ZnO Buffer Layer Thickness Research Articles

Thermochromism of vanadium dioxide films controlled by the thickness of ZnO buffer layer under low substrate temperature

High-quality vanadium dioxide (VO2) thermochromic thin films were fabricated on ZnO/soda-lime glass via direct current magnetron sputtering at a low temperature of 320 °C. The ZnO polycrystalline film was used as a buffer layer between glass substrate and VO2 film to improve the thermochromic property of VO2 film. The results of XRD, Raman spectrum, SEM and visible-infrared spectrum indicated that the thickness of the ZnO buffer layer has a significant effect on the physical and thermochromic performances of VO2 films. The surface morphologies of all VO2 films can be divided into three groups by employing ZnO buffers with different thicknesses. The film with thin buffer (56 nm) exhibited a weak crystallinity, low phase temperature and low solar energy modulability compared with the pristine sample. However, the crystallinity and solar switching efficiency of VO2 films noticeably increased as the thickness of the buffer layer increased further (thicker than 56 nm). The calculated modulability of solar energy of the VO2 film with a 235-nm thick ZnO buffer layer is about 13.11%, which may be beneficial in the application of VO2 films for smart energy-efficient windows.

Influence of ZnO buffer layer on the electrical, optical and surface properties of Ga-doped ZnO films

The influence of the ZnO buffer layer thickness on the structural, electrical, optical and surface properties of Ga-doped ZnO (GZO) films deposited on glass substrates by RF magnetron sputtering were investigated. X-ray diffraction results showed the obtained films had highly c-axis oriented with hexagonal (002) structures and GZO film with 20 nm buffer layer had the best crystalline quality. The resistivity in GZO/ZnO bi-layer films decreased significantly than that in GZO film without a ZnO buffer layer, and GZO film with 20 nm buffer layer showed the lowest resistivity of 4.09 × 10−4 Ω cm. The bi-layer films exhibited the highest transmittance of over 80% in the visible light range and displayed a low near infrared transmittance. The correlation between surface morphology and wettability was studied and GZO/ZnO bi-layer films exhibited hydrophobic property with contact angle of θ from 104° to 108.5°, indicating acceptable property of environmental durability.

Quality-enhanced AlN epitaxial films grown on c-sapphire using ZnO buffer layer for SAW applications

AlN epitaxial films with a thin ZnO buffer layer were successfully deposited on c-sapphire by DC magnetron sputtering for surface acoustic wave (SAW) applications. The effect of ZnO buffer layer thickness on structural properties of AlN epitaxial films and the related SAW properties were investigated systematically. The results revealed that a thin ZnO buffer layer can significantly enhance the crystalline quality of AlN films and release the strain in AlN films. The AlN films were epitaxially grown on ZnO buffered-substrate with orientation relationship of (0001)[101¯0]AlN//(0001)[101¯0]ZnO//(0001)[2¯110]Al2O3. High frequency SAW devices with a center frequency of 1.4GHz, a phase velocity of 5600m/s were achieved on the obtained AlN films. The optimum ZnO buffer layer thickness was found to be 10nm, resulting in high-quality epitaxial AlN films with a FWHM value of the rocking curve of 0.84°, nearly zero stress and low insertion loss of SAW devices. This work offers an effective approach to achieve high-quality AlN epitaxial films on sapphire substrates for the applications of AlN-based SAW devices.

Influence of ZnO buffer layers on the optoelectronic properties in Ga-doped ZnO thin films prepared by RF magnetron sputtering on PET substrates

The influence of ZnO buffer layers on the optoelectronic properties in Ga-doped ZnO (GZO) thin films deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering was investigated. The resistivity in GZO/ZnO bilayer films decreases significantly more than one order of magnitude than that in GZO film without a ZnO buffer layer. X-ray diffraction results show that the significant improvement of electrical properties is not related to the crystalline quality. Based on X-ray photoelectron spectroscopy analysis, it is suggested that the decrease in resistivity after the introduction of ZnO buffer layers is ascribed to the restraint of diffusion of moisture and gas from PET substrates to GZO thin films. The moisture and gas diffused into GZO films will be absorbed on the films’ surface in the form of negatively charged oxygen species acting as acceptors. Fifty nm buffer layer is thick enough to achieve the best effect, with further increase of the ZnO buffer layer thickness, the resistivity in the samples will increase due to the parallel effect of ZnO and GZO layers. The introduction of ZnO buffer layers has no obvious influence on the average transmittance in the visible range which is ~90 % high for all samples.

