Growth Of ZnO Thin Films Research Articles

Dependence of Structural and Optical Properties of ZnO Thin Films Grown by Sol–Gel Spin-Coating Technique on Solution Molarity

Dependence of Structural and Optical Properties of ZnO Thin Films Grown by Sol–Gel Spin-Coating Technique on Solution Molarity

Coarse‐grained approach to amorphous and anisotropic materials in kinetic Monte Carlo thin‐film growth simulations: A case study of TiO2and ZnO by plasma‐enhanced chemical vapor deposition

AbstractThe growth of TiO2and ZnO thin films is studied by means of coarse‐grained kinetic Monte Carlo simulations under conditions typically encountered in plasma‐enhanced chemical vapor deposition experiments. The basis of our approach is known to work well to simulate the growth of amorphous materials using cubic grids and is extended here to reproduce not only the morphological characteristics and scaling properties of amorphous TiO2but also the growth of polycrystalline ZnO with a good approximation, including the evolution of the film texture during growth and its dependence on experimental conditions. The results of the simulations have been compared with available experimental data obtained by X‐ray diffraction, analysis of the texture coefficients, atomic force microscopy, and scanning electron microscopy.

Study of the Effects of Annealing Temperature on the Properties of ZnO Thin Films Grown by Spray Pyrolysis Technique for Photovoltaic Applications

Study of the Effects of Annealing Temperature on the Properties of ZnO Thin Films Grown by Spray Pyrolysis Technique for Photovoltaic Applications

Investigation of the Effects of Rapid Thermal Annealing on the Electron Transport Mechanism in Nitrogen-Doped ZnO Thin Films Grown by RF Magnetron Sputtering.

Nitrogen-doped ZnO (ZnO:N) thin films, deposited on Si(100) substrates by RF magnetron sputtering in a gas mixture of argon, oxygen, and nitrogen at different ratios followed by Rapid Thermal Annealing (RTA) at 400 °C and 550 °C, were studied in the present work. Raman and photoluminescence spectroscopic analyses showed that introduction of N into the ZnO matrix generated defects related to oxygen and zinc vacancies and interstitials. These defects were deep levels which contributed to the electron transport properties of the ZnO:N films, studied by analyzing the current–voltage characteristics of metal–insulator–semiconductor structures with ZnO:N films, measured at 298 and 77 K. At the appliedtechnological conditions of deposition and subsequent RTA at 400 °C n-type ZnO:N films were formed, while RTA at 550 °C transformed the n-ZnO:N films to p-ZnO:N ones. The charge transport in both types of ZnO:N films was carried out via deep levels in the ZnO energy gap. The density of the deep levels was in the order of 1019 cm−3. In the temperature range of 77–298 K, the electron transport mechanism in the ZnO:N films was predominantly intertrap tunneling, but thermally activated hopping also took place.

Investigation of Structural and Optical Properties of ZnO Thin Films Grown on Different Substrates by Mist-CVD Enhanced with Ozone Gas Produced by Corona Discharge Plasma

This study focuses on the growth and physical properties of ZnO thin films on different substrates grown by mist-CVD enhanced with ozone (O3) gas produced by corona discharge plasma using O2. Here, O3 is used to eliminate the defects related to oxygen in ZnO thin films. ZnO thin films are grown on amorphous soda-lime glass (SLG) and single crystals SiO2/Si (100) and c-plane Al2O3 substrates at 350°C of low growth temperature. All ZnO thin films show dominant (0002) diffraction peaks from X-ray diffraction (XRD). As expected, full width at half maximum (FWHM) of (0002) is decreasing in ZnO thin films on single-crystal substrates, especially c-Al2O3 due to similar crystal structure. It is found that the strain in the films is lowest in ZnO/c-Al2O3. The surface morphologies of the thin films are studied with atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. Grown ZnO films have a hexagonal and triangular nanostructure with different nanostructure sizes depending on the used substrate types. The calculated surface roughness is dramatically decreased in ZnO/c-Al2O3 compared to the other grown structures. The confocal Raman measurements show the E2(H) peak of ZnO thin films at 437 cm−1. It is suggested that O3 gas produced by corona discharge plasma using O2 can be useful to obtain better crystal quality and physical properties in ZnO thin films.

