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Mn2+-doped ZnS nanoparticles embedded in a silica matrix were prepared by the sol–gel technique. Zinc sulfide nanoparticles were found to be well dispersed as single entities in the silica matrix. An electron spin resonance study indicated magnetically dilute discrete Mn2+ levels rather than Mn clusters, even at higher doping concentration (5 mol.%), probably due to the presence of the SiO2 matrix. Photoluminescence spectra showed characteristic yellow–orange luminescence due to the 4T1→6A1 transition of Mn. The emission energy was blue-shifted for higher doping concentrations.

Cd1?xZnxS nanoparticles with different compositions (0?x?1) embedded in silica matrix were prepared in thin film form by the sol?gel technique. The film texture and structural transformation with increasing x value were studied from transmission electron micrographs and electron diffraction patterns. Optical study indicated increase in optical bandgap and decrease in refractive index with increasing zinc content (x value). Photoluminescence studies showed emission from surface states with emission energy blue shifted with increasing zinc content in the films. Annealing behaviour of the films with increasing annealing temperature and time was studied.

SiO 2 /CdTe/SiO 2 composite films in the nanocrystalline form were deposited using a multi-target magnetron sputtering system onto fused silica substrates at a system pressure ∼15 Pa. Different sets of nanocomposite films with different ratios of the sizes of the nanocrystallites ( d ) and intercrystallite distances ( s ) were deposited by changing the relative time of sputtering during sequential sputtering of the targets. The films were characterized by measuring optical, electrical and microstructural properties. Variation of electrical conductivity with temperature indicated Efros hopping within the Coulomb gap to be the predominant carrier transport process in these composite films. A crossover from ‘soft’ to ‘hard’ Coulomb gap was observed with lowering of film temperature. Photoluminescence measurements were carried out in the temperature range 80–300 K. The experimental results were compared with those calculated from the empirical relations regarding the temperature dependence of band-edge energy.

Boron nitride films were deposited at different substrate temperatures (623–773 K) on Si and quartz (fused silica) substrates by RF plasma chemical vapour deposition technique using borane–ammonia and nitrogen as the precursor gases. FTIR studies indicated the films to contain mixed phases of c-BN and h-BN and the percentage of c-BN (35–53%) was dependent on the deposition environment. The optimum deposition condition for obtaining higher c-BN phase was ascertained. The surface textures of the films were observed by scanning electron microscope and atomic force microscope. The optical properties of the films were studied to determine the optical constants (refractive index and bandgap).

Optical and microstructural properties of polycrystalline CuGaTe2 films deposited by three source co-evaporation technique are presented. Two characteristic bandgaps were detected at 1.24 and 1.69 eV corresponding to allowed direct transition and forbidden direct transition respectively. Microstructure was studied by x-ray diffraction (XRD) and SEM/TEM. Harris texture analysis of the XRD data indicated (112) to be the predominant orientation for stoichiometric composition of CuGaTe2 films with Cu/Ga~1.0 whereas (204) orientation was most predominant for the off-stoichiometric films having excess Cu or excess Ga. Variation of Urbach tail width with Cu/Ga ratio was studied. The films had a rough surface, and the surface roughness of the films obtained from diffused reflectance measurement indicated a variation within 32-58 nm.

Synthesis and characterization of undoped and Mn2+ doped ZnS nanocrystallites (radius 2–3 nm) embedded in a partially densified silica gel matrix are presented. Optical transmittance, photoluminescence (PL), ellipsometric and electron spin resonance measurements revealed manifestation of quantum size effect. PL spectra recorded at room temperature revealed broad blue emission signal centred at ∼ 420 nm and Mn2+ related yellow-orange band centred at ∼ 590 nm while ESR indicated that Mn in ZnS was present as dispersed impurity rather than Mn cluster.

Well-crystallized and large-grained magnesium oxide films were deposited onto soda lime glass substrates by sol–gel technique. The films could be synthesized at a relatively low annealing temperature (∼500 °C). The films were dense and characterized by strong reflections from (200) plane for periclase phase and from (400) plane for the β-phase.

