Reactive Evaporation Technique Research Articles

Antimicrobial Activity against Fusarium oxysporum f. sp. dianthi of TiO2/ZnO Thin Films under UV Irradiation: Experimental and Theoretical Study.

We deposited bare TiO2 and TiO2/ZnO thin films to study their antimicrobial capacity against Fusarium oxysporum f. sp. dianthi. The deposit of TiO2 was performed by spin coating and the ZnO thin films were deposited onto the TiO2 surface by plasma-assisted reactive evaporation technique. The characterization of the compounds was carried out by scanning electron microscopy (SEM) and powder X-ray diffraction techniques. Furthermore, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were performed to support the observed experimental results. Thus, the removal of methylene blue (MB) by adsorption and posterior photocatalytic degradation was studied. Adsorption kinetic results showed that TiO2/ZnO thin films were more efficient in MB removal than bare TiO2 thin films, and the pseudo-second-order model was suitable to describe the experimental results for TiO2/ZnO (q e = 12.9 mg/g; k 2 = 0.14 g/mg/min) and TiO2 thin films (q e = 12.0 mg/g; k 2 = 0.13 g/mg/min). Photocatalytic results under UV irradiation showed that TiO2 thin films reached 10.9% of MB photodegradation (k = 1.0 × 10-3 min-1), whereas TiO2/ZnO thin films reached 20.6% of MB photodegradation (k = 3.9 × 10-3 min-1). Both thin films reduced the photocatalytic efficiency by less than 3% after 4 photocatalytic tests. DFT study showed that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap decreases for the mixed nanoparticle system, showing its increased reactivity. Furthermore, the chemical hardness shows a lower value for the mixed system, whereas the electrophilicity index shows the biggest value, supporting the larger reactivity for the mixed nanoparticle system. Finally, the antimicrobial activity against F. oxysporum f. sp. dianthi showed that bare TiO2 reached a growth reduction of 68% while TiO2/ZnO reached a growth reduction of 90% after 250 min of UV irradiation.

The influence of corrosive medium on the selected tribological properties of ZrSi-based nitride and oxynitride deposited on 316L stainless steel

Targeting to restore the function of load-bearing joints which are subjected to high levels of friction and wear during the normal activity, the aim of the current study was to assess the extent of the role played by the corrosive environment on the underlaying tribological mechanism. In this study we deposited by reactive cathodic arc evaporation technique ∼ 1 μm thick, stoichiometric ZrSi-based nitrides and oxynitrides coatings, either as monolayer or double-layer structure on 316L steel substrates. Tribological tests were conducted in dry and two commonly used corrosive environments: Ringer and 0.9 % NaCl solutions. We demonstrate that the ZrSiN and ZrSi(N,O) coatings improved the wear performance of 316L stainless steel in biological environments, reaching even ∼ 94 % improvement as compared with the bare substrate for the ZrSi(N,O) coating.

Functional enhancement of laser deposited carbon-based supercapacitor electrodes upon post-annealing treatment

The development of new synthetic methods is paramount for the versatile production of complex multicomponent electrodes for supercapacitors with enhanced performance. The reactive inverse matrix assisted pulsed laser evaporation (RIMAPLE) technique shows promise for the deposition of complex functional nanocomposites in a facile way. In this work, hybrid supercapacitor electrodes constituted by reduced graphene oxide (rGO) and carbon nanotubes (CNTs) decorated with a myriad of cerium and manganese oxide nanoparticles were obtained by using GO sheets, CNTs, CeO2 nanoparticles and, for the first time, the (NH4)2[Mn2(C6H5O7)2(H2O)2] coordination compound as precursors in the RIMAPLE targets. Compositional and structural characterizations revealed that post-annealing treatments at mild conditions (150-250 °C) induce a further reduction of the rGO and CNTs, besides an oxidation of the Ce oxide phases (Ce3+ to Ce4+) and a reduction of the Mn oxides (Mn3+ to Mn2+). The substantial change of the carbon and metal oxide nanostructures causes an up to 8-fold increase of the capacitance of the electrodes (63 F/cm3 @ 10 mV/s). Finally, the generation of a high quantity of edge defects at 250 °C and long dwell time leads to the drop of the electrode's capacitance.

