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The crystal structure and morphology of pure ZnO and Al-doped ZnO films a XRD pattern, b SEM image pure ZnO and c SEM image of Al-doped ZnO thin film
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We report the synthesis and luminescence properties of the pure and Al-doped photosensitive ZnO films by microwave successive ionic layer adsorption reaction. The grain textured growth along c-axis in pure ZnO thin films and those doped with Al was studied by Energy-dispersive X-ray spectroscopy. The Al-doped films show high textured grain growth a...
Citations
... Incorporation of ZnO filler into the epoxy matrix (INT0) caused lightness parameter L* to increase as the ZnO concentration increased. In the same manner as in bare samples, ZnO-loaded ones exhibited greenness (a* < 0) due to the hardener, as stated above, and to possible defects in ZnO crystal structure [53]. Yellowness parameter b* did not undergo significant changes. ...
An as-produced epoxy material reinforced with ZnO (nano)rods for outdoor use was produced for the purpose of enclosing VHF/early UHF transceiving elements. Three different ZnO (nano)rod percentages were dispersed (0.1 wt%, 0.5 wt% and 2 wt%) in epoxy samples and were consequently exposed to an artificial weathering environment for a total period of 2880 h. SEM and XRD characterizations were followed by gravimetric, colorimetric and dielectric measurements that were conducted every 576-h AWE treatment intervals and were complemented by FTIR, UV-Vis, contact angle and gloss measurements. The composite exhibited favourable dielectric behaviour: ZnO presence inflicted minimal impact to the composites’ loss tangent, while dielectric permittivity was reduced for low ZnO content (0.1 wt%/0.5 wt%), especially until the 1152-h interval, while it suffered an increase for 2 wt% samples that was maintained from the beginning until the end of the experiment. Hence, the low-k (4–5.2) constructed material, compared to bare epoxy resin, maintained moderate loss tangent levels (0.55–0.7) in the VHF/early UHF spectrum, throughout the full AWE treatment, and also attained reduced dielectric permittivity, thus exhibiting moderate radio frequency transparency, together with enhanced endurance against environmental fatigue.
... Increasing the temperature of the chemical bath up to 110 • C, i.e., the doping percentage, increases the DLE and hence the ratio of UV/visible intensity become smaller with increasing Al doping. This means increasing the aluminum concentration will increase DLE emission with respect to NBE, which is most likely due to added zinc and oxygen vacancies created by the substitution of zinc atoms with Al [30,36]. A drastic decrease in the intensity of the NBE peak was observed with increasing doping concentration. ...
Vertically aligned Al-doped ZnO nanorods (AZO-NRs) were grown on glass substrate using a chemical bath depo-sition (CBD) method at various temperatures between 80 • C and 130 • C. The results showed the Al content in the AZO-NRs strongly depends on the growth temperature. The optimum doping level was attained at 110 • C. The morphology was maintained in each sample, and the lasing properties were investigated against the Al-doped variation. The sample with a high doping level exhibited superior random lasing, with high intensity and spectral width of less than 0.08 nm. The same sample also had the lowest pumping threshold of 0.192 mW. More importantly, this study showed the possibility of utilizing doping as a tuning parameter for random lasing, whereby a 7.3 nm redshift in the lasing peak was observed with increasing doping concentration. This study also placed an emphasis on AZO-NRs as potential candidates for tunable random laser devices.
... Increasing the temperature of the chemical bath up to 110 • C, i.e., the doping percentage, increases the DLE and hence the ratio of UV/visible intensity become smaller with increasing Al doping. This means increasing the aluminum concentration will increase DLE emission with respect to NBE, which is most likely due to added zinc and oxygen vacancies created by the substitution of zinc atoms with Al [30,36]. A drastic decrease in the intensity of the NBE peak was observed with increasing doping concentration. ...
Vertically aligned Al-doped ZnO nanorods (AZO-NRs) were grown on glass substrate using a chemical bath deposition (CBD) method at various temperatures between 80°C and 130°C. The results showed the Al content in the AZO-NRs strongly depends on the growth temperature. The optimum doping level was attained at 110°C. The morphology was maintained in each sample, and the lasing properties were investigated against the Al-doped variation. The sample with a high doping level exhibited superior random lasing, with high intensity and spectral width of less than 0.08 nm. The same sample also had the lowest pumping threshold of 0.192 mW. More importantly, this study showed the possibility of utilizing doping as a tuning parameter for random lasing, whereby a 7.3 nm redshift in the lasing peak was observed with increasing doping concentration. This study also placed an emphasis on AZO-NRs as potential candidates for tunable random laser devices.
