Inducing Crystallinity of Metal Thin Films with Weak Magnetic Fields without Thermal Annealing

Stefan Ručman,Jaroon Jakmunee,Pisith Singjai,Winita Punyodom

doi:10.3390/cryst8090362

Abstract

Since the discovery of thin films, it has been known that higher crystallinity demands higher temperatures, making the process inadequate for energy-efficient and environmentally friendly methods of thin film fabrication. We resolved this problem by sparking metal wires in a 0.4 Tesla magnetic field at ambient conditions under ultra-pure nitrogen flow to replace the annealing of thin films, and thus designed an environmentally friendly and energy-efficient thin film fabrication method. We employed grazing incidence X-Ray Diffraction spectroscopy to characterize crystallinity of Iron, Nickel, Copper and Tungsten thin films prepared by a sparking discharge process in the presence of 0.4 T magnetic field at an ambient temperature of 25 °C. Control experiment was conducted by sparking without a magnetic field present and using ultra-pure nitrogen flow and ambient air containing oxygen. The Iron thin film prepared in ultra-pure nitrogen flow preserved crystallinity even after one year of ageing. Nickel exhibited higher crystallinity when sparked in nitrogen gas flow than when sparked in atmospheric air and was the only element to crystalize under atmospheric air. Tungsten successfully crystalized after just 40 min of sparking and aluminium failed to crystalize at all, even after 12 h of sparking under nitrogen flow.

Highlights

The thinner a thin film is, the higher the thermal conditions required for it to crystalize [1,2,3], if it is combined with nanocomposite material or deposited on substrate material that is not able to sustain high temperatures, it represents a dead end for scaling up or commercialization [4,5].In the field of material chemistry, low temperature processing is done at temperatures of 600 ◦ C or less [6]
The texture, morphology and thickness of aluminium thin film was different if deposited in the presence of a magnetic field or without one
Using electron microscopy and AFM, we observed higher porosity of a thin film deposited without a magnetic field, whereas in the presence of a magnetic field, the texture was more compact, and the film was

Summary

Introduction

The thinner a thin film is, the higher the thermal conditions required for it to crystalize [1,2,3], if it is combined with nanocomposite material or deposited on substrate material that is not able to sustain high temperatures, it represents a dead end for scaling up or commercialization [4,5].In the field of material chemistry, low temperature processing is done at temperatures of 600 ◦ C or less [6]. The thinner a thin film is, the higher the thermal conditions required for it to crystalize [1,2,3], if it is combined with nanocomposite material or deposited on substrate material that is not able to sustain high temperatures, it represents a dead end for scaling up or commercialization [4,5]. 20–45 ◦ C) opens up new possibilities for an approach that can provide a Crystals 2018, 8, 362; doi:10.3390/cryst8090362 www.mdpi.com/journal/crystals. Crystals 2018, 8, 362 cost-effective synthesis allowing for integration of thin film with temperature sensitive substrates and providing an alternative for widely used thermal annealing. Heating-free growth and crystallization of perovskite films at room temperature [10], in ambient air, and without the use of thermal annealing was first reported by Dubey et al who found that exposure of thin film to humid air (40% RH) promoted crystallization. Radiofrequency plasma [13] (RF)

Methods

Results

Discussion

Conclusion