Keywords : Thin Film

Influence of Coating Thickness on the Formability of Annealed Aluminum 2024

Irfan Mahmood Khan; Kinza Tahreem; Junaid Iqbal; Zeeshan Mehmood Khan; Fatima Anjum; Abdul Mateen

Advanced Materials Letters, 2020, Volume 11, Issue 8, Pages 1-7
DOI: 10.5185/amlett.2020.081544

Sheet metal forming of uncoated Aluminum 2024 (Al-2024-TO) alloy was performed on conventional press with a movable punch. A set of four uncoated aluminum specimens (UCS) was formed after the application of silicone-based lubricant on the specimen surface facing punch. Variation in thickness of the specimens at different locations was one of the major concerns during forming operation which caused localized thinning and hardening of stock, resulting in a premature fracture (100 mm depth). Thin porous membranes were deposited on the specimens to enhance lubrication (by retaining the lubricant) and reduce friction between clamp and stock. Four sets of coated specimens (CS) with different film thicknesses (5 μm, 10 μm, 15 μm, and 20 μm) were anodized and formed to study the effect of coating thickness and lubricant entrapment on the formed depth. Characterization of coated specimens operation exhibited that the porous thin film with an optimum thickness of 10 μm (pore diameter of 60-68 nm) facilitated the maximum entrapment of lubricant in the pores. Enhanced lubrication for CS-2 resulted in the aggravated material flow which showed minimum hardness (60 HV), minimum thickness variation (2.82-2.90 mm), and minimum draw force (11 kN) with the maximum draw depth of 172 mm.

The Effect of Complexing Reagent on Structural, Electrical and Optical Properties of CuS Thin Film

A.V. Mitkari; A.U. Ubale

Advanced Materials Letters, 2020, Volume 11, Issue 1, Pages 1-5
DOI: 10.5185/amlett.2020.011465

Semiconducting CuS thin films were successfully prepared by Successive Ionic Layered Adsorption Reaction technique at room temperature with and without using complexing reagent viz.  hydrazine hydrate (H6N2O(N2H2),tri ethanol amine (C6H15NO3 ) and ammonia (NH3) . The structural studies revealed that; the crystallinity of the film can be tailored by using complexing agent. The dc electrical resistivity measured in the temperature range 370–473 K confirmed its semiconducting nature of CuS and it varies depending on complexing reagent. The optical absorption measurements were studied in the wavelength range 350–950 nm . The thermo-emf measurements confirmed that the films prepared are semiconducting in nature with p-type conductivity. 

Dual Effect of Light Irradiation for Surface Relief Gratings Formation in Se-rich Ge-Se Thin Films

Tyler Nichol; Janis Teteris; Mara Reinfelde; Maria Mitkova

Advanced Materials Letters, 2019, Volume 10, Issue 12, Pages 868-873
DOI: 10.5185/amlett.2019.0012

Relief surface formation as a result of light irradiation is one important property of chalcogenide glasses which gives rise of number of applications. Understanding the nature of the process is an essential step towards optimization of the relief images obtained. This work depicts the mechanisms for surface relief grating formation in Ge-Se thin films exposed to diffracted light. A dependence on the period of the illumination source is revealed, which correlates with the composition of the thin film material. Raman spectroscopy, Energy Dispersive Spectroscopy (EDS), and Atomic Force Microscopy (AFM) were used to analyze the films. The results point towards a dual effect of light irradiation leading to mass transport and structural changes, which results in a surface relief formation. Copyright © VBRI Press.

