Tuning of material properties of ZnO thin films grown by plasma-enhanced atomic layer deposition at room temperature

Pilz, Julian; Perrotta, Alberto; Christian, Paul; Tazreiter, Martin; Resel, Roland; Leising, G.; Grießer, Thomas; Coclite, Anna Maria

doi:10.1116/1.5003334

Cited by 39 publications

(46 citation statements)

References 55 publications

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“…The crystalline properties investigated by specular X‐ray diffraction (XRD) are shown in Figure . At room temperature, the ZnO films exhibit a polycrystalline pattern with a (100) texture, as reported in a previous publication . By increasing the substrate temperature, the contribution of (002) peak increases and becomes the dominant orientation.…”

Section: Resultssupporting

confidence: 80%

“…These different effects happen simultaneously, making their individual effects on the GPC difficult to distinguish. On the other hand, especially for PE‐ALD, self‐limiting growth can be achieved well below the ALD window . This raises questions about the definition and relevance of the ALD window (in PE‐ALD processes) and the often exclusive focus on properties at temperatures within the window.…”

Section: Resultsmentioning

confidence: 99%

“…The RF‐power for the plasma dose was fixed at 60 W for all depositions. The saturation behavior of the four steps was investigated at room temperature, and due to possible decomposition effects of DEZ, the saturation of the purging step after DEZ was also investigated at 250 °C. At higher temperatures, the growth was found to be self‐limiting when the recipe was fixed at 0.15 s for the DEZ dose, 22 s for the Ar purge, 8 s for the O 2 ‐plasma dose, and 15 s for the second Ar purge.…”

Section: Methodsmentioning

confidence: 99%

“…UV–vis spectroscopy (Shimadzu UV‐1800) was used to measure the transmission of the films in a wavelength range from 190 to 1100 nm, and the absorption edge could be extracted via Tauc fitting . Contributions from reflections were neglected in the analysis.…”

Section: Methodsmentioning

confidence: 99%

“…A variant is plasma‐enhanced atomic layer deposition (PE‐ALD), in which reactive plasma species are utilized as co‐reactants instead of water . The advantages of using PE‐ALD instead of thermal ALD include often a higher growth rate, improved material characteristics at lower substrate temperature, and the possibility to tune material properties by changing the plasma characteristics …”

Section: Introductionmentioning

confidence: 99%

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ZnO Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition: Material Properties Within and Outside the “Atomic Layer Deposition Window”

Pilz

Perrotta

Leising

et al. 2019

Physica Status Solidi (a)

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ZnO thin films and nanostructures are applied in various devices due to their interesting optical and electrical properties. Atomic layer deposition (ALD) of ZnO offers unique advantages such as precise thickness control, uniformity, and conformality. Using reactive plasma species as the co-reactant (PE-ALD) allows further enhancement of the material characteristics and tunable properties. The substrate temperature has been reported to be the most influential parameter in this technique, as it affects the growth per cycle (GPC) and material properties. However, an investigation on how the film properties are linked to the GPC is lacking in the literature. Herein, the temperature dependence of several material properties is found closely related to the GPC. The preferential crystal orientation switches from (100) to (002) up to the constant region of the GPC versus temperature, the so-called ALD window. Refractive index and mass density show different slopes in temperature regions outside and within the ALD window. Excitonic absorption is only found for films prepared within the ALD window, and the resistivity drops rapidly above the ALD window. Following these results, more insights can be gained on the ALD growth (especially the role of the ALD window) and ideal temperature ranges for specific applications.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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ZnO Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition: Material Properties Within and Outside the “Atomic Layer Deposition Window”

Pilz

Perrotta

Leising

et al. 2019

Physica Status Solidi (a)

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Smart Core‐Shell Nanostructures for Force, Humidity, and Temperature Multi‐Stimuli Responsiveness

