Effect of Cr and V dopants on the chemical stability of AZO thin film

The effect of the dopants of Cr and V on the optoelectronic properties of AZO thin film by pulsed DC magnetron sputtering has been investigated. We also use HCl and KOH solutions to conduct the chemical stability of AZO:Cr:V thin film. The experimental results show that the optimum AZO optoelectronic properties without Cr and V doping obtain the resistivity of 9.87 × 10⁻⁴ Ω cm, optical transmittance of 84% and surface roughness rms value of 2.6 nm. The chemical stability of AZO will increase after Cr and V doping. Under the added V = 0.19 wt.%, Cr = 0.56 wt.%, AZO:Cr:V thin film showed 52% increased chemical stability and 128% decrease in surface roughness after etching (the resistivity was 3.62 × 10⁻³ Ω cm and optical transmittance 81%). From the experimental results, the higher resistivity obtained after KOH etching compared with after HCl etching. The reason is that the Zn/Al ratio will reduce after etching and cause the AZO film carrier density to reduce as well. However, the optical transmittance obtained after KOH etching will be higher than that after HCl etching. This is because that a better surface roughness after KOH etching obtained than after HCl etching.     

Comparing study of subpicosecond and nanosecond wet etching of fused silica

The effectiveness of the laser induced backside wet etching (LIBWE) of fused silica produced by subpicosecond (600 fs) and nanosecond (30 ns) KrF excimer laser pulses (248 nm) was studied. Fused silica plates were the transparent targets, and naphthalene-methyl-methacrylate (c = 0.85, 1.71 M) and pyrene-acetone (c = 0.4 M) solutions were used as liquid absorbents. We did not observe etching using 600 fs laser pulses, in contrast with the experiments at 30 ns, where etched holes were found. The threshold fluences of the LIBWE at nanosecond pulses were found to be in the range of 360-450 mJ cm⁻² depending on the liquid absorbers and their concentrations. On the basis of the earlier results the LIBWE procedure can be explain by the thermal heating of the quartz target and the high-pressure bubble formation in the liquid. According to the theories, these bubbles hit and damage the fused silica surface. The pressure on the irradiated quartz can be derived from the snapshots of the originating and expanding bubbles recorded by fast photographic setup. We found that the bubble pressure at 460 mJ cm⁻² fluence value was independent of the pulse duration (600 fs and 30 ns) using pyrene-acetone solution, while using naphthalene-methyl-methacrylate solutions this pressure was 4, 5 times higher at 30 ns pulses than it was at 600 fs pulses. According to the earlier studies, this result refers to that the pressure should be sufficiently high to remove a thin layer from the quartz surface using pyrene-acetone solution. These facts show that the thermal and chemical phenomena in addition to the mechanical effects also play important role in the LIBWE procedure.     

掺杂透明导电半导体薄膜的光电性能研究

掺杂氧化锌透明导电膜(AZO)是一种重要的光电子信息材料，其制备方法有真空蒸镀法、磁控溅射法，化学气相沉积和脉冲激光沉积法等。该文采用溶胶 凝胶（sol gel)工艺在普通玻璃基片上成功地制备出Al3+掺杂型ZnO透明导电薄膜。将这种薄膜在空气和真空中以不同的温度进行了退火处理，并对薄膜进行了XRD分析和光电性能研究。结果表明，所制备的薄膜为钎锌矿型结构，在c轴方向择优生长，真空退火有利于薄膜结晶状况的改善，并使薄膜的载流子浓度大幅度地增加而电阻率下降，并且真空退火对薄膜的透射率影响不大。     

Optical and electrical properties of aluminum zinc oxide (AZO) nanostructured thin film deposited on polycarbonate substrate

Transparent polymer materials, due to their unique properties, such as light weight, optical transparency, and electrical and mechanical properties, have become very attractive as a replacement for inorganic glass substrates in a wide range of optoelectronic applications. In this research, aluminum zinc oxide nanostructured thin film was deposited on polycarbonate polymer substrates using a magnetron sputtering technique. The structure, morphology, and surface composition of the thin film were investigated by X-ray diffraction and field emission scanning electron microscopy. The optical and electrical properties of the thin film were investigated by UV–VIS-NIR spectrophotometer, ellipsometer, and four point probe method. The X-ray diffraction pattern showed that the aluminum zinc oxide thin film had a polycrystalline structure. The optical and electrical results indicated that the refractive index, band gap, and sheet resistance of the aluminum zinc oxide thin film were 1.8, 3.2 eV, and 265 Ω/sq, respectively.     

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.     

Preparation and infrared emissivity of ZnO: Al (AZO) thin films

ZnO:Al(AZO) thin films with different Al-doped concentration were developed under different temperature. The effects of the temperature and Al-doped concentration on the infrared emissivity were investigated. Results show that the crystalline phase of the AZO films is hexagonal wurtzite which is the same as that of the un-doped ZnO film. The crystalline size become larger and the particle shapes become more regular with the increase of temperature, which lead to the increase of resistivity and the decreases of the infrared emissivity.     

