1 RADIATION DEFECTS AND OXIDATION STATE OF nl- IONS IN NON-STOICHIOMETRICAL OXIDES Nicolay A. Kulagin Kharkiv National University for Radio Electronics, av. Shakespeare 6-48, Kharkiv 61045, Ukraine. Szczecin May,

2 Outline of the talk - Radiation stimulated by X rays, gamma, electrons and particles charges transfer in oxides : sapphire, garnets, perovskites; - Optical absorption, luminescence, EPR and TSL-TSC spectra of irradiative oxides doped with nd- and nf- ions; - X Ray spectra and oxidation state of component and doped nl- ions; - Ab initio energy calculations for doped and radiation clusters and unit defects; - Electronic state stability of doped nl- ions under radiation of oxides; - Change of oxides surface under plasma treatment: quasi- ordered nano-scale structures; - Shot summary

4 Growth and Treatment The main methods of crystallization of the oxide single crystals Czochralsky - Cz; Verneuil - V; Method of horizontal and vertical crystallization - DC; Stepanov – S, etc. Mixtures of different quality and different concentration - C of accidental impurities were used for oxides crystals growth: * super- pure (C <10 -5 wt %), * pure (C <10 -3 wt %), and * standard one ((C <10 -2 wt %) Thermal treatments and co-doping by Ca, Mg O 2, 1200 <T <1800 K; CO 2, 1500 <T <1800 K; vacuum, Torr, 1500 <T <1900 K;

5 Pure Sapphire – Al2O3 Optical absorption of sapphire grown by different methods

6 TABLE. Spectral parameters of the sapphire grown by different techniques SampleAbs.edge nm Optical Bands, nm AA bands nm TL, nm TSC peaks T, K TL bands nm V195206*, 225*, 260*, 400* , 225, 280, , VpVp , 206, 230, 400* 206, 225, 280, 475* 4385, , V sp *,206*, 230*No AA0.1430, 507* , DC145175, 206* 235* 206, 230no TL398*, 507*- DC r , 206, , *, 470* 8373, 506, , Cz r *, , , , , 690 CrCr , 225*No AAno TL387*, 426* 485* ---- SrSr , , ,418, 430, 506* Pure Sapphire – Al2O3

7 Ruby – Radiation Effect Optical absorption of ruby: Al2O3:Cr

8 Structure and Defects Simplified garnet structure

9 Pure Garnet Optical absorption of pure YAG crystals grown by Chochralsky – 1 and HDC – methods

10 Optics of Y 3 Al 5 O 12 :Nd:Cr Garnets – Radiation Effect Optical absorption of YAG before and after irradiation

11 TSL – TSC spectra for YAG pure and doped with Cr:Nd

12 ESR of Cr +3 ion in Garnet EPR spectra of Cr*3 ions in YAG crystals

13 Optics of GSGG and GSAG Garnets doped with Cr and Ca OAS of doped garnets before and after thermal treatment

14 Optics of YAG:V +3 – Thermal Treatment OAS spectra of V*3 ions in YAG crystals

15 Theoretical Results - Cr +3: [O -2 ] 6 Cluster under Pressure Table 2. Theoretical values of radial integrals for Cr +3 ions in Cr +3 :[O -2 ] 6 clusters for different R IntegralFree ion / R = Configuration 3d 3 F 2 (3d,3d), cm F 4 (3d,3d), cm  (3d), cm (3d|r|3d ), a.u

16 Theoretical Results - Cr +3: [O -2 ] 6 Cluster, Ruby and YAG R Cr-O (Å)\ Level 2E2E 2T12T1 4T24T2 2T22T2 4 T 1 (t 2 2 e) 4 T 1 (t 2 e 2 ) Theory R = 2.0 Å Ruby Experiment Semiempirical Table1. Dependence of Cr +3 ions energy levels on R Cr-O (cm -1 )

17 Theoretical Results - Cr +3: [O -2 ] 6 Table 3. Semiempirical and theoretical data for B, C and Dq for Cr +3 ions in different crystals (cm-1) Integral  -Al 2 O 3 Y 3 Al 5 O 12 Gd 3 Sc 5 O 12 Gd 3 Sc 2 Ga 3 O 12 Cr +3 :[O -2 ] 6 B C Dq

18 Theoretical Results - 3d 2 configuration of Cr +4: [O -2 ] 6 2S+1 Γ(t,e) – levelEnergy, cm -12S+1 Γ(t,e)- levelEnergy,cm -1 3 T 1 (t 2 2 ) 0 1 T 2 (t 2 e) E(t 2 2 ) A 2 (e 2 ) T 2 (t 2 2 ) T 1 (t 2 e) T 2 (t 2 e) E(e 2 ) A 1 (t 2 2 ) A 1 (e 2 ) T 1 (t 2 e) Table 4. Theoretical level scheme for ion Cr +4 in ruby (Dq = 1990 cm -1, B = 1050 cm -1 and C = 3873 cm -1 )

19 Optics of Garnets – Cr +4 Energy Levels Schemes TABLE 10. Energy levels of Cr 4+ :[O 2- ] 4 cluster Y 3 Al 5 O 12 Gd 3 Sc 2 Ga 3 O 12 2S+1 Γ λ theor, nm λ exp, nm λ theor, nm λ exp, nm 3 A E T T A T T T

