Helical and square-spiral copper nanostructures: The effect of thickness and deposition conditions on the structural and optical properties

We have investigated the effect of thickness and deposition conditions on the structural and optical properties of nanostructured copper (Cu) thin films, deposited using e-beam glancing angle deposition. In the first series of experiments, samples were deposited in the form of helical nanostructures, to the thicknesses of 160 nm, 280 nm, 450 nm and 780 nm. The second set of the samples was fabricated in the form of zigzag and square-spiral nanostructures to a thickness of approximately 300 nm, by using different azimuthal rotations (φ = 180o, 90o, 45o, 22.5o and 11o). Field-emission scanning electron microscopy and high-resolution transmission electron microscopy were utilized to explore morphological and structural properties, while optical studies were done using spectroscopic ellipsometry. The results showed that for both series of the samples the deposited structures are porous with nanometer-sized particles. Detailed analyses of optical properties revealed that the thickness of the films had a significant impact on the dielectric function of Cu structures. With increasing the thickness from 160 nm to 780 nm the surface plasmon resonance (SPR) peak was shifted from 1.31 eV to 1.05 eV. Changes in SPR peak position were associated with the growth mechanism and the size of deposited nanostructures. For the second series of the samples, it was found that as the azimuthal rotation decreases, deposited nanostructures become more porous with larger number of grown arms. Optical analysis showed that the properties of the grown Cu films are greatly influenced by the deposition conditions. By decreasing the φ parameter, SPR peak was shifted from 1.19 eV to 0.75 eV, which can be correlated with the size distribution and agglomeration of Cu nanoparticles.IX International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; August 28 - September 1, 2023; Belgrad

Influence of In+ ions implantation in GaAs and Si on their optical characteristics

In this work we studied the influence of In+ ion implantation on structural and optical characteristics on semiconductors with direct (GaAs) [1] and indirect (Si) [2] band gap. A plenty of information on physical properties of various semiconductor materials can be obtained from optical spectra. In order to determine optical parameters, refraction index and extinction coefficient, we employed spectroscopic ellipsometry as a very useful technique. The parameters of the implantation process and the optical properties of the implanted GaAs and Si wafers are discussed with particular emphasis on the SWIR (Short Wavelength Infrared) region. In+ ions were implanted into n-type GaAs (100) and n-type Si (100) at an acceleration energy of 60 keV with doses of 1x1014 ion/cm2 , 5x1014 ion/cm2 , 1x1015 ion/cm2 and 2x1015 ion/cm2 in both cases. The change of the optical parameters in the subsurface region of the GaAs and Si wafers caused by implanted In+ ions is observed comparing the values of ellypsometric data and energy gap (Eg) of unimplanted and implanted wafers. In order to evaluate the crystallinity of the samples we used TEM microscopy.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

Indium ion implantation effects on the structural, optical and electrical properties of GaAs and Si wafers

In this paper we report a study on the effects of implanted In+ ions into GaAs and Si - semiconductors with direct and indirect band gap, respectively. Both systems, (In,Ga)As and (In)Si, are of great interest for fundamental investigations of their structures as well as for the development of technological applications with enhanced electronic and optical properties. In+ ions were implanted into n-type GaAs (100) and n-type Si (100) at acceleration energy of 60 keV and the fluences of 1×1014 ion/cm2, 5×1014 ion/cm2, 1×1015 ion/cm2 and 2×1015ion/cm2.It is well known that after ion implantation process substrate crystal structure is quite damaged due to the formation of point defects and dislocations which can strongly influence the semiconducting properties. In order to remove structural damage, after implantation all samples were annealed by rapid thermal annealing at temperatures 900oC1000oC. As-implanted and annealed samples were characterized for the structural changes and results are presented together with optical and sheet resistance measurements. Change in crystallinity of the samples was monitored by transmission electron microscopy, while chemical composition was determined by energy dispersive X-ray spectroscopy. Spectroscopic ellipsometry in the wavelength range 260 nm-2066 nm was performed in order to determine optical parameters and change in energy band gap. Atomic force microscopy was used to determine changes in surface roughness. Damage introduction during ion irradiation and its removal during a thermal annealing are key issues which are highlighted.VIII Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 23-25, 2019; Belgrad

Unconventional order/disorder behaviour in Al–Co–Cu–Fe–Ni multi-principal element alloys after casting and annealing

