Search Results (181)

The paper presents the results of a study on the structure and electrical properties of graphite-like amorphous carbon films deposited by electron-beam evaporation with vacuum heat treatment. The current–voltage characteristics of the films were analyzed in weak and strong electric fields in the temperature range from 25 to 155 °C. For the contact of carbon films with nickel, the Schottky barrier height was calculated based on the obtained current–voltage characteristics. It was found that in the temperature range of 25–45 °C, the mechanism of direct tunneling of charge carriers through the narrow Schottky barrier dominates (φ_b = 0.055 eV). In the range of 55–75 °C, a transition to the thermally assisted tunneling mechanism is observed (φ_b = 0.076 eV). At temperatures above 85 °C, charge carrier transport through the Schottky barrier occurs via thermionic emission (φ_b = 0.3 eV). The analysis of the current–voltage characteristics of graphite-like carbon films allowed us to establish the main mechanisms of hopping conductivity via localized states. It is shown that in the temperature range of 298–348 K, conductivity is determined by states near the Fermi level. The temperature interval of 348–428 K corresponds to conductivity through the band tail of localized states near the conduction band. It is shown that the increase in conductivity in strong electric fields is due to the Poole–Frenkel effect. Full article

The crystal structure regulation of Ti₃O₅ by Al₂O₃ doping and its effect on the optical properties of TiO₂ films prepared by electron beam evaporation were systematically studied. Ti₃O₅ coating materials with different Al₂O₃ doping contents (0–50 at%) were prepared by vacuum melting, and the corresponding TiO₂ films were deposited on K9 glass substrates via electron beam vacuum evaporation. The phase structure, phase transition temperature, chemical composition and optical properties of the materials and films were characterized by XRD, DSC, EDS, XPS, UV-Vis and AFM. Results show that Al₂O₃ doping induces the phase transition of Ti₃O₅ from a room-temperature stable β-phase to a high-temperature stable λ-phase, with complete transition at 5 at% doping. Al³⁺ with a smaller ionic radius causes lattice contraction and local distortion of Ti₃O₅, enabling stabilization at room temperature of the λ-phase. For TiO₂ films, 12.5 at% doping is the optimal state with the stable composition transfer under this condition. With the increase in Al₂O₃ doping content, the refractive index and extinction coefficient of TiO₂ films decrease continuously, while the optical band gap and surface roughness show an increasing trend. The changes in optical properties are mainly ascribed to the low refractive index of Al₂O₃, lattice compressive strain effect and oxygen vacancy passivation induced by Al³⁺. This study clarifies the regulation effect of Al₂O₃ doping on Ti₃O₅ phase transition and TiO₂ film optical properties, and provides theoretical basis and experimental reference for the doping modification of TiO₂ films and their practical applications in consumer electronics and optical filter devices. Full article

This study aims to reduce the phase transition temperature (PTT) of W-doped vanadium dioxide (VO₂) multilayer thin films. We designed and fabricated two asymmetric multilayer thin film structures; namely, TiO₂/VO₂-5%W/ITO and ITO/VO₂-5%W/TiO₂. The W-doped VO₂-based Trilayer thin films were deposited using an electron beam evaporation combined with the ion-assisted deposition (IAD) technique. An experimental study was conducted on the temperature-dependent residual stress and optical properties of the two asymmetric VO₂-based three-layer structures. The VO₂-based thin films were characterized using UV–Vis–NIR spectrophotometry, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and an improved Twyman–Green interferometer combined with fast Fourier transform (FFT) analysis for residual stress measurement. The trilayer structures incorporated a ~60 nm thick W-doped VO₂ middle layer, which plays a critical role in modulating thermochromic behavior and residual stress evolution. The results show that both trilayer thin films demonstrated excellent optical performance in transmission spectra. Raman spectral analysis revealed a blue shift in the characteristic W-doped VO₂ peaks, accompanied by a decrease in peak intensity as the temperature increased. Heating experiments on asymmetric W-doped VO₂ trilayer thin films revealed that the critical transition temperature of the ITO/VO₂-5%W/TiO₂/B270 trilayer film structure was significantly reduced to 45 °C. This demonstrates the effectiveness of our proposed multilayer film design in improving the PTT of W-doped VO₂ thin films. Analysis of the changes in residual stress of the trilayer thin films during heating experiments revealed that the residual stress shifted from compressive to tensile in the temperature range of 40 °C to 50 °C. The thermal expansion coefficient and biaxial modulus of the TiO₂/VO₂-5%W/ITO trilayer film structure were 5.37 × 10⁻⁶ °C⁻¹ and 295.7 GPa, respectively. In addition, the thermal expansion coefficient and biaxial modulus of the ITO/VO₂-5%W/TiO₂ trilayer film structure were 6.65 × 10⁻⁶ °C⁻¹ and 745.0 GPa. Full article

