Electron Beam Evaporation Method Research Articles

Experimental and Simulation Studies of Acetone Detection By Pt-Au Nanofilm Sensors

Introduction Acetone in exhaled breath is a biomarker of diabetes. However, since it is a very stable substance, its detection by chemical sensors has been a challenging task. Alloy nanoparticles have attracted great attention because of their great catalytic performance, and it has been reported that the response to acetone can be improved by functionalizing oxide semiconductors (In2O3) with PtAu nanoparticles [1]. However, the mechanism of better response to acetone has not been fully understood, which is partly because the effects of alloying and supporting materials cannot be separated in the composite material systems. In this study, we demonstrate that PtAu-alloy nanofilms, where the effect of supporting materials is eliminated, show a greater response to acetone than Pt nanofilms. Furthermore, the impact of alloying on sensing performance was studied by high-throughput atomistic simulation with neural network potentials. Method First, we fabricated Pt and PtAu nanofilm sensors. As the Pt and PtAu nanofilms, Pt and Pt/Au were deposited, respectively, by electron beam evaporation method. The thickness of Pt film is 3 nm, whereas Pt/Au thicknesses are 2.5 nm/0.5 nm. The electrodes consisted of 40-nm Pt and 40-nm Au layers, and they were annealed in N2 ambient for 1 hour at 300 oC. XRD measurements were performed to evaluate the alloy states for three samples: Pt (20nm), Au (20 nm), and PtAu (18 nm). The PtAu film for XRD was fabricated by repeating sequential depositions of 5-nm Pt and 1-nm Au three times. All the films were annealed for 1 hour at 300 oC in N2 ambient. The sensor responses to acetone were evaluated by measuring the resistance of Pt and PtAu at 260 oC under the following sequences.i) Dry air (15 min)ii) 1-ppm acetone in dry air (2 min)iii) Dry air (3 min)We applied DC current of 100 µA and the voltage difference between the terminals were measured. To examine the factors that contribute to the difference in sensing performance of PtAu and Pt nanofilms, we calculated the reaction pathway using the nudged elastic band method. All calculations were carried out with PFP version 2.0.0 on Matlantis [2]. DFT-D3 was used to describe the van der Waals interaction [3]. Results Pt, Au, and PtAu samples showed (111) peaks in the XRD analysis. The position of (111) peak of PtAu located between those of Pt and Au peaks, suggesting that PtAu was successfully alloyed. By applying the Vegard’s law, the composition of PtAu was determined to be 0.823:0.177, which is consistent with the thickness ratio. When acetone was exposed, the resistance of the devices decreased. The response of PtAu to acetone was greater than that of Pt. In addition, the responses of Pt and PtAu devices were proportional to the square root of the concentration of acetone. The limit of detections (LOD) determined by 3σ method were 76 ppb for Pt and 14 ppb for PtAu. Discussion We considered that H atoms introduced by CH dissociation of acetone prevent the adsorption of oxygens from the atmosphere and reduce the surface scattering of electrons, leading to a decrease in the resistance of Pt nanofilms. The Nudged Elastic Band method was used to calculate the activation energy of CH dissociation of acetone on the surface of Pt and PtAu. PtAu slab was prepared by replacing Pt atoms partly with Au atoms. The calculations showed that the activation energy for PtAu was 64-meV lower than that of Pt. In the transition state, the dissociated H atom stayed at the bridge site of Pt. When Pt atoms are substituted with Au atoms, the distance between Pt’s at the bridge site expands due to the large lattice constant of Au. As a result, the transition state became more stable on PtAu surface than on Pt surface. In fact, we confirmed that the activation energy was lowered as the Pt-Pt distance increased. Conclusion We demonstrated, for the first time, that PtAu nanofilm sensors show a greater response to acetone than Pt nanofilm. The atomic simulation demonstrated that the dehydrogenation of methyl group of acetone is the fundamental mechanism of the acetone sensing, and that the lattice expansion induced by replacing Pt with Au contributed to stabilize the transition state and to reduce the activation energy. Further optimization of the alloy composition should be essential to achieve a more highly sensitive acetone sensor.

