Ion implantation of copper oxide thin films; statistical and experimental results

doi:10.1016/j.surfin.2020.100463

Surfaces and Interfaces

Volume 18, March 2020, 100463

https://doi.org/10.1016/j.surfin.2020.100463 Get rights and content

Abstract

Ion implantation is one of the interesting way to tune the electrical and optical properties of metal oxides. In this regard, doping copper oxide with nitrogen is of interest on account of its potential to enhance the properties of copper oxide. Herein, we have investigated the influence of nitrogen ion implantation on the properties of copper oxide thin films, prepared using DC magnetron sputtering. The crystal structure, surface morphology, and optical properties of pristine and ion implanted copper oxide were investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and UV–visible spectrophotometer. The results of XRD demonstrated a mixture of CuO single bond Cu₂O and Cu₂O (as dominant phase). Additionally, the ion implanted sample illustrated a lower grain compared to the pristine sample. An increase of 2–3 order was obtained in the internal strain upon implementation of nitrogen into the samples that could be ascribed to the formation of non-uniform grains and an increment in lattice imperfection.

The results of surface micrographs demonstrated a remarkable change on the surface of samples and the appearance of interconnected holes after ion implementation. The band gap was tuned and increased from 2.27 to 2.36 eV upon ion implantation that is largely owing to the influence of the quantum size of copper oxide during implantation. Our results show that the nitrogen ion implantation (N-type doping) is a useful way to tune the properties of materials that are applicable for variety of photovoltaic and optoelectronic devices. Moreover, the 3-D surface micro-texture characteristics of pristine and nitrogen ion implanted copper oxide thin films were quantitatively investigated using AFM, fractal, and stereometric analyzes.

Introduction

The challenges associated with p-type doping of oxide materials such as self-compensation and dopant solubility limits open another window to think of n-type doping of these materials. In this regard, the dopants such as transition metals, germanium, nitrogen, and silicon have been investigated so as to improve the conductivity of oxide materials [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. Nitrogen doping has attracted much attention for the oxide materials. Among oxide materials, copper oxide is a p-type material which possesses high absorption, high minority carrier diffusion length, and excellent mobility at ambient conditions. Having a high absorption coefficient in the visible region and a large direct energy band gap of about 1.2–1.5 eV make the copper oxide thin film useful for applications in solar cells [12], [13], [14], [15]. Other development illustrated that the nitrogen ion implantation or nitrogen doping copper oxide (Cu₂O:N) can be used to enhance not only the electrical conductivity but also the light absorption less than the band gap owing to the additional band located at 0.7 eV just above the valence band [16], [17].

Simulation proposed that the band gap of nitrogen-doped copper oxide increases in presence of oxygen vacancies which was in consistence with the experimental results of the Cu₂O:N deposited using sputtering method [3], [13], [17]. Nitrogen ion implantation is normally employed to tune the electrical, structural, and optical features of various thin films. This method has several pros over chemical techniques such as easy processing, control over film stoichiometry, environmentally friendly, and therefore, it is used for the preparation of many semiconductor thin films and devices. In ion implantation process and order to tune the optical, electrical, and structural features, impurity ions are projected into the target material and the influence of ion implantation is usually significant on nanostructured materials compared to their bulk counterpart mainly owing to the large aspect ratio of nanomaterials.

So far, there are limited investigations on nitrogen-doped, cross-linking, and functionalization of copper oxide thin films. Therefore, further attention is needed on nitrogen ion implantation of Cu₂O thin films. Literature search reflected very few studies on effect of low energy ion irradiation on nanoparticles and nanocrystalline thin films [18], [19], [20]. The motivation of the present study is to study the effect of ion implantation using low energy beam as a post deposition method on copper oxide thin film prepared by pulsed DC magnetron sputtering technique.

In the current work, the surface of copper oxide thin film was bombarded using a low energy nitrogen ion beam by an ion implantation set up. Copper oxide films were prepared using DC magnetron sputtering method on glass substrate and the effect of nitrogen ion implantation on the microstructure, surface morphology, and optical properties of the copper oxide films was investigated by means of X-ray diffraction (XRD) with Cu K?? radiation (1.5405 Angstrom), atomic force microscope (AFM), and UV-visible spectrophotometer. The emphasis is on the changes in the structural, optical and morphological properties of Cu2O thin films.

