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S. Dhar

Bio: S. Dhar is an academic researcher from University of Calcutta. The author has contributed to research in topics: Band gap & Photoluminescence. The author has an hindex of 15, co-authored 60 publications receiving 589 citations.


Papers
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Journal ArticleDOI
TL;DR: In this article, the electroless nickel plating technique was used for making ohmic or rectifying contacts on porous silicon, and the results showed that the plated metal penetrates the pores and forms contact on an effective area, about 4.5 times the actual area of the sample.
Abstract: We have presented the electroless nickel plating technique as a preferred method for making ohmic or rectifying contacts on porous silicon. Nickel, plated by this technique, penetrates the pores and forms contact on an effective area, about 4.5 times the actual area of the sample. High‐temperature annealing of the plated metal produced excellent ohmic contacts with porous silicon formed on n‐type silicon. The properties of this contact are shown to be much superior to that of conventional evaporated and alloyed ohmic contacts made on p‐type porous silicon of identical characteristics. Contacts made under similar conditions by electroless nickel plating on p‐type porous silicon, on the other hand, showed good rectifying diode characteristics. The observed electrical properties of electroless nickel contacts are believed to be due to the presence of minute amounts of phosphorous with the plated metal.

69 citations

Journal ArticleDOI
TL;DR: The first observation of photoluminescence (PL) from the dilute bismide alloy GaSbBi was reported in this paper, where Epitaxial layers are grown by liquid phase epitaxy technique onto GaSB (1 00) substrates and PL is obtained in the near infrared spectral range (lambda similar to 1.6 mu m).

66 citations

Journal ArticleDOI
TL;DR: In this article, the results of optical absorption and Raman spectroscopy measurements on InSbBi layers grown by liquid phase technique are reported. But the results are limited to the case where the authors only measured the energy band gap reduction up to about 6 ǫ.

31 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the VBAC model to calculate the changes in band structure of Bi-containing alloys such as InP1−xBix, InAsBi, InPBi and GaSbBi due to the incorporation of dilute concentrations of bismuth.

28 citations

Journal ArticleDOI
TL;DR: In this article, the reduction in band gap as well as the increase in spin-orbit splitting energy in GaSb1−xBix and GaP1−XBix are explained by the Valence Band Anticrossing (VBAC) model.

28 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a solution growth technique was used to deposit Cu x S ( x ǫ = 1, 1.4, and 2) thin films on glass substrates at room temperature (300 K) and these as-deposited thin films were 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 currentvoltage (I-V ) measurements.
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.

223 citations

Patent
28 Apr 2006
TL;DR: In this article, the authors describe a system that allows for the detection of actual physical delivery of a pharmaceutical agent to a body using an identifier and an active agent, which finds use in a variety of different applications, including monitoring of therapeutic regimen compliance, tracking the history of pharmaceutical agents, etc.
Abstract: Compositions, systems and methods that allow for the detection of the actual physical delivery of a pharmaceutical agent to a body are provided. Embodiments of the compositions include an identifier and an active agent. The invention finds use in a variety of different applications, including but not limited to, monitoring of therapeutic regimen compliance, tracking the history of pharmaceutical agents, etc.

222 citations

Journal Article
TL;DR: In this paper, a new semiconductor alloy material, GaAs1-xBix, was created by metal organic vapor phase epitaxial (MOVPE) growth, and X-ray diffraction measurements of alloy layers reveal that the diffraction patterns are satisfactory.
Abstract: A new semiconductor alloy material, GaAs1-xBix has been created by Metal Organic Vapor Phase Epitaxial (MOVPE) growth. A low growth temperature, such as 365°C, is required to obtain the alloy. X-ray diffraction measurements of alloy layers reveal that the diffraction patterns are satisfactory. The maximum GaBi content in the GaAsBi alloy estimated from the lattice constant is around 2%, which is consistent with that estimated from secondary ion mass spectroscopy (SIMS) measurements. In a photoluminescence (PL) measurement, a single peak spectrum is observed from 10 to 300 K. The temperature variation of the PL peak energy is as small as 0.1 meV/K.

185 citations

Journal ArticleDOI
TL;DR: In this paper, the authors report on the recent developments and the performance level achieved in the strained-Si/SiGe material system, and propose possible future applications of strained Si and SiGe in high-performance SiGe CMOS technology.
Abstract: The purpose of this review article is to report on the recent developments and the performance level achieved in the strained-Si/SiGe material system. In the first part, the technology of the growth of a high-quality strained-Si layer on a relaxed, linear or step-graded SiGe buffer layer is reviewed. Characterization results of strained-Si films obtained with secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, atomic force microscopy, spectroscopic ellipsometry and Raman spectroscopy are presented. Techniques for the determination of bandgap parameters from electrical characterization of metal-oxide-semiconductor (MOS) structures on strained-Si film are discussed. In the second part, processing issues of strained-Si films in conventional Si technology with low thermal budget are critically reviewed. Thermal and low-temperature microwave plasma oxidation and nitridation of strained-Si layers are discussed. Some recent results on contact metallization of strained-Si using Ti and Pt are presented. In the last part, device applications of strained Si with special emphasis on heterostructure metal oxide semiconductor field effect transistors and modulation-doped field effect transistors are discussed. Design aspects and simulation results of n- and p-MOS devices with a strained-Si channel are presented. Possible future applications of strained-Si/SiGe in high-performance SiGe CMOS technology are indicated.

178 citations