Effect of mesh patterning with UV pulsed-laser on optical and electrical properties of ZnO/Ag-Ti thin films

In this study, the ZnO/Ag-Ti structure for transparence conducting oxide (TCO) is investigated by optimizing the thickness of the Ag-Ti alloy and ZnO layers. The Ag-Ti thin film is deposited by DC magnetron sputtering and its thicknesses is well controlled. The ZnO thin film is prepared by sol-gel method using zinc acetate as cation source, 2-methoxiethanol as solvent and monoethanolamine as solution stabilizer. The ZnO film deposition is performed by spin-coating technique and dried at 150 °C on Corning 1737 glass. Due to the conductivity of ZnO/Ag-Ti is dominated by Ag-Ti, the sheet resistance of ZnO/Ag-Ti decrease dramatically as the thickness of Ag-Ti layer increases. However, the transmittances of ZnO/Ag-Ti become unacceptable for TCO application after the thickness of Ag-Ti layer beyond 6 nm. The as-deposited ZnO/Ag-Ti structure has the optical transmittance of 83% @ 500 nm and the low resistivity of 1.2 × 10⁻⁵ Ω-cm. Furthermore, for improving the optical and electrical properties of ZnO/Ag-Ti, the thermal treatment using laser is adopted. Experimental results indicate that the transmittance of ZnO/Ag-Ti is improved from 83% to 89% @ 500 nm with resistivity of 1.02 × 10⁻⁵ Ω-cm after laser drilling. The optical spectrum, the resistance, and the morphology of the ZnO/Ag-Ti will be reported in the study.     

Effects of deposition temperatures and annealing conditions on the microstructural, electrical and optical properties of polycrystalline Al-doped ZnO thin films

Al-doped ZnO (AZO, ZnO:Al₂O₃ = 98:2 wt%) films are deposited on different substrates by an RF magnetron sputtering and subsequently annealed at three different conditions to investigate the microstructural, electrical, and optical properties. X-ray diffraction and scanning electron microscope results show that all the samples are polycrystalline and the samples rapid-thermal-annealed at 900 °C in an N₂ ambient contain larger grains compared to the furnace-annealed samples. It is shown that the sample deposited at room temperature on the sapphire gives a resistivity of 5.57 × 10⁻⁴ Ω cm when furnace-annealed at 500 °C in a mixture of N₂:H₂ (9:1). It is also shown that the Hall mobility vs. carrier concentration (μ-n) relation is divided into two groups, depending on the annealing conditions, namely, either rapid-thermal annealing or furnace annealing. The relations are described in terms of either grain boundary scattering or ionized impurity scattering mechanism. In addition, the samples produce fairly high transmittance of 91-96.99% across the wavelength region of 400-1100 nm. The optical bandgaps of the samples increase with increasing carrier concentration.     

Influence of high-pressure hydrogen treatment on structural and electrical properties of ZnO thin films

ZnO thin films were treated by high-pressure hydrogen (H₂). Scanning electron microscope (SEM) images show that the surface morphology of ZnO films has been changed significantly by H₂ treatment. X-ray diffraction patterns show that the Zn(OH)₂ phases formed after H₂ treatment. The X-ray photoelectron spectroscopy results indicate that H atoms were doped into the surface of ZnO by forming H-O-Zn bond. The phenomenon shows that it is easy to form O-H bond in ZnO rather than H interstitial atom under high-pressure hydrogen circumstance.     

Investigation of electronic and optical properties in Al−Ga codoped ZnO thin films

Electronic and optical properties of Al−Ga codoped ZnO thin films were investigated by post-annealing. The lowest resistivity of the Al-Ga codoped ZnO films was observed from the 450 °C-annealed sample. The Fermi-level shift of the Al−Ga codoped ZnO film was ∼0.6 eV from x-ray photoelectron spectroscopy, and the widening of optical-bandgap in the Al−Ga codoped ZnO film was ∼0.3 eV. The correlations of optical-bandgap with Fermi-level shift and conduction band filling were suggested by schematic band diagrams.     