The effect of Cu concentration on the order/disorder behaviour of the AlCoCuxFeNi (x = 0.6 to 3.0) multi-principal element alloys was investigated. BCC and/or FCC phases were observed in the microstructures of the alloys after casting and annealing at 1050 ◦C followed by slow cooling. Interesting is that the alloys form ordered structures after casting and disordered structures after annealing and slow cooling, while the opposite would be expected. The ordering in the as-cast state is explained by the strong affinity of Al to transition metals, which results in the formation of supercell structures having sublattices occupied by certain elements only. Disordering after annealing has two reasons. Either the phase is composed of nearly pure element (Cu) and is disordered by default or it is composed of randomly distributed nano-segregated regions within a single phase resulting in a uniform distribution of all elements in the sublattices and therefore appearing to be macroscopically disordered. The reason for the formation of such nano-segregated areas might reside in the reduction of Gibbs free energy due to the annealing by the interplay between enthalpy and entropy

Properties of Zig-Zag Nickel Nanostructures Obtained by GLAD Technique

Zig-zag structure of the nickel thin film has been obtained using Glancing Angle Deposition (GLAD) technique. Glass substrate was positioned 75 degrees with respect to the substrate normal. The obtained nickel thin film was characterized by X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and Atomic Force Microscopy. Surface energy of the deposited thin film was determined by measuring the contact angle using the static sessile drop method

Synthesis and Characterization of Na0.4MnO2 as a Positive Electrode Material for an Aqueous Electrolyte Sodium-ion Energy Storage Device

Due to the increasing use of batteries in everyday life and in industry, there is a need for developing cheaper batteries than the widely used lithium ion batteries. Lower price and higher abundance of sodium compared to lithium mineral resources intensified the development of Na-ion batteries. Aqueous lithium/ sodium rechargeable batteries have attracted considerable attention for energy storage because they do not contain flammable organic electrolytes as commercial batteries do, the ionic conductivity of the aqueous electrolyte is about two orders of magnitude higher than in non-aqueous electrolyte and the electrolyte salt and solvent are cheaper. Various materials such as manganese oxides, vanadium oxide and phosphates have been used as electrode materials (cathodic and anodic) in sodium batteries due to high sodium intercalation ability in both, organic and aqueous electrolytes. The most frequently used type of manganese oxides are Li–Mn–O or Na–Mn–O systems due to their tunnel or layered crystal structures which facilitate the lithium/sodium intercalation-deintercalation. In this work, a glycine-nitrate method (GNM) was applied for the synthesis of cathode material Na0.4MnO2

Optical properties of copper helical nanostructures: the effect of thickness on the SPR peak position

In this study, we have investigated the effect of thickness on the structural and optical properties of copper (Cu) helical nanostructures. Thin films with thicknesses of 160 nm, 280 nm, 450 nm, and 780 nm were obtained by e-beam glancing angle deposition. The morphology and the microstructure were studied by field emission scanning electron microscopy, x-ray diffraction and transmission electron microscopy, while for the optical analysis measurements spectroscopic ellipsometry was used. The results show that the deposited structures are porous with nanometer-sized crystallites preferentially oriented along (111) planes, as well as that the diameter of the helices increases with thickness. Detailed analyses of optical properties have demonstrated that the dielectric function of Cu structures is greatly influenced by the films thicknesses. With increasing thickness from 160 nm to 780 nm, the surface plasmon resonance peak was shifted from 1.31 eV to 1.05 eV, which was correlated with the growth mechanism and the size of deposited nanostructures

Microstructural Analysis of Thermally Treated Geopolymer Incorporated with Neodymium