Deposition and Application of Indium-Tin-Oxide Films for Defrosting Windscreens

The plasma-activated reactive evaporation technique was used for the formation of indium-tin-oxide (ITO) films. The ITO films were deposited on a heated (up to 350 °C) glass substrates using various mass ratios of indium and tin. The optical and electrical properties of the deposited ITO films were determined. The influence of the indium-to-tin mass ratio on the optical transmittance, bandgap, resistivity and resistance of ITO films was investigated. The bandgap of ITO films was increased from 3.18 to 3.37 eV, and the MIn/MSn ratio increased from 4.25 to 10.00. The average values of optical transmittance at the visible light wavelengths increased from ~43% to ~64% as tin mass was reduced. We demonstrated that ITO films with low resistivity ranging from 7.4 × 10−3 to 43.7 × 10−3 Ω·cm were obtained, and the MIn/MSn ratio changed from 4.25 to 10.00. The ITO film formed at the 9.25 MIn/MSn ratio demonstrated high transparency, a wide bandgap and optimal resistivity and resistance values. The heating characteristics indicated that the frozen ice on the ITO films was completely removed after 30 s when the applied voltage was 24 V.

Energy gaps, refractive index and photon emission from point defects in copper-doped Gd2O3 nanocrystalline films

Thin nanocrystalline films of gadolinium oxide (undoped and doped with copper ions) were synthesized by means of reactive anodic evaporation technique. Chemical composition inspection and structural-phase analysis of the samples obtained were performed by XPS and XRD methods. Optical characteristics (energy gaps, refractive index, emission parameters) of thin films were determined by means of absorption, transmission and photoluminescence spectroscopies. It was found that injection of copper leads to an insignificant decrease in the transparency gaps for direct and indirect transitions of Gd2O3 film. On the basis of interference effects, a decrease in refractive index and an increase in its dispersion in Gd2O3:Cu film were established. The excited by energy transfer from "defective" Gd3+ ions emission bands at 2.9 eV and 3.2 eV were associated with oxygen vacancies (F+- centers) localized near C2 and S6 cationic positions in Gd2O3 host. The injection of copper ions into Gd2O3 host stimulates the formation of lattice defects and leads to an increase in the luminescence yield. An analytical expression was obtained for describing luminescence flare-up and quenching. The corresponding thermal activation barriers were determined. The transfer of excitation energy between intrinsic defects of Gd2O3 film provides the conversion of hard UV radiation into soft UV and visible radiation.

Laser synthesis of TiO2–carbon nanomaterial layers with enhanced photodegradation efficiency towards antibiotics and dyes

Graphene-based photocatalytic layers were prepared by reactive matrix assisted pulsed laser evaporation technique. Binary, nitrogen doped reduced graphene oxide (RGO)/TiO2 and ternary RGO/TiO2/graphitic carbon nitride (g-C3N4) compounds were synthesized and simultaneously deposited onto solid substrates. Aqueous dispersions of commercial graphene oxide platelets and TiO2 nanoparticles were prepared. NH3 or melamine powder was added to the dispersions to achieve enhanced nitrogen doping and synthesis of g-C3N4 during laser irradiation. The photocatalytic efficiency of the layers towards degradation of antibiotic, chloramphenicol and organic dye molecules was systematically investigated and correlated with structural, compositional, and morphological features. This study provides new insights into the importance of TiO2 crystal facets and the synergistic effects between TiO2 nanocrystals and the other constituents, nitrogen doped RGO and g-C3N4 of the hybrid layers. As a result of combined effect of constituent materials, TiO2, RGO, and g-C3N4 as well as N doping of RGO, through the generation of quaternary and pyrrolic N functionalities, the composite layers showed high photocatalytic efficiency for degradation of organic molecules. Stability and reusability experiments indicated that the composite layers maintain their high photodegradation efficiency towards organic molecules during consecutive degradation cycles. Active radical scavenging experiments were also carried out in order to determine the role of the main active species involved in the photocatalytic degradation process.

Al doping for bipolarity induction in transparent conducting CuInO2 and its application in diode fabrication

Al doping is used in transparent conducting CuInO2 (CIO:Al) thin films for producing bipolar electrical conductivity. The doped thin films of electrical conductivity ~2 to 4 S/cm and mobility 100 to 101 V/cm2 are deposited by oxygen plasma assisted reactive evaporation technique. The change in conductivity from n-to p-type with the variation in doping atomic percentage is confirmed by multiple techniques like hot probe, hall and Seebeck measurements. The as deposited amorphous films are found to assume 3R poly type delafossite structure after post air annealing at 673 K. The suitability of the doped films in transparent device fabrication is verified by construction and characterization of a diode with configuration FTO/n-CIO:Sn/p-CIO:Al/Ag.