Room temperature growth of ultra porous hot-wire deposited tantalum pentoxide

Giorgos Papadimitropoulos; Maria Vasilopoulou; Nikos Vourdas; Dimitris N. Kouvatsos; Kostas Giannakopoulos; Stella Kennou; Dimitris Davazoglou

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 395-399
DOI: 10.5185/amlett.2019.2283

Tantalum pentoxide films were deposited on Si substrates at room temperature, by heating metallic filaments at temperatures below 600 o C, at a pressure of 1 Torr in O2 environment. This deposition method can be applied for all metallic oxides having higher vapor pressure than the corresponding metal. These (hwTa2O5) films were composed by amorphous material (as revealed by XRD measurements) and were found to be highly transparent within the range 350-1000 nm. Spectroscopic ellipsometry measurements have shown that the real part of the refractive index (n) of hwTa2O5 films depends on the deposition time and has a value below 1.5. As shown by scanning electron microscopy (TEM) measurements, these grains were composed by others with dimensions near 5 nm and with voids between them. The above microscopy measurements explain the high porosity of hwTa2O5 films. Moreover, hwTa2O5 films were also characterized by XPS and UPS measurements and the stoichiometric composition of the deposited films was determined.

Reducing edge effect of temperature-field for large area thin film deposition in hot filament chemical vapor deposition system

Lin Li; Shibing Tian; Ruhao Pan; Chao Wang; Chi Sun; Junjie Li; Changzhi Gu

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 727-732
DOI: 10.5185/amlett.2018.2146

The uniformity in temperature-field of the hot filament chemical vapor deposition (HFCVD) system is of great importance since it is a critical parameter that determines the quality of the deposited films. In fact, the temperature-field is mainly filament distribution dependent. In conventional analysis method, the filament array usually has an equal-space distribution, which leads to a remarkable edge effect and consequently unable to obtain large area uniformity in temperature-field in HFCVD for high-quality thin film deposition. Here, we proposed theoretically an asymmetrical filament distribution to reduce the edge-effect of temperature field. The adjacent filament distance was optimized by using numerical simulation based on heat-transfer theory. Based the optimized condition, temperature difference as low as 13 K between the center and edge region of the filament arrays can be achieved in 100-mm substrate, which is only one tenth of the temperature difference of that in the case that the filaments were evenly distributed. Thus unequal-space distribution can be employed to enhance the uniformity in temperature field of the HFVCD system in favor of the growth of high quality thin films in large area.

Enhancing absorption in thin film organometal trihalide perovskite solar cell by photon recycling

Abhinav Bhatnagar; Vijay Janyani

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 721-726
DOI: 10.5185/amlett.2018.2108

Over the past few years thin film planar heterojunctions solar cells have made much progress as a low cost with high power conversion efficiency photovoltaic devices. Among the materials used in fabricating such solar cells organometal trihalide perovskite (MAPbI3) has proven to be a promising absorber material due to cheaper organic-inorganic perovskite compounds, abundantly available in nature, ease of fabrication and compatible with low temperature large scale processing. In addition to the efficient absorption in ultra-violet range the material possess intriguing optoelectronic properties such as high crystallinity, high carrier mobility and large carrier diffusion lengths. Currently, the highest power conversion efficiency achieved by such perovskite solar cells is only 23.9% as reported in 2017. In this work we demonstrate a thin film organometal trihalide perovskite solar cell with hybrid interfaces between different materials which are selected after extensive study to achieve reduced recombination and high performance. Further, the absorption of the incident solar spectrum is enhanced by incorporating a 1D photonic crystal at the bottom of the cell facilitating the photon recycling process. The proposed solar cell parameters are numerically computed using rigorous coupled wave algorithm through SYNOPSYS RSOFT CAD tool. The thickness of each layer of the structure is optimized using MOST scanning and optimization module of RSOFT CAD tool to achieve highest power conversion efficiency at minimum device thickness (~2 µm). The power conversion efficiency thus obtained is 25.2% with a fill factor of 86.3% at AM 1.5, which is very promising. This demonstrates the remarkable potential of the proposed design to achieve efficiencies over 20% and compete with the existing crystalline silicon photovoltaic market. 

