Textured Films Research Articles

Evidence of silicon substrate effect on improved electrolytic performance of Sb-SnO2 thin films/polycrystalline Si/chromate solution structure

The photo-electrochemical properties of pure SnO2 and Sb-doped SnO2 grown on Si substrate (Sb(%)/SnO2/Si) thin films synthesized by the Atmospheric Pressure Chemical Vapor Deposition (APCVD) were studied. The nature of the substrate and its chemical composition were assessed. SnO2 and Sb(%)/SnO2/Si films crystallize in a tetragonal rutile-structure and the Sb-doping does not affect the growth direction of the diffracted peaks but increases the crystallites size. The lower Sb/Sn ratio (∼0.2) revealed a better homogeneity of SnO2 onto Silicon than the glass substrate. Indeed, the AFM images showed that Si gives a smoother Sb/SnO2 film. The electrochemical measurements were studied with the variation of Sb(%)/SnO2/Si. The Capacitance-Potential (C-2 – E) characteristics confirmed the n-type nature induced by the compensation mechanism Sb5+/Sn4+, the flat band potentials of −0.83 and −0.85 V for SnO2/Si and Sb(0.85 %)/SnO2/Si respectively were obtained and both values are cathodic enough to reduce Cr(VI). The variation of the impedance with the frequency and the effect of the substrate on the transport properties showed that the grain boundaries dominate the conduction mechanism, influenced by the microstructures of the films (crystallography and texture). Sb(%)/SnO2/Si/Cr(VI) solution provided variable electrochemical properties, and an appreciable difference in the light absorbance confirmed the chromate reduction (λmax = 350 nm, 16 ppm) to less hazardous form Cr3+; a conversion of 80 % was obtained under solar light.

Bulk and Surface Electrical Properties of BiSb on Flat and Ion‐Beam Nano‐Patterned InP Substrates

One route to the improvement of thermoelectric material performance is nanostructuring. Herein, BiSb thin films are grown by molecular‐beam epitaxy on two types of InP(001) substrate: flat epiready wafer, and nano‐patterned by ion bombardment and annealing (IBA). The effects of IBA on InP substrate are presented, and the structural and electrical properties of the BiSb films are measured. BiSb films on flat substrates are highly textured with (003) orientation, while films on IBA‐patterned substrates are less well ordered with mainly (012) orientation. A simple calculation method for nonplanar Hall measurements is proposed to explain the electrical conduction in rough films. The effects of BiSb film texture, roughness, and thickness on carrier density and mobility are provided. Sheet carrier density is independent of thickness at 77 K, which suggests conduction via surface states. Topological protection of such states may support nano‐patterning as a route to reducing thermal conductivity while maintaining electrical conductivity.

Preparation of MgO Self-Epitaxial Films for YBCO High-Temperature Coated Conductors.

Ion beam-assisted deposition (IBAD) has been proposed as a promising texturing technology that uses the film epitaxy method to obtain biaxial texture on a non-textured metal or compound substrate. Magnesium oxide (MgO) is the most well explored texturing material. In order to obtain the optimal biaxial texture, the actual thickness of the IBAD-MgO film must be controlled within 12nm. Due to the bombardment of ion beams, IBAD-MgO has large lattice deformation, poor texture, and many defects in the films. In this work, the solution deposition planarization (SDP) method was used to deposit oxide amorphous Y2O3 films on the surface of Hastelloy C276 tapes instead of the electrochemical polishing, sputtering-Al2O3 and sputtering-Y2O3 in the commercialized buffer layer. An additional homogeneous epitaxy MgO (epi-MgO) layer, which was used to improve the biaxial texture in the IBAD-MgO layer, was deposited on the IBAD-MgO layer by electron-beam evaporation. The effects of growth temperature, film thickness, deposition rate, and oxygen pressure on the texture and morphology of the epi-MgO film were systematically studied. The best full width at half maximum (FWHM) values were 2.2° for the out-of-plane texture and 4.8° for the in-plane texture for epi-MgO films, respectively. Subsequently, the LaMnO3 cap layer and YBa2Cu3O7-x (YBCO) functional layer were deposited on the epi-MgO layer to test the quality of the MgO layer. Finally, the critical current density of the YBCO films was 6 MA/cm2 (77 K, 500 nm, self-field), indicating that this research provides a high-quality MgO substrate for the YBCO layer.

