Thermal Evaporation Of Silver Research Articles

Physical properties of Ag3SbS3 thin films for photovoltaic applications

Ag3SbS3 thin films have been prepared by heating multilayers of glass/Sb2S3/Ag at different temperatures. Thin film of Sb2S3 were deposited on glass substrates using chemical bath deposition technique. Thermal evaporation of silver followed by annealing at 300 and 350°C were carried out to synthetize Ag3SbS3 thin films. XRD spectra showed the formation of Ag3SbS3 thin films at 300 and 350 °C with a micro-strain and grain size of 1.8 x 10-3 and 21 nm, respectively. Electrical conductivity in the range of 10-4 – 10-5 (Ωcm)-1 and a band gap of 1.3 eV were obtained.

AgSbS2-xSex thin films: Structure, composition, morphology and photodetection properties

Photodetectors using silver antimony seleno-sulfide (AgSbS2-xSex) thin films were fabricated and their photo sensing properties in the visible range were evaluated. The thin films were synthesized by combining chemical bath deposition and thermal evaporation techniques. The Sb2S3 thin films were deposited using chemical bath deposition followed by thermal evaporation of silver, varying the thickness from 10 to 80 nm proceeded by selenization via dipping in Na2SeSO3. The thin films were fabricated as glass/Sb2S3/Ag/Se layers with different silver thickness heated at 350 °C for 30 min. X-ray diffraction results showed the cubic structure of AgSbS2-xSex films. Elemental analysis, chemical composition and morphological studies were done using various techniques. The optical absorption in the UV–vis-NIR region spectra of the films with varying Ag content illustrated a wide spectral range for photodetector studies. The bandgap values calculated using Tauc plot method indicated within 1.53–1.75 eV, suitable for photodetector application. The current-voltage studies in the dark and illumination revealed that all the samples were photosensitive in the visible region. Methodical analysis of photoresponse was done using LEDs of various wavelengths at bias voltage of 0.5 and 1 V. All the samples showed a stable and good cyclic photoresponse behavior in the wavelength region between 395–740 nm. Further, the extensive photodetector application of the material was demonstrated by measuring the photoresponse using UV–vis LEDs and different laser power densities. The sensitivity and responsivity factors were calculated. With increase in Ag content, the conductivity of the films was increased and so the photocurrent response. This work asserts the application of AgSbS2-xSex thin films as a photodetector which has been explored till date for its photovoltaic properties only.

Fabrication and Microelectronic Properties of Hybrid Organic–Inorganic (poly(9,9, dioctylfluorene)/p-Si) Heterojunction for Electronic Applications

We report on the microelectronic characteristics of a novel hybrid heterojunction device based on a solution processable semiconducting polymer poly(9,9-dioctylfluorenyl-2,7-diyl)- co-(N,N0-diphenyl)-N,N′di(p-butyl-oxy-pheyl)-1,4-diamino-benzene) (PFB) and p-type silicon (p-Si). The PFB/p-Si heterojunction is prepared by spin coating 20 mg/mL solution of PFB in chloroform on the precleaned polished surface of p-Si substrate. Thermal evaporation of silver (Ag) electrode on top of PFB completes the fabrication of the Ag (90 nm)/PFB (180 nm)/p-Si heterojunction device. Morphology of PFB thin film is studied by using an atomic force microscope (AFM) and scanning electron microscope (SEM), which reveals grains are randomly distributed with slightly different grain sizes and shapes. It leads the film to form nonuniformity and some roughness in its topography that results in limiting the current (I) flow across the film/interface with p-Si. Ultraviolet (UV–vis) absorption and X-ray diffraction (XRD) spectra are measured for optical bandgap and crystal structure analysis of PFB. The key microelectronic parameters—rectification ratio (RR), ideality factor (n), barrier height (Φb), series resistance (Rs) and reverse saturation current (I0)—of the Ag/PFB/p-Si heterojunction are found from current–voltage (I–V) characteristics at room temperature (300 K) in dark conditions (≈0 lux). The Ag/PFB/p-Si heterojunction device exhibits improved microelectronic parameters when compared to those of earlier reported devices that were prepared in the same configuration. This improvement in the device parameters reveals enhancement in the microelectronic properties across the interface/depletion region of the Ag/PFB/p-Si device, which can be attributed to the remarkable electronic properties of PFB such as its relatively high hole mobility and better charge carriers’ conduction. The charge transport mechanisms through the device is also studied. Having the smaller values of I0 ≈ 7 × 10−10 A and n ≈ 3.23, as well as higher shunt resistance (Rsh) of 32 GΩ for the Ag/PFB/p-Si device suggest its potential for many electronic and optoelectronic applications.

