Sb-doped ZnO Research Articles

Ultraviolet response of ZnO nanorod/Sb-doped ZnO thin film homojunction structure prepared by all-chemically wet process

In this work, ZnO nanorod/Sb-doped ZnO thin film structure was fabricated and its relevant properties were investigated. The device was prepared by Sb-doped ZnO sol-gel spin coating technique onto ITO substrate annealed in nitrogen atmosphere followed by the hydrothermal process to obtain ZnO nanorod. The crystal structure demonstrates (002) plane dominant hexagonal wurtzite ZnO without phase impurity. The deterioration in the crystal structure of Sb-doped ZnO due to the Sb is incorporated in the ZnO lattice. The element component in each layer is confirmed by depth profile measurement. The low transmittance in the visible region is due to high reflection at the surface of the ZnO nanorod. The electrical measurement confirms that ZnO nanorod/Sb-doped ZnO thin film has p-n homojunction properties under dark conditions and 18 times higher photovoltage than the Sb-doped/undoped ZnO double layer device under UV LED irradiation due to enhanced photon harvesting of ZnO nanorod structure.

Uniform Sb doping of ZnO films with controllable morphology and enhanced optical property

In order to provide an effective and reliable approach to solving the difficulties in p-type modification of ZnO nanomaterials, in this work, we successfully synthesized ZnO films with uniform antimony distribution through low temperature aqueous growth method. The growth quality and dopant distribution of Sb-doped ZnO (SZO) films were evaluated by high-resolution micro-structural characterizations, and the growth mechanism for SZO films with various doping concentrations was discussed and revealed. Uniform and dispersive Sb distribution within SZO films contributed to the light transmittance of SZO films. The blue-shifted UV emission accompanied with weak visible light emission of SZO films were observed in room-temperature photoluminescent (PL) spectra, the rare yellow-red light emission and XPS results confirmed the existence of SbZn-related complex defects. This type of SZO films is competitive and promising for serving as the highly photo-conductive and photo-sensitive ZnO-based nanomaterials. And SZO films could be served as the basis for realizing the purpose of p-type modification with high efficiency and excellent stability.

High-performance, low-power, and flexible ultraviolet photodetector based on crossed ZnO microwires p-n homojunction

Low-power, flexible, and integrated photodetectors have attracted increasing attention due to their potential applications of photosensing, astronomy, communications, wearable electronics, etc. Herein, the samples of ZnO microwires having p-type (Sb-doped ZnO, ZnO:Sb) and n-type (Ga-doped ZnO, ZnO:Ga) conduction properties were synthesized individually. Sequentially, a p-n homojunction vertical structure photodiode involving a single ZnO:Sb microwire crossed with a ZnO:Ga microwire, which can detect ultraviolet light signals, was constructed. When exposed under 360 nm light illumination at −0.1 V, the proposed photodiode reveals pronounced photodetection features, including a largest on/off ratio of 105, responsivity of 2.3 A/W, specific detectivity of ∼6.5×1013 Jones, noise equivalent power of 4.8×10−15 W Hz−1/2, and superior photoelectron conversion efficiency of ∼7.8%. The photodiode also exhibits a fast response/recovery time of 0.48 ms/9.41 ms. Further, we propose a facile and scalable construction scheme to integrate a p-ZnO:Sb⊗n-ZnO:Ga microwires homojunction component into a flexible, array-type detector, which manifests significant flexibility and electrical stability with insignificant degradation. Moreover, the as-constructed array unit can be integrated into a practical photoimaging system, which demonstrates remarkable high-resolution single-pixel imaging capability. The results represented in this work may supply a workable approach for developing low-dimensional ZnO-based homojunction optoelectronic devices with low-consumption, flexible, and integrated characteristics.

