Electrical & Electronics

Overview

Electrical energy storage is one of the most critical needs of 21st century. At present, among various energy storage technologies, Lithium (Li)-ion batteries have conquered the portable electronic market. They have also proven suitable for next generation large scale energy storage (electric vehicle) due to their high energy density and remarkable cyclic life at higher currents. However, Li-ion batteries are expensive due to the heavy capital investment needed in mining and extraction of Li. Li is unevenly distributed in earth crust which is a critical barrier to the scale-up of Li production and thus Li battery energy storage for large-scale applications such as electrical vehicles remains limited. In this perspective, replacing expensive Li based electrodes with a sustainable battery electrode material is a major challenge to meet the increasing demand for portable electronics and zero emission vehicles. Li based active material electrodes and electrolytes may be replaced with the abundant alkaline element in earth’s crust with similar characteristics. In this direction, sodium (Na) based rechargeable batteries have been demonstrated with similar energy storage mechanism in 1980. However, Na-ion cells will always fall short of energy density compared to Li-ion batteries due to large atomic size compared to Li. This large atomic size not only results in lower energy density, it also limits the intercalation of Na into layers of graphite. Increasing surface area and electronic conductivity for improved specific capacity with good cyclic performance is a key challenge for commercialization of Na-ion batteries.

Overview

Joining of metals ceramic parts for high temperature application by complaint (using glue) is prime requirement in the field of solid oxide fuel cell (SOFC), oxygen sensors, thermocouples, high temperature thread lock etc., Development of such high temperature glue are in progress. Sodium silicate/alumina based glue are successfully developed for 800oC applications. The developed paste was demonstrated by using some of the in-house repair work. Further, successfully join silica and Invar-36 for 800oC application. Additionally silica, stainless and silicon carbide flange also demonstrated.

Key Features

• Sealant is in powder and liquid form.
• As per requirement, one can make past prior to application.
• Brush, spatula, or dispenser can do application.
• Low curing temperature in the order of 150oC.

Potential Applications

• Electrical such as heater and lamps.
• High temperature sodium batteries
• Sealant for solid oxide fuel cells
• Temperature probes bonding to the required surface.
• Refractory insulations.

Intellectual Property Development Indices (IPDI)

• Feasibility studies on SS/SiC/SiO2 was done
• Repair on broken porcelain flange was done as in-house work
• Silica dome and Invar flange was successfully join for another government sector company.

Percaline In-house repair

Major Patents / Publications

Major Patents

Major Publications

Overview

Due to reduced material and energy input thin-film provides still advantages compared to crystalline silicon-based PV technologies. In terms of cost per watt and efficiency of Cu(In,Ga)Se2 (CIGS) solar cell is considered to be the most promising thin-film PV technology. The efficiency evolution of CIGS during the last few years has been the most impressive within the thin-film materials, moreover comparable to multi-crystalline silicon cells and even more efficient than amorphous silicon (a-Si) and cadmium telluride (CdTe) while using a minimum of materials to produce. The current challenges include reducing the manufacturing cost and faster transfer of R&D results to industrial production. Due to the fact that the CIGS manufacturing process is more complex and less standardized than for other types of cells, it is necessary to select appropriate process route and maintain the manufacturing as flexible as possible. A monolithically integrated CIGS thin film solar cell on 300 mm x 300 mm being research and developed at ARCI has promising features over the existing technologies

Key Features

• Unique non-toxic two step, sputtering of precursor and atmospheric selenization process.
• Device configuration: Ag/AZO/ZnO/CdS/CIGS/Mo/Glass
• Tooled to make monolithically integrated CIGS thin film solar modules on 300 mm x 300 mm.
• Potential to make device on flexible substrates.