Structural, optical, and electrical properties of silver gratings prepared by nanoimprint lithography of nanoparticle ink

A facile method for fabrication of silver gratings using silver nanoparticle ink and nanoimprint lithography is investigated. The properties of silver nanoparticle ink grating and planar samples, with and without a PMMA layer, are compared with thermally evaporated silver on nanoimprinted PMMA. The grating pattern is successfully fabricated using nanoimprint lithography with the silver nanoparticle ink directly on a glass substrate and on a PMMA layer. We find that the use of PMMA adversely affects the structural, optical and electrical properties of the silver nanoparticle planar surfaces and gratings. Gratings nanoimprinted directly into silver nanoparticle ink on a glass substrate are found to have similar performance to gratings produced by thermal evaporation of silver on nanoimprinted PMMA and benefit from an easier fabrication process. The silver nanoparticle ink shows promise for the fabrication of patterned silver thin films and may be useful for upscaling and roll-to-roll processes.

The Structural and Optical Properties of Silver Oxide Thin Films Synthesized by Thermal Evaporation of Silver with Subsequent Annealing

In this study, silver oxide thin films were deposited on silicon and glass substrates using thermal evaporation techniques with subsequent annealing in air. The deposited films were annealed in air at different temperatures. The effect of annealing temperature on the structural and optical properties of prepared thin films was investigated. The results showed that, except for the grain size, the annealing temperature has a significant effect on the oxidation rate and the optical properties of silver oxide thin films.

The role of graphene in enhancing electrical heating and mechanical performances of graphene−aligned silver nanowire hybrid transparent heaters

In this work, flexible and energy-efficient transparent heaters based on graphene and aligned silver nanowire (G–ASNW) hybrid structures are fabricated by thermal evaporation of silver on the aligned electrospun nanofiber templates and subsequent transfer of monolayer graphene onto the ASNWs. The G–ASNW films exhibit few wire-wire junctions and low resistance along the aligned direction, which are favorable for low-voltage transparent heater applications. Coating the ASNW network with monolayer graphene increases the saturated temperature of the hybrid heater due to the high thermal conductivity and low convective heat-transfer coefficient of graphene. Meanwhile, G–ASNW films show excellent electromechanical stability under cyclic bending because the graphene anchoring on the top surface of ASNWs could share tensile stress and serve as local conducting pathways at break-points even if small cracks were generated. The G–ASNW hybrid structures present a perspective on wearable transparent heaters.

Flexible transparent heaters based on silver nanotrough meshes

Flexible transparent heaters based on silver nanotrough mesh were prepared by thermal evaporation of silver on sacrificial nanofiber templates fabricated by electrospinning. Due to the specific preparation process, the heaters have many advantages like large area uniformity, low resistance, high transparency, mechanical flexibility and strong adhesion to substrates. A rapid and effective heating (rising from 25 °C to 100 °C in 50 s) is obtained at a DC input of 7 V with a visible light transmittance as high as 87%, which results in a relatively high figure of merit for transparent heaters. Therefore, silver nanotrough mesh can be a promising candidate for transparent heating applications.

Generation of Charged Nanoparticles During Thermal Evaporation of Silver at Atmospheric Pressure.

The generation of charged silver nanoparticles in the gas phase during thermal evaporation of silver at atmospheric pressure was confirmed by the nano-differential mobility analyzer (DMA). Effects of the evaporation temperature, the nitrogen gas flow rate and the amount of silver to be evaporated on the size distribution of charged nanoparticles (CNPs) were examined. Both positively and negatively-charged nanoparticles were generated under all processing conditions adopted in this study. The deposition behavior of CNPs was affected by the gas flow, which is affected by the temperature gradient in the reactor and by the applied electric bias. The electric bias, which not only enhanced the film growth rate but also produced a much denser film surface, turned out to be an important process parameter under the condition where an appreciable amount of CNPs is generated.

Selective deposition on block copolymer film by thermal evaporation of silver

Selective deposition of Ag onto nanostructured block copolymer film template of poly(ethylene oxide) and poly(methacrylate) with azobenzene mesogen (PEO-b-PMA(Az)) has been done by thermal evaporation technique. A hexagonally arranged pattern or ordered strip structure of the PEO nanocylinders dispersed in the PMA(Az) matrix appears on the pure copolymer film surface after thermal annealing at 140°C or 110°C, respectively. Atomic force microscopy confirms that the deposited Ag atoms prefer to wet PMA(Az) matrix domains on the film surface, and finally aggregate into discrete nanoparticles in both cases. An ordered porous metallic layer is created on the hexagonally patterned copolymer template surface due to the preferential interaction of Ag toward the PMA(Az) phase. Alternatively, ordered array of metallic chains is formed on the template featured with strip structure. While the nominal layer thickness of the deposited Ag is 50nm, the ordered metallic nanostructure disappears, indicating the host copolymer template cannot guide the spatial distribution of the deposited metal any more.

Highly Transparent and Conductive ZTO/Ag/ZTO Multilayer Top Electrodes for Large Area Organic Solar Cells

Transparent multilayer electrodes prepared by rf sputtering of zinc tin oxide (ZTO) and thermal evaporation of silver (Ag) as contact for organic electronics are reported. This multilayer has similar optical properties in the VIS range compared with ITO, though a significantly higher conductivity. Specifically we study the electrical and optical properties of the novel multilayer electrode and use it as bottom and top contact for semitransparent bulk hetero junction (BHJ) [poly(3-hexylthiophene): (6,6)-phenyl C61 butyric acid methyl ester] solar cells with an inverted device architecture.