Wurtzite GaN films were synthesised on p-Si(1 0 0) and n-Si(1 0 0) substrates by plasma assisted hot wall vapour deposition technique without using any buffer layer. The films were characterised by electrical and optical measurements while the microstructural information was obtained from atomic force microscopy (AFM) and X-ray diffraction (XRD) studies. The compositional study for the GaN film was carried out using SIMS. Photoluminescence (PL) measurement at room temperature exhibited near band edge (BE) emission at ∼363 nm (3.4 eV) along with a broad yellow band. The bonding environment in the film was revealed from FTIR studies. Schottky diode (Au/GaN), fabricated with hexagonal GaN film on n-Si substrate, was characterised by I–V and C–V analysis.

CuIn1−xGaxSe2 (CIGS) (0.05≤x≤0.2) films were synthesized by co-evaporation of elemental materials onto sodalime glass substrates. Electrical and optical properties of the films were studied in the temperature range of 170–380 K. The effect of grain boundary scattering on the electrical transport were examined which indicated grain boundary scattering to play an important role in describing the electron transport processes in these films at lower temperature range. Band gap, refractive index and surface roughness were determined from the analysis of the optical traces (transmittance and reflectance as a function of wavelength) recorded by a spectrophotometer. These results were correlated with the microstructural analysis by SEM and XRD. Photoluminescence (PL) studies were carried out (at 80 and 300 K) for films with different Ga content. The PL spectra were dominated by a strong emission within 1.02–1.19 eV followed by emissions at ∼0.96 and 0.87 eV.

Gallium nitride (GaN) films were deposited by reactive hot wall evaporation technique onto fused silica (quartz) substrates at different substrate temperatures (573–773 K). The films were characterized by measuring microstructural, optical and electrical properties. The GaN films were predominantly hexagonal. The band gap (∼3.4 eV) refractive index (1.42–2.52) and surface roughness (10–46 nm) could be evaluated from the optical absorption spectra. The variation of AC conductivity σ ( ω ) with frequency ( ω ) at different temperatures (134–300 K) indicated a dependence σ ( ω )= Aω s with s varying within 0.85–0.97 having a weak temperature dependence. Elliot's model was utilized to interpret the conductivity data of GaN, which indicated the density of localized states to be ∼4.5×10 18 cm −3 .

CuInTe 2 films were synthesized by graphite box annealing of In/Cu/Te stacked elemental layers (SEL) deposited by evaporation onto glass substrates. The films were polycrystalline with preferential orientation in the (1 1 2) direction. Lattice constants ( a =0.62 nm, c =1.24 nm) were determined from the X-ray diffraction analysis. The optical band gap, determined from transmittance spectra, varied within 0.91–0.95 eV with variation of Cu/In ratio within 0.55–1.97, while the grain size varied between 0.35 and 0.51 μm. The electrical conductivity, Hall mobility and photoluminescence of CuInTe 2 films with different Cu/In and Te/(Cu+In) ratios were studied to ascertain the carrier transport mechanism and nature of defect states in the films.

Raman spectra of CuIn 1− x Ga x Se 2 (0 x ≤0.29) thin films were measured at room temperature and low (∼10 K) temperature to examine the Raman active modes in the films for different x values. The variation of the most intense mode (A 1 mode) with frequency was studied and was compared with the theoretical plot. Although anion is not being substituted in the films (for different x ), its mass was found to influence the Raman shift in the system. Optical band gaps of Cu(In,Ga)Se 2 films were found to vary with x showing a bowing effect.

CuInTe 2 films were synthesized by rapid thermal processing (RTP) of In/Cu/Te stacked elemental layers (SEL). The films were characterized by measuring optical, microstructural, electrical and galvanomagnetic properties. The optical band gap was found to vary within 0.95-0.97 eV with the variation of the Cu/In ratio within 0.72 to 0.92 while the grain size varied between 0.25 and 0.44 μm. Lattice constants were determined from the X-ray diffraction analysis. The films were polycrystalline in nature and oriented preferentially in (112) direction. It was found that grain boundary scattering played a dominant role in describing the electrical and galvanomagnetic properties.