Dependences of structural and electrical properties on thickness of polycrystalline Ga-doped ZnO thin films prepared by reactive plasma deposition

Polycrystalline Ga-doped (Ga content: 4 wt%) ZnO (GZO) thin films were deposited on glass substrates at 200 C by a reactive plasma deposition with DC arc discharge technique. The dependences of structural and electrical properties of GZO films on thickness, ranging from 30 to 560 nm, were investigated. Carrier concentration, n, and Hall mobility, μ, increases with increasing film thickness below 100 nm, and then the n remains nearly constant and the μ gradually increases until the thickness reaches 560 nm. The resistivity obtained of the order of 10⁻⁴ Ω cm for these films decreases with increasing film thickness: The highest resistivity achieved is 4.4×10⁻⁴ Ω cm with n of 7.6×10²⁰ cm⁻³ and μ of 18.5 cm²/V s for GZO films with a thickness of 30 nm and the lowest one is 1.8×10⁻⁴ Ω cm with n of 1.1×10²¹ cm⁻³ and μ of 31.7 cm²/V s for the GZO film with a thickness of 560 nm. X-ray diffraction pattern for all the films shows a hexagonal wurtzite structure with its strongly preferred orientation along the c-axis. Full width at half maximum of the (002) preferred orientation diffraction peak of the films decreases with increasing film thickness below 100 nm.     

Ultra smooth NiO thin films on flexible plastic (PET) substrate at room temperature by RF magnetron sputtering and effect of oxygen partial pressure on their properties

Transparent p-type nickel oxide thin films were grown on polyethylene terephthalate (PET) and glass substrates by RF magnetron sputtering technique in argon + oxygen atmosphere with different oxygen partial pressures at room temperature. The morphology of the NiO thin films grown on PET and glass substrates was studied by atomic force microscope. The rms surface roughnesses of the films were in the range 0.63-0.65 nm. These ultra smooth nanocrystalline NiO thin films are useful for many applications. High resolution transmission electron microscopic studies revealed that the grains of NiO films on the highly flexible PET substrate were purely crystalline and spherical in shape with diameters 8-10 nm. XRD analysis also supported these results. NiO films grown on the PET substrates were found to have better crystalline quality with fewer defects than those on the glass substrates. The sheet resistances of the NiO films deposited on PET and glass substrates were not much different; having values 5.1 and 5.3 kΩ/□ and decreased to 3.05, 3.1 kΩ/□ respectively with increasing oxygen partial pressure. The thicknesses of the films on both substrates were ∼700 nm. It was also noted that further increase in oxygen partial pressure caused increase in resistivity due to formation of defects in NiO.     

Optical and electrical properties of p-type ZnO fabricated by NH3 plasma post-treated ZnO thin films

In this paper, a simple method is reported to obtain nitrogen-doped p-ZnO film. In this method NH₃ plasma, generated in a plasma-enhanced chemical vapor deposition system, was employed to treat ZnO thin film. By Hall-effect measurement, a p-type conductivity was observed for the treated film with the hole density of 2.2 × 10¹⁶ cm⁻³. X-ray photoelectron spectroscopy (XPS) results confirmed that nitrogen was incorporated into ZnO film during the treatment process to occupy the oxygen positions. In low temperature photoluminescence spectra, an emission peak corresponding to acceptor-donor pair was observed. From this emission peak we calculated the N-related acceptor binding energy to be 130 meV.     

The structural properties of Al doped ZnO films depending on the thickness and their effect on the electrical properties

In this study, the structural and electrical properties of AZO films with different film thickness deposited by r.f. magnetron sputtering were interpreted in relation with film growth process. The result shows that the grain size increases during film growth, which is accompanied by decrease of compressive stress, indicating the enhancement of crystallinity. The relationship between grain size and compressive stress follows the same tendency for the samples regardless of deposition temperature, which implies the strong dependencies between the grain size and the compressive stress. The XPS analysis shows that the defects such as chemisorbed oxygen and segregated Al₂O₃ cluster at grain boundary are reduced with increase of film thickness or deposition temperature, leading to increase of carrier concentration and mobility. The mobility increase is accompanied by grain size increase and compressive stress reduction, indicating the influences of grain boundary and crystallinity on the mobility.     