Nanoscale thinning of metal-coated polypropylene films by Helium-ion irradiation

Polypropylene (PP) films have a wide range of applications, e.g. as dielectric materials for metallized film capacitors. In this article, we present a method for thickness reduction of PP films by ion irradiation, which has a direct effect on device capacitance. We show that the thickness of PP layers can be reduced by irradiation with He+ ions and controlled on the nanometer scale by the irradiation dose. The effect of different thin metal film coatings on PP surface was also investigated. The metal coatings were used for two reasons: they function as one of the metal electrodes in the capacitor structure, and they minimize sample charging during ion irradiation. Three different metallization materials were investigated: 5 nm Pt60Pd40, 5 nm Au, and 15 nm Al. We studied two technologically relevant PP films: the thinnest commercially available biaxially oriented polypropylene (BOPP) and spin-coated polypropylene (SC-PP) thin films. The irradiation was done with a focused Helium-ion beam (He-FIB) in a Zeiss Orion NanoFab Microscope at a landing energy of 30 keV with doses in a range of 5.4 × 10–5 nC/μm2 to 8.1 × 10–3 nC/μm2. An atomic force microscope (AFM) was used to analyze the details of surface modification: the surface height of the irradiated regions and surface morphology changes caused by the irradiation. For all applied doses, the Al-coated samples demonstrated smaller surface-height reduction compared to the Pt60Pd40 and Au-coated samples. We speculate that the possible factors responsible for this effect include differences in the thickness and the crystalline-grain orientation (texture) of the metallization films. Both BOPP and spin-coated PP presented surface ridges at the borders between the irradiated and non-irradiated regions. It can be attributed to the mechanical strain induced by the material modification.

Tribological properties of friction pairs under double composite surface configuration with diamond film and laser texture

A composite model, which combined diamond thin film with surface microstructure, was designed on the surface of silicon carbide by picosecond laser and hot filament chemical vapor deposition. And the multifunctional friction and wear tester was used to study the tribological performance of the friction pair (silicon carbide-graphite) under oil-poor conditions to examine the tribological performance of the friction pair in terms of surface temperature rise and time-varying wear. The results show that the friction coefficient under the composite modeling of surface microstructure and diamond film reaches 0.009, and at the same time, the surface temperature of the composite modeling is only 61.2 ℃, which is 5.1% lower than that of only diamond film and 62.1% lower than that of no surface treatment, which indicates that the high frictional heat has caused a significant graphitization transition in the film. And the surface of the friction sub-surface with the lowest temperature (surface microstructure and diamond thin film composite modeling) kept the carbon content at more than 90% without the formation of Si-C bonding, which guaranteed the complete carbon friction transfer film; At the same time, the ID/IG ratio of the friction surface under the composite modeling of the surface microstructure and diamond film is about 0.06 at the abrasion mark, the ID/IG ratio of the diamond film only is about 0.33, and the ID/IG ratio of the friction surface without any surface treatment is about 1.37. Transient high temperatures lead to abrasion and localized spalling on the surface of friction pairs, causing graphite oxidation to become progressively more severe, thus transforming abrasive wear into adhesive wear. As a result, double composite surface configuration with diamond film and laser texture further reduced the transient temperature rise of the surface and improved the tribological performance of the friction pairs.

Texture evolution of obliquely deposited Au thin films

Understanding the formation and evolution of the texture of obliquely deposited films is of great significance for improving their performance. Among these films, Au films have many advantages and wide application prospects. However, a systematic study of texture evolution of Au films has not been reported. In this study, Au films were prepared by magnetron sputtering oblique deposition. The pole figures of films deposited with various oblique angles (γ) and thicknesses were measured by X-ray diffraction. The morphology and size of the grains on the surface and in the cross-section of the films were observed by scanning electron microscopy. The surface topography of the films was determined by atomic force microscopy. During the growth process of the films, the increase rate of roughness was faster than the transverse broadening rate of grains. The samples deposited at γ ≤ 60° were composed of densely arranged grains with inclined (111) plane fiber texture whose tilt angle increased with the increase of γ and thickness. In the films deposited at γ ≥ 70°, the grain structure evolved into highly porous nanorods, and the (111) plane texture was more slanted and dispersed. The mechanism of film texture formation during oblique deposition is discussed.