... The peak areas for different color emissions were tabulated and revealed that all the defects decrease because of the addition of Al/Si in ZnO. Green emission (attributed to V O ) and yellow emission bands (due to O i ) reduce drastically in the codoped sample because of the higher charge of Al 31 /Si 41 , which attracts more oxygen into the ZnO lattice and because of lower ionic radii of Al 31 /Si 41 than Zn 21 . Unlike our results, earlier studies suggested that substitutional Al doping in ZnO enhanced green emission intensity, which they attributed to the larger charge density of Al and the creation of additional oxygen vacancies into the modified lattice [26]. However, the single doping of Si into ZnO reduces the oxygen vacancies but on the other hand increases O i as reported in the literature [17]. ...
The structural, vibrational, and optoelectronic properties of sol–gel synthesized Zn1−x(Al0.5Si0.5)xO nanoparticles
were investigated. The X-ray diffraction studies of the samples confirmed the hexagonal wurtzite phase with
the space group P63mc. No significant changes were observed in the lattice parameters. The increase in the
intensity of E2
high Raman mode observed at 438 cm−1 indicates a decrease in the crystallite size. The reduction in
the deep-level emission band with the introduction of Al/Si indicates a decrease in intrinsic defects for the
codoped sample. A unique electron paramagnetic resonance signal at g = 1.96 follows the same trend as the
green luminescence, and its evolution was shown to probe the oxygen vacancy concentrations. I–V characteristics
curve confirm the increase in the conductivity for the codoped samples. To evaluate the role of surface defects,
ultraviolet photoresponse behavior as a function of time was also studied, and an increase in the photocurrent
was observed. The slow decay and rise in the photocurrent are because of multiple trapping by interstitial defects.
A relatively faster response time was observed with the substitution of Al/Si. It has been observed that prepared
nanomaterials are suitable for optoelectronic devices.
... Various deposition techniques have been employed to produce AZO films such as microwave successive ionic layer adsorption reaction [9], spray pyrolysis [6,7], physical vapor deposition [8], atomic layer deposition [5], RF magnetron sputtering [1,2,4] and sol-gel [3,[10][11][12]. Among these techniques, the sol-gel process presents several advantages such as low cost, simplicity, control of chemical composition and dopants and lower crystallization temperature. ...
Al-doped ZnO (AZO) thin films are deposited on glass substrates by sol-gel method and dip-coating technique using different number of coating layers (6, 9 and 12). The effects of two different drying processes on structural, morphological, electrical and optical properties of the synthesized thin films are investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), Hall-effect measurements, UV–Vis–NIR spectrometry and photoluminescence (PL) spectroscopy. In the first drying process, temperature is gradually increased with an increment of 10°/min from room temperature to 150 °C. While in the second drying process, temperature is maintained at 250 °C. XRD results show that all deposited films crystallized in a hexagonal wurtzite structure. It is observed that the second drying process yields better crystal quality and films orientation. The AFM images reveal that both surface morphology and roughness are dependent on the drying process. Low roughness of 1.33 nm is obtained for the sample dried with the second process. Hall-effect measurements demonstrate high carrier concentration of 4.58×1021cm−3 and low resistivity of 0.003Ω.cm for the films which were found to be dependent on the drying process and film thickness. According to UV–visible–NIR optical measurements, all films exhibit an average transmission ranging from 70 to 86% and the optical band gap is sensitive for both the drying process and film thickness. Room temperature photoluminescence spectra show the dependence of the AZO thin films emission on the drying process. Higher emissions are obtained for the films dried at 250 °C, however the emission decreases with increasing thickness and this for both drying processes. The obtained results confirm that crystal quality and PL properties of the AZO films can be enhanced by the type of drying method.
... Zhao et al. grew a single ZnO nanowire on a flexible substrate using a custom-built nano-manipulation system and investigated it as an ultra-high-sensitivity strain sensor [9]. Thomas et al. used a microwave successive ionic layer adsorption reaction to synthesize pure and Al-doped photosensitive ZnO films and investigated their luminescence properties [10]. ...