Photoluminescence of thermal-annealed nanocolumnar ZnO thin films grown by electrodeposition

Nanostructured zinc oxide thin films formed by partially oriented hexagonal columns with dimensions of about 100 nm × 300 nm have been prepared by cathodic electrodeposition on conducting glass substrates. After subsequent thermal annealing in air at different temperatures (100-500 °C), structural information on the films was obtained by means of non-resonant Raman spectroscopy. Increasing the annealing temperature leads to a higher degree of crystallinity. The photoluminescence activity of the samples (at low temperature) also improves for increasing annealing temperatures in two ways: increasing the intensity of the near-band edge emission and decreasing the width of the excitonic peak. No emission band in the visible is detected, which attests the high quality of the ZnO nanocolumnar films.     

Influence of target substrate distance on the properties of transparent conductive Si doped ZnO thin films

Si doped zinc oxide (SZO, Si3%) thin films are grown at room temperature on glass substrates under argon atmosphere, using direct current magnetron sputtering. The influence of the target substrate distances on structure, morphology, optical and electrical properties of SZO thin films is investigated. Experimental results show that the target substrate distances have a significance impact on the growth rate, crystal quality and electrical properties of the films, and have little impact on the optical properties of the films. SZO thin film samples grown on glasses are polycrystalline with a hexagonal wurtzite structure and have a preferred orientation along the c-axis perpendicular to the substrate. When the target substrate distance decreases from 76 to 60 mm, the degree of crystallization of the films increased, the grain size increases, and the resistivity of films decreases. However, when the distance continuously decreases from 60 to 44 mm, the degree of crystallization of the films decreased, the grain size decreases, and the resistivity of the films increases. SZO(3%) thin films deposited at a target substrate distance of 60 mm show the lowest resistivity of 5.53 × 10⁻⁴ Ω cm, a high average transmission of 94.47% in the visible range, and maximum band gap of 3.45 eV under 5 Pa of argon at sputtering power of 75 W for sputtering time of 20 min.     

Structural and optical properties of ZnO thin films on (111) CaF2 substrates grown by magnetron sputtering

ZnO thin films were grown on (111) CaF₂ substrates by magnetron sputtering at room temperature. Structural and optical properties of the ZnO thin films were studied. XRD analysis showed that the ZnO thin films had the (002) preferential orientation. The transmittance of ZnO thin films was over 80% in the visible range. The optical band gap of the ZnO thin films was 3.26 eV. The optical constants (n,k)$(n,k)$ of the ZnO thin films in the wavelength range 300–1000 nm were obtained by infrared spectroscopic ellipsometry measurement. PL spectra of ZnO thin films showed strong UV near-band-edge emission peak at 376.5 nm and weak visible red emission at 643.49 nm using He–Cd laser as the light source, using a synchrotron radiation light source PL spectra showed three emission peak at 320 nm, 410 nm and 542 nm respectively.     

Structural and optical characteristics of spin-coated ZnO thin films

Zinc oxide (ZnO) thin films were deposited onto glass substrates by spin-coating method, from a precursor solution containing zinc acetate, ethanol and ammonium hydroxide. After deposition, the films were heated at a temperature of 100 °C in order to remove unwanted materials. Finally, the films were annealed at 500 °C for complete oxidation. X-ray diffraction showed that ZnO films were polycrystalline and have a hexagonal (wurtzite) structure. The crystallites are preferentially oriented with (0 0 2) planes parallel to the substrate surface. The films have a high transparency (more than 75%) in the spectral range from 450 nm to 1300 nm. The analysis of absorption spectra shows the direct nature of band-to-band transitions. The optical bandgap energy ranges between 3.15 eV and 3.25 eV.Some correlations between the processing parameters (spinning speed, temperature of post deposition heat treatment) and structure and optical characteristics of the respective thin films were established.     