Chemical techniques were employed to synthesize CdS nanoparticles embedded in polymer (PEG 300) and sol-gel silica matrices. Systematic growth of particles (radius 3–9 nm) was obtained by adjusting post-deposition annealing temperature and time to examine the dependence of surface-state–related luminescence on particle size. Photoluminescence (PL) peak energy showed a linear dependence with a gentle slope in the weak confinement region and a steep slope in the strong confinement region, the divergence being observed near the excitonic Bohr radius for CdS. The empirical relation proposed for the weak confinement region could be used for estimating chemically prepared CdS nanoparticle size with a high degree of reliability from PL peak energy.

A simple method for synthesis of well dispersed cadmium sulphide (CdS) nanoparticles embedded in a polyethylene glycol matrix (PEG 300) in thin film form is presented. The molar ratio of PEG and CdS was varied within the range 70 : 30 to as high as 50 : 50. Films with controllable sizes (r ∼ 3 –8 nm) of nanocrystals could be obtained by adjusting post-deposition annealing temperature (T) and time (t). The obtained films showed systematic variation in optical properties with decreasing crystal size due to quantum confinement. Transmission electron micrographs (TEM) indicated well resolved nanoparticles for films annealed at lower temperature (T = 373 K) and time (t < 45 min). Photoluminescence (PL) studies indicated blue shift with decreasing particle size. The films did not degrade with aging in a humid atmosphere (relative humidity 40%) for several weeks.

ZnS0.05Se0.95 nanocrystalline films were deposited onto fused silica and GaAs (100) substrates by the magnetron sputtering technique. The electrical conductivities of the films deposited onto fused silica substrates were measured in the temperature range of 180–300 K. It was observed that the low temperature conductivity could be explained by hopping of the charge carriers in the Coulomb gap while at elevated temperature Mott hopping is the predominant mode of conduction in these films. A distinct cross over from Efros–Shklovoskii to Mott hopping is observed for all the films. Optical spectra were found to be dominated by the combined effects of optical losses due to absorption and scattering. The absorption spectra indicated a blueshift, the extent of which depended on the crystallite size.

CuIn1-xGaxS2 films were synthesized by graphite-box annealing of In/Ga/Cu stacked elemental layers (SEL) in the presence of sulphur vapour. The effects of the ambient gas, annealing temperature and duration of annealing on the microstructure of the films synthesized during annealing were studied. The films were characterized by measuring the microstructure and the optical and electrical properties. The effect of grain boundary scattering on the electron transport process was also studied.

CuIn(S x Se 1− x ) 2 films were synthesized by sulphurization of In/Cu stacked elemental layers deposited onto glass and Mo-coated glass substrates followed by selenization by graphite box annealing. The films, thus synthesized, were characterized by measuring electrical, optical and microstructural properties. The microstructure and hence the physical properties of the films depended critically on the amount of sulphur incorporation. Nature of charge carriers depended on Cu/In, (S+Se)/(Cu+In) and S/(S+Se) ratios while their concentrations varied between 10 16 and 10 19 cm −3 . Grain boundary scattering effects were critically studied by measuring the electrical conductivity ( σ ) and Hall mobility ( μ ) simultaneously on the same sample. Optical transmittance studies indicated the band gap to vary within 0.98–1.40 eV with x values. The photoluminescence spectra, recorded at 80 K were dominated by the excitonic peak located within 1.40–1.16 eV followed by a small peak within ∼0.96–0.98 eV arising due to transition from conduction band to neutral acceptor ( V Cu ) or exciton bound to ionized acceptor (Cu In ) states.

ZnSxSe1-x (0

SiO2/CdSe/SiO2 composite films in nanocrystalline form were deposited on quartz substrates at ∼20 Pa with deposition temperatures ranging from 220 to 240 K using a multi-target magnetron sputtering system. Optical, electrical, and microstructural (TEM and AFM) studies were carried out on the composite films. Studies of the variation of conductivity with temperature indicated Efros hopping within the Coulomb gap to be the predominant carrier transport process in the composite films. Furthermore, a crossover from a ‘soft’ to a ‘hard’ Coulomb gap was noticed with lowering of temperature.

