Abstract:We report on first principle investigations about the electrical character of Li-X codoped ZnO transparent conductive oxides (TCOs). We studied a set of possible X codopants including either unintentional dopants typically present in the system (e.g., H, O) or monovalent acceptor groups, based on nitrogen and halogens (F, Cl, I). The interplay between dopants and structural point defects in the host (such as vacancies) is also taken explicitly into account, demonstrating the crucial effect that zinc and oxygen… Show more
“…3 . Similarly, the net magnetization is associated to unpairing of neighboring S-orbitals induced by the partially saturated Zn vacancies, as it happens for the case of ZnO 39 – 41 . Figure 3 ( a ) Modification of the total DOS around the band gap region of ZB-ZnS upon Cu doping at different dosages.…”
We revise the electronic and optical properties of ZnS on the basis of first principles simulations, in view of novel routes for optoelectronic and photonic devices, such as transparent conductors and plasmonic applications. In particular, we consider doping effects, as induced by Al and Cu. It is shown that doping ZnS with Al imparts a n-character and allows for a plasmonic activity in the mid-IR that can be exploited for IR metamaterials, while Cu doping induces a spin dependent p-type character to the ZnS host, opening the way to the engineering of transparent p-n junctions, p-type transparent conductive materials and spintronic applications. The possibility of promoting the wurtzite lattice, presenting a different symmetry with respect to the most stable and common zincblende structure, is explored. Homo- and heterojunctions to twin ZnO are discussed as a possible route to transparent metamaterial devices for communications and energy.
“…3 . Similarly, the net magnetization is associated to unpairing of neighboring S-orbitals induced by the partially saturated Zn vacancies, as it happens for the case of ZnO 39 – 41 . Figure 3 ( a ) Modification of the total DOS around the band gap region of ZB-ZnS upon Cu doping at different dosages.…”
We revise the electronic and optical properties of ZnS on the basis of first principles simulations, in view of novel routes for optoelectronic and photonic devices, such as transparent conductors and plasmonic applications. In particular, we consider doping effects, as induced by Al and Cu. It is shown that doping ZnS with Al imparts a n-character and allows for a plasmonic activity in the mid-IR that can be exploited for IR metamaterials, while Cu doping induces a spin dependent p-type character to the ZnS host, opening the way to the engineering of transparent p-n junctions, p-type transparent conductive materials and spintronic applications. The possibility of promoting the wurtzite lattice, presenting a different symmetry with respect to the most stable and common zincblende structure, is explored. Homo- and heterojunctions to twin ZnO are discussed as a possible route to transparent metamaterial devices for communications and energy.
“…The conductivities of SrZn 1– x Li x O 2 were found to be in the range of 1 × 10 –6 –3.5 × 10 –6 S cm –1 at 600 °C, significantly lower than the conductivities reported for other p-type conducting materials prepared in thin-film form. The low conductivity may be due to microstructural differences, compensation mechanisms, such as the formation of oxygen vacancies, which are known to exist in large concentration in ZnO or could result from strong trapping of the charges created by the dopants . The formation of Li i defect states, which in Li/ZnO are known to act as donors, could also compensate for any p-type conductivity obtained from the Li Zn ′ acceptor defects …”
It is challenging to achieve p-type doping of zinc oxides (ZnO), which are of interest as transparent conductors in optoelectronics. A ZnO-related ternary compound, SrZnO, was investigated as a potential host for p-type conductivity. First-principles investigations were used to select from a range of candidate dopants the substitution of Li for Zn as a stable, potentially p-type, doping mechanism in SrZnO. Subsequently, single-phase bulk samples of a new p-type-doped oxide, SrZnLi O (0 < x < 0.06), were prepared. The structural, compositional, and physical properties of both the parent SrZnO and SrZnLi O were experimentally verified. The band gap of SrZnO was calculated using HSE06 at 3.80 eV and experimentally measured at 4.27 eV, which confirmed the optical transparency of the material. Powder X-ray diffraction and inductively coupled plasma analysis were combined to show that single-phase ceramic samples can be accessed in the compositional range x < 0.06. A positive Seebeck coefficient of 353(4) μV K for SrZnLi O, where x = 0.021, confirmed that the compound is a p-type conductor, which is consistent with the p dependence of the electrical conductivity observed in all SrZnLi O samples. The conductivity of SrZnLi O is up to 15 times greater than that of undoped SrZnO (for x = 0.028 σ = 2.53 μS cm at 600 °C and 1 atm of O).
“…Li + or Cs + at Ni sites is also a widely used method to enhance the NiO conductivity (up to values of ~10-20 -1 cm -1 ) [188] , [189] , [190] , [191] . Analogously, Li doped ZnO (~3.6 eV) has a ptype character, when Li is included as Zn substitutional dopant, but it turns into an n-type when Li is in interstitial sites [192] , [193] .…”
New device concepts and new computing principles are needed to balance our ever-growing appetite for data and information with the realization of the goals of increased energy efficiency, reduction in CO 2 emissions and the circular economy. Neuromorphic or synaptic electronics is an emerging field of research aiming to overcome the current computer's Von-Neumann bottleneck by building artificial neuronal systems to mimic the extremely energy efficient biological synapses. The introduction of photovoltaic and/or photonic aspects into these neuromorphic architectures will produce self-powered adaptive electronics but may also open up new possibilities in artificial neuroscience, artificial neural communications, sensing and machine learning which would enable, in turn, a new era for computational systems owing to the possibility of attaining high bandwidths with much reduced power consumption. This perspective is focused on recent progress in the implementation of functional oxide thinfilms into photovoltaic and neuromorphic applications towards the envisioned goal of selfpowered photovoltaic neuromorphic systems or a solar brain.
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