20 Perovskites – ABO 3 LiNbO 3 :Cr -> A - Li +, B – Nb +5 YAlO 3 :Cr/Nd -> A – Y +3, B – Al +3 SrTiO 3 :V, Mn, Fe, Co, Ni / Pr, Nd, Sm, Tm A – Sr +2 (RE +2, +3 ), B – Ti +4 (Me +2, +3, +4 ) Simplified structure of perovskite

21 Perovskite - YAlO3:Cr:Nd OAS spectra of Cr*3 ions in YAlO 3 crystals

22 Perovskite SrTiO 3 Optical Absorption Optical absorption of SrTiO 3 crystals. Pure (1) and blue sample (2) – a, crystals doped with RE – b (1 - Sm, 2 – Pr, 3 – Nd, 4 – Tm)

23 Dielecrical Properties of SrTiO 3

24 Dielecrical Properties of SrTiO3

25 Structure and Defects in SrTiO3 Energy zones of a wide – band gap crystal with different transitions and local levels

26 X Ray Lines of nl N Ions X Ray lines: K α 1 : 1s 1/2 2p 3/2 transition n’l -1 nl N - L α 1 : 2p 3/2 3d 5/2 transition configurations nl- level nl J - spin-orbit level 3d d 5/2 ============= d 3/ p 3/2 2p ============= p 1/2 1s ============= ============= 1s 1/2

27 X Ray Microanalysor

28 CrK α - Line Valency Shift for Irradiated Ruby and Garnet

29 Perovskite SrTiO 3 X Ray

30 Energy of X Ray of RE and AC ions REE (K  1 )E(K  1 )E(L  1 ) Nd , , ,471 Nd , , ,708 Nd , , ,449 Eu , , ,357 Eu , , ,793 Eu , , ,622 Gd , , ,622 Gd , , ,971 Gd , , ,614 Yb , , ,563 Yb , , ,668 Yb , , ,100 U , , ,793 U , , ,528 U , , ,200 Np , , ,953 Np , , ,674 Np , , ,346

31 K  1 - line L  1 - line Ion E 0 a-b E 0 a -b Ac ,7890, Th ,5420, Pa ,5650, U ,8680, Np ,4810, Pu100738,5420,6910, ,3560, Am103210,6480,7240, ,2260, Cm105721,6130,7670, ,2490, Bk108272,1340,8260, ,3230, Cf110862,5720,8820, ,8060, Es113493,3970,9200, ,5600, Fm116165,2340,9350, ,0480, Md118877,8470,9770, ,3960, No124428,7621,0350, ,6940,

32 SEM Picture after SrTiO 3 :Sm Plasma Treatment

33 SEM Picture after SrTiO3:Tm Plasma Treatment

34 SEM Picture after SrTiO3:Nd Plasma Treatment

35 3D- AFM Picture after SrTiO 3 :Sm Plasma Treatment

36 3D-AFM Picture after SrTiO 3 : Ni Plasma Treatment

3 Energy Levels Scheme Parametrization of nl(f)- Ions

5 Theoretical Foundations Free Ions HFP approach Doped Crystals HL-SCF for Clusters

39 Theoretical Foundations – Ions and Hamiltonians Ion – nl N : Me – 3d N, RE - 4f N, AC - 5f N => ME The main configurations: nl N and nl N n’l’ N’ Cluster: ME +n : [L] k. Ligand – O -2, F -, Cl - etc

6 Theoretical Foundations – Energy of Cluster,,

41 Theoretical Foundations – Radial Integrals

42 Theoretical Results - 3d 2 4p configuration of Cr +3 in Cr +3 :[O -2 ] 6 IntegralFree / R(Å) = Configuration 3d 2 4p F 0 (3d,4p), cm F 2 (3d,4p), cm G 1 (3d,4p), cm G 3 (3d,4p),cm  (3d), cm  (4p), cm (3d|r|3d) a.u (4p|r|4p) a.u (4p|r|4p) a.u ΔE(3d 3 –3d 2 4p), eV

43 Self Consistent Field Equations for nl-Ions in Solids

44 Self-Consistent Potential for nl-Ions in Solids

45 Self Consistent Field Equations for nl-Ions in Solids Boundary conditions: P(nl|r)| r →∞ → 0 - for unit center or impurity ion Wigner-Zeits conditions: ∂P(nl|r)/∂r | r→R → 0 for cluster and crystal

7 SCF Potential and Radial Wave Functions for nf- Ions

47 Short Summary Ab initio study of the electronic structure of ME +n :[L] k -clusters and energy of X-ray lines is a powerful and effective method of investigation of foundations of doped materials. This method and optical spectra of nl- ions in oxides - on the one hand and study of the influence of irradiation or thermal treatment to crystals doped with d- or/and f ions on the other hand allow to explain of the nature of radiation defects into doped oxides and draw the simple conclusion that stability of the oxidation state of ions in crystals is determined relation of energy of ionization of ME +n ion – I Me and Madelung's constant α M = - ΣZ i /r i for the cation site.

48 Concluding Remarks Crystals growth method determines the main defects of the oxides through crystals stoichiometry Crystals stoichiometry determines electronic state and ions valency and properties of the oxide single crystals, too Relation A/O changes: - for simple oxides up 0.95 to for garnet crystals A/B changes up 0.9 to for perovskites – 0.98 (A 1-x B 1-y O 3-z ) Value of A/O and A/B is determined by possibility of the regular nd and nf ions to change their valency. We can used non-stoichiometry oxides for expansion of area of employment of the pure and doped single crystals