Sandwip K. Dey

Inorganic nanoparticles for cancer imaging and therapy.

Inorganic nanoparticles have received increased attention in the recent past as potential diagnostic and therapeutic systems in the field of oncology. Inorganic nanoparticles have demonstrated successes in imaging and treatment of tumors both ex vivo and in vivo, with some promise towards clinical trials. This review primarily discusses progress in applications of inorganic nanoparticles for cancer imaging and treatment, with an emphasis on in vivo studies. Advances in the use of semiconductor fluorescent quantum dots, carbon nanotubes, gold nanoparticles (spheres, shells, rods, cages), iron oxide magnetic nanoparticles and ceramic nanoparticles in tumor targeting, imaging, photothermal therapy and drug delivery applications are discussed. Limitations and toxicity issues associated with inorganic nanoparticles in living organisms are also discussed.

Integrated sol-gel PZT thin-films on Pt, Si, and GaAs for non-volatile memory applications

Abstract Properties of integrated sol-gel PZT thin-films of various Zr/Ti ratios, evaluated as a function of processing parameters, are presented and discussed. The substrate materials for the PZT depositions encompassed Pt, Si, and GaAs. The design, fabrication, and operation of a single PZT element combined with the GaAs JFET planar integrated circuit technology to produce non-volatile programmable random access memories (NVPRAM) are presented.

Processing and parameters of sol-gel PZT thin-films for GaAs memory applications

Polymeric sol-gel processing represents an IC technology compatible route to fabricate defect-free and compositionally adjustable inorganic non-metallic thin-films at relatively low temperatures.The critical physico-chemical issues which affect the reproducible fabrication of PZT thin-films are outlined. The low field behavior and the high field switching and stability characteristics of PZT thin-films were studied for radiation hard and nonvolatile memory applications. Performance data of integrated PZT thin-films on solid Pt and sputtered Pt layer on silicon-nitrided GaAs substrates are presented and discussed. A compositionally adjustable low field permittivity of 1200, a dielectric break-down strength exceeding 100 V/μm, ∼1012 polarization reversal cycles, and tm ∼ 100 ns were observed. Compatibility of non-linear PZT thin-film element processing with GaAs JFET planar VLSI technology is addressed.

Electrical properties of paraelectric (Pb0.72La0.28)TiO3 thin films with high linear dielectric permittivity : Schottky and ohmic contacts

Linear, paraelectric (Pb0.72La0.28)TiO3 or PLT(28) thin films with a bandgap>3 eV were deposited on Pt/Ti/SiO2/Si substrates by the sol-gel technique. Specific top-contact metals from two distinct groups (i.e., non-noble or M T and noble or M N; the former being oxidizable transition metals) were selected to understand the electrical nature of the interfaces in terms of electrode dependent energy band diagrams and equivalent circuit models. Using a high sensitivity high-pass filter circuit to evaluate the charging and discharging behavior coupled with results of the thickness and voltage dependence of capacitance, it was determined that M T ( Ni,Cr,Ti) and M N ( Pt,Au,Ag) metals form Ohmic and Schottky contacts, respectively. Supported by thermochemical data and calculations, the ohmic M T- PLT interfaces are envisioned to be of the form: M T-M T Ox-n+ PLT-n PLT. In contrast, the M N- PLT interfaces may be characterized by a metal work function independent Schottky diode; the surface Fermi level being pinned at the mid-gap. For example, a Schottky barrier height of 1.83 eV and a built-in voltage of 1.3 eV at the Pt-PLT interface were estimated. From low field capacitance measurements, the ratio of interfacial to bulk resistance, R i/R b, was estimated to be 23.