Fabrication of n-In6Se7:Sn/p-CuInSe2 heterojunction diode on FTO coated glass substrates using reactive evaporation technique

The heterojunction diode using Sn doped In6Se7 and CuInSe2 thin films are fabricated on FTO coated glass substrates using reactive evaporation technique. The structure of CuInSe2 film is studied using XRD analysis and the film exhibits polycrystalline nature. XPS result confirms that the prepared sample is nearly stoichiometric. The I–V measurements of FTO/n-In6Se7:Sn/p-CuInSe2/Ag heterojunction diode, in dark condition, shows rectification behavior. The knee voltage and ideality factor of the diode are observed to be 1.52 V, 3.09 V and 5.57, 16.16 respectively when the Sn dopant concentration varied from 0.47 at% to 1.57 at%. The absence of photoresponse from the diodes under illumination condition is explained using the energy band structure of the heterojunction.

Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporation

This work reports on low temperature deposition of conducting indium oxide films by a radio-frequency plasma enhanced reactive thermal evaporation (rf-PERTE) technique. The films were deposited on polyethylene terephthalate (PET) without intentional heating of the substrate and at elevated temperatures up to 150 °C. The material stoichiometry was accurately controlled by adjusting deposition conditions including the oxygen flow, process pressure, pumping speed, and RF-power. Besides, fine turning of the critical deposition parameters during the deposition was implemented by measuring the variation of film conductance in-situ. The film morphology was analyzed by scanning electron microscopy. Hall effect measurements were also performed to determine the relation between the deposition conditions and the electrical properties of the films. A resistivity of 4 × 10−4 Ω-cm was reached under optimized deposition conditions. A 250 nm-thick coating with 16 Ω/sq sheet resistance shows an 82% peak value of transmittance in the visible spectral range.

Oxygen controlled E-beam evaporation deposited p-SnOx thin film for photosensitive devices

Abstract Thin SnOx films of different thicknesses at different oxygen pressures were deposited on glass substrate using reactive E-beam evaporation technique. Significant changes in the optical and structural properties of the films with change in oxygen pressure are observed. Experimentally obtained absorption coefficient and band gap of SnOx suggests its prospective use as suitable absorber material for photoconductive and photovoltaic devices. In addition to the oxygen pressure, thickness of SnOx layer has also an important role on its optical and structural properties.

Improvement of polycrystalline InN thin films properties by localized ion source under low RF plasma ambient

Polycrystalline InN/Si(111) were prepared using plasma-assisted reactive evaporation technique under localized ion source (LIS). It was shown that in presence of LIS the structural, compositional, morphological and optical properties of the films can be engineered. XRD and Raman results revealed that shorter LIS-to-substrate distance ( $$d_{LIS - s} )$$ results in higher crystallinity. From XPS and EDX mapping it was concluded that as $$d_{LIS - s}$$ decreases, the incorporation of N into the InN films is enhanced. More uniform, compact and smooth films are obtained as the LIS is placed more adjacent to the substrate. From the optical results it was found that by using LIS, the band gap energy ( $$E_{g}$$ ) of the samples decreases from 1.97 to 1.23–1.37 eV which could be applicable in solar cell devices.

Fabrication of graphene-based electrochemical capacitors through reactive inverse matrix assisted pulsed laser evaporation

Electrodes constituted by nitrogen-doped reduced graphene oxide (NrGO) in combination with NiO nanostructures were fabricated by means of reactive inverse matrix assisted pulsed laser evaporation technique. The structure-composition of the electrode composites was tailored by laser-inducing chemical reactions of graphene oxide (GO) flakes with different precursor molecules (citric acid, ascorbic acid and imidazole) during GO deposition. Structural characterizations reveal the formation of wrinkles and nanoholes in the NrGO sheets, besides their coating with NiO nanostructures. Compositional studies disclose that imidazole precursor promotes the synthesis of NrGO with the largest degree of reduction and nitrogen doping (mainly with graphitic and pyridinic N). Electrochemical analyses of the obtained electrodes reveal that NiO nanostructures increase surface charge storage processes (double layer – pseudocapacitive) over diffusive ones, being the imidazole-based electrodes the ones exhibiting the best performance (up to 114 F cm−3 at 10 mV s−1). Symmetric and asymmetric electrochemical capacitors were also fabricated showing excellent robustness over 10,000 charge-discharge cycles at high specific currents.

A study of conditions of Al2O3 coatings deposition by the anodic reactive evaporation of aluminum

The conditions of the stable burning of high-current discharge with a self-heating hollow cathode and a hollow anode were studied. The parameters of the ion flow and the double electric layer arising in the vicinity of the hollow anode aperture were determined. It was shown that the use of a hollow anode allows for increasing the ion current density ∼2-fold compared to the mode of discharge burning with a flat anode and provides for an increase in the molecular gas dissociation degree. Single-phase nanocrystalline α-Al2O3 coatings were obtained at a temperature of 600°C using the reactive anode Al evaporation technique.

