Thin Films Research Papers - Academia.edu (original) (raw)

Slot die coating is growing in popularity because it is a low operational cost and easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste. The complex inner geometry of conventional slot dies require expensive machining that limits accessibility and experimentation. In order to overcome these issues this study follows an open hardware approach, which uses an open source 3-D printer to both fabricate the slot die and then to functionalize a 3-D slot die printing system. Polymer materials are tested and selected for compatibility with common solvents and used to fabricate a custom slot die head. This slot die is then integrated into a 3-D printer augmented with a syringe pump to form an additive manufacturing platform for thin film semiconductor devices. The full design of the slot die system is disclosed here using an open source license including software and operational protocols. This study demonstrates that functional lab-grade slot dies may be 3-D printed using low-cost open source hardware methods. A case study using NiO2 found an RMS value 0.486 nm, thickness of 17 to 49nm, and a maximum optical transmission of 99.1%, which shows this additive manufacturing approach to slot die depositions as well of fabrication is capable of producing viable layers of advanced electronic materials. Using this method, a cost savings of over 17,000% was obtained when compared to commercial slot die systems for laboratories.

This paper provides a review of the most recent works in electronic noses used in the food industry. Focus is placed on the applications within food quality monitoring that is, meat, milk, ﬁsh, tea, coffee and wines. This paper demonstrates that there is a strong commonality between the different application area in terms of the sensors used and the data processing algorithms applied. Further, this paper provides a critical outlook on the developments needed in this ﬁeld for transitioning from research platforms to industrial instruments applied in real contexts.

- by Ganesh Kumar Mani
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- Meat Science, Thin Films, Food Quality and Safety, E-Nose

Recent advances in the use of plasmonic metamaterials to improve absorption of light in thin-film solar photovoltaic devices has created a demand for a scalable method of patterning large areas with metal nanostructures deposited in an ordered array. This article describes two methods of fabricating ordered 2D nanosphere colloidal films: spin coating and interface coating. The two methods are compared and parameter optimization discussed. The study reveals that: For smaller nanosphere sizes, spin coating is more favorable, while for larger nanospheres, the angled interface coating provides more coverage and uniformity. A surfactant-free approach for interface coating is developed to fabricate zero-contamination colloidal films. Each of the methods reaches an overall coverage of more than 90% and can be used for nanosphere lithography to form plasmonic metamaterials.

- by Joshua Pearce
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- Materials Engineering, Physics, Materials Science, Photovoltaics
- by HwanYeol Park
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- Thin Films, Atomic Layer Deposition (ALD)

Novel aluminum and indium doped zinc oxide bilayer transparent conducting oxide thin films have been developed by simple sol gel spin coating and annealed at 500 C for an hour under nitrogen ambient towards solar cell applications. The structural, electrical and optical properties of both the as deposited and annealed bilayer thin films are characterized. X-ray diffraction studies showed a hexagonal wurtzite-type structure of ZnO with (002) orientation, which was enhanced with annealing. In atomic force microscopy studies minimum surface roughness is attained for the Al-doped ZnO/In-doped ZnO bilayer TCO films. The best Al-doped ZnO/In-doped ZnO films had sheet resistance of 0.057 M ohm/square and the films had an average transmittance in the visible region over 90%. Further results are discussed with single and bilayer structure.

A novel and simple chemical method based on sol-gel processing was proposed to deposit metastable orthorhombic tin oxide (SnOx) thin films on glass substrates at room temperature. The resultant samples are labeled according to the solvents used: ethanol (SnO-EtOH), isopropanol (SnO-IPA) and methanol (SnO-MeOH). The variations in the structural, morphological and optical properties of the thin films deposited using different solvents were characterized by X-ray diffraction, atomic force microscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence (PL) analysis. The XRD patterns confirm that all the films, irrespective of the solvents used for preparation, were polycrystalline in nature and contained a mixed phases of tin (II) oxide and tin (IV) oxide in a metastable orthorhombic crystal structure. FTIR spectra confirmed the presence of Sn=O and Sn-O in all of the samples. PL spectra showed a violet emission band centered at 380 nm (3.25 eV) for all of the solvents. The UV-vis spectra indicated a maximum absorption band shown at 332 nm and the highest average transmittance around 97% was observed for the SnO-IPA and SnO-MeOH thin film samples. The AFM results show variations in the grain size with solvent. The structural and optical properties of the SnO thin films indicate that this method of fabricating tin oxide is promising and that future work is warranted to analyze the electrical properties of the films in order to determine the viability of these films for various transparent conducting oxide applications.

