Structural and morphological properties of ZnO:Ga thin films

Zinc oxide (ZnO) is a promising semiconductor material with a great variety of applications. Compared to undoped ZnO, impurity-doped ZnO has a lower resistivity and better stability. With this aim, Ga has been proposed as a dopant. In this study, the structural characteristics and surface morphology of ZnO films produced by PEMOCVD at a substrate temperature of 250 °C on the c-plane (001) of sapphire were investigated. Doping was realized with 1, 3, 5 and 10 wt.% of Ga₂(AA)₃ in the precursor's mixture. At lower contents, Ga stimulates growth of (002) oriented textured films and the smallest FWHM was obtained as low as 0.17° for ZnO:Ga with 1 wt.%. A change in preferential orientation as well as surface smoothing and roughness decreasing of the films were observed with further increasing Ga content in precursor's mixture. We assume a key role of Ga and note that such a feature would be beneficial for the application of ZnO thin films for formation of abrupt junctions in p-n device structures.     

Effect of annealing temperature on structural, electrical and optical properties of B-N codoped ZnO thin films

The B-N codoped p-type ZnO thin films have been prepared by radio frequency magnetron sputtering using a mixture of nitrogen and oxygen as sputtering gas. The effect of annealing temperature on the structural, electrical and optical properties of B-N codoped films was investigated by using X-ray diffraction, Hall-effect, photoluminescence and optical transmission measurements. Results indicated that the electrical properties of the films were extremely sensitive to the annealing temperature and the conduction type could be changed dramatically from n-type to p-type, and finally changed to weak p-type in a range from 600 °C to 800 °C. The B-N codoped p-type ZnO film with good structural, electrical and optical properties can be obtained at an intermediate annealing temperature region (e.g., 650 °C). The codoped p-type ZnO had the lowest resistivity of 2.3 Ω cm, Hall mobility of 11 cm²/Vs and carrier concentration of 1.2 × 10¹⁷ cm^− 3.     

Preparation of Li and Er codoped ZnO thin films and their photoluminescence

Li-Er codoped ZnO thin films have been prepared on Si(100) substrates by pulsed laser deposition (PLD). Both the as-grown and post-annealed films exhibit good crystalline quality with preferred c-axis orientation. After post-annealing at 850 °C, the photoluminescence (PL) related to intra-4f shell of Er³⁺ can be clearly observed. The Li-Er codoped ZnO film shows higher intensity of PL around 1.54 μm than the Er monodoped ZnO film. The behavior is attributed to the lowering of the symmetry of the crystal field around Er³⁺ ions by introducing Li⁺ into ZnO lattice, which is also confirmed by Raman scattering spectra.     

Preparation and characterization of sol-gel Li and Al codoped ZnO thin films

Li and Al codoped ZnO (LAZO) thin films have been prepared by a sol-gel method and their structural and optical properties have been investigated. The prepared LAZO films had an average transmittance of over 85% in the visible range. The UV absorption edge was red-shifted with Li-doping, whereas it was blue-shifted with Al-doping. A broad yellowish-white emission was observed from the LAZO films annealed above 600 °C. The visible emission was enhanced with increasing annealing temperature and dopant concentration.     

Structural, electrical and optical properties of Ga-doped ZnO films on cyclo-olefin polymer substrates

Ga-doped ZnO (GZO) films with a thickness of 100 nm were prepared on cyclo-olefin polymer (COP) and glass substrates at various temperatures below 100 °C by ion plating with direct-current arc discharge. The dependences of the characteristics of GZO films on the substrate temperature Ts were investigated. All the polycrystalline GZO films, which exhibited a high average visible transmittance of greater than 86%, were crystallized with a wurtzite structure oriented along the c-axis. The lowest resistivities of the GZO films were 5.3 × 10^− 4 Ωcm on the glass substrate and 5.9 × 10^− 4 Ωcm on the COP substrate.     

