Zn Vacancies Research Articles

Effects of Vacancy Defects on Electrical and Optical Properties of ZnO/WSe2 Heterostructure: First-Principles Study

In this work, based on the first principles calculation of density functional theory (DFT), we studied the band structure changes of monolayer ZnO and ZnO/WSe2 before and after vacancy generation, and systematically studied the vacancy formation energy, band structure, density of states, electronic density difference and optical properties of ZnO/WSe2 heterostructure before and after vacancy generation. The results show that the band structures of ZnO, WSe2, and ZnO/WSe2 heterostructure are changed after the formation of Zn, O, W, and Se vacancies. The bandgap of the ZnO/WSe2 heterostructure can be effectively controlled, the transition from direct to indirect bandgap semiconductor will occur, and the heterostructure will show metallic properties. The optical properties of heterostructure have also changed significantly, and the absorption capacity of heterostructure to infrared light has been greatly increased with red shift and blue shift respectively. The generation of vacancy changes the electrical and optical properties of ZnO/WSe2 heterostructure, which provides a feasible strategy for adjusting the photoelectric properties of two-dimensional optoelectronic nano devices and has good potential and broad application prospects.

Identity of the reversible hole traps in InP/ZnSe core/shell quantum dots.

Density functional theory calculations are combined with time-resolved photoluminescence experiments to identify the species responsible for the reversible trapping of holes following photoexcitation of InP/ZnSe/ZnS core/shell/shell quantum dots (QDs) having excess indium in the shell [P. Cavanaugh et al., J. Chem. Phys. 155, 244705 (2021)]. Several possible assignments are considered, and a substitutional indium adjacent to a zinc vacancy, In3+/VZn 2-, is found to be the most likely. This assignment is consistent with the observation that trapping occurs only when the QD has excess indium and is supported by experiments showing that the addition of zinc oleate or acetate decreases the extent of trapping, presumably by filling some of the vacancy traps. We also show that the addition of alkyl carboxylic acids causes increased trapping, presumably by the creation of additional zinc vacancies. The calculations show that either a single In2+ ion or an In2+-In3+ dimer is much too easily oxidized to form the reversible traps observed experimentally, while In3+ is far too difficult to oxidize. Additional experimental data on InP/ZnSe/ZnS QDs synthesized in the absence of chloride demonstrates that the reversible traps are not associated with Cl-. However, a zinc vacancy adjacent to a substitutional indium is calculated to have its highest occupied orbitals about 1eV above the top of the valence band of bulk ZnSe, in the appropriate energy range to act as reversible traps for quantum confined holes in the InP valence band. The associated orbitals are predominantly composed of p orbitals on the Se atoms adjacent to the Zn vacancy.

Precursor mediated and defect engineered ZnO nanostructures using thermal chemical vapor deposition for green light emission

We used thermal chemical vapour deposition to synthesize zinc oxide nanostructured thin films on n-type silicon substrate using zinc oxide (ZnO) and zinc chloride (ZnCl2) powder precursors in conjunction with bulk graphite powder. The synthesized ZnO nanostructured thin films structures are polycrystalline with a relatively enhanced c-axis orientation for ZnO powder precursor with respect to that of ZnCl2 precursor. The scanning electron microscopic analysis substantiate the higher c-axis orientation of ZnO nanostructures, grown using ZnO powder precursor. The photoluminescence (PL) and UV–Vis measurements suggest the presence of zinc vacancies, causing the green emission from both nanostructured thin films. The measured bandgap of ZnO nanostructured thin film using ZnO powder precursor is slightly higher than that of ZnCl2 powder precursor. The capacitance-voltage and Mott-Schottky measurements showed the n-type characteristics with 6.3 × 1016 cm−3 and 2.7 × 1015 cm−3 carrier densities for ZnO nanostructured thin films prepared using ZnO and ZnCl2 precursors, respectively. The current-voltage measurements showed relatively lower current for ZnO nanostructured thin films, synthesized using ZnCl2 precursor, signifying the presence of zinc vacancies trap sites and is also consistent with Mott-Schottky measurements, showing lower carrier concentrations with respect to that of ZnO precursor derived ZnO nanostructured thin films. Thus, controlled Zn vacancies in ZnO nanostructured thin films may lead to the efficient green light emitters, useful for green light colour emission applications.

