Multilayer Thin Films Research Articles

Dye-sensitized solar cells achieved with multi-layered SnO2/ZnO composite photoanodes through precise control of thickness and composition

AbstractThe spin coating is cost-effective, straightforward, and highly suitable for the large-scale production of solar cells. In this study, we report the fabrication of SnO2/ZnO composite films for dye-sensitized solar cells (DSCs) using a simplified and cost-effective spin-coating technique on fluorine-doped tin oxide glass substrates. This study introduces a new way of preparing a multi-layered composite thin film using a suspension containing colloidal SnO2 nanoparticles and ZnO nanoparticles followed by sonication and aging of TiO2-free high-efficiency DSCs. Our approach provides a facile way of obtaining a uniform film of tunable thickness with high reproducibility by adjusting the total number of coating cycles. The spin-coating process achieved a nano-sized SnO2-covered ZnO layer, contributing to enhanced conversion efficiency in DSCs. A specific number of seven coating cycles was identified as optimal for achieving the aspirational performance. Under standard AM 1.5 irradiation with an intensity of 100 mW/ cm2, the fabricated SnO2/ZnO composite films revealed an overall energy conversion efficiency of 6.5% with a thickness of 2.06 µm which is impressive for a TiO2-free DSC. This achievement indicates the potential of the developed fabrication process for cost-effective and scalable production of efficient DSCs with SnO2/ZnO composite.

A two-dimensional thin film structure with spectral selective emission capability suitable for high-temperature environments

Spectral selective emission materials, characterized by their high emission efficiency within specific wavelength ranges, play a crucial role in various fields such as infrared stealth and radiative cooling. In this study, leveraging the tunneling effect of ultrathin metal layers and the impedance matching principle, we designed a one-dimensional multilayer thin film structure composed of Mo/Ge/Al. This design successfully achieved spectral selective emission within the 3-14 μm infrared spectrum range, showcasing superior high-temperature infrared stealth capabilities. Research findings indicate that the infrared atmospheric window (ε3-5 μm=0.40, ε8-14 μm=0.30) maintains a low emissivity within the temperature range from room temperature to 400°C, while high emissivity in non-infrared atmospheric windows (ε5-8 μm=0.81) enables radiative cooling. The use of high emissivity in the non-infrared atmospheric window reduced the surface temperature of this structure by 15.3°C compared to untreated Si substrate under similar heating conditions. The temperature reduction was 34.1°C when compared to a Si substrate coated with a 200 nm Al film. This straightforward and easily scalable structure not only presents novel solutions for applications in infrared stealth and radiative cooling but also holds vast potential for diverse fields including military, aerospace, and industrial manufacturing, injecting fresh impetus and possibilities into technological advancement.

Nested deep transfer learning for modeling of multilayer thin films

Nested deep transfer learning for modeling of multilayer thin films

Data-driven investigation of thickness variations in multilayer thin film coatings

Abstract Design and fabrication of multilayer thin film coatings for photonics applications require careful consideration of various parameters such as layer thickness, refractive indices and number of stacks. A growing trend uses machine learning for efficient navigation in the complex parameter space of photonics applications to efficiently extract valuable insights from the extensive datasets and to predict the optical performance. We developed an approach that combines Monte-Carlo and Finite-Difference Time-Domain simulations to model multilayer thin films. After conducting 95 200 runs, the data were analyzed using Neural Network fitting to explore how thickness variations influence the optical performance. An experiment validation on magnetron sputtered coated samples demonstrates the high accuracy of our method in predicting the optical performance of the thin film stacks (R 2 > 0.99), contributing to the understanding and enhancement of photonics stack properties for diverse optical applications using machine learning approaches.

Swift heavy ions induced transformations in the structural and magnetic properties of Co/Pt multilayer thin films for magnetic storage applications