Effect of ZnO buffer layer thickness on the epitaxial growth of GaN by reactive magnetron sputtering

Epitaxial GaN films were grown on sputtered ZnO buffer layers of thickness 25–200nm over c-plane sapphire by reactive sputtering of GaAs in nitrogen at 700°C. The epitaxial quality and microstructure have been studied by high resolution X-ray diffraction in phi (ϕ) and omega (ω) scan geometries. The surface morphology of epilayers was studied by atomic force microscopy and scanning electron microscopy and their crystalline quality was assessed by Raman spectroscopy. These studies have shown that ZnO buffer layers of 50–100nm facilitate growth of GaN epilayers of high crystalline quality, compared to those grown on thinner and thicker ZnO buffer layers.

Effect of the ZnO Buffer Layer Thickness on AZO Film Properties

To evaluate the influence of the ZnO buffer layer thickness on structural, electrical and optical properties of ZnO: Al (AZO)/ZnO bi-layer films, a series of AZO/ZnO films were deposited on the quartz substrates by electron beam evaporation. X-ray diffraction measurement shows that the crystal quality of the films is improved with the increase of the film thickness. The electrical properties results show that the resistivity decreases initial and then increases. However, optical transmittance of all the films is >80% regardless of the buffer layer thickness in the visible region. The results illustrate that the insertion of ZnO buffer layer can improve the film performance.

Influence Of ZnO Buffer Layer On Growth Of Sb Doped ZnO Nano Wires Using Nano Particle Assisted Pulsed Laser Deposition (NAPLD) Using Sb As Catalyst

Influence of ZnO buffer layer thickness on the structural and optical properties of the Sb catalyzed/doped ZnO nanowires synthesized using NAPLD has been investigated. Buffer layer with a thickness of 100 nm, 800 nm and 1600 nm coated with Sb are used as a substrate and pure ZnO was used as a target to synthesize Sb doped ZnO nanowires. Introduction of the buffer layer lead to the growth of vertically aligned along with horizontally grown ZnO nano wires. With the increase in buffer layer thickness, the core diameter of the vertically grown ZnO nano wires was subsequently increased. Nano wires synthesized with a buffer layer thickness of 1600 nm showed a significant change in the lattice constants, resulting in measurable lower angle of about 0.06o from XRD, widening of lattice fringe spacing of 0.54 nm from TEM and Suppression of A1T and E1(L0) modes in Raman Spectroscopic. In addition a strong UV emission with absence of visible emission was observed from the room temperature PL. This confirms the generation of Sb doped ZnO nano wire with high crystal quality. Copyright © 2012 VBRI Press.

Study on the Effect of ZnO Buffer Layer Thickness on the Properties of MgZnO Film

ZnO has recently attracted considerable attention due to its favorable properties such as the wider band gap (3.37eV) at room temperature, the large binding energy of excitons (60meV). These good photoelectric and piezoelectric properties [1-4] cause it has immensity space for developing at surface acoustic wave devices, light emitting diodes (LEDs) [5] , photodetectors [6], gas sensor and solar cells [7] etc. MgZnO has many similar properties to ZnO. Furthermore, the band gap of MgZnO is 3.3-4.0eV [9] due to the wider band gap of MgO (7.7eV [8]). In this paper, we report the characteristic of MgxZn1-xO films which were grown on c-plane sapphire with different thickness-ZnO buffer layers by MOCVD. By investigating the surface morphology, structural and optical properties, some dependences between properties of MgZnO films and the thicknesses of ZnO buffer layers can be found.

Effect of ZnO Buffer Layer Thickness on the Structural and the Optical Properties of PLD-grown0.1Zn0.9O Films

Effect of ZnO Buffer Layer Thickness on the Structural and the Optical Properties of PLD-grown0.1Zn0.9O Films

Growth of ZnGa 2O 4 nanowires on a ZnO buffer layer by carbothermal reduction of Ga 2O 3 powder

The synthesis of pure ZnGa 2O 4 nanowires (NWs) on the ZnO-coated Si substrates could be achieved by carbothermal reduction of Ga 2O 3 powder. The processing parameters such as the weight of Ga 2O 3 powder, the thickness of ZnO buffer layer, and the substrate temperature were explored. The growth of ZnGa 2O 4 NWs followed the vapor–solid process. Surplus ZnO source favored the growth of ZnGa 2O 4 NWs, while higher substrate temperature promoted the growth of Ga 2O 3 nanobelts. The results indicated a window for the growth of abundant and pure ZnGa 2O 4 NWs. The growth mechanism of ZnGa 2O 4 NWs on the ZnO buffer layer via carbothermal reduction of Ga 2O 3 powder was discussed. The ZnGa 2O 4 NWs showed a photoluminescence band centered at 466–475 nm.