Sub-15 nm line structures are key building blocks for advanced device prototyping, nanoscale electrodes, and lithography templates such as etch/deposition masks. Although ultrahigh-voltage (≥100 kV) electron-beam lithography (EBL) can more readily achieve extremely small critical dimensions, its tool and infrastructure requirements limit widespread adoption in many laboratories. In contrast, 30 kV field-emission SEM platforms are far more accessible; however, resolution-limit patterning at 30 kV is more sensitive to beam current, exposure dose, and development conditions, motivating the establishment of a reproducible process flow and a well-defined process window. Here, we investigate the resolution limit of isolated lines using a Zeiss Gemini 460 system operated at 30 kV and an in-house pattern generator with 950 k PMMA C2 resist. To demonstrate device-level applicability, we develop a stable lift-off process, and all critical dimensions are evaluated on metal lines after e-beam evaporation and lift-off. By screening beam current and scanning dose to build the dose-to-size relationship, we show that reducing beam current significantly improves the achievable minimum line width. Under 35 pA, using CD ≤ 15 nm as the criterion for sub-15 nm window extraction, the usable dose range is [700, 804.3] µC/cm², corresponding to a dose latitude of ~14.9%. The best performance is obtained at 700 µC/cm², yielding a transferred metal line width of 13.85 nm after lift-off. This work provides a practical resolution-limit process flow and a quantitative process window for performing sub-15 nm patterning on accessible 30 kV platforms, supported by product-level lift-off validation. Full article

Biocompatible thin films are essential for advancing biomedical devices, as they enhance integration with biological tissues, improve device longevity, and reduce complications. The rapid evolution of both medical needs and materials science has led to a diverse array of deposition techniques, each offering unique advantages and challenges for tailoring surface properties without compromising the bulk characteristics of implants and sensors. While laser-based methods—such as pulsed laser deposition (PLD) and Matrix-Assisted Pulsed Laser Evaporation (MAPLE)—are renowned for their precision, ability to preserve complex material stoichiometry, and suitability for low-temperature processing, the broader landscape includes several other important approaches. Physical Vapor Deposition (PVD) techniques, including magnetron sputtering and pulsed electron deposition, are widely used for their ability to create uniform, adherent coatings with controlled thickness and composition, making them suitable for both hard and soft biomedical substrates. Chemical Vapor Deposition (CVD) and its plasma-enhanced variant (PECVD) offer conformal coatings and excellent control over film chemistry, which is particularly valuable for functional polymer and ceramic films. Other methods, such as sol–gel processing, ion beam deposition, and electrophoretic deposition, provide additional flexibility in terms of coating composition, adhesion, and processing temperature, allowing for the fabrication of films with tailored mechanical, chemical, and biological properties. Despite these advances, the field faces ongoing challenges in optimizing film properties for specific clinical applications, ensuring reproducibility, and scaling up production for widespread use. The necessity of this review lies in its comprehensive comparison of laser-based techniques with alternative deposition methods, providing critical insights into their respective strengths, limitations, and suitability for different biomedical scenarios. By synthesizing recent developments and highlighting current gaps, this review aims to guide researchers and clinicians in selecting the most appropriate thin-film deposition strategies to meet the evolving demands of next-generation biomedical devices. Full article

