Vacuum Vapor Deposition Research Articles

Improving the Electroluminescence of [Zn(salophen)(OH2)] in Polyfluorene-Based Light-Emitting Diode: The Role of Energy Transfer and Charge Recombination

Combining two or more different compounds with advantageous properties has been a useful and straightforward strategy in achieving a new class of materials with improved physical properties. This has been especially true for electronic polymers, whose optoelectronic properties can be completely tuned, and even improved, when mixed with other polymeric materials, dye molecules and guest coordination compounds. Here, a light-emitting diode prepared with the conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(9,9-di-{5'-pentanyl}-fluorenyl-2,7-diyl)] (PFOFPen) as the host material and aquo[N,N'-bis(salicylidene)-o-phenylenediamine]zinc(II) ([Zn(salophen)(OH2)]) as the guest molecule was studied in terms of its photo and electroluminescence properties. The role of the ZnII coordination compound as a guest in the electroluminescence is discussed as a strategy for the improvement of the electroluminescence performance of coordination compounds using conjugated polymers as matrices. An additional advantage of these composites is that they are solution processable, a low-cost and time efficient alternative to vacuum vapor deposition. Additionally, the photophysical processes involved in both electroluminescence and photoluminescence emissions are discussed because they are markedly different.

Comparative life cycle assessment of laminated and vacuum vapor-deposited thin film solid-state batteries

Lamination technologies used to produce lithium ion batteries are limited by the capital investment needed for multiple unit operations, solvent use for electrolyte and electrode slurries, and an inability to exert control over active material particle morphology and homogeneity. Advancements in thin-film solid-state processing using vacuum coating hold promise to overcome these challenges for batteries with superior energy density and cycle life, if cost and scalability issues can be overcome. A comparative life cycle assessment is reported for battery production using lamination and thin-film vacuum vapor deposition. Lithium vanadium oxide solid-state cells are found to have the lowest impact, per unit energy storage, in cumulative energy demand (CED), global warming potential (GWP), and six other midpoint environmental indicators. Human health and resource depletion impacts are generally higher for lithium manganese oxide and lithium cobalt oxide solid-state cells than for their laminated counterparts, whereas CED and GWP per unit energy storage are 25–65% lower for solid-state cells across all cathode chemistries. Sensitivity analysis, taking into account uncertainties related to solid-state cell properties and vacuum vapor deposition process efficiencies, indicates that CED and GWP impacts for battery electric vehicle mobility using packs with solid-state cells will be lower than those incurred using laminated cells.

Optical amplification and photodegradation in films of spiro-quaterphenyl and its derivatives

Fluorescence spectra and optical constants in planar waveguides of spiro-quaterphenyl and two of its derivatives are investigated. Threshold of amplified spontaneous emission (ASE) and optical gain are determined. The thickness dependence of ASE spectral position, ASE threshold, and optical gain are investigated as well. Additionally, photodegradation in air and in vacuum for spiro-quaterphenyl and methoxy-spiro-quaterphenyl is compared. Films with various thicknesses (30–220nm) have been deposited by vacuum vapor deposition. A measurement setup based on the variable stripe length method was used to determine the threshold and the optical gain using ASE. A threshold of 22±5.7µJ/cm2, 51±2.1µJ/cm2 and 70±10µJ/cm2 was measured for spiro-quaterphenyl, methoxy-spiro-quaterphenyl and phenoxy-spiro-quaterphenyl respectively. At pump energy fluence of 3000µJ/cm2, maximum gain of 107.5±7cm−1, 104±6cm−1 and 184±1.2cm−1 was achieved for spiro-quaterphenyl, methoxy-spiro-quaterphenyl and phenoxy-spiro-quaterphenyl respectively.

Determining whether metals nucleate homogeneously on graphite: A case study with copper

We observe that Cu clusters grow on surface terraces of graphite as a result of physical vapor deposition in ultrahigh vacuum. We show that the observation is incompatible with a variety of models incorporating homogeneous nucleation and calculations of atomic-scale energetics. An alternative explanation, ion-mediated heterogeneous nucleation, is proposed and validated, both with theory and experiment. This serves as a case study in identifying when and whether the simple, common observation of metal clusters on carbon-rich surfaces can be interpreted in terms of homogeneous nucleation. We describe a general approach for making system-specific and laboratory-specific predictions.