Fabrication and magnetic properties of Sol-Gel derived NiZn ferrite thin films for microwave applications

Shauna Robbennolt; Stephen S. Sasaki; Tylisia Wallace; Marquise Bartholomew; Sarah H. Tolbert

Advanced Materials Letters, 2018, Volume 9, Issue 5, Pages 345-352
DOI: 10.5185/amlett.2018.1996

We present a new solution-phase, sol-gel based spin-coating method to fabricating high quality, nickel zinc ferrite (NZFO) thin films. The effect of annealing temperature on the microstructure, static magnetic properties and X-band FMR linewidth and resonance field was investigated. Furthermore, the effect of composition on these properties was explored in films with the formula NixZn(1-x)Fe2O4 (where x = 0 to 1 in 0.1 increments). Films annealed at the highest annealing temperature of 1100 ?C were found to have the highest saturation magnetization and coercivity, as well as the lowest FMR linewidths. Films with the composition Ni0.3Zn0.7Fe2O4 were found to have the lowest linewidths along with favorable magnetic properties for microwave applications. The champion film showed an FMR linewidth of 93 G, corresponding to a low Gilbert damping coefficient of α = 0.003, a saturation magnetization of 330 emu/cm 3 , and a coercivity and anisotropy field of 14 and 62 Oe respectively.

Morphological and electrical characterization of Cu-doped PbS thin films with AFM

Illia Dobryden; Baligh Touati; Abdelaziz Gassoumi; Alberto Vomiero; Najoua Kamoun; Nils Almqvist

Advanced Materials Letters, 2017, Volume 8, Issue 11, Pages 1029-1037
DOI: 10.5185/amlett.2017.1545

Lead sulphide (PbS) is a direct band gap IV–VI intrinsic p-type semiconductor with good potential for application in solar cells, sensors, etc. Doping the films with Cu 2+ ions may improve the electrical properties. Here, Cu-doped PbS films were deposited on conducting glass substrates. The morphology, topography and thickness of the doped PbS films were examined using atomic force microscopy (AFM) and high-resolution SEM. AFM analysis showed decreasing surface roughness and grain size with the increase of Cu 2+ concentration from 0.5 to 2.0 at%. Local surface electrical measurements using conducting AFM and Kelvin probe force microscopy showed the possibility to probe semi-quantitatively the changes in surface potential, work function, and Fermi level upon doping of the films. The estimated apparent work function for the un-doped PbS grains in the film was slightly above 4.5 eV, while it decreased to a minimum value of 4.43-4.45 eV at 1–1.5 at% Cu-doping. Conducting AFM measurements showed that local resistance of the doped samples is lower than on pure PbS films. These results indicate Cu doping as an effective strategy to tune the electrical properties of PbS thin films toward the development of suitable optically active materials for application in photovoltaics. 

Stoichiometric dependent optical limiting in PLD SiOx thin films

Partha P. Dey; Alika Khare

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 331-335
DOI: 10.5185/amlett.2017.6931

In this letter, optical limiting property of the insufficiently oxidized silicon oxide (SiOx) thin films is reported. Films were deposited by Pulsed Laser Deposition technique using Q-switched Nd: YAG laser (532 nm) onto fused silica substrate at a substrate temperature of 400 °C by varying the O2 pressure in the range of 5×10 -5 to 0.5 mbar. Energy Dispersive X-Ray spectra showed the increase in oxygen content with increasing O2 pressure. Raman spectra of SiOx films depicted the presence of micron sized clusters composed of nanocrystalline Silicon embedded in uniform matrix of oxidized amorphous Silicon. The open Z-scan of the thin films, under cw He-Ne laser irradiation, showed strong reverse saturation absorption (RSA) features and non linear absorption (NLA) coefficient, β, was found to be decreasing from 23.5 cm/W to 1.64 cm/W,  with increase in O2 pressure from 5×10 -5 to 10 -1 mbar, respectively. Also, the SiOx films except that with maximum oxygen content showed optical limiting, where limiting threshold increases with increasing transparency controlled by oxygen content. The key feature of the present work is the tunability in linear absorption, nonlinear RSA and optical limiting in the SiOx films which can be used as novel material for optical switching application.

