Papers by Keyword: Chalcogenide

Abstract: A vacuum-assisted thermal evaporation method for the preparation of undoped and Zn-doped erbium sesquiselenide Er₂Se₃ thin films on various substrates using independent elementary sources is developed. The electrophysical parameters, such as electrical resistivity and thermo-electromotive force of the films, are measured from 77 up to 650 K.

Abstract: Recently, matrix such as polymer, graphene and carbon nanotubes (CNTs) for the semiconductor nanoparticles plays a promising role due to their better structural, functional properties and broad range of applications in every field. This chapter reviews the metal chalcogenide semiconductor nanocomposites, their properties and applications. Furthermore, the importance of aforementioned matrix and their role in superior properties of metal chalcogenide nano composites have been discussed.

Abstract: In this study, the synthesis of the ternary semiconductor sensitized silver bismuth telluride (AgBiTe₂: SBT) particles was produced in the solution of AgNO₃, Bi (NO₃)₃×5H₂O and Na₂O₃Te by using a chemical bath deposition (CBD) method and annealing at 200°C for 1 h. According to scanning electron microscopy (SEM), the particle size of SBT after annealing was bigger than before annealing. Based on X-ray diffraction, the SBT after annealing for 1h became more crystalline. In addition, the XRF data also demonstrated that the SBT powder consists of Ag, Bi, and Te as dominant elements. The XRD result confirms a successful growth of the SBT particles with rhombohedral crystal structure. Based on the obtaining results, the SBT particles were successfully synthesized and potentially applied for solar cell application.

Abstract: In this study, a novel strategy for preparation of Cu₂(M^II)(M^IV)S₄ thin films was creatively proposed. Three light absorption materials Cu₂MnSnS₄, Cu₂ZnSnS₄ and Cu₂ZnGeS₄ were successfully synthesized based on combustion method. It was found that the combustion synthesized powder is mainly consist of several metal oxides. The band gap energy of Cu₂MnSnS₄, Cu₂ZnSnS₄ and Cu₂ZnGeS₄ are determined to be 1.3 eV, 1.49 eV and 2.15 eV, respectively, showing a promising application on thin film solar cells. According to our experiment results, the combustion method was confirmed to be an efficient tool to synthesize various Cu-based absorber materials by using a post-sulfurization process, which provides a new view for fabrication of high-efficient low-cost photovoltaics.

Abstract: Germanium–Antimony–Telluride (Ge–Sb–Te) has low electrical resistivity and thermal conductivity for good thermoelectric properties. The Ge–Sb–Te thin films were deposited on Al₂O₃ ceramic substrate by pulsed–dc magnetron sputtering system using a 99.99 % Ge:Sb:Te of 1:1:1 composite target and annealed at 573, 623, 673, and 723 K for 1 hour in vacuum. The phase identification, atomic composition, morphology and film thickness (d), carrier concentration (n), mobility (µ), Seebeck coefficient (S) and electrical resistivity (ρ) of the as–deposited and the annealed samples were investigated by X–ray diffraction (XRD), energy dispersive X–ray spectroscopy (EDX), field–emission scanning electron microscopy (FE–SEM), Hall–effect measurement, steady state method and calculation of from n and µ, respectively. The results demonstrated that the as–deposited Ge–Sb–Te film showed amorphous phase and annealing changed the phase crystalline. Morphologies of annealed Ge–Sb–Te films showed very large grain size and porosity to obtaining good n and µ. The approximately maximum power factor (P) was 4.22×10⁻⁴ W m⁻¹ K⁻² at annealing temperature of 723 K.

Abstract: The keys for development of copper-based chalcogenide crystal thin film solar cells are to improve efficiency and reduce costs. Oriented growth and band gap grading of its absorption layer crystal film are important ways to improve the efficiency. It proposed controllable preparation of this type thin film by chemical solution deposition and co-reduction, and study on the crystal orientation and regulation of the band gap gradient. It will design the composition and band gap gradient of multi-component and multilayer films, and establish the models for design, theoretical calculation and performance prediction; It will explore the effect of band gap gradient on electrical and optical properties and reveal the effecting laws and mechanism on electrical and optical properties.

Abstract: We report here on resistive switching measurements on GaMo₄S₈ a lacunar spinel compound with tetrahedral Mo₄ clusters filled with 11 electrons. Alike other clustered lacunar spinel compounds with 7 or 8 electrons per cluster, this narrow gap Mott Insulator exhibits both a volatile and a non-volatile unipolar resistive switching. We found that the volatile resistive switching appears above a threshold electric field in the 7 kV/cm range. For electric field much larger than this threshold, the resistive switching becomes non-volatile. Successive electric pulses allow switching back and forth between high and low resistance states. All these results demonstrate that the narrow gap Mott insulator compound GaMo₄S₈ could be a relevant candidate for a new type of non-volatile memory based on an electric field induced breakdown of the Mott insulating state.

Abstract: The great interest toward chalcogenide materials is due to the simple technology of preparation in bulk forms and thin films; good thermal and mechanical properties; transparency and photo-sensibility in the IR spectral range. These advantages determine the possibilities for potential application of these materials like optical storage media, memory devices, optical elements (lenses, waveguides, gratings, etc). The idea of present study is to trace the impact of gallium or indium as metal introduction on the behaviors of the glasses from germanium - chalcogenide system.

Abstract: Polymeric ligand (TSCF) have been synthesized via polycondansation of thiosemicarbazide with formaldehyde and its polymer metal complex [TSCF-Cd (II)] has been prepared with Cd (II) ion. Two different batches of CdS chalcogenide, semiconductor nanocrystals have been synthesized by hydrothermal treatment of TSCF-Cd (II)] using a glass Q tube reactor at 200 °C and 250 °C, and marked as (CdS)₁ and (CdS)₂ respectively. The resultant nanocrystals were characterized by a variety of methods for thier physochemcial properties. The TEM micrographs showed well-defined, close to hexagonal particles, and the lattice fringes in the HRTEM images confirmed their crystalline nature. The sizes of (CdS)₁ and (CdS)₂ were 40 and 50 nm respectively but their morphologies were similar. The optical band gap energies (2.52 eV/ 2.48 eV) and photoluminescence peaks (532/534 nm) of the synthesized CdS nanocrystals suggest that they can be promising photocatalysts. The conductivities and the dielectric constants of the CdS nanocrystals were also studied and the activation energy value of (CdS)₁ and (CdS)₂ nanocrystals were found to be 0.64 eV and 0.70 eV.

Abstract: In this work, we investigate the effect of the N-doping on microstructure and electrical properties of chalcogenide Ge₂Sb₂Te₅ (GST) films for application to multilevel-storage phase change memory (PCM). Crystal size can be markedly reduced from 16 nm to 5 nm by N-doping into GST. The crystal growth suppression is believed to be controlled by distributed fine nitride particles. The resistivity of N-GST as a function of annealing temperature exhibits a gradual change due to the crystal growth suppression. The characteristics imply that N-GST is suitable for application to multilevel-storage PCM as the next-generation nonvolatile memory.