Ag Doping Level Research Articles

Spray pyrolized Ag–N co-doped p-type ZnO thin films' preparation and study of their structural, surface morphology and opto-electrical properties

This work focused on the fabrication of p-type ZnO material by Ag–N co-doping using spray pyrolysis technique and the characterization of structural, surface morphology and opto-electrical properties. Hall measurements reveal that Ag–N co-doped ZnO thin films are p-type materials and highest mobility is obtained for 2.5mol% of Ag doping, keeping the concentration of N unchanged. The resistivity of the films depends on doping level and shows a minimum value (ρ~1.59Ω-cm) with a carrier concentration of 4.09×1016cm−3 for 2.5mol% of Ag doping at the deposition temperature of 400°C. X-ray diffraction study shows a single phase of ZnO up to 2.5mol% of Ag doping level and after that a phase of silver oxide arises, which confirms that 2.5mol% of Ag doping level is the optimum condition. The aging effect does not affect the p-type characteristics of the Ag–N co-doped ZnO films.

The role of Ag on dynamics of superspins in MnFe2−x Ag x O4 nanoparticles

The effect of dipole–dipole and exchange interactions on dynamics of superspins in a system of MnFe2−x Ag x O4 (where x = 0, 0.1, 0.2, 0.3, and 0.6) nanoparticles has been studied by Ac magnetic susceptibility measurements. Average crystallite size of samples was estimated to be ~7 to ~4 nm, with respect to the doping level of x = 0–0.6. It was found that the nanoparticles are superparamagnetic at room temperature with almost zero coercivity. Saturation magnetization of samples showed a remarkable reduction by increasing non-magnetic Ag doping level. By decreasing the temperature, a transition to frustrated superspin glass state was observed in all samples. Freezing temperatures of superspins were decreased by increasing the Ag content, as a result of decreasing size of crystallites, magnetization of nanoparticles, and consequently weakening of dipole–dipole interactions. The estimated values of zυ, τ 0, and T 0, using critical slowing down model, justify the observed variation of freezing temperatures. Furthermore it was realized that sensitivity of samples to the variation of applied frequency, an important parameter in hyperthermia based therapy, is affected by magnetic interactions between nanoparticles.

Tuning the p-type conductivity of ZnSe nanowiresvia silver doping for rectifying and photovoltaic device applications

Applications of one-dimensional (1D) semiconductor nanostructures in nanoelectronics and nano-optoelectronics rely on the ability to rationally tune their electrical transport properties. Here we report the synthesis of single-crystalline Ag-doped ZnSe nanowires (NWs) by using silver sulfide (Ag2S) as the p-type dopant via a thermal evaporation method. The ZnSe:Ag NWs had the zinc blende structure with [11 ] growth orientation. Significantly, the conductivities of the NWs could be tuned over 9 orders of magnitude by adjusting the Ag doping levels. Field-effect transistors (FETs) constructed from the ZnSe:Ag NWs verified their p-type nature with a hole concentration of up to 2.1 × 1019 cm−3, which is the highest value achieved for p-type ZnSe nanostructures thus far. Schottky barrier diodes (SBDs) based on the ZnSe:Ag NW/ITO junctions exhibited remarkable rectifying behavior, with a rectification ratio of >107 and a small ideality factor of ∼1.29 at 320 K. Moreover, photovoltaic devices were fabricated from the ZnSe NW array/Si p–n heterojunctions by aligning the p-ZnSe NWs in a parallel fashion on a n-Si substrate. The device with a graphene top electrode showed a large fill factor (FF) of 61%, yielding a power conversion efficiency of ∼1.04%. The realization of p-type ZnSe NWs with tunable conductivity opens up opportunities for a host of high-performance nanoelectronic and nano-optoelectronic devices.

Luminescence of oxyfluoride glasses co-doped with Ag nanoclusters and Yb3+ions

Bulk oxyfluoride glasses co-doped with Ag nanoclusters and Yb3+ ions have been prepared by a melt quenching technique. When excited in the absorption band of the Ag nanoclusters between 300 to 500 nm, these glasses emit a broad band characteristic of the Ag nanoclusters between 400 to 750 nm as well as an emission band between 900 to 1100 nm, originating from Yb3+ ions. The intensity ratio of the Yb3+/Ag emission bands increases with the Ag doping level at a fixed concentration of Yb3+, indicating the presence of energy transfer mechanism from the Ag nanoclusters to the Yb3+ ions. Comparison of time-resolved decay kinetics of the luminescence in the respectively Ag nanocluster-Yb3+ co-doped and single Ag nanocluster doped glasses, hints towards an energy transfer from the red and infrared emitting Ag nanoclusters to the Yb3+ ions.

Laser induced thermoelectric voltage effect in La0.67Pb0.33MnO3 thin films doped with Ag

The La0.67Pb0.33MnO3 (LPMO) thin films doped with Ag on vicinal-cut LaAlO3 substrates were prepared using standard pulsed laser deposition technique, in which laser induced thermoelectric voltage (LITV) effect was found. With Ag doping level x (x is defined as,x=massAg/massLPMO) increasing from 0.00 to 0.10, the response time of LITV signals in LPMO thin films firstly decreases (reaching minimum at 0.06), and then increases (still less than that with zero Ag doping). Further, an optimal film thickness was found, at which the peak voltage and response time of LITV signals to reaches maximum and minimum, respectively. The response time of LITV in the LPMO thin films are substantially smaller than that of La0.67Ca0.33MnO3 thin films at the same Ag doping level.