Silicon nanocrystals have been prepared in thin-film form by a dc magnetron sputtering technique. The optical transmission, optical absorption, Raman effect and photoluminescence of the nanocrystals have been studied. The observed blueshift of the band gap due to a reduction in the crystallite size is correlated with the transmission electron microscopy observation. Raman spectra indicated the presence of a TO mode which showed redshift with the decrease in the size of the nanocrystallites.

Studies on the dc electrical conductivity of SiO2/CdSe/SiO2 nanocomposites in the temperature range of 150-370 K are presented. The existence of a threshold volume fraction of the semiconducting phase for the percolation conduction in the composites was observed. The results are in agreement with the predictions of the theoretical models proposed for granular metals. The temperature dependence of the dc conductivity in the higher temperature range (with T-1/2 variation) is in good agreement with the model of Sheng and Klafter.

The surface photovoltage (SPV) measurements of CdS/CdT solar cells, prepared by electrodeposition technique, is presented. Minority carrier diffusion length (L) and lifetime (τ) along with the surface space-charge width (W) in the polycrystalline CdTe absorber layers were estimated. A simple modification of the existing theory of surface photovoltage (SPV) measurements is considered to include the effect of grain boundaries in the polycrystalline material. It was observed that the value of the diffusion length, derived from the Goodman's expression, was much higher (almost double) than the value obtained by considering the effect of barrier height at the grain boundaries of the polycrystalline absorber layer. This indicated that for SPV measurements in polycrystalline material the consideration of the effect of grain boundaries becomes essential. The use of Goodman's simplified expression may not yield unambiguous results.

CuInS2 films were synthesized by sulphurization of In/Cu stacked elemental layers (SEL) deposited onto glass and Mo-coated glass substrates by graphite box annealing at temperatures of 620–880 K. The films thus synthesized were characterized by measuring electrical, optical, microstructural and photoluminescence properties. The microstructure and hence the physical properties of the films depended critically on the amount of sulphur incorporation. Nature of charge carriers depended on both Cu/In and S/(Cu+In) ratio and the carrier concentration varied between 1014 and 1018 cm−3. Grain boundary scattering effects were critically studied by measuring the electrical conductivity and Hall mobility simultaneously on the same sample. The shape of the grains depended critically on the sulphur content. The PL spectra were dominated by the excitonic peak ∼788 nm followed by another peak at ∼892 nm which may be ascribed to the DA transition.

Electrical conductivities of nanocrystalline CdTe films deposited onto quartz substrates by high-pressure (~20 Pa) DC magnetron sputtering were studied as a function of temperature (188–298 K). The grain size varied within 4 to 4.7 nm with the variation of deposition temperature (Ts) within 253 to 273 K. The conductivity (σ) showed (T0/T)p dependence with p~0.5 indicating the presence of a Coulomb gap near the Fermi level. Efros–Shklovskii (ES) hopping was found to be the predominant carrier conduction mechanism in the nanocrystalline CdTe films. The width of the Coulomb gap varied within 27–41 meV depending on the deposition conditions. Cross-over from ES to Mott's hopping was observed. The existing theoretical models were used for estimating hopping energy (29 to 42 meV) and hopping distance (2.8 to 5.1 nm) in the films.

Nanocrystalline ZnS films with different thickness (10–40 nm) were deposited onto quartz and NaCl substrates by magnetron sputtering of a ZnS target in argon plasma. All the films showed a zinc blende structure and the photoluminescence peak positions depended on the surface to volume ratio of the films. The optical absorption in these films could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites.