Potential Applications

• Building integrated photovoltaics (BIPV)
• Application for DC power appliance

Intellectual Property Development Indices (IPDI)

• Maximum photo conversion efficiency of 8.2% on lab scale device
• Developed 50 x 50 mm monolithically integrated module with 5% efficiency.
• Demonstrated running 2V DC motor with propeller with the power output from mini module.
• Improvement in device performance on lab scale and module level is underway

I-V of CIGS thin film solar cell on lab device

I-V of monolithically integrated 50 mm x 50 mm module (Inset: Picture of in-house developed module)

Major Patents / Publications

Major Patents

Major Publications

• Process parameter impact on properties of sputtered large-area Mo bilayers for CIGS thin film solar cell applications, Amol C. Badgujar, Sanjay R. Dhage*, Shrikant V. Joshi, Thin Solid Films 589 (2015) 79–84
• Transparent conducting Al:ZnO thin film on large area by efficient cylindrical rotating DC magnetron sputtering. Sanjay R. Dhage* and Amol C. Badgujar, Journal of Alloys and Compounds Vol 763, (2018) 504
• Process parameter impact on selective laser ablation of bilayer Molybdenum thin films for CIGS solar cell applications, Amol C. Badgujar, Shrikant V. Joshi and Sanjay R. Dhage*, Materials Focus 7 (2018) 1-7

Overview

CIGS-based solar cells are one of the most promising thin film solar cell technology with steadily improving cell efficiencies and large-scale commercial manufacturability. Although conventional CIGS technology was established on rigid glass substrates, significant progress has been made during the last decade in the direction of developing ‘flexible’ CIGS panels made on polymer film and metal foil substrates. This has opened a niche market for CIGS based products in the form of standalone charging solutions for transportation systems and portable electronics. At ARCI, flexible CIGS solar cells are being developed on stainless steel foils for use in portable charging applications.

Key Features

• Well established vacuum based sputtering and selenization route for making high quality CIGS absorbers on flexible substrates
• Easily scalable, dip coated Fe-diffusion barrier layer between SS substrate and Mo back contact
• Thin, flexible and lightweight CIGS mini-modules
• Possibility to integrate CIGS base charging solution into common daily use items like backpacks and umbrellas

Potential Applications

• Portable chargers for consumer electronics
• Mobility systems such as mini-drones and UAVs
• Standalone off-grid lighting solutions
• Building integrated PV

Intellectual Property Development Indices (IPDI)

• Established baseline processes to fabricate CIGS cells on SS foils
• Working lab-scale devices made and I-V performance evaluated

Major Patents / Publications

Major Patents

Major Publications

Overview

Flexible photovoltaics (PV) are the need of the hour for various energy applications. Cu(In,Ga)Se2 (CIGS) possessing large absorption coefficient and excellent log-term stability is a potential candidate for flexible PV with already demonstrated commercial maturity. However, cost is the major aspect for portable energy applications even with a slight compromise on device efficiencies. Electrodeposition having the ability for roll-to-roll manufacturing with lower capital investment is among the most explored processes for CIGS. Pulse electrodeposition is an advanced feature which significantly simplifies the conventional process while improving the absorber quality owing to its crucial pulse parameters is being pursued for the realization of low-cost flexible CIGS solar cells. Additionally, an all non-vacuum based CIGS solar cell on Mo substrates is being fabricated with other device layers like CdS, ZnO and AZO are solution processed while ZnS is also used as replacement for CdS towards Cd-free CIGS solar cells.

Key Features

• A simple economic pulse electrodeposition route for CIGS solar cells
• Efficient utility of electroreduction and oxidation phenomena
• Process devoid of any complexing agents, additives and third reference electrode
• Suitable for large area and roll-to-roll manufacturing on flexible substrates

Potential Applications

• Portable energy needs
• Building integrated photovoltaics
• Photoelectrochemical cells

Intellectual Property Development Indices (IPDI)

• Demonstration of 6.1 % efficient CIS solar cells at laboratory scale
• Scale up of uniform CIGS absorbers till 8 x 8 cm2

Major Patents / Publications

Major Patents

Major Publications

• B. V. Sarada, Sreekanth Mandati and Shrikant V. Joshi, A novel electrochemical method for manufacturing CIGS thin-films containing nanomesh-like structures, Patent filed, File No: 426/DL/2015, Date: 16th February, 2015
• Sreekanth Mandati, S. R. Dey, S. V. Joshi and B. V. Sarada, Cu(In,Ga)Se2 Films with Branched Nanorod Architectures Fabricated by Environmental-friendly Pulse-reverse Electrodeposition Route, ACS Sustainable Chemistry and Engineering 6(11), 13787 (2018)
• Sreekanth Mandati, Suhash R. Dey, Shrikant V. Joshi and Bulusu V. Sarada, Two-dimensional CuIn1-xGaxSe2 Nano-flakes by Pulse Electrodeposition for Photovoltaic Applications, Solar Energy 181, 396 (2019)
• Divya B, Sreekanth Mandati, Ramachandraiah A, Bulusu V. Sarada, Room Temperature Pulse Electrodeposition of CdS Thin Films for Application in Solar Cells and Photoelectrochemical cells, ECS Journal of Solid State Science and Technology 7(8), P440 (2018)

