Chemical evolution of target surfaces during RF magnetron sputtering and its effect on the performance of TCO films

Wu, Junyan; Wang, Wenwen; Chen, Fei; Shen, Qiang; Zhang, Lianmeng

doi:10.1016/j.apsusc.2019.07.021

Cited by 8 publications

(5 citation statements)

References 29 publications

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“…During the growth of transparent conductive oxide films, it has been revealed that the selection of targets can significantly influence the optical properties of the films [30][31][32][33][34]. Additionally, arc discharge induced by target conditions has been a common phenomenon for sputtering cathodes, particularly in reactive sputtering [35].…”

Section: Introductionmentioning

confidence: 99%

“…Insufficient cooling can result in target material cracking, reducing the target's lifespan and affecting deposition process repeatability [31]. Furthermore, variable sputtering rates at grains, grain boundaries, and holes generate nodules on the surface, leading to irregular morphology [32]. In plasmas, most of the voltage drop occurs within a very thin sheath on the target surface.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Sputtering Target Density on the Crystal and Electronic Structure of Epitaxial BaTiO3 Thin Films

Qi,

Peng,

et al. 2024

Crystals

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Barium titanate (BaTiO3) is a promising material for silicon-integrated photonics due to its large electro-optical coefficients, low loss, high refractive index, and fast response speed. Several deposition methods have been employed to synthesize BaTiO3 films. Magnetron sputtering is one of these methods, which offers specific advantages for growing large-scale films. However, there is a scarcity of studies investigating the effect of sputtering target density on the quality of BaTiO3 films. Therefore, this study aims to uncover the effect of sputtering targets on the crystal and electronic structures of epitaxial BaTiO3 thin films. Two BaTiO3 ceramic targets were sintered at different densities by altering the sintering temperatures. The crystal structure and chemical composition of the targets were then characterized using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Subsequently, BaTiO3 epitaxial films were grown by magnetron sputtering using these two targets. The crystal and electronic structures of the BaTiO3 films were analyzed using high-resolution X-ray diffraction, X-ray photoemission spectroscopy, atomic force microscopy, and spectroscopic ellipsometry. Notably, the BaTiO3 films grown with high-density targets show superior quality but contain oxygen vacancies, whereas those films synthesized with low-density targets display high surface roughness. These findings provide insights into the effect of sputtering target density on the crystal and electronic structures of epitaxial BaTiO3 thin films.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Sputtering Target Density on the Crystal and Electronic Structure of Epitaxial BaTiO3 Thin Films

Qi,

Peng,

et al. 2024

Crystals

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“…The values of the electron and holes Solar 2021, 1 31 mobility are also highly important considering the potential of this material in applications such as TCO: thanks to this, ZnO exhibits high charge carrier mobilities as compared to other compounds used in photovoltaic devices [17]. Different technologies for the preparation of TCOs layers are used, predominantly physical techniques such as magnetron sputtering and chemical vapor deposition [18], instead of chemical routes (sol-gel or spray pyrolysis) [19]. In general, chemical methods are promising ways for TCOs production due to their efficient material use and high throughput.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Electrical Properties of Alkali-Doped ZnO Thin Films with Chemical Process

Cuadra

Porcar

Fraga

et al. 2021

Solar

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Doped ZnO are among the most attractive transparent conductive oxides for solar cells because they are relatively cheap, can be textured for light trapping, and readily produced for large-scale coatings. Here, we focus on the development of alternative Na and K-doped ZnO prepared by an easy low-cost spray pyrolysis method for conducting oxide application. To enhance the electrical properties of zinc oxide, alkali-doped Zn1−x MxO (x = 0.03) solid solutions were investigated. The resulting layers crystallize in a single hexagonal phase of wurtzite structure with preferred c-axis orientation along a (002) crystal plane. Dense, well attached to the substrate, homogeneous and highly transparent layers were obtained with great optical transmittance higher than 80%. The optical energy band gap of doped ZnO films increase from 3.27 to 3.29 eV by doping with Na and K, respectively. The electrical resistivity of the undoped ZnO could be decreased from 1.03 × 10−1 Ω.cm to 5.64 × 10−2 Ω.cm (K-doped) and 3.18 × 10−2 (Na-doped), respectively. Lastly, the carrier concentrations increased from 5.17 × 1017 (undoped ZnO) to 1 × 1018 (doped ZnO).

