TY - JOUR
T1 - Nature of the Positron State in CdSe Quantum Dots
AU - Shi, Wenqin
AU - Callewaert, Vincent
AU - Barbiellini, Bernardo
AU - Saniz, Rolando
AU - Butterling, Maik
AU - Egger, Werner
AU - Dickmann, Marcel
AU - Hugenschmidt, Christoph
AU - Shakeri, Behtash
AU - Brück, Ekkes
AU - Eijt, Stephan W.H.
AU - More Authors, null
PY - 2018
Y1 - 2018
N2 - Previous studies have shown that positron-annihilation spectroscopy is a highly sensitive probe of the electronic structure and surface composition of ligand-capped semiconductor quantum dots (QDs) embedded in thin films. The nature of the associated positron state, however, whether the positron is confined inside the QDs or localized at their surfaces, has so far remained unresolved. Our positron-annihilation lifetime spectroscopy studies of CdSe QDs reveal the presence of a strong lifetime component in the narrow range of 358-371 ps, indicating abundant trapping and annihilation of positrons at the surfaces of the QDs. Furthermore, our ab initio calculations of the positron wave function and lifetime employing a recent formulation of the weighted density approximation demonstrate the presence of a positron surface state and predict positron lifetimes close to experimental values. Our study thus resolves the long-standing question regarding the nature of the positron state in semiconductor QDs and opens the way to extract quantitative information on surface composition and ligand-surface interactions of colloidal semiconductor QDs through highly sensitive positron-annihilation techniques.
AB - Previous studies have shown that positron-annihilation spectroscopy is a highly sensitive probe of the electronic structure and surface composition of ligand-capped semiconductor quantum dots (QDs) embedded in thin films. The nature of the associated positron state, however, whether the positron is confined inside the QDs or localized at their surfaces, has so far remained unresolved. Our positron-annihilation lifetime spectroscopy studies of CdSe QDs reveal the presence of a strong lifetime component in the narrow range of 358-371 ps, indicating abundant trapping and annihilation of positrons at the surfaces of the QDs. Furthermore, our ab initio calculations of the positron wave function and lifetime employing a recent formulation of the weighted density approximation demonstrate the presence of a positron surface state and predict positron lifetimes close to experimental values. Our study thus resolves the long-standing question regarding the nature of the positron state in semiconductor QDs and opens the way to extract quantitative information on surface composition and ligand-surface interactions of colloidal semiconductor QDs through highly sensitive positron-annihilation techniques.
UR - http://resolver.tudelft.nl/uuid:f90a4d48-8538-42f6-905e-b33227abb90c
UR - http://www.scopus.com/inward/record.url?scp=85051536073&partnerID=8YFLogxK
U2 - 10.1103/PhysRevLett.121.057401
DO - 10.1103/PhysRevLett.121.057401
M3 - Article
AN - SCOPUS:85051536073
SN - 0031-9007
VL - 121
JO - Physical Review Letters
JF - Physical Review Letters
IS - 5
M1 - 057401
ER -