Enhanced photoelectrochemistry water splitting based on the bi-piezoelectric Z-scheme pn heterojunction of an n-CdTe/p-ZnO nanorods array

An n-type Cd-excess CdTe (n-CdTeCd)/p-type Sb-doped ZnO nanorods (p-ZnONR,Sb)/indium tin oxide photocathode with a bi-piezoelectric Z-scheme pn heterojunction is prepared by hydrothermal method and electrodeposition for photoelectrochemistry (PEC) water splitting. At 0 V vs RHE under 100 mW cm−2 Xe lamp illumination in 0.5 M aqueous Na2SO4 stirred at 1500 rpm, the photocurrent density, H2 (O2 evolved at a Pt anode) yield, and the apparent Faradaic efficiency for this photocathode are −3.86 mA cm−2, 58.5 (28.6) μmol cm−2 h−1 and 84.7%, respectively. After examining the other similar semiconductor combinations of n-CdTeCd or p-type Te-excess CdTe (p-CdTeTe) with n-type ZnO nanorods (n-ZnONR) or p-ZnOSb,NR, the co-effects of bi-piezoelectric and pn-junction electric fields on the separation and transfer of photogenerated charges for PEC water splitting are discussed in detail. This work may help to better understand various heterojunctions and the electric-field-modulated photogenerated charges’ separation and transfer for the development of relevant fields.

Microstructures and mechanical properties of Sb-doped ZnO thin films deposited on a-plane sapphire substrates

The structural features and nanomechanical properties of ZnO and Sb-doped (1.0 at%) ZnO (SbZO) thin films deposited on a-plane sapphire substrates by radio-frequency (RF) magnetron sputtering are comparatively investigated in this study. The X-ray diffraction and atomic force microscopy analyses indicated that both ZnO and SbZO thin films were highly (002)-oriented albeit with somewhat different grain structure and surface morphologies. Nanoindentation results of both films exhibited apparent discontinuities (so-called pop-ins) in the load-displacement curves (P-h curves), while no discontinuity was observed in the unloading segment of the P-h curves. By using a Berkovich nanoindenter operating with the continuous contact stiffness measurement mode, the obtained hardness and Young's modulus of ZnO (SbZO) thin films are 7.3 ± 0.2 (8.5 ± 0.4) GPa and 259.6 ± 17.8 (327.4 ± 13.9) GPa, respectively. Furthermore, the facture toughness and fracture energy of ZnO and SbZO thin films obtained by Vickers indentation were also compared.

Boosting the piezoelectric coefficients of flexible dynamic strain sensors made of chemically-deposited ZnO nanowires using compensatory Sb doping

The piezoelectric devices made of ZnO nanowires have received a great interest in the past decade as potential nanogenerators and sensors. However, their characteristics are still limited significantly by the screening of the piezoelectric potential generated under mechanical solicitations, originating from the high density of free electrons in ZnO nanowires. In order to tackle that issue, we develop the compensatory Sb doping of ZnO nanowires grown by chemical bath deposition, both in the low- and high-pH regions using Sb glycolate and ammonia as chemical additives. The adsorption process of Sb(III) species on the positively charged surfaces of ZnO nanowires proceeds through attractive electrostatic forces, resulting in the significant incorporation of Sb dopants with an atomic ratio in the range of 0.11–0.45%. The optical properties of Sb-doped ZnO nanowires exhibit additional phonon modes related to Sb dopants in the range of 500–750 cm-1 in the Raman spectra, and some specific characteristics in the nature and intensity of radiative recombination in the cathodoluminescence spectra. Importantly, the integration of Sb-doped ZnO nanowires encapsulated in PMMA and grown on PDMS into flexible piezoelectric dynamic strain sensors is shown to drastically boost the piezoelectric charge and voltage coefficients by a factor of 2.65 and 1.91, following the significant incorporation of Sb dopants. A subsequent thermal annealing under oxygen atmosphere is revealed to further increase the piezoelectric charge and voltage coefficients by an additional factor of 1.38 and 1.49, following the activation of Sb doping and engineering of hydrogen-related defects. Two figures-of-merit are eventually derived from the piezoelectric charge and voltage coefficients and their values for flexible piezoelectric composites made of annealed Sb-doped ZnO nanowires are compared to more conventional piezoelectric materials, showing their high potential for medical devices. The present findings highlight the strategy consisting in simultaneously introducing compensatory acceptors and engineering hydrogen-related defects to reduce the screening effect, representing an additional powerful way to enhance the characteristics of the piezoelectric devices integrating ZnO nanowires.

