CdSxTe1-x films: preparation and properties

TL;DR: In this paper, CdSxTe1-1-x films (0

Abstract: CdSxTe1-x films (0

TL;DR: In this article, the optical band gap of thin film CdSxTe1−x has been reviewed and combined in a meta-analysis to provide a new set of parameters for the bowing equation E g ( x ) = E 0 + (E 1 - E 0 - b ) x + b x 2.

TL;DR: In this paper, a new organometallic "cold-slow" route to strongly fluorescing CdTe/CdS (core−shell) colloids and transparent films is presented.

Abstract: A new organometallic “cold−slow” route to strongly fluorescing CdTe/CdS (core−shell) colloids and transparent films is presented. Based on the optical absorption, fluorescence, FTIR, micro-Raman, XPS, and XRD data collected on these nanostructures before and after thermal annealing, a mechanistic path of the core−shell formation and thermal break up is proposed and discussed. The processing of the CdTe/CdS nanostructures starts with 0.5 M tributylphosphine (TBP) stabilized CdS colloid in dichloromethane as a solvent. This yellow colloidal oil composed of 3−4 nm CdS clusters is reacted with liquid Bis(trimethylsilyl)-telluride (TMS2Te) in the presence of excess insoluble CdCl2 salt. During this reaction, a rapid chalcogen atom exchange occurs within a few seconds which produces a new CdTe “core”. The expelled sulfide reacts slowly with the CdCl2 salt to form new CdS clusters after several hours. Furthermore, this “CdS-formation-driven CdCl2 salt dissolution” activates a strong green-yellow fluorescence ind...

TL;DR: In this paper, an annealing time of 10 min was found to produce the most efficient (8.4%) cells and evidence was found for the CdCl2 anneal promoting the formation of a CdSxTe1−x alloy near the interface.

TL;DR: A novel hollow-core photonic crystal fiber platform was used for the first time to observe clear vibrational modes of the CdTe core, CdS( 0.7)Te(0.3) interface, and carboxylate-metal complexes in dilute aqueous Cd Te quantum dot (QD) solutions, demonstrating the presence of crystalline cores, defects, and surface passivation responsible for photoluminescent efficiency and stability.

Abstract: A novel hollow-core photonic crystal fiber platform was used for the first time to observe clear vibrational modes of the CdTe core, CdS(0.7)Te(0.3) interface, and carboxylate-metal complexes in dilute aqueous CdTe quantum dot (QD) solutions. These modes demonstrate the presence of crystalline cores, defects, and surface passivation responsible for photoluminescent efficiency and stability. In addition, 3-mercaptopropionic acid (MPA)-capped QDs show higher crystallinity and stability than those capped with thioglycolic acid (TGA) and 1-thioglycerol (TG). This detailed, nondestructive characterization was carried out using Raman spectroscopy for solutions with QD concentration of 2 mg/mL, which is similar to their concentration during synthesis process. This platform can be extended to the in situ studies of any colloidal nanoparticles and aqueous solutions of relevant biological samples using Raman spectroscopy.

TL;DR: In this article, Boron doses of 1×1012-5×1015/cm2 were implanted at 60 keV into 1-μm-thick polysilicon films and Hall and resistivity measurements were made over a temperature range −50-250 °C.

Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...

TL;DR: In this paper, a new calculation following traditional methods is proposed for deducing optical constants and thickness from the fringe pattern of the transmission spectrum of a thin transparent dielectric film surrounded by nonabsorbing media.

Abstract: A new calculation following traditional methods is proposed for deducing optical constants and thickness from the fringe pattern of the transmission spectrum of a thin transparent dielectric film surrounded by non-absorbing media. The particular interest of this method, apart from its easiness, is that it makes a directly programmable calculation possible; the accuracy is of the same order as for the iteration method.

TL;DR: In this article, the transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain-boundary trapping model, based on the assumption of both a δ-shaped and a uniform energy distribution of interface states.

Abstract: The transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain‐boundary trapping model. The theory has been developed on the assumption of both a δ‐shaped and a uniform energy distribution of interface states. A comparison with experiments indicates that the interface states are nearly monovalent and peaked at midgap. Their density is 3.8×1012 cm−2, in accordance with carrier‐lifetime measurements performed on CVD films.

TL;DR: In this paper, the optical absorption coefficient for direct, excitonic transitions in a uniform applied electric field is calculated and the electron-hole scattering is treated within the effective mass approximation and leads to an absorption coefficient which differs markedly in size and shape from the Franz-Keldysh absorption spectrum.

Abstract: Numerical calculations of the optical-absorption coefficient for direct, excitonic transitions in a uniform applied electric field are presented. The electron-hole scattering is treated within the effective-mass approximation and leads to an absorption coefficient which differs markedly in size and shape from the Franz-Keldysh absorption spectrum. A detailed numerical study of the shape of the absorption-edge spectrum at photon energies somewhat below the zero-field absorption threshold suggests that for small field strengths the dominant asymptotic form of the absorption coefficient is $\mathrm{exp}(\ensuremath{-}\frac{{C}_{0}|E\ensuremath{-}{{E}_{0}}^{\ensuremath{'}}|}{f})$, where $f=\frac{|e|\mathrm{Fa}}{R}$ is the electric field strength in units of exciton Rydbergs per electron-exciton Bohr radius. This result contradicts the existing belief that the electron-hole interaction does not alter the asymptotic form of the Franz-Keldysh shape: $\mathrm{exp}(\ensuremath{-}\frac{{{C}_{0}}^{\ensuremath{'}}{|E\ensuremath{-}{{E}_{0}}^{\ensuremath{'}}|}^{\frac{3}{2}}}{f})$. Physical arguments are presented to show why the exciton effects should be important. A discussion is presented of the interrelationships among the present treatment of electro-absorption and various one-electron, exciton, and many-body formalisms.

TL;DR: In this paper, a new formulation and method are presented for evaluating bandgap, optical transitions and optical constants from the reflectance data for films deposited onto a non-absorbing substrate, which can be used to evaluate the optical properties of the films.