Understanding the Sensing Mechanism of ZnO Nanoparticles through Identifying Intrinsic Defects

Progress in crystal growth made ZnO applicable as the next generation of inorganic light-emitting diodes and lasers, which has attracted much attention. Our previous work is a proof that Zn vacancies are occupied by three protons to form VZnH3 complexes in high-quality ZnO single crystals. In this work, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) studies on high-quality ZnO single crystals further confirm that three proton clusters or cations with three positive charges are the intrinsic defects and/or impurities related to doping in the host-lattice of high-quality ZnO single crystals. Unintentionally doped hydrogen (H) clusters might be relating to ZnO’s sensing capabilities. The sensor response of ZnO semiconductors is promoted by a decreasing size; however, the nature of the size effects has not been elucidated satisfactorily. In this work, broccoli-like ZnO nanoarrays, which can detect H2S gas in the parts per billion (ppb) region, has been synthesized under a hydrothermal method. High-resolution transmission electron microscopy (HRTEM) experimental results demonstrate that there are multiple polar faces exposed on the surfaces of ZnO nano crystals. The high catalytic active of oxygen species adsorbed on the multiple polar surfaces should respond to the high sensing performance and the high selectivity of ZnO toward reducing H2S gas. However, the enormous variations in electric current cannot be produced by releasing electrical charges from O– adsorbates into semiconductors. EPR results show that Zn+ interstitials have been produced after the reaction between H2S and O– adsorbates on ZnO. In contrast to the unintentionally doped hydrogen (H) clusters, our experimental results show that the Zn+ interstitials acting as shallow donors is what really offer the extra free-electron carriers.

Effect of indium doping on the optoelectronic properties of ZnSe films

Polycrystalline In:ZnSe films were prepared by the thermal co-evaporation method, where high purity ZnSe and In2Se3 powders are taken as source materials. Orderly change in the X-ray diffraction peak position and red shift in the optical absorption edge have confirmed the incorporation of the dopant in the system. Photoluminescence spectra showed that the doped system has a Zn vacancy, which is in line with energy dispersive spectroscopy measurements. The chemical state of the doped films i.e., Zn2+, In3+ and Se2− was analysed by Raman and X-ray photoelectron spectroscopy (XPS); XPS has also indicated the incorporation of oxygen in small fractions which improves the conductivity of the films. The electrical investigation has revealed that electrical properties altered by doping and majority charge carriers are electrons and carrier density is in the order of 1015 cm−3. Films with 15 at. % In exhibited good photoresponse in the visible range and suitable for photodetector applications.

Vacancy driven surface disorder catalyzes anisotropic evaporation of ZnO (0001) polar surface

The evaporation and crystal growth rates of ZnO are highly anisotropic and are fastest on the Zn-terminated ZnO (0001) polar surface. Herein, we study this behavior by direct atomic-scale observations and simulations of the dynamic processes of the ZnO (0001) polar surface during evaporation. The evaporation of the (0001) polar surface is accelerated dramatically at around 300 °C with the spontaneous formation of a few nanometer-thick quasi-liquid layer. This structurally disordered and chemically Zn-deficient quasi-liquid is derived from the formation and inward diffusion of Zn vacancies that stabilize the (0001) polar surface. The quasi-liquid controls the dissociative evaporation of ZnO with establishing steady state reactions with Zn and O2 vapors and the underlying ZnO crystal; while the quasi-liquid catalyzes the disordering of ZnO lattice by injecting Zn vacancies, it facilitates the desorption of O2 molecules. This study reveals that the polarity-driven surface disorder is the key structural feature driving the fast anisotropic evaporation and crystal growth of ZnO nanostructures along the [0001] direction.

Anisotropic Li diffusion in pristine and defective ZnO bulk and (10[formula omitted]0) surface

We study the Li interstitial diffusion in pristine and defective ZnO bulk and (101¯0) surface by means of first-principles density functional theory (DFT) coupled with the Nudged Elastic Band (NEB) calculations. We consider three types of point defects, i.e., oxygen vacancy (Ovac), Zn vacancy (Znvac) and ZnO vacancy pair (ZnOvac-pair) and investigate their individual effect on the energy barrier of Li interstitial diffusion. Our results predict that Ovac and Znvac lower the Li diffusion energy barrier as compared to the pristine ZnO case. However, we further find that Li interstitial, on the other hand, may possibly be trapped inside the Znvac subsequently forming the LiZn substitutional type of defect. The similar behavior also observed for Li interstitial in the vicinity of Zn-Ovac_pair though with less change of Li diffusion barriers as compared to the other two cases. For Li diffusion on the ZnO surface, our results indicate that Ovac imposes similar effect as in the bulk case; it lowers the energy barriers for Li to diffuse outward (inward) from (to) ZnO sub-surface lattice. Our results indicate that among the three considered defects only Ovac shows possible enhancement of the kinetics of Li diffusion inside the bulk and on the surface of ZnO.