Tuning the physical properties of Sb-doped ZnO nanopowders toward elevated photosensing and photocatalytic activity

Tuning the physical properties of Sb-doped ZnO nanopowders toward elevated photosensing and photocatalytic activity

Piezoelectricity-enhanced photoelectrochemistry synthesis of H2O2 on an Au nanoparticles modified p-type Sb-doped ZnO nanotubes array.

A p-type Sb-doped ZnO nanorods (p-ZnOSb,NR) array was hydrothermally prepared on indium tin oxide (ITO) and then etched into a p-type Sb-doped ZnO nanotubes (p-ZnOSb,NT) array by hot alkali solution. Further photodeposition of Au nanoparticles (AuNP) yielded a novel AuNP/p-ZnOSb,NT/ITO photocathode. The green synthesis of H2O2 by piezoelectricity-enhanced photoelectrochemistry and oxygen reduction reaction was studied for the first time, giving a H2O2 yield of 15.2 μmol cm-2 h-1, a photocurrent density of -1.05 mA cm-2 and a Faraday efficiency of 79.0% on this photocathode.

High-performance ultraviolet photodetector based on p-PEDOT:PSS film/p-ZnO:Sb microwire/n-Si double heterojunction

The development of high-sensitivity ultraviolet photodetectors, which can be compatible with the existing Si-based technique, is highly desirable in advanced applications. In this study, a double heterojunction ultraviolet photodetection device consisting of an ITO conductive glass covered by a layer of p-type poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) polymer film, a single p-type Sb-doped ZnO microwire (ZnO:Sb MW), and an n-type Si substrate was proposed and demonstrated. Using dimethyl sulfoxide (DMSO) and carbon nanohorn (CNHs) as treated solvent, the electrical properties of PEDOT:PSS polymer film were positively increased. Correspondingly, the treated photodetector exhibited a strongest photoresponsivity of approximately 737.8 A/W and largest external quantum efficiency (EQE) of approximately 2.6 × 105%, which were significantly higher than those of the pristine devices. Besides, the transient response manifests its highly-stable and faster photoresponse speed of rising/falling times of ∼67 μs/2.29 ms. The enhanced photoresponse properties are attributed to the increased electrical properties of the DMSO&CNHs co-treated PEDOT:PSS film. Especially, the p-p heterojunction formed at the PEDOT:PSS/ZnO:Sb heterointerface, can effectively accelerate the transport of photogenerated electron-hole pairs, thus reducing the recombination probability. The proposed double heterojunction that meeting the criteria of low-cost and eco-friendly would be a competitive option for the large-scale fabrication of high-performance ultraviolet photodetectors, which are efficient and compatible with the existing Si-based integrated circuit technology.

Enhancing transparent thermoelectric properties of Sb-doped ZnO thin films via controlled deposition temperature

ZnO is known as a wide-bandgap transparent thermoelectric material. Herein, the electronic transport and temperature-dependent thermoelectric properties of transparent Sb-doped ZnO (SZO) films are reported. The sputtered SZO films prepared at the optimum deposition temperature of 673 K show an n-type semiconducting behavior with the highest thermoelectric power factor of 406 μW/mK2 at 773 K, and a good transmittance ∼82% in the wavelength region of 400–1100 nm. It can well meet the requirements for transparent thermoelectric thin films. Through X-ray diffraction, UV–Vis, and photoluminescence analyses, the Zn2+ substitution by Sb5+ can be elucidated for significantly enhancing the Seebeck coefficient and thermoelectric power factor due to the increase of density-of-state effective mass.

