Plasma Assisted Deposition Technique for Synthesis of low Dielectric Constant Polyanisidine Thin Films

Plasma Science, 2002. ICOPS 2002. IEEE Conference Record-Abstracts. The 29th IEEE International Conference on

Photoluminescence studies of spray pyrolytically grown nanostructured tin oxide semiconductor thin films on glass substrates

SnO2 nanocrystalline thin films were deposited on glass substrates by the spray pyrolysis technique in air atmosphere at 375, 400, 425, 450 and 500 ◦C substrate temperatures. The obtained films were characterized by using XRD. The room temperature photoluminescence (PL) spectra of these films have near band edge (NBE) and deep level emission under the excitation of 325 nm radiation. NBE PL peak intensity decreased consistently with temperatures for samples prepared at 400, 450 and 500 ◦C, while a sudden reduction in intensity is observed for the sample prepared at 425 ◦C. A similar effect was observed for the optical transmittance spectra. These effects can be explained on the basis of the change in population of oxygen vacancies as indicated by the change in a values

Synthesis and characterization of 3d-transition metals doped ZnO thin films and nanostructures for possible spintronic applications

The objective of the present study is the formation of single phase Zn1−xTMxO thin films by PLD and increase the solubility limit of TM dopants. The TM doped ZnO nanostructures were also grown by hydrothermal method. The structural and morphological variation of ZnO:TM thin films and nanostructures with TM doping concentration is also investigated. The origin and enhancement of ferromagnetism in single phase Zn1−xTMxO thin films and nanostructures using spectroscopic techniques were also studied. The dependence of ablation parameters on the structural and optical properties of ZnO thin films were studied

Role of chlorine on the opto-electronic properties of β-In2S3 thin films

Effect of chlorine doping on the opto-electronic properties of β-In2S3 thin film, deposited by spray pyrolysis technique is studied for the first time. Chlorine was incorporated in the spray solution, using HCl. Pristine sample prepared using In(NO3)3 and thiourea as the precursors showed very low photosensitivity. But upon adding optimum quantity of chlorine, the photosensitivity increased by 3 orders. X-ray analysis revealed that crystallinity was also increasing up to this optimum level of Cl concentration. It was also observed that samples with high photosensitivity were having higher band gap. The present study proved that doping with chlorine was beneficial as this could result in forming crystalline and photosensitive films of indium sulfide.

Non-destructive evaluation of carrier transport properties in CuInS2 and CuInSe2 thin films using photothermal deflection technique

Photothermal deflection technique (PTD) is a non-destructive tool for measuring the temperature distribution in and around a sample, due to various non-radiative decay processes occurring within the material. This tool was used to measure the carrier transport properties of CuInS2 and CuInSe2 thin films. Films with thickness <1 μm were prepared with different Cu/In ratios to vary the electrical properties. The surface recombination velocity was least for Cu-rich films (5×105 cm/s for CuInS2, 1×103 cm/s for CuInSe2), while stoichiometric films exhibited high mobility (0.6 cm2/V s for CuInS2, 32 cm2/V s for CuInSe2) and high minority carrier lifetime (0.35 μs for CuInS2, 12 μs for CuInSe2

On tuning the orientation of grains of spray pyrolysed ZnO thin films

Effect of varying spray rate on the structure and optoelectronic properties of spray pyrolysed ZnO film is analysed. ZnO films were characterised using different techniques such as X-ray diffraction (XRD), photoluminescence, electrical resistivity measurement, and optical absorption. The XRD analysis proved that, with the increase in spray rate, orientation of the grains changed from (1 0 1) plane to (0 0 2) plane. The films exhibited luminescence in two regions—one was the ‘near band-edge’ (NBE) (∼380 nm) emission and the other one was the ‘blue-green emission’ (∼503 nm). Intensity of the blue-green emission decreased after orientation of grains shifted to (0 0 2) plane. Scanning electron microscope (SEM) analysis of the films asserts that spray rate has major role in improving the crystallographic properties of the films. Moreover resistivity of the films could be lowered to 2.4×10−2 cm without any doping or post-deposition annealing

Spray pyrolysed In2S3 thin films: A potential electron selective layer for large area inverted bulk-heterojunction polymer solar cells

In this paper, we report the results of investigations on the potential of spray pyrolysis technique in depositing electron selective layer over larger area for the fabrication of inverted bulk-heterojunction polymer solar cells. The electron selective layer (In2S3) was deposited using spray pyrolysis technique and the linear heterojunction device thus fabricated exhibited good uniformity in photovoltaic properties throughout the area of the device. An MEH-PPV:PCBM inverted bulk-heterojunction device with In2S3 electron selective layer (active area of 3.25 3.25 cm2) was also fabricated and tested under indoor and outdoor conditions. Fromthe indoor measurements employing a tungsten halogen lamp (50mW/cm2 illumination), an opencircuit voltage of 0.41V and a short-circuit current of 5.6mA were obtained. On the other hand, the outdoor measurements under direct sunlight (74mW/cm2) yielded an open-circuit voltage of 0.46V and a short-circuit current of 9.37mA

Reliable and Damage-Free Estimation of Resistivity of ZnO Thin Films for Photovoltaic Applications Using Photoluminescence Technique

This work projects photoluminescence (PL) as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO) thin films. ZnO thin films, deposited using chemical spray pyrolysis (CSP) by varying the deposition parameters like solvent, spray rate, pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the luminescence properties as well as resistivity. Two emissions could be recorded for all samples—the near band edge emission (NBE) at 380 nm and the deep level emission (DLE) at ∼500 nm which are competing in nature. It is observed that the ratio of intensities of DLE to NBE ( DLE/ NBE) can be reduced by controlling oxygen incorporation in the sample. - measurements indicate that restricting oxygen incorporation reduces resistivity considerably. Variation of DLE/ NBE and resistivity for samples prepared under different deposition conditions is similar in nature. DLE/ NBE was always less than resistivity by an order for all samples.Thus from PL measurements alone, the order of resistivity of the samples can be estimated.