- by Joshua Pearce
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- Materials Engineering, Materials Science, Photovoltaics, Thin Films and Coatings
- by Bruce Weiller
- •
- Chemistry, Thin Films, Sensors, Nanostructures

The agglomeration/dewetting process of thin silver films provides a scalable method of obtaining self-assembled nanoparticles (SANPs) for plasmonics based thin-film solar photovoltaic (PV) devices. Here, we show the effect of annealing ambiance on silver SANP average size, particle/cluster finite shape, substrate area coverage/particle distribution and how these physical parameters influence optical properties and surface-enhanced Raman scattering (SERS) responses of SANPs. Statistical analysis performed indicates that generally Ag SANPs processed in the presence of a gas (Argon and Nitrogen) ambiance tend to have smaller average size particles compared to those processed under vacuum. Optical properties are observed to be highly dependent on particle size, separation distance as well as finite shape. The greatest SERS enhancement was observed for the argon processed samples. There is a correlation between simulation and experimental data that indicate argon processed AgNPs have a great potential to enhance light coupling when integrated to thin-film PV. 1 Introduction As-deposited thin metallic films are generally metastable or unstable and readily de-wet from a solid substrate when heated even well below their melting temperature 1-2. The process of agglomeration/de-wetting proceeds in two ways: nucleation and growth of holes, and spinodal dewetting 1, 3-5. This process is a relatively economical means of obtaining both simple and complex nano-structures from thin metal films 5-10 compared to traditional methods such as e-beam lithography. Whilst dewetting during film processing has been reported to have undesirable effects on micro-and nano-systems, agglomeration has become the method of choice for catalyzed growth of nanotubes/nanowires and electronic and photonic devices 3. Dewetting of thin metallic films (both liquid and solid) to obtain mono/multi-dispersed nanoparticles has been demonstrated with a range of metals including: gold (Au), silver (Ag), nickel (Ni), copper (Cu) and alumina (Al), among others 1, 3-4, 10-1. However, Ag film dewetting has been mostly investigated as candidate for plasmonic sensing 12-18 and plasmonics-enhanced solar photovoltaics (PV) devices 19-31 applications. This is because Ag is generally considered to have the most suitable optical properties for solar cell applications. Silver nanoparticles exhibit highly intense and localized surface plasmon resonances (LSPR) and low absorption in the visible and near

- by Joshua Pearce and +2
- •
- Photovoltaics, Synthesis of nanoparticles, Nanomaterials Characterization, Thin Films and Coatings
- by F. Massines and +1
- •
- Thin Films

High-entropy alloys (HEAs) with multiple principal elements open up a practically infinite space for designing novel materials. Probing this huge material universe requires the use of combinatorial and high-throughput synthesis and processing methods. Here, we present and discuss four different combinatorial experimental methods that have been used to accelerate the development of novel HEAs, namely, rapid alloy prototyping, diffusion-multiples, laser additive manufacturing, and combinatorial co-deposition of thin-film materials libraries. While the first three approaches are bulk methods which allow for downstream processing and microstructure adaptation, the latter technique is a thin-film method capable of efficiently synthesizing wider ranges of composition and using high-throughput measurement techniques to characterize their structure and properties. Additional coupling of these high-throughput experimental methodologies with theoretical guidance regarding specific target features such as phase (meta)stability allows for effective screening of novel HEAs with beneficial property profiles.

