High-lights of High-lights of solid state physics at ISOLDE solid state physics at ISOLDE Instituto Tecnológico e Nuclear, Sacavém, Portugal Instituto Tecnológico e Nuclear, Sacavém, Portugal and Centro de Física Nuclear da Universidade de and Centro de Física Nuclear da Universidade de Lisboa, Portugal Lisboa, Portugal Tracer diffusion: Ag in CdTe Tracer diffusion: Ag in CdTe Transition metal impurities in Si: Fe Transition metal impurities in Si: Fe Photoluminescence: nature of the “green band” in ZnO Photoluminescence: nature of the “green band” in ZnO Arsenic as an “anti-site” impurity in ZnO Arsenic as an “anti-site” impurity in ZnO O and F configurations in High- O and F configurations in High-T c Hg1201 Hg1201 Polaron dynamics in Colossal Magneto-Resistive Polaron dynamics in Colossal Magneto-Resistive manganites manganites Magnetic hyperfine fields of adatoms at surfaces: Cd on Magnetic hyperfine fields of adatoms at surfaces: Cd on Ni Ni Ulrich Wahl Ulrich Wahl
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High-lights of solid state physics at ISOLDE Instituto Tecnológico e Nuclear, Sacavém, Portugal and Centro de Física Nuclear da Universidade de Lisboa,
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High-lights of High-lights of solid state physics at ISOLDEsolid state physics at ISOLDE
Instituto Tecnológico e Nuclear, Sacavém, PortugalInstituto Tecnológico e Nuclear, Sacavém, Portugal
and Centro de Física Nuclear da Universidade de Lisboa, Portugaland Centro de Física Nuclear da Universidade de Lisboa, Portugal
Tracer diffusion: Ag in CdTeTracer diffusion: Ag in CdTe
Transition metal impurities in Si: FeTransition metal impurities in Si: Fe
Photoluminescence: nature of the “green band” in ZnOPhotoluminescence: nature of the “green band” in ZnO
Arsenic as an “anti-site” impurity in ZnOArsenic as an “anti-site” impurity in ZnO
O and F configurations in High-O and F configurations in High-TTcc Hg1201 Hg1201
Polaron dynamics in Colossal Magneto-Resistive manganitesPolaron dynamics in Colossal Magneto-Resistive manganites
Magnetic hyperfine fields of adatoms at surfaces: Cd on NiMagnetic hyperfine fields of adatoms at surfaces: Cd on Ni
Ulrich Wahl Ulrich Wahl
Use of radioactive isotopes in Solid State PhysicsUse of radioactive isotopes in Solid State Physics
- Detect nuclear radiation to quantify impurities:Detect nuclear radiation to quantify impurities: radiotracer diffusionradiotracer diffusion
- Decay particles transmit information with atomic resolution:Decay particles transmit information with atomic resolution: Emission Channeling (EC)Emission Channeling (EC) Perturbed Angular Correlation (PAC)Perturbed Angular Correlation (PAC) Mössbauer Spectroscopy (MS)Mössbauer Spectroscopy (MS) Beta Nuclear Magnetic Resonance (Beta Nuclear Magnetic Resonance (-NMR)-NMR)
- Identify spectroscopic signals via isotope half life:- Identify spectroscopic signals via isotope half life: Photoluminescence (PL)Photoluminescence (PL) Deep Level Transient Spectroscopy (DLTSDeep Level Transient Spectroscopy (DLTS Hall effectHall effect
At ISOLDE often several of these methods are used in At ISOLDE often several of these methods are used in combinationcombination
The “unusual” diffusion of The “unusual” diffusion of 111111AgAg in CdTe in CdTe
H. Wolf H. Wolf et alet al, Phys. Rev. Lett 94 (2005) , Phys. Rev. Lett 94 (2005) 125901125901
depletion of Ag in depletion of Ag in surface regions due surface regions due to slow indiffusion to slow indiffusion of Cd of Cd [Ag[AgSS] ~ [V] ~ [VCdCd]]