Electroluminescence from Silicon-Based Light-Emitting Devices with Erbium-Doped ZnO Films: Strong Enhancement Effect of Titanium Codoping.

We report on the visible and near-infrared electroluminescence (EL) from the light-emitting device (LED) based on the erbium (Er)-doped ZnO (ZnO:Er)/SiO2/n+-Si heterostructure, wherein an ∼10 nm thick SiO2 intermediate layer serves as the energy plateau for producing hot electrons, which come from n+-Si via the trap-assisted tunneling mechanism. These hot electrons excite the doped Er3+ ions by inelastic collision, enabling the Er-related EL from the aforementioned LED. More importantly, by means of codoping the appropriate content of titanium (Ti) into the ZnO:Er film, the aforementioned Er-related emissions can be significantly enhanced. The density functional theory calculations indicate that the Ti-codoping improves rather than degrades the symmetry of the crystal field around the optically active Er3+ ions, hence not increasing the intra-4f transition probabilities of Er3+ ions. However, it is found that Ti-codoping nearly eliminates the segregation of Er3+ ions near the ZnO/SiO2 interface. Moreover, Ti-codoping is derived to result in a number of Zn vacancies, which provide the sites for incorporating Er3+ ions in the ZnO matrix. For the above two reasons, the Ti-codoping promotes the incorporation of optically active Er3+ ions into the ZnO matrix, thus enhancing the EL from the aforementioned LED.

Explosive hydrogen evolution from water splitting without sacrificial agent from the C, N co-doped Zn defective ZnS particle

In this study, we designed highly efficient, durable, inexpensive and photo-stable ZnS photocatalysts with Zn vacancies without heterojunctions for hydrogen production. Two types of spherical ZnS nanoparticles of < 10 nm size—ZnS-sulfur powder (S) and ZnS-thiourea (thio)—were synthesized by a simple hydrothermal method using sulfur powder and thiourea as the sulfur sources, respectively. The Zn vacancies introduced into the two particles shortened the band-gap and considerably improved the separation of the photogenerated carriers. However, the ZnS-S particles had higher number of Zn vacancies than those in ZnS-thio particles. ZnS-thio particles, which have Zn vacancies with the C and N co-doping, generated more than twice the amount of ∙OH and ∙O2− radicals than the ZnS-S particles, and demonstrated slower electron and hole recombination. The water splitting proceeded faster and more favorably in ZnS-thio particles, and the average hydrogen production rate without sacrificial agents was 176 μmol g–1h−1. ZnS-thio particles also maintained the excellent hydrogen generation efficiency without photo-corrosion even after five consecutive regeneration cycles. This study demonstrates the significant photocatalytic potential of ZnS containing appropriate number of Zn vacancies along with simultaneous complementary N-doping and strong C-doping.

Construction dual vacancies to regulate the energy band structure of ZnIn2S4 for enhanced visible light-driven photodegradation of 4-NP

Most of the intrinsic photocatalysts with visible light response can only generate one active radical due to the limitation of their band structures, which is immediate cause limiting their photocatalytic degradation performance. In this work, ZnIn2S4 with Zn vacancy and S vacancy (VZn+S-ZnIn2S4) was prepared for the first time. As expected, the VZn+S-ZnIn2S4 exhibits remarkable photocatalytic performance for 4-Nitrophenol (4-NP) degradation under visible light and the apparent rate constant is about 11 times that of pristine ZnIn2S4. The construction of dual vacancies can regulate the energy band structure of the ZnIn2S4, enabling it to generate •OH and •O2− simultaneously. Meanwhile, dual vacancies system can also extremely improve the separation efficiency of carriers. It is worth noting that Zn vacancy and S vacancy can capture photogenerated holes and photogenerated electrons, respectively, which is beneficial for photogenerated carriers to participate in radical generation reactions. In addition, a possible 4-NP degradation pathway was proposed based on HPLC-MS analysis. This work provides a new way to construct photocatalysts for photodegradation of pollutants in wastewater.