Characterization And Synthesis Of Bi2Se3 Topological Insulator Thin Film Using Thermal Evaporation

Bushra Irfan;Ratnamala Chatterjee

Advanced Materials Letters, 2016, Volume 7, Issue 11, Pages 886-890
DOI: 10.5185/amlett.2016.6208

Topological insulators are the new phase of matter with bulk insulating and conducting surface states. Among the known three dimensional topological insulators, bismuth selenide (Bi2Se3) is one of the most promising materials for studying topological insulating properties. Bi2Se3 thin films are grown using thermal evaporation technique and atomically smooth films are obtained by post annealing treatment. Pure phase of Bi2Se3 is confirmed using x-ray diffraction; Raman spectroscopy shows a strong intensity of A 1 1g, E 2 g and A 2 1g 2Se3 thin films. The surface studies on these films are carried out using scanning electron microscopy and atomic force microscopy. X-ray photoelectron spectroscopy (XPS) is used for elemental analyses in Bi2Se3 thin film. The surface quality of the film is improved with plasma etching (i.e. argon etching) in XPS. High quality Bi2Se3 thin films can be used further for investigation on transport properties of topological insulators.

Thickness Effect On Nano-multilayered Sb/As2S3 Chalcogenide Thin Films

Ramakanta Naik

Advanced Materials Letters, 2016, Volume 7, Issue 10, Pages 821-825
DOI: 10.5185/amlett.2016.6339

The nano multilayered thin films of Sb/As2S3 metal chalcogenide were prepared by thermal evaporation technique under high vacuum. The optical parameters such as optical band gap, tauc parameter, urbach energy were determined from the transmission spectra using Fourier Transform Infrared Spectroscopy. These properties are greatly influenced by the thickness of the nano layered Sb/As2S3 thin film. The Small Angle X-ray diffraction study reveals the amorphous nature of these films. The analysis reveals that the optical band gap decreases with increase in thickness due to Sb metal. The tauc parameter and urbach energy supports the optical property change. Such type of dependence is attributed to quantum size effect in semiconductors.

Impact Of Cross Linking Chain Of N,N’-bis(napthalen-|-y|)-N,N’-bis(phenyl)-benzidine On Temperature dependent Transport Properties

M. Ramar; S. S. Rawat; R. Srivastava; S. K. Dhawan; C. K. Suman

Advanced Materials Letters, 2016, Volume 7, Issue 10, Pages 783-789
DOI: 10.5185/amlett.2016.6305

The impact of cross linking chain of N, N’-bis (napthalen-|-y|)-N, N’-bis(phenyl)-benzidine (NPB) was studied for opto-electrical properties having focus on temperature dependent transport properties. The Spiro structured NPB compound is closed in itself and the thin film surface roughness is less in comparison to NTNPB compounds. Both absorptions and photoluminence shows a shift of 10 nm towards higher wavelength in case of cross linked spiro structured compound. The mobility calculated in SCLC region for NT and Spiro NPB was 1.32×10 -7 and 3.3x10 -7 cm 2 V -1 s -1 , respectively. Both the compounds show single relaxations and can be modeled as an RC equivalent circuits. The dc conductivity for both the compounds was explained by Mott’s VRH models showing 3D transport mechanism. The hopping distance for NT and Spiro NPB compounds is 0.8 and 0.5 nm, respectively. The hopping conduction process can be explained clearly using correlated barrier hopping model. The cross linking of the compounds shows two orders of less density of states.

Randomly Oriented Rectangular Shaped Structures Of CuO On NiO/ITO Surfaces

Siddharth Joshi; L. Krishnamurthy; G. L. Shekar

Advanced Materials Letters, 2016, Volume 7, Issue 9, Pages 735-742
DOI: 10.5185/amlett.2016.6102