CdTeAg
Agi + VCd AgCd Agi + CdS
AgCd + Cdi
Cdi + VCd CdS
Cd Cd
Identify + control Fe in Si below 1010 cm-3
International Technology Roadmap for SemiconductorsInternational Technology Roadmap for Semiconductors
Transition metal impurities in SiTransition metal impurities in Si
Fe, Ni, Co, Cu… fast interstitial diffusers Fe, Ni, Co, Cu… fast interstitial diffusers
deep centersdeep centers
interact with dopants and change the electrical interact with dopants and change the electrical properties of dopantsproperties of dopants
must be gettered away from active region of devices, must be gettered away from active region of devices, e.g. by trapping at e.g. by trapping at radiation damageradiation damage
investigate properties of Fe in Si by Emission investigate properties of Fe in Si by Emission Channeling (EC) and Mössbauer spectroscopy (MS)Channeling (EC) and Mössbauer spectroscopy (MS)
U. Wahl U. Wahl et alet al, Phys. Rev. B 72 (2005) , Phys. Rev. B 72 (2005) 014115014115
At least 3 different Fe lattice sitesAt least 3 different Fe lattice sites
Following release to interstitial state re-gettering occurs at a different Following release to interstitial state re-gettering occurs at a different gettering center on ideal substitutional sitesgettering center on ideal substitutional sites
Lattice site changes of implanted Lattice site changes of implanted 5959FeFe in Si in Si
RT as-implanted:RT as-implanted:
mainly displaced mainly displaced substitutional Fesubstitutional Fe
Mössbauer effect from Mössbauer effect from 5757Mn Mn 5757FeFe in Si in Si
H.P. Gunnlaugsson et al, Appl. Phys. Lett. 80 (2002) 2657H.P. Gunnlaugsson et al, Appl. Phys. Lett. 80 (2002) 2657
4-5 different Fe centers identified4-5 different Fe centers identified
interstitial Fe seen by EC is probablyinterstitial Fe seen by EC is probably a (Fe a (Feii-V) complex-V) complex
MS line broadening reveals MS line broadening reveals difference in diffusion difference in diffusion coefficients of Fecoefficients of Feii
and Fe and Feii00
FeiV
FeiV
FeiV
wurtzite semiconductor with band gap of 3.4 eVwurtzite semiconductor with band gap of 3.4 eV
very similar to GaN but with superior optical propertiesvery similar to GaN but with superior optical properties
large single crystals availablelarge single crystals available
Major problemMajor problem
all undoped crystals are all undoped crystals are nn-type -type (vacancies, interstitials, other defects, impurities?)(vacancies, interstitials, other defects, impurities?)
Puzzles of the “green band” in ZnOPuzzles of the “green band” in ZnO““Structured” green luminescence band in ZnOStructured” green luminescence band in ZnO
R. Dingle, Phys. Rev. Lett. 23 (1969) R. Dingle, Phys. Rev. Lett. 23 (1969) 579 579
Conflicting explanations for the “green band” in the literature:
• CuZn - impurities• Vacancies (e.g., VO, VZn)
diffusion diffusion
donor
acceptor
conduction band
valence band
exci
tatio
n
Photoluminescence
investigate properties of Cu in ZnO and nature of investigate properties of Cu in ZnO and nature of green band by emission channeling and PLgreen band by emission channeling and PL
Lattice location of Lattice location of 6767CuCu6767Zn in ZnOZn in ZnO
67Cu
61.9 h
67Zn
-
Implanted Cu occupies substitutional Zn sites:
CuZn
U. Wahl et al, Phys. Rev. B 69 (2004) 012102U. Wahl et al, Phys. Rev. B 69 (2004) 012102
Only patterns for SOnly patterns for SZnZn fit the fit the
experimental results!experimental results!
