Sb-doped ZnO Research Articles

Cross-section imaging and p-type doping assessment of ZnO/ZnO:Sb core-shell nanowires by scanning capacitance microscopy and scanning spreading resistance microscopy

ZnO/ZnO:Sb core-shell structured nanowires (NWs) were grown by the metal organic chemical vapor deposition method where the shell was doped with antimony (Sb) in an attempt to achieve ZnO p-type conduction. To directly investigate the Sb doping effect in ZnO, scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were performed on the NWs' cross-sections mapping their two dimensional (2D) local electrical properties. Although no direct p-type inversion in ZnO was revealed, a lower net electron concentration was pointed out for the Sb-doped ZnO shell layer with respect to the non-intentionally doped ZnO core, indicating an evident compensating effect as a result of the Sb incorporation, which can be ascribed to the formation of Sb-related acceptors. The results demonstrate SCM/SSRM investigation being a direct and effective approach for characterizing radial semiconductor one-dimensional (1D) structures and, particularly, for the doping study on the ZnO nanomaterial towards its p-type realization.

Structural and optical characterization of Sb-doped ZnO co-sputtered thin films

This paper reports the structural and optoelectronics properties of prepared pure and Sb-doped ZnO nanoparticles using the co-sputtering technique. The phase purity and crystallite size of synthesized ZnO and Sb-doped nano-sized particles were characterized and examined using X-ray diffraction and scanning electron microscopy. The elemental analysis was examined by using energy-dispersive X-ray spectroscopy (EDX). Optical properties were carried out by employing UV-visible spectroscopy to study the optoelectronic properties of Sb-doped ZnO thin film. These films are highly transparent in the visible region and exhibit a steep absorption edge at 380 nm. The average value of the optical gap belonging to the thin films deposited under different conditions is 3.17 eV. The refractive index (n) behaves as normal dispersion and decreases with increasing both the rate of flow and thickness. The dispersion energy, single oscillator energy, and optical conductivity increase with increasing the rate of flow of argon.

Low-Temperature Facile Synthesis of Sb-Doped p-Type ZnO Nanodisks and Its Application in Homojunction Light-Emitting Diode.

This study explores low-temperature solution-process-based seed-layer-free ZnO p-n homojunction light-emitting diode (LED). In order to obtain p-type ZnO nanodisks (NDs), antimony (Sb) was doped into ZnO by using a facile chemical route at 120 °C. The X-ray photoelectron spectra indicated the presence of (SbZn-2VZn) acceptor complex in the Sb-doped ZnO NDs. Using these NDs as freestanding templates, undoped n-type ZnO nanorods (NRs) were epitaxially grown at 95 °C to form ZnO p-n homojunction. The homojunction with a turn-on voltage of 2.5 V was found to be significantly stable up to 100 s under a constant voltage stress of 5 V. A strong orange-red emission was observed by the naked eye under a forward bias of 5 V. The electroluminescence spectra revealed three major peaks at 400, 612, and 742 nm which were attributed to the transitions from Zni to VBM, from Zni to Oi, and from VO to VBM, respectively. The presence of these deep-level defects was confirmed by the photoluminescence of ZnO NRs. This study paves the way for future applications of ZnO homojunction LEDs using low-temperature and low-cost solution processes with the controlled use of native defects.

An Sb-doped p-type ZnO nanowire based random laser diode

An electrically pumped Sb-doped ZnO nanowire/Ga-doped ZnO p–n homojunction random laser is demonstrated. Catalyst-free Sb-doped ZnO nanowires were grown on a Ga-doped ZnO thin film on a Si substrate by chemical vapor deposition. The morphology of the as-grown titled nanowires was observed by scanning electron microscopy. X-ray photoelectron spectroscopy results indicated the incorporation of Sb dopants. Shallow acceptor states of Sb-doped nanowires were confirmed by photoluminescence measurements. Current–voltage measurements of ZnO nanowire structures assembled from p- and n-type materials showed a typical p–n diode characteristic with a threshold voltage of about 7.5 V. Very good photoresponse was observed in the UV region operated at 0 V and different reverse biases. Random lasing behavior with a low-threshold current of around 10 mA was demonstrated at room temperature. The output power was 170 nW at 30 mA.