Metal oxide materials are one of the promising materials for low power consumption devices due to their unique size and dimensionality dependent physical and chemical properties. Low cost of production is also a key component in micro/nanoscale devices. Cupric oxide (CuO) nanostructures are of particular interest because of their interesting properties and promising applications in solar cells, bio and gas sensors, batteries, super capacitors, catalysis, photo detectors, energetic materials and removal of organic pollutants from waste water. An attempt has been made to synthesize randomly oriented rectangular shaped nanostructures of CuO, via hydrothermal synthesis at low temperature (~70 °C) on top of NiO porous structured film. The film was deposited using chemical bath deposition method at room temperature using ITO coated glass plate as a substrate. One can observe that the CuO growth on NiO/ITO substrate not only filled the porous structures of NiO but also formed the long rectangular shaped nanostructures which were randomly oriented on top of NiO surface. The CuO rectangular nanostructures have the dimensions in order of (6±2.0) μm x (2.0±0.5) μm. The randomly oriented rectangular structure can assist the charge transport in between the different semiconducting layers. These rectangular shaped nanostructures can also be used in nano-electronic devices, or as a p-type conducting wires in future electronic device applications. The present study is limited to the surface morphology studies of the nanostructured thin layers of NiO/CuO composite materials. Structural and absorption measurements of the CuO/NiO hetero junction have been studied using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV spectroscopy. The energy band gap of both layers NiO and CuO have been calculated using UV spectroscopy and discussed further. Therefore, the present rectangular structure of CuO could be helpful for the purpose of designing novel function nanostructures for efficient energy harvesting.

Correlation Between Oxygen Partial Pressure And Properties Of Pulsed Laser Deposited SnO2/Fe2O3 Composite Films

M. Chowdhury; S.K. Sharma; R.J. Chaudhary

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 930-934
DOI: 10.5185/amlett.2015.6017

SnO2/Fe2O3 composite thin films were deposited on quartz substrates at various oxygen partial pressures with a substrate temperature of 750 °C by pulsed laser deposition. The structural and optical properties of the deposited films were studied by X-ray diffraction (XRD), Atomic force microscopy (AFM), UV–visible spectroscopy and Photoluminescence. X-ray diffraction analysis revealed the formation of mixed phases (tetragonal SnO2 and hexagonal α-Fe2O3) at lower oxygen partial pressure (0.1 mTorr) and only tetragonal phase at higher oxygen partial pressures (50-250 mTorr). Atomic force microscopy studies show the dense and uniform distribution of composite films. The average RMS roughness of the films increases with increasing oxygen partial pressure. The bandgap was found varying between 3.55 and 3.85 eV for different oxygen pressures. A strong broad blue emission band was observed for all the oxygen partial pressures. The origin of the blue emission in the composite film is discussed with the help of vacancy creation. A correlation between oxygen partial pressure and the properties of SnO2/Fe2O3 .

Influence Of Air Annealing On The Structural, Morphology And Optical Properties Of ZnSe Thin Films By CW-CO2 Laser Evaporation

Wuttichai Phae-ngam; Taswal Kumpeerapun;Voravit Kosalathip; Suebtarkul Suchat

Advanced Materials Letters, 2014, Volume 5, Issue 9, Pages 496-500
DOI: 10.5185/amlett.2014.4577

 CW-CO2 laser evaporation was used to deposit ZnSe thin films onto glass microscope slides. The films prepared were annealed in air at annealing temperatures of 100, 200 and 300°C. The effect of annealing temperature on the surface morphology, crystal structure and optical properties was investigated. All samples were seen to have an homogeneous surface morphology. The as-deposited and low temperature annealed ZnSe films exhibited the cubic phase. As the annealing temperature increased, a hexagonal phase developed and at 300°C the ZnO phase began to appear. The average crystallite size of ZnSe films increased from 23.84 to 49.64 nm on annealing at 200°C. Dislocation density, strain in the film and film thickness decreased when the annealing temperature increased up to 200°C. The optical band-gap of the as-deposited film was 2.76 eV decreasing to about 2.70 eV at the 200°C anneal. The introduction of the ZnO phase at 300°C decreased crystallite size whereas it increased film strain. This work shows an easy and economical way to control band gap, crystallite size and film strain in ZnSe thin films by annealing in air. The lack of a pre-heated substrate and the ability to control band gap energy by annealing provides a versatile alternative source of ZnSe film deposition for potential optoelectronic applications.