This study investigates the fabrication and characterization of binary Ti-Si and Ti-Al thin-film metallic glasses (TFMGs) deposited via electron beam evaporation on cp Ti and Si substrates. X-ray diffraction confirmed the amorphous structure of the Ti₈₉Si₁₁ and Ti₅₅Al₄₅ thin films. AFM revealed differences in surface roughness, with Ti₈₉Si₁₁ exhibiting a smoother surface (Ra = 0.9 nm) than Ti₅₅Al₄₅ (Ra = 1.6 nm), likely due to differences in atomic size mismatch, heat of mixing, and potential oxidation effects. Electrochemical tests in Hank’s solution demonstrated the superior corrosion resistance of Ti₈₉Si₁₁, which had the lowest i_corr (0.123 µA/cm²) and widest passive region compared to Ti₅₅Al₄₅ and reference materials (cp Ti and SS316L). Mechanical properties revealed that both TFMGs exhibit higher indentation hardness and comparable reduced elastic modulus to cp Ti, with Ti₅₅Al₄₅ showing the highest hardness (5.93 ± 0.37 GPa). These findings highlight the potential of Ti-Si and Ti-Al TFMGs as high-performance materials for biomedical coatings. Full article

Femtosecond laser processing has emerged as a promising post-deposition method for tailoring the properties of dielectric thin films, offering localized modification without thermal damage. This study investigates the effect of sub-ablative femtosecond laser irradiation on the nonlinear optical response of a TiO₂ single-layer coating deposited on soda-lime glass by electron-beam evaporation. The coating was modified using 35 fs pulses at 800 nm delivered at a repetition rate of 1 kHz and a fluence of 0.083 J/cm² while varying the number of pulses per spot. The effective nonlinear refractive index (n_2,eff) and effective nonlinear absorption coefficient (β_eff) were measured using the z-scan technique with femtosecond excitation. The as-deposited TiO₂ coating exhibited a negative effective nonlinear refractive index, signifying a self-defocusing nonlinear response, while femtosecond laser irradiation leads to pronounced changes in the effective nonlinear parameters. An increase in the magnitude of both effective nonlinear coefficients and a reversal of the sign of the effective nonlinear refractive index are experimentally observed after irradiation with higher pulse numbers. These findings provide experimental evidence that sub-ablative femtosecond laser processing can be used as a post-deposition tool to control the nonlinear optical response of TiO₂ thin films. Full article

In addressing the key technical challenges of achieving ultra-broadband and high film-thickness uniformity for meter-class large-aperture space telescopes, this study utilized a self-developed 4 m-class large-aperture thin-film deposition system. By employing plasma-assisted electron-beam evaporation technology and a co-evaporation method with inner and outer dual-ring multi-evaporation sources, precise control of film-thickness uniformity within a 2 m range was achieved. A composite film structure combining a metal reflective layer and an ultraviolet-enhanced dielectric layer was adopted to realize high reflectivity across an ultra-broad spectrum from ultraviolet to long-wave infrared. Experimental results show that the average reflectance of the composite film reaches 91.52% in the 0.25~0.38 μm spectral band and 99.40% in the 0.38~12 μm spectral band. The thickness uniformity of ZrO₂ and MgF₂ films within the 2 m aperture area was controlled at 1.37% and 3.12%, respectively, meeting the requirements for high uniformity in large-aperture space applications. Radiation testing confirmed that the change in film reflectance is less than 1% under a total irradiation dose of 3.66 × 10⁸ rad(Si), satisfying the demands for operation in harsh space environments. This research provides an innovative solution for thin-film technology in large-aperture, ultra-broad-spectrum space optical systems and holds significant value for engineering applications. Full article

In high-precision optical systems such as laser optics, astronomical observation, and semiconductor lithography, anti-reflection coatings are crucial for light transmittance, imaging quality, and stability, but traditional designs face modeling challenges in balancing ultralow reflectivity, high wavefront quality, and manufacturability amid multi-dimensional parameter coupling and multi-objective constraints. This study addresses these by proposing a unified mathematical modeling framework integrating a Symmetric five-layer high-low refractive index alternating structure (V-H-V-H-V) with dual-scale nanostructures, employing a constrained quasi-Newton optimization algorithm (L-BFGS-B) to minimize reflectivity, wavefront root-mean-square (RMS) error, and surface roughness root-mean-square (RMS) in a six-dimensional parameter space. The Sellmeier equation is adopted to calculate wavelength-dependent material refractive indices, the model uses the transfer matrix method for the Symmetric five-layer high-low refractive index alternating structure’s reflectivity, incorporates nano-surface height function gradient correction, sub-wavelength modulation, and radial optimization, applies Zernike polynomials for low-order aberration correction, quantifies surface roughness via curvature proxies, and optimizes via a weighted objective function prioritizing low reflectivity. Numerical results show the spatial average reflectivity at 632.8 nm reduced to 0.13%, the weighted average reflectivity across five representative wavelengths in the 550–720 nm range to 0.037%, the reflectivity uniformity to 10.7%, the post-correction wavefront RMS to 11.6 milliwavelengths, and the surface height standard deviation to 7.7 nm. This framework enhances design accuracy and efficiency, suits UV nanoimprinting and electron beam evaporation, and offers significant value for high-power lasers, lithography, and space-borne radars. Full article