Section snippets

Experimental details

Preparation of copper oxide thin films includes three parts: first, prior to the deposition of copper oxide thin films, the glass substrates were ultrasonically washed for 10 min in ethanol and acetone and then the Cu₂O thin films were deposited using a DC magnetron cylindrical sputtering tool. As shown in Fig. 1, a copper target (99.99% purity) of 20 cm height and 3 cm diameter was used to sputter the copper oxide films. The deposition distance and the puttering DC power were 3 cm and 120 W

Crystallographic structure

The crystal structure and phase identification of Cu₂O thin films were studied using X-ray diffraction (XRD) and a source of CuKα with wavelength λ = 1.5406 Å. The XRD patterns were measured in the range of 2θ =10°−90° with a step size 0.04°. The XRD patterns of nitrogen doped Cu₂O thin films are depicted in Fig. 2. As can be seen, the pristine or un-doped samples showed a high degree of crystallinities, while a mixture of CuO single bond Cu₂O phases with Cu₂O as the dominant phase was evidently observed.

Conclusions

A DC magnetron sputtering technique was employed with a nitrogen ion beam of 30 keV energy to prepare copper oxide films. The obtained XRD results illustrated a high crystallinity of CuO single bond Cu₂O mixed phases with a majority of Cu₂O phase. Additionally, the grain size reduces after nitrogen ion implantation. Furthermore, the increase in the strain distribution is attributed to the influence of grain refinement or a high dislocation density upon ion implantation. The FESEM images showed a negligible

CRediT authorship contribution statement

Azadeh Jafari: Conceptualization, Methodology, Writing - original draft. Khashayar Tahani: Investigation, Data curation. Davoud Dastan: Conceptualization, Writing - review & editing, Supervision. Sima Asgary: Visualization, Investigation. Zhicheng Shi: Validation, Supervision. Xi-Tao Yin: Resources, Formal analysis. Wen-Dong Zhou: Software, Validation. Hamid Garmestani: Supervision. Ştefan Ţălu: Formal analysis.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (51)

C. Yang et al.
Mater. Lett
(2018)
B. Balamurugan et al.
Thin Solid Films.;
(2001)
H. Zuo et al.
Mater. Lett
(2020)
C. Malerba
Energy Mater. Sol. Cells
(2012)
X. Zhu et al.
Compos. Part A
(2019)
W. Hu et al.
J. Alloys Compd
(2020)
M. Öztas et al.
Mater. Lett
(2007)
S.K. Zheng et al.
Vacuum,;
(2002)
M. Oztas et al.
Mater. Lett
(2007)
D.C. Agarwal et al.
Surf. Coat. Technol
(2009)

K.L. Narayanan et al.

Nucl. Instrum. Methods

(1997)

A.J. Perry et al.

Surf. Coat. Technol

(1992)

L. Liu et al.

Tribol. Int

(2019)

X.-.T. Yin et al.

J Alloys Compd

(2019)

S. Rezaee et al.

Results Phys

(2017)

A. Akhundi et al.

Catal. Rev

(2019)

W. Ching et al.

Phys. Rev. B

(1989)

D. Dastan et al.

Macromol. Symp

(2015)

X.-.T. Yin et al.

Nanomater.,

(2019)

D. Dastan et al.

Sci. Mater. Electron

(2016)

Z. Shi et al.

J. Mater. Chem. A

(2017)

D. Dastan et al.

Adv. Sci. Lett.

(2016)

Y.S. Lee

Mater. Chem. A

(2013)

S. Abbasi et al.

Int. J. Environ. An. Chem.

(2019)

L. Aljerf et al.

Open J. Chem.

(2019)

Cited by (104)