Growth of ZnO thin films at low temperature by plasma-enhanced atomic layer deposition using H2O and O2 plasma oxidants

Growth of ZnO thin films at low temperature by plasma-enhanced atomic layer deposition using H2O and O2 plasma oxidants

Growth of ZnO Thin Film on Silicon and Glass Substrate by Pulsed Laser Deposition Technique

ZnO can be thought of a future material as it has wide range of applications starting from designing optoelectronics devices to .In this paper, i have deposited ZnO thin film on both silicon and glass substrate using pulsed laser deposition technique which comes under PVD. I studied its structural properties using XRD and absorption spectroscopy using UV Visible spectrometer. Wide band gap of ZnO makes it efficient in usingin optoelectronics application.

Growth and characterization of ZnO thin films at low temperatures: from room temperature to − 120 °C

ZnO thin films have been grown by e-beam evaporation in the range from room temperature to − 120 °C on two types of substrates, Al2O3 (0001) and Si (100). Although the ZnO/Al2O3 system has been thoroughly characterized, including optical and electrical techniques, the morphological, structural and chemical properties show no significant differences between both substrates. Thus, the general features of the ZnO growth mode at low temperature can be generalized. The relatively low growth temperatures reduce the diffusion of atoms at the surface, which leads to morphological and chemical changes. As the temperature decreases, the growth mode changes from a van der Drift model to a gradual bilayer system composed of an interfacial layer in contact with the substrate and a second columnar-based layer. This second well-ordered film disappears for the lowest temperatures while a Zn-rich interface in contact with the substrate emerges. Precisely from this interface, Zn-rich whiskers develop under the ZnO film and cause the loss of adhesion at temperatures below − 100 °C. These extreme temperatures also affect the crystal size, lattice strain, and total amount of oxygen vacancies. The behavior of the optical and electrical properties in terms of band gap, transparency, electrical resistivity, and Seebeck coefficient is discussed in the light of structural and chemical characterization. Samples grown at 0 °C exhibit an enhanced transmittance compared to those grown at room temperature while preserving similar electrical resistivity values and natural n-type doping. These results open a promising route to enhance ZnO films properties below the typical high temperature window.

Mathematical modeling and simulation of the growth of ZnO thin films in Ar/O2 plasma

Mathematical modeling and simulation of the growth of ZnO thin films in Ar/O2 plasma

Photoluminescence and time resolved photoluminescence properties in as grown ZnO thin films prepared by DC reactive sputtering for optoelectronic devices

Results of steady-state and time-resolved Photoluminescence (PL) measurements performed on ZnO thin films, deposited on (001) p-doped silicon substrate, by DC reactive sputtering technique for different growth times are presented. In all cases, two emission bands are observed. One is an exciton emission band and the second an intense and broad visible emission band.As the growth time increases, the intensity of the exciton emission decreases while that of the visible emission increases. Time-resolved PL (TRPL) measurements at the UV emission peak show a bi-exponential decay behavior. As the growth time increases, the fast and slow decay lifetimes increase together with a decrease of the amplitude ratio (AR) of the slow decay component to the rapid one due to the reduction of the non-radiative pathways when the oxygen deposition time is short. Moreover, slower rise time of the TRPL signal is observed when the growth time increases, proving the increase of the trap states density in the ZnO band gap. These results suggest that the amount of oxygen deposited as reactive gas in DC reactive sputtering technique must be optimized to improve the performance of UV light-emitting applications.

Thickness Effect on the Properties of 4% Mn‐Doped ZnO Thin Films Grown by Sol‐Gel Spin Coating Deposition

AbstractIn this study, the thickness effect of 4% Mn‐doped ZnO thin films on structural, optical, and morphological properties is investigated. The films are deposited on a glass substrate using the sol‐gel spin coating method. Phase analysis indicates that all films have a hexagonal wurtzite structure with a high preferential c‐axis orientation. All structural parameters are significantly influenced by the thickness variations. The optical analysis reveals that transmittance and band gap energy decrease with thickness. A red shift of the absorption edge is noticed. The surface morphology shows a good uniformity for all ZnO films. The surface roughness of the samples increases with film thicknesses. The photoluminescence (PL) spectra show a UV peak at 388 nm with two blue peaks at 438 and 475 nm and a weak green emission peak at 525 nm. A lower PL intensity is noticed by increasing the thickness. The obtained results exhibit similarities in behavior as other methods.

Growth, crystal structure and optical properties of Al-doped ZnO thin films

Al-doped ZnO (ZnO:Al) thin films are prepared by high-frequency magnetron sputtering method. The phase analysis and crystal structure refinement are performed using X-ray diffraction data. The mean grain size of the films was determined using the Scherrer formula. The strain and the dislocation density are also calculated. The spectral dependence of the optical transmittance of the obtained sample in the visible and near-infrared regions is studied at room temperature. The integral optical transmittance and the bandgap value of studied films are determined. The optical bandgap value of 3.26 eV is estimated. Based on the obtained experimental results, the refractive index and the high-frequency dielectric constant were determined using the ratio of Tripathy, Moss, Ravindra, and Herve–Vandamme.

