Nitrogen-doped Zinc Oxide Thin Films Research Articles

Effect of concentration on the properties of nitrogen-doped zinc oxide thin films grown by electrodeposition

Zinc oxide is one of the most researched semiconductors owing to the outstanding properties that make it useful in various industrial applications, such as solar cells and other optoelectronics. In this work, ZnO thin films were prepared in five different concentrations and doped with four nitrogen atoms from triethylene tetramine (TETA) to fabricate a ZnO for optoelectronic applications using an electrodeposition technique. The doped ZnO thin films were synthesized and deposited on ITO glass substrates. The deposited thin films were annealed at 400°Cfor 60min in a furnace under the same conditions. The thin films' optical, electrical, and surface morphological properties were characterized using UV–Vis Spectrophotometer, Four Point Probe (FPP), and Scanning Electron Microscope (SEM), respectively. The optical properties confirmed the film's suitability for various transparent device applications with a high optical transmittance of about 90% at the wavelength between 250 and 950 nm. The optical band gaps of 3.25 eV to 3.50 eV were obtained at ZnO concentrations from 0.2 M to 1.0 M. The SEM images depicted a polycrystalline nature of the films with irregular nanoparticle shapes across the substrates. Electrical results established the high conductivity of nitrogen-doped ZnO thin films, thereby making the thin films suitable as transparent conducting oxides for devices such as solar cells and optoelectronics.

Opto-electronic properties of solution-processed zinc oxide thin films: role of solvents and doping

Undoped zinc oxide (ZnO) and nitrogen-doped zinc oxide (NZO) thin films were prepared on transparent conducting oxide-coated glass substrates by employing sol–gel technique. The effect of different solvents and nitrogen doping on the optical, structural, and electrical properties was investigated by UV–visible absorption spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), profilometry, and Hall effect studies. ZnO films yielded transmittance above 85% and the bandgap of ZnO thin films decreased with doping. XRD pattern confirmed hexagonal wurtzite structure of ZnO. NZO thin films were found to be in the nano-thin film phase with thickness of 40 nm. Hall effect studies yielded carrier concentration of 1.2 × 1015 cm−3 and 2.03 × 1014 cm−3, respectively, for undoped and doped ZnO thin films. The changes in vibrational modes of ZnO due to nitrogen doping were detected using Fourier transform infrared (FTIR) analysis. It was found that p-type doping, leading to an improved surface morphology, led to a reduction in optical bandgap and an increased charge carrier mobility. The choice of the solvent was found to have a profound influence on the surface morphology, optical bandgap, tail states distribution, and charge carrier mobility.

TECHNOLOGY GROWTH, MORPHOLOGICAL, STRUCTURAL, ELECTRICAL AND OPTICAL PROPERTIES OF NITROGEN DOPED ZINC OXIDE THIN FILM ON POROUS GALLIUM NITRIDE TEMPLATE

Gallium nitride (GaN) is susceptible of producing efficient display and lighting devices. Low cost hybrid heterostructured lighting devices are developed by combining zinc oxide (ZnO) with GaN that has gained much more research interest, nowadays. Porous GaN receives a great deal of attraction by its excellent and improved properties compared with its bulk counterpart. Several potential applications have been realized, including for serving as a strain-relaxed substrates for the growth of superior quality heteroepitaxial thin films and it is quite interesting. UV assisted photo electrochemical etching nanostructuring technique was utilized for the development of GaN porous structure in this study. Nitrogen is regarded as a good candidate for acceptor doping in zinc oxide by the availability of its gaseous state compared with the other available p-type doping sources. Nitrogen doped ZnO thin film was grown on the resultant porous GaN template using radio frequency magnetron sputtering technique at room temperature. The morphological, structural and optical properties of the fabricated porous nanostructure as well as the grown nitrogen doped ZnO thin films were studied. It was found that the grown nitrogen doped ZnO thin film exhibited p-type conductivity, determined by Hall measurements and the obtained results were presented.

