PROCESSES DEVELOPED

INSTRUMENTS DEVELOPED

DEVICES FABRICATED

INDUSTRIAL COLLABORATION

 

 

 

PROCESSES DEVELOPED

 

The Laboratory has contributed significant innovations in the following thin film deposition processes:

 

Electroless and Chemical Conversion

 

Simple and inexpensive electro less and chemical conversion techniques have been developed to convert the surface of GI, stainless steel, molybdenum, aluminium (after pigmentation with nickel or cobalt) and copper to a solar selective black surface with high absorptance in the vIsible and low emittance in the infrared.

 

Chemical Solution Growth

 

This novel technique, known previously on black box basis, has been put on scientific foundations and extended to prepare variable composition binary, ternary, quarternary and quinary alloys and compounds of chalcogenides of several I to V period elements. Also, several transparent conducting oxide films have been prepared. The technique has made possible the deposition of large area multilayer coatings of tailored properties and dimensions for photothermal conversion and solar cell applications.

 

Spray Pyrolysis

 

Comprehensive studies of the effect of spray pyrolysis parameters on the opto-e1ectronic properties have enabled us to refine the technique to allow control of dopants, stoichiometry, microstructure and gradient of compositions.

 

Microlithography

 

Radiation (photons, electrons and ions) induced giant physical and optical densification effects discovered by us in Ge-S and Ge-Se based amorphous films have been exploited to produce high resolution, submicron reprographic and lithographic patterns of interest for optical memories and microelectronics.

 

INSTRUMENTS DEVELOPED

 

The Laboratory has contributed significantly towards indigenous design and development of instruments/equipment. An electronic instrument design and development cell has been established in the Laboratory with a view to help students set up various experimental facilities and to maintain and repair instruments like TEM, Spectrophotometers, ESCA/SAM/SIMS and DTA. Some of the instruments developed are:

 

      6 KW 180 bent beam Electron Gun for deposition of high melting point materials and multi component alloys.

      Planetary System for uniform deposition of films.

      Optical Thickness Monitor to monitor film thickness during deposition.

      DC and RFMagnetron Sputtering Module to deposit multi component alloys of refractory materials and mixtures of oxides, carbide and nitrides.

      Intergrating Sphere Reflectometer for measurement of solar absorptance,

      Vacuum Calorimeter designed to obtain the solar absorptance, thermal emittance, a/e ratio and stagnation temperatures,

      Ellipsoidal Concentrator to measure thermal emittance of a sample under simulated and actual test conditions.

      I-V and log I vs V Plotter to obtain currentvoltage plots and temperature dependence thereof in light and dark with facility for on-line data processing with microcomputer.

      Computerized C- V Plotter to record automatically capacitance-voltage characteristics of junctions in dark and under illumination with capacitance in the range 2 to 2 105 pF.

      Spectral Response set-up for solar cells in the wave-length range of 0.3 to 1.1 mm.

      Laser Scanner to scan and image defect induced spatial variations in the electronic parameters of large area junction devices.

      Deep Level Transient Spectrometer (DLTS), based on lock-in amplifier as well as multiple box car integrator using a microcomputer, for study of trap and impurity levels in junction devices.

 

DEVICES FABRICATED

 

Some of the thin film devices fabricated in the Laboratory are:

 

      Thin film CdS photocells with a photoconducting gain of 106 or better and 100 microsecond response time have been prepared by spray pyrolysis technique.

      Variable bandgap IR detectors, made from Pb1-xHgxS thin films for detection down to 8-l0 mm. These detectors, used at room temperature, have a detectivity of 1010 cmHz 1/2W-l.

      Thin film thermopile, consisting of an array of forty two Ge-Cu alloy thin film thermocouples, which can detect temperature differences of a millidegree Kelvin.

      Ophthalmic glass coatings, consisting of hard, adherent and scratch resistant mixed oxide films for use on sunglasses.

      Interference and reflection filters with bandwidth of 10 Ǻ using gradient index multilayer coatings.

      Dye filters and thin film polarisers using solution grown polymer films.

