title: Effect of Al3+ co-doping on the dopant local structure, optical properties, and exciton dynamics in Cu+-doped ZnSe nanocrystals.
abstract: The dopant local structure and optical properties of Cu-doped ZnSe (ZnSe:Cu) and Cu and Al co-doped ZnSe (ZnSe:Cu,Al) nanocrystals (NCs) were studied with an emphasis on understanding the impact of introducing Al as a co-dopant. Quantum-confined NCs with zinc blende crystal structure and particle size of 6 ± 0.6 Å were synthesized using a wet chemical route. The local structure of the Cu dopant, studied by extended X-ray absorption fine structure, indicated that Cu in ZnSe:Cu NCs occupies a site that is neither substitutional nor interstitial and is adjacent to a Se vacancy. Additionally, we estimated that approximately 25 ± 8% of Cu was located on the surface of the NC. Al(3+) co-doping aids in Cu doping by accounting for the charge imbalance originated by Cu(+) doping and consequently reduces surface Cu doping. The Cu ions remain distorted from the center of the tetrahedron to one of the triangular faces. The lifetime of the dopant-related photoluminescence was found to increase from 550 ± 60 to 700 ± 60 ns after Al co-doping. DFT calculations were used to obtain the density of states of a model system to help explain the optical properties and dynamics processes observed. This study demonstrates that co-doping using different cations with complementary oxidation states is an effective method to enhance optical properties of doped semiconductor NCs of interest for various photonics applications.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz , California 95064, United States.
authors.forename: Sheraz
authors.initials: S
authors.lastname: Gul
authors.forename: Jason Kyle
authors.initials: JK
authors.lastname: Cooper
authors.forename: Per-Anders
authors.initials: PA
authors.lastname: Glans
authors.forename: Jinghua
authors.initials: J
authors.lastname: Guo
authors.forename: Vittal K
authors.initials: VK
authors.lastname: Yachandra
authors.forename: Junko
authors.initials: J
authors.lastname: Yano
authors.forename: Jin Zhong
authors.initials: JZ
authors.lastname: Zhang