- by Murat Pırıldar
- •
- Thin Films

New types of thin film solar cells made from
earth-abundant, non-toxic materials and with adequate
physical properties such as band-gap energy, large absorption coefficient and p-type conductivity are needed in
order to replace the current technology based on
CuInGaSe2 and CdTe absorber materials, which contain
scarce and toxic elements. One promising candidate absorber material is tin monosulfide (SnS). The constituent
elements of the SnS film are abundant in the earth’s crust,
and non-toxic. If this compound is used as the absorber
layer in solar cells, high efficient devices should be fabricated with relative low cost technologies. Despite these
properties, low efficiency SnS-based solar cells have been
reported up to now. In this work, we present a review about
the state of the art of SnS films and devices. Finally, an
analysis about different factors that are limiting high efficiency solar cells is presented.

- by Maykel Courel Piedrahita and +1
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- Renewable Energy, Thin film solar cells, Solar Cells, SnS
- by Ali Farhat
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- Analytical Chemistry, Stable Isotope Analysis, Paleoclimatology, Mass Spectrometry

Significant progress has been made recently in the fabrication of polymeric nanofibers, their characterization and applications, new polymeric materials, theoretical analysis, and so forth. Hence, in this brief review, we report the progress made in these subjects during the last 5 years. Most of the work concerns nanofibers related to the field of medicine. On the other hand, negligibly few reports have been found on nanofibers related to membrane separation processes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

- by Chaoyang Feng
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- Engineering, Membranes, Electrospinning, Thin Films

Nickel doped zinc oxide (Ni/ZnO) nanostructures have the potential to improve the performance of electrochemical capacitors. This study investigates the preparation of Ni/ZnO nanomaterials by facile co-precipitation (CPM) and hydrothermal (HTM) methods. The effect of the synthesis methods on the optical, structural, chemical and morphological properties on ZnO products is investigated using ultra violet (UV)-visible spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray spectrometry (EDX), room temperature photoluminescence (PL), Fourier transform infrared (FTIR) and Raman spectroscopy. Finally, the electrochemical performance of the synthesized nanorods were examined by fabrication of a supercapacitor using standard three electrode cell configuration and tested with a cyclic voltammogram (CV) and galvanostatic charge-discharge (GCD) measurements. The results shown that the samples synthesized by HTM exhibited improved electrochemical capacitance performance with higher current density. The discharge curves are linear in the total range of potential with constant slopes, showing perfect capacitance. In conclusion, Ni/ZnO nanoparticles synthesized by this method with further optimization have the potential to lead to a high-efficiency supercapacitors.

- by Joshua Pearce and +1
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- Materials Engineering, Materials Science, Chemistry, Thin Films and Coatings

A new method of preparing highly conductive ultra-thin indium tin oxide for plasmonic-enhanced thin film solar photovoltaic devices. Abstract Recent numerical modeling of plasmonic metallic nanostructures have shown great potential as a method of light management in thin-film nanodisc-patterned hydrogenated amorphous silicon (a-Si:H) solar photovoltaic (PV) cells. A significant design challenge for such plasmonic-enhanced PV devices is the requirement for ultra-thin transparent conducting oxides (TCOs) with high transmittance (low loss) and low enough resistivity to be used as device top contacts/electrodes. Most work on TCOs is on relatively thick layers and the few reported cases of thin TCO showed a marked decrease in conductivity. Recent work on ultra-thin TCOs of aluminum-doped zinc oxide, indium-doped tin oxide and zinc oxide revealed an unavoidable trade-off between transmittance and resistivity when fabricated with conventional growth methods. Ultra-thin films showed a tendency to be either amorphous and continuous or form as isolated islands. This results in poor electrical properties, which cannot be improved with annealing as the delicate thin films nucleate to form grain clusters. In order to overcome this challenge, this study investigates a novel method of producing ultra-thin (<40 nm) high quality TCOs. First, ~80nm ITO films are sputtered in various argon-oxygen atmospheres and annealed to increase conductivity. The most promising materials were then reduced in thickness with a controlled low-cost room-temperature cyclic wet chemical etching process to reach the desired thickness. The degradation in the electrical conductivity was tracked as a function of thickness. The sheet resistance of 36nm thin films was observed to be of the same order compared to the much thicker commercial ITO films currently used as transparent electrodes in PV and other opto-electronic devices. Experimental optical properties of the shaved films were then used in an optimized model of nano-disc plasmonic a-Si:H solar cells. Simulations indicate that optical enhancement greater than 21% are possible in the 300 – 730 nm wavelength range, when compared to the reference cell. Using the novel chemical shaving method described here, high-quality ultra-thin ITO films capable of improving the efficiency of thin film a-Si:H solar cells have been demonstrated. The methods employed in the optimization process are well established and economically viable, which provide the technical potential for commercialization of plasmonic based solar cells. A new method of preparing highly conductive ultra-thin indium tin oxide for plasmonic-enhanced thin film solar photovoltaic devices.