Formula omitted] thin-films as efficient optical limiters: A study on impact of annealing

We present a detailed investigation on the impact of thermal annealing on the third-order nonlinear optical (NLO) properties of sputtered WSe2 thin films. The process of annealing results in an appreciable change in morphology and texture of WSe2 films that is governed by the annealing temperature and duration of annealing. These modifications are apparent from the electron micrographs as well as X-ray diffraction and Raman spectrum. The visible absorption spectroscopy point towards a gradual shrinkage of electronic bandgap which motivated us to explore the impact of NLO properties of the annealed WSe2 films. The NLO measurements were carried out using a single-beam Z-scan technique using ultrashort pulses centered at 1030 nm excitation wavelength. The investigations reveal a distinct two-photon absorption (TPA) signature for the annealed WSe2 films along with a self-focusing effect. The observations indicate the strengthening of optical limiting behavior exhibited by WSe2 films when they are annealed for a longer duration. The outcomes suggest that the process of annealing in WSe2 films allows controlling the NLO properties and renders them more suitable candidates as optical limiters for high-power applications.

Effect of deposition temperature on topography and electrochemical water oxidation of NiO thin films

The deposition temperature plays a significant role in controlling the crystallinity, morphology, and texture of thin films. Herein, we report the fabrication of nickel oxide thin films on a fluorine-doped tin oxide-coated glass substrate via a single-step aerosol-assisted chemical vapor deposition technique. Variable temperatures from 450 to 525 °C were used for the fabrication of these NiO thin films. The crystalline structure of nickel oxide thin films was determined by X-ray diffraction which showed cubic structure having space group Fm3m, and unit cell lattice parameters of a = b = c = 4.17 Å that crystallize preferentially along (200) plane. While the Raman spectroscopic study revealed the presence of peaks corresponding to nickel oxide structure. The surface chemical composition and oxidation states were investigated by X-ray photoelectron spectroscopy. Moreover, field-emission scanning electron microscopy aided in examining the temperature-dependent topography and microstructure of films. It was observed that when deposition temperature is increased from 450 to 525 °C, the bandgap energy decreased from 3.59 to 3.41 eV. The electrocatalytic activity for the oxygen evolution reaction was performed under alkaline conditions, using linear sweep voltammetry and cyclic voltammetry at different scan rates. Moreover, ohmic drop and charge transfer resistance are estimated by electrochemical impedance spectroscopy. The nickel oxide deposited at 500 °C showed the highest current density and the earliest onset overpotential as compared with other samples at different temperatures. Morphology-dependent catalytic activity is attributed to substrate temperature which significantly affects the growth of nickel oxide. Cyclic voltammetry reveals the Ni redox feature due to the active phase of nickel (oxy)hydroxide (NiOOH) and there was no significant current until 1.5 VRHE. Measurements of activity as a function of substrate temperature were consistent with the hypothesis that different morphology of the electrode exerts different charge transfer activation on nickel oxide. These results suggested that electrocatalysts coupled with controlled morphology can be tuned in terms of high performance, commercial applicability, and water-splitting devices.

Variable spin texture in Mn3Sn/Pt heterostructures revealed by magnetic circular dichroism

Non-collinear antiferromagnets with a D019 hexagonal structure have attracted tremendous attention for their potential applications in topological spintronics. Exploring the relationship between spin texture and electronic band structure is crucial for understanding the physical nature of these chiral antiferromagnets. Here, we systematically investigated the variation of topological spin texture of the non-collinear antiferromagnet Mn3Sn film using magnetic circular dichroism (MCD) spectroscopy. The evolution of Mn spin texture from coplanar inverted triangular structure to swirling spin texture was achieved in Mn3Sn/Pt heterostructures through introducing an interfacial Dzyaloshinskii–Moriya interaction (DMI) at room temperature. Correspondingly, unconventional zero-crossing points in energy-resolved MCD spectra as well as a gradual shift of a zero-crossing point to longer wavelength were observed. Our work provides a spin texture modulation approach via interfacial DMI and an effective non-contact magneto-optical detection method to reveal the spin texture in the non-collinear antiferromagnet/heavy metal system.