Cubic paraelectric (nonferroelectric) perovskite PLT thin films with high permittivity for ULSI DRAMs and decoupling capacitors

Polycrystalline paraelectric perovskite thin films in the Pb-La-Ti-O or PLT (28 mol.% La) system have been studied. Thin (0.5- mu m) films were integrated onto 3-in Pt/Ti/SiO/sub 2//

Effective work function of Pt, Pd, and Re on atomic layer deposited HfO2

Platinum and Pd show a significant difference in work function on SiO2 and high-K materials (HfO2). The effective metal work functions for Pd, Pt, and Re on atomic layer deposited HfO2, which are different from the vacuum work function and important for device threshold voltage control, are measured by the C-V method. The difference is attributed to the dipoles at the metal/HfO2 interface, which is a result of charge transfer across the interface. Moreover, the extracted charge neutrality level and screening parameter are correlated with the phase development, film stoichiometry, and density of interface states at the metal/high-K interface.

Ruthenium films by digital chemical vapor deposition: Selectivity, nanostructure, and work function

Ruthenium electrodes were selectively deposited on photoresist-patterned HfO2 surface [deposited on a SiOx/Si wafer by atomic layer deposition (ALD)] by a manufacturable, digital chemical vapor deposition (DCVD) technique. DCVD of Ru was carried out at 280–320 °C using an alternate delivery of Bis (2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)Ru (dissolved in tetrahydrofuran) and oxygen. The as-deposited Ru films were polycrystalline, dense, and conducting (resistivity ∼20.6 μΩ cm). However, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and high-resolution electron microscopy results indicate the presence of an amorphous RuOx at the Ru grain boundaries and at the DCVD–Ru/ALD–HfO2 interface. The estimated work function of DCVD–Ru on ALD–HfO2 was ∼5.1 eV. Moreover, the equivalent oxide thickness, hysteresis in capacitance–voltage, and leakage current density at −2 V of the HfO2/SiOx dielectric, after forming gas (95% N2+5% H2) annealing at 450 °C for 30 min, were 1....

Chemical bath deposition of nanocrystalline (111) textured Ag2Se thin films

Abstract An inexpensive chemical bath technique for nanocrystalline Ag2Se thin films deposition on transparent polyester sheets is developed. The deposition process is essentially based on a hydrolytic decomposition of selenosulfate. The deposited films were characterized by X-ray analysis, and also optical and electrical investigations were performed. X-ray analysis of the films confirmed that the deposited material is (111) textured silver selenide, with an average crystal size of 9.2 nm. The sheet resistance of the annealed films is about 10 Ω/square, while for the as-deposited ones, it is about 20 times higher. The optical investigations show that the films exhibit gradually increasing transparency in the 320–820 nm region. Using the optical absorption data, the optical band gap for the deposited thin films was determined to be 1.8 eV. Such somewhat higher value than the previously reported ones is attributed to size quantization effects.

A simple solution growth technique for PbSe thin films

A low temperature (room to 70°C) chemical bath deposition technique for submicron PbSe thin films, suitable for any size and shape of substrate is reported. Uniform, mirror like films were deposited on glass or clear polyester film substrates. X-ray, optical, and electrical investigations were carried out for as-deposited as well as for annealed films.

Experimental study of the copper thiosulfate system with respect to thin-film deposition

Abstract An experimental study of the copper-thiosulfate system in mild acidic (pH ∼ 5) aqueous solutions, with respect to thin-film formation, was undertaken. Thin films of Cu x S (1 ⩽ x ⩽ 2) were deposited by a simple electroless technique on glass or transparent polyester films, at 50 °C. Thin films were deposited from chemical baths in which the ratios of copper to thiosulfate were varied from 1:1 to 1:10. Thin films of different compositions (Cu 2 S, Cu 1.8 S, Cu 1.4 S and CuS) were prepared and then characterized for morphological, optical and electrical properties. The deposited films chemically close to Cu 2 S were found to be amorphous, while the CuS films were a mixture of both amorphous and polycrystalline phases. The optical spectra of the Cu 2 S films exhibited high transmission both in the visible region of the spectrum (beyond 600 nm) and throughout the near-infrared region (800 to 2500 nm), while CuS films were found to be highly absorptive throughout the near-infrared region, with peaked transmission in the visible region at about 560 nm. The sheet resistances of the films, determined by the standard four-probe measurements, were between 100 and 650 Ω/square.