On the substrate heating effects on structural, mechanical and linear/non-linear optical properties of Ag–Mn co-doped ZnO thin films
2024, Optical Materials
Optimization of the physical properties of ZnO thin films doped with different elements opens new opportunities for the application of these materials in different fields. Consequently, it is crucial to thoroughly explore the correlation of their structural, mechanical, and optical properties. In this paper, pure and Ag–Mn co-doped ZnO thin films were deposited by rapid thermal evaporation (RTE) method on glass substrates with the same Ag (5%)-Mn (5%) content at different substrate temperatures (room temperature, 200 °C and 400 °C). Subsequently, the samples were then annealed at 400 °C for 1 h. The prepared thin films were characterized by many techniques including XRD, XPS, SEM, EDS, Nanoindentation and UV–Vis–NIR spectroscopy. XRD analysis showed that the annealed layers have hexagonal wurtzite structure and the crystallinity rises as the substrate temperature increases. The elemental analysis of the films investigated by XPS and EDS which revealed the presence of C, Zn, Ag, Mn and O atoms for all layers. The morphological aspect performed by SEM revealed the apparition of nanoparticles of silver and ZnO. Nanoindentation measurements showed that the hardness increases from 9.43 to 12.44 GPa. The optical transmission of the films decreases with doping and with substrate heating, reaching 70–81 %. These variations are due to the structural and morphological changes related to the effect of co-doping and substrate heating.
Time-domain thermoreflectance measurement of the thermal diffusivity of Nb thin films
2024, Thin Solid Films
Nb-coated Cu superconducting radiofrequency (SRF) cavities are of interest as a possible alternative to bulk Nb cavities for particle accelerators due to the high thermal conductivity of Cu and its lower cost than Nb. Studying the thermal diffusion properties in Nb thin films on Cu is important for developing Nb-coated Cu SRF cavities. In the present study, the thermal diffusivity of 100‒800 nm Nb films on Cu is measured by time-domain thermoreflectance (TDTR). The thermal diffusivity is obtained from a curve fit of the TDTR signal to a one-dimensional Fourier heat diffusion model over a time extending from 25 to 985 ps after laser-surface interaction. The film was examined by atomic force microscopy and scanning electron microscopy. The grain size and thermal diffusivity increase with film thickness. The thermal diffusivity reaches a value similar to that reported for bulk Nb for the 400 and 800 nm films, for which the average grain size is 47 ± 13 nm and 68 ± 18 nm, respectively. TDTR measurement for the 400-nm film taken over the temperature range of 293 to 40 K showed that the thermal diffusivity increases as the temperature is reduced. The results indicate that grain boundaries reduce the thermal diffusivity of the Nb film and, therefore, must be considered in Nb-coated Cu SRF cavities.
Effect of polarization electric field in photodegradation over ε-Cd(IO<inf>3</inf>)<inf>2</inf> photocatalyst against antibiotics and dyes
2024, Ceramics International
The efficient photogenerated carriers separation is the key factor in enhancing the activity of photocatalysts to solve environmental pollution problems. The internal polarized electric fields in polar materials most likely provide a more direct and stronger driving force for photogenerated carriers separation. Here, we investigate polar ε-Cd(IO₃)₂ (CIO) with two different morphologies as an efficient photocatalyst for the photodegradation of antibiotics and dyes. According to the theoretical calculation of the ratios of m_h*/m_e* along three different crystal axis directions, the photogenerated carrier separation efficiency along the c-axis direction is the largest, which matches the direction of the polarized electric field in the crystal. The internal polarized electric field promotes the separation of photogenerated carriers, leading to a high transfer efficiency of the catalyst. Moreover, photodegradation experiments demonstrate that the photocatalytic activity of CIO-1 is approximately 3 times that of TiO₂ P25. This study provides some insights that might aid the development of polar photocatalysts with superior performance.
MD simulation study on the microstructural evolution of single-crystal Fe with pre-existing defects by Cr ion implantation
2024, Surfaces and Interfaces
In this study, we present the molecular dynamics simulation of metal ion implantation, investigating the strengthening mechanism from a microstructural perspective. A single crystal Fe with pre-existing defects is constructed based on actual dislocation density and the effects of Cr ion implantation are investigated. Additionally, nanoindentation simulations are conducted to analyze the mechanical properties of workpieces with and without ion implantation. Effects of implantation energy and dose on the microstructure and hardness of workpieces are analyzed. The results indicate that (i) ion implantation introduces FeCr bonds with higher bond energy while reducing the original FeFe bond energy, (ii) increasing implantation energy and dose corresponds to a greater number of point defects and a higher amorphous structures proportion, (iii) the microstructure transformed by ion implantation promotes dislocation nucleation during nanoindentation, (iv) ion implantation enhances workpiece hardness due to the dual effects of interstitials impeding dislocation motion and the heightened mutual obstruction attributed to a higher dislocation density. Notably, the hardness initially enhances with increasing implantation energy and dose, followed by a slight decrease. The computational approach in this paper can serve as a valuable tool for studying the microstructural evolution of metal ion implantation by molecular dynamics simulations.
