Figure - available from: Journal of Materials Science: Materials in Electronics
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Crystal structure of a undoped ZnO and b Ga-doped ZnO. Planar diagram of the atomic arrangement of c (002) plane, and d (100) plane of wurtzite ZnO
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With the vigorous development of information display system and solar energy conversion technology, it is crucial to develop newly indium-free, transparent conductive material (TCO). In this work, Ga-doped ZnO (GZO) thin films with excellent TCO properties were prepared by atomic layer deposition (ALD) at low-temperature. The influence of doping co...
Citations
... Some growth methods for depositing doped films require targets with corresponding doping ratios, preventing free modulation of the composition and significantly increasing the growth cost. Plasma-enhanced atomic layer deposition (PE-ALD) has a great advantage in setting the doping ratio freely and adapting to complex deposition surfaces with high aspect ratios [24,25]. PE-ALD enables effective doping of thin films using more readily accessible precursors. ...
Aluminum-doped Ga2O3 (AGO) thin films were prepared by plasma-enhanced atomic layer deposition (PE-ALD). The growth mechanism, surface morphology, chemical composition, and optical properties of AGO films were systematically investigated. The bandgap of AGO films can be theoretically set between 4.65-6.8 eV. Based on typical AGO films, metal-semiconductor-metal photodetectors (PDs) were created, and their photoelectric response was examined. The preliminary results show that PE-ALD grown AGO films have high quality and tunable bandgap, and AGO PDs possess superior characterizations to undoped films. The AGO realized using PE-ALD is expected to be an important route for the development of a new generation of gallium oxide-based photodetectors into the deep-ultraviolet.
... The preparation procedure is shown in Fig. 5. Ga cations as dopants supply electrons and zinc cations result in less lattice distortion [81]. Similar changes in growth orientation with Ga-doping have been observed by other researchers [82,83]. In Ga-doped ZnO, the surface defect, especially the oxygen vacancy, is the main reason for the accurate measurement of carbon monoxide, which is also analyzed by the XPS technique. ...
Until now, various composites based on zinc oxide (ZnO) have been investigated in electrochemical sensors. The physical and electrochemical properties of ZnO and its structure can improve the selectivity, sensitivity, and adaptability of nanocomposites. Therefore, the focus on the fabrication of cheap ZnO-based electrodes with affordable and easy transportability has increased. In addition, the electrochemical behavior is affected by the structure and morphology of the ZnO-based composite in detecting pollutants such as volatile organic compounds, heavy metals, and toxins. Furthermore, ZnO-based nanostructures are efficient in the fabrication of electrochemical sensors in the food industry, pharmaceutical analysis, and medical diagnostics. In this review, various techniques in the synthesis of ZnO-based electrodes and their effect on the particle size, shape, and morphology of compounds have been collected. Since the performance of chemical sensors has a direct relationship with the structure of the composite used in its electrode, it is necessary to discuss the new production methods, new concepts, strategies, and challenges. Additionally, new gains highlight recent developments and sensing of various analytes in the monitoring systems. These sensors have demonstrated a strong growth acceleration which could lead to the development of recent technologies. At last, an optimistic outlook is provided on the future of ZnO-based sensors and their challenges.
... To fabricate GZO thin films, several growth techniques such as electron beam evaporation [21], sol-gel [22], spray pyrolysis [23], pulsed laser deposition [24], atomic layer deposition [25], and radio frequency (RF) magnetron sputtering [17] can be implemented. The magnetron sputtering deposition approach is a preferable deposition technique for the production of ZnO-based TCE films with high quality since it provides homogenous and pure film together with its applicability to obtain films on large area, strong adhesion to the substrate, and precise controllable film thickness [26]. ...
In the present study, the impact of deposition pressure and substrate temperature of Ga-doped ZnO (GZO) thin film and the photovoltaic performance of this structure as a TCE layer in silicon-based solar cell were investigated. The structural, optical, and electrical properties of 350 nm thick GZO thin films with various deposition pressure (5-20 mTorr) and substrate temperature (RT-250 °C) were fabricated using sputtering technique using a single target of GZO. The aim here was to find out the GZO films with the optimum pressure and substrate temperature to incorporate them into solar cell as TCE layer. The XRD spectra of all the prepared films was dominated by (002) preferential orientation irrespective of the deposition pressure and substrate temperature. Both increasing the deposition pressure (up to 15 mTorr) and substrate temperature (up to 200 °C) contributes to improving the crystallite size, widening the optical band gap, lowering the resistivity, and increasing the carrier concentration. In order to evaluate and compare the effect both pressure and substrate temperature, Silicon-based solar cells were fabricated using the most promising layers (15 mTorr@RT, 15 mTorr@200°C). The cell performance with the GZO thin film as a TCE layer showed that varying both pressure and substrate temperature to GZO film contributed to enhancing the solar parameters. Thus, the conversion efficiency increased from 9.24% to 12.6% with the sequential optimization of pressure and temperature. It can be concluded that pressure applied during the deposition and substrate temperature have a significant impact on the properties of GZO thin films and its photovoltaic performance.
... The first is the Burstein-Moss effect in which increases in the dopant can result in an increase in the band gap. In GZO thin films, an increase in the deposition power increases the concentration of incorporated dopants in the film, yielding a wider band gap [22,23]. The second cause is stress in the film. ...
For the first time in the literature, the material properties of gallium-doped zinc oxide, grown from a high impulse magnetron sputtering system (HiPIMS), are reported. These material properties are compared to those of a typical radio frequency (RF) sputtering deposition. The films were grown without thermal assistance and were compared across multiple average deposition powers. The films’ resistivity, crystallinity, absorption coefficient, band gap, and refractive index were measured for each of the samples. It was observed that very similar results could be obtained between the HiPIMS and RF sputtering processes under the same average power conditions. It was found that the RF depositions demonstrated a slightly higher band gap and deposition rate as well as lower resistivity and optical absorption coefficient. Band gaps and grain size were found to increase with the power of the deposition for both HiPIMS and RF. These values ranged between 3.45 eV and 3.79 eV and 9 nm and 23 nm in this study, respectively. The absorption coefficient and resistivity were both found to decline with increasing power in both methods but reached minimums of 2800 cm−1 and 0.94 mOhm-cm, respectively, when sputtered using an RF power supply.
In this study, spatial atomic layer deposition (ALD) system is employed to grow zinc oxide films (ZnO) with diethylzinc and water precursors. The H2O flow rate is varied to investigate its effect on electrical, structural and optical properties of the films. The experimental results show that the low H2O flow rates lead to a lower amount of oxygen vacancies compared to higher flow rates. The x-ray diffraction reveals the stress released and crystalline structure repair at high flow rates. The film deposited at 9 sccm corresponding to the saturation point exhibits the highest electron mobility of 32 cm²V–1s–1 and the lowest resistivity of 0.05 Ω-cm. A deposition mechanism is proposed, where the low H2O flow rate requires multiple ALD cycles to complete oxidation of surface ligands, thereby suppressing the oxygen vacancies formation. High H2O flow rates give rise to better ZnO growth, favoring the oxygen vacancies formation and stress release.