Influence of host matrices on krypton electron binding energies and KLL Auger transition energies

The low-energy electron spectra emitted in the radioactive decay of the 83Rb and 83Sr isotopes were measured with a combined electrostatic electron spectrometer. Radioactive sources used were prepared by ion implantation of 83Sr into a high purity polycrystalline platinum foil at 30keV and by vacuum-evaporation deposition of 83Rb on the same type of foil. From the measured conversion electron spectra, the electron binding energies (referenced to the Fermi level) for the K, L1, L2, L3, M1, M2, and M3 shell/subshells of krypton in the platinum host were determined to be 14316.4(12), 1914.3(9), 1720.3(9), 1667.6(9), 281.5(9), 209.6(13), and 201.2(15)eV, respectively, and those for the evaporated layer were observed to be lower by 0.7(1)eV. For both host matrices, values of 2.3(2), 4.6(2), 1.7(2), 1.3(2), and 3.2(3)eV were obtained for the krypton K, L1, L2, L3, and M1 natural atomic level widths, respectively. The absolute energies of 10838.5(9) and 10839.5(10)eV were measured for the KL2L3(1D2) Auger transition in krypton implanted in Pt and generated in the evaporated rubidium layer, respectively. A value of 601.0(8)eV was measured for the energy difference of the KL2L3(1D2) transitions in Rb and Kr in the Pt host. Multiconfiguration Dirac–Fock calculations of the krypton KLL transition energies and intensities were also performed.

Nanosilver surface plasmon response enhanced the photovoltaic performance of organic solar cells

Nanosilver island thin films with different thickness were synthesized by vacuum vapor deposition between ITO and PEDOT:PSS for organic solar cells, forming the structure of ITO/AgNPs layer/PEDOT:PSS/P3HT:PCBM/LiF/Al. Surface morphology and UV–vis absorption spectrum were investigated by AFM and UV–vis scanning spectrophotometer. It was found that after adding the nanosilver film, the optical properties of the device were enhanced with increasing the thickness of nanosilver island films. When the thickness of nanosilver thin films is 3.0nm, the most significant surface plasmon response and red-shift of the resonance absorption peak appeared. Meanwhile, short circuit current density of the device increased from 9.93mA/cm2 to 12.98mA/cm2, the fill factor increased from 49.35% to 52.79% and the power conversion efficiency increased from 3.05% to 4.01%. These results provided a theoretical guidance to optimize the design and increase the performance of solar cells.

Film electrodes deposited from Cu2SnSe3 source in comparison with those deposited from SnSe and Cu2ZnSnSe4 sources by thermal vacuum evaporation: Effect of argon gas flow rate

Addition of argon gas, with different flow rates, to vacuum evaporation deposition of film electrodes from Cu2SnSe3 source, affect nature and properties of the resulting films. While keeping other factors constant, it is possible to control nature and properties of the resulting films simply by controlling the argon gas flow rate. This work shows that films deposited from Cu2SnSe3 under high argon gas flow rate (25 cm3/min) involved SnSe as a major compound, with low concentration of Cu dopant. The film showed higher photoresponse than those deposited from pristine SnSe source. Under lower argon gas flow rates, the resulting films were dominated by the ternary source compound itself, which also showed lower photoresponse than that deposited under higher flow rate. Structure, morphology, chemical composition, optical and photo-electrochemical characteristics have all been studied for films deposited from Cu2SnSe3 under different argon gas flow rates, in parallel with earlier films deposited from SnSe and Cu2ZnSnSe4. The films deposited from Cu2SnSe3 or Cu2ZnSnSe4 under high argon gas flow rate showed a p-type semiconductor behavior with energy gap of about 1.0eV which confirms the existence of SnSe as a dominant component in each case. A mechanism, which is mainly based on a model of elastic collisions, is proposed to explain the production of SnSe films from the ternary and quaternary sources. On the other hand, the presence of low concentrations of Cu or/and Zn species in the resulting SnSe films is presumably responsible for enhanced photoresponse, as compared to films deposited from pristine SnSe.