Study on influences of Sb doping content on the defects of ZnO film by photoluminescence (PL) spectrum and raman scattering spectrum

Sb-doped ZnO thin films with different values of Sb concentrations are deposited on glass substrate by using spin-coating technique. The influences of Sb doping content on the microstructural, photoluminescence and Raman properties of ZnO film are systematically investigated by X-ray diffraction (XRD), transmission spectrum, photoluminescence (PL) spectrum and Raman scattering spectrum. The results indicate that ZnO thin film doped with Sb exhibits a hexagonal wurtzite structure with preferred c-axis orientation. The strong violet emission peak located at 3.11 eV is observed in the Sb-doped ZnO thin film by photoluminescence. Conbining the Raman scattering spectrum with photoluminescence, it is concluded that the strong violet emission peak related to SbZn-O complex defect in ZnO:Sb film.

Sb substitution into ZnO nano-composite: Ferromagnetic behavior

Properties of particles whose dimensions are of the nanoscale can be quite different from those of bigger dimension particles. We investigate here the effects of doping Sb5+ ions into ZnO nanorods (NR's) on the formation of magnetic moments. The pure ZnO and Sb-doped ZnO NR's were grown by the hydrothermal process. The fabricated nanorods were then studied using X-ray diffraction (XRD), ultraviolet–visible light spectroscopy (UV–vis), Scanning Electron Microscopy (SEM), Photoluminescence (PL) Spectrometer and Vibrating Sample Magnetometer (VSM) spectrometry. Substitution of Sb into the ZnO leads to the formation of a defect (SbZn+2VZn) complex state which can capture the oxygen p-orbital electrons of the oxygen atoms and form a spin polarized state. The PL was used to monitor the defect formation in the ZnO NR's when the Sb is doped in. As more Sb was doped in, the visible blue portion of the PL spectrum decreased while the visible red portion increased. Magnetization measurements (VSM) showed that the pure ZnO NR's possessed a magnetic moment which initially increased as Sb is doped in but decreased as more Sb was doped in. We obtain a value of 1.015memu/g for the saturation magnetization of the pure ZnO nanorod.

Fabrication of Sb-doped p-type ZnO Thin Films by Pulsed Laser Deposition

In this work, antimony (Sb)-doped p-type ZnO thin films on c-plane sapphire substrates have been fabricated by pulsed laser deposition, with Sb2O3 used as the dopant source. The effects of ambient gas or growth temperature on the fabrication process were investigated. The nitrogen ambient was found to be essential to achieve the p-type conduction. The Hall-effect measurements at room temperature indicated that the ZnO thin films doped with 3 at.% Sb and grown at 600 °C under N2 atmosphere exhibited p-type behavior with a hole concentration of 1.17×1017 cm−3, hole mobility of 0.63 cm2/V·s, and resistivity of 84.51 Ω·cm. X-ray diffraction and scanning electron microscopy revealed good crystallization and homogenous surface morphology of the ZnO:Sb thin films. The optical transmission spectrum of the ZnO:Sb thin films indicated that the energy band gap value was around 2.9 eV. Post-growth annealing at 650 oC converted the p-type conduction to n-type. This result implied that Sb-doping and annealing treatment were dominant factors determining native and extrinsic defects in the ZnO thin films, and thus controlling their electrical conductivity properties.

Nanobranched ZnO Structure: p-Type Doping Induces Piezoelectric Voltage Generation and Ferroelectric-Photovoltaic Effect.

p-Type Sb-doped ZnO nanobranched films are synthesized by an innovative approach: sputtered nanobranched Zn films are impregnated in an Sb-based solution and thermally treated to simultaneously oxidize Zn and insert the Sb dopant in the wurtzite structure. Sb doping of ZnO results in a rise of the piezoelectric voltage generation and, for the first time, ferro­electric properties and a ferroelectric-driven photovoltaic effect.