Effect of crystallinity of ZnO buffer layer on the properties of epitaxial (ZnO:Al)/(ZnO:Ga) bi-layer films deposited on c-sapphire substrate

Bi-layer ZnO films with 2 wt.% Al (AZO; ZnO:Al) and 4 wt.% Ga-doped (GZO; ZnO:Ga) were deposited on the ZnO buffered and annealed ZnO buffered c(0 0 0 1)-sapphire(Al₂O₃) substrates respectively by Pulsed Laser Deposition (PLD). The effect of crystallinity of ZnO buffer layer on the crystallinity and electrical properties of the AZO/GZO bi-layer thin films was investigated. It was seen that the crystallinity of ZnO buffer layer had a great influence on the orientation and defect density of AZO/GZO bi-layer thin films from X-ray Diffraction (XRD) peaks and High Resolution Transmission Electron Microscopy (HRTEM) images. In a word, it was found in the films that more preferred c-axis orientation texture and reduction of the defects such as stacking faults and dislocations, with increasing of the crystallinity of ZnO buffer layer.     

Mechanical reliability of transparent conducting IZTO film electrodes for flexible panel displays

The mechanical reliability of transparent In-Zn-Sn-O (IZTO) films grown using pulsed DC magnetron sputtering with a single oxide alloyed ceramic target on a transparent polyimide (PI) substrate at room temperature is investigated. All IZTO films deposited at room temperature have an amorphous structure. However, their optical and electrical properties change depending on the oxygen partial pressure applied during depositing process. At an oxygen partial pressure of 3%, the films exhibit a resistivity of 8.3 × 10⁻⁴ Ω cm and an optical transmittance of 86%. Outer bending tests show that the critical bending radius decreases from 10 mm to 7.5 mm when the oxygen partial pressure increases from 1% to 3%. In the inner bending test, the critical bending radius is independent of oxygen partial pressure at 3.5 mm, indicating excellent film flexibility. In the dynamic fatigue test, the electrical resistance of the films reduces by less than 1% for more than 2000 bending cycles. These results suggest that IZTO films have excellent mechanical durability and flexibility in comparison to ITO films.     

Highly conductive and transparent laser ablated nanostructured Al: ZnO thin films

Al doped ZnO thin films are prepared by pulsed laser deposition on quartz substrate at substrate temperature 873 K under a background oxygen pressure of 0.02 mbar. The films are systematically analyzed using X-ray diffraction, atomic force microscopy, micro-Raman spectroscopy, UV-vis spectroscopy, photoluminescence spectroscopy, z-scan and temperature-dependent electrical resistivity measurements in the temperature range 70-300 K. XRD patterns show that all the films are well crystallized with hexagonal wurtzite structure with preferred orientation along (0 0 2) plane. Particle size calculations based on XRD analysis show that all the films are nanocrystalline in nature with the size of the quantum dots ranging from 8 to 17 nm. The presence of high frequency E₂ mode and longitudinal optical A₁ (LO) modes in the Raman spectra suggest a hexagonal wurtzite structure for the films. AFM analysis reveals the agglomerated growth mode in the doped films and it reduces the nucleation barrier of ZnO by Al doping. The 1% Al doped ZnO film presents high transmittance of ∼75% in the visible and near infrared region and low dc electrical resistivity of 5.94 × 10⁻⁶ Ω m. PL spectra show emissions corresponding to the near band edge (NBE) ultra violet emission and deep level emission in the visible region. Nonlinear optical measurements using the z-scan technique shows optical limiting behavior for the 5% Al doped ZnO film.     

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.     

Influence of the deposition pressure on the properties of transparent conducting zirconium-doped zinc oxide films prepared by RF magnetron sputtering

Transparent and conducting zirconium-doped zinc oxide films with high transparency and relatively low resistivity have been successfully prepared by RF magnetron sputtering at room temperature. The deposition pressure was varied from 0.6 to 2.5 Pa. A transformation from a relatively compact structure to individual grains was observed with the increase of deposition pressure. As the deposition pressure increases, the resistivity increases sharply due to both, the decrease of hall mobility and carrier concentration. The lowest resistivity achieved was 2.07 × 10⁻³ Ω cm at a deposition pressure of 0.6 Pa with a hall mobility of 16 cm² V⁻¹ s⁻¹ and a carrier concentration of 1.95 × 10²⁰ cm⁻³. The films are polycrystalline with a hexagonal structure and a preferred orientation along the c-axis. All the films present a high transmittance of above 90% in the visible range. The optical band gap decreases from 3.35 to 3.20 eV as the deposition pressure increases from 0.6 to 2.5 Pa.     

Temperature dependence of optical absorption for the visible region in transparent conducting oxides

We study theoretically the temperature dependence of the optical-absorption coefficient, for the visible region, in thin films of transparent conducting oxides by using the well-known Varshni approach relative to optical band-gap energy. Zero absorption is considered and an approximate formula for the coefficient of visible absorption is derived when photon energy is near the band-gap energy, that is, when absorption is negligible.     

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.     

