Lattice, band, and spin engineering in Zn1−<i>x</i>Co<i>x</i>O

Matsui, Hiroaki; Tabata, Hitoshi

doi:10.1063/1.4804656

Cited by 7 publications

(13 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6. The calculated coefficient b defined by the relation E gap (x) = E gap (0) + bx is 1.9 eV, which agrees well with the experimental values 1.1 [3], 1.7 [4], 2.3 [66] and 2.5 eV [9].…”

Section: Comparison With Experimentssupporting

confidence: 87%

“…In the absorption measurements, only one ionization channel is seen at energies just below the band gap [2,4,6,9,10]. Based on our results, we assign this transition to t 2↑ → CBM, i.e.…”

Section: Comparison With Experimentsmentioning

confidence: 60%

“…1. Equation 1 [13,[64][65][66], while the energy range of internal transitions is taken from absorption [1,3,5,8,9,11,12]. See text for definitions of ionization Eion1 and Eion2 and internal transition Eint energies.…”

Section: A Co Levels In Znomentioning

confidence: 99%

“…4, where the vertical transitions are shown by arrows.) Both transitions can be completely suppressed by the two step processes involving (Co 2+ ) * , which is probably observed in the luminescence [7,9,11,12,70].…”

Section: Comparison With Experimentsmentioning

confidence: 99%

See 3 more Smart Citations

Calculated optical properties of Co in ZnO: internal and ionization transitions

Ciechan

Bogusławski²

2019

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Previous luminescence and absorption experiments in Co-doped ZnO revealed two ionization and one intrashell transition of d(Co 2+ ) electrons. Those optical properties are analyzed within the generalized gradient approximation to the density functional theory. The two ionization channels involve electron excitations from the two Co 2+ gap states, the t 2↑ triplet and the e 2↓ doublet, to the conduction band. The third possible ionization channel, in which an electron is excited from the valence band to the Co 2+ level, requires energy in excess of 4 eV, and cannot lead to absorption below the ZnO band gap, contrary to earlier suggestions. We also consider two recombination channels, the direct recombination and a two-step process, in which a photoelectron is captured by Co 3+ and then recombines via the internal transition. Finally, the observed increase the band gap with the Co concentration is well reproduced by theory.The accurate description of ZnO:Co is achieved after including +U corrections to the relevant orbitals of Zn, O, and Co. The +U (Co) value was calculated by the linear response approach, and independently was obtained by fitting the calculated transition energies to the optical data. The respective values, 3.4 and 3.0 eV, agree well. Ionization of Co induces large energy shifts of the gap levels, driven by the varying Coulomb coupling between the d(Co) electrons, and by large lattice relaxations around Co ions. In turn, over ∼ 1 eV changes of Co 2+ levels induced by the internal transition are mainly caused by the occupation-dependent U (Co) corrections.

show abstract

“…6. The calculated coefficient b defined by the relation E gap (x) = E gap (0) + bx is 1.9 eV, which agrees well with the experimental values 1.1 [3], 1.7 [4], 2.3 [66] and 2.5 eV [9].…”

Section: Comparison With Experimentssupporting

confidence: 87%

Section: Comparison With Experimentsmentioning

confidence: 60%

Section: A Co Levels In Znomentioning

confidence: 99%

Section: Comparison With Experimentsmentioning

confidence: 99%

See 2 more Smart Citations

Calculated optical properties of Co in ZnO: internal and ionization transitions

Ciechan

Bogusławski²

2019

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

show abstract

“…For antiferromagnetic phase the effect of ex− change interaction changes so as to produce a blue shift [35]. Matsui et al [30] have showed (VB) PES−spectra of ZnO and Zn 1-x Co x O reflecting the effect of Co (3d) states, which re− mains unchanged with increasing x and the band gap in Zn 1-x Co x O has been explained in terms of sp hybridization between ZnO and CoO. Furdyna [36] stressed the close rela− tionship of s and p electron bands in A II 1-x Mn x B VI material to the band structure of nonmagnetic A II B VI materials.…”

Section: Transmission and Optical Band Gapmentioning

confidence: 99%

Enhancement in UV emission and band gap by Fe doping in ZnO thin films

Srivastava

Kumar

Khare

2014

Opto-Electronics Review

View full text Add to dashboard Cite

Enhancement of the optical band gap of ZnO from 3.14 to 3.29 eV has been obtained using Fe dopant. Undoped and doped ZnO films are deposited by sol-gel spin coating. XRD patterns indicate polycrystalline nature and hexagonal wurtzite structure of Zn1−xFexO films. EDX analysis confirms the presence of iron dopant. The photoluminescence spectra show an ultraviolet emission peak at 398 nm (NBE emission) and defect emission peak at 485 nm. Intensity of the NBE emission is much higher for the doped samples with its ratio to defect emission intensity highest for 2 at. %doping. The NBE emission shifts to higher energy with increasing dopant concentration in a manner similar to that exhibited by the band gap. Surface morphology has been studied using FESEM.

show abstract