- by Joshua Pearce and +2
- •
- Materials Engineering, Materials Science, Photovoltaics, Thin Films and Coatings

Nanometer-sized structures, surfaces and sub-surface phenomena have played an enormous role in science and technological applications and represent a driving-force of current interdisciplinary science. Recent developments include the atomic-scale characterization of nanoparticles, molecular reactions at surfaces, magnetism at
the atomic scale, photoelectric characterization of nanostructures as well as two-dimensional solids. Research and development of smart nanostructured materials governed by their surface properties is a rapidly growing field. The main challenge is to develop an accurate and robust electronic structure description. The density of surface-related trap states is analyzed by transient UV photoconductivity and temperature-dependent admittance spectroscopy. An advanced application of thin films on shaped substrates is the deposition of catalytic layers on hollow glass microspheres for hydrogen storage controlled exothermal hydrolytic release. Surface properties of
thin films including dissolution and corrosion, fouling resistance, and hydrophilicity/hydrophobicity are explored to improve materials response in biological environments and medicine. Trends in surface biofunctionalization routes based on vacuum techniques, together with advances in surface analysis of biomaterials, are discussed. Pioneering advances in the application of X-ray nanodiffraction of thin film cross-sections for characterizing nanostructure and local strain including in-situ experiments during nanoindentation are described. Precise measurements and control of plasma properties are important for fundamental investigations and the development of next generation plasma-based technologies. Critical control parameters are the flux and
energy distribution of incident ions at reactive surfaces; it is also crucial to control the dynamics of electrons initiating non-equilibrium chemical reactions. The most promising approach involves the exploitation of complementary advantages in direct measurements combined with specifically designed numerical simulations. Exciting new developments in vacuum science and technology have focused on forward-looking and next generation standards and sensors that take advantage of photonics based measurements. These measurements are inherently fast, frequency based, easily transferrable to sensors based on photonics and hold promise of being disruptive and transformative. Realization of Pascal, the SI unit for pressure, a cold-atom trap based ultra-high
and extreme high vacuum (UHV and XHV) standard, dynamic pressure measurements and a photonic based thermometer are three key examples that are presented.

- by Jacobo Hernandez-Montelongo
- •
- Surface Science, Biomaterials, Surface Engineering, Thin Films

Micromorphology analysis of sputtered indium tin oxide fabricated with variable ambient combinations. Abstract This study experimentally investigates the fractal nature of the 3-D surface morphology of sputtered indium tin oxide (ITO) fabricated with five sets of ambient combinations. The samples were prepared on glass substrates by DC magnetron sputtering using argon, argon with oxygen, argon with oxygen and nitrogen, argon with oxygen and hydrogen and argon with oxygen, nitrogen and hydrogen ambient compositions at room temperature and the films were annealed at 450 °C in air. The characterization of the films surfaces was carried out by X-ray diffraction (XRD), and atomic force microscopy (AFM). The XRD results indicate that the cubic ITO films form with highly preferable (222) and (400) orientations. The AFM images were analyzed using the Areal Autocorrelation Function (AACF) and pseudo-topothesy K. This analysis revealed that these samples are well described as fractal structures at nanometer scale.