Synthesis and optical properties of Sb-doped ZnO thin film by sol-gel spin coating method

Sb-doped ZnO thin films had been successfully synthesized by the sol-gel spin coating method. The results of XRD analysis of ZnO and Sb-ZnO thin films showed a hexagonal wurtize crystal structure with crystal sizes of 21,251 nm and 11.265 nm, respectively. The results of SEM analysis showed that the grain size distribution of the crystallites was round and uniform, compactly covering the substrate and almost no porosity. The percentage of Sb concentration based on EDS analysis was 3.02%. UV-Vis analysis results showed the absorbance and transmittance values of Sb-ZnO thin films were higher than the transmittance values of ZnO thin films. The energy band gaps for ZnO and ZnO:Sb thin films were 3.20 eV and 3.30 eV, respectively.

Enhanced n-butanol sensitivity and selectivity of Sb-doped ZnO–Co3O4 nanoparticles synthesized by solvothermal method

Sb-doped ZnO–Co 3 O 4 nanoparticles with excellent gas-sensing performance for n -butanol were synthesized by a simple one-step solvothermal route and annealing process. Microstructure, morphology, and element valence states were characterized by X-ray diffraction, field scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Sensing performance of Sb-doped ZnO–Co 3 O 4 composite nanoparticles for various volatile organic components was comprehensively investigated. Results show that nanocomposites exhibit high selectivity and sensitivity to n -butanol when doped with Sb at a level of 8%. Specifically, the selectivity of 8% Sb-doped ZnO–Co 3 O 4 sensor to 100 ppm n -butanol reached a response of 61.129 at optimal operating temperature of 200 °C, which is significantly higher than that of ZnO–Co 3 O 4 composite materials prepared without Sb doping. Improved sensing performance of Sb-doped ZnO–Co 3 O 4 was attributed to electronic and chemical sensitization effects of Sb as well as the formation of shallow donor complex defects.

MORPHOLOGICAL AND PHYSICAL PROPERTIES OF ZnO NANOSTRUCTURES GROWN ON Sb-DOPED ZnO SEEDING FILMS ANNEALED UNDER DIFFERENT ATMOSPHERES

In this work, morphological and physical properties of pyramid-like ZnO nanostructures fabricated on Sb-doped ZnO seeding films annealed under different atmospheres are extensively studied. The Sb-doped ZnO seeding films were first prepared by sol–gel spin coating technique onto glass substrate then annealed in nitrogen, air and argon followed by low-temperature hydrothermal process for ZnO nanostructures fabrication. The morphological results exhibit the growth of pyramid-like ZnO nanostructure with increasing density of the ZnO nanostructures. The crystal structure shows pyramid-like ZnO wurtzite hexagonal growth along the c-axis without any impurity phase. The growth of pyramid-like ZnO nanostructures is due to the high growth rate of (002) plane. Photoluminescence spectra exhibit the near-band-edge of all samples while the red emission appears in ZnO nanostructures after the hydrothermal process due to the imperfection in the crystal. The reflectance of ZnO nanostructures covers the visible region with the absorption edge of 375[Formula: see text]nm. The calculation shows the relevant energy band gaps in the range of 3.26–3.28[Formula: see text]eV. The difference in hydrothermally grown ZnO nanostructures is significantly affected by different annealing atmospheres.

Preparation and characterization of self-assembled ZnO nanowire devices: nanowire strain sensor and homogeneous p–n junction

In this work, intrinsic and p-type ZnO nanowires (NWs) have been synthesized. Pure intrinsic ZnO nanowires have been fabricated by direct oxidation method and their aspect ratio reached up to 271.3. Sb-doped ZnO nanowires were uniformly grown on Si substrates by chemical vapor deposition with diameters ranging from 0.5 to 5 μm and lengths ranging from 100 μm to 3 mm. Directional arrangement of nanowires has been realized by two self-assembly methods, pulling method and water flow method, and two kinds of ZnO nanodevices (strain sensor and homogenous p–n junction) were prepared and characterized based on the directional arranged nanowires. According to the current response of ZnO nanowire strain sensor, the deformation quantities of elastic plate under the action of external forces in orthogonal X and Y direction were calculated respectively. The ZnO nanowire homogenous p–n junction was made of two vertical Sb-doped and intrinsic ZnO nanowires. The I–V characteristic curve showed good rectification characteristics, and the forward turn-on voltage was about 10 V. However, since the current was too small due to the small carrier concentration in the ZnO single crystal, it is difficult to achieve electroluminescence at present.