Substrate-dependent fractal growth and wettability of N+ ion implanted V<inf>2</inf>O<inf>5</inf> thin films
2023, Applied Surface Science
Wettability of active material surface affects the electrolyte and electrode-material interaction in electrochemical applications. An increase in the V₂O₅ electrode's wetting behaviour allows for better contact with the electrolyte. The surface properties of the V₂O₅ sample were examined in order to evaluate its wettability. In this work, the surface growth of V₂O₅ thin films on three different substrates (glass, silicon, and sapphire) after 16 keV N⁺ ion implantation is presented as a function of ion dose. Thin films of 500 nm V₂O₅ deposited on different substrates show the formation of the nanocrystalline structure over the surface after thermal annealing. Silicon substrate shows the formation of V₂O₅ nanorods over the surface. Surface morphology shows the growth dynamics of the surface in terms of roughness (α) and growth (β) exponents. Lateral growth of surface features has been quantified in terms of co-relation length (ξ) and fractal dimensions (D_f). The scaling laws studies of the surfaces in terms of exponents and co-relation length shows the role of N⁺ implantation in structural modifications. Furthermore, wetting dynamics have been co-related with fractal growth of the films under ion implantation. The contact angle of V₂O₅ thin films is found to be higher for V₂O₅ nanorods on silicon substrate as compared to crystallite grains on sapphire. The present study showed that the surface morphology and wettability of V₂O₅ are mainly substrate-dependent and can be controlled by surface fractal parameters.
Ion implantation as an approach for tuning of electronic structure, optical, morphological and electrical transport properties of sputtered molybdenum disulfide thin films
2023, Materials Science in Semiconductor Processing
Molybdenum disulfide (MoS₂) thin films have acquired increasing consideration in the field of low-dimensional electronics as device-active layers and also in hydrogen evolution reaction (HER) as catalysts in distinct electrochemical processes. Thus, for distinct applications, extensive scalable fabrication techniques with tunable MoS₂ properties are significant. To possess tunable efficiency of various device applications at nanoscale it is significant to acquire control over the density of defects, although attaining with direct growth techniques remains a significant issue. Here we illustrate a robust and effective approach to tailor the density of defects using Au ion implantation. In the present work, we illustrate the scalable technique i.e. magnetron sputtering for the fabrication of MoS₂ thin films, subsequently, ion implantation with 80 keV Au ions at a distinct fluence of 1 × 10¹⁵ and 5 × 10¹⁵ ions/cm² was carried out. Striking deviations were remarked in nanostructure and depth distributions of the resultant thin films of MoS₂. Pristine and ion implanted thin films were characterized to comprehend the morphological, electrical transport and electronic structure properties. The surface micrographs’ results revealed noteworthy alterations in the thin films’ surface roughness. The modifications induced by low energy Au ion implantation in core-level electronic structure and atomic bonding was probed by XPS and Raman spectroscopy technique. The electrical properties of these films were studied to demonstrate the scattering and conduction mechanisms. The present work contributes to the significant passage of tailoring 2D MoS₂ thin films’ electronic structure, optical and morphological properties through doping and defects formation by low energy ion beam implantation to extend their practical device applications.

View all citing articles on Scopus

View full text

Published by Elsevier B.V.

Ion implantation of copper oxide thin films; statistical and experimental results

Abstract

Introduction

Section snippets

Experimental details

Crystallographic structure

Conclusions

CRediT authorship contribution statement

Declaration of Competing Interest

Mater. Lett

Thin Solid Films.<b>;

Mater. Lett

Energy Mater. Sol. Cells

Compos. Part A

J. Alloys Compd

Mater. Lett

Vacuum,<b>;

Mater. Lett

Surf. Coat. Technol

Nucl. Instrum. Methods

Surf. Coat. Technol

Tribol. Int

J Alloys Compd

Results Phys

Catal. Rev

Phys. Rev. B

Macromol. Symp

Nanomater.,<b>

Sci. Mater. Electron

J. Mater. Chem. A

Adv. Sci. Lett.

Mater. Chem. A

Int. J. Environ. An. Chem.

Open J. Chem.