Synthesis of P-type transparent conducting silver:indium oxide (AIO) thin films by reactive electron beam evaporation technique

Present paper reports the synthesis, electrical and optical properties of p-type conducting and transparent silver indium oxide (AIO) thin films prepared on glass substrates by reactive electron beam evaporation technique at three substrate temperatures (50, 200 and 250 °C) and at five evaporation rates (0.05 to 16.0 nm/s). The source material is pure powders of Ag₂O:In₂O₃=50:50 mol%. The AIO films are amorphous. The films, though not corresponding to Delafossite crystal structure, exhibit p-type conductivity, when prepared at an evaporation rate of 0.05 nm/s at all the three substrate temperatures. With increasing filament current, it is observed that (i) the electrical resistivity decreases and (ii) the refractive index of the films (at 632.8 nm, and is in the range: 1.219-1.211) decreases. The work function (effective Fermi level) has been measured on these samples by Kelvin Probe method. The results are explained on the basis of partial ionic charge and localization of covalent bonds in the AIO thin films.     

Preparation of transparent conducting ZnO:Al coating using hot wall deposition technique

Aluminium-doped zinc oxide thin films were grown on glass substrates using hot wall deposition technique. The method involved evaporation of high purity ZnO and Al from respective sources surrounded by alumina cylinder held at high temperature. The additional thermal energy supplied by the hot wall to the particles colliding on it helps in its migration resulting in highly uniform films. XRD studies show the growth of c-axis oriented near single phase ZnO films having about 90% transmittance in the visible range and resistivity of the order of 10⁻⁴Θ cm.     

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.     

A study of stitch line formation during high speed laser patterning of thin film indium tin oxide transparent electrodes

High speed laser patterning of indium tin oxide thin films on glass is part of the production method used to produce transparent conductive electrodes for plasma display panels. Such a design consists of rows of repeating electrode structures which cover the active area of the display. Whilst the patterning process for such electrode structures exceeds the industrial acceptance criteria there are certain features that are yet to be fully understood. The visible line that occurs in-between two adjacent laser processed areas, commonly known as a stitch line, is one such feature. Previously published research claimed that the stitch line was caused by incomplete removal of the thin film however experimental results presented within this paper demonstrate that this cannot be the case and show that the stitch line is formed by redeposition of the plume of ablated material within the area of overlap with the previous pulse, and that heating of the sample by the second pulse plays a key role in stitch line formation.     

Influence on the laser induced backside dry etching of thickness and material of the absorber, laser spot size and multipulse irradiation

Laser induced backside dry etching method (LIBDE) was developed - analogously to the well-known laser induced backside wet etching (LIBWE) technique - for the micromachining of transparent materials. In this procedure, the absorbing liquid applied during LIBWE was replaced with solid metal layers. Fused silica plates were used as transparent targets. These were coated with 15-120 nm thick layers of different metals (silver, aluminium and copper). The absorbing films were irradiated by a nanosecond KrF excimer laser beam through the quartz plate. The applied fluence was varied in the 150-2000 mJ/cm² range, while the irradiated area was between 0.35 and 3.6 mm². At fluences above the threshold values, it was found that the metal layers were removed from the irradiated spots and the fused silica was etched at the same time. In our experiments, we investigated the dependence of the main parameters (etch rate and threshold) of LIBDE on the absorption of the different metal layers (silver, copper, aluminium), on the size of the irradiated area, on the film thickness and on the number of processing laser pulses.     

Control growth of catalyst-free high-quality ZnO nanowire arrays on transparent quartz glass substrate by chemical vapor deposition

ZnO nanowire arrays have been successfully synthesized on transparent quartz glass substrate by chemical vapor deposition technique. Our work demonstrates the critical role of the growth temperature and the buffer layer on the effective control of the morphology of ZnO nanowires. A proper growth temperature and the thicker buffer layer could promise the good alignment and high density of the nanowires. The room-temperature photoluminescence spectrum shows that the buffer layer has also great effects on optical properties of ZnO nanowire arrays. The integrated intensity ratio [I_UV/I_{Visible band}] of the ZnO UV emission peak to visible band emission decreases with the increase of the thickness of the buffer layers. The obtained nanowire arrays have transmittance of above 50% in the visible region.     

ZnO纳米流体对氨水降膜吸收影响的实验研究

通过配制不同浓度ZnO纳米流体的氨水溶液,研究了ZnO纳米流体氨溶液在降膜吸收器内定初始压力条件下对氨气的吸收效果.结果表明:不同浓度的纳米流体体现出对氨水降膜吸收强化的效果有所不同,随着ZnO纳米流体浓度的增大,对氨水降膜吸收的强化影响先增大后减小,且在浓度为0.1wt％时强化效果最佳.从实验还可看出,氨水基液浓度的增加使氨气的吸收量逐渐减小,但纳米流体的添加均可使吸收量得到不同程度的提高,纳米流体的加入,还可放缓由于氨水基液浓度增高引起的吸收速率降低的速度,且强化吸收的最佳纳米流体浓度不随氨水基液浓度的改变而改变.