Crystal growth of rubrene in ionic liquids by vacuum vapor deposition

The crystal growth and unique morphological changes of organic semiconductor rubrene, fabricated by ionic liquid (IL)-assisted vacuum vapor deposition, were investigated. The texture and structure of rubrene films strongly depended on the thickness of IL films on substrates, namely, three-dimensional dendrites in 3D-ILs, two-dimensional microfibrils in 2D-ILs, and two-dimensional spherulites in 0D-ILs. The growth of two-dimensional spherulites would be promoted by the supersaturation of ILs, minutely controlling the rate and total amount of rubrene deposition. The growth mechanisms of rubrene fabricated by IL-assisted vacuum vapor deposition were different from that of the conventional one in terms of the nucleation and growth modes.

Preparation and Properties of Ag Nanofilms for Organic Solar Cells

nanoAg island thin films with different thickness have been prepared by vacuum vapor deposition method on ITO substrates for organic solar cells. UV-Vis absorption spectrum and surface morphology have been studied by UV-Vis scanning spectrophotometer and SEM. The influence of different thickness nanoAg has also been discussed. The results show that, when the nanoAg thickness is 3.0 nm, the surface plasmon response is most obvious, the resonance absorption peak appears red-shift, the surface plasmon response could enhance optical absorption, photocurrent, fill factor and power conversion efficiency obviously. The research results provide theoretical guidance to optimize the design and increase the performance of solar cells.

Chemical Synthesis of Silicon Nanosheets from layered calcium disilicide

The synthesis of silicon nanosheets (SiNSs) without using conventional vacuum processes and vapor deposition is challenging and is anticipated to receive significant attention for a wide range of applications. Thereby, mass production of silicon nanosheets with low cost can be achieved using top-down approach starting from materials including a 2D sheet structure as a fundamental unit. We have recently, developed a soft synthetic method for the preparation of silicon sheets in gram-scale quantities by redox-assisted chemical exfoliation (RACE) of calcium disilicide (CaSi2). In this review, we will present chemical methods for the synthesis and modification of silicon sheets.

Study of Influencing Factors on Vacuum Evaporation Film Thickness

The basic principle of vacuum evaporation deposition was introduced, the factors that influence the coating thickness in the process of evaporation coating has carried out by theoretical calculation and experimental analysis, and the influence law of film thickness was found out.

Preparation and Study of SnO2 MOM Structure by The Thermal Vacuum Evaporation Deposition

Resistive switching random access memory is one of the novel nonvolatile memory technologies that, has a promising future for replacing the conventional FLASH memory. In this work a detailed study made about the types of operations and understanding the mechanisms of the resistance changing in the device.SnO 2 thin films are deposited by using Thermal Vacuum Evaporation deposition method at room temperature on Al/glass substrate to produce Al/SnO 2 /Al/glass device structure. Optical properties are taken to measure the optical band gap of SnO 2 . Resistive switching is observed by taking current voltage readings at room temperature. RRAM cell showed unipolar resistive switching behavior with no overlapping between reset and set voltage (1.5V, 2.5V respectively) ,also between high and low resistance states (7.7KΩ,106Ω). Good retention and endurance are obtained and the ratio between HRS to LRS has been found to be at least (41) within 21 cycles. تحضير ودراسة التركيب MOM لـ SnO2 باستخدام ترسيب التفريغ الحراري عمر غانم غزال أ.م.د. لقمان سفر علي كلية الهندسة / قسم الهندسة الكهربائية الخلاصة الذاكرة العشوائية المعتمدة على التغير في المقاومة هي احدى التقنيات الحديثة للذاكرة غير المتطايرة ولها مستقبل واعد في قدرتها على استبدال الذاكرة الحالية المستخدمة نوع فلاش. في هذا البحث تمت الدراسة بشكل مفصل لأنواع هذه الذاكرة حسب طريقة عملها وكذلك ألية الخلية والتغير الذي يطرأ عليها عند تغير قيمة مقاومتها.تم ترسيب SnO 2 بطريقة التبخير الحراري في درجة حرارة الغرفة وعلى سطح مكون من Al/glass وكذلك الطبقة العليا كانت المنيوم. وقد اخذت قياسات الخصائص الضوئية لسطح SnO2 لقياس فجوة الطاقة. التغير في المقاومة تم ملاحظته عند اخذ قياسات التيار مع الفولتيه في درجة حرارة الغرفة. وقد اظهرت خلية الذاكرة تغير في المقاومة نوع احادي الفولتية مع عدم وجود تداخل بين فولتيات العمل(reset, set)بما يقارب (1.5V,2.5V)كذلك كانت قيمة المقاومة العليا والدنيا (106Ω , 7.7 KΩ). وقد اظهرت هذه الذاكرة المصنع تكرارا بحدود (21) دورة وديمومة للمعلومة مع نسبة للمقاومة العليا الى والمقاومة الدنيا وبأسوء الظروف بحدود (41) .

