Chemical Physics of Thin Film Deposition Processes for Micro- and Nano-Technologies (Nato Science Se

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Design and development of high speed TTL monolithic circuits with paraphrase output patented in co-authorship with others. Several projects have been awarded by "Cum Laude" citation by Intel's and Science Museum "Young Scientists" competition of year two projects , year two projects , year two projects , year one project , and year one project. Ygal Eisenberg received his B.

Eisenberg prepares a thesis in a photovoltaic area. He has experience in design, technology and characterization of diffractive optical elements, micro-optics and micro-lithography. His scope of the interests includes an advanced micro-technology systems, 3D characterization of micro-structures using optical microscopy, white-light micro-interferometry and multi-wavelength confocal scanning microscopy.

Eisenberg has several publications in the micro-technology area. The project is devoted to development of fast electrically-controlled optical components based on the use of new LC materials - stressed liquid crystals SLCs that are comprised of a LC matrix in which an oriented polymer network is formed.

Publications

The project will result in the application of the SLC technology for development of several ultra-fast active LC optical components for military and civilian applications. During the implementation of the project the SLC technology will be extended to the components that contain the curved and profiled substrates. The chemical, mechanical, thermal and adhesive properties of SLC materials will be adjusted to the requirements for the optical components and special SLC compositions to get a minimal driving voltage at the fastest electric response and maximal control of the birefringence range will be developed.

Zvi Kotler Orbotech ltd , — , https: Development of the Generic Universal Design and Technology for the Unique Ultrafast Dynamic Beam Shaping Micro-optical Components, based on the innovative nanocolloidal material, which will be operated with the sub-microsecond switching time in the UV, visible and NIR ranges and suitable for the high power laser systems.

The second direction connected with adaptation of the Generic Universal Design and Technology, fabrication and measurement of the novel specific Ultrafast Dynamic Beam Shaper. This unique patentable Micro-optical Component, based on the innovative nanocolloidal material, will be operated with the sub-microsecond switching time in the UV, visible and NIR ranges and suitable for the high power laser systems. Fast Switching in the range of - milliseconds due to the use of the innovative design, material and technology.

Novel basic design and manufacturing technology for Millimeter-sized Lens Arrays, operated in the infrared range, will be developed by our team in this Project. Several samples of the Millimeter-sized Lens Arrays will be fabricated and characterized. Combination of the optimal design and novel basic manufacturing technology with advanced material for fabrication of the Millimeter-sized Lens Arrays, suitable for the infrared range, is proposed.

Completion of the Project will solve interdisciplinary problems of the research, which will combine several technologies photolithography, micro-structuring, vacuum evaporation and millimeter-sized optics with advanced photopolymer material, resulting in the development of one final product.

The performances of liquid crystal cell are tested by electro-optical measurements. The optical response of the cell is usually measured upon voltage application. For accurate measurements a fine tuning of the optical components, and especially the cell, is required. For the measurement of Stressed Liquid Crystal SLC cells, the application of controlled micromechanical shear also should be integrated in the micro-electro-optical system, which will be developed.

After completion of the Project, the following results will be obtained:. A new concept and a simple design for the micro-electro-optical system of direct measuring the SLC cell transmittance, during alignment of SLC molecules, when one substrate of the cell is micromechanically sheared relative to another substrate, will be developed by our team in this Project. The Project has a great potential for industrial applications in Israel.

However, the cylinder screen is also considered to be attached and sealed at both ends. The semirigid planar surface creates tension in the opposite direction of the mesh, similar to the tensions generated via the interaction between synthetic polyester monofilaments or stainless steel.

This stretched printing screen achieves three discrete purposes: This method eliminates any loss of the coating solution and produces a large wet thick film with a high viscosity. The screen printing method uses thick film printing, producing films that are around 10—15 microns. This method is widespread in the electronic industries to manufacturing DSSC in producing miniature and robust electronic circuits in a cost-effective manner, massive and automated, well-defined, and with highly reproducible structures.