Amorphous hydrogenated carbon films with different nitrogen content (a-C : H : N) were deposited (thickness 2.65–3.01 μm) by plasma-activated chemical vapour deposition of acetylene+nitrogen (0–62 vol%) onto glass/Si substrates at a deposition temperature of ∼523 K and a negative bias voltage ∼500 V. The fundamental optical absorption edge was studied by optical transmittance measurements. With increasing nitrogen content (0–20 at%) in the films the band gap and Urbach tail width decreased. Thick films deposited without nitrogen had high compressive stress (∼3 GPa). Introduction of nitrogen in the precursor gas was effective in reducing the stress to less than 1 GPa with improved adhesion of the film on the substrate. The stresses in the films were determined by a non-destructive optical technique (from the optical absorption band tail) so that the substrate effect on the stress measurement prevalent in the indentation technique could be eliminated. Raman, photoluminescence and FTIR spectra were analysed to ascertain the quality of the films. Studies on the temperature dependence of the electrical conductivity of the films indicated variable range hopping conduction to be predominant at low temperature.

Amorphous hydrogenated carbon films with different nitrogen contents (a-C : H : N) were deposited by DC plasma chemical vapour deposition of acetylene + nitrogen (0–62, vol.%) onto glass/Si/fused silica substrates. The deposition temperature was ∼523 K at a system pressure of ∼0.2 mbar and negative bias voltage of −500 V. Photoluminescence of the a-C : H : N films were studied with different excitation energies (Eex) below and above the band gap. The optical parameters (absorption coefficient, band gap and refractive index) of a-C : H : N films were determined from the transmittance and ellipsometric measurements. Optical properties of the films could be explained by a two phase model which considers the existence of sp2 clusters (lower band gap region) embedded in a sp3 matrix (higher band gap region). Carrier confinement within the sp2 clusters gives rise to radiative recombination, producing strong photoluminescence (PL) at room temperature. The film quality was ascertained from the FTIR and Raman measurements.

CuIn x Ga 1-x Se 2 films were synthesized by graphite box annealing of In/Ga/Cu/Se stacked elemental layers deposited by thermal evaporation onto sodalime glass substrates. Photoluminescence (PL) studies were carried out in near stoichiometric and copper-rich films with Ga/(In+Ga) ratios varying between 0.24–0.29. The PL spectra were dominated by peaks at ~1.19 eV and 0.87 eV with a shoulder at ~0.84 eV. There was also a peak around 1.3 eV which could be assigned to the absorption from the split-off band. The transitions at ~1.19 eV and 0.87 eV were due to excitonic transition and donor-acceptor pair formation respectively.

Copper indium diselenide films were prepared by graphite box annealing of stacked elemental layer (SEL) precursors. Effects of annealing temperature and ambient atmosphere on the microstructural, optical and electrical properties were studied critically. PL measurements were also carried out to find information on the defect levels. From the above studies, the optimum condition for the deposition of high quality CuInSe 2 films by this technique was determined.

CdTe films with large grains were prepared by rapid thermal processing (RTP) of a room temperature evaporated CdTe film used as the precursor. RTP was carried out at different temperature ramps and the films, thus produced, were characterized by measuring the optical and microstructural properties to optimize the deposition conditions for the preparation of large grained CdTe films. Photoluminescence (PL) measurements were carried out to derive information on the defect structures in these films.

CuInSe2 (CIS) films were prepared by the stacked elemental layer (SEL) technique with subsequent post deposition rapid thermal processing. This technique offered uniform deposition over a considerably large area (∼4 cm2) with perfect control on the individual elemental fluxes. In this method, elemental layers of Cu, In and Se were sequentially deposited on soda-lime glass substrates at room temperature (300 K) in appropriate thickness ratios to ensure the desired composition in the film. The layers were annealed by the rapid thermal process in a temperature range of 373–723 K with an interval of 100 K and at a high ramp rate (∼30 K s−1) using tungsten lamps to ascertain the optimum annealing condition. Structural investigations were carried out by the XRD measurements in order to optimize the annealing parameters (e.g., ramp rate and annealing temperature) for obtaining high quality CIS films free from the deleterious secondary binary phases. It was found that high quality films could be obtained by annealing the stack at 673 K for 3 min in argon atmosphere.