TiO2 and Al2O3 nanoporous oxide layers decorated with silver nanoparticles—active substrates for SERS measurements

Self-organized nanoporous oxide layers (TiO2, Al2O3) exhibiting specific properties, obtained by anodic oxidation at a constant voltage in neutral electrolyte, may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as a stable platform for detecting various organic compounds. This paper presents the influence of the size of the nanotubes/nanopores and the structure of the porous oxide layers on the SERS enhancement factor, E F. We used pyridine and mercaptobenzoic acid as probe molecules, since they have a large cross-section for Raman scattering. To characterize the morphology and structure of the oxide layer substrates, before and after vacuum vapor deposition of silver nanoparticles, we applied scanning electron microscopy, X-ray diffraction and surface analytical techniques: AES, XPS and SERS. The results obtained show that for the same amount of Ag (0.02 mg/cm2) the size of the nanopores significantly affects the E F, which reaches, at a properly chosen nanopore size, distinctly higher values than that characteristic of a standard silver surface roughened by electrochemical cycling, i.e. E F > 106. The new Ag/MeO x –NT composites layer, ensure a good reproducibility of the SERS measurements and exhibit stability over a limited period of time.

Electron injection at the PTCDA/metal interface detected by electron paramagnetic resonance

Electron paramagnetic resonance absorption was observed for samples prepared by vacuum vapor deposition of thin films of 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) on metal films of magnesium (Mg), aluminum (Al) and silver (Ag) but not on gold (Au) or PTCDA on quartz. The resonance absorption is seen as a Lorentzian line with g-value of 2.0030 and a linewidth of 0.19mT. The signal is attributed to PTCDA anions at the metal organic interface. The relative values of the metal work function and the PTCDA electron affinity appear to determine the occurrence of the EPR absorption.

Tin doping effect on crystallization of amorphous silicon obtained by vapor deposition in vacuum

Tin doping effect on crystallization of amorphous silicon obtained by vapor deposition in vacuum

Impact of annealing process on stacking orientations and second order nonlinear optical properties of metallophthalocyanine thin films and nanostructures

The paper presents the second order nonlinear optical properties of Cu, Co, Mg and Zn metallophtalocyanines thin films. The films were fabricated by physical vapor deposition in high vacuum onto fused silica glass substrates. In order to investigate both optical and structural properties an annealing process in an ambient atmosphere for 12 h at temperatures equal to either 150 °C or 250 °C applied after the fabrication process. Atomic force microscopy images were obtained for an observation of the structural property changes. The thickness of the thin films was in the range from 80 nm to 120 nm. The size and shape of the forming nanostructures were different for different metallophthalocyanines and depended on the phase of the material. As-deposited sample of copper phthalocyanine formed the smallest nanostructures – standing columns with 100 nm of the height and 40 nm of the diameter. Annealed sample formed the largest nanostructures – lying cuboids with dimensions: 10 × 1000 × 40 nm. The second harmonic generation measurements have been carried out in order to investigate the second order nonlinear optical properties and their dependence on the structure of the thin films after the annealing process. Moreover the fittings based on the two models have been carried out in order to understand deeper the origin of the experimental findings. It was found that the annealing process can significantly modify both the structural and the second order nonlinear optical properties of the metallophthalocyanine thin films.