Overview

Non-vacuum processes have great interest for low cost chalcopyrite based photovoltaic technologies in CIGS thin film solar cell fabrication. A key feature in these processes is the selenization treatment has significant impact on the microstructure of the absorbers and, in turn, are determining for the performance of the device. In this context, a two step non-vacuum process, spraying of sonochemically synthesized CIGS nanoparticles suspension followed by post treatment (IPL/laser treatment or atmospheric selenization). A non-vacuum based route using Photonic sintering, novel atmospheric pressure thermal annealing is being developed to reduce the number of processing steps in complete cell fabrication and has great potential to be incorporated in to roll-to-roll manufacturing of cost effective CIGS thin film solar cells.

Key Features

• Scalable non vacuum manufacturing process for CIGS without toxic selenization
• Simple ambient sonochemical synthesis for CIGS NP’s with high material utilization
• Solution process using spraying technique
• Environmentally benign flash light and/laser post-treatment method
• Processing on Light weight and flexible glass substrate

Potential Applications

• Building integrated photovoltaic (BIPV)
• Application for DC Power Aplliance
• Powering Internet on things (IOT) based applications

Intellectual Property Development Indices (IPDI)

• Fabricated device demonstrated photo conversion efficiency exceeding 4% on lab scale
• Performance improvement by fine tuning the process parameters is underway

IV curve of non-vacuum processed CIGS thin film solar cell

Surface morphology of CIGS thin film absorber on Mo glass by non-vacuum ink based route

Major Patents / Publications

Major Patents

Major Publications

• Improved method of manufacturing copper-indium-gallium diselenide thin films by laser treatment. Patent application No: 2084/DEL/2212, Date: 05/07/2012, Inventors: Sanjay R. Dhage, Manish Tak and Shrikant V. Joshi
• Sonochemical synthesis of CuIn0. 7Ga0. 3Se2 nanoparticles for thin film photo absorber application, Amol C. Badgujar, Rajiv O. Dusane and Sanjay R. Dhage, Material Science in Semiconductor Processing 81 (2018) 17.
• Cu (In, Ga) Se 2 thin film absorber layer by flash light post-treatment, Amol C. Badgujar, Rajiv O. Dusane and Sanjay R. Dhage, Vacuum 153 (2018) 191.

Overview

The existing high temperature and vacuum processing and selenization treatment used in CIGS thin film solar cell fabrication are neither cost effective nor easily scalable to high volume production. Non-vacuum processes have great interest for low cost chalcopyrite based photovoltaic technologies. A key feature in these processes is the selenization treatment has significant impact on the microstructure of the absorbers and, in turn, are determining for the performance of the device. In this context, a two-step non-vacuum process (inkjet printing and selenization) for the preparation of CIGS absorber layer is being developed at ARCI. The process is novel and expected to have large impact in CIGS PV industry in terms of cost reduction and easy processing. Moreover, the non-vacuum route will reduce the number of processing steps in complete cell fabrication.

Key Features

• Scalable Inkjet printing process for quality CIGS thin film absorber preparation
• High material utilization technique because of drop on demand feature
• Mask-less and non-contact approach
• Fast and cost effective atmospheric pressure RTP selenization process
• Processable on Light weight and flexible glass substrat.

Potential Applications

• Building integrated photovoltaics (BIPV)
• Application for DC power appliance

Intellectual Property Development Indices (IPDI)

• Achieved 4.7% photo conversion efficiency on lab scale device
• Proved technical feasibility of process and proof of concept
• Performance improvement and evaluation underway

Schematic of inkjet printing of CIG precursor film

AM1.5 and Dark I-V of ink jet processed CIGS thin film solar cell (inset: Device x-section)