ALUMINUM OXIDE IN VACUUM CONDENSATES BASED ON COPPER

Strengthening of copper and copper alloys with aluminum oxide particles is an important technological technique. Composite materials based on copper strengthened with aluminum oxide particles have a significant operating temperature range and better mechanical properties at elevated temperatures than age-hardening alloys. However, at moderate operating temperatures, the use of age-hardening alloys remains more economically justified. The main direction in the development of composites strengthened with oxide particles is the dispersion of the strengthening phase to sizes of several or one nanometer, which will bring their mechanical properties to the level of age-hardening alloys. However, dispersion leads to a significant increase not only in strength, but also in electrical resistance. The adverse effect on the electrical conductivity of dispersed particles will decrease with a decrease in the volume fraction of oxide, bringing the electrical conductivity closer to the level of copper. Based on an analysis of the materials of scientific research devoted to the production of dispersion-strengthened Cu–Al2O3 composites, it was concluded that the most significant progress in the dispersion of oxide particles with uniform distribution in the copper matrix of the composite was achieved using the method of electron beam evaporation and simultaneous deposition (condensation) of vapors of components in vacuum (EB–PVD). Structural studies of the morphology of aluminum oxide particles in dispersion-strengthened copper composites were carried out using methods such as: X-ray fluorescence analysis, transmission electron microscopy, and energy-dispersive X-ray spectroscopy (EDS). The average size of aluminum oxide particles in the studied dispersion-strengthened composites was in the range from 1.8 to 3 nm. In the work, the dependence of the specific electrical resistance of composites (ρ) on the oxide content was investigated. It was found that a decrease in the size of oxide particles leads to an increase in the electrical resistance of the dispersion-strengthened composite. The studies of the method of electron beam evaporation and subsequent condensation in vacuum, presented in the work, confirm the possibility of further dispersion of aluminum oxide particles with simultaneous narrowing of the distribution histogram. This opens up prospects for further improvement of vacuum dispersion-strengthened copper-based composites.

Optical Characteristics of Silver Thin Films from Island to Percolation in the Ultra-Wide Infrared Spectral Range

Silver (Ag) thin films have garnered significant attention due to their unique optical properties. This paper systematically investigates the optical characteristics of Ag films prepared using the electron beam evaporation method. The investigation was conducted using spectroscopic ellipsometry and covers a broad wavelength range of 1679 nm to 36 µm (0.738–0.034 eV), spanning from near-infrared to far-infrared regions. Optical and dispersion models were developed to analyze the impacts of Ag nanostructures on the complex refractive indices, dielectric functions, and reflectance. The results indicate that Ag particles and coalescence films exhibit non-metallic and low absorption properties, while Ag percolation and continuous films present a typical Drude model. The reflectance of Ag films increases as the film coverage ratio increases, and it can reach close to 100% in continuous film. Additionally, a non-destructive, non-contact, and vacuum-free means of confirming the percolation threshold of Ag films was proposed based on the slope of the imaginary part curve. This work is useful to guide simulations and provide a basis for the applications of Ag films in different fields.

The response of an Al-10B4C coupled neutron detector based on PIPS technology to Cf-252

After decades of discussions, it has been firmly established that detectors made of silicon-based semiconductor materials can be effectively used for neutron detection by simply coating them with suitable substances. The incident thermal neutrons interact with the coating neutron-sensitive materials such as 10B and 6LiF, resulting in the production of secondary charged particles which can be effectively detected in the sequencial silicon substrate. In this article, the detector system was designed with a coupled neutron detector structure which combined a silicon detector with a  10B4C film in various forms. The 10B4C layer was deposited on the substract with electron beam evaporation method. Two kinds of structrue were discussed: (1) one was the direct contact neutron detector by depositing 10B4C directly onto the front surface of silicon-based detectors; (2) the other was the coupled neutron detectors by depositing  10B4C onto substrates made from different materials such as Al and glass which then coupled with silicon-based detectors. The responses of these neutron detectors to neutrons (Cf-252) were measured individually. It's showen that the detection capability of direct contact neutron detectors was lower than the coupled neutron detectors. For the coupled detectors, the detector by depositing  10B4C on the aluminum substrate was found to be superior than that by depositing  10B4C on the glass substrate.