Temperature-Dependent Photoluminescence of ZnO Thin Films Grown on Off-Axis SiC Substrates by APMOCVD.

The growth of high-quality ZnO layers with optical properties congruent to those of bulk ZnO is still a great challenge. Here, for the first time, we systematically study the morphology and optical properties of ZnO layers grown on SiC substrates with off-cut angles ranging from 0° to 8° by using the atmospheric pressure meta–organic chemical vapor deposition (APMOCVD) technique. Morphology analysis revealed that the formation of the ZnO films on vicinal surfaces with small off-axis angles (1.4°–3.5°) follows the mixed growth mode: from one side, ZnO nucleation still occurs on wide (0001) terraces, but from another side, step-flow growth becomes more apparent with the off-cut angle increasing. We show for the first time that the off-cut angle of 8° provides conditions for step-flow growth of ZnO, resulting in highly improved growth morphology, respectively structural quality. Temperature-dependent photoluminescence (PL) measurements showed a strong dependence of the excitonic emission on the off-cut angle. The dependences of peak parameters for bound exciton and free exciton emissions on temperature were analyzed. The present results provide a correlation between the structural and optical properties of ZnO on vicinal surfaces and can be utilized for controllable ZnO heteroepitaxy on SiC toward device-quality ZnO epitaxial layers with potential applications in nano-optoelectronics.

Influence of the Substrate, Process Conditions, and Postannealing Temperature on the Properties of ZnO Thin Films Grown by the Successive Ionic Layer Adsorption and Reaction Method.

Here, we report the effect of the substrate, sonication process, and postannealing on the structural, morphological, and optical properties of ZnO thin films grown in the presence of isopropyl alcohol (IPA) at temperature 30–65 °C by the successive ionic layer adsorption and reaction (SILAR) method on both soda lime glass (SLG) and Cu foil. The X-ray diffraction (XRD) patterns confirmed the preferential growth thin films along (002) and (101) planes of the wurtzite ZnO structure when deposited on SLG and Cu foil substrates, respectively. Both XRD and Raman spectra confirmed the ZnO and Cu-oxide phases of the deposited films. The scanning electron microscopy image of the deposited films shows compact and uniformly distributed grains for samples grown without sonication while using IPA at temperatures 50 and 65 °C. The postannealing treatment improves the crystallinity of the films, further evident by XRD and transmission and reflection results. The estimated optical band gaps are in the range of 3.37–3.48 eV for the as-grown samples. Our experimental results revealed that high-quality ZnO thin films could be grown without sonication using an IPA dispersant at 50 °C, which is much lower than the reported results using the SILAR method. This study suggests that in the presence of IPA, the SLG substrate results in better c-axis-oriented ZnO thin films than that of deionized water, ethylene glycol, and propylene glycol at the optimum temperature of 50 °C. Air annealing of the samples grown on Cu foils induced the formation of CuxO/ZnO junctions, which is evident from the characteristic I–V curve including the structural and optical data.

Comparison of Thermoelectric Properties of ZnO and ZnSnO Thin Films Grown on Si Substrate by Thermal Evaporation

In this manuscript, we compared the thermoelectric properties of ZnO and ZnSnO thin films grown on silicon (100) substrate. We have evaporated Zn and Sn+Zn metal powders were evaporated in vacuum tube furnace alternatively, under same experimental conditions for the growth of ZnO and ZTO respectively. After the deposition, these grown films were cut into pieces and post growth annealed at different annealing temperatures from 600oC to 800oC in the air using programmable muffle furnace. Seebeck and Hall data suggested that ZTO sample shows highest value of Seebeck coefficient, electrical conductivity and power factor as compared to the ZnO samples. It is also observed that the value of Seebeck coefficient showing an increasing trend for both of the samples as we increase the post growth annealing temperature. The higher thermoelectric properties for ZTO are due the presence of Sn atoms in ZnO structure. Tin dopants may generate secondary phases and/or enhanced the carrier mobility which might be the reason that ZTO has improved thermo-electric properties as compared to ZnO. XRD and Raman measurements were used to confirm the formation of ZTO. XRD data verified the hexagonal structure of ZnO but a slight red shift is observed for the case of ZTO samples. To further justify our argument, we have also performed Raman spectroscopy measurements which confirmed the presence of Sn elements in ZTO.

Atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) growth of undoped and aluminium-doped ZnO thin film using hot wall reactor

In this contribution, a hot wall reactor via economic atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) was adopted for Un-doped and Al-doped Zinc oxide films were deposited on borosilicate glass and silicon substrates. To avoid the use of an expensive vacuum system, all experiments were realized at atmospheric pressure. The chemical reagents used for this experiment are Zinc acetylacetonate (Zn(acac)2) and aluminium acetylacetonates (Al (acac)2) under atmospheric conditions. The obtained films are characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Uv-–vis spectrometer, respectively. As results, it is found that The un-doped ZnO films are polycrystalline. However, a significant enhancement in the intensity of the relevant (100) reflection is observed when Zinc oxide films are doped with Al. It is also observed that the Al-doped Zinc oxide films present higher transparency in the visible region and resistivities of 2.55 ohm cm and 1.44 ohm cm for un-doped and Al doped films respectively

Structural, optical and morphological studies of SILAR grown ZnO thin film and double coated CBD grown ZnO thin film

The Zinc oxide thin films were produced on glass substrate by using SILAR and CBD methods. The structural, optical and morphological properties of the films were investigated by X- Ray diffractometer, UV-visible spectrometer and scanning electron microscopy respectively. The XRD pattern shows that in both the samples preferential growth orientation is along (0 0 2) plane. The optical band gap was found to be 3.31eV for SILAR ample and 3.18eV for CBD grown sample. The morphology analysis shows that the particle size in SILAR grown sample was high. A vertically aligned nanorods were obtained in CBD grown sample.

Growth and Characterization of ZnO and Al-Doped ZnO Thin Films by a Homemade Spray Pyrolysis

In this work, we have prepared the undoped and Al-doped ZnO thin films by a homemade spray pyrolysis method at 450°C onto glass substrates. The X-ray diffraction patterns of undoped ZnO and aluminized zinc-oxide (AZO) thin films exhibit hexagonal wurtzite crystal structure with high crystalline quality, the crystallite size is nanometric. The morphology of the undoped and Al-doped ZnO thin films also indicate that all samples have a nanoscale grain size around 50 nm, and the microstructure of ZnO films is highly influenced by the aluminum doping. The two films are characterized by UV-visible spectrophotometry showing that the films have a whole optical transmission above 85% in the visible range. The composition of our films is obtained by energy dispersive spectrum, confirmed by Auger electron spectroscopy (AES) and by Rutherford back-scattering spectrometry (RBS) techniques.

Columnar structure growth of Mn-doped ZnO (MZO) thin films by radio frequency co-sputtering and studies on films properties

ABSTRACT The present investigation deals with the columnar structured growth of Mn doped ZnO (MZO) thin films by radio frequency sputtering technique. The X-ray diffraction and the processed electron diffraction pattern confirmed the hexagonal wurtzite structure and the film growth direction along (101) plane. The structure of grown film was compared with the pristine ZnO film and the JCPDS card No. 00-36-1451. The microstructures of the pristine ZnO and MZO films were studied by scanning electron microscopy and atomic force microscopy. The columnar structure growth of MZO was confirmed by transmission electron microscopy using TEM cross-section sample. The presence of constituent elements and their concentrations in the films were recorded by energy dispersive X-ray diffraction spectroscopy. The optical transmittance, absorption edge and band gap of the material were studied by UV-Visible transmission spectroscopy. The field dependent magnetization at room-temperature was analysed by using vibrating sample magnetometer and magneto-optic Kerr effect.

The Photophysical Properties of Ga-doped ZnO Thin Films Grown by Spray Pyrolysis Method

In this paper we report nanocrystalline ZnO thin films deposited by varying the Ga concentrations and atmosphere gas, onto the glass substrates using spray pyrolysis technique at 450 °C substrate temperature. After deposition Ga-doped ZnO thin films were annealed at temperature 420 °C in vacuum. The morphological, structural, optical and spectral properties of synthetized thin films have been characterized by scanning electron microscopy, X-ray diffraction, Raman analysis, UV–Vis spectrophotometry and spectrofluorimetry. The XRD result shows hexagonal structure with preferential orientation along the (0002) plane and the dependence of the values of the full-width at half-maximum of this peak on the nature of the gas used in the synthesis. Also, it is found that the optical bandgap can be increased by increasing the doping level. The fluorescence spectra of ZnO thin films with 1%, 2%, 3% and 5% concentrations of Ga demonstrate that these nanostructured thin films can produce reactive oxygen species (ROS) such as singlet oxygen under ultraviolet light. Nanocrystalline ZnO thin films in function of the Ga concentration provide the phosphorescence lifetime of the charge separated states up to 102 ms.