ZnO films with a thickness of ~200 nm were deposited on SiO2/Si substrates as the seed layer. Then Zn(NO3)2-6H2O and C6H12N4 containing different concentrations of Eu(NO3)2-6H2O or In(NO3)2-6H2O were used as precursors, and a hydrothermal process was used to synthesize pure ZnO as well as Eu-doped and In-doped ZnO nanowires at different synthesis temperatures. X-ray diffraction (XRD) was used to analyze the crystallization properties of the pure ZnO and the Eu-doped and In-doped ZnO nanowires, and field emission scanning electronic microscopy (FESEM) was used to analyze their surface morphologies. The important novelty in our approach is that the ZnO-based nanowires with different concentrations of Eu3+ and In3+ ions could be easily synthesized using a hydrothermal process. In addition, the effect of different concentrations of Eu3+ and In3+ ions on the physical and optical properties of ZnO-based nanowires was well investigated. FESEM observations found that the undoped ZnO nanowires could be grown at 100 °C. The third novelty is that we could synthesize the Eu-doped and In-doped ZnO nanowires at temperatures lower than 100 °C. The temperatures required to grow the Eu-doped and In-doped ZnO nanowires decreased with increasing concentrations of Eu3+ and In3+ ions. XRD patterns showed that with the addition of Eu3+ (In3+), the diffraction intensity of the (002) peak slightly increased with the concentration of Eu3+ (In3+) ions and reached a maximum at 3 (0.4) at%. We show that the concentrations of Eu3+ and In3+ ions have considerable effects on the synthesis temperatures and photoluminescence properties of Eu3+-doped and In3+-doped ZnO nanowires.
... SEM images display the structures characterized in terms of their forms, sizes, material, and uniformity of the layer. [33][34][35][36] In this article, gold and silver were coated on the silicon surfaces using the thermal evaporation method, by single-layer and doublelayer depositing; the first layer material on the double-layer coatings was TiO 2 ; AFM measurements considered for this article were measurements related to the minimum force necessary to separate the AFM tip. The specimen giving the adhesion force is often known as the pull-off force. ...
Adhesion force is one of the most important factors in microelectromechanical systems (MEMS), especially for microassembly. It depends on operating conditions and is affected by the contact area. In this study, the adhesion force between MEMS materials and AFM tips was analysed using AFM's point‐mode spectroscopy. The aim was to study the effectiveness of various coatings in MEMS adhesion surfaces. For this purpose, five silicon surfaces were used, four of which were coated, and one was noncoated. Two of them were deposited by single‐layer coating (Au and Ag). The other two were deposited by double‐layer coating (TiO2/Au, TiO2/Ag) on a Si (1 0 0) substrate. The depositing was accomplished by the thermal evaporation method. Composite materials and analysis were reviewed by observing the SEM image. The experimental results showed that the method of deposition helped to decrease the adhesion force between the probe tip and the surface of the specimens, and double‐layer coating had stronger effect on decreasing the adhesion force than the single‐layer coating.
Titanium dioxide (TiO2) thin films of different concentrations are prepared by using titanium trichloride on conducting FTO glass substrate by chemical bath deposition (CBD) method. The X-ray powder diffraction (XRD) method is used to study the structure of TiO2 thin film. XRD analysis has confirmed amorphous nature of the TiO2.The surface morphology of the film is studied using field emission scanning electron microscopy (FE-SEM). The optical properties are studied using the UV-VIS and photoluminescence (PL) spectroscopy. The band gap of prepared titanium dioxide (TiO2) thin film is 2.84 eV. A photo-electrochemical cell analysis shows that the conversion efficiency of 3.24% with a fill factor of 43%.
ZnO nanowires doped with Aluminium (AZO) grown by chemical bath deposition technique on ITO/glass substrates exhibit random lasing emission with lowest threshold of just 0.07 W/cm2 when 12.5 % of aluminium nitride was added during the growth of the nanorods. Compared to pure ZnO nanorods, grown with the same parameters, threshold was at least 2 orders of magnitude lower. Results overall indicate incorporating aluminium reduces threshold for random lasers however improvements in doping high aluminium content without affecting growth is required to reduce the threshold at high doping levels.
