Author
A.B. Maity
Other affiliations: Haldia Institute of Technology
Bio: A.B. Maity is an academic researcher from Indian Association for the Cultivation of Science. The author has contributed to research in topics: Grain boundary & Thin film. The author has an hindex of 11, co-authored 18 publications receiving 256 citations. Previous affiliations of A.B. Maity include Haldia Institute of Technology.
Topics: Grain boundary, Thin film, Sputter deposition, Crystallite, Grain size
Papers
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TL;DR: In this article, a bowing effect was observed in Zn x Cd 1−x Se films, with an effective mass of the carriers varied with x and indicated that the carriers were highly resistive and polycrystalline.
Abstract: Zn x Cd 1−x Se films (0 E g ) in the Zn x Cd 1−x Se films showed a bowing effect, with a bowing parameter of about 1.26. Microstructural information was obtained from X-ray diffraction and transmission electron microscopy (TEM) measurements, which indicated a predominant wurtzite structure for x x > 0.7. The grain size, determined from scanning electron microscopy and TEM, was observed to decrease with increasing zinc content in the films. The films were highly resistive and polycrystalline in nature, with partially depleted grains. An optical method, developed on the basis of the model of Dow and Redfield. was used to determine the barrier height and the density of trap states at the grain boundary region, along with the carrier concentration of the polycrystalline films. The variation of the electric field within the grains also was studied. The effective mass of the carriers varied with x and indicated a bowing effect.
42 citations
TL;DR: The shift of the band gap to higher energies depended on the relative magnitudes of substrate temperature and gas pressure during deposition as mentioned in this paper, and the relative magnitude of temperature and pressure during the sputtering of a ZnTe target was determined.
Abstract: ZnTe films in nanostructured form have been deposited by high pressure d.c. magnetron sputtering of a ZnTe target onto different substrates kept at various temperatures ranging from 223–373 K. Shift of the band gap to higher energies depended on the relative magnitudes of substrate temperature and gas pressure during deposition.
24 citations
TL;DR: In this paper, the authors obtained explicit expressions for the absorption coefficient beyond the absorption edge by considering the Franz-Keldysh effect and mechanical stress to be operative simultaneously in the grain boundary regions of polycrystalline semiconductor films.
Abstract: Explicit expressions for the absorption coefficient beyond the absorption edge are obtained by considering the Franz-Keldysh effect and mechanical stress to be operative simultaneously in the grain boundary regions of polycrystalline semiconductor films. The expressions are successfully utilized to explain the tail end of the absorption spectrum of ZnTe films.
24 citations
TL;DR: In this paper, 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.
Abstract: 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.
20 citations
TL;DR: In this paper, CdTe films were deposited at different substrate temperatures (423-573 K) using the hot wall evaporation technique using the polycrystalline in nature with varying grain size (0.06-0.18 μm).
Abstract: 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.
20 citations
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TL;DR: The theoretical concepts, experimental tools, and applications of surface photovoltage (SPV) techniques are reviewed in detail in detail as discussed by the authors, where the theoretical discussion is divided into two sections: electrical properties of semiconductor surfaces and the second discusses SPV phenomena.
Abstract: The theoretical concepts, experimental tools, and applications of surface photovoltage (SPV) techniques are reviewed in detail. The theoretical discussion is divided into two sections. The first reviews the electrical properties of semiconductor surfaces and the second discusses SPV phenomena. Next, the most common tools for SPV measurements and their relative advantages and disadvantages are reviewed. These include the Kelvin probe and the use of MIS structures, as well as other less used techniques. Recent novel high-spatial-resolution SPV measurement techniques are also presented. Applications include surface photovoltage spectroscopy (SPS) which is a very effective tool for gap state spectroscopy. An in-depth review of quantitative analyses, which permit the extraction of various important surface and bulk parameters, follows. These analyses include: carrier diffusion length; surface band bending, charge, and dipole; surface and bulk recombination rates; surface state distribution and properties; distinction between surface and bulk states; spectroscopy of thin films, heterostructures and quantum structures; and construction of band diagrams. Finally, concluding remarks are given.
1,499 citations
TL;DR: In this paper, the synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described, which is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1.
Abstract: ▪ Abstract The synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described. The nanocrystallinity is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1. Extensive characterization studies led to the conclusion that phase-pure diamond is produced with a microstructure consisting of randomly oriented 3–15-nm crystallites. By adjusting the noble gas/hydrogen ratio in the gas mixture, a continuous transition from micro- to nanocrystallinity is achieved. Up to 10% of the total carbon in the nanocrystalline films is located at 2 to 4 atom-wide grain boundaries. Because the grain boundary carbon is π-bonded, the mechanical, electrical, and optical properties of nanocrystalline diamond are profoundly altered. Nanocrystalline diamond films are unique new materials with applications in fields as diverse as tribolo...
858 citations
Journal Article•
TL;DR: In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and the phonon broadening of these lines is considered.
Abstract: We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.
788 citations
TL;DR: In this article, ZnSe nanoparticles of about 3 nm in size have been prepared by the sonochemical irradiation of an aqueous solution of selenourea and zinc acetate under argon.
Abstract: ZnSe nanoparticles of about 3 nm in size have been prepared by the sonochemical irradiation of an aqueous solution of selenourea and zinc acetate under argon. The ZnSe nanoparticles were characterized using techniques such as transmission electron microscopy, X-ray diffraction, absorption spectroscopy, differential scanning calorimetry, transmission and diffuse reflection spectroscopy, photoluminescence spectroscopy, and energy-dispersive X-ray analysis. The mechanism of the sonochemical irradiation is discussed. This sonochemical method was found to be a general method for the preparation of other selenides as well.
194 citations
TL;DR: In this article, the preparation conditions of undoped and aluminum-doped zinc oxide (ZnO, ZnO/Al) films by a screen printing technique were investigated.
Abstract: This paper describes the preparation conditions of undoped and aluminum-doped zinc oxide (ZnO, ZnO/Al) films by a screen printing technique. The structural, morphological and electrical properties of the deposited films were investigated. X-Ray diffraction pattern analysis shows that screen printed undoped and aluminum-doped zinc oxide are polycrystalline. Scanning electron microscopy (SEM) of ZnO shows that the obtained ZnO films are granular and porous. The roughness (σ) of the films was found to be in the range 1000–2000 A, depending on fabrication parameters. The electrical behavior of ZnO films under different storage conditions was studied. We show qualitatively that the resistance of ZnO films depends on oxygen and water vapor pressures. We have measured the variation of the electrical resistance at the 300–830 K temperature range, and three activation energies corresponding to donor levels were determined.
132 citations