Effect of Buffer Layer Thickness on the Growth Properties of Hydrothermally Grown ZnO Nanorods

We investigated the effect of ZnO buffer layer thickness on the growth of hydrothermally grown ZnO nanorods. A series of ZnO buffer layers with different thicknesses was deposited on a p-Si (111) substrate using a co-sputtering system. After annealing the ZnO buffer layer, ZnO nanorods grown were grown hydrothermally at 95 degrees C. Unlike ZnO nanorods grown on as-deposited ZnO buffer layer, the diameter and length of ZnO nanorods grown on annealed ZnO buffer layers can be controlled. The structural and optical properties of ZnO nanorods grown on annealed ZnO buffer layers were analyzed by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence. The influence of ZnO buffer layer thickness on ZnO nanorods growth is discussed.

Investigation and Fabrication of Bottom Gate ZnO:Al TTFTs with Various Thicknesses of ZnO Buffer Layers

An Al doped ZnO (ZnO:Al) transparent thin film transistors (TTFTs) with various thickness of ZnO buffer layer sandwiched between gate insulator and channel ayer were deposited by a magnetron radio frequency co-sputter system. When the thickness of the buffer layer was 80 nm, the field-effect carrier mobility of the TTFTs was as high as 122.0 cm^2/V-s. Furthermore, the associated gate voltage swing was 0.24 V/decade, and the maximum state density was 2.69×10^11 eV^−1cm^−2. The on-to-off current ratio of the TTFTs with 80 nm-thick ZnO buffer layer was up to 5×10^7.

Growth and characteristics of ZnO films on growth side of freestanding diamond substrate dependent on buffer layer thickness

We report the growth and properties of highly c-axis oriented ZnO films, by radio-frequency magnetron sputtering, on the growth side of freestanding chemical vapor deposited diamond film-substrate. Low-temperature ZnO buffer layer is required for the formation of continuous ZnO films. The morphology, structure, and optical properties of the ZnO films deposited are strongly dependent on the thickness of the buffer layer. The optimized thickness of ZnO buffer layer is about 10 nm to realize high-quality ZnO films having small compressive stress and high intensity ultraviolet emission. The ZnO/diamond (growth side) system is available for the applications in numerous fields, especially for high performance surface acoustic wave devices.

Influence of ZnO buffer layer on AZO film properties by radio frequency magnetron sputtering

Transparent conductive films of Al-doped zinc oxide (AZO) were deposited on glass substrates under various ZnO buffer layer deposition conditions (radio frequency (r.f.) power, sputtering pressure, thickness, and annealing) using r.f. magnetron sputtering at room temperature. This work investigates the influence of ZnO buffer layer on structural, electrical, and optical properties of AZO films. The use of grey-based Taguchi method to determine the ZnO buffer layer deposition processing parameters by considering multiple performance characteristics has been reported. Findings show that the ZnO buffer layer improves the optoelectronic performances of AZO films. The AZO films deposited on the 150-nm thick ZnO buffer layer exhibit a very smooth surface with excellent optical properties. Highly c-axis-orientated AZO/ZnO/glass films were grown. Under the optimized ZnO buffer layer deposition conditions, the AZO films show lowest electrical resistivity of 6.75 × 10 −4 Ω cm, about 85% optical transmittance in the visible region, and the best surface roughness of R a = 0.933 nm.

Influence of ZnO buffer layer thickness on the electrical and optical properties of indium zinc oxide thin films deposited on PET substrates

The influence of the ZnO buffer layer thickness on the electrical and optical properties of In 2O 3–10 wt.% ZnO and ZnO bilayers deposited on polyethylene terephthalate (PET) substrates by RF magnetron sputtering were investigated. The optimum ZnO buffer layer thickness was found to be 90 nm which gives the lowest electrical resistivity of the bilayer of IZO and ZnO deposited on the PET substrate. The surface roughness decreases and diffusion of moisture and gas is more efficiently restrained, which contributes to lower the resistivity of the bilayer as the ZnO buffer layer thickness is increased. On the other hand, the total resistivity of the bilayer increases as the ZnO buffer layer thickness is increased because the resistivity of ZnO is higher than that of IZO. Introduction of a ZnO buffer layer does not nearly affect the IZO/ZnO/PET sample.