The effect of doping Ag on the microstructure of La2/3Sr1/3MnO3 films

The microstructure of Ag-doped La2/3Sr1/3MnO3 (LSMO) thin films deposited on (001) LaAlO3 single-crystal substrates was systematically investigated in cross section and plan view by high-resolution electron microscopy and analytical electron microscopy. The results showed that the films deposited at 750 °C were perfectly epitaxial with or without Ag-doping. No Ag in the doped film was detected. On the other hand, the LSMO films deposited at 400 °C were less perfect. With increasing Ag-doping level, the shape of LSMO grains became irregular, and the grain size increased gradually. Large polycrystalline clusters consisting of LSMO, AgO, and Ag grains formed in the doped films, and the amount and size of them increased with increasing Ag-doping level. Ag existed at the LSMO grain boundaries in its elemental state. A growth process for the LSMO-Ag system is discussed based on the experimental results. The enhancement of the magnetic spin disorders at the grain boundaries and interfaces caused by doping Ag could result in an improvement of low-field magnetoresistance.

Effect of Ag additions on shock wave degradation of superconductivity in BiPBSrCaCuO and YBaCuO

While it has been successfully demonstrated that Bi-Pb-Sr-Ca-Cu-O and YBa{sub 2}Cu{sub 3}O{sub x} powders as well as mixtures of these powders along with silver and copper can be shock fabricated in metal or alloy matrices, it has been found that their superconducting properties are degraded by the shock wave. In shock fabricating Bi{sub 7}Pb{sub 3}Sr{sub 10}Ca{sub 10}Cu{sub 15}O{sub x}, it has been observed that at peak shock pressures of 4 GPa and above, the as-shocked material behaves as a semiconductor and there is no transition or superconducting onset in the resistance-temperature (R-T) signature. A transition was recently seen for the first time in Bi{sub 7}Pb{sub 3}Sr{sub 10}Ca{sub 10}Cu{sub 15}O{sub x} with plane wave shock loading at 1.5 GPa peak shock pressure. However, even at such a low peak pressure, the R-T signature showed signs of residual degradation: the normal state resistivity was semiconducting and it showed a two phase transition with a T{sub c}(R=O) of about 77 K. The R-T signatures of these degraded samples could, however, be completely recovered on proper heat treatment (typically around 860{degrees}C in flowing air for 90 hours). The results of the effect of the shock wave on Bi{sub 7}Pb{sub 3}Sr{sup 10}Ca{sub 10}Ci{sub 15}O{sub x}more » and YBa{sub 2}Cu{sub 3}O{sub x} at different Ag doping levels is presented in this paper.« less

Optical study of complex formation in Ag-doped CdTe.

The thermal instability of substitutional Ag doping on Cd sites in CdTe is studied with optical spectroscopy. For Ag doping levels above ${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ the ${\mathrm{Ag}}_{\mathrm{Cd}}$ concentration decreases gradually during several months while complex defects are formed, as evidenced by the evolution of low-temperature bound-exciton spectra. In particular, such a bound exciton (BE), ${X}_{2}^{\mathrm{Ag}}$, at 1.5815 eV has been studied in this work, as a typical example of complex Ag-related defects created in the course of release of Ag from Cd sites. A rich phonon spectrum is found to couple to this BE, as expected for a complex defect involving an interstitial species. Dye-laser-excited photoluminescence excitation (PLE) spectra reveal a single lowest BE state, with an orbitally excited (electron) state 8.6 meV higher. An activation energy of 8.8 meV is also found for the thermal quenching of the ${X}_{2}^{\mathrm{Ag}}$ PL emission, interpreted as an 1s-2s rate-limiting excitation of the electron in the BE, in good agreement with PLE data. Zeeman splitting of the 1.5815-eV ${X}_{2}^{\mathrm{Ag}}$ BE line is consistent with the assumption of an electron-hole pair bound to a neutral ``isoelectronic'' defect of a symmetry lower than tetrahedral. Further, the local potential of this defect is predominantly hole attractive, while the electron is loosely bound in a shallow donorlike state. The hole is a ${m}_{z}$=\ifmmode\pm\else\textpm\fi{}(3/2) state, as expected for an average tensional local strain field. A tentative identification is discussed in terms of a ${\mathrm{Ag}}_{\mathrm{Cd}}$-${\mathrm{Ag}}_{\mathrm{i}}$ pair, assumed to be produced by the spontaneous release of ${\mathrm{Ag}}_{\mathrm{Cd}}$ into interstitial (i) sites, with a rather high mobility of the ${\mathrm{Ag}}_{\mathrm{i}}$ interstitial also at room temperature. An alternative defect model, a pair of a Cd vacancy and an ${\mathrm{Ag}}_{\mathrm{i}}$ interstitial, cannot presently be excluded, however. A similar thermal instability of ${\mathrm{Cu}}_{\mathrm{Cd}}$ at a slightly higher doping level is found not to produce strong new BE spectra as for the ${\mathrm{Ag}}_{\mathrm{Cd}}$ case.

Ac conductivity of Ag-doped bulk, glassy As 2S 3

Measurements of the electrical conductivity of Ag-doped bulk As 2S 3 glasses have been made as functions of temperature, pressure, frequency and Ag doping level. A Debye-like loss peak was observed near 10 4 Hz. The frequency of the loss peak is dependent on temperature, pressure and doping level, but these dependences are different from those of the dc conductivity. The ac loss is attributed to the Maxwell-Wagner losses characteristic of inhomogeneous materials. The materials are presumed to be inhomogeneous mixtures of As 2S 3 and Ag 2S. We have also searched unsuccessfully for ac conductance in several bulk chalcogenide glasses.