Reproducibility and stability of N–Al codoped p-type ZnO thin films

Reproducible and stable p-type ZnO thin films have been prepared by the N–Al codoping method. Secondary ion mass spectroscopy measurements demonstrate that N and Al are incorporated into ZnO. The resistivity, carrier concentration, and Hall mobility are typically of 50–100 Ωcm, 1×10¹⁷–8×10¹⁷ cm⁻³, and 0.1–0.6 cm²/Vs, respectively, for the N–Al codoped p-type ZnO films. Hall measurement, X-ray diffraction, and optical transmission were carried out to investigate the changes of the properties with the storage period. Results show that the p-type characteristics of the N–Al codoped ZnO films are of acceptable reproducibility and stability. In addition, the N–Al codoped p-type ZnO films have good crystallinity and optical quality. The properties are time independent.     

Structural and optical properties of Cu doped ZnO thin films by co-sputtering

This paper reports on the structural and optical properties of ZnCuO thin films that were prepared by co-sputtering for the application of p-type-channel transparent thin-film transistors (TFTs). Pure ceramic ZnO and metal Cu targets were prepared for the co-sputtering of the ZnCuO thin films. The effects of the Cu concentration on the structural, optical, and electrical properties of the ZnCuO films were investigated after their heat treatment. It was observed from the XRD measurements that the ZnCuO films with a Cu concentration of 7% had ZnO(002), Cu2O(111), and Cu2O(200) planes. The 7% Cu-doped ZnO films also showed a band-gap energy of approximately 2.05 eV, an average transmittance of approximately 62%, and a p-type carrier density of approximately 1.33 x 10(19) cm-3 at room temperature. The bottom-gated TFTs that were fabricated with the ZnCuO thin film as a p-type channel exhibited an on-off ratio of approximately 6. These results indicate the possibility of applying ZnCuO thin films with variable band-gap energies to ZnO-based optoelectronic devices.     

Reflection X-ray topography of ZnO thin films on non-orienting substrates

Thin or moderately thick polycrystalline films of ZnO with preferentially oriented crystallites deposited on non-orienting substrates can in some cases be investigated using conventional X-ray topography. Examples of such reflection topographs are presented and their characteristic features are discussed. In particular, it is often possible to observe the texture, the film inhomogeneity and the influence of the deposition conditions on the preferred orientation.     

Structural and electrical properties of Al doped ZnO thin films deposited at room temperature on poly(vinilidene fluoride) substrates

Transparent, conducting, Al-doped ZnO films have been deposited, by dc and pulsed dc magnetron sputtering, on glass and electroactive polymer (poly(vinylidene fluoride)–PVDF) substrates. Samples have been prepared at room temperature varying the argon sputtering pressure, after optimizing other processing conditions. All ZnO:Al films are polycrystalline and preferentially oriented along the [002] axis. Electrical resistivity around 3.3 × 10^− 3 Ω cm and optical transmittance of ~ 85% at 550 nm have been obtained for AZOY films deposited on glass, while a resistivity of 1.7 × 10^− 2 Ω cm and transmittance of ~ 70% at 550 nm have been attained in similar coatings on PVDF. One of the main parameters affecting film resistivity seems to be the roughness of the substrate.     

Structural,optical and electrical characterization of ZnO:Ga thin films for organic photovoltaic applications

Gallium-doped zinc oxide (ZnO:Ga) films were prepared on glass substrates by RF magnetron sputtering. The effect of growth temperature on microstructure, optical and electrical properties of the films was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectrophotometer and four-point probe. The results show that all the films are polycrystalline and (002) oriented, and that the growth temperature significantly affects the microstructure and optoelectrical properties of the films. The film deposited at 670 K has the largest grain size of 71.9 nm, the lowest resistivity of 8.3 × 10^? 4 Ω?cm and the highest figure of merit of 2.1 × 10^? 2 Ω^? 1. Furthermore, the optical energy gaps and optical constants were determined by optical characterization methods. The dispersion behavior of the refractive index was also studied using the Sellmeir's dispersion model and the oscillator parameters of the films were obtained.     

Structural, electrical and bending properties of transparent conductive Ga-doped ZnO films on polymer substrates

We investigated the characteristics of highly transparent conductive Ga-doped ZnO (GZO) polycrystalline films of 100 nm thickness deposited on glass and polymer substrates. GZO films were deposited by ion plating with dc-arc discharge. We developed multiple-deposition method to obtain various deposition process temperatures lower than 100 °C. Cross-sectional SEM images show that all the GZO films have columnar structure. Analysis of data obtained by XRD measurements shows that all the GZO films with wurtzite structure exhibit highly (002) orientation perpendicular to the substrate. The resistivity of the GZO films deposited on polyester and glass substrates were 5.0 × 10^-4 Ω · cm. The mechanical bending properties of the GZO films were investigated by comparing the sheet resistance determined before and after a bending test with various bending diameters. For the bending diameter of more than 30 mm, all the GZO films exhibited excellent bending properties with no change in sheet resistance. For the bending diameter of less than 20 mm, we found the sheet resistance affected by the bending. We demonstrated that our multiple-deposition method to achieve different controllable polyester substrate temperatures is highly suitable for improving the bending properties of GZO films.     