- by Joshua Pearce and +1
- •
- Photovoltaics, Thin Films and Coatings, Morphology, Photovoltaic Materials
- by Vikram Reddy Vangala
- •
- Engineering, Electronics, Semiconductors, Advanced Materials

The human hearing range is from 20 Hz to 20 kHz. However, many animals can hear much higher sound frequencies. Dolphins, especially, have a hearing range up to 300 kHz. To our knowledge, there is no data of a reported wide-band sound frequency earphone to satisfy both humans and animals. Here, we show that graphene earphones, packaged into commercial earphone casings can play sounds ranging from 100 Hz to 50 kHz. By using a one-step laser scribing technology, wafer-scale flexible graphene earphones can be obtained in 25 min. Compared with a normal commercial earphone, the graphene earphone has a wider frequency response (100 Hz to 50 kHz) and a three times lower fluctuation (±10 dB). A nonlinear effect exists in the graphene-generated sound frequency spectrum. This effect could be explained by the DC bias added to the input sine waves which may induce higher harmonics. Our numerical calculations show that the sound frequency emitted by graphene could reach up to 1 MHz. In addition, we have demonstrated that a dog wearing a graphene earphone could also be trained and controlled by 35 kHz sound waves. Our results show that graphene could be widely used to produce earphones for both humans and animals.

- by Kentaro Ito
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- Multidisciplinary, Thin Films, Copper, Annealing
- by Teodor Todorov
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- Engineering, Solar Cell, Nanoparticles, Advanced Materials
- by Shekhar Prajapati
- •
- Thermal Spray Coating, Gas Sensors, Thin Films, Uv-Vis Spectroscopy

This article provides an overview of the state-of-the-art chemistry and processing technologies for silicon nitride and silicon nitride-rich films, i.e., silicon nitride with C inclusion, both in hydrogenated (SiN x :H and SiN x :H(C)) and non-hydrogenated (SiN x and SiN x (C)) forms. The emphasis is on emerging trends and innovations in these SiN x material system technologies, with focus on Si and N source chemistries and thin film growth processes, including their primary effects on resulting film properties. It also illustrates that SiN x and its SiN x (C) derivative are the focus of an ever-growing research and manufacturing interest and that their potential usages are expanding into new technological areas.

Lithium-doped zinc oxide thin films (ZnO:Li) at different percentages (0–4%) were deposited on glass substrates at 460 °C using the spray pyrolysis technique. The effect of lithium content on the structural, morphological and optical properties of ZnO:Li thin films was investigated. First, X-ray diffraction study revealed that undoped and Li-doped ZnO thin films crystallize in hexagonal wurtzite structure with a preferred orientation of the crystallites along (002) direction. The scanning electron microscopy (SEM) showed a clear hexagonal-shaped granular onto the surface of such films. Indeed, the averaged grain size, visualized by SEM, varied from 100 nm, for undoped ZnO, to 200 nm for ZnO:Li 4%. Second, the optical analysis by means of the transmittance and the reflectance measurements revealed that in UV–Vis domain, the average trans-mittance of the ZnO:Li thin films was 75%, while the average reflectance was \35% in the visible range. Moreover, the band gap energy, E g , decreased from 3.285 to 3.264 eV as Li content increases. On the other hand, the photolumi-nescence spectra revealed emission with multiple peaks and exhibited especially two emission bands in UV and visible regions. Finally, the ZnO photodetectors showed superior performance in the view of photocurrent.

- by Mohamed Salah
- •
- Morphology, Doping, Thin Films, ZnO (Zinc Oxide)

Graphene is flexible and transparent with one-atom layer thickness, and is a novel building block with potential applications in future portable devices. Herein a flexible, transparent and ultrathin earphone based on single-layer graphene (SLG) is reported. The SLG earphone operates in the frequency range of 20 Hz to 200 kHz and has a highest sound pressure level (SPL) of 70 dB at a 1 cm distance. The SPLs emitted from one to six layers of stacked SLG are compared. It is observed that the SPL decreases with an increasing number of stacked layers. The SLG earphone, which is packaged with a commercial earphone casing, can play music clearly. Compared with a conventional earphone, the SLG earphone has a broader frequency response and a lower fluctuation. Testing results in both time and frequency domains show a frequency doubling effect, which indicates that the working principle is based on the electro-thermoacoustic (ETA) effect. As the SLG earphone operates in both the audible and ultrasonic frequency range, it can be used for a wide variety of applications.