Bias voltagecontrolledphotoluminescencefrom b-In2S3 thin films

b-In2S3 thin filmsweredepositedonIndiumTinOxidesubstratesusingtheChemical SprayPyrolysistechnique.Metalcontactwasdepositedoverthe b-In2S3 thin filmto formahetero-structureofthetypeITO/b-In2S3/Metal.Theintensityoftwophoto- luminescenceemissionsfromthe b-In2S3 thin film,centeredat520and690nmcould be variedbytheapplicationofanexternalbiasvoltagetothishetero-structure.The emissionscouldbeswitchedonoroffdependinguponthemagnitudeoftheexternal appliedbiasvoltage.Thusthepresenceoftwoconductingstatesinthishetero-structure could beidentified.Thetemporalvariationinintensityofthephotoluminescence emissionwiththeapplicationofthebiasvoltagehasalsobeenstudied.Thecondition underwhichphotoluminescencequenchingoccurshasbeenrepresentedbyafirst order differentialequationbetweendiffusionlengthandcarrierconcentration

Growth and Characterization of LiCoO₂ Thin Films for Microbatteries

LiCoO₂thin films have been grown by pulsed laser deposition on stainless steel and SiO₂/Si substrates. The film deposited at 600°C in an oxygen partial pressure of 100mTorr shows an excellent crystallinity, stoichiometry and no impurity phase present. Microstructure and surface morphology of thin films were examined using a scanning electron microscope. The electrochemical properties of the thin films were studied with cyclic voltammetry and galvanostatic charge-discharge techniques in the potential range 3.0-4.2 V. The initial discharge capacity of the LiCoO2 thin films deposited on the stainless steel and SiO₂/Si substrates reached 23 and 27 µAh/cm², respectively.

Electric field alignment in thin films of cylinder-forming diblock copolymer

We investigate thin films of cylinder-forming diblock copolymer confined between electrically charged parallel plates, using self-consistent-field theory ( SCFT) combined with an exact treatment for linear dielectric materials. Our study focuses on the competition between the surface interactions, which tend to orient cylinder domains parallel to the plates, and the electric field, which favors a perpendicular orientation. The effect of the electric field on the relative stability of the competing morphologies is demonstrated with equilibrium phase diagrams, calculated with the aid of a weak-field approximation. As hoped, modest electric fields are shown to have a significant stabilizing effect on perpendicular cylinders, particularly for thicker films. Our improved SCFT-based treatment removes most of the approximations implemented by previous approaches, thereby managing to resolve outstanding qualitative inconsistencies among different approximation schemes.

Ordering in thin films of block copolymers: fundamentals to potential applications

The ordering of block copolymers in thin films is reviewed, starting, from the fundamental principles and extending to recent promising developments as templates for nanolithography which may find important applications in the semiconductor industry. Ordering in supported thin films of symmetric and asymmetric AB diblock and ABA triblock copolymers is discussed, along with that of more complex materials such as ABC triblocks and liquid crystalline block copolymers Techniques to prepare thin films, and to characterise ordering within them, are summarized. Several methods to align Hock copolymer nanostructures, important in several applications are outlined A number of potential applications in nanolithography, production of porous materials, templating. and patterning of organic and inorganic materials are then presented. The influence of crystallization on the morphology of a block copolymer film is briefly discussed, as are structures in grafted block copolymer films. (C) 2009 Elsevier Ltd All rights reserved.

Comparative characterisation by atomic force microscopy and ellipsometry of soft and solid thin films

Ellipsometry and atomic force microscopy (AFM) were used to study the film thickness and the surface roughness of both 'soft' and solid thin films. 'Soft' polymer thin films of polystyrene and poly(styrene-ethylene/butylene-styrene) block copolymer were prepared by spin-coating onto planar silicon wafers. Ellipsometric parameters were fitted by the Cauchy approach using a two-layer model with planar boundaries between the layers. The smooth surfaces of the prepared polymer films were confirmed by AFM. There is good agreement between AFM and ellipsometry in the 80-130 nm thickness range. Semiconductor surfaces (Si) obtained by anisotropic chemical etching were investigated as an example of a randomly rough surface. To define roughness parameters by ellipsometry, the top rough layers were treated as thin films according to the Bruggeman effective medium approximation (BEMA). Surface roughness values measured by AFM and ellipsometry show the same tendency of increasing roughness with increased etching time, although AFM results depend on the used window size. The combined use of both methods appears to offer the most comprehensive route to quantitative surface roughness characterisation of solid films. Copyright (c) 2007 John Wiley & Sons, Ltd.