The integration of CoPt nanoparticles into an insulating matrix has garnered significant attention in material science, nanotechnology, and electronic engineering, particularly for their potential use in magnetic storage media. Precise control over the size, shape, and ordering of these nanoparticles is crucial. This study investigates the impact of swift heavy ion irradiation (120 MeV Ag+9) with varying ion fluences (1 × 1013 and 3 × 1013 ions/cm2) on the structural and magnetic properties of sputter-deposited Co/Pt multilayer thin films on quartz substrates. X-ray diffraction (XRD) analysis of the pristine samples reveals the presence of an FCC-structured CoPt alloy. In contrast, films irradiated with a fluence of 1 × 1013 ions/cm2 exhibit superlattice peaks (001) and (110), indicative of L10-structured CoPt alloy, whereas films subjected to 3 × 1013 ions/cm2 retain the FCC structure. This suggests that a fluence of 1 × 1013 ions/cm2 promotes ordering, while 3 × 1013 ions/cm2 induces disordering. Selected area electron diffraction (SAED) patterns from TEM confirm these structural transitions, while SQUID magnetometry reveals an increase in coercivity at 1 × 1013 ions/cm2, followed by a reduction at 3 × 1013 ions/cm2, consistent with the observed structural changes. These results demonstrate that carefully controlled ion fluences can effectively tailor the structural and magnetic properties of Co/Pt multilayers, enhancing their suitability for advanced magnetic storage applications.

Compact multilayer selective absorbers based on amorphous carbon for solar-thermal conversion

In addressing the energy crisis and climate change, environmentally sustainable materials and structures with heightened absorption and enhanced photothermal conversion efficiency are urgently demanded. In this study, a series of ultrabroadband, omnidirectional, and near-perfect solar radiation absorbers based on amorphous carbon (a-C) were fabricated by magnetron sputtering. These absorbers, featuring 4, 6, and 8-layer compact multilayer thin film structures, exhibited measured absorption of 96.8 %, 96.5 %, and 96.6 % in the range of 300–2500 nm, respectively. The high absorption efficiency delves into the synergistic effects of intrinsic absorption of a-C and enhanced absorption through thin film interference. Through microstructure analysis, the reduced absorption compared to design originates from the optical thickness mismatch caused by the unstable growth rate of a-C. In addition, the absorbers show very slight variations in absorption within 40° and maintain a high absorption of more than 80 % in the incident angle of 60°. For samples with different air annealing temperatures from 100 to 250 °C, the microstructure, morphology, and optical properties were systematically investigated. The appearance of oxygen channels due to surface defects or voids leads to the oxidation reaction of the diffused Ti atoms at high temperature. Notably, the proposed absorber can be fabricated by a lithography-free method, paving a way for large-area application of a-C.

Variation of MEMS Thin Film Device Parameters under the Influence of Thermal Stresses.

With the advancement of semiconductor manufacturing technology, thin film structures were widely used in MEMS devices. These films played critical roles in providing support, reinforcement, and insulation in MEMS devices. However, due to their microscopic dimensions, the sensitivity of their parameters and performance to thermal stress increased significantly. In this study, a Pirani gauge sample with a multilayer thin film structure was designed and fabricated. Based on this sample, finite element modeling analysis and thermal stress experiments were conducted. The finite element modeling analysis employed a combination of steady-state and transient methods to simulate the deformation and stress distribution of the device at room temperature (25 °C), low temperature (-55 °C), and high temperature (125 °C). The thermal stress test involved placing the sample in a temperature cycling chamber for temperature cycling tests. After the tests, the resonant frequency and surface deformation of the device were measured to quantitatively evaluate the impact of thermal stress on the deformation and resonant frequency parameters of the device. After the experiments, it was found that the clamped-end beams made of Pt were a stress concentration area. Additionally, the repetitive thermal load caused the cantilever beam to move cyclically in the Z direction. This movement altered the deformation of the film and the resonant frequency. The suspended film exhibited concavity, and the overall trend of the resonant frequency was downward. Over time, this could even lead to the fracture of the clamped-end beams. The variation of mechanical parameters derived from finite element simulations and experiments provided an important reference value for device design improvement and played a crucial role in enhancing the reliability of thin film devices.

Multilayer thin film mid-infrared broadband absorber with high visible light transmittance

Few reports on absorbers achieve both high transmittance of visible light and strong absorption of mid-infrared light. Here a multilayered absorber with high visible light transmittance and strong broadband absorption in the mid-infrared band is proposed. The absorber is four-layer films of ITO/SiO2/ITO/SiO2 successively deposited on single-sided conductive glass by electron beam evaporation technology. The experiment shows that the integral transmittance in the 400–800 nm range is 82.8 %, and the integral absorption in the 3–5 μm band is 88.2 %.