U. Wahl U. Wahl et alet al, in print, Phys. Rev. Lett. (2005), in print, Phys. Rev. Lett. (2005)
High-High-TTcc superconductors superconductors
Superconductivity and its Superconductivity and its TTcc
critically influenced by the critically influenced by the charge that Ocharge that O22 doping doping introduces in the introduces in the superconducting CuOsuperconducting CuO22 planes planes
Twice the number of FTwice the number of F introduce introduce the same charge dopingthe same charge doping
investigate atomistic investigate atomistic configurations of Oconfigurations of O22 and F and F dopants by means of electrical dopants by means of electrical field gradient (EFG) it causes on field gradient (EFG) it causes on PAC probe atom PAC probe atom 199m199mHgHg
frequency
start stop
I Q
I
Ii
Q
1
IfIf
Q.Vzz
clock
time
Radioactive
ions PAC
Electric Field Gradient
dopant configuration fingerprint
HgBa2CuO4
+
Tc > 92K
O(2)
Cu O(1)
Ba
Hg
PAC
PAC
Experiment ~ 0.20
0 2500 5000 (Mrad/s)
0
50
100
~ 0.0
0
50
100
000 2500 5000
(Mrad/s)
0.34 (a)
EFG Simulations
J.G. Correia J.G. Correia et alet al, in press, Phys. Rev. B (2005), in press, Phys. Rev. B (2005)
Oxygen & Fluorine Configurations in Hg1201 (High-Oxygen & Fluorine Configurations in Hg1201 (High-TTcc))
In contrast to O, In contrast to O, F orders in small F orders in small atomistic stripesatomistic stripes
Local deformations Local deformations and atomistic stripes and atomistic stripes in the doping planes in the doping planes are are NOTNOT responsible responsible for for charge orderingcharge ordering at the CuOat the CuO22 planes planes
Complex multi-scale world with:Complex multi-scale world with:
Intrinsic inhomogeneitiesIntrinsic inhomogeneitiesClusters and stripes (charge, spin and structure) Clusters and stripes (charge, spin and structure) Unconventional phase transitionsUnconventional phase transitions Charge-coupled lattice deformations: PolaronsCharge-coupled lattice deformations: Polarons
Strong coupling of Strong coupling of spinspin, , chargecharge, , orbitalorbital and and lattice degrees of freedomlattice degrees of freedom
use use 111m111mCd impurities as local observers of the nature Cd impurities as local observers of the nature of structural phase transitions by means of PACof structural phase transitions by means of PAC
200 400 600 8000
20
40
60
80
0,0
0,3
0,6
0,9
fd
fu
fC
Orth. phase(x-ray)
T (K)
%=0.12
u
=0.08
=0
d
Unconventional phase transitions as seen Unconventional phase transitions as seen by by 111m111mCdCd in LaMnO in LaMnO3.123.12
• Hopping energy Hopping energy EEaa~0.31 ~0.31 eVeV
Dynamic JDynamic Jahn-ahn-TTellereller distortions related to polaron diffusion distortions related to polaron diffusion give rise to EFG fluctuations/attenuationgive rise to EFG fluctuations/attenuation
Fast fluctuations regime(observable region)
A.M.L. Lopes et al, submitted to Phys. Rev. Lett. A.M.L. Lopes et al, submitted to Phys. Rev. Lett.
4
111Cd Probe on Ni(001)
Subst. Terrace SiteNN = 8
Free Kink SiteNN = 6
Adatom siteNN = 4 Subst. Step Site
NN = 7
Free Step SiteNN = 5
Impurity Atoms at Various Siteson a Surface (001)
Magnetism on surfacesMagnetism on surfaces
Different adatom sites can be prepared via Different adatom sites can be prepared via deposition and anneal temperaturedeposition and anneal temperature
allows systematic studies of magnetic hyperfine fields allows systematic studies of magnetic hyperfine fields BBHFHF
at different sites by means of PACat different sites by means of PAC
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MagneticHyperfine Fieldsat 111Cd on Ni Surfaces
Coordination Number
1968
PRL 88, 247201 (2002)Theory: Mavropoulos et al. PRL 81, 1506 (1998)
13 12 11 10 9 8 7 6 5 4 3 2 1
-10
-5
0
5
10
15
20
25
-|Bhf
| [T]
Ni(001) Ni(111) Ni(111) vicinal
Bhf ~ [Coord. No.]2
|Bhf
| [T]
Adatom
Bulk
Konstanz group:Ni(001):6,4;
Ni(111)
Ni(001)
K. Potzger et al, Phys. Rev. Lett. 88 (2002) 247201K. Potzger et al, Phys. Rev. Lett. 88 (2002) 247201BBHFHF parabolic function parabolic function