Data on the paramagnetic and optical properties of defects in crystals were reviewed, and a first attempt was made to obtain a comprehensive summary (tables 2 and 3) of known defects in this oxide. The defects were classified into defects in cation and anion sub-lattices, proper and impurity defects, growth defects and radiation-induced defects and point or complex defects. It was suggested that V-type defects were hole-trapped centers that were based upon cation vacancies. They were formed during crystal growth or neutron irradiation. Further differences were revealed by annealing. In some cases, thermo-activated hole delocalization took while, in others, there was an annihilation of interstitial-vacancy cation pairs. It was also concluded that the impurity defect B2+, Al2+ and Zn+ centers were substitutional ions, on cation sites, which trapped an electron during X-irradiation. The [Li]o center had a different structure, in that the hole was trapped by the O ions nearest to the Li impurity. No impurity centers were found on the anion sub-lattice.
I.N.Antsigin, A.V.Kruzhalov: Radiation Effects and Defects in Solids, 1995, 134, 303-5
Table 2
Characteristics of Lattice Defects in BeO
Defect Electron Spin Resonance Parameters Conditions
|
|
V- = Vch+ isotropic, g = 2.0117 300K, X-band |
|
Vo = Vc2h+ gxx = 2.0107, gvv = 2.0154, gzz = 2.0075 10K, X-band |
S = 1, D = -103.7mT, E = -20mT |
|
VB = Vch+-B3+ I - ‘axial’: g|| = 2.0026, g = 2.0155 300K, X-band |
II - ‘non-axial’: g|| = 2.0026, g = 2.0164 |
|
[Li]o = Li+h+ g|| = 2.0023, g = 2.0153 300K, X-band |
HFS: 7Li (I = 3/2; 92.6%) |
A|| = 1.37, A =9.5MHz |
|
B2+ = B3+e- g|| = 2.0035, g = 2.0044 300K, X-band |
HFS: 11B (I = 3/2; 80.4%) |
A|| = 343, A = 214.6MHz |
|
|
B2+ = B3+e- octahedral interstitial site 77K, X-band |
= 2.0023, g = 2.0028 |
HFS: 11B (I = 3/2; 80.4%) |
A|| = 821, A = 714.8MHz |
|
Al2+ = Al3+e- g|| = 2.003, g = 2.004 300K, X-band |
HFS: 27Al (I = 5/2; 100%) |
A|| = 583.1, A = 495MHz |
F = Va2e- ground state, S = 0 |
|
P- = VaVce- isotropic, g = 2.0026 300K, X-band |
sHFS: 3* 9Be (I = 3/2, 100%) |
A|| = 25.2MHz |
|
V-type complex |
I isotropic, g = 2.0150 300K. X-band |
II not found |
III isotropic, g = 2.0096
|
Table 3
Creation and Annihilation Conditions for Defects in BeO
Defect Creation, Optical Properties Annihilation
|
|
V- growth, neutron irradiation (adsorption: 4.0eV, 2.1eV) V- Vc + h+, 620K |
|
Vo growth, neutron irradiation Vo V- + h+, 550K |
|
VB growth, X-irradiation (adsorption: 3.85eV, 2.1eV) VB VB- + h+, 680K |
|
[Li]o growth, X-irradiation (adsorption: 3.65eV, 2.1eV) [Li]o Li+ + h+, 450K |
|
B2+ growth, X-irradiation Bi2+ Bi3+ + e-, >90K |
|
Al2+ growth, X-irradiation Al2+ Al3+ + e-, 580K |
|
Zn+ growth, X-irradiation Zn+ Zn2+ + e-, 310K |
|
F+ neutron irradiation (adsorption: 5.4eV) >900K |
(luminescence: 3.9eV [5.4eV]) |
|
F neutron irradiation (adsorption: 6.6eV) >900K |
(luminescence: 5.0eV, 3.4eV [6.0eV]) |
|
P- neutron irradiation, annealing, 700K ionic processes, >900K |
|
type-I neutron irradiation (luminescence: 1.97eV [3.5eV]) >650K |
|
type-II neutron irradiation, annealing, 400-650K >800K |
(adsorption: 4.05eV, luminescence: 2.12eV [4.2eV]) |
|
type-III neutron irradiation, annealing, 700-1100K >1100K |
(luminescence: 2.03eV [3.8eV, 4.7eV])
|