P K Nair

Bio: P K Nair is an academic researcher. The author has contributed to research in topics: Thin film & Chemical bath deposition. The author has an hindex of 1, co-authored 1 publications receiving 162 citations.

Chemical bath deposition of CuxS thin films and their prospective large area applications

Abstract: CuxS thin films with a wide range of sheet resistances (rSquare Operator ) and optical transmittance (T%), indicating different composition x, have been obtained from chemical baths constituted from copper(II) chloride, triethanolamine and thiourea at appropriate pH (10-12). Depending on the deposition parameters, a range of combination of rSquare Operator approximately=30 Omega to 1 M Omega and T% (500 nm) approximately=1 to 65 and a range of colour of reflected daylight (golden yellow, purple, blue, green, etc.) can be obtained. The films have been found to be stable with respect to electrical and optical properties on storage under ambient. Various possible large area applications such as in architectural glazing, photothermal and photovoltaic conversions are discussed.

Chemical deposition method for metal chalcogenide thin films

Abstract: Metal chalcogenide thin films preparation by chemical methods are currently attracting considerable attention as it is relatively inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors or metals can be used since these are low temperature processes which avoid oxidation and corrosion of substrate. These are slow processes which facilitates better orientation of crystallites with improved grain structure. Depending upon deposition conditions, film growth can take place by ion-by-ion condensation of the materials on the substrates or by adsorption of colloidal particles from the solution on the substrate. Using these methods, thin films of group II–VI, V–VI, III–VI etc. have been deposited. Solar selective coatings, solar control, photoconductors, solid state and photoelectrochemical solar cells, optical imaging, hologram recording, optical mass memories etc. are some of the applications of metal chalcogenide films. In the present review article, we have described in detail, chemical bath deposition method of metal chalcogenide thin films, it is capable of yielding good quality thin films. Their preparative parameters, structural, optical, electrical properties etc. are described. Theoretical background necessary for the chemical deposition of thin films is also discussed.

A general method for the large-scale synthesis of uniform ultrathin metal sulphide nanocrystals

Abstract: Ultrathin metal sulphide nanomaterials exhibit many unique properties, and are thus attractive materials for numerous applications. However, the high-yield, large-scale synthesis of well-defined ultrathin metal sulphide nanostructures by a general and facile wet-chemical method is yet to be realized. Here we report a universal soft colloidal templating strategy for the synthesis of high-quality ultrathin metal sulphide nanocrystals, that is 3.2 nm-thick hexagonal CuS nanosheets, 1.8 nm-diameter hexagonal ZnS nanowires, 1.2 nm-diameter orthorhombic Bi(2)S(3) nanowires and 1.8 nm-diameter orthorhombic Sb(2)S(3) nanowires. As a proof of concept, the ultrathin CuS nanosheets are used to fabricate an electrode for a lithium-ion battery, which exhibits a large capacity and good cycling stability, even after 360 cycles. Furthermore, high-yield, gram-scale production of these ultrathin metal sulphide nanomaterials has been achieved (~100%, without size-sorting process). Our method could be broadly applicable for the high-yield production of novel ultrathin nanostructures with great promise for various applications.

High Symmetric 18-Facet Polyhedron Nanocrystals of Cu7S4 with a Hollow Nanocage

Abstract: On the basis of Kirkendall Effect, high symmetric 18-facet polyhedral nanocrystals of Cu7S4 with a hollow nanocage could be converted from cubic nanocrystals of Cu2O in an aqueous media. The presence of organic additives makes the surface energy of {110} smaller than those of {100} and {111}. The growth of nanocrystals along the normal direction of highest energy surface {100} leads to the formation of a 18-facet polyhedron.

Copper sulphide (CuxS) as an ammonia gas sensor working at room temperature

Abstract: A solution growth technique (SGT) has been used to deposit Cu x S ( x = 1, 1.4, and 2) thin films on glass substrates at room temperature (300 K). These as-deposited thin films are characterized for their structural, optical and electrical properties by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), scanning electron microscopy (SEM) and atomic force microscopy (AFM), optical absorption and current–voltage ( I – V ) measurements. XRD shows that the Cu x S layer grew with hexagonal and monoclinic phases for x = 1 and 2, respectively. SEM and AFM show the nano-particles ( x = 1 and 1.4) and nano-discs ( x = 2) formation. The optical band gaps ( E g ) of thin films are 1.26 eV (CuS), 1.96 eV (Cu 1.4 S), and 2.31 eV (Cu 2 S). In addition, surface wettability is studied by using double-distilled water drops for contact angle measurements. It is observed that the contact angle for Cu 1.4 S is larger than those for CuS and Cu 2 S films. It suggests that the x = 1.4 films have high-surface energy. Ammonia gas sensors are fabricated by using these copper sulphide thin films with silver metal contacts. Based on the time-dependent experimental results nanostructured Cu x S serve as sensor material for the detection of NH 3 molecules at room temperature.

Simplified chemical deposition technique for good quality SnS thin films

Abstract: A chemical deposition technique, much simpler and more versatile than previously reported and capable of yielding good quality SnS films of thickness up to approximately=1.2 mu m under a choice of deposition conditions, is presented. The as-prepared films are polycrystalline with p-type dark conductivity in the range 10-5-10-4 Omega -1 cm-1 for the thicker ( approximately 1 mu m) films and showing a photocurrent to dark current ratio of 5-10 under 500 W m-2 tungsten halogen illumination. The optical transmittance and reflectance spectra and the photocurrent response curves of a series of SnS samples are explicitly presented to provide insight into possible applications of these films.