Mechanical and tribological properties related on the texture of TiN films regulated via HiPIMS

Since H/E represents elastic strain to failure and H3//E2 represents the resist to plastic deformation, both ratios assure the tribology properties. In this study, at very first time, hardness variation does not agree the Hall-Patch effect and wear rate of the TiN film shows the opposite change with hardness, i.e., tribological properties related to the texture of TiN films, beyond H/E or H3/E2. Base on the XRD and HRTEM results, we proposed a new decipher that texture dominate the hardness and wear properties, i.e., hardness, roughness, wear rate of the TiN film and wear volume of GCr15 ball to some extent that are increase with increasing of texture coefficient at (111) and decreasing of texture coefficient at (200). Further, the tribo-chemical reaction on the friction pair produces a graphite-like tribo-layer with anti-friction effect.

Structure and Properties of Thin Magnetron Films of Cadmium Arsenide on Various Substrates

Purpose of the study. Synthesis of cadmium arsenide magnetron films on various substrates and study of their structure, composition, optical and electrical properties.Methods. The deposition of thin films of cadmium arsenide was carried out by the method of non-reactive highfrequency magnetron sputtering in an argon atmosphere. The structure and composition of the films were studied using X-ray phase analysis, scanning electron microscopy, energy dispersive analysis, and small-angle X-ray diffractometry. Optical studies were performed using Raman spectroscopy. The results of a study of the electrical properties of thin films of cadmium arsenide are presented.Results. On silicon, sapphire, and strontium titanate substrates, thin films of the Dirac semimetal, cadmium arsenide, were obtained with a thickness of about 40 nm. A study of their structure and composition showed a significant effect of annealing in an argon atmosphere following deposition on the crystallinity of the film. After annealing, regardless of the crystal structure of the substrate, partial orientation of the film with the (112) texture axis. The films closest to the stoichiometric composition were obtained by deposition followed by annealing onto an oriented strontium titanate substrate, and to the crystal structure of cadmium arsenide single crystals of a film on a sapphire substrate. Annealing also leads to a smoothing of the film surface, a decrease in structural defects, and the transition of the fractal dimension of its topology to two-dimensional from close to three-dimensional immediately after deposition. The optical properties after annealing also change, which indicates their transition from a polycrystalline (amorphous) state to a single-crystal (textured).Conclusion. Experimental studies of the structure and properties performed by various methods made it possible to establish that single-crystal or textured cadmium arsenide films suitable for studying the manifestation of topological properties can be obtained by controlled annealing.

Biaxial texture establishment and evolution in IBAD-MgO films under different ion-to-atom ratios

MgO is a critical layer for the high-temperature superconducting coated conductor whose quality and performance greatly depend on the texturization of the MgO layer. In this paper, we have successfully grown MgO thin films on Y2O3 seed layers by the ion beam-assisted deposition (IBAD) method and systematically investigated the effects of ion-to-atom ratios (IARs) on the texture evolution of MgO films. It was found that better textured IBAD-MgO films could be obtained at thinner thickness with the increase of IAR. At low IARs of 0.2, 0.34, and 0.47, biaxial texture without c-axis tilting features could be observed in MgO films with thicknesses up to 50–60 nm, which is the highest value in our study. On the other hand, for high IARs of 0.66 and 0.79, the biaxial texture of MgO films was optimized at 13 nm and 7 nm, but completely disappeared at 26 nm and 12 nm, respectively. The differentiation in the texture evolution process under different IARs provides a crucial reference for elucidating the growth mechanism of IBAD-MgO. Moreover, these unambiguous experimental results also provide an excellent reference for the industrial production of HTS-coated conductors.

Improving the crystallinity and texture of oblique-angle-deposited AlN thin films using reactive synchronized HiPIMS

