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A. K. Barua

Bio: A. K. Barua is an academic researcher from Indian Association for the Cultivation of Science. The author has contributed to research in topics: Thin film & Amorphous silicon. The author has an hindex of 10, co-authored 37 publications receiving 317 citations.

Papers
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Journal ArticleDOI
TL;DR: Using very high Ar-dilution to the SiH4 plasma, good quality amorphous Si:H films could be obtained at very low rf power as mentioned in this paper, and the growth of a columnar network structure was demonstrated.
Abstract: Using very high Ar-dilution to the SiH4 plasma, good quality amorphous Si:H films could be obtained at very low rf power. The a-Si:H film, prepared at a very low deposition rate of ∼10 A/min, exhibited a σPh∼1×10−4 S cm−1, σPh/σD∼105, a notably wide optical gap of 2.10 eV and a very good stability against thermal annealing effects with reasonable light induced degradation. At higher rf power undoped μc-Si:H films were prepared with a high σD∼1×10−4 S cm−1, at a deposition rate of 30 A/min from <1 sccm of SiH4. Micrograins were identified with several well-defined crystallographic orientations. However, porosity in the grain boundary zone contributed a significant amount of adsorbed effects on the electrical properties. At very high powers, the growth of a columnar network structure was demonstrated. Long-range structural relaxation permitted by the non-rigid and heterogeneous network structure associated with the physical vapor deposition-like growth at the microcrystalline-transition state, has been identified as the origin of nucleation to the Si network and microcrystallization at higher power. It is proposed that Ar* in the Ar-diluted plasma provides the energy required for nucleation and grain growth during microcrystallization, and plays an analogous role as atomic H does during chemical annealing in H2-diluted plasma.Using very high Ar-dilution to the SiH4 plasma, good quality amorphous Si:H films could be obtained at very low rf power. The a-Si:H film, prepared at a very low deposition rate of ∼10 A/min, exhibited a σPh∼1×10−4 S cm−1, σPh/σD∼105, a notably wide optical gap of 2.10 eV and a very good stability against thermal annealing effects with reasonable light induced degradation. At higher rf power undoped μc-Si:H films were prepared with a high σD∼1×10−4 S cm−1, at a deposition rate of 30 A/min from <1 sccm of SiH4. Micrograins were identified with several well-defined crystallographic orientations. However, porosity in the grain boundary zone contributed a significant amount of adsorbed effects on the electrical properties. At very high powers, the growth of a columnar network structure was demonstrated. Long-range structural relaxation permitted by the non-rigid and heterogeneous network structure associated with the physical vapor deposition-like growth at the microcrystalline-transition state, has been iden...

45 citations

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TL;DR: In this paper, hydrogen was added to the Ar-diluted SiH4 plasma to obtain a homogeneous and improved network structure without having any effect of adsorption.
Abstract: Hydrogenated microcrystalline silicon thin films have been prepared by the rf glow discharge method using argon as a diluent of SiH4 to achieve a high growth rate. μc-Si:H film having conductivity ∼10−5 S cm−1 was achieved at a deposition rate of 36 A/min at a moderate power density of 90 mW/cm2, without hydrogen dilution. Micrograins were identified with several well defined crystallographic orientations. Inhomogeneity and porosity at the grain boundary zone have a significant effect on the electrical properties of the films due to adsorption when exposed to atmosphere. However, by adding hydrogen to the Ar-diluted SiH4 plasma, a homogeneous and improved network structure without having any effect of adsorption was obtained at a reduced deposition rate. Highly conducting (σD∼10−3 S cm−1) undoped μc-Si:H film was prepared at a deposition rate of 15 A/min having 90% crystalline volume fraction. The energy released by the de-excitation of Ar* in the plasma initiates rapid nucleation in the Si network and at...