Multi-layer heterojunction phase change thin films with extremely low resistance drift

This work prepared [GeSb9 (x nm)/Ga3Sb7 (16-x nm)]5 multi-layer phase change thin films and studied their related properties. Compared to traditional GST and GeSb9, [GeSb9 (6 nm)/Ga3Sb7 (10 nm)]5 multi-layer phase change thin films have a higher crystallization temperature (∼205 °C) and an extremely low resistance drift coefficient (0.0004). The crystalline behavior and bonding of thin films are analyzed to elucidate their intrinsic mechanisms, thermal stability, and interfacial effects. According to crystal mechanism analysis, the Avrami index (n) is 0.904, indicating that the [GeSb9(6 nm)/Ga3Sb7(10 nm)]5 multi-layer phase change thin films grow in one dimension. The presence of interfaces alters the crystallization behavior of crystals, leading to a growth mode that transitions from diffusion-controlled to interface-controlled and back to diffusion-controlled. This transformation significantly reduces the nucleation index (m ≤ 0.16), minimizing the inherent randomness of the film itself and achieving extremely low resistance drift. Research has demonstrated that [GeSb9 (6 nm)/Ga3Sb7 (10 nm)]5 multi-layer phase change materials have promising applications in embedded memory.

Understanding vapor phase growth of hexagonal boron nitride.

Hexagonal boron nitride (hBN), with its atomically flat structure, excellent chemical stability, and large band gap energy (∼6 eV), serves as an exemplary 2D insulator in electronics. Additionally, it offers exceptional attributes for the growth and encapsulation of semiconductor transition metal dichalcogenides (TMDCs). Current methodologies for producing hBN thin films primarily involve exfoliating multi-layer or bulk crystals and thin film growth via chemical vapor deposition (CVD), which entails the thermal decomposition and surface reaction of molecular precursors like ammonia boranes (NH3BH3) and borazine (B3N3H6). These molecular precursors contain pre-existing B-N bonds, thus promoting the nucleation of BN. However, the quality and phase purity of resulting BN films are greatly influenced by the film preparation and deposition process conditions that remain a substantial concern. This study aims to comprehensively investigate the impact of varied CVD systems, parameters, and precursor chemistry on the synthesis of high-quality, large scale hBN on both catalytic and non-catalytic substrates. The comparative analysis provided new insights into most effective approaches concerning both quality and scalability of vapor phase grown hBN films.

Multilayer Ge8Sb92/Ge2Sb2Te5 thin films: unveiling distinct resistance states and enhanced performance for phase change random access memory

This study investigates the phase-change properties of [Ge8Sb92 (25 nm)-Ge2Sb2Te5 (25 nm)]1 multilayer thin films, elucidating three distinct resistance states originating from two structural transitions: initial Sb precipitation and Ge2Sb2Te5-FCC crystallization, followed by Ge2Sb2Te5-FCC to Ge2Sb2Te5-HEX transformation with additional Sb precipitation. The phase transitions induce two abrupt changes in resistance at temperatures of 169.8 °C and 197.7 °C, respectively, with corresponding data retention temperatures of 97 °C and 129 °C, indicating robust thermal stability. The [Ge8Sb92 (25 nm)-Ge2Sb2Te5 (25 nm)]1-based phase change random access memory (PCRAM) device demonstrates reversible switching characteristics and multi-level storage capabilities within 20 ns, showcasing enhanced phase-change speed and storage density. In summary, [Ge8Sb92(25 nm)-Ge2Sb2Te5(25 nm)]1 demonstrates enhanced thermal stability, swift phase transition, and increased storage density relative to conventional Ge2Sb2Te5, establishing it as a promising new phase-change material for PCRAM applications.

Deposition Kinetics and Characteristics of Peald Igzo Films Using Tetrahydrofuran-Adducted in & Ga Precursors

As the down-scaling of semiconductor materials, silicon compatible emerging materials have extensively researched for next generation display and 3D structured devices. In particular, oxide semiconductors are considered a promising candidate for backplane applications in display. Among them, indium-gallium-zinc oxide (IGZO) using plasma enhanced atomic layer deposition (PEALD) has excellent properties, like high mobility, low leakage current, high transparecy and low temperature processablility. However, conventional precursors for IGZO still have some prolems to solve such as low deposition rate, low thermal stability and high price. In this study, we developed indium precursor (Trimethylindium Tetrahydrofuran, DIP-4) and gallium precursor (Trimethylgallium Tetrahydrofuran, DGP-2) to overcome the shortcomings of the conventional In & Ga precursors. ALD characteristics of the films deposited using the newly developed the precursors were confirmed through the source feeding time saturation and linearity. Furthermore, the incubation time of In, Ga and Zn oxide films according to the different bottom layer was respectively verified and calculated using the developed DIP-4, DGP-2 and commercially used DEZn. In order form a multilayer IGZO thin film, application of the incubation factors at IGZO process were experimentally demonstrated. Thickness of the IGZO films can be easily controlled through modulation of the incubation factors. The physical and chemical properties of the films were analyzed by X-ray diffraction, X-ray reflectrometer, X-ray photoelectron spectroscopy, transmission electron microscope. Figure 1