Defect Chemistry of Halogen Dopants in ZnSe.

Halogen dopants in ZnSe have been a research focus for quantum applications utilizing excitonic emissions, wherein point defects play a critical role. To provide a full first-principles perspective on the defect chemistries of halogen-doped ZnSe, Cl- and F-doped ZnSe were explored via hybrid functional density functional theory calculations involving all possible isolated defects and defect-defect complexes. Cl and F both exhibit more complicated defect chemistries than just forming a shallow substitutional donor on the Se site. For Cl, the complex of Cl substituting for Se with a neighboring Zn vacancy was also found to be prevalent. For F, its interstitial in the Zn tetrahedron was found to be stable in addition to the complex of such interstitial with an adjacent F atom substituting for Se. The explicitly simulated emission photoluminescence lineshapes of the self-activated centers exhibited both a peak value and a broad line width consistent with the experiment.

Defect engineered blue photoluminescence in ZnO:Al/TiO2 heterostructures

Tailoring the blue photoluminescence (PL) in Al-doped ZnO (AZO)/TiO2 heterostructures is demonstrated by a controlled induction of shallow defect centers by 50 keV Ar+-ions. This is established by a combination of temperature dependent PL and electron paramagnetic resonance spectroscopy. The dominant blue-violet PL in an as-grown sample comprises a near band-edge emission, along with a peak associated with a radiative recombination of the electrons in shallow donor levels (Zn interstitials) and the holes from the valence band. However, the evolution of an additional yellow-green PL band at a fluence of 1 × 1015 ions/cm2 is governed by deep donor levels, particularly ionized oxygen vacancies. Irradiation at 1 × 1016 ions/cm2 further leads to the formation of Zn vacancies (shallow acceptors) owing to the development of an O-rich surface. The structural modifications of these samples have been investigated by field-emission scanning electron microscopy , transmission electron microscopy, and Rutherford backscattering. While small micro-cracks are found at a fluence of 2 × 1016 ions/cm2, the formation of graded layers is obtained at the highest fluence of 5 × 1016 ions/cm2 owing to ballistic intermixing and diffusion of the constituents. Detailed investigation suggests that a significant amount of Ti atoms is diffused in AZO by a complete deterioration of the AZO/TiO2 matrix at the highest fluence.

Computational insights into electronic, magnetic and optical properties of Mn(II)-doped ZnTe with and without vacancy defects

First principles calculations have been performed to investigate the optoelectronic and magnetic properties of Mn(II); ZnTe DMS with and without native defects using first principle calculations. Our results find that anti-ferromagnetic coupling dominates in the pure Mn(II)-doped ZnTe system due to super-exchange (SE) mechanism. The impact of p-type and n-type defects on magnetic coupling in Mn(II)-doped ZnTe were discussed and we found that p-type defect such as Zn vacancy defects play important role in stabilization of FM state due to the formation of bound magnetic polaron (BMP) while n-type defect such as Te vacancy defect does not affect the ground state of Mn(II); ZnTe. The magnetic coupling of Mn(II) spins in the absence and presence of Zn vacancy were explained on the basis of phenomenological band structure model. The optical absorption spectra of pure ZnTe and Mn(II); ZnTe with and without vacancies have been investigated and we found that single Mn(II)-doping in the lattice of ZnTe generates an absorption band at energy around 2.02 eV, which is assigned to intra-band d-d transitions of Mn(II) dopant. The band at energy around 0.44 eV in the absorption spectrum of Mn(II)-doped ZnTe with Zn-vacancy may be due to the acceptor states produced by Zn vacancy at Fermi level and band around 1.6 eV in the spectrum of Te vacancy defect system are related to the donor states produced by Te vacancy defect. Moreover, the correlation of magnetic coupling with intra-band d-d transition bands and fundamental bandgaps of ZnTe were also discussed and it was found that intra-band transition peak of Mn(II) ions and optical band gap of ZnTe are blue-shift in AFM coupled Mn(II) ions and are red-shift in FM coupled ions system. Our present findings highlight the worthwhile half-metallic properties of Mn(II)-doped ZnTe, which can be obtained via Zn vacancy defect engineering; this can find broad applications for the fabrication of optoelectronic and spintronic devices.