Silver-Rutile UV Sensor Fabricated on Thermally Oxidized Titanium Foil <sup></sup>

A UV-sensitive Schottky diode of Ag-rutile-Ti structure is fabricated on a thermally oxidized titanium chip. The junction is formed by the thermal evaporation of silver in vacuum and a subsequent controlled annealing process. Applying a biasing voltage of-300 mV, the reverse current of the fabricated silver-rutile-titanium structure increases five orders of magnitude under 50 µW/mm2 UV illumination ( λ=355 nm). The device is visible-blind and its operation is described based on the photoelectric mechanism in the carrier-depleted oxide layer. The dominance of the photoelectric, rather than photoconductive, mechanism along with the dense rutile layer are responsible for the fast transient times observed. The response and recovery times of the device are 800 µs and 7 ms, respectively.The device is stable and extremely cost effective.

Efficient large area semitransparent organic solar cells based on highly transparent and conductive ZTO/Ag/ZTO multilayer top electrodes

We present transparent multilayer electrodes prepared by RF sputtering of zinc tin oxide (ZTO) and thermal evaporation of silver (Ag) as top contact for organic electronics. Specifically we study the electrical, optical and structural properties of the ZTO/Ag/ZTO (ZAZ) electrode. In the first step, we analyze the origin of high conductivity and high transparency by studying structural, electrical and optical properties of ultra thin Ag films. Secondly, we demonstrate that continuous and highly conductive Ag films can be deposited down to a thickness of 6 nm on top of ZTO. Furthermore we show, that owing to the stabilizing effect of the sputtered ZTO cap, ZAZ is substantially more robust than ZTO/Ag (ZA). As a first result we achieve a low sheet resistance of 5 Ω/sq and a transmissivity of 82% in the visible region of light. These values are compared to common transparent and semitransparent electrode materials deposited at room temperature like indium tin oxide (ITO). As an application we realized an optimized ZAZ structure as highly conductive and transparent top contact for large area semitransparent bulk hetero junction (BHJ) polymer solar cells (OSC) with an inverted device architecture. To expose the outstanding properties of the novel multilayer electrode we compare semitransparent OSCs using common ITO and ZAZ as top electrode cells with a large cell area >2 cm 2.

Fabrication of Functional Silver Nanobowl Arrays via Sphere Lithography

We report a low-cost and high-throughput method to fabricate large-area silver nanobowl arrays via thermal evaporation of silver on a self-assembled monolayer of nanospheres. The nanobowl array is a hierarchical structure, composed of silver nanoparticles with average diameter size of ca.10 nm, which can serve as a reaction container and catalyst. The optical absorption spectra indicates that surface plasmon resonance of silver nanoparticles exists on the nanobowl array, and it can serve as an excellent surface enhanced Raman scattering (SERS)-active substrate.

Spontaneous generation of charged atoms or clusters during thermal evaporation of silver

Abstract Spontaneous generation of charged atoms or clusters was investigated during thermal evaporation of silver. For this, the effect of the applied electric bias on the film growth rate was examined during evaporation of silver at 1373 K in a tungsten basket. Film growth rates on three silicon substrates biased + 300, 0 and −300 V with respect to the chamber were 300, 420 and 960 nm per hour, respectively. The number density of generated positively-charged atoms or clusters could be measured by the electric current on the Faraday cup in the chamber. From the temperature dependence of the positive current, the activation energy for charging was determined to be ∼ 2.2 eV. This value could be best explained by the surface ionization of clusters of a few atoms on the oxidized tungsten surface.

Optical Spectra of Metal-Dielectric Nanocomposites with a Layered Subwave Structure

The results of theoretical and experimental investigations of the optical spectra of layer-periodic nanocomposites consisting of alternating tightly packed monolayers of silver nanoparticles and separating KCl layers of subwave thickness are presented. The characteristic features of the spectral dependence of the transmission and reflection coefficients of this type of nanocomposites have been analyzed for the case where the photon forbidden bands are located near the plasmon-absorption band. Experimental samples were prepared by successive thermal evaporation of silver and KCl in vacuum. Theoretical calculations were carried out using the quasi-crystalline approximation of the theory of multiple scattering of waves. It is shown that the spectral position, shape, and intensity of absorption and reflection bands can be regulated by changing the optical thickness of the intermediate dielectric films in a layered metal-dielectric composite.

Changes of the optical properties of plasma polymer silver composite films caused by laser-annealing

Plasma polymer-silver composite films were deposited by simultaneous plasma polymerization of hexamethyldisilazane as well as benzene, and thermal evaporation of silver. The particle distribution of the silver particles in the insulating matrix was determined by transmission electron microscopy investigations. The changes of particle size and particle shape caused by laser annealing were investigated by image processing. The optical properties in UV/VIS/NIR were measured by transmission spectroscopy before and after laser annealing. Changes of the optical properties were modelled with effective medium theories concerning the changes of the microstructure.