Origin of p-type conductivity of Sb-doped ZnO nanorods and the local structure around Sb ions

To probe the origin of p-type conductivity in Sb-doped ZnO, a careful and detailed synchrotron radiation study was performed. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy investigations provided the evidence for the formation of the complex defects comprising substitution Sb ions at Zn sites (SbZn) and Zn vacancies within the Sb-doped ZnO lattice. Such complex defects result in the increases of Sb-O coordination number and the Sb valence and thereby lead to the p-type conductivity of Sb-doped ZnO. The back-gate field-effect-transistors based on single nanorod of Sb-doped ZnO were constructed, and the stable p-type conduction behavior was confirmed.

Influence of Sb valency on the conductivity type of Sb-doped ZnO

Sb-doped ZnO thin films with different Sb concentrations were grown by varying mole ratio of Sb precursor to Zn precursor during the growth process using metal organic chemical vapor deposition technology. It was found that the valency of Sb changed from Sb3+ to Sb5+ in Sb doped ZnO with increasing mole ratio of Sb precursor to Zn precursor. The p-type ZnO was obtained only for ZnO films with lower mole ratio of Sb precursor. The conductivity type of Sb doped ZnO was changed from p-type to n-type accordingly. These results were suggested that the valency of Sb in ZnO is more important for obtaining p-type Sb doped ZnO thin films.

Enhanced piezo-humidity sensing of Sb-doped ZnO nanowire arrays as self-powered/active humidity sensor

Room-temperature self-powered/active humidity sensing has been realized from Sb-doped ZnO nanowire (NW) arrays by coupling their piezoelectric and gas sensing characteristics. The piezoelectric output of the device acts as both the power source and the response signal against relative humidity (RH). Upon exposure to 70% RH, the piezoelectric output of Sb-doped ZnO NWs decreases from 1.35V (10% RH) to 0.22V, and the response is 83.70 (much higher than that of undoped ZnO).

Hot probe measurements of n-type conduction in Sb-doped ZnO microwires

The charge carriers type in antimony-doped ZnO (ZnO:Sb) microwires was studied using the hot probe technique. The wires were grown by a simple thermal evaporation method. Contrary to the expected p-type behavior reported for Sb doped ZnO thin films and nanowires, our hot probe measurements of representative single Sb-doped ZnO wires show a stable n-type behavior. The hot probe technique is a simple and efficient way to determine the charge carrier type from thermoelectric measurements on a single semiconductor wire and could offer an alternative to Hall effect measurements. The technique relies on creating a temperature gradient across the wire (i.e., heating one side of the wire relative to the other) and monitoring the resulting open-circuit voltage between the two ends. We also performed Energy Dispersive X-ray Spectroscopy measurements to identify and monitor the elemental composition in these ZnO:Sb wires.

Laser doping of Sb into ZnO nanowires in the Sb nanoparticle-dispersed liquid

We succeed in fabricating Sb-doped ZnO nanowires by laser doping using Sb nanoparticles (Sb NPs). Vertically aligned ZnO nanowires with a diameter of 100 nm were synthesized by the nanoparticles-assisted pulsed laser deposition. Sb NPs were prepared by laser ablation in liquid. The average size of 50 nm Sb NPs was successfully fabricated by laser ablation in ethanol. Subsequently, laser doping was performed by irradiating Nd:YAG laser beam (355 nm) in Sb-dispersed ethanol. After laser doping, the tip of ZnO nanowires was slightly deformed into spherical shape by laser heating. A rectifying property with a threshold voltage of 4.5 V was observed between n-type ZnO nanowires and Sb-doped ZnO nanowires.

