synthesis

12

3

4

5

6

7

9

10

11

Schematic drawing of hydrothermal growth system.

1. Pressure metering system; 2. channel for thermocouples; 3. autoclave lid; 4. autoclave; 5. liner; 6.container with frames ; 7. internal baffle;8. basket with the nutrient; 9. heaters of crystallization zone;10. external heater of dissolution zone; 10. internal heater of dissolution zone.

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Zinc oxide crystals grown in an industrialautoclave.а) the smallest frame of container;b) single crystal ZnO.

The growth rate of (0001) –0.05 - 0.11 mm/day.

The growth rate of (10-10) –0.02 – 0.05 mm/day.

а)

b)

Results of experiment

Dependency of zinc solubility from temperature

Hydrothermal methodDependency of zinc solubility

from KOH and NaOH concentration

mass %mass %

mass %

Dependency of growth rate of positive monohedron from temperature

Hydrothermal synthesis

1 – at temperature gradient 75 ºС

2 – at temperature gradient 50ºС

1 – according to calculation data

2 – according to experimental data

mm/daymm/day

Dependency of face (0001) growth rate from temperature gradient ∆Т at different concentration of LiOH

Hydrothermal synthesis

1 - without LiOH

2 – 1.0М LiOH

3 – 2.0М LiOH

4 – 3.0 М LiOH

mm/day

Electrophysical parameters

Transmission range Spectrum of photoluminescenceLaser excitation 325,0 nm, 3,5 mW

Conclusions:1. Provided optimal conditions for hydrothermal growth it is

possible to obtain high-quality ZnO single crystals. Furthermore, big size crystals (over 50 mm) can be grown while the main problem is absence of large seed material.

2. Hydrothermal technology allows to dope zinc oxide crystals with required admixtures.

3. On the basis of homogenious high-quality ZnO single crystals it is possible to design fast scintillators, effective high-frequency piezotransducers, acoustoelectronic devices, high-temperature sensors, elements of power high-temperature electronics. However, the major application of ZnO crystals will be the use as substrates for ZnO homoepitaxy to create optoelectronic devices.