Modification of the optoelectronic properties of reactively evaporated In6Se7 thin films by Sn doping for photovoltaic applications

Sn doped In6Se7 thin films with 5 wt% and 10 wt% Sn are prepared on glass substrate using reactive evaporation technique. The samples are characterized by XRD, FESEM, XPS and UV–Vis–NIR Spectrophotometer. XRD result shows that the samples are polycrystalline with monoclinic structure. Presence of compressive strain and lattice space shrinkage is observed in 10 wt% Sn doped sample. A detailed study of the optical properties demonstrated that a blue shift of 0.02 eV in the optical band gap of 5 wt% Sn doped sample is due to Burstein–Moss effect. Band gap narrowing in 10 wt% Sn doped sample is explained in terms of defect induced static disorder. 5 wt% Sn doped sample exhibits lowest resistivity and improved photoconductivity compared to undoped sample. This enhancement in optoelectronic properties facilitates the use of such films in photovoltaic applications.

Structural, optical, ac conductivity and dielectric relaxation studies of reactively evaporated In6Se7 thin films

Polycrystalline In6Se7 thin films are prepared on glass substrate by reactive evaporation technique at a substrate temperature of 523 K under a vacuum of 10−5 mbar. The samples are characterized using XRD, SEM, EDAX and UV-Vis-NIR Spectrophotometer. Photoconductivity studies in the prepared sample shows that the decay follows stretched exponential function with an effective relaxation time of 3.45 × 104 s. Dc conductivity measurements are done to study the dependence of conductivity on temperature. Dielectric properties and ac conductivity studies of the prepared sample are done in the frequency range 5 Hz–300 KHz and in the temperature range 303 K–383 K. The ac conductivity is found to vary as ωs with the index 0.9389 ≤ s ≤ 0.9631 and it decreases with increase in temperature. The calculated ac activation energy value is less than that of dc activation energy and it decreases with increase in frequency. These result shows that correlated barrier hopping (CBH) mechanism is the dominant conduction mechanism in the prepared In6Se7 sample. From ac conductivity, the density of states at fermi level is calculated and is of the order of 1018 eV−1 cm−3. Capacitance and dielectric loss are found to decrease with increase in frequency and increase with increase in temperature, which is in agreement with the existing equivalent circuit model. Studies using complex impedance spectroscopy shows a non-Debye type relaxation in the prepared film. Dielectric modulus studies reveal a long range to short range transition in the mobility of the charge carriers with the increase in frequency.

Annealing effects on microstructure and laser-induced damage threshold of HfO2/SiO2 multilayer mirrors.

HfO2/SiO2 periodic multilayer high reflection mirrors have been prepared by a reactive electron-beam evaporation technique. The deposited mirrors were annealed in the temperature range from 300°C to 500°C. The effects of annealing on optical, microstructural, and laser-induced damage characteristics of the mirrors have been investigated. The high reflection band of the mirror shifts toward a shorter wavelength with increasing annealing temperature. As-deposited and annealed mirrors show polycrystalline structure with a monoclinic phase of HfO2. Crystalinity and grain size increase upon annealing. The laser-induced damage threshold (LIDT) has been assessed using a 532 nm pulsed laser at a pulse width of 7 ns. The LIDT value of the multilayer mirror increases from 44.1 J/cm2 to 77.6 J/cm2 with annealing up to 400°C. The improvement of LIDT with annealing is explained through oxygen vacancy defects as well as grain-size-dependent thermal conductivity. Finally, the observed laser damage morphology, such as circular scalds and ablated multilayer stacks with terrace structure, are analyzed.

Effect of nitrogen flow rate on structural, morphological and optical properties of In-rich InxAl1−xN thin films grown by plasma-assisted dual source reactive evaporation

In-rich InxAl1−xN thin films were deposited on quartz substrate at various nitrogen flow rates by plasma-assisted dual source reactive evaporation technique. The elemental composition, surface morphology, structural and optical properties of the films were investigated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Raman spectroscopy, X-ray diffraction (XRD), UV–vis spectrophotometer and photoluminescence (PL) measurements. XPS results revealed that the indium composition (x) of the InxAl1−xN films increases from 0.90 to 0.97 as the nitrogen flow rate is increased from 40 to 100sccm, respectively. FESEM images of the surface and cross-sectional microstructure of the InxAl1−xN films showed that by increasing the N2 flow rate, the grown particles are highly agglomerated. Raman and XRD results indicated that by increasing nitrogen flow rate the In-rich InxAl1−xN films tend to turn into amorphous state. It was found that band gap energy of the films are in the range of 0.90–1.17eV which is desirable for the application of full spectra solar cells.