Many technologies, such as surface-acoustic-wave (SAW) resonators, sensors, and piezoelectric MEMS require highly-oriented and textured functional thin films. The best results are typically achieved for on-axis sputter geometries, but in some scenarios, this is not feasible, such as during co-deposition from multiple magnetrons or when coating substrates with high aspect ratios. Ionized physical vapor deposition (PVD) techniques such as HiPIMS can be used to accelerate the film-forming species onto the growing film using substrate-bias potentials, thus increasing adatom mobility and film texture. However, gas-ion incorporation can limit the feasibility of such synthesis approaches for defect-sensitive functional thin films. This work reports on the oblique-angle deposition of highly textured, c-axis oriented AlN (0002) films using reactive metal-ion synchronized HiPIMS. AlN thin films deposited using direct current magnetron sputtering (DCMS) and HiPIMS are discussed for comparison and the effect of ion irradiation through substrate biasing is investigated. We find that combining HiPIMS with a moderate substrate bias of only −30 V improves the crystalline quality and texture of the films significantly, while the process-gas incorporation and point defects formation can be further reduced by synchronizing the negative substrate bias potential to the Al-rich fraction of each HiPIMS pulse. In addition to a pronounced out-of-plane texture, the films show uniform polarization of the grains making this synthesis route suitable for piezoelectric applications. While the compressive stress in the films is still comparatively high, the results already demonstrate, that metal-ion synchronized HiPIMS can yield promising results for the synthesis of functional thin films under oblique-angle deposition conditions - even with low substrate-bias potentials.

Van der Waals epitaxy of pulsed laser deposited antimony thin films on lattice-matched and amorphous substrates

Monatomic antimony thin films have recently attracted attention for applications in phase change memory, nanophotonics, and two-dimensional materials. Although some promising results have been reported, the true potential of Sb thin films is still hindered by the scalability issue and the lack of reliable bottom-up production. Here we demonstrate the growth of Sb thin films on a lattice-matching and amorphous substrates using pulsed laser deposition. C-axis out-of-plane textured Sb thin films were successfully deposited on Sb2Te3 and SiO2/Si3N4 substrates. In the case of growth on Sb2Te3, we show that an intermediate phase is formed at the Sb2Te3–Sb interface playing a crucial role in forming a solid coupling and thus maintaining epitaxy leading to the production of high-quality Sb thin films. A 3–4 nm amorphous Sb seed layer was used to induce texture and suitable surface termination for the growth of Sb thin films on amorphous substrates. The deposition parameters were fine-tuned, and the growth was monitored in situ by reflection high energy electron diffraction. Scanning/transmission electron microscopy unveiled the local structure of produced films showing the formation of ꞵ-phase Sb thin films. Our results demonstrate the feasibility to produce very smooth high-quality antimony thin films with uniform coverage, from few layers to large thicknesses, using pulsed laser deposition. We believe the results of our work on scalable and controllable Sb growth have the potential to open up research on phase change materials and optoelectronics research.

Tuning the texture and polarity of ZnO thin films deposited by spatial atomic layer deposition through the addition of a volatile shape-directing agent

Many functional devices are nowadays based on thin films deposited by physical or chemical vapour deposition methods. Being able to control the texture of the films is very important to tune their functional properties. Texture is commonly tuned by either using single crystalline substrates or seed layers, or by modifying the deposition parameters (gas flows, precursor concentration, temperature, etc.). In this study a volatile shape-directing agent (VSDA), namely 4-(5)-Methylimidazole (4-(5)-MeIM), is used during the deposition of ZnO thin films by Atmospheric-Pressure Spatial Atomic Layer Deposition (AP-SALD) to control the texture and growth rate of the films. In particular, ZnO thin films can be grown preferentially along [001], resulting in an enhanced piezoelectric coefficient. In addition, the polarity of the ZnO films also depends on the amount of VSDA used. An innovative industry-compatible approach to control texture and polarity of ZnO thin films is presented, having a clear potential for other functional materials and applications.

Thickness dependence of magnetic and magnetotransport properties of textured Fe3O4 ferrimagnetic films on SiO2/n-Si(001)

The efficient injection of spin-polarized charge carriers from a ferro- or ferrimagnet into a semiconductor is an urgent problem. Half-metal magnetite (Fe3O4) is an attractive candidate for the role of a spin injector in spintronic devices. Here, the influence of the thickness of magnetite films on their electrical, magnetic, and magnetotransport properties is presented. Polycrystalline magnetite films with (311)-texture and thickness ranging from 15 to 250 nm are grown on the oxidized silicon surface by reactive iron deposition in the molecular oxygen atmosphere. The saturation magnetization is found to increase nonmonotonically with the film thickness and reaches its maximum value at 170 nm, which is close to that of a single crystal (∼480 emu/cm3). It is shown that for films with a thickness of more than 150 nm, there is a rapid decrease in resistivity by almost three times. The critical film thickness at which the coercive force decreases to the lowest value of ∼250 Oe is 100 nm. The magnetoresistance value reaches − 2.5 % already at a thickness of 50 nm and remains almost unchanged with a subsequent increase in the thickness of the textured film. Since, at a small thickness, textured films have higher magnitudes of conductivity and magnetization than conventional polycrystalline films, the textured-F3O4/SiO2/n-Si(001) junction with amorphous SiO2 barrier is promising for Si-based spintronic devices.