INFLUENCE OF TEMPERATURE ON THE PROPERTIES OF FREE LOADED INORGANIC OXIDE NANO POWDERS

A comparative study was carried out on the possibility of controlling the average sizes of nano-sized powders of silicon dioxide and aluminum oxide obtained by electron beam evaporation, pyrogenic, liquid chemical and plasma chemical methods, by keeping them in the temperature range of 800 – 1300 ?C in an air atmosphere. The average size of the resulting particles was estimated from specific surface area measurements using the Brunauer–Emmett–Taylor (BET) adsorption method at liquid nitrogen temperature. Crystallographic parameters in the treated powders were assessed using X-ray diffraction analysis. It has been shown that by appropriate choice of temperatures and initial powder, it is possible to achieve an average particle size in the resulting powder close to a given one and a phase composition.

A study of surface morphology of Fe/p-Si hybrid structure using atom force microscope

p-Si substrate was cleaned by chemical means. After the cleaning, iron thin film was deposited on the silicon substrate by electron beam evaporation method with high purity Fe target. Then, the roughness parameters of the sample after chemical cleaning and after obtaining a thin layer were compared. Surface roughness measurement of the iron thin film in the nanometer scale can be accurately determined using the AFM. Apart from the average roughness, all the roughness parameters of the surface increased. The average roughness, average height, root mean square roughness, and other parameters are used to analyze surface morphology.

Obtaining Multicomponent Coatings of a Stable Composition for Electromagnetic Radiation Screens

The formation processes of coatings of Cu–Ni and Ag–Cu systems with a stable elemental composition by the method of electron-beam evaporation are considered. It is shown that in the zone of action of the electron beam on the ingot placed in the crucible at the total vapor pressure of the alloy elements Σp above the pressure under the cap of the installation, the melt boils, and in the outer zone adjacent to the melt zone, the process of sublimation of the hard alloy occurs. The microrelief and elemental composition of the surface layer of the Cu–Ni alloy ingot in the zones of evaporation and sublimation, as well as the elemental composition of the coatings deposited in this case, have been studied. It is shown that the most acceptable way to obtain coatings of the Cu–Ni system with a stable elemental composition is the simultaneous electron-beam evaporation of copper and nickel from two crucibles. The azeotropic composition of the alloy of the Ag–Cu system was calculated and experimentally verified. The research results are used in the manufacture of multilayered screens of electromagnetic radiation.

Reactive e-beam evaporated SnOx layer as an effective ETL for highly efficient spray-coated perovskite solar cells

The spray-coating deposition method can extend the use of perovskite solar modules to substrates with different shapes and curvatures that can be used in various parts of buildings and vehicles to maximize the use of solar energy. Due to the lack of centrifugal forces in this method, unlike spin-coating, the quality of the deposited perovskite layer highly depends on the wettability and uniformity of the under layer. In this project, the SnOx layer is deposited by the reactive electron beam evaporation method (re-SnOx) as an electron transport layer for the spray-coated Cs0.05FA0.81MA0.14PbI2.55Br0.45 layer. Results show that spray-coated perovskite (PSK) layers are significantly more uniform on re-SnOx layers compared to the spin-coated commercial nanoparticles of SnOx (np-SnOx) due to their excellent surface coverage and purity. The best efficiency of 20.8% is obtained for re-SnOx/spray-coated PSK. Surface passivation of spray-coated PSK with phenethylammonium iodide improves all photovoltaic properties, increases efficiency from an average of 17.9%–19.6%, and reduces the hysteresis index from an average of 0.3 to 0.09. This low-temperature structure can be fabricated on plastic substrates, as well.