      Electron microscope grids, micron size apertures, graticules and high resolution test patterns have been fabricated by lithographic techniques.

      Thin film Cu2S/CdS solar cells using sprayed and evaporated CdS films, having efficiencies in the range of 8-10% on' small areas (1 cm2).

      Thin film CdSe photoelectrochemical cells with efficiencies of 4-5 % utilising chemically deposited films.

      SnOx: F/Si SIS type solar cells with sprayed transparent conducting coatings having efficiencies of about 11 % on small areas (1 cm2).

      Selective black nickel, chromium, iron and copper coatings for photothermal conversion of solar energy.

      Zinc oxide varistors, for use in electrical appliances to protect them from voltage surges.

      Thin film strain gauges, made from suitably shaped thin metal films deposited on Kapton foil for measurement of stress.

 

INDUSTRIAL COLLABORA ION

 

The Laboratory maintains an active collaboration with industries in such diverse fields as electronics, optics, vacuum technology and surface analysis and this finds expression in the many consultancy projects.

 

Know-how Transfer

Some of the devices/processes developed in the Laboratory have been given to manufacturing firms for commercial exploitation.

These are:

         Chromium sputtering process for razor blades to Sharpedge Ltd., Delhi.

         6 KW bent beam electron gun-to Vacuum Instruments Co., Delhi.

         Electron microscope grids-to Montech Instruments, Chandigarh.

         Ophthalmic glass coatings-to Laxmi Opticians, New Delhi.

         Thin film CdS photocell to Patel Enterprises,Bangalore.

         Ultra high vacuum systems-to Vacuum Instruments Co., Delhi.

         Optical thickness monitor-to Hind High Vacuum Co., Bangalore.

         RF magnetron sputtering modules-to Indo Burma Petroleum Co., Bombay.

         ZnO varistors-to W.S. Insulators, Madras.

         Selective coatings-to Jyoti Ltd., Baroda.

 

Industrial Consultancy

The following firms have consulted the Laboratory for product improvement/process development/device testing/materials analysis:

      Vacuum Instruments Co., Delhi (Vacuum components, systems and their application to thin film technology and metallurgy).

      Sharpedge Ltd., Delhi (Structure and metallurgy of blades, Improvement of comfort and durability of razor blades by chromium sputtering).

      Harvin Optical Glass Co., Hyderabad (Design and operation of optical instruments).

      Laser Instruments Co., Delhi (Reflecting coating for lasers mirrors).

      Hindustan Machine Tools Ltd., Bangalore (Gratings for numerically controlled machines).

      Central Building Research Institute, Roorkee (Thin film strain gauges).

      Goodyear Ltd., Delhi (Structure of filler powder).

      Jyoti Ltd., Baroda (Emissivity and absorptance of selective coatings).

      Advani-Oerlikon Ltd., Pune (Selective coatings). .

      Bharat Heavy Electricals Ltd., Hyderabad (Selective black surfaces, composition and chemical nature of various constituents present in steel and brass).

      Madhu Chemicals, Delhi (Structure of silica powder, particle size of precipitated silica).

      Montech Instruments, Chandigarh (Electron microscope accessories).

      K.N. Minerals Pvt. Ltd., Ahmedabad (Structure of silica powder).

      National Thermal Power Corporation Ltd., New Delhi (Surface oxide characterization).

      Patel Enterprises, Bangalore (Photocells and its use in electronic devices).

      Continental Devices India Ltd., New Delhi (Metal contact for Electronic Devices).

      Bharat Bijlee Ltd., Thane (Selective Coatings)

      Bharat Electronics Ltd., Bangalore (Spectral response of space quality solar cells).

      R & D Centre, Iron & Steel. Ranchi (Mineral content in ores).

      IIT Kharagpur (SAM/ESCA analysis).

      Cement Research Institute, New Delhi (Structural analysis of specimens).

      Laxmi Opticians, Delhi (Coatings for ophthalmic glasses).

      Police Forensic Science Laboratory, Jaipur (Blood specimen analysis).

      Garware Plastics and Polyester, Bombay (optical measurements on Sun Control polymer films).

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