Anisotropy control in magnetic nanostructures through field-assisted chemical vapor deposition

Stadler, Daniel; Brede, Thomas; Schwarzbach, Danny; Maccari, Fernando; Fischer, Thomas; Gutfleisch, Oliver; Volkert, Cynthia A.; Mathur, Sanjay

doi:10.1039/c9na00467j

Cited by 5 publications

(10 citation statements)

References 34 publications

(34 reference statements)

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“…Differences in sample thicknesses may explain the difference in the percentages of photocurrent efficiency. When the light falls on the hematite film, and the electron–hole pair is generated, the electrons migrate to FTO and the holes at the surface [ 4 , 5 , 25 ]. When the film is very thin, the formation of a few excitons occurs, and when the thickness is too thick, the separation is limited by the long diffusion distance that the load carriers must travel.…”

Section: Resultsmentioning

confidence: 99%

“…Several techniques have been investigated for the synthesis of hematite nanocrystalline thin films: thermal evaporation [ 19 ], aqueous chemical growth [ 20 ], spray-pyrolysis [ 10 , 21 , 22 ], sol-gel [ 23 ], and electrodeposition methods [ 1 , 8 , 13 ]. A low-cost and solvent-free method for preparing semiconducting thin films well-suited for the preparation of nanostructures is chemical vapor deposition (CVD) [ 24 , 25 ]. In the last years, several research groups have employed the CVD technique to obtain iron oxide thin films.…”

Section: Introductionmentioning

confidence: 99%

“…In the last years, several research groups have employed the CVD technique to obtain iron oxide thin films. Thermal CVD synthesis of α-Fe 2 O 3 thin films by using different iron precursors such as carbonyls, alkoxides, and β-diketonates has been reported [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. However, it is still necessary to achieve a deep understanding of the hematite thin film growth by CVD in order to develop efficient photoelectrodes for solar photoelectrochemical water splitting.…”

Section: Introductionmentioning

confidence: 99%

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CVD Growth of Hematite Thin Films for Photoelectrochemical Water Splitting: Effect of Precursor-Substrate Distance on Their Final Properties

et al. 2023

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The development of photoelectrode materials for efficient water splitting using solar energy is a crucial research topic for green hydrogen production. These materials need to be abundant, fabricated on a large scale, and at low cost. In this context, hematite is a promising material that has been widely studied. However, it is a huge challenge to achieve high-efficiency performance as a photoelectrode in water splitting. This paper reports a study of chemical vapor deposition (CVD) growth of hematite nanocrystalline thin films on fluorine-doped tin oxide as a photoanode for photoelectrochemical water splitting, with a particular focus on the effect of the precursor–substrate distance in the CVD system. A full morphological, structural, and optical characterization of hematite nanocrystalline thin films was performed, revealing that no change occurred in the structure of the films as a function of the previously mentioned distance. However, it was found that the thickness of the hematite film, which is a critical parameter in the photoelectrochemical performance, linearly depends on the precursor–substrate distance; however, the electrochemical response exhibits a nonmonotonic behavior. A maximum photocurrent value close to 2.5 mA/cm2 was obtained for a film with a thickness of around 220 nm under solar irradiation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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CVD Growth of Hematite Thin Films for Photoelectrochemical Water Splitting: Effect of Precursor-Substrate Distance on Their Final Properties

et al. 2023

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“…[212] In general, force fields have direction and strength, which give the capability for expanding the experimental space for VD. [208] The concept of force fields is broader than electromagnetism, and many other modulations of physical parameters can be thought of as such, including ultrasound, gas, and temperature, which can affect the reaction kinetics. [205] In combination with solvophobicity and geometry of the surfaces, [53,213] these factors might enable a very complex VD pattern that could be understood and utilized better with stringent modeling and careful reaction parameter design.…”

Section: Future Directions and The Paradigm Of Toposelective Vapor De...mentioning

confidence: 99%

“…The surface shape can also directly affect selective deposition with a “parameter handle” that can easily be controlled externally. For example, magnetic fields can control the structure of the deposited material, [ 208 ] and electronic fields can control adsorbate localization even on a flat surface [ 209 ] and initiate a reaction. [ 210 ] Because sharp edges enhance potential fields near them, deposition might be localizable on top of microstructures based on the field or potential strengths and the conductivity of the substrate.…”