Ali

Schäffner

Belegratis

et al. 2022

Adv Materials Technologies

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stimuli and transmits the information to the brain. [1] In the last decade, a substantial understanding of how this complex system behaves has been gained. [2][3][4] Nevertheless, its replication to form artificial skins is still a relatively new field with massive potential. Relying on advancements in functional materials, structural design, and state-of-art production/deposition techniques, a wide variety of single/ multi-stimuli responsive sensory systems, suitable for electronic skin (e-skin) applications, have been reported. [5][6][7][8] An efficient e-skin design requires a combination of functional materials with suitable mechanical and electrical properties, [9] in addition to the micro/nanoscale control of the layer's thickness and dimensions, which is optimized by the choice of suitable fabrication techniques.For pressure and force detection, the most common methods exploit piezoelectric, piezoresistive, or capacitive sensing. [10][11][12][13] Bao's group investigated an e-skin design based on flexible pressure-sensitive organic thinfilm transistors deploying a force-sensitive gate dielectric capacitance. The sensor has a maximum sensitivity of 8.4 kPa −1 and a fast response time of 10 ms. This was realized with a combination of microstructured polydimethylsiloxane (PDMS) gate dielectric and a high-mobility semiconducting polymer in a transistor design. The sensor relies on capacitance change due to mechanical excitations. [14] Another pressure-sensitive e-skin design, investigated by Bao's group, is realized by a composite piezoresistive material consisting of an organic polymer and nickel nanostructured microparticles. [15] Park and Jang investigated hybrid piezoelectric/piezoresistive pressure sensors based on a nanohybrid material from graphene with free-standing nanofibers of PEDOT/P(VDF-HFP). Their e-skin device impresses with a gauge factor as high as 320 under tensile strain thus showing high sensitivity to pressure with a low limit of detection of 0.5 Pa only. [16] Humidity sensors for e-skin applications have also been investigated. [17,18] Guo et al. demonstrated that a tungsten sulfite (WS 2 ) film combined with graphene electrodes and PDMS substrate exhibits a high humidity response (up to 90% relative humidity or RH) due to the change in the WS 2 conductivity. [19] Similarly, e-skin sensitivity to changes in surrounding temperature is desired and has been investigated. [20][21][22] Chen et al.A force, humidity, and temperature-responsive electronic skin is presented by combining piezoelectric zinc oxide (ZnO) and poly-N-vinylcaprolactamco-di(ethylene glycol) divinyl ether hydrogel into core-shell nanostructures using state-of-the-art dry vapor-based techniques. The proposed concept is realized with biocompatible materials in a simplified design that delivers multi-stimuli sensitivity with high spatial resolution, all of which are prerequisites for an efficient electronic skin. While the piezoelectricity of ZnO provides sensitivity to external force, the thermoresponsiveness of the hydrogel...

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Piezoelectric Properties of Zinc Oxide Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition

Ali

Pilz

Schäffner

et al. 2020

Physica Status Solidi (a)

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Zinc oxide (ZnO) thin films are deposited by plasma‐enhanced atomic layer deposition (PE‐ALD). This deposition method allows depositing stoichiometric and highly resistive ZnO films at room temperature. Despite such important requirements for piezoelectricity being met, not much is known in literature about the piezoelectric properties of ZnO thin films (<70 nm) deposited by PE‐ALD. The films are grown at different substrate temperatures to investigate the effect on crystalline and piezoelectric properties. Films deposited on flexible poly(ethylene terephthalate) (PET) generated a higher piezoelectric current (>1.8 nA) and charge (>80 pC) compared with films deposited on glass (>0.3 nA and >30 pC) due to bending effects of the substrate when mechanically excited. Furthermore, increasing the substrate temperature, during deposition, enhances the growth along the (002) crystallographic orientation, which further strengthens the generated piezoelectric current signal for mechanical excitations along the ZnO film's c‐axis.

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Tuning of material properties of ZnO thin films grown by plasma-enhanced atomic layer deposition at room temperature

Cited by 39 publications

References 55 publications

ZnO Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition: Material Properties Within and Outside the “Atomic Layer Deposition Window”

ZnO Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition: Material Properties Within and Outside the “Atomic Layer Deposition Window”

Smart Core‐Shell Nanostructures for Force, Humidity, and Temperature Multi‐Stimuli Responsiveness

Piezoelectric Properties of Zinc Oxide Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition

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