Room temperature ferromagnetism in Sb doped ZnO

Using first-principle calculations, the magnetic properties of the monovacancies and the Sb-related defects including VZn, VO, SbZn, SbO, SbZn-VZn and SbZn-2VZn are studied. It is found that the isolated VZn with the charge state of 0 and −1 can contribute to ferromagnetism in ZnO material. The substitution of Sb on O sites (SbO0) also results in magnetic property. Moreover, the SbZn-2VZn complex is another defect having non-zero magnetic moment and energetically favors for the ferromagnetic state. The resultant density of states (DOS) and spin density distribution clearly show that the ferromagnetic interaction is majorly due to the O-p Zn-d and Sb-p states. To check this calculation, Sb-doped ZnO samples were grown by pulsed laser deposition with different Sb composition under P(O2) = 1.3 Pa. SQUID study showed that all of these samples are ferromagnetic at room temperature. The variation of the saturation magnetization against the Sb composition is discussed.

Recent Progress in Hybridized Nanogenerators for Energy Scavenging.

SummaryAs the world's demand for alternative energy increases, the development of green energy harvesters becomes ever more important. As a result, the creation of triboelectric (TENG), piezoelectric (PENG), and pyroelectric nanogenerators, electromagnetic generators (EMG), solar cells, and electrochemical cells is attracting interest in an effort to convert mechanical, thermal, magnetic, solar, and chemical energy into electricity. In order to take advantage of the ambient energies from our surrounding environment, the design of hybridized generator units that can simultaneously scavenge energy in a variety of forms continues to develop. These systems are being considered to satisfy the energy needs of a range of electronic devices and adapt to a variety of working environments. This review demonstrates the latest progress in hybridized nanogenerators in accordance with their structure, operating principle, and applications. These studies demonstrate new approaches to developing hybrid techniques and novel assemblies for efficiently harvesting environmental energy from a number of sources.

New inversion boundary structure in Sb-doped ZnO predicted by DFT calculations and confirmed by experimental HRTEM

Today, ab-initio calculations are becoming a powerful tool to perform virtual experiments that have the capacity to predict and to reproduce experimentally observed non-periodic features, such as interfaces, that are responsible for quantum properties of materials. In our paper we investigate 2D quantum-well structures, known as inversion boundaries (IB). Combining atomistic modeling, DFT calculations and HRTEM analysis we provide a new fundamental insight into the structure and stability of Sb-rich basal-plane IBs in ZnO. DFT screening for potential IB model was based on the known stacking deviations in originating wurtzite structure. The results show that the model with Aβ−Bα−AβC−γB−βC sequence (IB3) is the most stable translation for Sb-doping, as opposed to previously accepted Aβ−Bα−AβC−γA−αC (IB2) model. The key to the stability of IB structures has been found to lie in their cationic stacking. We show that the energies of constituting stacking segments can be used to predict the stability of new IB structures without the need of further ab-initio calculations. DFT optimized models of IBs accurately predict the experimentally observed IB structures with lateral relaxations down to a precision of ~1 pm. The newly determined cation sublattice expansions for experimentally confirmed IB2 and IB3 models, ΔIB(Zn-Zn) are +81 pm and +77 pm, whereas the corresponding O-sublattice contractions ΔIB(O-O) are –53 pm and –57 pm, respectively. The refined structures will help to solve open questions related to their role in electron transport, phonon scattering, p-type conductivity, affinity of dopants to generate IBs and the underlying formation mechanisms, whereas the excellent match between the calculations and experiment demonstrated in our study opens new perspectives for prediction of such properties from first principles.