Influence of aluminum and iron chlorides on the parameters of zigzag patterns on films dried from BSA solutions

The relationships between the structural and aggregational state of bovine serum albumin (BSA) and the specific length and total number of zigzag pattern segments of the film textures formed upon drying biopolymer solutions with aluminum and iron chlorides have been shown. To obtain films, saline solutions of BSA were dried in a glass cuvette under thermostatically controlled conditions. It is shown that the formation of zigzag structures is sensitive to the influence of aluminum chlorides Al3+ and iron chlorides Fe3+ and depend on the concentration of AlCl3 and FeCl3. This may be due to a change in the charge and size of BSA particles and due to a change in conformation or a violation of the structure of BSA. These factors, in turn, affect the hydration of the solution components and the structural state of free water in solution, which presumably also affects the formation of zigzag structures. It is established that the analysis of the specific length and the number of segments of zigzag patterns makes it possible to evaluate changes in the state of biopolymers in the initial solution during structural changes and aggregation.

Annealing temperature dependent properties for Ni/Ti/W Ohmic contacts simultaneously formed on n- and p-type 4H-SiC

The paper investigated the annealing temperature dependence of electrical and structural properties for Ni (50 nm)/Ti (60 nm)/W (60 nm) Ohmic contacts simultaneously formed on n- and p-type 4H-SiC by in-depth electrical and physical characterization. With the annealing temperature rising in the range of 900 °C–1050 °C, the specific contact resistances (SCRs) of both n- and p-type Ohmic contacts monotonously decreased with a similar trend in the range of 1 × 10−4–1 × 10−6 Ω cm2, which was favorable for the simultaneous formation of n- and p-type Ohmic contacts with lower SCRs in the active region. For n-type Ohmic contacts, the variation of SCRs with annealing temperatures was correlated to the relative proportion of the total contact area occupied by the (220) plane compared to the other planes for the polycrystalline and textured δ-Ni2Si film at the contact interface characterized by x-ray diffraction. Furthermore, the surface morphology of Ohmic contacts under different annealing temperatures was highly similar with almost identical root mean square roughness of about 6.2 nm measured by atomic force microscopy (AFM), which was thought to be smooth enough for the wire bonding process from the perspective of device applications. The distinct W layer with no evidence of obvious intermixing and the great distance of released free carbon away from the contact surface makes the surface morphology smooth and uniform.

Methods for controlling the texture of thin films of wedge-shaped amphiphilic compounds based on 2,3,4-tris(dodecyloxy)benzenesulfonic acid

Methods for controlling the texture of thin films of wedge-shaped amphiphilic compounds based on 2,3,4-tris(dodecyloxy)benzenesulfonic acid

Topological transport properties of highly oriented Bi2Te3 thin film deposited by sputtering

Topological insulators (TIs) are the promising materials for next-generation technology due to their exotic features such as spin momentum locking, conducting surface states, etc. However, the high-quality growth of TIs by sputtering technique, which is one of the foremost industrial requirements, is extremely challenging. Also, the demonstration of simple investigation protocols to characterize topological properties of TIs using electron-transport methods is highly desirable. Here, we report the quantitative investigation of non-trivial parameters employing magnetotransport measurements on a prototypical highly textured Bi2Te3 TI thin film prepared by sputtering. Through the systematic analyses of the temperature and magnetic field dependent resistivity, all topological parameters associated with TIs, such as coherency factor , Berry phase (), mass term (m), the dephasing parameter (p), slope of temperature dependent conductivity correction () and the surface state penetration depth (λ) are estimated by using the modified ‘Hikami–Larkin–Nagaoka’, ‘Lu–Shen’ and ‘Altshuler–Aronov’ models. The obtained values of topological parameters are well comparable to those reported on molecular beam epitaxy grown TIs. The epitaxial growth of Bi2Te3 film using sputtering, and investigation of the non-trivial topological states from its electron-transport behavior are important for their fundamental understanding and technological applications.