Production and characterization of thin film group IIIB, IVB and rare earth hydrides by reactive evaporation

A recent short history of reactive evaporation by D. M. Mattox [History Corner—A Short History of Reactive Evaporation, SVC Bulletin (Society of Vacuum Coaters, Spring 2014), p. 50–51] describes various methods for producing oxides, nitrides, carbides, and some compounds, but hydrides were not mentioned. A study was performed in the mid-1970s at the General Electric Company Neutron Devices Department in Largo, FL, by the author to study preparation of thin film hydrides using reactive evaporation and to determine their unique characteristics and properties. Films were produced of scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), and the rare earth praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy), and erbium (Er) hydrides by hot crucible filament and electron beam evaporation in atmospheres of deuterium and tritium gases. All-metal vacuum systems were used and those used with tritium were dedicated for this processing. Thin film test samples 1000 nm thick were prepared on 1.27 cm diameter molybdenum disk substrates for each occluder (i.e., an element that can react with hydrogen to form a hydride) material. Loading characteristics as determined by gas-to-metal atomic ratios, oxidation characteristics as determined by argon–sputter Auger analysis, film structure as determined by scanning electron microscope analysis, and film stress properties as determined by a double resonator technique were used to define properties of interest. Results showed hydrogen-to-metal atomic ratios varied from 1.5 to 2.0 with near maximum loading for all but Pr and Nd occluders which correlated with the oxidation levels observed, with all occluder oxidation levels being variable due to vacuum system internal processing conditions and the materials used. Surface oxide levels varied from ∼80 Å to over 1000 Å. For most films studied, results showed that a maximum loading ratio of near 2.0 and a minimum surface oxide level of ∼80 Å could be obtained with a bulk film oxygen level of ∼0.54 oxygen as determined by microprobe analysis when an evaporation rate of ∼0.313 mg/cm2 min was used in an atmosphere of D2 or T2 gas at a system deposition pressure of 1 × 10−3 Torr (1.33 × 10−1 Pa) in an evaporation time of ∼2 min. Platelet type (i.e., a film microstructure showing an overlay of flat plates with large grain sizes) film structures were observed for most films with some film mechanical properties determined (i.e., grain size and Vickers μ-hardness), and reduced stress levels were seen with initial normalized differential (tensile) stress levels being (1.0–4.0) × 108 dyne/cm2 for tritium loaded samples and (1.5 ± 0.5) × 109 dyne/cm2 for deuterium loaded samples. Also, stress aging characteristics were determined for some hydride films prepared in a radioactive tritium gas atmosphere. Tritium loading, however, had the undesirable characteristic of having to dispose of the internal processing system fixtures, which can be minimized, but the reactive evaporation technique produced desirable thin films.

Electrical and photoconductivity studies on AgSbSe2 thin films

Silver antimony selenide thin films have been deposited on ultrasonically cleaned glass substrate at a vacuum of 10−5 torr using reactive evaporation technique. The preparative parameters like substrate temperature and incident fluxes have been properly controlled in order to get highly reproducible compound films. The polycrystalline nature of the sample is confirmed using XRD. The dependence of the electrical conductivity on the temperature has also been studied. The prepared AgSbSe2 samples show p-type conductivity. The samples show a little photoresponse.

Characterization of Aluminum Doped Zinc Oxide (Azo) Thin Films Prepared by Reactive Thermal Evaporation for Solar Cell Applications

Aluminium doped Zinc Oxide (AZO) thin films have been deposited using reactive thermal evaporation technique using an Edward Auto 306 Magnetron Sputtering System. Transmittance and reflectance data in the range 300 nm-2500 nm were obtained using UV-VIS NIR Spectrophotometer Solid State 3700 DUV for all the thin films samples that were prepared. Transmittance values of above 70% were observed. The optical measurements were simulated using SCOUT 98 software to determine optical constants and optical bad gap of the thin film. The optical properties in these films were varied by varying Aluminums doping percentages. It was observed that the transmission over the visible range decreased as the concentration of Aluminum increased. This is due to free carriers coupling to the electric field hence increasing the reflection. Optical band gap for various samples of Aluminum doped thin films show a direct allowed transition and a shift in the optical absorption edge as the Aluminums concentration increased. These results show values of band gap ranging between 3.2 eV and 3.5 eV. Between 0% - 3% the optical band gap reduces. This is followed with widening of the band gap for doping between 4%- 6%. Urbach energy gradually increased with increasing band gap. The band gap reduced due to formation of localized states near the conduction band corresponding to increase in Urbach energy.