The following investigation presents the thermal treatment of geopolymer at 300 °C, 600 °C and 900 °C. We investigated what happens to the geopolymer base when incorporated with 1% and 5% of neodymium in the form Nd2O3. A total of six samples were synthesized. Geopolymer 1 contained 1% and geopolymer 2 contained 5% Nd2O3, and these samples were treated at 300 °C; then, samples geopolymer 3 and geopolymer 4 also had the same percentage composition of Nd2O3 and were treated at 600 °C, while samples geopolymer 5 and geopolymer 6were treated at 900 °C. Physical and chemical changes in the aluminosilicate geopolymer matrix were monitored. The incorporation of rare earths into the polymer network of aluminosilicates has been proven to disrupt the basic structure of geopolymers; however, with increased temperatures, these materials show even more unusual properties. Diffuse reflectance infrared Fourier transform (DRIFT) analysis showed that the intensity of the vibrational band decreases with the increase in temperature during thermal treatment, suggesting alterations in the chemical structure of the geopolymers. Transmission electron microscopy (TEM) analysis showed that the diameter of the nanoparticles containing Al2O3 is in the range 5–10 nm, while larger crystallites range from 30 to 80 nm. Scanning electron microscopy (SEM) analysis revealed that the temperature of the thermal treatment increases to 300 °C and 600 °C; the porosity of geopolymer increases in the form of the appearance of large pores and cracks in material. X-ray photoelectron spectroscopy (XPS) analysis was used to investigate the surface chemistry of geopolymers, including the chemical composition of the surface, the oxidation state of the elements, and the presence of functional groups. The UV/Vis spectra of the synthesized geopolymers doped with Nd3+ show interesting optical properties at 900 °C; the geopolymer matrix completely disintegrates and an amorphous phase with a rare-earth precipitate appears

Crosslinking of rare earth ions into aluminosilicate inorganic polymer

Rare earth oxides have been broadly utilised in different research areas due to their unique properties. This research aims to examine the effect of Nd and Sm in the form of oxide addition in the metakaolin-based geopolymer matrix. Metakaolin-based geopolymers with the addition of different percentages of Sm2O3 and Nd2O3 (S1-S6) were synthesised. Samples contained 0.1% Sm; 1% Sm; 5% Sm, and 0.1% Nd, 1% Nd, and 5% Nd. The focus was on monitoring the polymerisation process using the DRIFT method for 7, 14, 21 and 28 days. The phase composition of the samples was confirmed by the XRD method, while the morphology of the samples was analysed by SEM analysis. After 28 days, due to the polymerisation process, the binding of Neodymium and Samarium ions were incorporated into the structure.X Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 26-27, 2022; Belgrad

Nickel vertical posts: Influence of thickness on magnetic and optical properties

In the present study we have investigated the influence of the nickel (Ni) thin films thicknesses on their structural, magnetic and optical properties. Nickel vertical posts were deposited by Glancing Angle Deposition technique, at the angle of 85o .The films were grown to the thicknesses of 50 nm, 80 nm, 110 nm and 140 nm onto the glass slide substrates, which were rotated at the constant rate during the deposition process. After the deposition, the samples were characterized by Scanning ElectronMicroscopy (SEM) and it was found that the thin films are porous and that the diameter of the columns increases from 18 nm to 29 nm with increasing thickness.X-ray photoelectron spectroscopy was used in order to determine the chemical composition of the samples, as well as the identification of the compounds present in the deposited thin films. It was shown that the metallic Ni is the dominant component, while the deconvolution of the oxygen line revealed the presence of NiO and Ni(OH)2. Magnetic measurements of Ni thin films were accomplished by Magneto-Optical Kerr effect Microscope at room temperature. Based on the obtained results it can be seen that the deposited nickel samples possess uniaxial magnetic anisotropy. Also, it was noticed that the coercivity increases with thickness up to 150 Oe, for the 110 nm thick sample and then decreases to the value of 115 Oe. For thinner films, magnetic properties are mainly affected by the diameter of the columns, while for the thicker samples, the mechanism of the column growth determines their characteristics. Optical and electrical properties of nanostructured nickel thin films were investigated by spectroscopic ellipsometry and four-point probe, respectively. According to the ellipsometric measurementsit was found that as the thickness of the deposited samples increases plasma frequency (ωp) also increases, and the damping factor (Γd) decreases. An increase in the plasma frequency means that the density of conducting electrons is higher forthe thicker samples, while the decrease in Γd indicates their better structural arrangement and lower concentration of defects.From the ellipsometric measurements, also, was observed the decrease of the refractive index values with increasing the film thickness, which is due to the lower optical density of the samples. Besides, higher values of the column width of the thicker Ni films lead to the reduced scattering of the conduction electrons at their boundaries and consequently increase both conductivity and extinction coefficient. Indeed, four-point probe measurements revealed that the electrical resistivity decreases from 4.98102μΩcm to 0.44102μΩcm, with increase film thickness from 50 nm to 140 nm. Lower values of electrical resistivity are probably due to the larger column diameter and lower defects density, as a result of column connecting during the film growth.VIII International School and Conference on Photonics and HEMMAGINERO workshop : PHOTONICA2021 : book of abstracts; August 23-27, 2021; Belgrad