This work reports an enhanced flexible vacuum-ultraviolet (VUV) photodetector on a polyimide (PI) substrate based on hexagonal boron nitride nanosheets (BNNSs) with Al nanoparticles (Al NPs). The BNNS film were prepared via liquid-phase exfoliation combined with a self-assembly process, and size-controllable Al NPs were constructed on the BNNS’s surface by electron-beam evaporation followed by thermal annealing. When the Al film thickness was 15 nm, the annealed Al NPs exhibited a pronounced enhancement of photoelectric effects at a wavelength of 185 nm. Combined with finite-difference time-domain (FDTD) simulations, it was confirmed that the localized surface plasmon resonance (LSPR) generated by Al NPs significantly enhanced the local electromagnetic field and effectively coupled into the interior of BNNSs. These exhibited a strong plasmon-enhanced absorption effect and thereby improved light absorption and carrier generation efficiency. The flexible photodetector based on this structure showed an increase in the photo-to-dark current ratio from 110.17 to 527.79 under a bias voltage of 20 V, while maintaining fast response and recovery times of 79.79 ms and 82.38 ms, respectively. In addition, the device demonstrated good stability under multiple bending angles and cyclic bending conditions, highlighting its potential applications in flexible solar-blind VUV photo ultraviolet. Full article

Tantalum pentoxide (Ta₂O₅) films deposited on fused silica substrates are critical components of high-power laser systems. Ion-assisted electron beam evaporation (IAD-EBE) is the mainstream technique for fabricating Ta₂O₅ films. However, it commonly requires extensive experimental efforts for deposition quality optimization, while each coating cycle is extremely time-consuming. To solve this issue, this work establishes a dataset targeting the surface roughness (Rq) and refractive index (n) of Ta₂O₅ films using atomic force microscopy, as well as ellipsometer and deposition experiments. Influence of assisting ion source beam voltage (V)/current (I) and Ar (Q₁)/O₂ (Q₂) flow rate on the n and Rq of Ta₂O₅ films are analyzed. Combining energy-field mechanism analysis with a Bayesian optimization approach (PI-BO), both deposition quality prediction and feature analysis of process parameters are achieved. The determination coefficient/mean absolute error for the prediction models of n and Rq reach 0.927/0.013 nm and 0.821/0.049 nm, respectively. Based on sensitivity analysis, the weight factors of V, I, Q₁, and Q₂ affecting n/Rq of Ta₂O₅ films are determined to be 0.616/0.274, 0.199/0.144, 0.113/0.582, and 0.072/0.000. V and Q₂ are identified as the core factors for regulating deposition quality. The optimal ranges for V and Q₂ are 600~700 V and 70~80 sccm, respectively. This study proposes a PI-BO method for predicting Rq and n of Ta₂O₅ films under small-data conditions, while determining the preferred parameter ranges and their sensitivity weight factors. These findings provide effective theoretical support and technical guidance for IAD-EBE strategy design and optimization of optical films in high-power laser systems. Full article

This paper analyzes microstructural layout and electrical behavior of silicon nanowire-based Schottky diodes, for use as wide-domain temperature sensors. The employed nanostructured three-dimensional substrates provide larger contact areas and enable higher Schottky barrier heights, ultimately leading to a better operable temperature range. Two metal deposition techniques (Radio Frequency sputtering and Electron-beam evaporation) are used to fabricate experimental Schottky diode samples. Scanning electron microscopy, X-ray diffraction, and diffuse reflectance investigations are carried out in order to determine nanowire distribution and the influence of subsequent metal deposition. The analyses evince the formation of a slightly inhomogeneous contact. The findings are validated by a thorough electrical characterization over a wide temperature domain. Inhomogeneity models are used in order to determine the main device parameters and the bias regions where they can be used as precise temperature sensors. The sputtered sample exhibits the best sensitivity, between 1 and 1.4 mV/K, while excellent linearity (R² > 99.5%) is obtained for Electron-beam evaporated devices. Both types of silicon nanowire-based Schottky diode sensors have 100–500K operable ranges, much larger than planar counterparts. Full article