Major Patents / Publications

Major Patents

Major Publications

• Chalcopyrite CIGS absorber layer by inkjet printing for photovoltaic application, Brijesh Singh Yadav, Suhash Ranjan Dey and Sanjay R Dhage, material today proceedings, volume 4, issue 14 (2017)12480-12483
• Effective printing strategy for Cu (In, Ga) Se2 thin film absorber using aqueous ink for solar cell application” Brijesh Singh Yadav, Suhash Ranjan Dey and Sanjay R Dhage, Solar Energy 179 (2019) 363–370
• Role of selenium content in selenization of inkjet printed CIGSe2 thin film solar cell” Brijesh Singh Yadav, Suhash Ranjan Dey and Sanjay R Dhage, AIP Conference Proceedings 2082 (2019) 050001

Overview

Indian industrial sector needs both power and thermal energy for their manufacturing processes. Recently, Indian industries shown interest in exploit renewable energies, especially solar energy, due to their economic and environmental-friendly advantages. In this regard, centre for solar energy materials, ARCI has developed a cost-effective selective coating to convert solar radiation into a heat which can be used for low and medium temperature industrial process heat applications. We followed a facile wet chemical route using a combination of novel chemical oxidation, sol-gel and nanoparticle coating methods. The developed high selective receiver tube offers good mechanical strength along with high corrosion resistance. The high-performance cost-effective receiver tube with a capability of facile upscaling attracting many industries and technology has been transferred to an Indian industry as non exclusive basis (Greenera Energy India Pvt. Ltd).

Key Features

• High selective properties (Solar Absorptance ~95%; Spectral emittance ~0.12)
• Low heat loss property: ~0.14 at 250 °C
• Temperature stability: < 250 °C
• High corrosion resistance > 200 hrs withstand in salt spray test (ASTM B117)
• High mechanical stability

Potential Applications

• Solar hot water & Sea water desalination
• Solar drying and Cooking
• Space and Swimming pool heating
• Solar cooling
• Industrial process heat applications
• Power generation

Intellectual Property Development Indices (IPDI)

0.5-meter tandem absorber ,4-meter prototype receiver tube

Major Patents / Publications

Major Patents

Major Publications

• Filed an Indian patent application no 2142/DEL/2015 on 15/07/2015

Overview

Spectrally selective receiver tube is the critical component in Concentrated Solar thermal (CST) technology. To increase the overall efficiency of a CST system, we need high thermal stable spectral selective coating which can be operated at ≤500 °C and should sustain minimum of 25 years without any functional degradation. In order to meet the challenge, we designed and developed a high performance solar selective coating with spinel structures by using transition metals like Mn, Cu and Ni by wet chemical method. Spinel’s are amenable to the substitution of a large number of transition metals to tune the optical properties with high thermal stability. We employed a facile low cost wet chemical method to develop coatings.

Key Features

• High solar absorptance αsol= 0.97 & Low emittance ε = 0.16
• Spinel based nanocomposite oxide
• Thermally sable coating up to 500 °C
• Cost effective

Potential Applications

• Stream generation for various industrial applications
• Power generation
• Solar water heater /Solar dryer
• Solar desalination

Intellectual Property Development Indices (IPDI)

Major Patents / Publications

Major Patents

Major Publications

• Indian patent application no. 2142/DEL/2015, date of filling: 15.07.2015.
• Solar Energy Materials and Solar Cells 174 (2018) 423–432

Overview

Solar collectors are very important devices for increasing energy efficiency in concentrated solar thermal power (CSP) for various industrial applications. Low to medium temperature stable solar absorber coating plays an important role in industrial process heat, desalination and solar hot water applications . For such application, coatings on large area and generation of solar receiver tubes are required by an economic way is one main objective to reduce the cost of power generation from solar energy. The technology involves an economical, efficient and environmental friendly non-chrome based absorber coatings by electrodeposition route

Key Features

• Cost effective and environmental friendly non-chrome based electrodeposition route
• High optical properties (solar absorptance: 94-95 % and thermal emittance: <0.20 (at 300°C)
• Temperature of operation: <300°C
• Good mechanical and weather stability

Potential Applications

• Stream generation for various industrial applications
• Solar water heater
• Solar desalination
• Solar dryer

Intellectual Property Development Indices (IPDI)

• Performance and stability are validated at laboratory scale
• Scale up of electrodeposited coating development are completed

Highlights

• Csp of 1977 F/g at 1 A/g by half cell and 91.5 F/g at 0.5 A/g by full cell analysis
• Maximum energy density of 28.59 Wh/kg and a power density of 7.5 kW/kg
• 74% capacitive retention for 5000 cycles

Image of non-chrome based absorber coating on SS tube and copper foil

Major Patents / Publications

Major Patents

Major Publications

• Indian patent to be filed

Overview

The enhancement of thermal behavior of Heat transfer fluid (HTF) by using high specific heat capacity nanostructure materials such as smart carbon ( Carbon Nano Clusters (CNCs), Layer Structured Carbon and Graphene nanocomposite) based materials can be provided enormous benefits for heat transport phenomena which are primary importance to solar thermal power generation and industrial heat transportation. Due to nanometer-scale materials, particles are well stable without sedimentation.