AlN/Si衬底上ZnO薄膜的择优取向生长

当ZnO薄膜直接沉积在Si衬底上时,由于ZnO与Si的晶格失配度大,不易于获得高质量的ZnO薄膜.因此,选择合适的衬底材料沉积ZnO薄膜,对提高其质量非常重要.本文采用射频磁控溅射法,通过在Si(100)衬底上预沉积AlN作为ZnO薄膜生长的缓冲层,获得了择优取向的ZnO薄膜.我们还讨论了ZnO薄膜在AlN/Si衬底上的取向生长机理.     

射频磁控溅射制备Mn掺杂ZnO薄膜的结构与光学性能

采用反应射频磁控溅射方法制备Zn1-xMnxO薄膜(0≤x≤0.25),并在不同温度下进行退火处理.通过原子力显微镜、薄膜X射线衍射、透射电子显微镜和透射光谱对薄膜的成分、表面形貌、微结构和光学性质进行了研究.结果表明,薄膜结晶质量明显地依赖于掺杂Mn元素的浓度,所有薄膜都表现了沿(002)晶面方向择优取向生长,当Mn...     

Mechanical properties of ZnO thin films deposited on polyester substrates used in flexible device applications

ZnO is growing in importance as a functional film in flexible devices because of the wide range of electrical properties that can be achieved through appropriate doping and the relative abundance of Zn. We have deposited ZnO films with various thicknesses by sputtering on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) flexible substrates and measured their mechanical properties using compression and scratch tests coupled with in-situ optical microscopy. The cracking of ZnO, during compression, is thickness dependent and at lower thicknesses the films sputtered on PEN exhibit the highest crack onset strains, around 2%. During scratch testing, two major scratch failure mechanisms are observed, analyzed and discussed. It is also found that scratch resistance of ZnO is thickness dependent for both PET and PEN. At high scratch loads a secondary failure mechanism due to impregnation of film debris into the polymer substrates is observed.     

Structural and functional properties of ZnO thin films grown on Si substrates by air assisted USP method from non-aqueous solutions at low-temperature

In this work, we deals with the processing and characterization of transparent conducting ZnO thin films on p-type Silicon substrates (1 0 0) by air assisted Ultrasonic Spray Pyrolysis (USP) method. The thin films from different Zn acetate precursor solution concentrations (0.1, 0.2, 0.3 and 0.4 M) were deposited at several temperatures (400, 450 and 500 °C) with thickness from ～100 to ～500 nm. The effects of precursor solution concentration, deposition time and temperature on the structural, morphological, optical, and electrical properties of ZnO films were studied by X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), UV–Vis-NIR spectroscopy, and Hall Effect techniques, respectively. It has been shown that on the ZnO film surface, the preferred orientation, the average crystallite size, the electrical resistivity and the RMS surface roughness depend on the substrate temperature. The grown films have showed a good adhesion and an excellent optical transmission of about 80–95% within the visible range (400–800 nm) and a direct band gap from 3.35 to 3.23 eV with the increase of the substrate temperature and the deposition time. All the PL spectra have exhibited a typical green-yellow emission band. Additionally photovoltaic (PV) activities of n-ZnO/p-Si heterostructures fabricated are investigated.     

Laser-ablated plasma for deposition of ZnO thin films on various substrates

We report optical and structural properties of ZnO films deposited by pulsed laser deposition technique on 1100) n-typesilicon and quartz substrates at various pressures of back ground gas. ZnO plasma was created using KrF laser 1248 nm) atvarious pressures of the ambient gas, oxygen. Laser induced plasma at varying fluence on the target was investigated using optical emission spectroscopy and 2-D images of the expanding plumes. X-ray diffraction, atomic force microscopy, and spectro-photometry were used to characterize as grown films.