Volume 8, Issue 3
June 1986, pages 265-438
pp 265-265 June 1986
pp 267-277 June 1986
Microcrystalline silicon films have been found quite useful in amorphous silicon solar cells as a contact material in n-i-p cells. Microcrystalline silicon films are obtained when amorphous silicon films are prepared by R.F. glow discharge of SiH4 + H2 at higher power ratings. These films possess higher conductivity as well as high transmission than amorphous silicon films. The present paper reports the preparation technique ofµc-SiH films using R.F. capacitive glow discharge of hydrogen-diluted silane. X-ray studies andtem studies of the films indicate microcrystallinity of the films. The electrical and optical properties are also reported.
pp 279-284 June 1986
Cd1−xZnxS/CuInSe2 solar cells having efficiencies in the range of 2·3% were fabricated by spray pyrolysis. The best cell had the following parameters:Voc = 305 mV,Jsc = 32 mA/cm2, FF = 0·32 area = 0·4 cm2 and efficiency = 3·149%.Voc versus temperature measurements showed that the electron affinity difference was 0·22 eV. Forward dark current versus voltage curves were plotted and a possible current mechanism occurring in these cells has been proposed.
pp 285-289 June 1986
Heterojunctions of hydrogenated a-Si films prepared by r.f. sputtering with spraypyrolyzed CuInS2 films have been studied. Capacitance-voltage measurements establish the formation of abrupt heterojunction. The barrier height varies from 0·26 to 0·55 V as the resistivity of CuInS2 film decrease from 1·5 × 103 to 65 Θm. These junctions exhibit photovoltaic behaviour withVoc = 220 mV andIsc = 0·20 mA/cm2.
pp 291-296 June 1986
Flash-evaporated technique has been developed for deposition of CuInSe2 thin films. A control over the stoichiometry and chemical composition of the films has been obtained by varying the deposition parameters. Single phase chalcopyrite structure films with optical gap ∼ 1·15 eV have been obtained. The electronic properties of the films have been tailored for solar cell applications.
pp 297-305 June 1986
Doped and undoped polycrystalline silicon films were grown byapcvd and thermal evaporation techniques. The effect of growth and annealing conditions on the crystalline nature of the films and their properties were studied by electrical, optical, x-ray diffraction andsem techniques. Metal silicides such as TiSi2 and PtSi2 were prepared by co-evaporation technique over polysilicon layers to study their suitability in microelectronic applications. Some of the properties of polysilicon and silicides are discussed.
pp 307-313 June 1986
A comparative study of dielectric properties of polysilicon oxide with silicon dioxide, grown on single crystal silicon, shows that the former is more conducting due to the presence of asperites at polysilicon/SiO2 interface. This paper also reports attempts made to improve the electrical properties of polysilicon oxide by investigating the effects of oxidation temperature, polysilicon deposition temperature and doping on current field characteristics of polyoxide. Higher doping and higher oxidation temperature yield smoother interface with higher breakdown voltages and lower leakage currents. Surface morphology of polyoxide under different process conditions is also studied.
pp 315-318 June 1986
Highly transparent and highly conducting films of SnO2:F were prepared by chemical vapour deposition technique. The films prepared at 350°C substrate temperature and 2·5 lit. min−1 flow rate of oxygen showed maximum figure of merit. The optimum doping concentration of fluorine was 1·02 wt%. The Hall experiment showed that the films prepared at optimum conditions had high carrier concentration and high mobility.
pp 319-324 June 1986
Thin films of CuInSe2 have been evaporated onto glass substrates by flash evaporation. The as-deposited films are amorphous and annealing in selenium atmosphere produces polycrystalline films. The films were characterized bytem and x-ray diffraction techniques. The optical absorption of the films shows three energy gaps of 1·03, 1·07 and 1·22 eV. The crystal field and spin-orbit splitting are thus found to be 0·04 eV and 0·16 eV respectively. The percentaged-character of the valence band states is ∼35%. The Arrhenius plot of electrical conductivity of films showed impurity ionization ofEA = 75 meV.