39 citations

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TL;DR: Polycrystalline silicon carbide thin films have been deposited on amorphous substrates by radio-frequency plasma assisted decomposition of tetrafluoro silane, tetrafluoro methane, and hydrogen gas mixtures using low power density and deposition temperatures as discussed by the authors.
Abstract: Polycrystalline silicon carbide thin films have been deposited on amorphous substrates by radio‐frequency plasma‐assisted decomposition of tetrafluoro silane, tetrafluoro methane, and hydrogen gas mixtures using low‐power density and deposition temperatures. The material is shown to possess the α‐SiC structure using transmission electron microscopy. It has highly visible transmittance and exhibits bands due to silicon carbide as well as fluorine bonded to carbon and silicon in the infrared transmission spectra. It is easily doped, both types showing high conductivity (∼10 S/cm) and Hall mobility [∼10 cm2/(V s)] for either carrier type. The conductivity is seen to be independent of thickness down to ∼10 nm when deposited on glass. This behavior and the dependence of both structural and electronic properties on deposition parameters is discussed in terms of the chemical reactions in gas phase and on the growth surface.

28 citations

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TL;DR: In this article, a phase is obtained which shows significant broadening of the photoluminescence spectrum indicating the quantum wire size distribution, and infrared vibrational studies indicate that this enhancement is due to the H-passivation of defects in the Si-pore interface, though the presence of hydrogenterminated silicon clusters cannot be ignored.

20 citations

Journal Article
TL;DR: In this article, thermal diffusivity (α) has been correlated with electrical and structural properties of hydrogenated microcrystalline silicon (µc-Si:H) films.
Abstract: Thermal diffusivity (α) has been correlated with the electrical and structural properties of hydrogenated microcrystalline silicon (µc-Si:H) films. In the heterogeneous microcrystalline network, α and electrical conductivity (σD) maintain a one-to-one correspondence, and both these parameters are directly related to the crystalline volume fraction (Fc) of the network. For the amorphous silicon network, α is ~ 0.2 cm2s1 and has a very low σD of ~ 10-8 Scm-1. When the crystalline volume fraction (Fc) exceeds a certain percolation threshold, both α and σD increase abruptly. Undoped µc-Si:H films having Fc~94% exhibit a high magnitude of α~0.80 cm2s-1 and a very high σD of ~ 10-3 Scm-1.

17 citations


Cited by
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TL;DR: In this article, the authors consider three types of systems: Carbon Black-Polymer composites, metal-insulator cermets and hydrogenated microcrystalline silicon.
Abstract: Classical percolation theory is concerned with the onset of geometrical connectivity and the accompanied onset of electrical connectivity in disordered systems. It was found, however, that in many systems, such as various composites, the geometrical and electrical onsets of the connectivity are not simultaneous and the correlation between them depends on physical processes such as tunneling. The difference between the above two types of systems and the consequences for the electrical transport properties of the latter composites have been largely ignored in the past. The application of scanning local probe microscopies and some recent theoretical developments have enabled a better understanding of the latter systems and their sometimes "strange" behavior as bona fide percolation systems. In this review we consider the above issues and their manifestation in three types of systems: Carbon Black–Polymer composites, metal–insulator cermets and hydrogenated microcrystalline silicon.

203 citations

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TL;DR: In this article, the influence of the N2O/SiH4 flow ratio and the thickness of the films on the optical and structural properties of the material was analyzed, and the results demonstrate that in silicon dioxide-like material, the nitrogen concentration can be adequately controlled (within the range 0−15 at%) with total hydrogen incorporation below 5 at.

149 citations

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TL;DR: In this paper, the surface defects of ZnO nanoparticles have been characterized by electron paramagnetic resonance (EPR), Raman and PL spectroscopy to reveal the origin of bulk and surface defects within the nanostructures.

103 citations

Journal ArticleDOI
TL;DR: In this article, the effect of post-deposition heat treatment on the electrical and optical properties of ITO films is investigated and several material parameters, such as the effective band gap and the refractive index, have been derived and discussed.

95 citations

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TL;DR: In this paper, the structural, thermal and magnetic properties of synthesized powder particles have been studied as a function of calcination temperature, and the presence of functional group was identified by Fourier transform infrared (FTIR) spectroscopic studies.

76 citations