High quality nitrogen-doped zinc oxide thin films grown on ITO by sol–gel method

Highly transparent N-doped ZnO thin films were deposited on ITO coated corning glass substrate by sol–gel method. Ammonium nitrate was used as a dopant source of N with varying the doping concentration 0, 0.5, 1.0, 2.0 and 3.0at%. The DSC analysis of prepared NZO sols is observed a phase transition at 150°C. X-ray diffraction pattern showed the preferred (002) peak of ZnO, which was deteriorated with increased N concentrations. The transmittance of NZO thin films was observed to be ~88%. The bandgap of NZO thin films increased from 3.28 to 3.70eV with increased N concentration from 0 to 3at%. The maximum carrier concentration 8.36×1017cm−3 and minimum resistivity 1.64Ωcm was observed for 3at% N doped ZnO thin films deposited on glass substrate. These highly transparent ZnO thin films can be used as a window layer in solar cells and optoelectronic devices.

Interstitial zinc clusters in zinc oxide

Doped zinc oxide (ZnO) exhibits anomalous Raman modes in the range of 270 to 870 cm${}^{\ensuremath{-}1}$. Commonly, the resonance at 275 cm${}^{\ensuremath{-}1}$ is attributed to the local vibration of Zn atoms in the vicinity of extrinsic dopants. We revisit this assignment by investigating the influence of isotopically purified zinc oxide thin films on the frequency of the vibrational mode around 275 cm${}^{\ensuremath{-}1}$. For this purpose, undoped and nitrogen-doped ZnO thin-films with Zn isotope compositions of natural Zn, ${}^{64}$Zn, ${}^{68}$Zn, and a 1:1 mixture of ${}^{64}$Zn and ${}^{68}$Zn were grown by pulsed laser deposition. The isotopic shift and the line shape of the Raman resonance around 275 cm${}^{\ensuremath{-}1}$ are analyzed in terms of three different microscopic models, which involve the vibration of (i) interstitial zinc atoms bound to extrinsic defects, (ii) interstitial diatomic Zn molecules, and (iii) interstitial zinc clusters. The energy diagram of interstitial Zn-Zn bonds in a ZnO matrix is derived from density functional theory calculations. The interstitial Zn-Zn bond is stabilized by transferring electrons from the antibonding orbital into the ZnO conduction band. This mechanism facilitates the formation of interstitial Zn clusters and fosters the common $n$-type doping asymmetry of ZnO.

Nitrogen-doped zinc oxide thin films biosensor for determination of uric acid

Nitrogen-doped zinc oxide thin films (ZnO:N) have been realized as a potential matrix for the development of a uric acid biosensor. The correlation between the change in property of the ZnO film with N doping concentration and its biosensing response has been studied. The nitrogen dopant in a ZnO film alters its defects profile, thus improving the charge transfer characteristics and resulting in an enhanced peak oxidation current in the cyclic voltammogram in comparison to that of the pure ZnO film. The studies reveal that the bio-electrode based on the nitrogen-doped ZnO thin film matrix exhibits better sensitivity (1.1 mAmM(-1)cm(-2)) with linearity over a wide range (0.05 mM to 1.0 mM) of uric acid concentration. A comparatively low value (0.10 mM) of the Michaelis-Menten constant (Km) indicates high affinity of the immobilized uricase towards uric acid. The proposed ZnO:N thin films matrix-based uric acid-biosensor has good reproducibility, a long shelf-life (20 weeks) and high selectivity.

Effect of substrate temperature on the properties of pyrolytically deposited nitrogen-doped zinc oxide thin films

Abstract The effect of substrate temperature (Ts) on the properties of pyrolytically deposited nitrogen (N) doped zinc oxide (ZnO) thin films was investigated. The Ts was varied from 300 °C to 500 °C, with a step of 50 °C. The positive sign of Hall coefficient confirmed the p-type conductivity in the films deposited at 450 °C and 500 °C. X-ray diffraction studies confirmed the ZnO structure with a dominant peak from (1 0 0) crystal plane, irrespective of the variation in Ts. The presence of N in the ZnO structure was evidenced through X-ray photoelectron spectroscopy (XPS) analysis. The obtained high N concentration reveals that the 450 °C is the optimal Ts. Atomic force microscope (AFM) analysis showed that the surface roughness was increased with the increasing Ts until 400 °C but then decreased. It is found that the transmittance of the deposited films is increased with the increasing Ts. The optical band gap calculated from the absorption edge showed that the films deposited with Ts of 300 °C and 350 °C possess higher values than those deposited at higher Ts.