Key Features

• High heat capacity & thermal conductivity
• High specific surface area and therefore more heat transfer surface between particles and liquids
• Reduced sedimentation & pumping power
• Adjustable thermal properties
• Cost effective and easy to prepare
• 27% enhancement in specific heat capacitance

Potential Applications

• Industrial cooling applications
• Solar thermal power plants
• Extraction of geothermal power and other energy sources
• Cooling of Microchips
• Lubricants

Intellectual Property Development Indices (IPDI)

Commercial HTF & ARCI’s nano HTF

Carbon Nanoclusters (CNCs) Graphene nanocomposite, Specific Heat capacity of Graphene nanocomposite based HTF

Major Patents / Publications

Major Patents

Major Publications

Overview

Al:ZnO (AZO) has emerged as popular transparent conducting electrode material replacing conventional indium tin oxides (Sn:In2O3) and fluorine doped tin oxide (F:SnO2) as non-toxic, cheaper and available in abundance. AZO thin films finds application in wide range of areas such as solar cells, flat panel displays, organic light emitting diodes, gas sensors, photo-catalysis, transistors, and electromagnetic interference shields (EMIS) and piezoelectric devices. Apart from exclusive use in CIGS thin film solar cells, AZO is widely being applied as transparent conducting contact in dye sensitized, perovskite, CdTe and Si based solar cells. DC magnetron systems with cylindrical rotating targets was used for large area deposition, which has advantages of possess high plasma density, faster deposition rate and enables better control over the sputter deposition process, required for high thickness uniformity over large area. Best resistivity and transmittance with high thickness uniformity on 300 mm x 300 mm glass substrate was achieved on the AZO thin films sputtered using optimized process conditions considering technological aspect.

Key Features

• AZO thin films with high transmittance and conductivity on 300 mm x 300 mm glass substrate
• Highly uniform films (Std deviation 20.65%) with visible light optical transmittance 84% and least resistivity of 4.07 X 10-4 ohms.cm.
• Figure of merit confirms the suitability of AZO thin films for various optoelectronic device applications as compare to other existing TCO films.

Potential Applications

• Solar energy
• Electrical and electronics
• Sensors

Intellectual Property Development Indices (IPDI)

• Application development completed

Transmission curve of AZO thin film on glass (Inset: SEM X-Section image)

Major Patents / Publications

Major Patents

Major Publications

• Transparent conducting Al:ZnO thin film on large area by efficient cylindrical rotating DC magnetron sputtering. Sanjay R. Dhage* and Amol C. Badgujar, Journal of Alloys and Compounds Vol 763, (2018) 504

Overview

CIGS solar cell fabrication begins with sputter coated Molybdenum (Mo) on soda lime glass (SLG) substrate which acts as a back contact, likewise Mo thin film back contact is also exclusively being used in CZTS, CdTe and Sb2Se3 thin film solar cells. Moreover, Mo thin films has wide range of applications, as an electrode in optoelectronical systems. Properties of Mo thin film are dependent upon various sputtering parameters such as power, pressure and substrate temperature. Precise optimization of sputter process parameters such as sputtering power and deposition pressure in the bilayer approach can effectively achieve high electrical conductivity and strong adhesion; in addition, substrate cleaning and surface treatment play a crucial role influencing adhesion between SLG and Mo thin film. Surface conditioning of glass substrate to sputter coat adherent thin films via cost-effective, scalable, environmentally benign process has potential technological benefits. Sputtering process parameters were optimized on DC cylindrical rotating magnetron system to obtain stress free, conductive, well adherent and uniform Mo thin films on substrates of size 300 mm x 300 mm for contact applications.