- by Tian-ling Ren and +1
- •
- Electrical Engineering, Microelectronics And Semiconductor Engineering, Acoustic Engineering, Acoustics

Cu2ZnSnS4 (CZTS) thin films were grown onto glass substrates using pneumatic spray pyrolysis method under different growth conditions.The electrical properties have been investigated by means of dark and illuminated conductivity measurements in the 293–353 K temperature range and Hall measurements at
room temperature. The influence of growth parameters on the grain boundary barrier height and other associated grain boundary parameters of the CZTS thin films was determined from electrical, optical, and morphological characterization.The CZTS electrical properties relation with secondary phases formation as well as with transport mechanisms is presented. Finally, CZTS electrical parameters impact on the properties of polycrystalline thin film solar cells is discussed.

This chapter looks at the role of silicon carbide (SiC) in microsystem technology. It starts with an introduction into the wide bandgap (WBG) materials and the properties that make them potential candidates to enable the development of harsh environment microsystems. The future commercial success of WBG microsystems depends mainly on the availability of high-quality materials, well-established microfabrication processes, and economic viability. In such aspects SiC platform, in relation to other WBG materials, provides a clear and competitive advantage. The reasons for this will be detailed. Furthermore, the current status of the SiC thin film and bulk material technologies will also be discussed. Both SiC material forms have played important roles in different microsystem types.

- by Mariana Amorim Fraga
- •
- MEMS, Thin Films, Silicon Carbide, Bulk materials

We demonstrate a novel flexible and transparent earphone based on single-layer graphene (SLG) for the first time. The SLG earphone operates in the frequency range of 20 Hz to 200 kHz and has a highest sound pressure level (SPL) of 70 dB with a 1 W input power. The SPL emitted from one to six layers of stacked SLG are compared. It is observed that the SPL decreases with an increasing number of stacked layers. The SLG earphone is packaged into a commercial earphone casing and can play music. Compared with a conventional earphone, the SLG earphone has a broader frequency response and a lower fluctuation. Testing results in both time- and frequency-domains show a frequency doubling effect, which indicates that the working principle is based on the electro-thermoacoustic (ETA) effect. As the SLG earphone operates in both the audible and ultrasonic frequency range, it can be used for a wide variety of applications, including for interspecies communication.

- by Ganesh Kumar Mani
- •
- Thin Films, Ammonia Gas Sensors, Spray Pyrolysis, Room Temperature Sensor
- by Robert Keller
- •
- Materials Engineering, Mechanical Engineering, Microstructure, Image Analysis
- by Mohammad Najmzadeh
- •
- Electrical Engineering, Nanoelectronics, Raman Spectroscopy, Nanotechnology

Whether decorative, protective or functional, coatings must contend with water in the environment. A problem distinct from the issue of wet adhesion and hydrolytic stability of coatings is controlling the interaction of water with a coated surface. Very often the descriptors hydrophobic or hydrophilic are applied to coated surfaces. Although the terms hydrophobic and hydrophilic are casually used, they are usually not defined. A growing number of applications ranging from architectural coatings to aortic stents require precise control and, therefore, precise definition of substrate interaction with water. Silanes are playing an increasing role in controlling the interaction of water with a surface. Silanes are silicon chemicals that possess a hydrolytically sensitive center that can react with inorganic substrates such as glass to form stable covalent bonds and organic substitution that alters the physical interactions of treated substrates (Figure 1). Different than most additives, which have a limited performance range, they can achieve surface properties ranging from hydrophobic to hydrophilic. They may be a sole active ingredient or a component in a coatings formulation, controlling the interaction of water over a broad spectrum of requirements. In order to understand how silanes can affect hydrophobicity and hydrophilicity, it is important to understand some of the fundamentals of the interaction of water with surfaces.