The corrosion resistance of Al-Fe-Co-Cr-Ni-Cu high entropy alloy coatings

A high entropy alloy AlxFeCoCrNiCu (x=0.5, 1) coating was prepared by the electron beam evaporation method on the surface of the steel. The influence of aluminum content on the corrosion resistance of the coating is discussed. The obtained results show that the HEA coatings retain the HEA phase structure without any phase change. The polarization curves show that the high entropy alloy coating of Al0.5FeCoCrNiCu had better corrosion resistance in 0.5 mol/L H2SO4 solution and 1 mol/L NaCl solution. This design of the HEA coatings provides a novel method for steel corrosion-resistant materials.

Особливості структури і фізико-хімічних властивостей міді, отриманої способом електронно-променевого випаровування-конденсації у вакуумі

Особливості структури і фізико-хімічних властивостей міді, отриманої способом електронно-променевого випаровування-конденсації у вакуумі

Features of the structure and physico-chemical properties of copper produced by the method of electron beam evaporation and condensation in vacuum

Features of the structure and physico-chemical properties of copper produced by the method of electron beam evaporation and condensation in vacuum

Electrical characteristics of Mg doped GeO2 NWs based device

In this article, the growth of a undoped GeO2 and Mg doped GeO2 nanowires (NWs) by electron beam evaporation method and analysis of its electrical properties has been reported. Au/GeO2 and Au/Mg-GeO2NWs based devices on Si substrate was fabricated. The optical band gap (Eg) for both the undoped GeO2 and Mg doped GeO2NWswas estimated to be 3.78 eV and 3.37 eV from UV–Vis spectrum. The temperature dependence current(I)–voltage(V) characteristics of undoped GeO2 based device shows a gradual increase of conductivity with the increase of temperature. Where, Mg doped GeO2NWs based device demonstrates a decreasing nature of conductivity with the increase of temperature. This anomalous characteristic has been explained by the positive temperature coefficient of resistance (PTCR) effect. The temperature dependent ideality factor of Mg doped GeO2NWsand undoped GeO2 NWs devices were studied. The increase in barrier height on increasing of temperature also been observed for the Mg doped GeO2NWs based device. Owing to the PTCR effect, the calculated series resistance of Mg doped GeO2NWs based device also shows an anomalous increasing behavior with the increasing of temperature where as undoped GeO2 based device shows a normal behavior of decreasing of series resistance with increase of temperature.

MgB2 thin films fabricated on Fe tape and effects of annealing on their properties

Magnesium diboride (MgB2) thin films were fabricated on Fe tapes by an electron-beam evaporation method and post-annealed at 650 °C for 1–5 h. Appropriate post- annealing (1 h) resulted in a critical temperature (T c) of 34.4 K and infield critical current density (J c) of 0.20 MA cm−2 at 20 K under 6 T. Characterization suggests that annealing improves the crystallinity of the MgB2 thin film; however, Fe diffuses into the MgB2 layer when annealing for longer durations, which deteriorates the superconductivity. MgB2 thin films on Fe tape can be utilized in diverse superconducting applications under external magnetic fields.

Improving the performance of perovskite solar cells by electron beam evaporation processing

Electron transport layer (ETL) plays an important role in the development of high performance perovskite solar cells (PSC). Here, we first compared the optical and surface morphology characteristics of titanium dioxide (TiO₂) thin films prepared by electron beam evaporation (EB) and hydrothermal (HT) method, as well as the device performance of perovskite solar cells, and then studied the effect of electron beam evaporation TiO₂ film thickness on the performance of perovskite solar cells. It was found that the morphology of TiO₂ ETL prepared by electron beam evaporation was more uniform and compact, and the surface root mean square roughness was lower than that of hydrothermal method, and the quality of the film was better. And the average transmittance of TiO₂ ETL prepared by electron beam evaporation was 94.67%. Compared with hydrothermal method, the PCE of TiO₂-based PSC devices based on electron beam evaporation was increased by 60%. The thickness of TiO₂ ETL was adjusted by electron beam evaporation, and a good surface morphology of the film was obtained. When the thickness was 75 nm, the ETL of the prepared PSC showed the best device performance, and the PCE reached 9.00%, showing excellent performance.