First, the thick film screen printing ink or paste is pressed onto the substrate by a mechanical squeegee, transferring the patterns [ 22 ]. This method consists of a solvent organic or inorganic salt and a binder TiO 2 particles. The role of the solvent provides an ink homogeneous mixture for printing purposes. The screen includes woven mesh of stainless steel, nylon, or polyester mounted under tension on a metal frame. During printing, the substrate is held at a distance from one side of the screen and the ink is deposited on the screen from the opposite side, while a squeegee traverses the screen under pressure.

The nonvolatile portion of the solvent evaporates under high temperature. The most popular screen printable ink recipe contains ethanol for its solvent, terpineol for its dispersant, ethyl cellulose for its thickener, and Triton X for its surfactant [ 23 ]. The water solvent causes cracks to form on the film, so organic solvents are used. The long stability and superior morphology of TiO 2 are important in dye adsorption, which utilize terpineol component and ethyl cellulose, respectively. The loading nanoparticles on screening print are important, because they affect the TiO 2 structure, although they reduce the efficiency of DSSC if the dispersion is incomplete.

The low current output and the decline in the efficiency of the solar cell are due to the agglomeration of nanoparticles. The thickness of the coated film is superior compared to the other methods, such as offset lithography, gravure, flexography, xerography, or ink-jet printing, caused by the flow of coating material being under pressure into and through this mesh or matrix via coating on the substrate.

The high efficiency for DSSC is around 9.

The ZnO nanoparticle shows an efficiency of 1. The electrospray forms droplets from the sample solution, such as nanoparticles, and these droplets will be deposited on various substrates. The uniform solid film is formed by evaporating or heating the solvent on the surface via sintering. The thin films could be formed by a precursor compound, which decomposes at high temperatures or converts to another substance via chemical reactions with other compounds that are simultaneously sprayed or delivered during its gaseous phase [ 30 ].

This method could be used in physical and chemical reactions that are taken into account in the physical aspect in this review. The metal nitrates or acetates dissolve in water, methanol, and ethanol, and these mixtures are electrosprayed as precursors for a metal-oxide layer production. The advantage of this method is the usage of the less soluble materials [ 31 ], the ability to control charge droplet, the lack of solvent evaporation effects, and the ability to form multilayered thin films.

The significant advantage of ESD is the multilayered thin film growth being superior compared to spin coating, dip coating, and screen printing, since the bottom organic layer solvent during the top layer growth cannot be avoided [ 32 ]. The nanocrystalline TiO 2 electrodes [ 33 ], porous TiO 2 films [ 34 ], and terpyridine-coordinated dye [ 33 ] had the efficiencies of 5. The spray dye molecules onto TiO 2 surfaces used this method to develop molecular dye sensitized solar cells [ 31 ]. Thin film deposition via PVD is regarded as a vacuum coating technology and is classified into two techniques, evaporation and sputtering.

The material could be coated in an energetic and entropic environment, since the particles will escape from the surface. The solid layer that is formed on the surface is due to the cooling of the particles once they lose their energy when immobilized. The particles are capable of moving in a straight path because the system is kept in vacuum, and the films are coated by physical means that are commonly directional, rather than conformal, in nature.

Generally, thin films are deposited by evaporation. The source material is evaporated in a vacuum, which allows the vapor particles to travel directly to the substrate as a target and condense into a solid state.

Thermal evaporation is a simple and economical method in fabricating thick films and microfilms Figure 6. The source materials are melted or sublimated via electrical heating, converting it into a gaseous phase. The vapor particles will then achieve a certain velocity in the chamber and will attempt to condense on the substrate.

The substrates are located close to the source materials. The high vacuum condition in the vacuum chamber will act to prevent the particles from scattering and minimize the residual gas impurities. There are some disadvantages, including poor adhesion because of low affinity with substrate surface and the need to use an adhesive layer due to evaporated temperature, metal and low melting point materials are suitable and refractory materials and multicomponent alloys cannot be used, contamination problems, and poor step coverage rendering pattern making impossible.

The film coated without contamination is made by materials that have a much higher vapor pressure than the heating element. Electron beam evaporation used high-speed electrons to bombard the source materials. During this process Figure 7 , the kinetic energy will be converted into thermal energy, which increases the temperature of the source. An electron gun creates the electron beam.