- by Barry Arkles
- •
- Sol-Gel Technology, Thin Films, Surface Coatings, Wettability
- by Davide Barreca
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- Engineering, Technology, Thin Films, X Rays

The need for tighter control over film uniformity, conformality, and properties at decreasing thicknesses was met by a gradual evolution from physical vapor deposition (PVD), to chemical vapor deposition (CVD), and eventually atomic layer deposition (ALD) processes. Of all manufacturing-worthy thin-film deposition processes, ALD has the greatest potential to satisfy these requirements. However, the intrinsic constraints of recurrent two atom reactivity and associated byproducts have kindled tremendous interest in other self-limiting deposition processes such as Molecular Layer Deposition (MLD), Self-Assembled Monolayer (SAM), and “Click” Chemistry Deposition (CCD) processes, either as alternatives to or in conjunction with ALD. This overview provides definitions, illustrations and examples of these processes.

- by Somobrata Acharya
- •
- Engineering, Nanoparticles, Advanced Materials, Thin Films

The effect of substrate and annealing temperatures on the structural, morphological, optical and electrical properties of spray deposited copper oxide thin ﬁlms was investigated. The ﬁlms were deposited on glass substrates using 0.05 M of cupric acetate precursor at the substrate temperatures of 523, 623 and 723 K. From the structural, morphological and optical characteristics, the ﬁlm coated at 623 K was found to have better crystallinity with mixed cuprite and tenorite phases. Thus, substrate temperature was ﬁxed at 623 K and ﬁlms were prepared by increasing the molar concentration of cupric acetate to 0.1 M. Further the effect of annealing on the various properties of the CuO ﬁlms was investigated. The XRD patterns of the annealed ﬁlms at 523, 623 and 723 K for 6 h revealed the formation of copper oxide thin ﬁlms with tenorite phase.

- by Ganesh Kumar Mani
- •
- Nanomaterials, Nanotechnology, Thin Films, Temperature

Vanadium pentoxide (V2O5) thin films were deposited on glass substrates using spray pyrolysis technique. Aqueous solution of ammonium vanadate with 0.1 M concentration was used to deposit V2O5 thin films at different substrate temperatures. The structural, morphological, electrical, optical and vapour sensing properties of the films were investigated. XRD patterns confirmed the polycrystalline nature of the films with orthorhombic structure. Crystallite size was increased with an increase in the substrate temperature. SEM images showed the formation of films with flower like morphology. From the optical absorbance spectra, the optical band gap was determined and varied between 3.34 to 3.24 eV. The charge carrier concentration was found to be increased with substrate temperature. Room temperature xylene sensing characteristics of the films were investigated. The influence of substrate temperature on the vapour sensing characteristics of V2O5 is reported.

- by Shekhar Prajapati
- •
- Sensors and Sensing, Thin Films, Formaldehyde
- by sam zhang
- •
- Materials Engineering, Condensed Matter Physics, Thin Films, Thin Film
- by G. Sberveglieri
- •
- Engineering, Technology, Atomic Force Microscopy, Thin Films
- by Sankara Narayanan TSN
- •
- Corrosion, Thin Films, Mechanical properties, Coatings

Piezoelectric materials used in the development of nanoscale mechanical sensors, actuators and energy harvesters have received much attention. More recently, devices made of graphene are of particular interest because of graphene’s intriguing electronic and mechanical properties. Intrinsic graphene has long been considered devoid of the piezoelectric effect, although flexoelectricity has been exploited to demonstrate piezoelectricity in functionalized graphene and graphene nanoribbons. The perceived lack of this property has restricted graphene’s use in nanoelectromechanical systems (NEMS) for electromechanical coupling purposes. Here an unprecedented two-dimensional (2D) piezoelectric effect on a strained/unstrained graphene junction is reported. In stark contrast to the bulk piezoelectric effect that results from the occurrence of electric dipole moments in solids, the 2D piezoelectric effect arises from the charge transfer along a work function gradient introduced by the biaxial-strain-engineered band structure. The observed effect, termed the band-piezoelectric effect, exhibits an enormous magnitude due to the ultrathin structure of graphene. On the basis of the band-piezoelectric effect, a graphene nanogenerator and a pressure gauge were fabricated. The results not only provide a versatile NEMS platform for sensing, actuating and energy harvesting, but also pave the way for efficiently modulating graphene via strain engineering.