Self-powered and improved photoresponsive broadband photodetecting sensors using Au/NiFe2O4/p-Si heterojunction architecture

Recently, heterojunctions-based photodetectors (PDs) with outstanding photosensitivity and fast switching time received substantial attention due to their broadband (BB) photoresponse in various regimes of the electromagnetic spectrum. Still, there is an increasing demand to accomplish BB PDs operating at photovoltaic (self-driven) mode for serving the today's societal energy efficient needs. In this work, Au and NiFe2O4 thin films were deposited onto p-Si substrates to accomplish interdigitated Au/NiFe2O4/p-Si heterojunction type BB PDs operated in self-powered mode. The structural, optical, morphological and magnetic parameters of the prepared NiFe2O4 thin films as a function of annealing process were studied using XRD, UV–Vis, AFM and XAS/XMCD techniques. Tauc's plot fitted from the UV–Vis absorption data for the as-deposited, 700 °C and 800 °C NiFe2O4 thin films were 4.85, 3.42 and 2.85 eV, respectively. The photodetection parameters of the fabricated interdigitated Au/NiFe2O4/p-Si BB PDs were analyzed with I–V, photoresponsivity and response (rise/fall) times as a function of annealing process. All the fabricated Au/NiFe2O4/p-Si BB PD devices with/without annealing process operated in photovoltaic mode (at 0 V). The PD device annealed at 800 °C unveiled better photoresponsivity (12.35 A/W @1060 nm), detectivity (5.9 × 1014 Jones @1060 nm) and rise/fall times (89 ms/185 ms @900 nm) compared to the as-prepared/700 °C annealed PD devices. The reason for this was attributable to the accomplished improvement in crystallinity (XRD), surface morphology (AFM), reduction of bandgap (UV–Vis) and variation of spin/orbital magnetic moments (XAS/XMCD). In this work, we suggest one of the alternative and cost-effective electron beam evaporation method to grow the desired epitaxial NiFe2O4 thin films compared to the other physical vapor deposition approaches such as PLD and ALD to fit the future necessities of optoelectronic field.

Study on the structural and magnetic properties of e-beam evaporated Co thin films annealed in vacuum

The present paper investigates the effects of thermal annealing on the structural and magnetic properties of Co thin films. The films were prepared by using electron-beam evaporation method onto Si (100) wafers and annealed in vacuum at 200 °C, 300 °C and 400 °C. A combination of X-ray diffraction, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrometry were used to characterize structural properties and the composition of the films, while magnetic behavior was studied by magneto-optical Kerr effect measurements. It was found that as deposited Co layer show predominantly uniaxial magnetic anisotropy, while after annealing at 200 °C and 300 °C a strong influence of fourfold contribution is observed, which is assigned to the thermally induced HCP→FCC phase transition. With further increase in annealing temperature of 400 °C the isotropic contribution becomes the main component of magnetization. Besides, a strong variation in coercive field with annealing temperature was observed, where the coercivity seems to depend closely on the crystallite size. The highest value of HC equals ∼70 Oe and was found for the temperature of 400 °C, where also mixing at the interface has started and formation of CoSi was observed.

Physical vapour deposition of Zn2+ doped NiO nanostructured thin films for enhanced selective and sensitive ammonia sensing