Structural and nonlinear optical properties of as-grown and annealed metallophthalocyanine thin films

The paper presents the Third Harmonic Generation investigation of four metallophtalocyanine (MPc, M=Cu, Co, Mg and Zn) thin films. The investigated films were fabricated by Physical Vapor Deposition in high vacuum onto quartz substrates. MPc thin films were annealed after fabrication in ambient atmosphere for 12h at the temperature equal to 150°C or 250°C. The Third Harmonic Generation spectra were measured to investigate the nonlinear optical properties and their dependence on the structure of the thin film after the annealing process. This approach allowed us to determine the electronic contribution of the third-order nonlinear optical susceptibility χ<3>elec of these MPc films and to investigate two theoretical models for explanation of the observed results. We find that the annealing process significantly changes the optical and structural properties of MPc thin films.

Chemical vapor deposition of ordered TiOx nanostructures on Au(111)

The deposition of TiOx (x≤2) structures on Au(111) by chemical vapor deposition (CVD) in ultrahigh vacuum (UHV) has been investigated with high-resolution core level photoelectron spectroscopy (PES), low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Using titanium tetra-isopropoxide as single source precursor it is possible to form different TiOx phases on the surface after deposition: at low coverages, we observe large two-dimensional (2D) honeycomb-lattice Ti2O3 islands with a (2×2) registry with the substrate. Higher coverages are dominated by the formation of three-dimensional (3D) TiO2 structures. The TiO2 structures are atomically well ordered provided that the deposition temperature is high enough (500°C). The ordered structure exhibits a LEED pattern characteristic for a rectangular surface unit cell. By performing the deposition at different temperatures it is possible to tune the balance between the 2D and 3D phases: Growth at 500°C significantly favors the formation of 3D TiO2 islands as compared to growth at 200°C and 300°C.

Corrosion resistance and cytotoxicity of a MgF2 coating on biomedical Mg–1Ca alloy via vacuum evaporation deposition method

To reduce the biocorrosion rate and enhance the biocompatibility by surface modification, MgF2 coatings were prepared on Mg–1Ca alloy using vacuum evaporation deposition method. The average thickness of the coating was about 0.95 µm. The results of immersion test and electrochemical test indicated that the corrosion rate of Mg–1Ca alloy was effectively decreased after coating with MgF2. The MgF2 coating induced calcium phosphate deposition on Mg–1Ca alloy. After 72 h culture, MG63 cells and MC3T3‐E1 cells were well spread on the surface of the MgF2‐coated Mg–1Ca alloy, while few cells were observed on uncoated Mg–1Ca alloy samples. In summary, MgF2 coating showed beneficial effects on the corrosion resistance and thus improved cell response of the Mg–1Ca alloy effectively and should be a good surface modification method for other biomedical magnesium alloys. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Optical constants of diindenoperylene in the dependence of preparation temperature and pressure

We determine the optical constants, that is, refractive index n, extinction coefficient k, and absorption coefficient α, of diindenoperylene (DIP) films deposited by organic vapor phase deposition (OVPD®) on quartz glass at different substrate temperatures between 60°C and 140°C and chamber pressures between 0.08 and 1.10kPa. The corresponding optical properties of the OVPD-films are compared with those of DIP layers deposited by physical vapor deposition (PVD) in high vacuum (~10−5kPa) at substrate temperatures of 20°C–140°C. Measured transmission/reflection spectra are evaluated numerically by a dielectric function of a sum of Lorentz oscillators to reproduce the optical properties of the DIP films. The optical results are analyzed in relation to the morphological and structural properties of the DIP films investigated by scanning electron microscopy. The optical and structural properties of the PVD-DIP films show a weak dependence on substrate temperature. A similar temperature behavior is observed for OVPD-DIP films for the chamber pressure range of 0.08–0.18kPa. For these conditions, we found from the optical calculations in the spectral range 250–660nm that (i) n varies between 1.4 and 1.9, (ii) k increases from 0.02 to 0.6, and (iii) α varies between 3.0×105cm−1 and 5×104cm−1. These data allow satisfactory determinations of thin film thicknesses by optical methods. At OVPD chamber pressures higher than 0.18kPa, the growth of spongelike film structures is observed which induce large deviations from computed film thicknesses. Nevertheless, the high absorption coefficients in the visible spectral region make all the investigated DIP films suitable for application as absorber in organic solar cells.