Nanocolumnar growth of sputtered ZnO thin films

Szabó, Ondrej; Kováčová, Soňa; Tvarožek, V.; Νovotný, I.; Šutta, P.; Netrvalová, Marie; Rossberg, D.; Schaaf, Peter

doi:10.1016/j.tsf.2015.04.009

Cited by 10 publications

(2 citation statements)

References 17 publications

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“…The images suggest that AZO thin films have homogeneous morphology and are composed of granular structures. [ 43 ] It is also observed that the films show columnar growth, typical of a polycrystalline structure for a thin AZO film. [ 43 ] Also, a coalescence of these columns as the O 2 atmosphere increases until they form a uniform and homogeneous structure, causing the appearance of more dense particles seen in the image surface topography and less roughness as it is a film with more excellent continuity.…”

Section: Resultsmentioning

confidence: 99%

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

Queiroz

Filho

Feitor

et al. 2020

Physica Status Solidi (a)

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This work addresses, in an experimental and theoretical way, the influence of different oxygen pressure values on the physical and electronic properties of thin conductive and transparent oxide films of Al‐doped ZnO, with different thicknesses. A series of characterization techniques, which include X‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), optical spectrophotometry, and Hall measurements are conducted. All films have a hexagonal wurtzite structure characteristic of ZnO, with preferential orientation along the plane (002) and transmittance values, in the visible range, greater than 80%. The increase in flow oxygen up to 25% provides an increase in the film's density resulting in a decrease in electrical resistivity from 9.58 × 10−3 Ω cm to 8.14 × 10−3 Ω cm. The ab initio calculations allow to observe the distortions in the microstructure of the films attributed to the presence of impurities and to obtain the values of the total and formation energies. The values of the Mulliken population and chemical bond length are notoriously influenced by the concentration of oxygen in the atmosphere. The displacement of the valence band (VB) and the Fermi level, together with the decrease in the gap energy, reinforce the influence of oxygen gas on the electronic structure of the films.

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Section: Resultsmentioning

confidence: 99%

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

Queiroz

Filho

Feitor

et al. 2020

Physica Status Solidi (a)

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“…The residual stress in the film is given by the following equation;

normalσ = \frac{2 c_{13}^{2} - c_{33} ((), c_{11} + c_{12})}{2 c_{13}} ((), \frac{c - c_{0}}{c_{0}}) = - 233 ((), \frac{c - c_{0}}{c_{0}}),

where c ij represents the elastic stiffness constants of ZnO single crystals: c 11 = 208.8 GPa, c 12 = 119.7 GPa, c 13 = 104.2 GPa, and c 33 = 213.8 GPa . The compressive stress in the films arises because of the generation of the point defects in the film by ion beam irradiation …”

Section: Resultsmentioning

confidence: 99%

100 keV H⁺ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

Sahoo

Mangal

Mishra

et al. 2018

Surface & Interface Analysis

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We report the influence of 100 keV H + ion beam irradiation on the surface morphology, crystalline structure, and transport properties of as-deposited Al-doped ZnO (Al:ZnO) thin films. The films were deposited on silicon (Si) substrate by using DC sputtering technique. The ion irradiation was carried out at various fluences ranging from 1.0 × 10 12 to 3.0 × 10 14 ions/cm 2 . The virgin and ion-irradiated films were characterized by X-ray diffraction, Raman spectroscopy, atomic force microscopy, and Hall probe measurements. Using X-ray diffraction spectra, 5 points Williamson-Hall plots were drawn to deduce the crystallite site and strain in Al:ZnO films. The analysis of the measurements shows that the films are almost radiation resistant in the structural deformation under chosen irradiation conditions. With beam irradiation, the transport properties of the films are also preserved (do not vary orders of magnitude). However, the surface roughness and the crystallite size, which are crucial parameters of the ZnO film as a gas sensor, are at variation with the ion fluence. As ion fluence increases, the root-mean-square surface roughness oscillates and the surface undergoes for smoothening with irradiation at chosen highest fluence. The crystallite size decreases initially, increases for intermediate fluences, and drops almost to the value of the pristine film at highest fluence. In the paper, these interesting experimental results are discussed in correlations with ion-matter interactions especially energy losses by the ion beam in the material. KEYWORDS Al-doped ZnO, atomic force microscopy, ion beam irradiation, sputtering, thin film 1 | INTRODUCTION The ZnO is a direct wide band gap semiconductor. Due to being nontoxic, inexpensive, and abundant in nature, ZnO finds several potential applications in new technology such as solar cells, piezoelectric, gas sensors, and optoelectronic communication. 1,2 The ZnO has more than one stable crystal structure. It can exist in hexagonal wurtzite as well as in cubic zinc blende structure. This feature of ZnO allows us to synthesize a tetrapod-like morphology with multifunctionality. The synthesis of nano-dimensional tetrapod ZnO with various morphologies, their unique properties, and functional applications such as photocatalytic, UV photodetection, and gas sensing are reported elsewhere. 3-5 By tailoring the morphology, the properties of ZnO can be tuned for diverse applications. For instance, the quasi 1-dimensional ZnO nanowires exhibit piezo-resistivity. 6 The pure ZnO thin films show lack of stability due to thermal edging in air or corrosive environment, and native point defects such as O vacancies make it resistive. 7,8 Therefore, ZnO films are commonly doped with group II and group III metal ions such as indium (In), aluminium (Al), gallium (Ga), copper (Cu), and cadmium (Cd) to enhance its structural, optical, and electrical properties. 9 The indium (In) doping in ZnO improves both electrical and optical properties, but In is toxic and costly as well due to natural...

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Structurally Colored Physically Unclonable Functions with Ultra‐Rich and Stable Encoding Capacity

Esidir,

Ren,

Pekdemir

et al. 2024

Adv Funct Materials

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Identity security and counterfeiting assume a critical importance in the digitized world. An effective approach to addressing these issues is the use of physically unclonable functions (PUFs). The overarching challenge is a simultaneous combination of extremely high encoding capacity, stable operation, practical fabrication, and a widely available readout mechanism. Herein this challenge is addressed by designing an optical PUF via exploiting the thickness‐dependent structural color formation in nanoscopic films of ZnO. The structural coloration ensures authentication using widely available bright‐field‐based optical readout, whereas the metal oxide provides a high degree of structural stability. True physical randomness in spatial position is achieved by physical vapor deposition of ZnO through stencil masks that are fabricated by pore formation in polycarbonate membranes via photothermal processing of stochastically positioned plasmonic nanoparticles. Structural coloration emerges from thin film interference as confirmed via simulation studies. The rich color variation and stochastic definition of domain size and geometry result in chaotic features with an encoding capacity that approaches (6.4 × 105)(2752×2208). Deep learning‐based authentication is further demonstrated by transforming these chaotic features into unbreakable codes without field limitations. This ultra‐rich encoding capacity, coupled with outstanding thermal and chemical stability, forms a new cutting edge for state‐of‐the‐art PUF‐based encoding systems.

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Nanocolumnar growth of sputtered ZnO thin films

Cited by 10 publications

References 17 publications

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

100 keV H⁺ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

Structurally Colored Physically Unclonable Functions with Ultra‐Rich and Stable Encoding Capacity

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Nanocolumnar growth of sputtered ZnO thin films

Cited by 10 publications

References 17 publications

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

Structural and Optical Properties of ZnO:Al Thin Films Produced by Magnetron Sputtering with Different Oxygen Flow: An Experimental and Ab Initio Study

100 keV H+ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

Structurally Colored Physically Unclonable Functions with Ultra‐Rich and Stable Encoding Capacity

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100 keV H⁺ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications