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.
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.
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.
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:
Ø 6 KW 180° bent beam Electron Gun for deposition of high melting point materials and multi component alloys.
Ø Planetary System for uniform deposition of films.
Ø Optical Thickness Monitor to monitor film thickness during deposition.
Ø DC and RFMagnetron Sputtering Module to deposit multi component alloys of refractory materials and mixtures of oxides, carbide and nitrides.
Ø Intergrating Sphere Reflectometer for measurement of solar absorptance,
Ø Vacuum Calorimeter designed to obtain the solar absorptance, thermal emittance, a/e ratio and stagnation temperatures,
Ø Ellipsoidal Concentrator to measure thermal emittance of a sample under simulated and actual test conditions.
Ø 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.
Ø 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.
Ø Spectral Response set-up for solar cells in the wave-length range of 0.3 to 1.1 mm.
Ø Laser Scanner to scan and image defect induced spatial variations in the electronic parameters of large area junction devices.
Ø 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.
Some of the thin film devices fabricated in the Laboratory are:
Ø Thin film CdS photocells with a photoconducting gain of 106 or better and 100 microsecond response time have been prepared by spray pyrolysis technique.
Ø 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.
Ø 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.
Ø Ophthalmic glass coatings, consisting of hard, adherent and scratch resistant mixed oxide films for use on sunglasses.
Ø Interference and reflection filters with bandwidth of 10 Ǻ using gradient index multilayer coatings.
Ø Dye filters and thin film polarisers using solution grown polymer films.
Ø Electron microscope grids, micron size apertures, graticules and high resolution test patterns have been fabricated by lithographic techniques.
Ø 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).
Ø Thin film CdSe photoelectrochemical cells with efficiencies of 4-5 % utilising chemically deposited films.
Ø SnOx: F/Si SIS type solar cells with sprayed transparent conducting coatings having efficiencies of about 11 % on small areas (1 cm2).
Ø Selective black nickel, chromium, iron and copper coatings for photothermal conversion of solar energy.
Ø Zinc oxide varistors, for use in electrical appliances to protect them from voltage surges.
Ø Thin film strain gauges, made from suitably shaped thin metal films deposited on Kapton foil for measurement of stress.
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.
Some of the devices/processes developed in the Laboratory have been given to manufacturing firms for commercial exploitation.
Chromium sputtering process for razor blades to Sharpedge Ltd.,
6 KW bent beam electron gun-to Vacuum
Electron microscope grids-to Montech
Ophthalmic glass coatings-to Laxmi
Thin film CdS
photocell to Patel Enterprises,
Ultra high vacuum systems-to Vacuum Instruments
Optical thickness monitor-to Hind High Vacuum
RF magnetron sputtering modules-to Indo Burma
ZnO varistors-to W.S. Insulators,
Selective coatings-to Jyoti
The following firms have consulted the Laboratory for product improvement/process development/device testing/materials analysis:
Vacuum Instruments Co.,
Ø Sharpedge Ltd., Delhi (Structure and metallurgy of blades, Improvement of comfort and durability of razor blades by chromium sputtering).
Harvin Optical Glass
Laser Instruments Co.,
Hindustan Machine Tools Ltd.,
Ø Central Building Research Institute, Roorkee (Thin film strain gauges).
Ø Advani-Oerlikon Ltd., Pune (Selective coatings). .
Bharat Heavy Electricals Ltd.,
Ø K.N. Minerals Pvt. Ltd., Ahmedabad (Structure of silica powder).
National Thermal Power Corporation Ltd.,
Continental Devices India Ltd.,
Ø Bharat Bijlee Ltd., Thane (Selective Coatings)
R & D Centre, Iron & Steel.
Ø IIT Kharagpur (SAM/ESCA analysis).
Cement Research Institute,
Ø Police Forensic Science Laboratory, Jaipur (Blood specimen analysis).
Garware Plastics and