Influence of topography on nano-mechanical properties of cylindrical magnetron sputtered TiN films

Numerous studies on Nano-mechanical behavior of the thin films explained primarily in terms of their film morphology and particle size rather than film topography. Therefore, the current study investigates the effect of film topography on the nano-mechanical characteristics of the film. Ti/TiN multilayer thin films were deposited at varying deposition pressures by using an indigenously developed Cylindrical Magnetron Sputtering (CMS) unit. Surface crystallographic information is characterized by synchrotron-based Grazing Incidence XRD analysis. Film growth follows self-assembled nano hill architecture as revealed by AFM and in situ Scanning Probe Microscopy images. The tribo-mechanical properties of the film is dependent on the height and spacing of its self-assembled structure, which experiences either crushing or buckling under the indenter load, thereby affecting film characteristics. Film deposited at moderate pressure exhibits superior wear behavior, attributed to the interplay between Plasticity Index (PI) and Depth Recovery Ratio (DRR). The study primarily focused on film growth phenomena by using cylindrical targets and their influence on nanomechanical properties of the film.

Combining Lorentz TEM and SEM with Polarization Analysis to Uncover Fractional Topological Spin Textures in Fe/Gd Multilayer Thin Films

Combining Lorentz TEM and SEM with Polarization Analysis to Uncover Fractional Topological Spin Textures in Fe/Gd Multilayer Thin Films

Effect of interlayer thickness on electrochemical properties and corrosion resistance of sputtered TiNxnm/Tixnm multilayer thin films

Three multilayers [TiNxnm/Tixnm/p-type Si (100)] (x = 2.5, 5, 10) were fabricated using a dc-magnetron sputtering to evaluate surface and interfacial effect on electrochemical properties for possible application in supercapacitor electrode materials. The (111) and (101) planes of TiN and Ti were observed at 36.50° and 40.19° respectively. TA, LA, and TO phonon modes were found at 254.12, 306.15, and 637.94 cm−1, respectively. The defect state distribution of Ti, N, and O was investigated from PL. XPS confirmed the Ti at. % of TiNxnm/Tixnm multilayers decreased from 43.07 to 12.04 and N at. % increased from 42.79 to 72.53 % as the x value decreased from 10 nm to 2.5 nm. The areal specific capacitance (Ca) and energy density (E) of the TiNxnm/Tixnm multilayer electrode increased with decreasing multilayer thickness. E varied from 0.27 to 1.37 mWhcm−2 and the power density (P) from 5.04 to 25.4 mWcm−2 for the multilayers. The diffusion coefficient (D) and total accumulated charge (Qin) decreased from 6.48 × 10−17 to 1.56 × 10−18 cm2/s and 1.82 to 1.64 C/cm2, respectively, for TiNxnm/Tixnm multilayers. The capacitive contribution was the highest in x = 10 (2.181 Av−1s). However, the diffusion-limited contribution was maximum in x = 5 (3.541 Av−1/2s1/2). The cyclic stability maintained at 85.4 % capacitive retention over 1000 cycles and the expansive potential window (up to 0.8 V in 1 M H2SO4) makes the multilayer thin films ideal for supercapacitor electrodes. Among all the samples, the TiN2.5nm/Ti2.5nm exhibited the highest Ca, E, and diffusion coefficient, originating from the smaller layer thickness, leading to more ohmic conductivity and facilitating the supercapacitive performance.

Impact of carbon and platinum protective layers on EDS accuracy in FIB cross-sectional analysis of W/Hf/W thin-film multilayers

Achieving high-quality cross sections is essential for accurate analysis of multilayer coatings. One method of performing such cross sections is focused ion beam, where sample protection from ion damage in the form of protective layers applied by FEBID and FIBID methods is used. Due to the lack of comparative summaries of different layers applied by these methods, especially in the context of cross-sectional analysis and elemental analysis of the cross-section, it was decided to address the effect of the protective layer on the reliability of EDS analysis. This study compares the effectiveness of platinum and carbon protective layers in creating cross sections for W/Hf/W samples. The effect of protective layers on elemental mapping and elemental analysis accuracy was evaluated. This study highlights the importance of protective layer selection in providing reliable EDS analysis of cross sections.