Deposition and Characterisation of Nitrogen-Doped Zinc Oxide Thin Films by MOCVD Using Zinc Acetate—Ammonium Acetate Precursor

The synthesis and comprehensive analysis of nitrogen-doped zinc oxide thin films grown from a compound precursor of zinc acetate and ammonium acetate has been reported. The precursor was processed in different ratios of the zinc acetate-ammonium acetate additives, and each combination was used to deposit a thin film using metalorganic chemical vapour deposition (MOCVD) method. The produced thin films were characterised using Rutherford backscattering (RBS) spectroscopy, uv-visible spectrometry, x-ray diffractometry, four point probe measurements and optical microscopy. The deposited thin films showed a fairly consistent zinc:oxygen:nitrogen ratio of 4.4:3.7:1, the film structures were quasicrystalline and the sheet resistivities were high, while other familiar characteristics like optical transmittance, bandgap, thermal stability, etc. were maintained in the grown films. Applications in device fabrication and active sensor devices were hence envisaged as the emergent potentials of the thin films.

Evaluation of Acceptor Binding Energy of Nitrogen-Doped Zinc Oxide Thin Films Grown by Dielectric Barrier Discharge in Pulsed Laser Deposition

In this research, nitrogen (N)-doped zinc oxide (ZnO) thin films have been grown on a sapphire substrate by dielectric barrier discharge (DBD) in pulsed laser deposition (PLD). DBD has been used as an effective way for massive in-situ generation of N-plasma under conventional PLD process conditions. Low-temperature photoluminescence spectra of N-doped ZnO thin films provided near-band-edge emission after a thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound excitation peak () that indicated acceptor doping of ZnO with N. The acceptor binding energy of the N acceptor was estimated to be approximately 145 MeV based on the results of temperature-dependent photoluminescence (PL) measurements.

Effect of Doping on the Optical and Structural Properties of ZnO Thin Films Prepared by RF Diode Sputtering

Nitrogen-doped zinc oxide thin films (ZnO:N), and aluminum-nitrogen co-doped zinc oxide thin films (ZnO:Al:N), were deposited on Corning glass substrates by RF diode sputtering. The nitrogen (N2) content in the working gas varied from 0 to 100 %. XRD patterns revealed improving of the crystalline structure and stronger expressed c-axis preferential orientation of the aluminum-nitrogen co-doped films compared to nitrogen-doped films. The estimated crystallite size varied from 140 to 8 nm, depending on the N2 content. The transmittance spectra of ZnO:N and ZnO:Al:N films were acquired over the wavelength range of 200 < λ < 1000 nm. All nitrogen-doped and Al-N2 co-doped films were colored as a result of the increase absorption near the band edge. Optical band gap (Eg) of the ZnO:N and ZnO:Al:N thin films decreases with increase of the N2 content in the working gas.

Infrared Lattice Vibrations of Nitrogen-doped ZnO Thin Films

AbstractNitrogen (N) is the most promising p-type dopant for zinc oxide (ZnO), and its bonding state must be governed by the substitution of N atoms into anion sites. We have synthesized un-doped ZnO and N-doped ZnO thin films by utilizing a pulsed laser deposition (PLD) method. The N-doped ZnO thin film possessed shorter c-axis length than the un-doped ZnO thin film. This fact seems to be owing to that Zn-N bond length is shorter than Zn-O bond length in wurtzite structure. Besides, from the result of Fourier transform infrared (FT-IR) measurement, the absorption peak of the N-doped ZnO thin film emerged at 406 cm−1, and was attributed to transverse optical (TO) phonon of E1 mode. The infrared lattice vibrations of the N-doped ZnO thin films can be induced by the complex factors consisting of not only the decreases in reduced mass and interionic distance, but also the increase in covalency.