Metallic indium (In) nanotubes were prepared by direct thermal evaporation of an In metal source. In metal was heated in an Ar atmosphere at a high temperature, and after certain period of heating the system was allowed to cool to room temperature in normal atmosphere during which the nanotubes were formed. Growth of the nanotubes was initiated by the catalytic effect of Au, whereas the low melting point of the In metal was found to be responsible for the formation of the hollow core of the nanotubes. The samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, and energy dispersive analysis of X-ray.

Au/diamond/Si Schottky diodes were fabricated with submicron diamond films deposited on Si substrate by chemical vapour deposition of Freon 22 (CHF 2 Cl≤10 vol.%) and hydrogen at a substrate temperature of ∼725 K. The diamond films were ∼0.7 μm thick with a grain size of 500–600 nm. Characterization of the devices by J – V analysis ( J being the current density) showed that an increase in stress (internal or external) makes the forward-biased J – V plot steeper. Films with a low intrinsic stress were used for the fabrication of pressure-sensing devices, which showed a reversible behaviour with an external load (130–900 g) applied perpendicularly to the diode structure. The force sensitivity factors (0.04–0.20 V N −1 ) of the devices (with an area of ∼0.04 cm 2 ) were obtained for different forward-biased current conditions (0.15–0.40 mA cm −1 ). The observed pressure dependence of the electrical properties of the MIS Schottky devices was due to changes in the properties of diamond film under stress.

Nano-diamond films were deposited by chemical vapour deposition (CVD) of camphor (C 10 H 16 O) and hydrogen (∼ 75 vol.%) on glass (at 523–623 K) and quartz/Si substrate (at 523–713 K). The films had low values of surface roughness (∼ 17 nm on quartz) along with high values of hardness and band gap. IR studies of the films deposited on Si substrate indicated the films to be transparent in the IR region. Optical properties of the films deposited on quartz (fused silica) and glass (Corning) substrates were studied. The absorption data in the below band gap region were utilized to estimate the strain (2–12 × 10 −3 ), stress (1.9–8.4 GPa) and hardness (47–62 GPa) in the films. The FTIR studies of the films did not show absorption around 2900 cm −1 , while the Raman spectra indicated a sharp peak (with FWHM ∼8 cm −1 ) at 1337 cm −1 corresponding to good quality diamond films.

Electrical properties of nanostructured ZnSe films deposited onto quartz substrates by high pressure (~20 Pa) d.c. magnetron sputtering technique were studied. The grain size varied within 4 to 4.4 nm with variation of deposition temperature (Ts) from 233 to 273 K. The variation of the electrical conductivity (σ) with temperature was measured in the temperature range of 120–240 K. The conductivity showed ( T 0 T ) p dependence with variation of p within 0.4 to 0.6 indicating the presence of a Coulomb gap (~0.03 eV) near the Fermi level. Efros-Shklovskii hopping (with average p = 0.5) was predominant at low temperature which changed to Mott's hopping with increasing temperature. The existing theoretical models were used to determine the range of hopping energy (0.027 to 0.037 eV) and hopping distance (4.2 to 5.8 nm) in nanocrystalline ZnSe films. Applicability of the percolation model was tested. The effective potential barrier offered by the intergrannular insulating region was found to increase from 0.004 to 0.094 eV with the decrease of grain size from 4.43 to 3.98 nm.

Grain growth in CdTe films was studied by rapid thermal annealing of films prepared by co-deposition (at room temperature) of CdTe and CdCl 2 . Annealing conditions were varied to optimize the post-deposition heat treatment for obtaining CdTe films with larger grains. It was found that it is possible to obtain grains ~ 5 μ m in size in CdTe films by the above techniques. Photoluminescence studies were used to derive information on the film defect structure.

CdTe films were prepared by graphite box annealing of an evaporated CdTe precursor in different ambient conditions in the quartz annealing chamber. Large grain growth was observed for films synthesized at 710 K in argon atmosphere. The films thus produced were characterized by measuring the optical, microstructural and electrical properties.