Optimal design and preparation of high-performance multilayered thin film daytime radiative coolers

Optimal design and preparation of high-performance multilayered thin film daytime radiative coolers

SURFACE PLASMON RESONANCE ANALYSIS FOR BENZENE SENSING MEDIA USING SILVER AND Ta2O5 THIN FILMS

The increasing demand for optical sensors is driven by their wide applications, making surface plasmon resonance (SPR) play a crucial role in this field. In this study, a multilayered thin film consisting of tantalum pentoxide (Ta2O5) and silver (Ag) deposited on a glass prism was used to study SPR. The Ag layer thickness was fixed at 50 nm, while the Ta2O5 layer thickness varied from 0 to 70 nm. The Kretschmann configuration was employed to assess the sensitivity of air and gases with different refractive indices. Therefore, different layer thicknesses along with different wavelengths and angles were investigated. MATLAB software was employed to simulate and analyze SPR with a half-sphere prism to extend the incident angle. The simulation conditions with Fresnel equations were used to calculate the reflectivity and transmittance coefficients for the studied sample. The results revealed that the best output was at a Ta2O5 thickness of 50 nm to get optimal full width at half maximum of 2.4 and sensitivity factor of 162.5. This device works in the visible and infrared regions.

Synthesis, microstructure and micro-mechanical characterization of metal (Nb, Ti) – MAX phase (Ti2AlC) nanolaminates

We utilize elevated temperature physical vapor deposition (PVD) techniques to design metal/MAX multilayered nanocomposite thin films with alternating nanoscale metallic (Nb, Ti) and MAX phase (Ti2AlC) layer thicknesses. These metal/MAX nanolaminate architectures attempt to exploit a unique hierarchical topology – as interfaces between the layers are expected to be in direct competition with the internal interfaces within the MAX layers, to drive their tunable macroscopic mechanical behavior. Two metal/MAX nanolaminates – Nb/Ti2AlC and Ti/Ti2AlC – were deposited. The Nb/Ti2AlC metal/MAX system showed highly diffused layer interfaces with distinct Ti – rich and Nb–Al – rich layers, with the presence of MAX phase alongside TiC and other Ti–Al and Nb–Al intermetallic phases. The Nb/Ti2AlC system possessed a layered architecture, though the MAX phases were not found to be continuously present in each alternating layer. The second Ti/Ti2AlC system showed a non-lamellar nanocomposite microstructure and the formation of mixed Tin+1AlCn phases (a mix of n = 1, 2), and no indication of layering. Diffusion occurring between the metal/MAX layers in both cases, likely due to the elevated temperatures during the deposition process, is speculated as the likely cause of these resultant microstructures. The mechanical properties of both systems were evaluated using micromechanical (nanoindentation and micro-pillar compression) techniques, which demonstrated high strengths for both systems (Nb system: yield and instability strengths of 4.88 ± 0.1 GPa and 5.57 ± 0.03 GPa, Ti system: yield and instability strength of 5.61 ± 0.28 GPa and 6.21 ± 0.25 GPa). This work highlights the promising mechanical properties of metal/MAX multilayered depositions and summarizes the challenges in PVD synthesis of metal/MAX multilayered nanolaminates.

Layer‐Engineered Functional Multilayer Thin‐Film Structures and Interfaces through Atomic and Molecular Layer Deposition

AbstractAtomic layer deposition (ALD) technology is one of the cornerstones of the modern microelectronics industry, where it is exploited in the fabrication of high‐quality inorganic thin films with excellent precision for film thickness and conformality. Molecular layer deposition (MLD) is a counterpart of ALD for purely organic thin films. Both ALD and MLD rely on self‐limiting gas‐surface reactions of vaporized and sequentially pulsed precursors and are thus modular, meaning that different precursor pulsing cycles can be combined in an arbitrary manner for the growth of elaborated superstructures. This allows the fusion of different building blocks — either inorganic or organic — even with contradicting properties into a single thin‐film material, to realize unforeseen material functions which can ultimately lead to novel application areas. Most importantly, many of these precisely layer‐engineered materials with attractive interfacial properties are inaccessible to other synthesis/fabrication routes. In this review, the intention is to present the current state of research in the field by i) summarizing the ALD and MLD processes so far developed for the multilayer thin films, ii) highlighting the most intriguing material properties and potential application areas of these unique layer‐engineered materials, and iii) outlining the future perspectives for this approach.