Influence of ZnO buffer layer thickness on electrical and optical properties of GZO thin films deposited on polymer substrates

Ga doped ZnO (GZO) thin films were deposited on polymer polyethylene terephthalate (PET) substrates with a ZnO buffer layer using a radio frequency (RF) magnetron sputtering technique and the effects of the buffer layer thickness on the microstructure, and electrical and optical properties of the GZO films were investigated to develop transparent conductors for flexible display applications. The optimum buffer layer thickness with which the lowest resistivity of the GZO/ZnO films was obtained was determined to be 140 nm. The carrier concentration, the carrier mobility and the electrical resistivity of the GZO film with a ZnO buffer layer 140 nm thick were 7·5 × 1020 cm−3, 9·4 cm2 V−1 s−1 and 8·8 × 10−4 Ω cm respectively. The transmittance of the GZO/ZnO films was found to be higher than 85% and nearly independent of the ZnO buffer layer thickness.

Effects of low-temperature-grown ZnO buffer layer and Zn/O ratio on the properties of high-temperature-overgrown ZnO main layer on Si substrate by MBE

The undoped ZnO thin films grown on Si (1 1 1) substrates by plasma-assisted molecular beam epitaxy (P-MBE) were reported. The effects of growth temperature, the thickness of low temperature ZnO buffer layer and Zn/O ratio on the quality of high-temperature-overgrown ZnO main layer were studied by atomic force microscopy (AFM), X-ray diffraction (XRD) and room-temperature photoluminescence (PL) spectra. These results showed that it was difficult to directly obtain high quality ZnO films on Si substrate. By introducing a thin ZnO buffer layer at 350 °C, c-axis preferred orientation ZnO films with improved optical properties were obtained at 750 °C. However, the thickness of ZnO buffer layer and Zn/O ratio in the ZnO main layer greatly influenced the quality of high-temperature-overgrown ZnO main layer.

Antibacterial treatments on titanium for implantology

Transparent conductive films of Al-doped zinc oxide (AZO) were deposited on glass substrates under various ZnO buffer layer deposition conditions (radio frequency (r.f.) power, sputtering pressure, thickness, and annealing) using r.f. magnetron sputtering at room temperature. This work investigates the influence of ZnO buffer layer on structural, electrical, and optical properties of AZO films. The use of grey-based Taguchi method to determine the ZnO buffer layer deposition processing parameters by considering multiple performance characteristics has been reported. Findings show that the ZnO buffer layer improves the optoelectronic performances of AZO films. The AZO films deposited on the 150-nm thick ZnO buffer layer exhibit a very smooth surface with excellent optical properties. Highly c-axis-orientated AZO/ZnO/glass films were grown. Under the optimized ZnO buffer layer deposition conditions, the AZO films show lowest electrical resistivity of 6.75 × 10−4 Ω cm, about 85% optical transmittance in the visible region, and the best surface roughness of Ra = 0.933 nm.

Effects of ZnO buffer layer thickness on the crystallinity and photoluminescence properties of rf magnetron sputter-deposited ZnO thin films

Highly c-axis oriented ZnO thin films were grown on Si(100)substrates with Zn buffer layers. Effects of the Zn buffer layer thickness on the structural and optical qualities of ZnO thin films were investigated using X-ray diffraction (XRD), photoluminescence (PL) and Atomic force microscopy (AFM) analysis techniques. It was confirmed that the quality of a ZnO thin film deposited by rf magnetron sputtering was substantially improved by using a Zn buffer layer. The highest ZnO film quality was obtained with a Zn buffer layer 110 nm thick. The surface roughness of the ZnO thin film increases as the Zn buffer layer thickness increases.

Preparation of GaN films on ZnO buffer layers by rf magnetron sputtering

We have deposited the GaN films on Si(001) substrate using the ZnO buffer layers at room temperature by the radio frequency (rf) magnetron sputtering method. The ZnO buffer layer thickness affected the structural properties of GaN films. With a sufficiently thick ZnO layer, we have obtained a c-axis-oriented GaN/ZnO thin film on Si with the XRD full-width at half-maximum (FWHM) of 0.22° and root-mean-square (RMS) surface roughness of about 22Å.