pp 325-331 June 1986
The development of Cs3Sb transmissive interference cathode technology needs processing of such photocathodes on thin dielectric films coated on glass substrates. Here the use of such films as light resonators is made for reducing the light losses due to reflection at the cathode surface. Consequently the sensitivity of the photocathode is enhanced. TiO2 and SiO films are chosen for their good optical properties with Cs3Sb photocathodes in interference photoemission. Deposition methods and instrumentation in assessing their properties are discussed.
pp 333-338 June 1986
Fabrication of thin film patterns involves a sequence of photolithographic and chemical processes to define the high resolution features in thin films on the surface of the optical substrates. The substrates used in the present work were curved fused silica with radii of curvature 58 mm and 18 mm which are used as photocathode substrates for image converter and image intensifier tube devices. The resolution pattern and bar chart were successfully printed on these substrates using a secondary conformable photomask of Mylar.
pp 339-342 June 1986
Development of low loss dielectric high reflecting mirrors for high power laser applications presents some problems in selecting suitable thin film materials and in understanding their optical constants. Some of these problems have been solved by a systematic study of the dependence of optical constants on different evaporation parameters for a number of thin film materials. Using the data thus obtained high reflecting dielectric mirrors for different laser applications in theuv, visible and near-infrared regions were successfully developed indigenously by the method of vacuum evaporation.
pp 343-346 June 1986
A multilayer thin film device called a beam combiner for a specific photodissociation experiment was designed and developed. The device when operated at 45° angle of incidence transmits auv laser beam and reflects a visible laser beam at the same time with minimum energy loss. The efficiency of the device was found to be better than 90%.
pp 347-350 June 1986
A suitable method to determine the optical constants of high index thin films is essential for developing high efficiency dielectric thin film devices in theuv region from 240 nm to 400 nm. A quick and accurate method is established to determine these constants. Using this method the optical losses, refractive index, absorption coefficient and extinction coefficient of ZrO2 films prepared by the method of reactive evaporation were evaluated in theuv region.
pp 351-355 June 1986
Quality and reliability of optical coatings can be evaluated by studying their basic and durability properties. A simple experimental technique is developed which facilitates easy and quick estimation of the quality and reliability of optical coatings as well as optimization of process parameters. This technique has been successfully applied for process optimization of anti-reflection coatings (arcs) for Ge optics in their region.
pp 357-363 June 1986
Transparent and conducting SnO2 films are prepared at 500°C on quartz substrates by chemical vapour deposition technique, involving oxidation of SnCl2. The effect of oxygen gas flow rate on the properties of SnO2 films is reported. Oxygen with a flow rate from 0·8–1·35 lmin−1 was used as both carrier and oxidizing gas. Electrical and optical properties are studied for 150 nm thick films. The films obtained have a resistivity between 1·72 × 10−3 and 4·95 × 10−3 ohm cm and the average transmission in the visible region ranges 86–90%. The performance of these films was checked and the maximum figure of merit value of 2·03 × 10−3 ohm−1 was obtained with the films deposited at the flow rate of 1·16 lmin−1.
pp 365-371 June 1986
Some of the polymers have been recognised as potential materials for application in pyroelectric detectors because of their large and durable electric polarization. These materials are preferred over conventional ceramics due to their unique teatures which make them very sensitive and fast to the infrared radiation detection. The present paper deals with the special characteristics of polymer films, namely PVDF, PVC and PVF, their preparation and characterization and their pyroelectric behaviour.
pp 373-377 June 1986
This paper presents a study of responsivity of InAs0·3Sb0·7 infrared detector. Thin films of InAs0·3Sb0·7 semiconducting compound were prepared by vacuum evaporation on glass and mica substrates held at 473° K under a pressure of 10−6 torr with deposition rate of 20 A°/sec. The isothermal annealing process was employed to improve the quality of the films. The responsivity variation with blackbody temperature (333° K to 673° K), detector temperature (80° K to 303° K) and frequency (10 Hz to 10 kHz) was measured. The experimental set-up and the results are presented and discussed.
pp 379-384 June 1986
Thin films of tungsten carbide have been deposited on stainless steel substrates held at 500°C by r.f. reactive magnetron sputtering in two different modes of introducing argon and acetylene gases called normal and high rate mode. A single phase fcc-WC is formed in the normal mode whereas a mixture of A-15-W3C, hexagonal-WC and graphitic- and diamond-carbon is found in the high rate mode. A microhardness value as high as 3200 kgf/mm2 (as compared to the bulk value of 1800 kgf/mm2) is obtained in the film deposited by normal mode.
pp 385-389 June 1986
Cobalt oxide-iron oxide coatings on stainless steel have been prepared by spray pyrolysis technique. These coatings have absorptance (α) = 0·94 and emittance (ε100) = 0·20 which are much better values than for cobalt oxide or iron oxide alone on stainless steel substrates. The coatings have been found to be stable for temperatures upto 400°C.
pp 391-396 June 1986
lpcvd polycrystalline silicon films were deposited on thermally oxidized silicon as well as onlpcvd silicon nitride deposited on silicon. Acw argon ion laser was used to recrystallize the polysilicon film into large grains (grain size from 5µm to 40µm). Boron was then implanted and standard N-channel silicon gate process and N-channel metal gate process were carried out to realisemosfets on this material. Channel mobilities upto 450 cm2/V-sec for electrons have been measured. This thin filmmosfet has a four-terminal structure with a top and a bottom gate and the influence of one gate on the drain current due to the other gate has been investigated. Comparison of theIDv-VD curves of the devices with physical models was found in good agreement.
pp 397-405 June 1986
The changes in the characteristics of microstrip rejection filter and simple microstriplines due to bulk and thin film dielectric overlay are reported in this paper. Al2O3 overlay both bulk and thin film increases theQ of the filter. All other overlays decrease theQ. TiO2 thin film shows improvement inQ whereas with bulk TiO2 the filtering property is not observed. The effect of overlays on simple lines is to reduce the transmission without much effect in the reflection.
pp 407-413 June 1986
Thermoelectroluminescence studies were performed on zinc phthalocyanine and copper phthalocyanine films deposited on transparent and conducting glass substrate. Theel glow curves were recorded. The trap depths and frequency factors have also been determined using three different methods.
pp 415-418 June 1986
The band gap of semiconductor is determined by photovoltage spectrum. The photovoltage sign shows the semiconductor to be ofn-type conductivity. Mott-Schottky plot gives the position of Fermi level, the approximate position of band edges, donor density in the semiconductor and space charge layer thickness. The results agree with other reported values.
pp 419-422 June 1986
Cadmium sulphide thin films have been deposited onto chromium plated stainless steel substrates under the influence of electric field. The various deposition parameters such as speed of rotation of the substrates, temperature of the chemical bath, molar concentrations of solution and the strength of the electric field were kept at optimized conditions. The electrochemical photovoltaic (ecpv) cells are formed with CdS film electrodes. The properties of CdS films andecpv cells are monitored with selective values of the electric field employed in the controlled precipitation technique. This relatively new technique is described and the possible film formation mechanism suggested.
pp 423-426 June 1986
Thin films of CuBiS2 have been deposited on glass substrates using spray pyrolysis technique. The effect of substrate temperature on the growth of CuBiS2 thin films is studied in the range of 150 to 400°C. The best quality films are grown at substrate temperature 250°C with 0·1 M composition. Other preparative parameters like spray rate, pressure, height of the solution, etc are optimized with respect to substrate temperature. Some optical and electrical properties of CuBiS2 films are also studied and reported.
pp 427-431 June 1986
The solution gas interface technique by which thin films of Bi2−xAsxS3 were deposited is described in this paper. The semiconducting properties of the interface grown Bi2−xAsxS3 thin films are studied. The optical absorption, dark resistivity and thermoelectric power of the films were studied and results are reported.
pp 433-438 June 1986
The structure of electroless thin films of Ni-P has been studied. The microstructure and the selected area diffraction pattern of the samples reveal that certain samples transform to crystalline Ni with P in solid solution by nucleation and growth, whereas others transform to crystalline state by growth alone. The former set of thin films having a P-content of 19–21 at.% is characterized as amorphous. Films with a P-content of 13–15 at.% fall in the latter category and are characterized as microcrystalline. Those with a P-content of 16–18 at.% contain both amorphous and microcrystalline regions.
Volume 42 | Issue 5
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