Structural, optical and electrical properties of ZnO/Zn2GeO4 porous-like thin film and wires

Zinc oxide/zinc germanium oxide (ZnO/Zn₂GeO₄) porous-like thin film and wires has been fabricated by simple thermal evaporation method at temperature about 1120 °C for 2.5 h. The structural and optical properties of the porous-like-thin film and wires have been investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Metal semiconductor metal (MSM) photodetector structure was used to evaluate the electrical characteristics by using current-voltage (I-V) measurements. Room temperature photoluminescence spectrum of the sample shows one prominent ultraviolet peak at 378 nm and a shoulder at 370 nm. In addition, broad visible blue emission peak at wavelength 480 nm and green emission peak at 500 nm are also observed. Strong photoelectric properties of the MSM in the UV demonstrated that the porous-like-thin film and wires contribute to its photosensitivity and therefore making ZnO/Zn₂GeO₄ wires potential photodetector in the shorter wavelength applications.     

Structural and optical properties of Er, Yb co-doped Y2O3 thin films

Thin Er³⁺, Yb³⁺ co-doped Y₂O₃ films were grown on (1 0 0) YAG substrates by pulsed laser deposition. Ceramic targets having different active ion concentration were used for ablation. The influence of the rare-earth content and oxygen pressure applied during the deposition on the structural, morphological and optical properties of the films were investigated. The films deposited at the lower pressure, 1 Pa, and at 1/10 Er to Yb doping ratio are highly textured along the (1 1 1) direction of the Y₂O₃ cubic phase. In addition to the crystalline structure, these films possess smoother surface compared to those prepared at the higher pressure, 10 Pa. All other films are polycrystalline, consisting of cubic and monoclinic phases of Y₂O₃. The rougher surface of the films produced at the higher-pressure leads to higher scattering losses and different behavior of the reflectivity spectra. Optical anisotropy in the films of less than 0.004 was measured regardless of the monoclinic structure obtained. Waveguide losses of about 1 dB/cm at 633 nm were obtained for the films produced at the lower oxygen pressure.     

纳米ZnO和ZnO-SiO2复合薄膜的光学性质研究

通过溶胶凝胶(sol-gel)法分别在玻璃衬底上制备了ZnO纳米薄膜和ZnO-SiO₂纳米复合薄膜,并利用紫外-可见光分光光度计对薄膜的光学性能进行了分析.可见光-紫外透射谱显示,随着ZnO溶胶浓度从0.7mol/L降低到0.006mol/L,制备的ZnO薄膜从只出现一个380nm(对应的光学禁带宽度为3.27eV)左右的吸收边到在380和320nm(对应的光学禁带宽度为3.76eV)左右各出现一个吸收边,并且随着ZnO溶胶浓度的降低,在380—320nm波段内的透过率明显提高.而Z 关键词： 纳米ZnO 2复合薄膜')" href="#">ZnO-SiO₂复合薄膜 溶胶凝胶法 透射率     

The influence of oxidation temperature on structural, optical and electrical properties of thermally oxidized bismuth oxide films

Monoclinic bismuth oxide (Bi₂O₃) films have been prepared by thermal oxidation of vacuum evaporated bismuth thin films onto the glass substrates. In order to obtain the single phase Bi₂O₃, the oxidation temperature was varied in the range of 423-573 K by an interval of 50 K. The as-deposited bismuth and oxidized Bi₂O₃ films were characterized for their structural, surface morphological, optical and electrical properties by means of X-ray diffraction, scanning electron microscopy (SEM), optical absorption and electrical resistivity measurements, respectively. The X-ray analyses revealed the formation of polycrystalline mixed phases of Bi₂O₃ (monoclinic, α-Bi₂O₃ and tetragonal, β-Bi₂O₃) at oxidation temperatures up to 523 K, while at an oxidation temperature of 573 K, a single-phase monoclinic α-Bi₂O₃ was formed. From SEM images, it was observed that of as-deposited Bi films consisted of the well-defined isolated crystals of different shapes while after thermal oxidation the smaller dispersed grains were found to be merged to form bigger grains. The changes in the optical properties of Bi₂O₃ films obtained by thermal oxidation at various temperatures were studied from optical absorption spectra. The electrical resistivity measurement depicted semiconducting nature of Bi₂O₃ with high electrical resistivity at room temperature.     