First-principle study of the effect of point defects on the activity, carrier lifetime, and photocatalytic performance of ZnO:(S/Se/Te) system

The effect of S/Se/Te-doped ZnO system on photocatalytic performance has been extensively studied. However, theoretical computational studies on S/Se/Te-doped ZnO systems containing O or Zn vacancies are lacking. Previous theoretical computational studies have also ignored the problem of unintentional introduction of H-interstitial impurities in the semiconductor fabrication process in a vacuum environment. In this paper, first-principle study is used to investigate S/Se/Te-doping and the vacancy (VO or VZn) and H gap coexistence on the photocatalytic properties of ZnO. The results showed that the Zn35SHiO35 system has the best hole life, strong activity, obvious red shift of absorption spectrum, and strong oxidation reaction. This has good theoretical reference value to be used as a photocatalyst for oxidative reaction to decompose water to produce H2.

Defect-Enriched ZnO/ZnS Heterostructures Derived from Hydrozincite Intermediates for Hydrogen Evolution under Visible Light.

Introducing defect engineering into ZnO/ZnS heterojunction photocatalysts is an effective method to simultaneously improve their visible light performance and photocatalytic efficiency. Herein, a defect-enriched ZnO/ZnS heterostructure photocatalyst was synthesized through a hydrozincite [Zn5 (OH)6 (CO3 )2 ] intermediate-deriving reaction. The mechanism analysis showed that there were interstitial Zn and Zn vacancies in the hydrozincite-derived ZnO, while S vacancies and interstitial S and Zn vacancies were formed in ZnS components after calcination. These specific defect states endowed visible light response ability to both ZnO and ZnS components in the ZnO/ZnS photocatalysts. Under visible light irradiation, the photocatalytic hydrogen evolution rate of ZnO/ZnS reached 11.68 mmol h-1 g-1 , and under simulated sunlight irradiation, the best photocatalytic hydrogen evolution rate could reach 27.94 mmol h-1 g-1 , which was much higher than most previous reports. The analysis of energy band structure and photodeposition showed that the photocatalytic reduction sites were mainly on ZnS, and the photocatalytic reaction mainly followed the typical Z-type mechanism. This work presents a simple and low-cost method for the preparation of defects-enriched ZnO/ZnS-based photocatalytic materials with high photocatalytic activity and stability.

DFT insights into the selective NH3 sensing mechanism of two dimensional ZnTe monolayer

Exploring novel NH3 sensing materials is crucial in chemical industries, fertilizing plants and medical fields. Herein, for the first time, the NH3 sensing behaviors and sensing mechanisms of two dimensional (2D) ZnTe monolayer are systematically investigated by density functional theory calculations. It is shown that 2D ZnTe monolayer exhibits excellent selective NH3 sensing properties. (220) crystal facet of ZnTe possesses a higher NH3 adsorption energy (−1.59 eV) and a larger charge transfer (0.195e) than (111) and (311) crystal facets. The positive charges could enhance NH3 sensing while the negative charges could reduce NH3 sensing. The NH3 adsorption strengths are significantly improved in O2 atmosphere while it is negligibly affected by N2 atmosphere and H2O atmosphere. Moreover, the presence of Zn vacancy and Fe, Co, Ni doping could improve the NH3 sensing of ZnTe. Additionally, the experimental results confirms that ZnTe possesses a low detection limit of 0.1 ppm NH3. These theoretical predictions and experimental results present a wide range of possibilities for the further development of ZnTe monolayer in NH3 sensing fields.

Electronic origin of phase stability in Mg–Zn–Y alloys with a long-period stacking order

The origin of the phase stability of 18R Mg–Zn–Y alloys with a long-period stacking order (LPSO) is studied using first-principles calculations. We calculate the heat of formation as a function of the number of Zn vacancies to discuss the role of Zn atoms. The calculated convex hull indicates that the Zn atoms in the LPSO alloys are stable even if they number about half of the Y atoms. The bonding state with Zn p orbitals leads to the stability of the LPSO structure because the partial density of states of Mg nearest to the solute cluster forms a valley structure.

