Zincite Properties. Growth methods. Applications. ZnO Kortunova E.V., Dubovskiy A.B., Filippov I.M., Kaurova I.A. - Mineral Ltd. 1, Institutskaya st., Alexandrov, Vladimir Region , Russia

Applications of ZnO crystals High quality crystal substrates Luminescence devices Electronic components Piezoelectronic devices Acoustoelectronics for ZnO heteroepitaxy for optical waveguides Phosphor scintillators 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 – Wurtzite Hexagonal syngony Space group P6 3 mc Lattice parameters : а=3,2495 А, с=5,2069 А

Density – 5,64 ± 0,01 g /cm 3 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 · Om·cm Mobility of carriers –180 cm 2 /V · s ZnO main properties

Elastic constant с ,718 GPa; s TPa -1 с ,14 GPa; s TPa -1 с ,13 GPa; s TPa -1 с ,941 GPa; s TPa -1 с ,449 GPa; s TPa -1 с ,289 GPa; s TPa -1 Permittivity  11 s /  0 – 8.33  33 s /  0 – 8.8  11 t /  0 – 9.26  33 t /  0 – 11.0 Piezomodule d * Cl/N; d ,2* Cl/N; d ,6* Cl/N Optical parameters Refraction index wave-length, mkm n 0 n e 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 PbF 2 melt. Grower diagram mm/day mole %

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(NH 4 OH) Seeds: ZnO monoherdal or prism orientation Size ~ 80 mm Cycle duration ~ 180 days Working temperature ~ ºС Pressure ~ 500 atm. Temperature gradient between growth and dissolution chambers 8-15 ºС. Thickness of crystals mm

Hydrothermal synthesis

Dependency of zinc solubility from temperature Hydrothermal method Dependency of zinc solubility from KOH and NaOH concentration 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/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 photoluminescence Laser 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.