Growth of transparent conducting nano-structured In doped ZnO thin films by pulsed DC magnetron sputtering

Transparent conducting nano-structured In doped zinc oxide (IZO) thin films are deposited on corning 7059 glass substrates by bipolar pulsed DC magnetron sputtering with variation of pulsed frequency and substrate temperature. Highly c-axis oriented IZO thin films were grown in perpendicular to the substrate on the 30 kHz and 500 °C. The IZO films exhibited surface roughness of 3.6 nm similar to the commercial ITO and n-type semiconducting properties with electrical resistivity (carrier mobility) of about 5 × 10⁻³ Ω cm (14 cm²/V s). The optical characterization showed high transmittance of over 85% in the UV-vis region and exhibited the absorption edge of near 350 nm. In micro-Raman spectra, the origin of two additional modes is attributed to the host lattice defect due to the addition of In dopant. These results suggest that the IZO film can possibly be applied to make transparent conducting electrodes for flat panel displays.     

Structural, optical and electrical properties of Zn1−xCdxO thin films prepared by PLD

Ternary polycrystalline Zn_1−xCd_xO semiconductor films with cadmium content x ranging from 0 to 0.23 were obtained on quartz substrate by pulse laser deposited (PLD) technique. X-ray diffraction measurement revealed that all the films were single phase of wurtzite structure grown on c-axis orientation with its c-axis lattice constant increasing as the Cd content x increasing. Atomic force microscopy observation revealed that the grain size of Zn_1−xCd_xO films decreases continuously as the Cd content x increases. Both photoluminescence and optical measurements showed that the band gap decreases from 3.27 to 2.78 eV with increasing the Cd content x. The increase in Cd content x also leads to the broadening of the emission peak. The resistivity of Zn_1−xCd_xO films decreases evidently for higher values of Cd content x. The shift of PL emission to visible light as well as the decrease of resistivity makes the Zn_1−xCd_xO films potential candidate for optoelectronic device.     

Structural and electrical properties of lithium manganese oxide thin films grown by pulsed laser deposition

LiMn₂O₄ thin films were deposited by reactive pulsed laser deposition technique and studied the microstructural and electrical properties of the films. The LiMn₂O₄ thin films deposited in an oxygen partial pressure of 100 mTorr and at a substrate temperature of 573 K from a lithium rich target were found to be nearly stoichiometric. The films exhibited predominantly (111) orientation representing the cubic spinel structure with Fd3m symmetry. The intensity of (111) peak increased and a slight shift in the peak position was observed with the increase of substrate temperature. The lattice parameter increased from 8.117 to 8.2417 Å with the increase of substrate temperature from 573 to 873 K. The electrical conductivity of the films is observed to be a strong function of temperature. The evaluated activation energy for the films deposited at 873 K is 0.64 eV.     

Comparison of the optical properties of undoped and Ga-doped ZnO thin films deposited using RF magnetron sputtering at room temperature

The optical properties of undoped zinc oxide (ZnO) thin films of various thicknesses were compared with those of Ga-doped (GZO) thin films. Transparent, high-quality undoped ZnO and GZO films were deposited successfully using radio-frequency (RF) sputtering at room temperature. The films were polycrystalline with a hexagonal structure and a strongly preferred orientation along the c-axis. The films had an average optical transmission >85% in the visible part of the electromagnetic spectrum. The undoped ZnO thin films were more transparent than the GZO thin films. In the photoluminescence (PL) spectrum, ZnO film has higher quality than GZO as a result of decrease in the green emission intensity.