Section: Implications On the Vapor Deposition Paradigmmentioning

confidence: 99%

Condensation‐Controlled Toposelective Vapor Deposition in Nano‐ and Microcavities: Theory, Methods, Applications, and Related Technologies

Lovikka¹

2022

Adv Materials Inter

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fabricable while we are facing increasing complexity in, for example, microelectronics. [6,7] For these reasons, challenges such as bad pattern alignment, [8,9] or pinch-off of pores and void formation [10][11][12][13] in top-down fabrication need to be addressed. On the other hand, a continuous film causes tradeoffs in desirable properties in many nanotechnological applications, such as losing mesoporosity while increasing the mechanical properties of an aerogel [14] or reducing catalytic activity while increasing catalyst stability against sintering. [15] To counter these problems, even atomic layer deposition (ALD), a method known for its superior conformality, has been expanded into area-selective fabrication by the addition of etching and functionalization steps in the workflow. [16][17][18][19] However, additional steps make the workflow increasingly slow, complex, and dependent on surface chemistries. There is also a growing interest in area-selectivity based on properties of precursors and substrates in ALD, [20] but new requirements on precursors would narrow down potential reagents. Furthermore, even conformal methods would leave voids inside ink-bottle-shaped pores and under composite undercuts [21] because conformal methods would clog the pore mouths before filling the internal parts. These problems have very recently revoked calls for profound changes and even a paradigm shift toward selective functionalization in the nanoscale. [18,20,[22][23][24][25] Special attention should be paid to inherently non-conformal methods, especially if they are surface-selective towards cavities. This includes both surface-selective subconformal coatings, those that coat only extremities and protrusions of a substrate, and surface-selective superconformal coatings, those that fill or coat cavities.Bottom-up approaches could eliminate the aforementioned problems while reducing the needed steps for surface-selective treatments-instead of breaking or carving things smaller and using miniaturized techniques (top-down), coatings could be grown self-aligning (bottom-up). One bottom-up category is surface-shape-selective deposition. Currently, this category has limited approaches, which are often based on either anisotropic processes such as directional plasma etching [26] or reagent flux, force fields, [27] competitive adsorption, [28] or reagents and additives with specific properties. [22] Truly bottom-up gap-filling technologies, especially those free of line-of-sight limitations, Nanotechnology drives technological progress in many frontiers, from electronics to medicine, from tougher composites to adaptive surfaces. As the feature sizes are made smaller, the importance of surfaces is increased. Many of the most powerful methods for surface manipulation are variants of vapor deposition (VD). However, VD is typically not surface-selective and, therefore, extra work steps are needed to integrate the methods into nanofabrication routines. Furthermore, many fields are moving toward 3D nanostructures, which unavoidably means...

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Control of Microstructure in Iron–Carbon Thin Films by Means of Electromigration

et al. 2023

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Herein, it is demonstrated that high DC electric current densities can be used to tailor the microstructure of iron–carbon thin films. Specifically, elongated ferrite grains can be formed in a nanocrystalline matrix via a process involving electromigration‐induced carbide migration. Herein this article, the parameters that are required to produce and control elongated grain formation in the Fe(C) system are mapped out and they are interpreted in terms of carbon electromigration, and the flux divergences need to reach a critical carbon concentration for precipitate growth and migration. Possible approaches to allow more precise control of the elongated grains are discussed, as are the requirements for material systems where microstructure control through electromigration should be feasible.

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Anisotropy control in magnetic nanostructures through field-assisted chemical vapor deposition

Cited by 5 publications

References 34 publications

CVD Growth of Hematite Thin Films for Photoelectrochemical Water Splitting: Effect of Precursor-Substrate Distance on Their Final Properties

CVD Growth of Hematite Thin Films for Photoelectrochemical Water Splitting: Effect of Precursor-Substrate Distance on Their Final Properties

Condensation‐Controlled Toposelective Vapor Deposition in Nano‐ and Microcavities: Theory, Methods, Applications, and Related Technologies

Control of Microstructure in Iron–Carbon Thin Films by Means of Electromigration

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