Nano-diamond films were deposited at room temperature (≈ 300 K) on quartz, Si and Mo substrates by high pressure (≥ 45 mTorr) dc magnetron sputtering of vitreous carbon target in an argon + hydrogen (0–10 vol%) plasma. The nanocrystallites of diamond were embedded in a-C matrix and the ratio of sp3 and sp2 bonds in the film (determined from FTIR) was dependent on the deposition conditions. Formation of nanocrystallites was examined by TEM and SAD patterns. XRD and Raman spectroscopy were also used to probe the microstructural characteristics of the deposited films having average grain size ≈ 55 nm on quartz and ≈ 75 nm on Si and Mo substrates. The films had a surface roughness of ≈ 9 nm on quartz substrates. The sp3 content of the film was high (> 80%) leading to a high band gap (Eg ≈ 4.2 eV) and hardness (Hv≈ 30 GPa). Eg and Hv increased to 5 eV and 50 GPa respectively with the addition of hydrogen (≈10 vol%) in the sputtering environment.

Polycrystalline diamond films were deposited on quartz (fused silica), glass and Si substrates by chemical vapour deposition of Freon 22 (CHF 2 Cl ⪯ 10 vol%) and hydrogen with substrate temperature in the range 525–725 K. Films were sp 3 rich (85–95%) with high band gap ( E g ≈ 3.7–3.95 eV on glass and E g ≈ 4.5–5.5 eV on quartz). The strain and stress in the films were determined from the broadening of the optical absorption edge. The variations of strain and stress on glass with deposition temperature ( T s ≈ 525–725 K) were 5.6–6.0 × 10 −3 and 4.9–5.7 GPa, respectively. With variation of freon content (≤ 10 vol%) in the gas mixture the strain and stress on quartz substrate (for T s ≈ 725 K) varied within 1.6–8.0 × 10 −3 and 1.5–7.8 GPa, respectively. The films were found to be scratch resistant for higher deposition temperature ( T s ≥ 700 K) and lower freon content (≈ 1–2 vol%) in the feed gas. The hardness in the films was observed to decrease from 71 to 63 GPa with increase of freon content from 2–10 vol%.

Flower-like dendritic Cu2S crystals are successfully synthesized from Cu(NO3)2 and thiourea via solvothermal route, using an organic reagent ethylenediamine (en). Growth of dendritic flower and stoichiometry of copper sulphide depended upon reaction time at a constant temperature.

Different morphological patterns of copper sulfide crystals, e.g., flowers, distorted rods (rice, grainlike morphology), and spaghetti-like and spherical microparticles have been successfully synthesized using different organic solvents, namely, ethylenediamine, ethyleneglycol, and ethanol, by a solvothermal process. From the experimental results, it has been revealed that the solvents played an important role to control the morphology and composition of copper sulfide crystals.

CdTe films were deposited at different substrate temperatures (423–573 K) using the hot wall evaporation technique. The films were polycrystalline in nature with varying grain size (0.06-0.18 μm). Dark and photo-conductivities in the films were measured in the temperature range 90–300 K. The conductivity data at low temperatures ( 155 K) was explained by the possible thermionic emission of the carrier over the grain boundary potential barrier. The influence of the modulated grain boundary barrier height (at high temperature) and width (at low temperature) with different illumination levels could explain the overall conductivity of CdTe films.

CuIn 1-x Ga x Se 2 (0 ≤ x ≤ 0.25) films were deposited (on glass substrates at ∼770 K) by four source coevaporation technique. The thickness and average grain size of the films varied within 3-3.5 μm and 0.2-0.5 μm, respectively, with small variation of surface roughness (18-24 nm). The films were characterized by measuring the microstructural, optical and mechanical properties. A new optical technique was used to estimate the strain/stress in the polycrystalline films from the broadening of the optical absorption band tail. Addition of Ga increased the stress from 1.37 x 10 8 to 2.78 x 10 8 dynes/cm 2 while the density of trap states (Q t ) at the grain boundaries varied from 7.2 x 10 9 to 1.3 x 10 11 cm -2 . The corresponding variation in the average built electric field (F av ) at the grain-surfaces of the polycrystalline films was estimated to be 0.15-2.95x10 4 V/cm. Surface photovoltage (SPV) measurements of CuIn 1-x Ga x Se 2 /CdS devices indicated minority carrier diffusion lengths (L n ) to be ∼1 μm and 0.7 μm, respectively, for x=0 and x=0.25.