Highly sensitive and selective ammonia sensors based on Zn2+ doped NiO thin films with well-controlled morphology through a substrate temperature variation developed with the electron beam evaporation method. The obtained films were systematically studied using various characterization techniques involving X-ray Diffraction, FESEM, EDS, XPS, AFM, RBS, UV–visible spectrophotometer and Hall effect measurements. The successful preparation of Zn2+ doped NiO thin films has been confirmed by structural, elemental and chemical analysis. The fabricated Zn: NiO sensors have shown excellent selectivity towards ammonia at 100 ppm concentration at room temperature. Sensors deposited with high temperatures ((≥300°C) were more sensitive towards ammonia with a fast response and recovery time (10/15 s) and a low detection limit of 10 ppm. The enhanced ammonia sensing performance could be attributed to the high surface-to-volume ratio and high porosity of films deposited at substrate temperature (≥300°C), and electronic sensitization through Zn2+ incorporation into NiO lattice. The addition of Zn into NiO caused rapid adsorption of oxygen adsorbates on the surface of doped NiO, which increased the sensor's response. The sensing mechanism for the detection of ammonia is formulated. The outcome of this work opens a pathway for the efficient detection of ammonia at ambient temperature for numerous medical and industrial applications.

Tailoring of defects dependent magnetic properties of swift heavy ion irradiated CeO2 for spintronics application

The present investigation reports the swift heavy ion induced effects on cerium oxide (CeO2) thin films. These thin films were deposited on Si (111) substrates by the electron-beam evaporation method and irradiated by a 100 MeV O7+ ion beam with different ion fluences. X-ray diffraction analysis of these films confirms the stable fluorite phase of CeO2 even after the higher fluence of irradiations. Raman measurement also supports the presence of the F2g phase of CeO2 and the presence of defect states. The Gaussian deconvolution of photoluminescence (PL) spectra reveals various defect-associated peaks. The broad peaks in the PL spectra are associated with oxygen vacancies and are red-shifted (494–520 nm) with ion fluences. The surface morphological images show the modification in the surface roughness with ion irradiation and the re-growth of smaller circular-formed nanoparticles on the surface is observed at the fluence of 5 × 1011 ions/cm2. Magnetic measurements show an enhancement in magnetic ordering with ion irradiation. All the samples demonstrate room temperature ferromagnetism with magnetic saturation (Ms) up to 14.57 emu/cm3. The saturation magnetization in irradiated thin films is directly correlated to the area under the peak of defect-associated PL emission. The mechanism such as the oxygen vacancy-based F-center exchange model is considered to understand the enhancement of ferromagnetism in ion irradiated CeO2 thin films. Some popular theoretical models are also employed to determine various magnetic parameters.

Nanoluminofors based on siliсates and germanates of rare earth elements for visualization of biotissues

Nanoparticles of silicates and germanates with a general formula Sr2R8–x–yErxYbyM6O26 (R = Y, La; M = Si, Ge) were produced in vacuum by the method of pulse electron beam evaporation. An upconversion photoluminescence of the nanoparticles was detected during the excitation by a laser with a wavelength of 980 nm with a predominance of lines in the red and near infrared regions of the spectrum. Due to their optical properties, the nanoparticles can be excited directly through the biotissues to visualize various pathologies. The obtained nanosamples have K-jumps of X-ray radiation absorption in the 10−100 keV energy region. This opens up prospects for the use of the nanoparticles as X-ray contrast agents. Thus, the nanoparticles have both optical and X-ray contrast characteristics, and therefore have the potential necessary for imaging and diagnosing pathologies in biological tissues.

Annealing induced morphology evolution and phase transition in SnOx thin films grown by e-beam evaporation method

In the present work, we demonstrate the growth of tin oxide (SnOx) thin films using electron beam evaporation method to study the phase transition from stannous oxide (SnO) to stannic oxide (SnO2) by varying annealing temperature (i.e., from 300 to 700 °C). Annealing induced morphology evolution and structural modifications stimulate the process of phase-transformation, which is primarily discussed by divided the entire temperature range into two-regimes. Regime-A (from 300 to 400 °C) consists of tetragonal α-SnO dominated phase, regime-B (from 600 to 700 °C) exhibits orthorhombic pure SnO2 phase. However, these regimes are being separated by an interface conferring a mixed-phase of tin oxides at an annealing temperature ∼500 °C. This temperature-dependent phase-inversion is adequately controlled by tuning the morphological, structural and optical properties of SnOx thin films to develop homo/heterostructures for various photovoltaic and optoelectronic applications.