In this study, nanocrystalline dysprosium oxide (Dy₂O₃) thin films were deposited on sapphire and quartz glass substrates by an electron beam evaporation technique to comparatively evaluate the influence of substrate type on their structural and optical properties. X-ray diffraction (XRD) confirms that all films exhibit a polycrystalline nature and possess a cubic-type structure. The Debye–Scherrer equation was used to determine the average crystallite size and it was found that the film deposited on quartz glass substrate is slightly larger than the film deposited on the sapphire substrate. Scanning electron microscopy (SEM) revealed a granular morphology for the sapphire film and a more compact, pore-free surface for the quartz film. Spectroscopic ellipsometry (SE) and UV-Vis spectrophotometry were employed to extract the optical constants and reflectance behavior, respectively. The film on sapphire exhibited a lower refractive index, higher extinction coefficient, and reduced reflectance, confirming its enhanced anti-reflective performance. The study provides new insights into how the substrate affects the optical properties of Dy₂O₃ thin films. This study demonstrates that sapphire is a more suitable substrate for enhanced anti-reflective and optoelectronic applications. Full article

Thin films of nickel oxide (NiO) were deposited on a 5° miscut magnesium oxide (MgO)(100) substrate using electron-beam evaporation to pursue morphology-directed resistive switching. The atomic force microscope (AFM) confirmed a stepped surface with a terrace width of ~85 nm and a step height of ~7 nm. After deposition, the film resistance decreased from 200 MΩ to 25 MΩ by annealing under ambient air at 400 °C, attributed to the increase in the p-type conductivity through nickel vacancy formation. Top electrodes of Ag (500 nm width, 180 nm gap) were patterned parallel or perpendicular to the substrate steps using UV and electron-beam lithography. Devices aligned parallel to the step showed reproducible unipolar switching with 100% yield between forming voltages 20–70 V and HRS/LRS~10² at ±5 V. In contrast, devices formed perpendicular to the steps (8/8) subsequently failed catastrophically during electroforming, with scanning electron microscopy (SEM) showing breakdown holes on the order of ~100 nm at the step crossings. The anisotropic electrodynamic response is due to step-guided electric field distribution and directional nickel vacancy migration, illustrating how substrate morphology can deterministically influence filament nucleation. These results highlighted stepped MgO as a template to engineer the anisotropic charge transport of NiO, exhibiting a reliable ReRAM as well as directional electrocatalysis for energy applications. Full article

In this study, high-conductivity W-doped Ga₂O₃ thin films were successfully fabricated by directly depositing a composition of Ga₂O₃ with 10.7 at% WO₃ (W:Ga = 12:100) using electron beam evaporation. The resulting thin films were found to be amorphous. Due to the ohmic contact behavior observed between the W-doped Ga₂O₃ film and platinum (Pt), Pt was used as the contact electrode. Current-voltage (J-V) measurements of the W-doped Ga₂O₃ thin films demonstrated that the samples exhibited significant current density even without any post-deposition annealing treatment. To further validate the excellent charge transport characteristics, Hall effect measurements were conducted. Compared to undoped Ga₂O₃ thin films, which showed non-conductive characteristics, the W-doped thin films showed an increased carrier concentration and enhanced electron mobility, along with a substantial decrease in resistivity. The measured Hall coefficient of the W-doped Ga₂O₃ thin films was negative, indicating that these thin films were n-type semiconductors. Energy-Dispersive X-ray Spectroscopy was employed to verify the elemental ratios of Ga, O, and W in the W-doped Ga₂O₃ thin films, while X-ray photoelectron spectroscopy analysis further confirmed these ratios and demonstrated their variation with the depth of the deposited thin films. Furthermore, the W-doped Ga₂O₃ thin films were deposited onto both p-type and heavily doped p⁺-type silicon (Si) substrates to fabricate heterojunction diodes. All resulting devices exhibited good rectifying behavior, highlighting the promising potential of W-doped Ga₂O₃ thin films for use in rectifying electronic components. Full article