Polycrystalline CuIn1 − xGaxSe2 (0 ≤ x < 0.3) films (CIGS) were deposited by coevaporating the elements from appropriate sources onto glass substrates (substrate temperature ∼ 720 to 820 K). Photoconductivity of the polycrystalline CIGS films with partially depleted grains were studied in the temperature range 130–285 K at various illumination levels (0–100 mW/cm2). The data at low temperature (T < 170 K) were analyzed by the grain boundary trapping model with monovalent trapping states. The grain boundary barrier height in the dark and under illumination were obtained for different x-values of CuIn1−xGaxSe2 films. Addition of Ga in the polycrystalline films resulted in a significant decrease in the barrier height. Variation of the barrier height with incident intensity indicated a complex recombination mechanism to be effective in the CIGS films.

Amorphous hydrogenated carbon (a-C:H) films were deposited (at room temperature) by plasma CVD of acetylene onto glass substrates with substrate bias (VB) varying within 0 to −400 V. Films deposited at ¦V B ¦≥ 200 V showed significant photoconductivity. The photoconductivity of the films was measured under different illumination level (0–100 mW/cm2). Hopping at the shallow localized states was the predominant mode of electron transport process in these films. Photo-induced conduction process in the amorphous material in the temperature region 80

Diamond like carbon (DLC) films were deposited (thickness ≈ 100–130 nm) by RF plasma CVD of ethylene on to mica and silicon substrates at room temperature. Optical properties of the films deposited at different negative self bias (V B ) voltages (0 to − 805 V) were measured. The refractive index (n) and extinction coefficient (k) of DLC films on mica varied within 1.6–2.1 and 0.035–0.128, respectively while the band gap energy (E g ) decreased from 2.38 to 2.01 eV with increase in V B from 0 to − 805 V. The internal stress (compressive in nature) of these films (on mica) along with that of films deposited by sputtering of vitreous carbon target (on glass) was obtained from the broadening of the optical absorption band tail. The stress on mica (0.2–1.0 GPa) was observed to be comparable to the stress on silicon substrates (0.18–2.1 GPa), measured by the flexure of beam technique. The hardness of DLC films on mica varied within 6.5–8 GPa while that on Si varied within 6–9.5 GPa. The hardness of sputtered films on glass substrate was ≈8.7 GPa.

The electrical resistivity of short carbon fibre filled thermoplastic elastomers based on natural rubber-high density polyethylene (NR-HDPE) blend and styrene-isoprene-styrene (S-I-S) block copolymer has been studied by varying the concentration of fibre from the 0 to 40 phr level. A sharp drop in resistivity is observed in both cases after a critical concentration of fibre is reached, with the S-I-S system showing lower values of critical concentration. At higher concentrations, experimental values of the electrical conductivity agreed reasonably well with the calculated values from a theory based on the probability of formation of a conductive network. The effect of temperature on the resistivity of the composites has also been investigated in a temperature range of 27–120 °C and 27–90 °C for the NR-HDPE system and S-I-S system, respectively. The type of carrier in both the composites is found to be n-type, i.e. electrons, and the activation energy of hopping of the electrons for both the systems has been calculated. A Hall effect study has also been carried out to determine the carrier concentration and drift mobility of both the composites.

Single crystalline indium oxide pyramid and column structures were synthesized by a simple physical evaporation technique. The pyramid structure was obtained without any catalytic action while the column structure was produced using gold as the catalyst. The nanostructures were characterized by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. A blue-green photoluminescence band in the visible region was observed in the In2O3 structures which could be ascribed to the existence of a large amount of singly ionized oxygen vacancies, confirmed by electron paramagnetic resonance.

A comprehensive model has been developed for the determination of the strain, stress and microhardness of polycrystalline thin films from the below-band-gap optical absorption data which reflect the defect states at the grain boundary regions. The model has been applied to describe the absorption data of AlN and diamond films and consequent interpretation of the mechanical properties of the same is presented.