- by Mohammad Ali Mohammad and +1
- •
- Electrical Engineering, Physics, Materials Science, Chemistry

Au/graphene oxide (GO)-doped PrBaCoO nanoceramic/n-Si capacitors were fabricated and their admittance measurements were carried out between 1 kHz and 1 MHz at room temperature. Experimental results showed that the capacitance (C) and conductance (G/w) values are strong functions of frequency and applied bias voltage. C–V plot revealed two distinctive peaks at low frequencies which are located at about 0 and 2 V, such that the first peak disappears towards high frequencies. The energy density distribution profile of the interface/surface states (D it / N ss) and their relaxation time (s) and capture cross section (r p) of the sample were obtained by using the admittance method. In addition, the voltage-dependent profile of N ss and resistance were obtained by using low–high frequency capacitance and Nicollian-Brews method, respectively, and they also reveal two distinctive peaks, respectively. Two peaks' behavior in the forward bias C–V, N ss –V and R i –V plots confirmed the existence of two different localized regions of N ss between Si and interfacial layer. The series resistance (R s) of the device decreased with increasing frequency from 175 X at 1 kHz to 72 X at 1 MHz. As a result, the mean value of D it was found about 5 9 10 13 eV-1 cm-2 which is reasonable for an electronic device.

- by Martin Kordesch and +1
- •
- Materials Engineering, Condensed Matter Physics, Near Infrared, Thin Films

The opportunity for substantial efficiency enhancements of thin film hydrogenated amorphous silicon (a-Si:H) solar photovoltaic (PV) cells using plasmonic absorbers requires ultra-thin transparent conducting oxide top electrodes with low resistivity and high transmittances in the visible range of the electromagnetic spectrum. Fabricating ultra-thin indium tin oxide (ITO) films (sub-50 nm) using conventional methods has presented a number of challenges; however, a novel method involving chemical shaving of thicker (greater than 80 nm) RF sputter deposited high-quality ITO films has been demonstrated. This study investigates the effect of oxygen concentration on the etch rates of RF sputter deposited ITO films to provide a detailed understanding of the interaction of all critical experimental parameters to help create even thinner layers to allow for more finely tune plasmonic resonances. ITO films were deposited on silicon substrates with a 98-nm, thermally grown oxide using RF magnetron sputtering with oxygen concentrations of 0, 0.4 and 1.0 sccm and annealed at 300 °C air ambient. Then the films were etched using a combination of water and hydrochloric and nitric acids for 1, 3, 5 and 8 min at room temperature. In-between each etching process cycle, the films were characterized by X-ray diffraction, atomic force microscopy, Raman Spectroscopy, 4-point probe (electrical conductivity), and variable angle spectroscopic ellipsometry. All the films were polycrystalline in nature and highly oriented along the (222) reflection. Ultra-thin ITO films with record low resistivity values (as low as 5.83 × 10−4 Ω·cm) were obtained and high optical transparency is exhibited in the 300–1000 nm wavelength region for all the ITO films. The etch rate, preferred crystal lattice growth plane, d-spacing and lattice distortion were also observed to be highly dependent on the nature of growth environment for RF sputter deposited ITO films. The structural, electrical, and optical properties of the ITO films are discussed with respect to the oxygen ambient nature and etching time in detail to provide guidance for plasmonic enhanced a-Si:H solar PV cell fabrication.

- by Joshua Pearce and +2
- •
- Materials Engineering, Materials Science, Optics, Photovoltaics
- by Stefano Leporatti and +2
- •
- Engineering, Materials Chemistry, Membrane Science, Light Scattering