Effects of coexistence of Mo and Zn vacancies with different valence states and interstitial H on the magneto-optical properties of ZnO: First-principles calculations

Research progress has been achieved on the influence of transition metal Mo doping and Zn vacancy coexistence on the magnetic and optical properties of ZnO. However, the interstitial H impurity in the Mo-doped ZnO system has been neglected. In this work, first principles were used to calculate the effects of the coexistence of different valence states of Mo and Zn vacancies and interstitial H on the magneto-optical properties of ZnO under the framework of density functional theory. Magnetic results showed that when Mo and Zn vacancies have +6 and 0 valences, respectively, the Zn22Mo6+O24(VZn0) system without interstitial H shows the largest magnetic moment and strongest magnetism. In the doped system, the local electrons of the spin-polarized O-2p orbital behave as acceptors near the valence band maximum, and the itinerant electrons behave as donors near the conduction band minimum. The itinerant electrons of the O-2p orbital adjacent to the Zn vacancy mainly contribute to the magnetic properties of the Zn22Mo6+O24(VZn0) system, and they are most beneficial to the design and preparation of new ZnO-based dilute magnetic semiconductors. Analysis of optical properties found that the Zn22Mo6+HiO24(VZn0) system with interstitial H have the easiest separation of electron–hole pairs, the highest mobility, the longest relaxation time, and the strongest built-in electric field when the Mo and Zn vacancies have +6 and 0 valences, respectively. Therefore, this system has the longest carrier lifetime and best activity. In addition, the absorption spectrum of the Zn22Mo6+HiO24(VZn0) system shows the most remarkable red shift in the visible and near-infrared regions. When pH = 0/7, the Zn22Mo6+HiO24(VZn0) system shows the strongest photocatalytic reduction ability. Given its carrier lifetime and activity, absorption spectrum, and redox ability, the Zn22Mo6+HiO24(VZn0) system is relatively the best for the design and preparation of new ZnO-based photocatalysts.

First-principle study of the effects of Ni doping and point vacancy on the magnetic and absorption spectrum and itinerant electron properties of ZnO

At present, determining which system contains the characteristics of itinerant electrons is unclear by considering the coexistence of Ni doping and O vacancies or Zn vacancies in the ZnO system. The effects of Ni doping and point vacancy on the magnetic and absorption spectra and itinerant electronic properties of ZnO were studied by using first principles. Results show that the binding energy of Zn30NiO32 and Zn31NiO31 systems are large, and the systems are stable. The Zn30NiO32 system containing the O1−-2p state has the characteristics of itinerant electrons. The Zn31NiO31 system has no characteristics of itinerant electrons. The Zn31NiO31 system has room temperature ferromagnetism. The more the oxygen vacancy and the increase in Ni atom doping ratio, the higher the increase in the total magnetic moment of the doped system. This condition is consistent with bound magnetopolaron theory.

First-principle study of new insights on the magnetic mechanism of ZnO through rare-earth Nd doping and Zn vacancies

Theoretical and experimental studies on the magnetic mechanism of Nd doping or Nd doping and Zn vacancies on ZnO have been reported. However, the magnetic source and mechanism of the doping system are controversial. Thus far, no reasonable theoretical explanation exists. First principles can solve such problems. In this study, the first principles are used to investigate the influence of Nd doping or Nd doping and Zn vacancies on the magnetic source and mechanism of ZnO based on the generalized gradient approximation plane wave supersoft pseudopotential method under the framework of spin density functional theory. The calculation results show that the formation energy of the Zn15NdO16 system or the Zn14NdO16 system is smaller and the doping is easier under the O-rich condition than those under the Zn-rich condition. Both doping systems have high binding energy and high stability. The study found that the magnetism of the Zn15NdO16 system is mainly produced by the spin polarization of the s, p, d, and f states of a single Nd3+ ion. This phenomenon is consistent with the mechanism by which a single ion in a compound produces magnetism. The magnetism of the Zn14NdO16 system is produced not only by the double exchange of the p, d, and f state itinerant electrons of a single Nd3+ ion but also by the d and f state exchange mediated of the O1−-2p state itinerant electrons. This finding is consistent with the explanation of the carrier-mediated double exchange mechanism. The new insights on the magnetic origin and mechanism of doped Nd or doped Nd and Zn vacancy coexisting ZnO mediated by itinerant electron have a leading role in studying similar dilute magnetic semiconductors.