Mechanical Properties and Deformation Of Ceramic Coated Steels Heat-treated By Scanning Laser

Hirotaka Tanabe; Keiji Ogawa; Yui Izumi; Motoyuki Nishizawa; Tohru Takamatsu; Heisaburo Nakagawa

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 248-254
DOI: 10.5185/amlett.2014.amwc1012

A new surface modification method “laser quenching after coating” using a high power diode laser equipped with a 2-dimensional galvano-scanner unit was developed to process a larger area of ceramic coated steel uniformly and efficiently. The laser irradiation tests for 3 kinds of ceramic-coated steels: CrAlN, TiAlN and CrN, were carried out with the scanning laser, and the appropriate irradiation conditions to achieve the uniformly quenched substrate without any surface damage were clarified for these ceramic-coated steels. The area of the substrate surface wider than the laser spot size could be easily quenched by the scanning laser. The adhesive strength, the film hardness of the laser-irradiated regions and the deformation caused by laser irradiation were evaluated. Laser quenching with the scanning laser can effectively improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of the ceramic-coated specimens. In the deformation of the laser-irradiated specimens, two features were recognized; one is the bending, and the other is the expansion of laser-irradiated part. It was found that the deformation of ceramic-coated steel by laser irradiation under the same heat input condition does not depend on the kind of ceramic thin film but on the steel type of the substrate. It was concluded that “laser quenching after coating” with scanning laser could easily improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of large surface areas in the tested all types of ceramic-coated specimens.

Fabrication And Characterization Of Epitaxial BaTiO3 Thin Film Employing Platinum (111) Template

Antony Jeyaseelan A.; Sruthi S.; Soma Dutta

Advanced Materials Letters, 2013, Volume 4, Issue 8, Pages 632-636
DOI: 10.5185/amlett.2012.11476

Epitaxial Barium Titanate (BaTiO3) thin films were fabricated on Platinised (Pt 111) Si/SiO 2 wafer by spin coating of metalloorganic sol gel solution. A preferred directional growth was obtained for BT (BaTiO3) thin film by employing Platinum (111) coating as a template. BT film was heat-treated at 700°C for 1 hour using the direct insertion method. The film was epitaxially grown with (111) and (211) being parallel to the Pt(111). The epitaxial growth of the thin film along (111) orientation was confirmed by XRD, AFM and SEM. The cross sectional view of SEM image showed that most nuclei were formed at the interface between the film and the substrate. BT thin film was characterized for its ferroelectric, dielectric and piezoelectric properties. Ferroelectric hysteresis measurement yielded high spontaneous polarization value (12.3µC/cm 2 ) comparatively at low electric field (150kV/cm). Substantial increase in piezoelectric d33 was explained in the light of domain wall engineering.

Low Temperature Sensing Of NO2 Gas Using SnO2-ZnO Nanocomposite Sensor

Advanced Materials Letters, 2013, Volume 4, Issue 3, Pages 196-201
DOI: 10.5185/amlett.2012.7390

In the present work an effort has been made to synthesize nanocrystalline composites (NCC) of Zinc oxide and Tin oxide (ZSO) using chemical route for efficient sensing of NO2 gas at lower operating temperature. The structural, microstructural and optical information have been revealed by X-ray diffraction (XRD), Atomic force microscopy (AFM) and UV-Visible spectroscopy respectively. Sensor structure showed a better sensing response (S ~ 6.64×10 2 ) at a relatively low operating temperature of 70 °C for 20 ppm NO2 gas with an average response time of about 2 min. The sensing response characteristics for NO2 gas has been compared with corresponding results obtained for pure SnO2 and ZnO thin film based sensor structure.

Structural properties of Fe doped TiO2 films on LaAlO3 and Si substrates

Komal Bapna; R.J. Choudhary; D.M. Phase

Advanced Materials Letters, 2011, Volume 2, Issue 4, Pages 281-284
DOI: 10.5185/amlett.indias.205

We have prepared 4 at.% Fe doped TiO2 thin films on LAO (001) and Si (111) substrates by pulsed laser deposition. X-ray diffraction (XRD) studies suggest different structural properties of the films on the different substrates. Raman measurements corroborate the XRD findings. The thicknesses of the films are also different on the two substrates, suggesting different nucleation process on the two substrates. Interestingly on both the substrates, Fe is not in metal clusters, suggesting their possible incorporation in TiO2 matrix.