Dopant atoms captured by vacancies are known to obstruct vacancy-mediated atomic diffusion. Yet, there are cases where the opposite behavior has been reported. Here, Na doping in Cu(In,Ga)Se2 is shown to enhance or impede the interdiffusion of In and Ga, depending on the relative concentration of Na and Cu. The experimental study suggests that doping a host material may enhance heteroatom diffusivities if (i) dopant migration occurs through the Frank-Turnbull mechanism and (ii) there is overlap between the (cationic/anionic) migration sublattices of dopant and heteroatom. Under such conditions a migration catalysis may occur at sufficiently low dopant concentrations, despite the decreased absolute concentration of point defects responsible for heteroatom diffusion. Herein, a mechanism of doping-assisted catalytic migration is presented.
Frank-Turnbull dopant migration may enhance heteroatom diffusivity: Evidence from alkali-doped Cu(In,Ga)Se2
Diego Colombara
2019-01-01
Abstract
Dopant atoms captured by vacancies are known to obstruct vacancy-mediated atomic diffusion. Yet, there are cases where the opposite behavior has been reported. Here, Na doping in Cu(In,Ga)Se2 is shown to enhance or impede the interdiffusion of In and Ga, depending on the relative concentration of Na and Cu. The experimental study suggests that doping a host material may enhance heteroatom diffusivities if (i) dopant migration occurs through the Frank-Turnbull mechanism and (ii) there is overlap between the (cationic/anionic) migration sublattices of dopant and heteroatom. Under such conditions a migration catalysis may occur at sufficiently low dopant concentrations, despite the decreased absolute concentration of point defects responsible for heteroatom diffusion. Herein, a mechanism of doping-assisted catalytic migration is presented.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