Key Features

• Mo thin films of 500 nm thickness using rotating DC magnetron on SLG substrate of the size of 300 mm x 300 mm
• High uniformity of thickness (Std. Dev. 3.17%), best electrical (resistivity of 1.59E-05 ohm.cm), mechanical and optical properties of Mo thin film over large area.
• High reflectance in IR region
• High adhesion strength on Mo to glass substrate

Potential Applications

• Solar energy
• Electrical and electronics
• Sensor

Intellectual Property Development Indices (IPDI)

• Application development completed

FESEM X-Section image of Mo thin film on glass

Summary of best achieved properties of Mo thin film on glass

Major Patents / Publications

Major Patents

Major Publications

• Molybdenum bilayer thin film on large area by cylindrical rotating DC magnetron sputtering for CIGS solar cell application, Amol C. Badgujar, Brijesh singh Yadav, Suhash R Dey, Rajiv O. Dusane and Sanjay R. Dhage* Proceedings of 35th EUPVSEC 2018
• Effect of various surface treatments on adhesion strength of magnetron sputtered bi-layer molybdenum thin films on soda lime glass substrate, B.S.Yadav, Amol C. Badgujar and Sanjay R. Dhage*, Solar Energy 157 (2017) 507-513
• Process parameter impact on properties of sputtered large-area Mo bilayers for CIGS thin film solar cell applications, Amol C. Badgujar, Sanjay R. Dhage*, and Shrikant V. Joshi, Thin Solid films 589 (2015) 79-84

Overview

The development of low cost coating for corrosion and environmentally sensitive metallic substrates are inevitable in high temperature application. One such low cost processing techniques is slurry coating. This coating process involves spray the formulated coating material applied to the area to be coated and heated in an ambient or under inert gas atmosphere. The major part of research and development activates involves preparation of suitable slurry.

Key Features

The slurry process make new opening for developing various metal ceramic and composites coating with following merits.

• Low cost
• Lack of access to machinery capable of other deposition methods
• Flexibility to apply the coating to complex surfaces
• Composites of metal-ceramic, polymer-ceramics, metal-polymers etc.,

Potential Applications

• Thermal protection shield for low melting substrates such as aluminum and polymer composites.
• Copper-glass composites for high temperature electronics.
• Slurry based environmental barrier coatings (EBC) on silicon carbide.

Intellectual Property Development Indices (IPDI)

• Exploratory studies on aluminum and polymeric substrates for thermal protection.
• Copper thick printing on alumina and aluminum nitride.

Thick Copper coating on Al2O3

Major Patents / Publications

Major Patents

Major Publications

Overview

Field electron emission (FE) is a phenomenon where emission of electrons induced by an electrostatic field. The most common context is field emission from a solid surface into vacuum. However, field emission can arise from solid or liquid surfaces, into vacuum, air, a fluid, or any non-conducting or weakly conducting dielectric. Carbon nanotubes (CNT) have attracted much attention owing to their mechanical, electrical and thermal properties etc. CNTs are promising candidates for use in FE devices and nanoelectronics as they possess sharp tips with unusual characteristics. These types of application will require a fabrication method capable of producing CNTs with well-defined and controllable properties such as the orientation, spatial distribution, diameters and lengths of the CNT. In addition, FE devices would need island-like structured high density and well-ordered nanotube arrays to alleviate screening effect. Our technology demonstrates the production of CNT arrays and producing microislands through ultrafast laser-assisted micromachining to improve FE characteristics.

Key Features

• Self-assembled arrays of macroscopic carbon nanotube forest 
• Easy to control height and spatial distribution of carbon nanotubes 
• Nitrogen-content modulated arrays of carbon nanotubes 
• Microstructure-tuned edge-density controlled carbon nanotube arrays
• Laser-assisted patterned arrays of microislands with assorted size
• Optimized-growth of carbon nanotube forest on silicon wafer
• Scalable process in batch-mode

Potential Applications

• For electron gun 
• For microwave amplifiers
• For X-ray tubes
• For flat panel display

Intellectual Property Development Indices (IPDI)

• FE performance and stability are validated at laboratory scale
• Cathode material is integrated to an electron gun and field emission properties were evaluated.

SEM micrographs of aligned carbon nanotube forest

Major Patents / Publications

Major Patents

• Nanotech Insights Vol. (3-4), 94-97 (2014) 
• J. nanoelectronic and optoelectronics 8 (2),177-181 (2013) 
• AIP Conf.Proc. 1538, 196-199 (2013)