The origin of additional modes in Raman spectra of ZnO:Sb films

Systematic Raman spectroscopic study was conducted on the wurtzite (002) Sb-doped ZnO films grown by pulsed laser deposition with different Sb doping levels and annealed at different temperatures, with the undoped, Cu-doped and Ga-doped ZnO films for comparison. Three additional Raman modes 235 cm−1, 510 cm−1 and 534 cm−1 were observed only in the Sb-doped ZnO samples but not in the other controls. The vibration mode 235 cm−1was associated with the SbZn-related shallow donor, which was the origin of the n+-conductivity. The 510 cm−1 vibrational mode has been associated with HO in previous literature. However in the current study, the correlation between its intensity and the H abundance was not observed. The 534 cm−1 Raman mode was associated with a Sb-related defect. The variation of the intensities of the Raman modes 235 cm−1 and 510 cm−1 upon annealing and change of Sb composition were discussed.

Analytical Performance Analysis of CdZnO/ZnO-Based Multiple Quantum Well Solar Cell

This article presents analytical and simulation evaluation of multiple quantum well solar cells (MQWSC) with CdZnO/ZnO as the intrinsic layer, Sb-doped ZnO (SZO) as a p-type layer, and Ga-doped ZnO (GZO) as an n-type layer of the p-i-n solar cell (SC). The material parameters used in this article are obtained from the experimental reports on the properties of ZnO and CdZnO thin films grown by dual-ion-beam sputtering (DIBS). The American Society for Testing and Materials (ASTM) standards data sheets have been utilized for attaining photon flux density instead of the blackbody radiation formula. The analytically obtained results show good agreement with the simulated results obtained by the ATLAS simulation tool. The variation of device performance parameters is examined for thermal stability. The results show that, for the proposed ZnO-based MQWSC, the open-circuit voltage ( ${V}_{{\text {oc}}}$ ) has a negative temperature coefficient (−2.63 mV/°C), and short-circuit current density ( ${J}_{{\text {sc}}}$ ) and conversion efficiency ( ${\eta }$ ) have positive temperature coefficients of $2.43\times 10^{{-{3}}} \,\,{\text {mA}/\text {cm}^{{{2}}}\cdot ^{\circ }}\text{C}$ and $2.91\times 10^{{-{3}}}$ %/°C, respectively. Further, the device performance has been explored for variation in the number of quantum wells. The results present that an increase in the number of quantum wells has a negative impact on the performance parameters of ZnO-based MQWSC.

Cation impurity-defect complex induced ferromagnetism and hopping conduction in Sb-doped ZnO synthesized under high pressure

Sb-doped p-type ZnO was synthesized using the high-pressure method with a quasi-equilibrium thermodynamic process. Room temperature ferromagnetism was observed in Sb-doped ZnO. The ferromagnetic coupling was found to be associated with zinc vacancies (VZn) induced by Sb doping, which was supported by a strong ultraviolet emission peak relevant to VZn in low temperature photoluminescence. Hall effect measurements indicated that the Sb-doped ZnO with Sb content of 3.4 at% had a hole concentration of 1.4 × 1020 cm−3 and low resistivity of 7.4 × 10−2 Ω cm. Temperature-dependent resistance measurements suggest that the electrical conduction mechanism of the Sb-doped ZnO changed from thermal activation model and nearest-neighbor hopping (NNH) conduction at high temperature to Mott variable-range hopping (VRH) and Efros–Shklovskii VRH conduction at low temperature. First-principles calculations demonstrated that the Sb impurity substituting Zn (SbZn) combines two VZn defects to form acceptor-like impurity-defect complex of SbZn–2VZn in ZnO due to the coulomb attraction. The SbZn–2VZn complex in Sb-doped ZnO are strongly correlated with ferromagnetic stability and lead to the Mott and Efro–Shklovskii VRH conduction at low temperature due to the localization of carriers at the complex impurity band.