Spetroscopic ellipsometry study on electrical and elemental properties of Sb-doped ZnO thin films

Room-temperature spectroscopic ellipsometry data has been analyzed to determine the complex dielectric functions, ɛ(E) = ɛ1(E) + iɛ2(E) of as-deposited Sb-doped ZnO (SZO) thin films grown on n-Si(100) substrates by dual ion beam sputtering deposition system for different growth temperatures (Tg). The dielectric functions have been obtained from ellipsometry data analyses using Cody-Lorentz oscillator in the GenOsc model. A gradual reduction in the value of electron concentration and finally the conversion of doping characteristics from donor type to acceptor type was observed with the rise in Tg. This, in turn, resulted in the decline of broadening of ɛ1 peaks, and hence in the increase of excitonic lifetime. Optical band-gap energy was observed to decrease with increase in Tg from 200 to 300 °C, and then rise continuously with further increase in Tg. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. Hall measurement and X-ray photoelectron spectroscopy analysis confirmed that the change in the electrical conduction from n-to p-type was due to the enhancement in the value of Sb5+/Sb3+ ratio and SbZn–2VZn complex formation in SZO films.

Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation.

ZnO homojunction UV photodetector based on solution-grown Sb-doped p-type ZnO nanorods and pure n-type ZnO nanorods

The p-type Sb-doped ZnO NRs act as one of promising candidates for electronic and optoelectronic devices in the future.

Resistive switching in Ga- and Sb-doped ZnO single nanowire devices

Self-rectifying resistive switching is demonstrated in Ga-doped ZnO single nanowire device. The current is not only self-rectifying but also self-compliance for Sb-doped single nanowire devices in which multilevel resistive switching has also been achieved by using different SET voltages.

Bandgap-engineered CdxZn1 − xO nanowires as active regions for green-light-emitting diodes

A green-light-emitting diode device was fabricated based on a p-type Sb-doped ZnO segments/Cd-alloyed ZnO/n-type ZnO film/heteronanowires array structure. The structures and chemical components of the heteronanowire sample were studied by energy dispersive spectrometer, x-ray photoelectron spectrometer, etc, from which the statuses of Cd and Sb in the sample were confirmed. Spatially resolved photoluminescence measurement on a single heteronanowire revealed a large bandgap shift in the CdxZn1 − xO active region. In electroluminescence characterizations, the device showed that the green emission was centered at 550 nm, suggesting the successful formation and functioning of the double heterojunction nanowire light-emitting diodes.

Synthesis and Characterization of Antimony-Doped Zinc Oxide Nanostructures via Microwave-Assisted Process

Sb-doped ZnO nanostructures have been deposited on to glass substrates via microwave-assisted process form Zn-Sb with different 1, 2 and 3 % by atomic weight. As the Sb/Zn mole ratio of the microwave oven materials increases, the Sb content doped in to the ZnO increases size, and the shape of the ZnO nanomaterials could be controlled via doping Sb. The structural and properties of undoped and doped ZnO were characterized by various techniques including by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV-visible spectroscopy. Finally, the controlled growth mechanism of ZnO nanomaterials was discussed in detail.

Opto-electrical properties of Sb-doped p-type ZnO nanowires

P-type ZnO nanowires (NWs) have attracted much attention in the past years due to the potential applications for optoelectronics and piezotronics. In this study, we have synthesized Sb-doped p-type ZnO NWs on Si (100) substrates by chemical vapor deposition with Aucatalyst. The Sb-doped ZnO NWs are single crystalline with high density, grown along [1-1-2] direction. The doping percentage of Sb is about 2.49%, which has been confirmed by X-ray photoelectron spectroscopy. The ZnO NW field effect transistor demonstrated its p-type characteristics. A high responsivity to ultraviolet photodetection was also observed. In addition, compared to intrinsic ZnO NWs, the conductivity of the Sb-doped ZnO NWs exhibited ∼2 orders of magnitude higher. These properties make the p-type ZnO NWs a promising candidate for electronic and optoelectronic devices.