The crucible acts as an anode and is cooled by cooling water to prevent contamination. Consequently, a pure thin film is formed. Quite a number of materials could be formed using this method, such as dielectric oxide, refractory metals, and metal oxide Table 3. These advantages enhance the uniform thickness and create a multilayer deposition by changing the crucible and making multiple target film possible.

The surface, however, could easily be damaged by the decomposition or ionization of the target.

However, the enormous electrical energy and X-ray that is consumed in this method put it at a distinct disadvantage. The sputtering method was discovered in as a means to monitor metals deposit at the cathodes of a cold cathode glow discharge.

This method was used to coat mirror fabrics and phonograph wax masters. We analyzed two kinds of sputtering, including DC magnetron sputtering and radio frequency RF magnetron sputtering.

PUBLICATIONS

DC magnetron sputtering could increase deposition rates with minimal damage to the substrate, while the RF magnetron sputtering plays an important role in allowing direct deposition of insulators. The high quality deposition materials such as metal, alloy, and simple organic compound coatings were deposited using the sputtering method, which precipitates the preference of this method over other PVD methods such as EBE and thermal evaporation Table 5.

Sputtering is considered a momentum transfer procedure. As the particles collide with a surface, the procedure is dependent upon the incident particle energy, the incidence angle, the surface atoms binding energy, and the colliding particles mass Figure 8. The ions are regarded as the incident particles in sputtering, which are accelerated by an applied electrical potential. The surface will be damaged as the kinetic energy is higher than the surface atom binding energy when the atoms are placed into new lattice positions.

Publications - Scientific Computing International

The sputtered atoms and ions deposit the thin film onto the substrate. A low-pressure process of the glow discharge type will usually cause energetic ion bombardment. The basic diode process is revealed in Figure 9. During the sputtering process, the heat generated in the target is connected to a water-cooled metal copper backing plate with a solder or conductive epoxy, which cools the target. An electrical potential is applied between the cathode and anode. Grounded shields avoid discharges from forming in undesirable areas.

The sputter yield is dependent on the target material; for example, silver has high yield. The deposition of large amounts of materials, including compounds and mixtures, the inducement of better step coverage and uniformity, and good adhesion with low substrate temperature are some of the advantages of this process, but the risk of substrate damage due to ionic bombardment is omnipresent. DC magnetron sputtering is one of the simpler and older sputter depositions methods. This method should be used for conductive materials and is unsuitable for dielectric material targets Table 6.

Kvalifikatsioon

The good adhesion, very low levels of contamination, film properties control of pressure, bias, and temperature are some of the advantages of DC sputtering, whereas some of its significant disadvantages include plasma electrons bombarding the substrate and producing heat, high working gas pressure, low deposition rate, and targets being limited to electrical conductors. The performance of this system can be improved by cathode systems. Insulating materials are suitable as materials in RF sputtering, which are induced by a positive charge on the target surface Table 7.

Text books

Defects in chlorine-doped cdte thin films. Trans Tech Publications Ltd. Solid State Phenomena; Complex Defects in ZnSe-based Phosphors. Grassie et al Ed. The influence of nacl on the microstructure of cds films and cdte solar cells. Comparative study of isothermal grain growth of cds and cdte in the presence of halide fluxes. Photoluminescence properties of Z-bands in CdTe. Growth of cdte monograin powders. Monograin layers as optoelectronic devices.

Group II-VI downconverting phosphors. Recrystallyzation of CIS Powders in molten fluxes. Technology of CdTe monograin powders. Proceedings of the Estonian Academy of Sciences. Monograin powders and layers for photovoltaic application. Date of birth Member of societies and institutions:. Estonian Chemical Society , since Materials Research Society since Baltic Materials Society, since Natural Sciences and Engineering; 4. Liquid phase chemical deposition of compound semiconductor thin films, process chemistry, structural, optical and electrical properties of the films.

Teenistuskäik

Chemical technologies for production of solar cells. TAR "Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics 1. IUT "Thin films and nanomaterials by wet-chemical methods for next-generation photovoltaics 1. ETF "Thin film solar cells on the basis of calcogenide layers deposited from water solution 1. TK "Mesosystems - Theory and Applications 1. AR "New materials for solar energetics 1.

AR "Efficient plasmonic absorbers for solar cells.

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