Burnaby - Dublin - Freiberg – Manchester – Saarbrücken - ISOLDE Collaboration Spokesperson: M. Deicher Contact person: K. Johnston

Introduction Electrical and optical properties of intrinsic defects in ZnO. How to enhance the p-type doping of ZnO? Fine structure in donor energy levels in ZnO. Transition metals in ZnO and their role for dilute magnetic semiconductors. Structure of DX centers in II-VI semiconductors limiting the n-type doping. Multi-atom impurity complexes in silicon. Original proposal: aims Initially awarded 23 shifts instead of requested 35, INTC desirous of more priority in the choice of isotopes. Benefitting from ISOLDE’s wide variety of beams and successfully sharing with other experiments. Last two years has concentrated mostly on PAC and optical measurements of ZnO (electrical technique was being upgraded).

Why so many isotopes? 111 Ag7.45dYYY 2 UC 2 RILIS 117 Ag/ 1 17 Cd 2.4hYYYUC 2 RILIS 113 Ag5.4 hYYNUC 2 RILIS 115 Cd53 hYYYUC 2 RILIS 119 Sb38.5hYYN0.5UC 2 RILIS 104 Cd57.7mYYN 1 SnVADIS 105 Cd55.5mYYNSnVADIS 107 Cd6.5hYYNSnVADIS 191 Hg49minYYN 1.5 PbVADIS 193 Hg3.8hYYNPbVADIS 197 Hg64.4hYYNPbVADIS 204 Bi11.2hYYN0.5UC 2 RILIS 73 As80.3dYYY 1.5 YO/ ZrO 2 VADIS 72 As26hYYNYO/ ZrO 2 VADIS IsotopeT 1/2 PL (L)DLT S PAC Typical # of shifts required Target Ion source 28 Mg 21 hYYN1SCRILIS 24 Na 11.8 h YYN0.5UC 2 W/Ta/R e 43 K 22.3 h YYN0.5UC 2 W/Ta/R e 61 Cu 3.3 hYYY? 1 UC 2 /Y O/ ZrO 2 RILIS 64 Cu 12.4 h YYNUC 2 RILIS 67 Cu 67 hYYNUC 2 RILIS 65 Ni 2.5 hYYN0.5UC 2 RILIS 56 Co 80 dYYN 1 YO/ ZrO 2 VADIS 57 Co 271 d YYNYO/ ZrO 2 VADIS 56 Mn 2.4 hYYN0.75UC 2 RILIS 59 Fe 44.5 d YYNUC 2 RILIS 77 Kr/ 77 Br 57 hYYY2YO/ ZrO 2 VADIS Multi-stranded experiment, utilising ISOLDE beamtimes to provide invaluable input to “traditional” semiconductor spectrocopies

Co-doping of ZnO using group III + group V elements

Proposed PAC experiments for 2012 Is co-doping limited to group III and group V donor acceptor pairs? Or do group I-VII pairs also behave similarly? Stable implantations of group I impurities such as Li and Na to be carried out prior to ISOLDE experiments, or through diffusion. Implantations with 77 Br/ 77 Se to verify if the co-doping is limited to the previous case.

C  detector plane C  detector plane Recent results : formation of Br donor…. Indication of Br occupying O-site

Recent results: PL Multiplicity of lines in ZnO - Various impurities - Various transition types D 0 X – neutral donor-bound excitons D + X – ionised donor bound excitons Also - DAP, eA, A 0 X PL intensity I-lines Photon energy (eV) Widely used for characterisation of semiconductors, chemically blind.

PL resulting from In PL resulting from Ge Presented at MRS Accepted for publication. ICDS2011. PRB (2011)

Perturbation work carried out in Dublin: Stress : orientational information Zeeman: electronic structure

PL work for 2012: ISOLDE Do Si and Sn produce a signal? Does Cd? Carried out in conjunction with stable implantations.

Recent Developments: Installation of Laplace DLTS (J. Bollmann et al., Physica B (2006) 97) “Classical” DLTS Well-established, but has difficulties resolving similar emission rates

Laplace DLTS Achieves higher resolution by minimizing emission rate (related to temperature instabilities during measurement). Needs a cryostat capable of holding very stable temperatures. Example of improvement in signal possible using L-DLTS 2012: aim to carry out most of the original experimental programme, using the new setup.

Multi-atom complexes in Si Quite a body of work now exists on identifying multi- atom impurities in Si. However, dynamics of formation still not well understood. Implantations of 191 Hg and 193 Hg/Au will allow detailed study of the temperature stability of these centres. PL + L-DLTS planned.

Summary of beam request…..and priorities for 2012 Target - Ion source IsotopeMaterial under studyPACPLL-DLTSShifts Pb – HP 191 HgSi/ZnONYY Hg/AuSiNYY UCx – RILIS 56 MnSi/Ge/ZnONYY 1 59 Mn/FeSi/Ge/ZnONYY UCx – Ta/W/Re 43 KSi/ZnONYY 1 24 NaSi/ZnONYY UCx – RILIS 113 AgZnONYY AgZnOYNN SiC – RILIS 28 MgZnONYY1 YO/ZrO - HP 77 BrZnOYNN 2 56 CoSi/GeNYY 71 AsSi/ZnONYY 48 CrZnOYYY All the above beamtimes can be shared with other experiments (not just solid state).