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“…Although some research has been done on the analysis of sputtered thin films, the alteration of the target microstructure as a result of the sputtering process has been severely overlooked. It is well known that the destructive plasma–microstructure interactions occurring on the surface of the target can lead to a ‘racetrack’ phenomenon which is clearly visible to the naked eye (Nakano et al ., 2015; Wu et al ., 2019). Furthermore, experimental studies have shown that during plasma‐enhanced chemical vapour deposition, the resulting product morphology is greatly influenced by the plasma parameters (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…These include gas composition (Bose et al ., 2018; Ţălu et al ., 2018), flow rate/pressure (Ma et al ., 2019; Lee et al ., 2020; Shakoury et al ., 2020), deposition time (Dallaeva et al ., 2012; Ma et al ., 2019; Lee et al ., 2020), deposition rate (Taheriniya et al ., 2018), power (Ma et al ., 2019; Lee et al ., 2020), distance of substrate from target (Sangwaranatee et al ., 2018), substrate temperature (C. Taheriniya et al ., 2018; Ma et al ., 2019; Rajabi Kalvani et al ., 2019) and the target fabrication process (Wu et al ., 2012, 2019; Liu et al ., 2020). Since the target itself is one of the key factors contributing to the microstructure of the substrate, the evaluation of plasma–microstructure is key to not only better understanding the process but also to allow for optimisation (Dallaeva et al ., 2012; Wu et al ., 2019; Chen et al ., 2020). When competing phases occur, secondary phases may emerge leading to various effects such as Zener pinning that ultimately affect the local chemical reactivity (Huang et al ., 2018; Thiruvalluvan et al ., 2018).…”

Section: Introductionmentioning

confidence: 99%

Quantitative SEM characterisation of ceramic target prior and after magnetron sputtering: a case study of aluminium zinc oxide

Jahangiri

Kalvani

Shapouri

et al. 2020

Journal of Microscopy

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Summary Till now electron microscopy techniques have not been used to evaluate the plasma–target interactions undergone during the magnetron sputtering process. The destructive nature of this interaction severely alters the target microstructure. Utilising quantitative microscopy techniques can shed light on the complex plasma and solid‐state processes involved which can ultimately lead to improved functional thin film deposition. As a representative functional material, aluminium‐doped‐zinc oxide (AZO) is an upcoming alternative to conventional transparent electrode wherein the process optimisation is of great importance. In this paper, we evaluate the pre‐ and post‐sputter field emission scanning electron microscopy (FESEM) data for ceramic AZO target fabricated at three final sintering temperatures (1100°C, 1200°C and 1300°C). In all cases, grain boundaries are merged in addition to a visible reduction in the secondary phases which makes segmentation‐based image analysis challenging. Through surface statistics (i.e. fractal dimension, autocorrelation length, texture aspect ratio and entropy) as a function of magnification we can quantify the electron microscopy image of the microstructure. We show that the plasma–microstructure interaction leads to an increase in autocorrelation length, texture aspect ratio and entropy for the optimum AZO ceramic sputtering target sintered at 1200°C. Furthermore, a maximum reduction in fractal dimension span (as determined by exponential regression) is also observed for 1200°C. In addition to the evaluation of plasma effects on sintering, our approach can provide a window towards understanding the underlying thin film growth mechanisms. We believe that this technique can be applied to the defect characterisation of a wide range of polycrystalline ceramic sputtering targets (e.g. ITO, CZTS, GAZO and so on) with the ultimate goal of improving the magnetron sputtering process and the resulting functional thin film. Lay Description Magnetron sputtering allows scientists to make functional thin films on the order of the nanoscale. In this technique, atoms are plucked from a ‘target’ then placed onto a substrate forming a thin nanometric film: all thanks to magnets, a special power supply and the fourth state of matter (plasma). Understanding what is going on and how to make a ‘good’ thin film is important for making better light emitting diodes, solar cells and light sensors. Scientists use electron microscopy to see what is going on in the microstructure of the sputtered thin films to fine tune the sputtering recipe. Here, for the first time, we have applied electron microscopy to see the surface of the microstructure before and after magnetron sputtering. This will help us understanding the plasma–microstructure interaction allowing us to make more informed decisions when fine‐tuning the sputtering process to get improved thin films. This is a case study of aluminium‐doped zinc oxide (AZO) target that could potentially replace indium tin oxide (ITO), which is widely used as a tra...

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Chemical evolution of target surfaces during RF magnetron sputtering and its effect on the performance of TCO films

Cited by 8 publications

References 29 publications

The Effect of Sputtering Target Density on the Crystal and Electronic Structure of Epitaxial BaTiO3 Thin Films

The Effect of Sputtering Target Density on the Crystal and Electronic Structure of Epitaxial BaTiO3 Thin Films

Enhanced Electrical Properties of Alkali-Doped ZnO Thin Films with Chemical Process

Quantitative SEM characterisation of ceramic target prior and after magnetron sputtering: a case study of aluminium zinc oxide

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